https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&user=108.162.216.49&feedformat=atomexplain xkcd - User contributions [en]2024-03-19T14:04:40ZUser contributionsMediaWiki 1.30.0https://www.explainxkcd.com/wiki/index.php?title=2886:_Fast_Radio_Bursts&diff=3337562886: Fast Radio Bursts2024-01-29T20:35:57Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 2886<br />
| date = January 26, 2024<br />
| title = Fast Radio Bursts<br />
| image = fast_radio_bursts_2x.png<br />
| imagesize = 469x524px<br />
| noexpand = true<br />
| titletext = Dr. Petroff has also shown that the Higgs boson signal was actually sparks from someone microwaving grapes, the EHT black hole photo was a frozen bagel someone left in too long, and the LIGO detection was just someone slamming the microwave door too hard.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Created by an ENERGETIC OVEN-SIZED STAR - Please change this comment when editing this page. Do NOT delete this tag too soon.}}<br />
<br />
[[Cueball]] is giving a presentation, stating the different sources of {{w|fast radio burst}}s, which are short high-energy signals which have been detected by astronomers, but whose source is not known. His team is pretty sure that most of these bursts are energetic stellar objects in space - that is, astronomical phenomena.<br />
<br />
He then says that some of them are caused by {{w|microwave oven}}s, citing Dr. Emily Petroff's work on identifying the apparent source of "{{w|Peryton (astronomy)|peryton}}s" at the {{w|Parkes Observatory}}.<ref>E.Petroff et al. (2015). "[https://academic.oup.com/mnras/article/451/4/3933/1119649?login=false Identifying the source of perytons at the Parkes radio telescope]". ''Monthly Notices of the Royal Astronomical Society'', '''451'''(4):3933–3940.</ref> These are signals similar to fast radio bursts, but which originate on Earth and not in space; initial hypotheses included atmospheric effects related to {{w|lightning}}, and passing aircraft, but they were eventually identified as a much closer range signal from microwaves escaping as the oven door was opened inside the observatory.<br />
<br />
After that, he explores two further options, combining attributes of the previous two:<br />
<br />
* Energetic stellar-sized microwave ovens; this is unlikely since microwaves typically are not stellar-sized and all known microwave ovens originate on Earth rather than in space. (There is [https://global.chinadaily.com.cn/a/202106/30/WS60dbaca4a310efa1bd65ebc9.html apparently a microwave oven] installed in the Chinese Tiangong space-station, but it appears that the ISS [https://www.bbc.co.uk/news/world-51235555 is less well equipped] than that. Neither facility is ever likely to have room for 'stellar-sized' equipment of any kind.)<br />
* An energetic stellar-sized object in the break room, which would be surprising, as we have yet to see a break room large enough to contain a stellar-sized object. Although unlikely, he says he is sending a grad student there to double-check. Presumably the student is being sent rather than Cueball himself both because it is unlikely to give useful data, and because if there is indeed energetic stellar plasma in the break room, the million-degree temperatures would probably kill anyone who enters it, and grad students are disposable when compared to researchers.<br />
<br />
Note that, as well as the ''universe-''sized {{w|Cosmic microwave background}} radiation, there are various microwave-bright {{w|Pulsar}}s and other strong microwave signals [https://www.space.com/40840-nanodiamonds-mysterious-cosmic-microwave-light.html originating from actual stars], but no reason to believe that they are deliberately purposed/engineered as any kind of actual oven, despite [https://science.nasa.gov/missions/hubble/hubble-sees-a-stellar-furnace/ misleading language] sometimes employed by those in the field.<br />
<br />
The title text references a number of other discoveries, with Dr. Petroff suggesting explanations based on microwave ovens for each of them, as was the case with her own discovery:<br />
<br />
* The apparent detection of the {{w|Higgs boson}} at the Large Hadron Collider was actually someone [https://www.youtube.com/watch?v=wCrtk-pyP0I microwaving grapes], which generates plasma<br />
* The [https://science.nasa.gov/resource/first-image-of-a-black-hole/ image of a black hole] captured by the Event Horizon Telescope was actually a burning bagel (a notably ring-shaped bread product)<br />
* {{w|LIGO}} (the Laser Interferometer Gravitational-Wave Observatory) did not detect gravitational waves, but was instead disturbed by someone slamming the microwave door too hard<br />
<br />
In each case, these are highly improbable - for instance, LIGO used a complex suspension system, and two sites (one in Louisiana and one in Washington State) comparing signals, to rule out such interference.<br />
<br />
See [[2289: Scenario 4]] for a similar situation.<br />
<br />
==References==<br />
<references/><br />
<br />
==Transcript==<br />
{{incomplete transcript|Do NOT delete this tag too soon.}}<br />
<br />
:[Cueball standing behind a lectern, with a poster hung from the ceiling behind him]<br />
<br />
:Potential sources of fast radio bursts:<br />
:(1) Energetic stellar-sized astrophysical objects floating in space<br />
:Cueball: We're pretty sure this is what most of them are.<br />
<br />
:(2) Microwave ovens in the observatory break room<br />
:Cueball: This was definitely some of them, oops. (Petroff et. al., 2015)<br />
<br />
:(3) Energetic steller-sized microwave ovens floating in space<br />
:Cueball: We think this one is unlikely.<br />
<br />
:(4) Energetic stellar-sized astrophysical objects in the observatory break room<br />
:Cueball: This is almost certainly not it, though we're sending a grad student to double-check.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Astronomy]]<br />
[[Category:Physics]]<br />
[[Category:Space]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=Talk:2408:_Egg_Strategies&diff=204222Talk:2408: Egg Strategies2021-01-07T15:51:32Z<p>108.162.216.49: </p>
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<div><!--Please sign your posts with ~~~~ and don't delete this text. New comments should be added at the bottom.--><br />
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I'm not going to get into it because it's not related to these egg cartons, but it is ''really weird'' sitting here explaining a joke while I listen to breaking news on the radio. [[User:Captain Video|Captain Video]] ([[User talk:Captain Video|talk]]) 22:24, 6 January 2021 (UTC)<br />
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I really thought it was just me who cared about center of gravity for eggs. [[Special:Contributions/162.158.79.49|162.158.79.49]] 23:43, 6 January 2021 (UTC)<br />
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We keep the hard boiled ones at one end and the fr4esh ones at the other end.<br />
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Bring True Neutral (egg carton sits lengthwise in fridge, most convenient egg is removed until carton is empty), I am ''baffled'' by the existence of other "strategies". Do people really do this? [[Special:Contributions/108.162.241.70|108.162.241.70]] 00:57, 7 January 2021 (UTC)<br />
: True Neutral here, and also putting the carton in the fridge eggless side out (which is consistent with "most convenient egg removed"). The current explanation says that this is "a disaster waiting to happen". Why?<br/>As a side-note, as I understand it, the alternate strategies can be convenient if you ''don't'' put the carton lengthwise in the fridge (particularly if you don't put it in the fridge ''at all''). [[Special:Contributions/162.158.183.117|162.158.183.117]] 11:26, 7 January 2021 (UTC)<br />
:: I am also True Neutral - when putting the carton into the fridge end-first it allows me to extract it with the majority of the weight in my hand. It's a disaster if it is inserted the heavy side in first because when I grab the empty end the weight of the eggs can tip them out the other side. As an aside, I was a little insulted to find out that I am not the only person in the world who actually has an "egg carton strategy". I thought I was unique! ;-) [[User:Rtanenbaum|Rtanenbaum]] ([[User talk:Rtanenbaum|talk]]) 13:40, 7 January 2021 (UTC)<br />
: Chiming in on True Neutral strategy, which I also use, with some added thoughts: I also put the heavy end in first, but primarily because I usually have two cartons stacked, where inserting the heavy end on top of the full carton in the fridge makes it easier to push the carton the rest of the way in on top of the bottom carton. Putting it in the other way around, the heavy end is hanging off the bottom carton, resulting in less stability before it's pushed all the way in. If you can't tell, I'm an engineer! [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 14:41, 7 January 2021 (UTC)<br />
<br />
Being Lawful Good and married to someone who is Chaotic Good, we might sometimes argue over this. [[Special:Contributions/162.158.62.29|162.158.62.29]] 03:23, 7 January 2021 (UTC) MSS<br />
<br />
In Germany, there are two sizes of egg cartons, containing 6 or 10 eggs, respectively. Most refrigerators I’ve seen (in stores or households) contain an egg-holder with six dents, though I also have occasionally seen 10-dent egg holders.<br />
Since I usually buy 20 eggs at the weekly market, my strategy is to transfer the eggs from a package to the egg holder once there are less than 9 left in the package (for the purpose of knowing how many are still left without having to open a package). If there are more than six eggs, the one or two additional eggs are placed lying besides the egg holder.<br />
I think that counts as chaotic neutral. [[Special:Contributions/141.101.68.28|141.101.68.28]] 01:42, 7 January 2021 (UTC)<br />
<br />
I've got a niggling feeling that Chaotic Neutral (at least) is wrongly depicted. Too orderly. I'd have put Chaotic Good's pattern there (not necessarily vice-versa, as the current incumbent looks more Lawful or Variation-of-neutrality as well as Good) as attempting to maintain balance but with an element of chance. We don't know what sequence of removal ''led'' to each of these states, of course. That might make much of the difference in how we reach the illustrated states. [[Special:Contributions/162.158.158.253|162.158.158.253]] 03:03, 7 January 2021 (UTC)<br />
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I'd go a little further and swap CG and CN (the current CG being a marginally more ordered and balanced CN) but otherwise agree. CN is the strategy I use when the carton is at risk of being centrally supported while in humid conditions (don't ask), making NG risk bending of the whole carton. LG is actually worse then NG in some circumstances, due to a drastically reduced moment of inertia contributing to the chance of dropping. On the other hand, NG increases the probability of end-shattering if the carton is actually dropped. Overall, different strategies are probably a result of experience, circumstance, relative clumsiness, and hat colour. [[Special:Contributions/162.158.166.75|162.158.166.75]] 05:43, 7 January 2021 (UTC)<br />
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I feel like the chaotic good isn't random. It seems like it could be Braille or something like that, maybe? I don't know, I might looking for patterns where there are none.<br />
<br />
Is it bother anyone that there are different numbers of eggs in each carton? At least there should have been two boxes for each alignment, one with an even number of eggs and one with odd.<br />
:: I was thinking precisely this. Can lead to a sense of "apples and oranges" otherwise. [[Special:Contributions/108.162.216.49|108.162.216.49]] 15:51, 7 January 2021 (UTC)MeZimm</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=Talk:1103:_Nine&diff=113391Talk:1103: Nine2016-02-26T15:11:58Z<p>108.162.216.49: Added comment</p>
<hr />
<div>Am I the only one that uses "99" whenever the instructions say something close to "1 minute 30 seconds"? [[Special:Contributions/108.162.216.49|108.162.216.49]] 15:11, 26 February 2016 (UTC)BenDanTomJack<br />
<br />
I really find that the hover-over text applies to me more often than not, unless I'm not in mixed company. This reminds me of a time that I was staying with a friend and she walked in on me changing the time on her microwave. When I explained to her that her microwave, stove, and coffee pot were all set to different times and it was bugging me, she just looked at me like I was crazy. --[[User:Grate314|&#34;grate314&#34;]] ([[User talk:Grate314|talk]]) 16:47, 3 September 2012 (UTC)<br />
:I don't think that is what the title text meant. Also, anybody who reads an xkcd comic and remembers that they did that ''is'' crazy. --[[Special:Contributions/98.221.139.80|98.221.139.80]]<br />
:I agree with grate314. I have to fix this every time the power goes out in my house because the stove, microwave, and radio all treat power outages differently. Between different rooms, though, it doesn't bother me. --[[User:DanB|DanB]] ([[User talk:DanB|talk]]) 19:04, 3 September 2012 (UTC)<br />
::I know that that isn't specifically what the hover-over text was talking about, but I was thinking of it in a more general way. I've just found that whenever someone asks me what I'm thinking about, it's best to say 'nothing'. What I meant by 'mixed company' is a general social gathering, like a wedding or birthday party. I'm an EE student, so when someone asks me that question at school, I answer honestly. The answer is usually 'soldering'. I think about soldering a lot. Thanks, DanB, the clocks were all on top of each other, btw, I'm not sure how she lived in that chaos.--[[User:Grate314|grate314]] ([[User talk:Grate314|talk]]) 21:27, 3 September 2012 (UTC)<br />
<br />
Did anybody try doing what the title text is saying? Just wondering. --[[Special:Contributions/98.221.139.80|98.221.139.80]]<br />
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When I'm not following written instructions, I tend to use multiples of 1:11, out of laziness. So, if I figure something should take about 2-3 minutes, I'll nuke it for 2:22. That way, I can press one button 3 times without having to move my finger. [[User:MGK|MGK]] ([[User talk:MGK|talk]]) 17:23, 3 September 2012 (UTC)<br />
<br />
If your microwave is connected to your home network you should accept that GCHQ have probably broken all your codes.[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 20:03, 20 January 2015 (UTC)<br />
<br />
I'm lazy and like to use repeated digits rather than have to move my finger along to find the next one - thus 33, 55, 66 get used a lot. I also find that for most items, longer time at lower power settings is more effective at even heating, so I do a lot of 66 at 50% rather than 33 at 100%. Our current oven only has 10 power settings, unlike a previous one that had two digit power settings resulting in 66 sec at 55% being a fairly commonly used setup. Interestingly, the logic of every microwave oven I have encountered treats 99 entered in the seconds display the same as if one were to have entered 1minute and 33 seconds. Thus 99:99 would be 100 minutes and 33 seconds. [[User:J-beda|J-beda]] ([[User talk:J-beda|talk]]) 17:31, 3 September 2012 (UTC)<br />
<br />
Oddly (apparently) my microwave has only 3 buttons (10 minutes, 1 minute, 10 seconds), though I do feel sorry for the 10 minute button.<br />
:Maybe it would make more sense to change the 10 minutes button to a 6 minutes button [[Special:Contributions/212.23.140.110|212.23.140.110]] 16:39, 5 September 2012 (UTC)<br />
<br />
I usually just push the "add 30 seconds" button until I reach the desired time (6 pushes for three minutes, 3 for 1:30, etc.). [[User:Erenan|Erenan]] ([[User talk:Erenan|talk]]) 16:06, 4 September 2012 (UTC)<br />
<br />
:mine only has a single analogue dial that jumps up in increasingly large steps, and for some reason is numbered to skip over some sensible times, such as six minutes. however, no buttons, so problem solved. [[Special:Contributions/86.15.83.223|86.15.83.223]] 22:00, 29 December 2012 (UTC)<br />
<br />
The 9 and 0 button are near each other so I do a lot of 90 (meaning 1 minute, 30 seconds). Sometimes, I'll get lazy<strike>er</strike> and press 99.<br />
<br />
'''Quasar '''unit offers the additional accuracy/simplicity/utility of min 10, 1 and sec 10, 1 There are no other numbers on the control face, which has 14 buttons total. hmm, Minimum number of buttons required to accomplish nuking?--[[User:Idkrash|Idkrash]] ([[User talk:Idkrash|talk]]) 01:28, 5 September 2012 (UTC)<br />
:For simplicity I would be in favor of 2 dials and 2 buttons. The dials could serve for power and time, which could output to digital displays. The buttons then could serve as start and stop. Pressing start and stop simultaneously would toggle the clock set function and you could use the dials to set the min and hour.----[[User:Shine|Shine]] ([[User talk:Shine|talk]]) 10:47, 5 September 2012 (UTC)<br />
::I suspect that sooner or later they'll all just have a power button and a touchscreen. [[User:Erenan|Erenan]] ([[User talk:Erenan|talk]]) 15:15, 5 September 2012 (UTC)<br />
::Agreed that the touchscreen is likely but you could get away with just the two dials by having the time dial start the oven when it is pulled out and stop when pushed in. (#Analog) --[[User:DanB|DanB]] ([[User talk:DanB|talk]]) 19:18, 5 September 2012 (UTC)<br />
::: My microwave already has a touch screen... we use the 30 second button on it a lot... --[[User:Tustin2121|Tustin2121]] ([[User talk:Tustin2121|talk]]) 16:36, 9 September 2012 (UTC)<br />
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[http://en.wikipedia.org/wiki/Benford's_law Benfords law] pops to mind.<br />
<br />
<br />
I don't use 20, 30 ,40, because find it easier to just click twice same button: 11, 22, 33, 44, 55, 66, 77, 88, 99 and anything beyond 99 seconds - well, 200 {{unsigned ip|82.71.241.138|17:25, 6 December 2012 (UTC)}}<br />
<br />
As a datum-point, my microwave has a (linear, clockwork, with mechanical bell-ding) dial, which is imprecise enough. Also it's a ''really'' old one (20 years old? 25? 30?) with a lower power than is common to see mentioned, so I look at the packaging recommendations, see perhaps 650W, 750W and 850W times, or 700W and 800W ones, and then add half again onto the lower rate's required time, and then perhaps a little more for good luck, as the amount I (roughly) twist the dial. I rarely use anything other than 'full'-power, out of the five settings. And I still sometimes need to renuke after testing. I really ought to get a new one. Probably would be more efficient, as well as accurate. ;) [[Special:Contributions/178.98.141.216|178.98.141.216]] 13:07, 31 March 2013 (UTC)<br />
<br />
Shockingly, no one has mentioned Cirno from Touhou Project.--[[Special:Contributions/67.78.126.46|67.78.126.46]] 12:41, 14 October 2013 (UTC)<br />
<br />
Shockingly, noone has mentioned that 159 seconds is closer to 3 minutes that it is to 2. [[User:Marklark|Marklark]] ([[User talk:Marklark|talk]]) 23:03, 29 December 2015 (UTC)</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=1079:_United_Shapes&diff=1115231079: United Shapes2016-02-12T01:48:35Z<p>108.162.216.49: </p>
<hr />
<div>{{comic<br />
| number = 1079<br />
| date = July 9, 2012<br />
| title = United Shapes<br />
| image = united_shapes.png<br />
| imagesize = 800px<br />
| titletext = That eggplant is in something of a flaccid state.<br />
}}<br />
The large version is here: [http://xkcd.com/1079/large/ http://xkcd.com/1079/large/]<br />
==Explanation==<br />
{{incomplete|The transcript should only mention what the picture looks like and the text in the pictures. All comments, should be in a separate part of the explanation with this table. Also the transcript should follow a realistic order of "reading" not alphabetical, that will be fine for the table with the explanation.}}<br />
In this comic, each state of the United States of America has been filled-in with an object of similar shape. Due to the size range of the states, some states are too small to clearly make-out in the normal size image. Click [http://xkcd.com/1079/large/ here] to see the large version, which makes every state perfectly clear. <br />
<br />
Very few, if any, of the shapes used are stereotypes of the state; they are merely objects that look like the state. Some of the objects are those which the states are widely known to resemble. For example, Michigan is represented by a glove and an Eagle, and a pot with handle takes the place of Oklahoma (with the panhandle region of the state filled with a literal handle). Others, however, are more creative. Few would have likely pictured Texas as a dog or Alaska as a bear with a jet pack and laser gun. There are several incredibly simple objects filling some states. Kentucky is filled by a cloud, which conceivably could have been used for any state, and Wyoming, one of the nearly rectangular states, is simply an envelope. There are three pairs of states that are related. Georgia and Missouri each contain an image of the other, drawing attention to their similar shapes, North and South Dakota are the top and bottom halves of an amp, and Alabama and Mississippi are {{w|moai}} facing in opposite directions.)<br />
<br />
Colorado contains what looks like a Wikipedia article. A close-up of the fake article is provided [http://xkcd.com/1079/colorado/]. The following references are made in the Colorado article:<br />
<br />
*The pronunciation is not that for Colorado, but for {{w|Eyjafjallajökull}}, a volcano in Iceland that erupted in April 2010.<br />
*The way it has a demilitarized zone towards Wyoming resembles {{W|North Korea}} and {{W|South Korea}}.<br />
*Eleven dimensions refers to {{w|string theory}}.<br />
*A {{w|wormhole}} is a theoretical relative of the {{w|black hole}}. This is a reference to the television series {{w|Stargate SG-1}} where a device capable of creating wormholes is located in the {{w|Cheyenne Mountain nuclear bunker}} in Colorado.<br />
*A {{w|Horcrux}} is a type of magical object in the world of {{W|Harry Potter}}.<br />
*The radiation zones around Longmont are caused by {{w|Radioactive contamination from the Rocky Flats Plant|radioactive contamination from the Rocky Flats Plant}}.<br />
*The fake motto ''Si parare possis, vivere septem'' can be roughly translated as "With preparation, survival is possible for over a week."<br />
<br />
New Mexico according to Randall's transcript is "A liquid container labeled for something of unusual and silly danger". The labeling is upside down and it refers to the nuclear testing facility White Sands Missile Range located in New Mexico for the nuclear bomb.<br />
:This end up<br />
:Property of White Sands Missile Range<br />
:??? [Followed by a [https://en.wikipedia.org/wiki/NFPA_704 NFPA 704] Diamond with all divisions at severe risk, and a radiation symbol in the special notice division]<br />
:Contains White Sand<br />
:FLAMMABLE<br />
:Warning: <br />
:This product contains chemicals known <br />
:only to the state of Nevada. <br />
:Contents under pressure from parents<br />
:If swallowed, induce labor<br />
:56 fluid ounces <br />
:and 14 other ounces<br />
<br />
The title text makes fun of Florida which is sometimes called "The penis of America". Obviously, this penis is somewhat flaccid (not erect). The use of the word "state" is a pun, as it means some particular condition (flaccid state) as well as a political entity (The State of Florida).<br />
<br />
==Transcript==<br />
{{incomplete transcript|The transcript should only mention what the picture looks like and the text in the pictures. All comments, should be in a separate part of the explanation with this table}}<br />
:The '''United Shapes'''<br />
:A map of things states are shaped like <br />
:[Each state has some item wedged to stay inside its borders]<br />
<br />
{|class=wikitable<br />
!Official transcript!!Comments<br />
|-<br />
|Alabama: A moai head facing east.||{{w|Moai}} are Easter Island stone statues<br />
|-<br />
|Alaska: A teddy bear with a jetpack and a ray gun||<br />
|-<br />
|Arizona: A refrigerated shelf containing milk, bread, and pastries.||<br />
|-<br />
|Arkansas: A measuring cup.||<br />
|-<br />
|California: A vacuum.||An old-fashioned upright vacuum cleaner (lying down to the right), green with a yellow bag.<br />
|-<br />
|Colorado: The wiki article on Colorado.||A fake Wikipedia article on Colorado. Below the text as seen in the provided close up:<br />
:[web address:]<br />
::en.wikipedia.org/wiki/colorado<br />
:[Headers]<br />
::Wikipedia<br />
::Article Talk<br />
::Colorado<br />
:[Main article {note that Randall forgot the closing parentheses ')' after the pronunciation}]<br />
::Colorado (Pronounced [ˈeːijaˌfjatlaˌjœːkʏtl̥] is a US State encompassing portions of the Rocky<br />
::Mountains and the Great Plains. The region has been inhabited since at least 11,000 BCE, and <br />
::some archaeological evidence suggest the state – with roughly its current borders – has literally<br />
::always existed. Colorado is separated from Wyoming by a 28-mile demilitarized zone, and <br />
::has at times exercised substantial regional <br />
::power via the installation of puppet governments<br />
::in neighboring states<br />
::Geographically, Colorado is eleven-dimensional,<br />
::though seven of those dimensions are tightly<br />
::compacted and difficult to detect in most areas<br />
::of the state. Colorado is home to the nation's<br />
::oldest continually-operated wormhole and two<br />
::of President Lincoln's horcruxes.<br />
::The wildlife in Colorado is commonly characterized <br />
::as "erratic", particularly in the radiation zones <br />
::around Longmont. The State's timber wolf<br />
::population is largely bipedal; the Park Service<br />
::has expressed "concern" at their attempts to enroll in<br />
:[Fact box with correct State flag and emblem and fake motto:]<br />
::State of Colorado<br />
::Motto:<br />
::"Si parare possis, vivere septem."<br />
::(With preparation, survival is<br />
::possible for over a week.)<br />
|-<br />
|Connecticut: A train conductor's hat.||<br />
|-<br />
|Delaware: A meerkat.||<br />
|-<br />
|Florida: An eggplant.||<br />
|-<br />
|Georgia: Missouri.||The outline of the state of Missouri, with the {{w|Gateway Arch}} in St. Louis.<br />
|-<br />
|Hawaii: A snowball.||<br />
|-<br />
|Idaho: A garden gnome, sitting down.||<br />
|-<br />
|Illinois: A gangster with a guitar case, upside down.||<br />
|-<br />
|Indiana: The brush of a paintbrush.||<br />
|-<br />
|Iowa: A tomato, lettuce, cold cut and cheese sandwich.||<br />
|-<br />
|Kansas: A stand-up piano.||<br />
|-<br />
|Kentucky: A cloud.||<br />
|-<br />
|Louisiana: A boot with some gum stuck to the bottom of it.||<br />
|-<br />
|Maine: A Vulcan salute.||<br />
|-<br />
|Maryland: A wolf howling to the moon, upside down.||<br />
|-<br />
|Massachusetts: An elephant, being ridden by a man, carrying tea.||<br />
|-<br />
|Michigan: A mitten for the lower portion, an eagle for the U{{w|Upper Peninsula of Michigan}}.||<br />
|-<br />
|Minnesota: $160 in $20 USD bills.||<br />
|-<br />
|Mississippi: A moai head facing west.||<br />
|-<br />
|Missouri: Georgia.||The outline of the state of Georgia, with a pair of {{w|Georgia Peach|Georgia peaches}}.<br />
|-<br />
|Montana: One half of a muffin.||<br />
|-<br />
|Nebraska: A blue VW type 2 with mattresses sticking out the back.||<br />
|-<br />
|Nevada: A clothes iron.||<br />
|-<br />
|New Hampshire: A tall brick factory building.||<br />
|-<br />
|New Jersey: A bent-over old person.||<br />
|-<br />
|New Mexico: A liquid container labeled for something of unusual and silly danger.||A yellow liquid container with upside-down labeling.<br />
::This end up!!<br />
::Property of White Sands Missile Range<br />
::Contains White Sand<br />
:[Written inside a hazardous-materials diamond with the ? very large, and the three '4' in the three top part of a diamond shape divided in four these three sections being blue, red, yellow. The lower part has a radioactive sign on the same grey background as the large rectangle.]<br />
::??? 4 4 4 <br />
::Flammable<br />
::Warning<br />
::This product contains chemicals known<br />
::Only to the Sate of Nevada.<br />
::Contents under pressure from rich parents<br />
::If swallowed, induce labor<br />
::56 fluid ounces<br />
::and 14 other ounces<br />
|-<br />
|New York: A hybrid transmission with standard manual-style gears and a torque converter sliced in half.||<br />
|-<br />
|North Carolina: A bouquet of flowers.||<br />
|-<br />
|North Dakota: The top half of an amp.||<br />
|-<br />
|Ohio: Underwear (Briefs).||<br />
|-<br />
|Oklahoma: A covered pot, dripping with boil-over.||<br />
|-<br />
|Oregon: A locomotive.||<br />
|-<br />
|Pennsylvania: A very thick book with a bookmark.||<br />
|-<br />
|Rhode Island: The bow half of a boat's hull.||<br />
|-<br />
|South Carolina: A slice of pizza.||<br />
|-<br />
|South Dakota: The bottom half of an amp.||<br />
|-<br />
|Tennessee: A number of children's books, placed in a slightly askew pile.||<br />
|-<br />
|Texas: A dog sitting in a bowl.||<br />
|-<br />
|Utah: An oven.||<br />
|-<br />
|Vermont: A microscope, upside down.||<br />
|-<br />
|Virginia: A {{w|stegosaurus}}.||<br />
|-<br />
|Washington: A whale.||<br />
|-<br />
|Washington DC: A star.||<br />
|-<br />
|West Virginia: A {{w|frog}}.||<br />
|-<br />
|Wisconsin: A skull.||<br />
|-<br />
|Wyoming: An envelope.||The back side of a white envelope, sealed with red wax, with a black heart next to a signature (lower left corner).<br />
|}<br />
<br />
{{comic discussion}}<br />
<br />
[[Category:Large drawings]]<br />
[[Category:Comics with color]]<br />
[[Category:Maps]]<br />
[[Category:Food]]<br />
[[Category:Animals]]<br />
[[Category:Dinosaurs]]<br />
[[Category:Wikipedia]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=1079:_United_Shapes&diff=1115221079: United Shapes2016-02-12T01:42:28Z<p>108.162.216.49: </p>
<hr />
<div>{{comic<br />
| number = 1079<br />
| date = July 9, 2012<br />
| title = United Shapes<br />
| image = united_shapes.png<br />
| imagesize = 800px<br />
| titletext = That eggplant is in something of a flaccid state.<br />
}}<br />
The large version is here: [http://xkcd.com/1079/large/ http://xkcd.com/1079/large/]<br />
==Explanation==<br />
{{incomplete|The transcript should only mention what the picture looks like and the text in the pictures. All comments, should be in a separate part of the explanation with this table. Also the transcript should follow a realistic order of "reading" not alphabetical, that will be fine for the table with the explanation.}}<br />
In this comic, each state of the United States of America has been filled-in with an object of similar shape. Due to the size range of the states, some states are too small to clearly make-out in the normal size image. Click [http://xkcd.com/1079/large/ here] to see the large version, which makes every state perfectly clear. <br />
<br />
Very few, if any, of the shapes used are stereotypes of the state; they are merely objects that look like the state. Some of the objects are those which the states are widely known to resemble. For example, Michigan is represented by a glove and an Eagle, and a pot with handle takes the place of Oklahoma (with the panhandle region of the state filled with a literal handle). Others, however, are more creative. Few would have likely pictured Texas as a dog or Alaska as a bear with a jet pack and laser gun. There are several incredibly simple objects filling some states. Kentucky is filled by a cloud, which conceivably could have been used for any state, and Wyoming, one of the nearly rectangular states, is simply an envelope. There are three pairs of states that are related. Georgia and Missouri each contain an image of the other, drawing attention to their similar shapes, North and South Dakota are the top and bottom halves of an amp, and Alabama and Mississippi are {{w|moai}} facing in opposite directions.)<br />
<br />
Colorado contains what looks like a Wikipedia article. A close-up of the fake article is provided [http://xkcd.com/1079/colorado/]. The following references are made in the Colorado article:<br />
<br />
*The pronunciation is not that for Colorado, but for {{w|Eyjafjallajökull}}, a volcano in Iceland that erupted in April 2010.<br />
*The way it has a demilitarized zone towards Wyoming resembles {{W|North Korea}} and {{W|South Korea}}.<br />
*Eleven dimensions refers to {{w|string theory}}.<br />
*A {{w|wormhole}} is a theoretical relative of the {{w|black hole}}. This is a reference to the television series {{w|Stargate SG-1}} where a device capable of creating wormholes is located in the {{w|Cheyenne Mountain nuclear bunker}} in Colorado.<br />
*A {{w|Horcrux}} is a type of magical object in the world of {{W|Harry Potter}}.<br />
*The radiation zones around Longmont are caused by {{w|Radioactive contamination from the Rocky Flats Plant|radioactive contamination from the Rocky Flats Plant}}.<br />
*The fake motto ''Si parare possis, vivere septem'' can be roughly translated as "With preparation, survival is possible for over a week."<br />
<br />
New Mexico according to Randall's transcript is "A liquid container labeled for something of unusual and silly danger". The labeling is upside down and it refers to the nuclear testing facility White Sands Missile Range located in New Mexico for the nuclear bomb.<br />
:This end up<br />
:Property of White Sands Missile Range<br />
:??? [Followed by a [https://en.m.wikipedia.org/wiki/NFPA_704 NFPA 704] Diamond with all divisions at severe risk, and a radiation symbol in the special notice division]<br />
:Contains White Sand<br />
:FLAMMABLE<br />
:Warning: <br />
:This product contains chemicals known <br />
:only to the state of Nevada. <br />
:Contents under pressure from parents<br />
:If swallowed, induce labor<br />
:56 fluid ounces <br />
:and 14 other ounces<br />
<br />
The title text makes fun of Florida which is sometimes called "The penis of America". Obviously, this penis is somewhat flaccid (not erect). The use of the word "state" is a pun, as it means some particular condition (flaccid state) as well as a political entity (The State of Florida).<br />
<br />
==Transcript==<br />
{{incomplete transcript|The transcript should only mention what the picture looks like and the text in the pictures. All comments, should be in a separate part of the explanation with this table}}<br />
:The '''United Shapes'''<br />
:A map of things states are shaped like <br />
:[Each state has some item wedged to stay inside its borders]<br />
<br />
{|class=wikitable<br />
!Official transcript!!Comments<br />
|-<br />
|Alabama: A moai head facing east.||{{w|Moai}} are Easter Island stone statues<br />
|-<br />
|Alaska: A teddy bear with a jetpack and a ray gun||<br />
|-<br />
|Arizona: A refrigerated shelf containing milk, bread, and pastries.||<br />
|-<br />
|Arkansas: A measuring cup.||<br />
|-<br />
|California: A vacuum.||An old-fashioned upright vacuum cleaner (lying down to the right), green with a yellow bag.<br />
|-<br />
|Colorado: The wiki article on Colorado.||A fake Wikipedia article on Colorado. Below the text as seen in the provided close up:<br />
:[web address:]<br />
::en.wikipedia.org/wiki/colorado<br />
:[Headers]<br />
::Wikipedia<br />
::Article Talk<br />
::Colorado<br />
:[Main article {note that Randall forgot the closing parentheses ')' after the pronunciation}]<br />
::Colorado (Pronounced [ˈeːijaˌfjatlaˌjœːkʏtl̥] is a US State encompassing portions of the Rocky<br />
::Mountains and the Great Plains. The region has been inhabited since at least 11,000 BCE, and <br />
::some archaeological evidence suggest the state – with roughly its current borders – has literally<br />
::always existed. Colorado is separated from Wyoming by a 28-mile demilitarized zone, and <br />
::has at times exercised substantial regional <br />
::power via the installation of puppet governments<br />
::in neighboring states<br />
::Geographically, Colorado is eleven-dimensional,<br />
::though seven of those dimensions are tightly<br />
::compacted and difficult to detect in most areas<br />
::of the state. Colorado is home to the nation's<br />
::oldest continually-operated wormhole and two<br />
::of President Lincoln's horcruxes.<br />
::The wildlife in Colorado is commonly characterized <br />
::as "erratic", particularly in the radiation zones <br />
::around Longmont. The State's timber wolf<br />
::population is largely bipedal; the Park Service<br />
::has expressed "concern" at their attempts to enroll in<br />
:[Fact box with correct State flag and emblem and fake motto:]<br />
::State of Colorado<br />
::Motto:<br />
::"Si parare possis, vivere septem."<br />
::(With preparation, survival is<br />
::possible for over a week.)<br />
|-<br />
|Connecticut: A train conductor's hat.||<br />
|-<br />
|Delaware: A meerkat.||<br />
|-<br />
|Florida: An eggplant.||<br />
|-<br />
|Georgia: Missouri.||The outline of the state of Missouri, with the {{w|Gateway Arch}} in St. Louis.<br />
|-<br />
|Hawaii: A snowball.||<br />
|-<br />
|Idaho: A garden gnome, sitting down.||<br />
|-<br />
|Illinois: A gangster with a guitar case, upside down.||<br />
|-<br />
|Indiana: The brush of a paintbrush.||<br />
|-<br />
|Iowa: A tomato, lettuce, cold cut and cheese sandwich.||<br />
|-<br />
|Kansas: A stand-up piano.||<br />
|-<br />
|Kentucky: A cloud.||<br />
|-<br />
|Louisiana: A boot with some gum stuck to the bottom of it.||<br />
|-<br />
|Maine: A Vulcan salute.||<br />
|-<br />
|Maryland: A wolf howling to the moon, upside down.||<br />
|-<br />
|Massachusetts: An elephant, being ridden by a man, carrying tea.||<br />
|-<br />
|Michigan: A mitten for the lower portion, an eagle for the U{{w|Upper Peninsula of Michigan}}.||<br />
|-<br />
|Minnesota: $160 in $20 USD bills.||<br />
|-<br />
|Mississippi: A moai head facing west.||<br />
|-<br />
|Missouri: Georgia.||The outline of the state of Georgia, with a pair of {{w|Georgia Peach|Georgia peaches}}.<br />
|-<br />
|Montana: One half of a muffin.||<br />
|-<br />
|Nebraska: A blue VW type 2 with mattresses sticking out the back.||<br />
|-<br />
|Nevada: A clothes iron.||<br />
|-<br />
|New Hampshire: A tall brick factory building.||<br />
|-<br />
|New Jersey: A bent-over old person.||<br />
|-<br />
|New Mexico: A liquid container labeled for something of unusual and silly danger.||A yellow liquid container with upside-down labeling.<br />
::This end up!!<br />
::Property of White Sands Missile Range<br />
::Contains White Sand<br />
:[Written inside a hazardous-materials diamond with the ? very large, and the three '4' in the three top part of a diamond shape divided in four these three sections being blue, red, yellow. The lower part has a radioactive sign on the same grey background as the large rectangle.]<br />
::??? 4 4 4 <br />
::Flammable<br />
::Warning<br />
::This product contains chemicals known<br />
::Only to the Sate of Nevada.<br />
::Contents under pressure from rich parents<br />
::If swallowed, induce labor<br />
::56 fluid ounces<br />
::and 14 other ounces<br />
|-<br />
|New York: A hybrid transmission with standard manual-style gears and a torque converter sliced in half.||<br />
|-<br />
|North Carolina: A bouquet of flowers.||<br />
|-<br />
|North Dakota: The top half of an amp.||<br />
|-<br />
|Ohio: Underwear (Briefs).||<br />
|-<br />
|Oklahoma: A covered pot, dripping with boil-over.||<br />
|-<br />
|Oregon: A locomotive.||<br />
|-<br />
|Pennsylvania: A very thick book with a bookmark.||<br />
|-<br />
|Rhode Island: The bow half of a boat's hull.||<br />
|-<br />
|South Carolina: A slice of pizza.||<br />
|-<br />
|South Dakota: The bottom half of an amp.||<br />
|-<br />
|Tennessee: A number of children's books, placed in a slightly askew pile.||<br />
|-<br />
|Texas: A dog sitting in a bowl.||<br />
|-<br />
|Utah: An oven.||<br />
|-<br />
|Vermont: A microscope, upside down.||<br />
|-<br />
|Virginia: A {{w|stegosaurus}}.||<br />
|-<br />
|Washington: A whale.||<br />
|-<br />
|Washington DC: A star.||<br />
|-<br />
|West Virginia: A {{w|frog}}.||<br />
|-<br />
|Wisconsin: A skull.||<br />
|-<br />
|Wyoming: An envelope.||The back side of a white envelope, sealed with red wax, with a black heart next to a signature (lower left corner).<br />
|}<br />
<br />
{{comic discussion}}<br />
<br />
[[Category:Large drawings]]<br />
[[Category:Comics with color]]<br />
[[Category:Maps]]<br />
[[Category:Food]]<br />
[[Category:Animals]]<br />
[[Category:Dinosaurs]]<br />
[[Category:Wikipedia]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=Talk:1460:_SMFW&diff=110012Talk:1460: SMFW2016-01-26T14:13:19Z<p>108.162.216.49: Added comment</p>
<hr />
<div>SMFW = so much fun when. "So much fun when an acronym almost makes sense."<br />
[[Special:Contributions/108.162.216.49|108.162.216.49]] 14:13, 26 January 2016 (UTC)<br />
<br />
Reading this is like listening to the video of that lady who imitates the sound patterns of different languages, but without actually saying any real words! --[[User:Elipongo|Elipongo]] ([[User talk:Elipongo|talk]]) 05:34, 15 December 2014 (UTC)<br />
:link? -- [[User:Brettpeirce|Brettpeirce]] ([[User talk:Brettpeirce|talk]]) 15:41, 15 December 2014 (UTC)<br />
::https://www.youtube.com/watch?v=ybcvlxivscw [[Special:Contributions/199.27.130.192|199.27.130.192]] 19:56, 15 December 2014 (UTC)<br />
:No. It's absolutely '''nothing''' like that. If this were reddit I'd downvote you. --[[Special:Contributions/173.245.54.180|173.245.54.180]] 19:18, 16 December 2014 (UTC)<br />
<br />
It would sound more natural if it were "''SMFW '''as''' an acronym almost makes sense''". Is the fact that "as" was omitted from that sentence supposed to give us a hint as to what "SMFW" might mean? [[User:Nicksh|Nicksh]] ([[User talk:Nicksh|talk]]) 07:16, 15 December 2014 (UTC)<br />
<br />
: As "the Internet is for porn", in many contexts SFW, lit. Safe for Work, can be taken to mean sex-free content, while NSFW, Not Safe for Work, would mean sex-positive content, then SMFW might be interpreted to me SM For Work, where SM would be humorously interpreted as some graphically explicit sex-positive content, perhaps SadoMachoism, which outside of paperwork is generally classified NSFW. [[Special:Contributions/199.27.133.29|199.27.133.29]] 10:31, 15 December 2014 (UTC)<br />
<br />
:: And "wtfw it's like smho tbfh, imdb." might be a defensive reaction to those what would not find humour of SM For Work. "what the fooking wut? It's like stick my humble opinion, to be fooking honest, in my dead body. (or database)." [[Special:Contributions/199.27.133.29|199.27.133.29]] 10:38, 15 December 2014 (UTC)<br />
<br />
:: Additional evidence of SM For Work, would be the posture in the task chair with respect to the desk and laptop (hunched over, feet not resting on ground, etc) seems the opposite of ergonomic advice which might lead to muscle strain, pain and fatigue -- the type of unsexy, self-inflicted torments that workers do to themselves "for work" {{unsigned ip|199.27.133.29}}<br />
<br />
: >It would sound more natural<br />
: You're missing the whole point. It's not ''supposed'' to sound natural. It's supposed to look strange and confuse you. That's the joke. --[[Special:Contributions/173.245.54.180|173.245.54.180]] 19:20, 16 December 2014 (UTC)<br />
<br />
I thought it was simply 'Save Me From Work' - being unhappy at work is common, and using the internet as a distraction from work is common as well. - So sending a quick message to a friend "SMFW" is a request for them to send you a link or other internet distraction, or otherwise help you come up with an excuse to not be productive. {{unsigned ip|108.162.221.206}}<br />
<br />
<br />
I thought of So Much For Work as a possible meaning. {{unsigned ip|173.245.50.178}}<br />
<br />
SMFW: Single Mode Fiber Waveguide * {{unsigned ip|108.162.216.39}}<br />
<br />
<br />
I think "SMFW" is a mixture of SMF and MFW: "So Much Fun When". It fits the sentence. The only thing is that Cueball doesn't look like he's having fun.<br />
<br />
Smoke more fucking weed could be a replacement for something like "Bloody hell" or "Shit the bed".<br />
[[Special:Contributions/141.101.98.252|141.101.98.252]] 09:05, 15 December 2014 (UTC)<br />
<br />
So why doesn't "xkcd" appear on the acronyms list? --[[User:Koveras|Koveras]] ([[User talk:Koveras|talk]]) 09:47, 15 December 2014 (UTC)<br />
: Because xkcd isnt an acronym. [[Special:Contributions/108.162.216.61|108.162.216.61]] 09:56, 15 December 2014 (UTC)<br />
<br />
I would like to add STFW ("Search the fucking web", [http://en.wiktionary.org/wiki/STFW]) as an acronym that SMFW is close to (same except for the second letter)...but there might be enough examples? [[User:Aquaplanet|Aquaplanet]] ([[User talk:Aquaplanet|talk]]) 11:07, 15 December 2014 (UTC)<br />
<br />
<br />
SMFW makes perfect sense. Shaking my face when (SMH+MFW) an acronym almost makes sense. {{unsigned|Sederts}}<br />
:Seconded, "Shaking my face when" seems to be the best decryption so far... [[Special:Contributions/108.162.219.249|108.162.219.249]] 23:12, 15 December 2014 (UTC)<br />
<br />
See My Face When an acronym almost makes sense... makes perfect sense. [[Special:Contributions/141.101.99.4|141.101.99.4]] 13:26, 15 December 2014 (UTC)<br />
<br />
<br />
"So Much Frustration When an acronym ''almost'' makes sense."<br />
: +1 -- [[User:Brettpeirce|Brettpeirce]] ([[User talk:Brettpeirce|talk]]) 15:44, 15 December 2014 (UTC)<br />
: I'd also like to add in my +1 on this -- [[Special:Contributions/108.162.216.188|108.162.216.188]] 19:39, 15 December 2014 (UTC)<br />
: +1 [[User:Ursushoribilis|Ursushoribilis]] ([[User talk:Ursushoribilis|talk]]) 15:33, 21 December 2014 (UTC)<br />
<br />
"What to feel when it's like some message has only to be f...ing hashtags, is mostly deep bafflement." [[User:Ackegard|Ackegard]] ([[User talk:Ackegard|talk]]) 14:35, 15 December 2014 (UTC)<br />
<br />
None of these are acronyms. [[Special:Contributions/199.27.128.115|199.27.128.115]] 14:55, 15 December 2014 (UTC)<br />
<br />
So Much F*cking Want. So, uh. Yeah. [[Special:Contributions/108.162.237.124|108.162.237.124]] 15:10, 15 December 2014 (UTC)<br />
<br />
Small Men Fear Women [[Special:Contributions/108.162.216.39|108.162.216.39]] 15:27, 15 December 2014 (UTC)<br />
<br />
So Many Fucking Ways an acronym almost makes sense. Makes sense to me. {{unsigned ip|108.162.230.209}}<br />
<br />
Staring, Mildly Frustrated When...? [[User:Kirdneh|Kirdneh]] ([[User talk:Kirdneh|talk]]) 17:50, 15 December 2014 (UTC)<br />
<br />
"SMHO" could also be related to "LMHO," or "Laughing My Head Off." So, "Shaking My Head Off"? Something that makes you shake your head so hard it might fall off? [[User:Shanek|Shanek]] ([[User talk:Shanek|talk]]) 16:12, 15 December 2014 (UTC)<br />
<br />
SMFW is an initialism. [[Special:Contributions/108.162.230.131|108.162.230.131]] 16:45, 15 December 2014 (UTC)<br />
<br />
<pedantic>Initialisms are only acronyms when they can be pronounced </pendantic> [[User:Sideshowtanley|Sideshowtanley]] ([[User talk:Sideshowtanley|talk]]) 17:16, 15 December 2014 (UTC)<br />
<br />
: smif-whaa? (smfw) wha-ti-fuh? (wtf) zik-cid? (xkcd) Can be pronounced or intended to be pronounced? Two very different things. [[Special:Contributions/108.162.216.64|108.162.216.64]] 01:47, 16 December 2014 (UTC)<br />
<br />
I was thinking "So M*therf*cking what?" as the meaning for the acronym, but Randall is more arcane than that :) [[Special:Contributions/173.245.49.148|173.245.49.148]] 17:49, 15 December 2014 (UTC)<br />
<br />
"Social Media Forum Warrior" is what came to my mind. I may have been on the internets for too long. [[Special:Contributions/141.101.104.137|141.101.104.137]] 19:22, 15 December 2014 (UTC)<br />
<br />
Could be an example of a stacked acronym with an acronym recursively nested in an acronym. Or it could be a portmanteau of two acronyms. Is there a term for a portmanteau of two acronyms? Portmonym? Acmanteau? --[[User:Gbleck|Gbleck]] ([[User talk:Gbleck|talk]]) 19:31, 15 December 2014 (UTC)gbleck<br />
<br />
It's not meant to make sense. It's a play on acronyms not making sense. It is a single statement in a single sentence, but the play is on the fact that the acronym doesn't make sense. {{unsigned ip|141.101.98.207}}<br />
<br />
Smacks My Face When an acronym almost makes sense. {{unsigned ip|108.162.238.160}}<br />
<br />
Two things - 1) these are all abbreviations, not acronyms - no-one goes around saying "Smfw" - they'd say "S.M.F.W."; 2) WTFW is "whatever the fuck works" - used quite often on a couple of forums I've been on. [[User:Grutness|Grutness]] ([[User talk:Grutness|talk]]) 23:11, 15 December 2014 (UTC)<br />
: I think there are two different, valid definitions of acronyms. Personally the first "acronym" I think of as an example is ATM machine, which you're saying is an abbreviation. I guess some people draw the line if it uses the initials of words, and other draw the line at being pronounced. [[Special:Contributions/108.162.215.187|108.162.215.187]] 12:45, 16 December 2014 (UTC)<br />
:Of course you're suffering from RAS Syndrome when you say "ATM Machine", anyway, whatever you call it. [[Special:Contributions/141.101.98.245|141.101.98.245]] 13:17, 17 December 2014 (UTC)<br />
<br />
<br />
<br />
<br />
Maybe it's So My Face When an ancryonom alost makes sense [[Special:Contributions/141.101.98.203|141.101.98.203]] 18:53, 15 March 2015 (UTC)<br />
<br />
TDEMSYR!!! [[Special:Contributions/141.101.89.217|141.101.89.217]] 10:03, 16 December 2014 (UTC)<br />
<br />
Maybe “SMFW” could mean “So Much Fun When” — wait, that makes too much sense. [[User:Jolbucley|Jolbucley]] ([[User talk:Jolbucley|talk]]) 02:28, 17 December 2014 (UTC)<br />
<br />
I thought it meant "So Much For Work" Something I would mutter to myself when distracted by XKCD [[Special:Contributions/108.162.250.222|108.162.250.222]] 04:54, 17 December 2014 (UTC)<br />
<br />
Couldn't SMFW mean "Sorta My Face When"?<br />
[[Special:Contributions/108.162.231.27|108.162.231.27]] 05:11, 17 December 2014 (UTC)<br />
<br />
PCMCIA! (People cant memorize computer industry acronyms). SMFW... Somewhat Mediocre For Work? Specialy Mindbogling For Work? Super Mario Friday Workout? Something Might Fall When? Streets Must Freeze Wednesdays! Should Mum Fry Warderobe? Show Me Fried Wintercoat! Steve Must Find Wholesaler. (for fried wintercoat, indeed). So Many "Friction" Words! Should Maybe First... Whatever. Somewhat Memorable First Words? So, Maybe, Fire Works. Sh!t May Fly Wherever. (And I refuse to write down the more NSFW options) -[[Special:Contributions/173.245.53.234|173.245.53.234]] 21:32, 17 December 2014 (UTC)<br />
<br />
"(if one discounts IMDB, which is only there to make an already obnoxious sentence completely absurd)" I actually think it's who the message is addressed to, compare "WTF, NSA?". The message then expresses incredulous disappointment in something IMDB, or more likely the user base, did (like a 1-star review for Firefly). [[Special:Contributions/141.101.104.136|141.101.104.136]] 11:42, 18 December 2014 (UTC)<br />
<br />
You guys are all missing the obvious meaning: "'''S'''o '''M'''any '''F'''eel(ing)s '''W'''hen an acronym almost makes sense."<br />
[[Special:Contributions/108.162.217.71|108.162.217.71]] 01:46, 24 December 2014 (UTC)<br />
<br />
I interpreted it as "Show Me Five Ways". [[Special:Contributions/173.245.54.204|173.245.54.204]] 04:25, 3 January 2015 (UTC)<br />
<br />
Some Mother Fucking Way {{unsigned ip|108.162.215.192}}<br />
<br />
Well, MFW can mean "motherfucking win", so my first thought was "such motherfucking win". [[Special:Contributions/141.101.98.211|141.101.98.211]] 19:14, 24 December 2014 (UTC)<br />
<br />
Acronym <> Initialism. {{unsigned ip|108.162.216.95}}<br />
<br />
SMFW could also be "So Much Fucking Work".[[Special:Contributions/173.245.56.199|173.245.56.199]] 15:16, 15 January 2015 (UTC)<br />
<br />
See my face when... is ironic considering Cueball's face consists of a blank circle. Cueball's slumped posture may imply he is lamenting the lack of facial expression.[[User:JBinSV|JBinSV]] ([[User talk:JBinSV|talk]]) 07:00, 14 February 2015 (UTC)<br />
<br />
SMHO is similar to SWMBO, "She Who Must Be Obeyed"; a passive aggressive reference to one's wife. Also why has no one noted that the title of the comic itself is a false acronym? XKCD stands for nothing. Randall is so meta even this comic… [[User:Saspic45|Saspic45]] ([[User talk:Saspic45|talk]]) 14:22, 25 January 2016 (UTC)</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=1621:_Fixion&diff=1078201621: Fixion2015-12-26T05:20:18Z<p>108.162.216.49: </p>
<hr />
<div>{{comic<br />
| number = 1621<br />
| date = December 25, 2015<br />
| title = Fixion<br />
| image = fixion.png<br />
| titletext = My theory predicts that, at high enough energies, FRBs and perytons become indistinguishable because the detector burns out.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|This explanation is very incomplete. It is a small and terrible draft, only listing some immediate things I have noticed. This article should be structured as: General idea, table of explanations for each property.}}<br />
The second [[:Category:Christmas|Christmas]] comic in a row, this one - released on Christmas day - is a present to all physicists of a new particle, the ''Fixion'', which explains everything.<br />
<br />
In physics, there are still many big questions and mysteries. There are many phenomena which don't seem to fit, and we don't know how to explain yet. The "fixion" is satirically presented as a particle which acts as a {{w|Deus ex machina}} (see also [https://www.tvtropes.org/pmwiki/pmwiki.php/Main/DeusExMachina tvtropes]) which solves all of these mysteries without any serious fundamental reasons.<br />
<br />
The style of the chart suggests a {{w|Feynmann diagram}} - an easy way of drawing particle interactions. Typically, fermions (the "solid" particles like electrons and quarks) are shown with solid lines, photons (and generally the weak-force-carrying bosons) are shown with wavy lines, gluons with spiraling lines and other mediating particles (such as pions in the nuclear force, or the Higgs) with a dotted line. Randall obeys these rules only very loosely, which makes sense - many of the things involved in this Feynmann diagram are either so theoretical that they have no widely used standard representation, or would never appear in a sensible diagram (spacecraft, for instance).<br />
<br />
===Table of Phenomena===<br />
{| border =1 width=100% cellpadding=5<br />
|'''Phenomenon''' || '''Description''' || '''Solved?'''<br />
|- <br />
| Main component of {{w|dark matter}} || Our best measurements of the universe predict that visible matter is only about one-sixth of the matter in the universe; the remaining matter is "dark matter" that cannot be seen. The leading candidates for dark matter are {{w|WIMPs}} - weakly interacting massive particles. These would be new, undiscovered forms of matter which barely interact except through gravity and thus give off little or no light. Some of the dark matter is likely made up of {{w|MACHOs}} - massive compact halo objects; effectively dead stars too dim to see. MACHOs are probably only a minority of the dark matter, however. Studies of two colliding galaxy clusters suggest that dark matter can pass through other matter without slowing down, unlike ordinary matter. Moreover, calculations of the elements produced during the big bang - which match the observed distribution of elements in the universe very precisely - don't leave room for enough additional protons and neutrons to form the dark matter. || No, and proving the nature of dark matter will win someone the Nobel Prize.<br />
|-<br />
| Confines {{w|quark}}s and {{w|gluon}}s || {{w|Quark confinement}} means that we never see particles with {{w|colour charge|color charge}} (i.e. quarks and gluons) on their own. They only exist in groups that cancel out the color charge. Try to separate the groups, and the energy you add will instead cause new particles to pop into existence. || The basic facts of confinement are well understood, but some of the details are too complicated to tease out.<br />
|-<br />
| Suppresses antimatter in early universe || The universe today is made almost entirely of matter. Antimatter and matter are identical, except that the charges are opposite. Antimatter and matter "annihilate" when they come into contact? So why is the universe made of matter? Why didn't the universe have equal amounts of both, and if it did, why didn't it annihilate itself immediately? This is a big question in physics today. Of course, the fixion explains this. || Lots of theories, no conclusive evidence for any yet. The most notable theories revolve around the weak interaction, which has been shown to treat matter and antimatter asymmetrically. Now that the Higgs boson has been found, the biggest project for the {{w|Large Hadron Collider}} experiments is to try to crack this.<br />
|-<br />
| Neutralizes monopoles || {{w|Magnetic monopoles}} (i.e., a north charge without a south charge) should exist, according to many GUTs (grand unified theories) and string theories, but none have ever been seen. || No (despite claims that pop up in the news every year, creating a monopole-like state in the magnetic spins of a crystal is not the same as creating a real monopole.)<br />
|-<br />
| Spontaneously emits {{w|dark energy}} || Prior to the 1990s, most cosmologists expected that the universe's expansion after the Big Bang would either slow down or stay constant. In 1998, cosmologists discovered that the expansion of the Universe is accelerating. Under Einstein's theory of general relativity, the observed acceleration predicts that ordinary matter and dark matter make up about 30% of the universe's total energy, with the rest coming in the form of "dark energy." The nature of dark energy is not certain. However, the leading candidate is that space itself has intrinsic energy (either constant or variable), and so as space expands, the energy of the universe increases. || Again, Nobel Prize territory.<br />
|-<br />
| Mediates {{w|proton decay}}, but then hides it. || Many GUTs predict that protons will decay, but experiments have shown the proton to have a half life of at least the age of the universe. || It's not ''necessarily'' a problem. All theories predict that proton decay is a very slow process (10<sup>32+</sup> seconds), which is consistent with the current data.<br />
|-<br />
| Broken symmetry causes ϴ=0, explaining unobserved neutron dipole moment || The {{w|neutron electric dipole moment}} is a measure of how balanced electric charge is inside the neutron. ϴ (theta) is a number in quantum chromodynamics which quantifies the the breaking of a type of symmetry called {{w|CP violation|CP symmetry}}. If ϴ is not 0, one result of this should be a neutron dipole moment. {{w|Symmetry breaking}} is a common explanation of effects in some areas of theoretical physics (for instance, it's an important part of Higgs' theory about why particles have mass), but normally it explains why a value is ''not'' zero. Presumably the fixion breaks CP symmetry independently of QCD, which means that ϴ can be 0 while preserving observed CP-breaking effects. || Again, it's not (yet) a problem - the predicted dipole moment is tiny, and we're only just reaching the point when we can measure it that accurately.<br />
|-<br />
| Introduces dispersion in perytons from kitchen microwaves, explaining fast radio bursts || {{w|Fast radio burst}}s are unexplained bursts of radio-frequency energy from space. {{w|Peryton}}s are things that ''look like'' FRBs, but come from Earth (specifically, from the microwave oven at Parkes Observatory). Randall's fixions makes some perytons change frequency distribution so they appear to come from space. || No, but it's probably something very big - a star collapsing to a black hole or (as now looks likely) a {{w|magnetar}} (magnetic neutron star)<br />
|-<br />
| Covers naked singularities || A {{w|naked singularity}} is like a black hole without an {{w|event horizon}}. So far no naked singularity has been observed (except, arguably, the big bang) and the {{w|cosmic censorship hypothesis}} suggests they can't exist, although some people have suggested ways of making them. || Not necessarily something that needs explaining - none have been seen, and most theories say they don't exist. If support grows for {{w|loop quantum gravity}}, then we might have to start really searching.<br />
|-<br />
| Causes {{w|alpha effect}} || A weird effect from chemistry, where putting an "alpha" atom with a {{w|lone pair}} of electrons close to a molecule makes the molecule more likely to give up its electrons. || Lots of competing explanations.<br />
|-<br />
| Causes coronal heating || For some reason the outer layer of the sun (the {{w|corona}}) is hotter than most reasonable theories predict. || It's a mystery, but it possibly has something to do with waves in the corona (for example, the {{w|High Resolution Coronal Imager}} has seen "braids" in the corona that whip around and unravel themselves).<br />
|-<br />
| Intercepts certain {{w|gravitational waves}} before they're observed. || If gravity behaves like the other forces, it must be conveyed by waves. Our best detector, {{w|LIGO}} has yet to detect any gravitational waves, though this is probably just due to the low probability of events that would be detectable. Only extreme events like binary black hole mergers are detectable with the current setup. The proposed LISA spacecraft will be able to see things like orbiting black holes and neutron stars. || Let's wait for the LISA data before jumping to conclusions.<br />
|-<br />
| Higgs-ish || The {{w|Higgs boson}} is a manifestation of the Higgs field... but many supersymmetry and string theories predict multiple Higgs-like particles. It's almost a prerequisite of any new theory that it has a Higgs-ish element. || N/A<br />
|-<br />
| Accelerates certain spacecraft during flybys || This refers to the {{w|flyby anomaly}} which is sometimes (but not always) seen when spacecraft fly close to planets and pick up more speed than expected. It's not always seen - ROSETTA had no flyby anomaly when it swooped extremely close to Mars. || It could be an unpredicted quirk of gravity and relativity... or it could be experimental error.<br />
|-<br />
| Superluminally smooths anisotropies in early universe (but adds faint polarization for BICEP3 to find) || The CMB (Cosmic Microwave Background) is incredibly uniform. In fact it is so uniform that the conclusion is that these areas must have been in contact at some time in the early universe. But with the age of the universe, even traveling at the speed of light, opposite sides never touch. The explanation usually given is that the universe expanded really fast in the beginning ("inflation"). {{w|BICEP2}} is a radio telescope at the South Pole whose operators claim to have seen polarization in the CMB indicative of inflation. || As stated, inflation is the standard explanation and it holds up fairly well. Other studies haven't seen the polarization that BICEP2 has - the {{w|Planck (spacecraft)|Planck space telescope}} also suggests that BICEP2 team were looking at an unusually dusty bit of space, which could cause polarization.<br />
|-<br />
| Triggers Siberian sinkholes || Recently, several sinkholes opened up in remote parts of Siberia. The explanation is currently unknown. || While there are lots of weird theories, there's a good chance they were [http://www.independent.co.uk/news/science/mystery-of-the-siberian-holes-at-the-end-of-the-world-solved-scientists-offer-explanation-9642988.html caused by melting permafrost] (possibly due to global warming)<br />
|-<br />
| Melts ice in "{{w|Snowball Earth}}" scenario || "Snowball Earth" is the theory that the whole planet was covered in ice at some point. To melt all that ice by the greenhouse effect would require far more carbon dioxide in the atmosphere than seems plausible. However, if volcanoes were to deposit black soot on the surface of the ice, it would start absorbing heat more efficiently (in scientific terms, the Earth's {{w|albedo}} would decrease) and that would also make the planet heat up. || There's no firm evidence one way or the other for Snowball Earth.<br />
|-<br />
| Transports neutrinos faster than light, but only on certain days through one area of France || Refers to the {{w|faster-than-light neutrino anomaly}}, where it seemed that a neutrino beam from {{w|CERN}} on the France/Switzerland border to the {{w|OPERA experiment}} in Italy traveled fast than light. This result was not able to be replicated. || In the end, there was no mystery. Just a dodgy cable causing a measurement error.<br />
|-<br />
| Suppresses sigma in experiments || Sigma (σ) refers to the {{w|standard deviation}} - a mathematical measure of how much an observed value differs from the expected value. For a formal scientific discovery in particle physics, the standard is 5 sigma which means that there is about a 1 in 3.5 million chance that the results were caused by random errors (of course, they could be caused by ''systematic'' errors, such as measurement problems). Some tantalizing experiments have found interesting results at 3 or 4 sigma but either can't reach 5 sigma or {{w|Oops-Leon|are subsequently disproven}}. The fixion means that actually, these experiments ''have'' found what the experimenters wanted to find, but because of the fixion's dastardly behavior, the sigma has been artificially lowered below the proof threshold.|| N/A<br />
|}<br />
<br />
The title text is a further joke about FRBs and perytons. GUTs normally predict that all the forces we see are the different low-energy versions of a single force which can only be seen at extremely high energies (much higher than any Earth-based collider could produce). A high-energy FRB would be a {{w|gamma ray burst}} and if it came from a close enough object, would obliterate all life on Earth... and wreck the sensitive electronics at Parkes Observatory. This "high energy unification" is stated in a way reminiscent of the unification of electromagnetic and weak forces at high energies; but unlike the latter, it involves two things only "appearing" (or, in this case, not appearing) to be the same, not actually becoming the same.<br />
<br />
==Transcript==<br />
:[Caption above the panel:]<br />
:A Christmas gift for physicists:<br />
:The '''Fixion'''<br />
:A new particle that explains everything<br />
<br />
:[A chart resembling a Feynmann like-diagram is shown. It begins with a solid line coming down at the top, going a little to the left. The line continues downwards all the time, but changes direction 16 times before exiting at the bottom almost straight under the starting point. At every point where it changes direction, there is some kind of “interaction” with something outside this line. There are 19 phrases, 10 on the left and 9 on the right. 11 of these are distinct labels for points on the line as 14 gray curved arrows points between these 11 phrases to specific points on the line. Three of the phrases on the left has two arrows pointing to two different, but close, parts of the line. The main central line is solid all the way, except at the very bottom, where it “disappears” inside a hole only to “reappear” later from a similar hole. Between these two holes the line is dotted. The lines going away (or to) the main line can be straight and solid, straight and dotted, wavy lines (with different waviness), even looking like a spiral. Two straight solid lines ends up at two space probes, and finally the last two straight solid lines coming in (and out) on either side of the “hole” in the line has arrow pointing in and out. Below the phrases will be listed in reading order, taking one on each side alternatingly. Above each is described if there are any arrow and, if there are, what they points at.]<br />
<br />
:[Left: Arrow pointing to the very first part of the main line:]<br />
:Main component of dark matter<br />
<br />
:[Right: Arrow pointing to the very first part of the main line, but below the previous arrow:]<br />
:Confines quarks and gluons<br />
<br />
:[Left: Arrow points to the first solid line going left and upwards:]<br />
:Neutralizes monopoles<br />
<br />
:[Right: No arrow:]<br />
:Suppresses antimatter in early universe<br />
<br />
:[Left: Two arrows points to two dotted lines going out left and downwards below the first solid line:]<br />
:Spontaneously emits dark energy<br />
<br />
:[Right: Arrow pointing to several lines going almost parallel with the main line. The first line closest to the arrow is not connected with the main line. It bends closer to the other lines in the middle. The next line is connected to the main line, and is thus actually two lines going in to the main line. The same goes for the inner line, where there is some distance between the entry and exit, as the middle of these three lines connect to the main line in between. In principle there are four lines going in/out and one not connected, but it looks like three lines:]<br />
:Mediates proton decay but then hides it<br />
<br />
:[Left: One arrow points to the first wavy line (7 peaks) coming out and up towards the dotted lines above. A second arrow points further down the main line where there are three more wavy lines coming out, but to the right, they are all of the same length and go almost straight right, only a little down. The first has as short a wave length as the line above to the left, but as it is shorter it only has 6 peaks. Then the wavelength decreases to a very long one for the last, 5 peaks and then 3 peaks. The arrow points almost where the middle wavy line exits the main line:]<br />
:Introduces dispersion in perytons from kitchen microwaves, explaining fast radio bursts<br />
<br />
:[Right: An arrow point to the part of the main line between the three parallel lines and the first wavy line:]<br />
:Broken symmetry causes ϴ=0, explaining unobserved neutron dipole moment<br />
<br />
:[Left: No arrow:]<br />
:Causes alpha effect<br />
<br />
:[Right: No arrow, but right next to the middle of the three wavy line:]<br />
:Covers naked singularities<br />
<br />
:[Left: An arrow points to a corkscrew line going upwards to the left:]<br />
:Intercepts certain gravitational waves before they're observed.<br />
<br />
:[Right: No arrow, but right next to the bottom of the three wavy line:]<br />
:Causes coronal heating<br />
<br />
:[Left: No arrow:]<br />
:Higgs-ish<br />
<br />
:[Right: A long arrow point to the point of the main line just below the line pointing to the bottom (and left) of the space probes:]<br />
:Superluminally smooths anisotropies in early universe (but adds faint polarization for BICEP3 to find)<br />
<br />
:[Left: One arrows point towards the point on the main lines where a solid line goes to the right and up and another arrow points on another solid line going away from the main line towards left and down. At the end of both lines are drawn space probes with sat4elie dish and solar panels:]<br />
:Accelerates certain spacecraft during flybys<br />
<br />
:[Right: No arrow, but right next to the solid line with an arrow going into the main line just before the first hole where the main line disappears and becomes dotted:]<br />
:Triggers Siberian sinkholes<br />
<br />
:[Left: No arrow:]<br />
:Melts ice in "Snowball Earth" scenario<br />
<br />
:[Right: Arrow points to the dotted part of the main line between the two holes:]<br />
:Transports neutrinos faster than light, but only on certain days through one area of France<br />
<br />
:[Left: No arrow but the last solid line, with an arrow pointing left, that is going away from the main line, point almost directly at it:]<br />
:Suppresses sigma in experiments<br />
<br />
{{comic discussion}}<br />
<br />
[[Category:Christmas]]<br />
[[Category:Charts]]<br />
[[Category:Science]]<br />
[[Category:Physics]]<br />
[[Category:Space]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=1621:_Fixion&diff=1077561621: Fixion2015-12-25T06:20:45Z<p>108.162.216.49: </p>
<hr />
<div>{{comic<br />
| number = 1621<br />
| date = December 25, 2015<br />
| title = Fixion<br />
| image = fixion.png<br />
| titletext = My theory predicts that, at high enough energies, FRBs and perytons become indistinguishable because the detector burns out.<br />
}}<br />
<br />
==Explanation==<br />
[This explanation is very incomplete. It is a small and terrible draft, only listing some immediate things I have noticed. This article should be structured as: General idea, table of explanations for each property.]<br />
<br />
In physics, there are still many big questions and mysteries. There are many phenomena which don't seem to fit, and we don't know how to explain yet. The "fixion" is satirically presented as a particle which acts as a [https://www.tvtropes.org/pmwiki/pmwiki.php/Main/DeusExMachina Deus Ex Machina] which solves all of these mysteries without any serious fundamental reasons.<br />
<br />
Suppresses antimatter in early universe: The universe today is made almost entirely of matter. Antimatter and matter are identical, except that the charges are opposite, and that they annihilate when they come in contact with each other. So why is the universe made of matter? Why didn't the universe have equal amounts of both, and if it did, why didn't it annihilate itself immediately? This is a big question in physics today. Of course, the fixion explains this.<br />
<br />
Transports neutrinos faster than light, but only on certain days through one area of France: Refers to the "superluminal neutrino" experiment, where it seemed that a neutrino traveled faster than light. This result was not able to be replicated.<br />
<br />
"Mediates proton decay,but then hides it." Many GUTs (grand unified theories) predict that protons will decay, but experiments have shown the proton to have a half life of at least the age of the universe. <br />
<br />
"Causes coronal heating." For some reason the outer layer of the sun (the corona) is hotter than most reasonable theories predict. <br />
<br />
"Neutralizes monopoles." Some string theories predicts the existence of magnetic monopoles, which have never been observed. <br />
<br />
"Intercepts certain gravitational waves before they're observed." LIGO has yet to detect any gravitational waves, though this is probably just due to the low probability of events that would be detectable. Only extreme events like binary black hole mergers are detectable with the current setup. The proposed LISA spacecraft will be able to see things like orbiting black holes and neutron stars. <br />
<br />
"Superluminally smooths anistrophies in early universe (but adds faint polarization for bicep3 to find)." The CMB (Cosmic Microwave Background) is incredibly uniform. In fact it is so uniform that the conclusion is that these areas must have been in contact at some time in the early universe. But with the age of the universe, even traveling at the speed of light, opposite sides never touch. The explanation usually given is that the universe expanded really fast in the beginning. (Called inflation)<br />
The second part refers to the detection of polarization of the CMB by bicep3 that was first used as evidence for inflation,until the Planck telescope showed that they were looking at a region with a lot of dust,which could have caused the polarization as well. <br />
<br />
<br />
==Transcript==<br />
{{incomplete transcript}}<br />
<br />
{{comic discussion}}</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=1575:_Footprints&diff=1015821575: Footprints2015-09-11T22:45:45Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 1575<br />
| date = September 9, 2015<br />
| title = Footprints<br />
| image = footprints.png<br />
| titletext = "There's one set of foot-p's cause I was totes carrying you, bro!" said Jesus seconds before I punched him.<br />
}}<br />
<br />
==Explanation==<br />
<br />
The comic is a satirical graphical representation of the inspirational Christian poem "{{w|Footprints (poem)|Footprints}}," which has been recounted in many versions and is of disputed authorship. <br />
<br />
The basic idea of the poem is that the narrator looks back at scenes of his life and sees two sets of footprints, his and those of Jesus. During the most difficult times of his life, the narrator sees only one set of footprints and assumes that Jesus had left him during those times. In the climax of the poem, Jesus responds to the narrator that he saw only one set of footprints during the most difficult times of his life because Jesus was carrying him during those times. <br />
<br />
The poem is seen by many as overly sentimental and is thus ripe for parody of this kind. The graph mockingly illustrates various times when Jesus or the narrator left the scene, or otherwise gives various reasons why the number of footprints may have been other than two.<br />
<br />
"Ducklings {{w|Imprinting (psychology)|imprinted}} on Jesus and followed Him around" is a reference to {{w|Konrad Lorenz}}'s experiments. Three ducklings followed Jesus and the narrator.<br />
<br />
"Jesus disappeared for an evening each time a new ''{{w|The Twilight Saga (film series)|Twilight}}'' movie came out" probably means that Jesus went to see the movie and left the narrator alone.<br />
<br />
"Got lost and followed our own footprints" may be a reference to "{{w|Winnie-the-Pooh}}" (1926), in which the titular bear and his friend try and hunt a "Woozle" by its footprints, actually following their own round and round a bush, which also seems slightly childish for Jesus as traditionally portrayed. An alternate explanation is that they came to a dead end, and had to double back.<br />
<br />
"Rode around with Jesus in captured {{w|Walker (Star_Wars)#All_Terrain_Scout_Transport_.28AT-ST.29|AT-ST}}" is a reference to a two-legged combat "walker" from Star Wars. The implication is that Jesus would have participated in forcibly taking a war machine, which appears somewhat out of character. <br />
<br />
The reference at the end to Jesus drowning in a patch of quicksand, and then the narrator simply going home, again subverts the poem's earnestness. "Going home" may be a reference to dying, implying that the narrator died without Christ, or that the narrator and Christ were not traveling anymore.<br />
<br />
The title text continues the parody by imagining that Jesus delivers the poem's climactic lines in stereotypical {{w|California English|"surfer dude"}} speak, a dialect perceived by many to be obnoxious. The reference to punching Jesus is possibly another reference to the poem's perceived excessive sentimentality. Another interpretation is that the narrator, like many people, dislikes usage of this lingo and punched Jesus as a result of this hatred.<br />
<br />
"There's one set of foot-p's cause I was totes carrying you, bro!" can be translated into normal English as "There's one set of footprints because I was definitely carrying you, brother!".<br />
<br />
An alternate explanation of some of the oddities of the strip is that "Jesus" is not Jesus Christ, but some guy merely ''named'' Jesus, as is common in some Latin American countries.<br />
<br />
==Transcript==<br />
{{incomplete transcript}}<br />
<br />
A graph with time on the x-axis and numbers 1 through 5 on the y axis, labeled "Sets of footprints". A single red line runs through from left to right, showing different values at different times. Until the very end, the line always returns to the value 2, signifying two sets of footprints in the sand.<br />
<br />
* The line starts at the value 2, then dips twice to the value 1. The two troughs are labeled, "Jesus carried me".<br />
* The line then dips once again to the value 1. The trough is labeled, "I carried Jesus".<br />
* The line rises to 3 briefly, and is labeled, "Who was that guy?"<br />
* The line rises to 5 sharply, and then falls in a sharp staircase pattern, labeled "Ducklings imprinted on Jesus and followed him around".<br />
* The line rises to 4, labeled "Got lost and followed our own footprints".<br />
* The line dips for very short periods five times to the value 1. The troughs are labeled, "Jesus disappeared for an evening each time a new <em>Twilight</em> movie came out". The first dip is between "I carried Jesus" and "Who was that guy?", the second between "Who was that guy?" and "Duckings imprinted on Jesus..." and the final three are all between the "Ducklings imprinted on Jesus..." and "Got lost and followed our own footprints".<br />
* The line dips to 1, labeled "Rode around with Jesus in captured AT-ST"<br />
* The line dips and stays level at 1, labeled "Hit quicksand patch. Jesus didn't make it :("<br />
* The line dips to zero at the end, and is labeled "Went home".<br />
<br />
{{comic discussion}}<br />
<br />
[[Category:Religion]]<br />
[[Category:Language]]<br />
[[Category:Charts]]<br />
[[Category:Animals]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=Talk:1567:_Kitchen_Tips&diff=100323Talk:1567: Kitchen Tips2015-08-26T04:26:16Z<p>108.162.216.49: </p>
<hr />
<div>Does the title text refer to Cueball never ripping a sheet of toilet paper off, just putting the end of the roll in the toilet and flushing, making it unroll? [[User:Thomasa88|Thomasa88]] ([[User talk:Thomasa88|talk]]) 05:16, 21 August 2015 (UTC)<br />
<br />
:-Not quite, I think. I got the impression that cueball wiped with the ''whole roll,'' then simply shoved the entire thing down the toilet. [[Special:Contributions/199.27.128.72|199.27.128.72]] 05:49, 21 August 2015 (UTC)<br />
:: That option didn't even occur to me. In my defence, it just wasn't where the comic panels seemed to be heading. [[Special:Contributions/108.162.249.155|108.162.249.155]] 23:25, 22 August 2015 (UTC)<br />
<br />
Is Cueball really hosting a show here? I would think of this comic as a series of commercials or a vlog series rather than a TV show. Just my opinion. [[Special:Contributions/199.27.133.156|199.27.133.156]] 05:37, 21 August 2015 (UTC)<br />
:Maybe it's also meant to mock the so-called kitchen-hacks articles. [[Special:Contributions/108.162.225.56|108.162.225.56]] 07:01, 21 August 2015 (UTC)<br />
:I'm pretty sure it's aimed at [such-and-such]-hack listicles, articles, and videos. [[Special:Contributions/173.245.54.96|173.245.54.96]] 12:40, 21 August 2015 (UTC)<br />
<br />
The implication is that the the first tip: "If you want to know the temperature of something, use a thermometer designed to measure its temperature", is as obvious as the other four ridiculous 'tips'.[[User:Zeimusu|Zeimusu]] ([[User talk:Zeimusu|talk]]) 07:42, 21 August 2015 (UTC)<br />
<br />
:Zeimusu's comment goes to what i think is the real point of this comic. I came here since i wanted to know '''''why'''''. It is a commentary on the stupidity of not using the obvious and sane methods of household activities. There are a lot of really ''odd'' tips for households, including "unspooling two ply toilet paper to have each roll last twice as long" of which the "whole roll" usage is a parody. [[User:Harodotus|Harodotus]] ([[User talk:Harodotus|talk]]) 10:45, 21 August 2015 (UTC)<br />
::I 2nd Zeimusu's comment. I think Randall is saying that meat thermometers should be used more often. I don't see how you could say each panel builds up from practical to impractical. Throwing away dishes is probably less practical that cooking directly on a stove. So it goes: Obvious tip (thermometer), Obvious tip (dishes), Obvious tip (stove), Really crazy obvious tip (hose in freezer, punchline), Further grossout title text (TP waste). I don't agree with Randall's cooking advice myself (I think a meat thermometer is bothersome, and cooking to a certain number for safety is not always the point of cooking) but if you follow his "scientific" perspective then it should be "obvious" you use a thermometer to measure internal meat temperature instead of the typical (scientifically unreliable) methods of basing it on timing or other folk wisdom indicators of meat being done.[[Special:Contributions/108.162.216.164|108.162.216.164]] 07:41, 24 August 2015 (UTC)<br />
:::Actually throwing away dishes is not less practical than cooking on a stove if you consider that paper/plastic plates, plastic cups and plastic utensils can also be purchased and thrown away after every meal. Thus, the panel can be saying not to throw away ''glassware'' or to stop buying and throwing away ''plasticware'' and instead invest in dishes that can be cleaned and reused. In a way, this panel is the bridge between the realistic and the absurd since it can be taken either way IMHO. --[[User:R0hrshach|R0hrshach]] ([[User talk:R0hrshach|talk]]) 16:07, 24 August 2015 (UTC)<br />
:::: A lack of meat thermometers isn't 'stupid' and you're only 'guessing' if meat is done if you are a child or an alien with no cultural context. Recipes will say 'Until the juices run clear' or 'until pink in the middle' for a reason. Because that means it's cooked. And the result is that thermometers are just superfluous for most home cooking. They get used in commercial kitchens because in most countries you are required by law to heat meat to a set temperature before you can serve it. You don't just heat it until the temperature reaches a set point and call it cooked, you cook until it's right for the recipe, then double check it with a thermometer to comply with health regulations. When equipment is mandated by law then it shows up a lot, but I worked in kitchens for years and I never met a chef who used one at home. Why? Because knowing the temperature isn't that helpful for a lot of things. When you are cooking a big turkey or barbecuing chicken from raw then they can potentially be useful but using them correctly (which involves totally disinfecting the probe after every time you use it, and for meat with bones or different thicknesses you need to test a couple of times on each piece) is extremely time consuming. If you ever fail to properly wash the probe then you'll contaminate your cooked meat with uncooked bacteria. Also, if you only wait for the temperature to reach the legal limit and take it off you might kill the bacteria but you won't necessarily properly cook the meat. If you are cooking steak at home you really don't want to use a meat thermometer unless you want to cook it well done. Steaks are supposed to be unevenly cooked to make them tender and juicy and depending on thickness you can either ruin a steak waiting for the temperature in the middle, or serve it very rare. That's why commercial chefs cook for colour or texture then probe once before it hits the plate. Almost every other kind of meat you are going to cook until it's evenly cooked through and you don't need a thermometer to see if that's happened. Thermometers just aren't helping most of these processes. They are taking up time to tell you something you already know; they are a way to standardize something for the commercial industry that you'd never do at home, just like I'm sure you don't put out a wet floor sign when you mop at home. In theory a thermometer can make your cooking safer but our whole lives are about acceptable levels of risk. It's safer to never step out of your house, to never see the sun light or inhale unfiltered air. But just like with meat, the risks there are very small and having a happy, convenient life has to trump some abstract idea of safety at some point. You can make that call for yourself where the line is for you but don't call other people stupid for just cooking a damn steak how they like it. [[User:LostAlone|LostAlone]] ([[User talk:LostAlone|talk]]) 16:56, 24 August 2015 (UTC)<br />
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The last tip would result in the freezer door being very hard to open as it becomes jammed with ice. Try it! [[Special:Contributions/188.114.102.11|188.114.102.11]] 08:20, 21 August 2015 (UTC)<br />
: That's not the tip. The tip is that there's a better way. [[Special:Contributions/108.162.249.155|108.162.249.155]] 23:19, 22 August 2015 (UTC)<br />
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i don't find it surprising that randall doesn't read viz. http://viz.co.uk/category/top-tips/ --[[Special:Contributions/141.101.98.34|141.101.98.34]] 11:38, 21 August 2015 (UTC)<br />
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But what is his better of way of making ice? [[Special:Contributions/141.101.85.241|141.101.85.241]] 14:13, 21 August 2015 (UTC)<br />
:Presumably installing a faucet ''inside'' the freezer. {{unsigned ip|141.101.88.224}}<br />
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Can we be sure that the title text is also from Cueball? [[User:Jkrstrt|Jkrstrt]] ([[User talk:Jkrstrt|talk]]) 14:19, 21 August 2015 (UTC)<br />
<br />
My first inclination was that this was a meta joke on Randall's [http://www.explainxkcd.com/wiki/index.php/Category:My_Hobby My Hobby] series. The more I looked at it the more I think it is a progression from Practical to Impractical (Y-axis) and Plausible to Implausible (X-axis). It is both practical and plausible to check meat without a meat thermometer making the comment a true tip. However, assuming the title text is the implied ''last panel'', it is both impractical and implausible to stuff a whole roll of toilet paper down a toilet drain making the comment an imperative. --[[User:R0hrshach|R0hrshach]] ([[User talk:R0hrshach|talk]]) 15:43, 21 August 2015 (UTC)<br />
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I felt this was maybe a take on the whole "life-hacks" thing, most lifehacks are simple, and one would think, obvious. Some are a little less so, and some are just ridiculous.<br />
We've become a society which has lost it's ability to solve things by thinking, and presumably the ability to pass on basic knowledge that has been known for years, instead we need to google, luckily there are people out there who will tell us what we need to know. [[User:6328915234|6328915234]] ([[User talk:6328915234|talk]]) 15:31, 24 August 2015 (UTC)<br />
:You could have left it at the first paragraph, but no, you had to throw in a "Modern society is dumb, bluh bluh bleh" complaint. Neglecting the fact that it was the previous itineration of society that dropped the ball on passing down basic knowledge if anyone did, and apparently acting like checking Google is somehow inferior to older ways of finding out things. Go and Google how to get down off your high horse. -Pennpenn [[Special:Contributions/108.162.250.162|108.162.250.162]] 03:11, 26 August 2015 (UTC)<br />
<br />
This XKCD seems very similar to this recent episode of "The New Screensavers" in which Patrick Norton has a quick tip session about using a meat thermometer: https://youtu.be/AvN-9pOsnP8?t=1h9m47s Perhaps Randall watches the show? --[[User:Bkuhns|Bkuhns]] ([[User talk:Bkuhns|talk]]) 16:17, 25 August 2015 (UTC)<br />
<br />
Could 'easier on your plumbing' be interpreted as meaning that it's physically easier to wipe with sheets than a whole roll of paper? Just saying . . .</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=Talk:1398:_Snake_Facts&diff=72193Talk:1398: Snake Facts2014-07-23T18:12:59Z<p>108.162.216.49: Added comment.</p>
<hr />
<div>I thought the Worlds longest snake was so long that it took up enough space to be in Brazil, Peru, and Chile at the same time.~~<br />
<br />
Just a couple of thoughts: How big was the person whose digestive tract became the longest snake in the world? Also, does the grosser end of the digestive tract develop into the head of a venomous snake? [[Special:Contributions/108.162.223.29|108.162.223.29]] 06:57, 23 July 2014 (UTC)<br />
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The snake in the map shades Chile, BOLIVIA and Brazil, not Peru. [[Special:Contributions/108.162.229.125|108.162.229.125]] 08:25, 23 July 2014 (UTC)<br />
:Updated the image to match the one on xkcd.com. [[User:Nialpxe|Nialpxe]] ([[User talk:Nialpxe|talk]]) 10:00, 23 July 2014 (UTC)<br />
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<br />
Sorry, the shading (unless randell's updated after reading this) does track chili, up the Pacific Coast, across the border with Peru and veers east into Brazil.<br />
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I did wonder if 'the World's longest snake' was a reference to the south American highway, part of the pan American highway. Parts were completed in the 1950's making it 'over 60years old', and does track chili as per the 'snakes' body into Peru but the brazilian section is connected elsewhere, neatly crushing my wild theory. :-( [[Special:Contributions/141.101.99.161|141.101.99.161]] 09:39, 23 July 2014 (UTC)<br />
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The first factoid contains a common misconception about evolution, namely that species evolve ''only'' in small steps. It's entirely possible that a small mutation caused a protein that appeared in snakes' saliva to suddenly be ''very'' poisonous to the snake's prey or enemies. --[[Special:Contributions/108.162.231.98|108.162.231.98]] 11:13, 23 July 2014 (UTC)<br />
:It is possible, but unlikely. Snake venom is not a single chemical, but a mixture of several enzymes and toxins. There is a lot of variation in protein structure and enzymatic properties of the constituents of different snakes' venom, which suggests a gradual shift from one or two simpler lytic enzymes to a complex mixture. Each protein could have mutated separately, but the composition of the venom of each species almost certainly developed over a prolonged period of time. [[Special:Contributions/108.162.223.29|108.162.223.29]] 11:34, 23 July 2014 (UTC)<br />
::I don't think the implication was that every venom evolution happened in one fail swoop. I believe he was pointing out that instead of people thinking that venom evolution started with bad breath (minuscule unnoticeable changes) more likely started with a reasonably poisonous mutation that actually benefited a snakes survival.--[[User:Bmmarti3|Bmmarti3]] ([[User talk:Bmmarti3|talk]]) 12:46, 23 July 2014 (UTC)<br />
:: Exactly what Bmmarti3 said. ''"the composition of the venom of each species"'' You mean of today's snakes. This is what we would expect for animals that have been around for almost 100M years. The venom of the first poisonous snakes was certainly weaker (and probably only worked on specific targets), but that doesn't mean it was weak. --[[Special:Contributions/108.162.231.98|108.162.231.98]] 13:05, 23 July 2014 (UTC)<br />
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Is it possible that the alt-text is a reference to Cyrano de Bergeracs "L’Autre monde ou les états et empires de la Lune" ("Comical History of the States and Empires of the Moon")? I don't have a proper translation, but there's a dialogue that says that every man is born with a snake inside his belly as a punishment by god.--[[Special:Contributions/141.101.104.129|141.101.104.129]] 15:35, 23 July 2014 (UTC)<br />
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That ive seen, Randall is usually very precise in his work. getting a wrong breed for 'longest snake' seems odd to me. Could the 'longest snake' be referring to either a 'longest lived' specimen, or a geographical feature named for a snake? Or perhaps an extinct species? [[Special:Contributions/108.162.215.196|108.162.215.196]] 15:51, 23 July 2014 (UTC)<br />
::I think he's referring to an actual specimen that is pictured. [[Special:Contributions/108.162.216.49|108.162.216.49]] 18:12, 23 July 2014 (UTC)</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=428:_Starwatching&diff=72179428: Starwatching2014-07-23T13:39:45Z<p>108.162.216.49: /* Title Text */</p>
<hr />
<div>{{comic<br />
| number = 428<br />
| date = May 26, 2008<br />
| title = Starwatching<br />
| image = starwatching.png<br />
| titletext = I always figured the word 'blog' would sound *less* silly as the years went by.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Edit for accuracy and grammar, possibly other references of making fun of the word blog in comics}}<br />
It's night and [[Megan]] and [[Cueball]] lie down on the earth while looking into the sky. Cueball tells a story. Cueball says all dead bloggers are in the sky and watching them, and above of them all there is the master blogger Cory Doctorow. The story is interrupted when Cueball goes on to say that the {{w|Tag cloud}} opens and {{w|Cory Doctorow}} speaks. Megan interrupts, telling Cueball that he needs to "get out more or less, I cant decide". This means he should be away from the computer more so he doesn't connect everything to Cory Doctorow, but she is afraid that if he gets out more he would creep people out.<br />
<br />
Cueball is referencing the movie {{w|The Lion King}}. The first two panels reference a scene where the protagonist, Simba, remember how his father, Mufasa, explained the night sky by saying, 'the great kings of the past are up there'. The last panel is from a scene near the climax of the movie where a the spirit of Mufasa appears to Simba in the clouds and speaks to him. <br />
<br />
===Title Text===<br />
In the title text, Randall mentions that he feels that the word {{w|blog}}, a {{w|portmanteau}} and an {{w|Elision}} of 'web log', is a silly word, and does not sound less silly despite becoming common in usage. This is a common theme in Randall writing and comics's. Xkcd's blog is called "[http://blag.xkcd.com/ The blag of the webcomic]" in mockery of the word blog.<br />
<br />
==Transcript==<br />
:Cueball: Just look at those stars.<br />
:Cueball: My father once told me that the great bloggers of the past are up there, watching over us.<br />
:Cueball: High above the blogosphere, a gap opens in the tag clouds. Cory Doctorow's voice booms forth...<br />
:Megan: You need to get out either more or less. I can't decide.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Comics featuring real people]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=428:_Starwatching&diff=72178428: Starwatching2014-07-23T13:35:08Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 428<br />
| date = May 26, 2008<br />
| title = Starwatching<br />
| image = starwatching.png<br />
| titletext = I always figured the word 'blog' would sound *less* silly as the years went by.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Edit for accuracy and grammar, possibly other references of making fun of the word blog in comics}}<br />
It's night and [[Megan]] and [[Cueball]] lie down on the earth while looking into the sky. Cueball tells a story. Cueball says all dead bloggers are in the sky and watching them, and above of them all there is the master blogger Cory Doctorow. The story is interrupted when Cueball goes on to say that the {{w|Tag cloud}} opens and {{w|Cory Doctorow}} speaks. Megan interrupts, telling Cueball that he needs to "get out more or less, I cant decide". This means he should be away from the computer more so he doesn't connect everything to Cory Doctorow, but she is afraid that if he gets out more he would creep people out.<br />
<br />
Cueball is referencing the movie {{w|The Lion King}}. The first two panels reference a scene where the protagonist, Simba, remember how his father, Mufasa, explained the night sky by saying, 'the great kings of the past are up there'. The last panel is from a scene near the climax of the movie where a the spirit of Mufasa appears to Simba in the clouds and speaks to him. <br />
<br />
===Title Text===<br />
In the title text, Randall mentions that the word {{w|blog}} — a {{w|portmanteau}} of 'web log' — is a silly word, despite becoming common in usage. This is a common theme in Randall writing and comics's. Xkcd's blog is called "[http://blag.xkcd.com/ The blag of the webcomic]" in mockery of the word blog.<br />
<br />
==Transcript==<br />
:Cueball: Just look at those stars.<br />
:Cueball: My father once told me that the great bloggers of the past are up there, watching over us.<br />
:Cueball: High above the blogosphere, a gap opens in the tag clouds. Cory Doctorow's voice booms forth...<br />
:Megan: You need to get out either more or less. I can't decide.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Comics featuring real people]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=428:_Starwatching&diff=72177428: Starwatching2014-07-23T13:29:12Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 428<br />
| date = May 26, 2008<br />
| title = Starwatching<br />
| image = starwatching.png<br />
| titletext = I always figured the word 'blog' would sound *less* silly as the years went by.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Both interpretations could be merged.}}<br />
It's night and [[Megan]] and [[Cueball]] lie down on the earth while looking into the sky. Cueball tells a story. Cueball says all dead bloggers are in the sky and watching them, and above of them all there is the master blogger Cory Doctorow. The story is interrupted when Cueball goes on to say that the {{w|Tag cloud}} opens and {{w|Cory Doctorow}} speaks. Megan interrupts, telling Cueball that he needs to "get out more or less, I cant decide". This means he should be away from the computer more so he doesn't connect everything to Cory Doctorow, but she is afraid that if he gets out more he would creep people out.<br />
<br />
Cueball is referencing the movie {{w|The Lion King}}. The first two panels reference a scene where Simba remember how his father, Mufasa, explained the night sky by saying, 'the great kings of the past are up there'. The last panel is from a scene near the climax of the movie where a the spirit of Mufasa appears to Simba in the clouds and speaks to him. <br />
<br />
<br />
===Title Text===<br />
In the title text, Randall mentions that the word {{w|blog}} — a {{w|portmanteau}} of 'web log' — is a silly word, despite becoming common in usage. Randall's own blog is just called "[http://blag.xkcd.com/ The blag of the webcomic]".<br />
<br />
==Transcript==<br />
:Cueball: Just look at those stars.<br />
:Cueball: My father once told me that the great bloggers of the past are up there, watching over us.<br />
:Cueball: High above the blogosphere, a gap opens in the tag clouds. Cory Doctorow's voice booms forth...<br />
:Megan: You need to get out either more or less. I can't decide.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Comics featuring real people]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=428:_Starwatching&diff=72176428: Starwatching2014-07-23T13:28:42Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 428<br />
| date = May 26, 2008<br />
| title = Starwatching<br />
| image = starwatching.png<br />
| titletext = I always figured the word 'blog' would sound *less* silly as the years went by.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Both interpretations could be merged.}}<br />
It's night and [[Megan]]and [[Cueball]] lie down on the earth while looking into the sky. Cueball tells a story. Cueball says all dead bloggers are in the sky and watching them, and above of them all there is the master blogger Cory Doctorow. The story is interrupted when Cueball goes on to say that the {{w|Tag cloud}} opens and {{w|Cory Doctorow}} speaks. Megan interrupts, telling Cueball that he needs to "get out more or less, I cant decide". This means he should be away from the computer more so he doesn't connect everything to Cory Doctorow, but she is afraid that if he gets out more he would creep people out.<br />
<br />
Cueball is referencing the movie {{w|The Lion King}}. The first two panels reference a scene where Simba remember how his father, Mufasa, explained the night sky by saying, 'the great kings of the past are up there'. The last panel is from a scene near the climax of the movie where a the spirit of Mufasa appears to Simba in the clouds and speaks to him. <br />
<br />
<br />
===Title Text===<br />
In the title text, Randall mentions that the word {{w|blog}} — a {{w|portmanteau}} of 'web log' — is a silly word, despite becoming common in usage. Randall's own blog is just called "[http://blag.xkcd.com/ The blag of the webcomic]".<br />
<br />
==Transcript==<br />
:Cueball: Just look at those stars.<br />
:Cueball: My father once told me that the great bloggers of the past are up there, watching over us.<br />
:Cueball: High above the blogosphere, a gap opens in the tag clouds. Cory Doctorow's voice booms forth...<br />
:Megan: You need to get out either more or less. I can't decide.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Comics featuring real people]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=826:_Guest_Week:_Zach_Weiner_(SMBC)&diff=72174826: Guest Week: Zach Weiner (SMBC)2014-07-23T13:09:55Z<p>108.162.216.49: /* Rotunda of Uncomfortable Topics */</p>
<hr />
<div>{{comic<br />
| number = 826<br />
| date = November 26, 2010<br />
| title = Guest Week: Zach Weiner (SMBC)<br />
| before = ''Explainxkcd note: Don't try and click on this image to see the exhibits. Visit [http://www.xkcd.com/826/ the actual comic] instead''<br />
| image = guest week zach weiner smbc.png<br />
| titletext = Guest comic by Zach Weiner of Saturday Morning Breakfast Cereal. When I was stressed out, Zach gave me a talk that was really encouraging and somehow involved nanobots.<br />
}}<br />
<br />
==Explanation==<br />
<br />
This comic is drawn by a guest webcomic artist, Zack Weiner, following the theme of "Guest Week". Zach is the author of the webcomic [http://www.smbc-comics.com/ Saturday Morning Breakfast Cereal]. The [http://www.xkcd.com/826/ original comic] is interactive. It will show images of the exibits (see below) by clicking on them.<br />
<br />
The entire comic is a hypothetical "{{w|Smithsonian Museum}} of Dad-Trolling, an entire building dedicated to deceiving children for amusement." It is an common occurrence that curious children will ask simple questions about science to their parents, such as, "Daddy, why is the sky blue?" and a parent could respond, "Well Susie, the sky is blue to match your dress."<br />
<br />
===Hall Of Misunderstood Science===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about scientific topics. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_27.png|In this exhibit the marquee claims that basilisks exist, and that they live under your bed. The basilisk is a mythological reptilian monster that was described as having the ability to turn other living things to stone with its gaze. This story might be believed by children because children often imagine that a monster or a dangerous creature is hiding under the bed at night, and verifying that the basilisk is under the bed might turn the child to stone. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_26.png|In this exhibit the marquee claims that "In my day" molecules did not exist, and everything was just atoms. Molecules are chains of atoms, and therefore more complex than atoms. This story might be believed by children because old people often tell unbelievable and questionably credible "In my day" stories about how different, or in this case less complicated, things when they where younger. This story may sound no less credible then these stories to a child. Like most "In my day" stories there is at least a grain of truth. The word atom has changed its meaning over time; at one time all discovered molecules were called {{w|atomism|atoms}}, as when they were modified their properties change. Also, according to the {{w|Big Bang}} theory, there was a period billions of years ago when the universe contained no molecules, yet still contained atoms.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_25.png|In this exhibit the marquee claims that magnets are only attracted to each other when they are teenagers. This is a inside joke that the child is not in on about how there is a loss of sexual desire in adults. This story might be believed because magnets are seen as mysterious and possibly magical by children.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_24.png|In this exhibit the plaque on the statue of Jesus claims that {{w|snow}} is composed of Jesus' {{w|dandruff}}. This story might be believed because some children take the expression that {{w|rain}} is "God's tears", and this would be a logical extension.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_20.png|In this exhibit the marquee claims that the reason that there are only four components of {{w|DNA}} is because there where only four letters back then. The following letters describe the {{w|nucleotides}} that make up DNA chains: "G" {{w|guanine}}, "A" {{w|adenine}}, "T" {{w|thymine}}, and "C" {{w|cytosine}}. This story might be believed by children as DNA can be thought as an instruction set to build life. Instructions contain words, and therefore the letters G, A, T, and C can be thought of as the letters that the words in the instructions are made from.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_23.png|In this exhibit the marquee claims that you are more vulnerable to the {{w|Bogeyman|boogie man}} when you are sleeping. "The Boogie Man" is a common legend used to scare young kids; he typically hides in closets and underneath beds, and attacks sleeping children. This story might be believed by children as some believe in the boogie man.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_22.png|In this exhibit the marquee claims that water increases its size to frighten {{w|predator|predators}}. {{w|Ice}} is less dense than liquid {{w|water}}. This is an unusual property as most materials are more dense in solid form. This might be believed by a child because many animals appear to increase there size to frighten away other threatening animals. A {{w|rhinoceros}} although not traditionally a predator, would be a predator of water.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_21.png|In this exhibit the marquee claims that {{w|antimatter|anti-matter}} is composed of half ant and half matter. The prefix anti means "the opposite of", but sounds similar to the word ant. This story might be believed by children because a hyphen is often used to combine two words together with different meanings to create a word with the meaning of both. Combining the words ants and matter could produce a word meaning something composed of both ants and matter.<br />
</gallery><br />
<br />
===Regrettable Pranks: An Interactive Experience===<br />
This section holds falsehoods that a dad might use to frighten his children. Fear is often used to discourage children from disobeying their parents. It is an interactive experience, so visitors can try something for themselves, then learn the frightening fact it indicates.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_19.png|In this exhibit the sign claims that helium makes your voice higher because you are about to explode. Helium makes your voice high-pitched, because sound travels faster in helium than in oxygen, and it does not explode because it is a noble gas. This story might be used by parents to discourage children from inhaling helium. This story might regrettably convince a child that they are dying after they inhale helium.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_18.png|In this exhibit the sign claims that if your middle finger is longer than all the others, you are an alien half-breed. For almost all people the middle finger is longer than all the others. This story might be used by parents to tease their children. This story might regrettably convince a child that one of their parents is a alien, and therefore not to be trusted.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_16.png|In this exhibit the sign claims that one of the cups of {{w|Jell-O|Jello}} had a rabbit brain instead of a cherry. Cherries are a common ingredient in gelatin based deserts. One cup is missing and in the hands of the child, possibly eaten. This story might be used by parents to tease their children, or discourage them from eating more dessert. This story might regrettably convince a child that they ate the brain of a small cute fluffy animal.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_17.png|In this exhibit the sign claims that monsters will eat you if you do not make your bed. In some stories monsters specifically prey on children. This story might be used by parents to encourage children to make their beds. This story might regrettably convince a child that there are monsters under their beds and frighten them so they can not sleep.<br />
</gallery><br />
<br />
===Concessions===<br />
This area holds concession stands, which sell food. There are misleading names on each stand. The pop-outs in this section are based on jokes parents tell their children to frighten them about food.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_15.png|In this exhibit the marquee announces the name of the concession stand as KFP. The parent claims that the "P" stands for phoenix, and the operator adds "also ponies". KFP is a a parody of Kentucky Fried Chicken ({{w|KFC}}), a popular fast food chain which specializes in fried chicken. A phoenix is a mythical bird that throws it self into a fire and later rises from the ashes. This story might be believed by children because phoenixes are birds and a fried one may look similar to a chicken.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_14.png|In this exhibit the marquee announces that the concession stand sells {{w|ground beef}} and further enplanes that ground beef is beef that is found on the ground. The word ground sometimes refers to the floor other times is past tense of the word grind. This story might be believed by children because the words are spelled and pronounced the same.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_13.png|In this exhibit the marquee announces that the concession stand sells {{w|ice cream}} and claims that ice cream is really spelled eyes cream, and always composed of eyeballs. This story might be believed by children because the words "eyes cream" sounds similar to "ice cream".<br />
</gallery><br />
<br />
===Conservatory of Poorly Remembered History===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about history. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_11.png|In this exhibit the marquee claims that {{w|Genghis Khan}} achieved his victories by using dragons. Genghis Khan was a Mongolian conqueror who conquered almost all of Asia and much of Europe founding the {{w|Mongol Empire}}, and creating the then-largest continuous land empire in history. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_12.png|In this exhibit the marquee claims that the {{w|Crimean War}} was a war on crime. The Crimean War is an often forgotten Eastern European conflict between Russia and a European coalition with aims to stop Russia's expansion. This story might be believed by children because adding an "a" to a people group sometimes is used to create a country name, making Crimea sounds similar to a nation of criminals. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_10.png|In this exhibit the marquee claims that wizards where in control during {{w|The Renaissance}}. The Renaissance is a cultural movement in Europe that took place after the Dark ages. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_3.png|In this exhibit the marquee claims that {{w|Star Wars}} is actual history. Star Wars is a fantastical science fiction movie. This story might be believed by children because the movie begins "a long time ago in a galaxy far away", and some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_9.png|In this exhibit the poster claims that {{w|France}} does not exist. The adult in the comic continues to attempt to convince the children that France does not exist. This is supposed to be funny because the knowledge of France as a country is common. This may be parodying the global warming debate, a common theme in both XKCD and SMBC.<br />
</gallery><br />
<br />
===Rotunda of Uncomfortable Topics===<br />
Each exhibit is a display set up to explain uncomfortable topics that children may ask their parents about. The answers given so that the children do not ask further questions.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_8.png|In this exhibit the sign on the box covering up a couple in bed claims that naked wrestling is perfectly normal, but kids should never engage in it. "Naked wrestling" is a euphemism for sex. A parent may give this explanation if a child walks in on their parents having sex and they have to come up with an explanation on the spot, or they feel that the children are too young to know about sex.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_7.png|In this exhibit the sign over the stand claims your parents drink alcohol to prevent you from drinking it as alcohol is a poison. This is technically true, as alcohol is a toxin. A parent may give this explanation to a child who asks their parents why they drink alcohol if it is bad for you, and did not want to explain the pleasurable experience of alcohol because it might encourage children to drink.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_5.png|In this exhibit the banner claims that mommies have big tummies because storks like chubby girls. According to some childhood stories storks deliver babies. Also, there are men who prefer heavy women, these men are often called called chubby chasers. A parent may give this explanation to a child who asks why, if a stork delivers babies, there mother is changing while she is pregnant, and the parent continues to try to avoid the topic of sex.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_6.png|In this exhibit the sign claims that grandma did not die, but is going back to Saturn. Some parents tell their children that their loved ones have gone away instead of telling them the truth, their loved ones are dead. Going to Saturn "for revenge" is added for comic value. A parent may give this explanation to a avoid causing their child pain.<br />
</gallery><br />
<br />
===Miscellaneous===<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_4.png|In this exhibit the marquee claims that {{w|dinosaur|dinosaurs}} are made of bones only. The fossil record includes the imprints of the other tissues of dinosaurs including skin, nails, teeth, and feathers. This story might be believed by children because the majority of all displays of dinosaurs in museums only include bones.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_2.png|The Bathrooms have 3 doors. Clicking reveals that there is one for each gender of humans, and one for "Korgmen & Spangs". This is most likely a reference to the Marvel alien species {{w|Korg_(comics)|the Korg}}.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_1.png|In this exhibit the sign (which the children can not see) explains that the {{w|Magic Eye}} poster contains no hidden images. Magic Eye is a company that sells {{w|autostereogram}}s in books. Autostereograms contain "hidden" three-dimensional image that can only be seen by focusing one's eyes at a point other than the poster itself. This takes time and many people find it difficult or impossible to do.<br />
</gallery><br />
<br />
==Transcript==<br />
:In the spirit of xkcd I present a proposal for a new Smithsonian museum:<br />
:The Smithsonian Museum Of Dad-Trolling<br />
:An entire building dedicated to deceiving children for amusement<br />
<br />
:(Click to view exhibits!)<br />
<br />
:The top left room is 'The Hall of Misunderstood Science'. It contains six exhibits.<br />
<br />
:Exhibit: A giant basilisk looms over children.<br />
:Exhibit label: BASILISKS: Real, deadly, under your bed.<br />
<br />
:Exhibit: Four magnets hang from a square arch. A child is touching two of them together.<br />
:Text on the arch: Magnets only leap at each other when they're teenagers. Later, they lose interest.<br />
<br />
:Exhibit: A child on his dad's shoulders looks up at a looming statue of Jesus behind a lectern. There are flakes falling from Jesus onto them both.<br />
:Exhibit label: Snow is Jesus' dandruff. His scalp gets dry when it's cold.<br />
<br />
:Exhibit: A child lies asleep, while hands and a scary face reach up around the bed toward him.<br />
:Exhibit label: Sleep: Now you're vulnerable to the boogie man!<br />
<br />
:Exhibit: An ice block sits on a stand in front of pictures of a wolf and rhinoceros looking frightened.<br />
:Exhibit label: Freezing water: Expands to frighten predators.<br />
<br />
:Exhibit: An insect on a stick is orbited by a small sphere.<br />
:Exhibit label: Anti-matter: Matter that is more than 50% ants.<br />
<br />
:Exhibit: A DNA strand with the letters T, A, C, and G hanging around it.<br />
:Exhibit label: DNA only has four letters because the alphabet was smaller back then.<br />
:Dad, to child: Told you so.<br />
<br />
:Exhibit: A bunch of molecules hang from the ceiling.<br />
:Exhibit label: Molecules? In my day, we only had atoms!<br />
<br />
:The top right room is 'Regrettable Pranks: An Interactive Experience'. There are four exhibits.<br />
<br />
:Exhibit: Five balloons float tethered to a table. A child is holding a sixth balloon. The Dad looks alarmed.<br />
:Sign on exhibit: If this helium makes your voice go higher, it's because you're ten seconds from exploding.<br />
<br />
:Exhibit: An alien face is shown above an outline of several hands next to a ruler. A child holds his hand up to it.<br />
:Sign on exhibit: Measure your middle finger. If it's longer than the others, you're an alien halfbreed.<br />
<br />
:Exhibit: Three cups are on a table. A child is walking away with a fourth cup, the dad's arm around the child's shoulder.<br />
:Exhibit label: Has anyone seen my rabbit brain? It looks like a cherry, and I dropped it in a Jello cup.<br />
<br />
:Exhibit: A monstrous set of jaws open upward around a bed.<br />
:Sign on exhibit: Make your bed or monsters will know a kid lives there.<br />
<br />
:The center right room is 'Concessions'. There are three booths.<br />
<br />
:Booth: A concession stand is labeled 'KFP', and displays a KFC-style bucket. A dad and child are eating.<br />
:Dad: The "P" is for "phoenix".<br />
<br />
:Booth: A concession stand.<br />
:Sign on stand: Ground beef: Beef we found on the ground.<br />
:Dad, to child: Told you.<br />
<br />
:Booth: A stand shaped like a giant eye.<br />
:Booth label: EYES CREAM<br />
:Subtitle: How did you think it was spelled?<br />
:Sign on booth: Now with more of the goo in your eyes. Same as every other creamery.<br />
<br />
:The lower left room is 'Conservatory of Poorly Remembered History'. There are five exhibits.<br />
<br />
:Exhibit: A man is riding a dragon.<br />
:Exhibit label: Genghis Khan: victory through dragons.<br />
<br />
:Exhibit: A criminal in front of some windows.<br />
:Exhibit label: The Crimean War: The first war against crime.<br />
<br />
:Exhibit: A castle with flags hanging on it.<br />
:Exhibit label: The Renaissance<br />
:Subtitle: Long story short, the wizards were in control.<br />
<br />
:Exhibit:A man in Jedi-style robes with a fake beard.<br />
:Exhibit label: Star Wars is a documentary. No, seriously.<br />
:Dad, to children: Kids, this man is a veteran.<br />
<br />
:The lower right room is 'Rotunda of Uncomfortable Topics'. There are five exhibits.<br />
<br />
:Exhibit: A wrestling ring, with a man and woman mostly obscured by the exhibit label.<br />
:Exhibit label: Naked wrestling: perfectly normal. NEVER DO IT.<br />
<br />
:Exhibit: a figure sits at a booth in front of a bowl of food. The dad is holding a bottle.<br />
:Exhibit label: Alcohol is poison. I drink to save you from it.<br />
:Dad: You're welcome.<br />
<br />
:Exhibit: A large bird.<br />
:Exhibit label: Mommies get big tummies before babies come because the stork likes chubby girls.<br />
<br />
:Exhibit: A rocket ship.<br />
:Sign on exhibit: Grandma's not dead. She just returned to Saturn. For REVENGE.<br />
<br />
:In the areas outside the rooms, there are two more exhibits and restrooms, all clickable.<br />
<br />
:Exhibit: A dinosaur skeleton.<br />
:Exhibit label: That's right. Dinosaurs were made entirely of BONES.<br />
:Dad, to kid: If you think about it, it makes sense.<br />
<br />
:Exhibit: A large image hangs on the wall. It is a dense squiggly jumble of lines.<br />
:Dad, to kids: You gotta squint juuust right.<br />
:Sign on exhibit: Magic eye trick that doesn't actually work.<br />
<br />
:Restrooms: There are three doors, each with a sign.<br />
:First door (male logo): Men & Boys<br />
:Second door (female logo): Women & Girls<br />
:Third door (unrecognizable logo): Korgmen & Spangs<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
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[[Category:Star Wars]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=826:_Guest_Week:_Zach_Weiner_(SMBC)&diff=72093826: Guest Week: Zach Weiner (SMBC)2014-07-21T22:42:23Z<p>108.162.216.49: </p>
<hr />
<div>{{comic<br />
| number = 826<br />
| date = November 26, 2010<br />
| title = Guest Week: Zach Weiner (SMBC)<br />
| before = ''Explainxkcd note: Don't try and click on this image to see the exhibits. Visit [http://www.xkcd.com/826/ the actual comic] instead''<br />
| image = guest week zach weiner smbc.png<br />
| titletext = Guest comic by Zach Weiner of Saturday Morning Breakfast Cereal. When I was stressed out, Zach gave me a talk that was really encouraging and somehow involved nanobots.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Review for grammar}}<br />
This comic is drawn by a guest webcomic artist, Zack Weiner, following the theme of "Guest Week". Zach is the author of the webcomic [http://www.smbc-comics.com/ Saturday Morning Breakfast Cereal]. The [http://www.xkcd.com/826/ original comic] is interactive. It will show images of the exibits (see below) by clicking on them.<br />
<br />
The entire comic is a hypothetical "{{w|Smithsonian Museum}} of Dad-Trolling, an entire building dedicated to deceiving children for amusement." It is an common occurrence that curious children will ask simple questions about science to their parents, such as, "Daddy, why is the sky blue?" and a parent could respond, "Well Susie, the sky is blue to match your dress."<br />
<br />
===Hall Of Misunderstood Science===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about scientific topics. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_27.png|In this exhibit the marquee claims that basilisks exist, and that they live under your bed. The basilisk is a mythological reptilian monster that was described as having the ability to turn other living things to stone with its gaze. This story might be believed by children because children often imagine that a monster or a dangerous creature is hiding under the bed at night, and verifying that the basilisk is under the bed might turn the child to stone. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_26.png|In this exhibit the marquee claims that "In my day" molecules did not exist, and everything was just atoms. Molecules are chains of atoms, and therefore more complex than atoms. This story might be believed by children because old people often tell unbelievable and questionably credible "In my day" stories about how different, or in this case less complicated, things when they where younger. This story may sound no less credible then these stories to a child. Like most "In my day" stories there is at least a grain of truth. The word atom has changed its meaning over time; at one time all discovered molecules were called {{w|atomism|atoms}}, as when they were modified their properties change. Also, according to the {{w|Big Bang}} theory, there was a period billions of years ago when the universe contained no molecules, yet still contained atoms.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_25.png|In this exhibit the marquee claims that magnets are only attracted to each other when they are teenagers. This is a inside joke that the child is not in on about how there is a loss of sexual desire in adults. This story might be believed because magnets are seen as mysterious and possibly magical by children.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_24.png|In this exhibit the plaque on the statue of Jesus claims that {{w|snow}} is composed of Jesus' {{w|dandruff}}. This story might be believed because some children take the expression that {{w|rain}} is "God's tears", and this would be a logical extension.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_20.png|In this exhibit the marquee claims that the reason that there are only four components of {{w|DNA}} is because there where only four letters back then. The following letters describe the {{w|nucleotides}} that make up DNA chains: "G" {{w|guanine}}, "A" {{w|adenine}}, "T" {{w|thymine}}, and "C" {{w|cytosine}}. This story might be believed by children as DNA can be thought as an instruction set to build life. Instructions contain words, and therefore the letters G, A, T, and C can be thought of as the letters that the words in the instructions are made from.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_23.png|In this exhibit the marquee claims that you are more vulnerable to the {{w|Bogeyman|boogie man}} when you are sleeping. "The Boogie Man" is a common legend used to scare young kids; he typically hides in closets and underneath beds, and attacks sleeping children. This story might be believed by children as some believe in the boogie man.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_22.png|In this exhibit the marquee claims that water increases its size to frighten {{w|predator|predators}}. {{w|Ice}} is less dense than liquid {{w|water}}. This is an unusual property as most materials are more dense in solid form. This might be believed by a child because many animals appear to increase there size to frighten away other threatening animals. A {{w|rhinoceros}} although not traditionally a predator, would be a predator of water.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_21.png|In this exhibit the marquee claims that {{w|antimatter|anti-matter}} is composed of half ant and half matter. The prefix anti means "the opposite of", but sounds similar to the word ant. This story might be believed by children because a hyphen is often used to combine two words together with different meanings to create a word with the meaning of both. Combining the words ants and matter could produce a word meaning something composed of both ants and matter.<br />
</gallery><br />
<br />
===Regrettable Pranks: An Interactive Experience===<br />
This section holds falsehoods that a dad might use to frighten his children. Fear is often used to discourage children from disobeying their parents. It is an interactive experience, so visitors can try something for themselves, then learn the frightening fact it indicates.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_19.png|In this exhibit the sign claims that helium makes your voice higher because you are about to explode. Helium makes your voice high-pitched, because sound travels faster in helium than in oxygen, and it does not explode because it is a noble gas. This story might be used by parents to discourage children from inhaling helium. This story might regrettably convince a child that they are dying after they inhale helium.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_18.png|In this exhibit the sign claims that if your middle finger is longer than all the others, you are an alien half-breed. For almost all people the middle finger is longer than all the others. This story might be used by parents to tease their children. This story might regrettably convince a child that one of their parents is a alien, and therefore not to be trusted.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_16.png|In this exhibit the sign claims that one of the cups of {{w|Jell-O|Jello} had a rabbit brain instead of a cherry. Cherries are a common ingredient in gelatin based deserts. One cup is missing and in the hands of the child, possibly eaten. This story might be used by parents to tease their children, or discourage them from eating more dessert. This story might regrettably convince a child that they ate the brain of a small cute fluffy animal.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_17.png|In this exhibit the sign claims that monsters will eat you if you do not make your bed. In some stories monsters specifically prey on children. This story might be used by parents to encourage children to make their beds. This story might regrettably convince a child that there are monsters under their beds and frighten them so they can not sleep.<br />
</gallery><br />
<br />
===Concessions===<br />
This area holds concession stands, which sell food. There are misleading names on each stand. The pop-outs in this section are based on jokes parents tell their children to frighten them about food.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_15.png|In this exhibit the marquee announces the name of the concession stand as KFP. The parent claims that the "P" stands for phoenix, and the operator adds "also ponies". KFP is a a parody of Kentucky Fried Chicken ({{w|KFC}}), a popular fast food chain which specializes in fried chicken. A phoenix is a mythical bird that throws it self into a fire and later rises from the ashes. This story might be believed by children because phoenixes are birds and a fried one may look similar to a chicken.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_14.png|In this exhibit the marquee announces that the concession stand sells {{w|ground beef}} and further enplanes that ground beef is beef that is found on the ground. The word ground sometimes refers to the floor other times is past tense of the word grind. This story might be believed by children because the words are spelled and pronounced the same.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_13.png|In this exhibit the marquee announces that the concession stand sells {{w|ice cream}} and claims that ice cream is really spelled eyes cream, and always composed of eyeballs. This story might be believed by children because the words "eyes cream" sounds similar to "ice cream".<br />
</gallery><br />
<br />
===Conservatory of Poorly Remembered History===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about history. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_11.png|In this exhibit the marquee claims that {{w|Genghis Khan}} achieved his victories by using dragons. Genghis Khan was a Mongolian conqueror who conquered almost all of Asia and much of Europe founding the {{w|Mongol Empire}}, and creating the then-largest continuous land empire in history. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_12.png|In this exhibit the marquee claims that the {{w|Crimean War}} was a war on crime. The Crimean War is an often forgotten Eastern European conflict between Russia and a European coalition with aims to stop Russia's expansion. This story might be believed by children because adding an "a" to a people group sometimes is used to create a country name, making Crimea sounds similar to a nation of criminals. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_10.png|In this exhibit the marquee claims that wizards where in control during {{w|The Renaissance}}. The Renaissance is a cultural movement in Europe that took place after the Dark ages. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_3.png|In this exhibit the marquee claims that {{w|Star Wars}} is actual history. Star Wars is a fantastical science fiction movie. This story might be believed by children because the movie begins "a long time ago in a galaxy far away", and some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_9.png|In this exhibit the poster claims that {{w|France}} does not exist. The adult in the comic continues to attempt to convince the children that France does not exist. This is supposed to be funny because the knowledge of France as a country is common. This may be parodying the global warming debate, a common theme in both XKCD and SMBC.<br />
</gallery><br />
<br />
===Rotunda of Uncomfortable Topics===<br />
Each exhibit is a display set up to explain uncomfortable topics that children may ask their parents about. The answers given so that the children do not ask further questions.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_8.png|In this exhibit the sign on the box covering up the couple in bed claims that naked wrestling is perfectly normal, but kids should never engage in it. "Naked wrestling" is a common euphemism for sex, often made up on the spot. A parent may give this explanation if a child walks in on there parents having sex and they feel that the children are too young to understand<br />
<br />
File:guest_comic_week_zach_weiner_smbc_7.png|In this exhibit the sign over the stand claims your parents drink alcohol to prevent you from drinking it as alcohol is a poison. This is technically true, as alcohol is a toxin. A parent may give this explanation to a child who asks their parents why they drink alcohol if it is bad for you, and did not want to explain the pleasurable experience of alcohol because it might encourage children to drink.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_5.png|In this exhibit the banner claims that mommies have big tummies because storks like chubby girls. Some parents tell their children that storks deliver babies so that they do not have to discuss the topic of sex. A parent may give this explanation to a child who asks why, if a stork delivers babies, there mommies is changing while she is pregnant.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_6.png|In this exhibit the sign claims that grandma did not die, but is going back to Saturn. Some parents tell their children that their loved ones have gone away instead of telling them the truth, their loved ones are dead. Going to Saturn "for revenge" is added for comic value. A parent may give this explanation to a avoid causing their child pain.<br />
</gallery><br />
<br />
===Miscellaneous===<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_4.png|In this exhibit the marquee claims that {{w|dinosaur|dinosaurs}} are made of bones only. The fossil record includes the imprints of the other tissues of dinosaurs including skin, nails, teeth, and feathers. This story might be believed by children because the majority of all displays of dinosaurs in museums only include bones.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_2.png|The Bathrooms have 3 doors. Clicking reveals that there is one for each gender of humans, and one for "Korgmen & Spangs". This is most likely a reference to the Marvel alien species {{w|Korg_(comics)|the Korg}}.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_1.png|In this exhibit the sign (which the children can not see) explains that the {{w|Magic Eye}} poster contains no hidden images. Magic Eye is a company that sells {{w|autostereogram}}s in books. Aautostereograms contain "hidden" three-dimensional image that can only be seen by focusing one's eyes at a point other than the poster itself. This takes time and many people find it difficult or impossible to do.<br />
</gallery><br />
<br />
==Transcript==<br />
:In the spirit of xkcd I present a proposal for a new Smithsonian museum:<br />
:The Smithsonian Museum Of Dad-Trolling<br />
:An entire building dedicated to deceiving children for amusement<br />
<br />
:(Click to view exhibits!)<br />
<br />
:The top left room is 'The Hall of Misunderstood Science'. It contains six exhibits.<br />
<br />
:Exhibit: A giant basilisk looms over children.<br />
:Exhibit label: BASILISKS: Real, deadly, under your bed.<br />
<br />
:Exhibit: Four magnets hang from a square arch. A child is touching two of them together.<br />
:Text on the arch: Magnets only leap at each other when they're teenagers. Later, they lose interest.<br />
<br />
:Exhibit: A child on his dad's shoulders looks up at a looming statue of Jesus behind a lectern. There are flakes falling from Jesus onto them both.<br />
:Exhibit label: Snow is Jesus' dandruff. His scalp gets dry when it's cold.<br />
<br />
:Exhibit: A child lies asleep, while hands and a scary face reach up around the bed toward him.<br />
:Exhibit label: Sleep: Now you're vulnerable to the boogie man!<br />
<br />
:Exhibit: An ice block sits on a stand in front of pictures of a wolf and rhinoceros looking frightened.<br />
:Exhibit label: Freezing water: Expands to frighten predators.<br />
<br />
:Exhibit: An insect on a stick is orbited by a small sphere.<br />
:Exhibit label: Anti-matter: Matter that is more than 50% ants.<br />
<br />
:Exhibit: A DNA strand with the letters T, A, C, and G hanging around it.<br />
:Exhibit label: DNA only has four letters because the alphabet was smaller back then.<br />
:Dad, to child: Told you so.<br />
<br />
:Exhibit: A bunch of molecules hang from the ceiling.<br />
:Exhibit label: Molecules? In my day, we only had atoms!<br />
<br />
:The top right room is 'Regrettable Pranks: An Interactive Experience'. There are four exhibits.<br />
<br />
:Exhibit: Five balloons float tethered to a table. A child is holding a sixth balloon. The Dad looks alarmed.<br />
:Sign on exhibit: If this helium makes your voice go higher, it's because you're ten seconds from exploding.<br />
<br />
:Exhibit: An alien face is shown above an outline of several hands next to a ruler. A child holds his hand up to it.<br />
:Sign on exhibit: Measure your middle finger. If it's longer than the others, you're an alien halfbreed.<br />
<br />
:Exhibit: Three cups are on a table. A child is walking away with a fourth cup, the dad's arm around the child's shoulder.<br />
:Exhibit label: Has anyone seen my rabbit brain? It looks like a cherry, and I dropped it in a Jello cup.<br />
<br />
:Exhibit: A monstrous set of jaws open upward around a bed.<br />
:Sign on exhibit: Make your bed or monsters will know a kid lives there.<br />
<br />
:The center right room is 'Concessions'. There are three booths.<br />
<br />
:Booth: A concession stand is labeled 'KFP', and displays a KFC-style bucket. A dad and child are eating.<br />
:Dad: The "P" is for "phoenix".<br />
<br />
:Booth: A concession stand.<br />
:Sign on stand: Ground beef: Beef we found on the ground.<br />
:Dad, to child: Told you.<br />
<br />
:Booth: A stand shaped like a giant eye.<br />
:Booth label: EYES CREAM<br />
:Subtitle: How did you think it was spelled?<br />
:Sign on booth: Now with more of the goo in your eyes. Same as every other creamery.<br />
<br />
:The lower left room is 'Conservatory of Poorly Remembered History'. There are five exhibits.<br />
<br />
:Exhibit: A man is riding a dragon.<br />
:Exhibit label: Genghis Khan: victory through dragons.<br />
<br />
:Exhibit: A criminal in front of some windows.<br />
:Exhibit label: The Crimean War: The first war against crime.<br />
<br />
:Exhibit: A castle with flags hanging on it.<br />
:Exhibit label: The Renaissance<br />
:Subtitle: Long story short, the wizards were in control.<br />
<br />
:Exhibit:A man in Jedi-style robes with a fake beard.<br />
:Exhibit label: Star Wars is a documentary. No, seriously.<br />
:Dad, to children: Kids, this man is a veteran.<br />
<br />
:The lower right room is 'Rotunda of Uncomfortable Topics'. There are five exhibits.<br />
<br />
:Exhibit: A wrestling ring, with a man and woman mostly obscured by the exhibit label.<br />
:Exhibit label: Naked wrestling: perfectly normal. NEVER DO IT.<br />
<br />
:Exhibit: a figure sits at a booth in front of a bowl of food. The dad is holding a bottle.<br />
:Exhibit label: Alcohol is poison. I drink to save you from it.<br />
:Dad: You're welcome.<br />
<br />
:Exhibit: A large bird.<br />
:Exhibit label: Mommies get big tummies before babies come because the stork likes chubby girls.<br />
<br />
:Exhibit: A rocket ship.<br />
:Sign on exhibit: Grandma's not dead. She just returned to Saturn. For REVENGE.<br />
<br />
:In the areas outside the rooms, there are two more exhibits and restrooms, all clickable.<br />
<br />
:Exhibit: A dinosaur skeleton.<br />
:Exhibit label: That's right. Dinosaurs were made entirely of BONES.<br />
:Dad, to kid: If you think about it, it makes sense.<br />
<br />
:Exhibit: A large image hangs on the wall. It is a dense squiggly jumble of lines.<br />
:Dad, to kids: You gotta squint juuust right.<br />
:Sign on exhibit: Magic eye trick that doesn't actually work.<br />
<br />
:Restrooms: There are three doors, each with a sign.<br />
:First door (male logo): Men & Boys<br />
:Second door (female logo): Women & Girls<br />
:Third door (unrecognizable logo): Korgmen & Spangs<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
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[[Category:Comics featuring Ponytail]]<br />
[[Category:Comics featuring Black Hat]]<br />
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[[Category:Comics featuring Cory Doctorow]]<br />
[[Category:Comics featuring real people]]<br />
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[[Category:Guest Week]]<br />
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[[Category:Dinosaurs]]<br />
[[Category:LOTR]]<br />
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[[Category:Science]]<br />
[[Category:Star Wars]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=826:_Guest_Week:_Zach_Weiner_(SMBC)&diff=72067826: Guest Week: Zach Weiner (SMBC)2014-07-21T14:40:34Z<p>108.162.216.49: /* Hall Of Misunderstood Science */</p>
<hr />
<div>{{comic<br />
| number = 826<br />
| date = November 26, 2010<br />
| title = Guest Week: Zach Weiner (SMBC)<br />
| before = ''Explainxkcd note: Don't try and click on this image to see the exhibits. Visit [http://www.xkcd.com/826/ the actual comic] instead''<br />
| image = guest week zach weiner smbc.png<br />
| titletext = Guest comic by Zach Weiner of Saturday Morning Breakfast Cereal. When I was stressed out, Zach gave me a talk that was really encouraging and somehow involved nanobots.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Review for grammar}}<br />
This comic is drawn by a guest webcomic artist, Zack Weiner, following the theme of "Guest Week". Zach is the author of the webcomic [http://www.smbc-comics.com/ Saturday Morning Breakfast Cereal]. The [http://www.xkcd.com/826/ original comic] is interactive. It will show images of the exibits (see below) by clicking on them.<br />
<br />
The entire comic is a hypothetical "{{w|Smithsonian Museum}} of Dad-Trolling, an entire building dedicated to deceiving children for amusement." It is an common occurrence that curious children will ask simple questions about science to their parents, such as, "Daddy, why is the sky blue?" and a parent could respond, "Well Susie, the sky is blue to match your dress."<br />
<br />
===Hall Of Misunderstood Science===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about scientific topics. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_27.png|In this exhibit the marquee claims that basilisks exist, and that they live under your bed. The basilisk is a mythological reptilian monster that was described as having the ability to turn other living things to stone with its gaze. This story might be believed by children because children often imagine that a monster or a dangerous creature is hiding under the bed at night, and verifying that the basilisk is under the bed might turn the child to stone. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_26.png|In this exhibit the marquee claims that "In my day" molecules did not exist, and everything was just atoms. Molecules are chains of atoms, and therefore more complex than atoms. This story might be believed by children because old people often tell unbelievable and questionably credible "In my day" stories about how different, or in this case less complicated, things when they where younger. This story may sound no less credible then these stories to a child. Like most "In my day" stories there is at least a grain of truth. The word atom has changed its meaning over time; at one time all discovered molecules were called {{w|atomism|atoms}}, as when they were modified their properties change. Also, according to the {{w|Big Bang}} theory, there was a period billions of years ago when the universe contained no molecules, yet still contained atoms.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_25.png|In this exhibit the marquee claims that magnets are only attracted to each other when they are teenagers. This is a inside joke that the child is not in on about how there is a loss of sexual desire in adults. This story might be believed because magnets are seen as mysterious and possibly magical by children.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_24.png|In this exhibit the plaque on the statue of Jesus claims that {{w|snow}} is composed of Jesus' {{w|dandruff}}. This story might be believed because some children take the expression that {{w|rain}} is "God's tears", and this would be a logical extension.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_20.png|In this exhibit the marquee claims that the reason that there are only four components of {{w|DNA}} is because there where only four letters back then. The following letters describe the {{w|nucleotides}} that make up DNA chains: "G" {{w|guanine}}, "A" {{w|adenine}}, "T" {{w|thymine}}, and "C" {{w|cytosine}}. This story might be believed by children as DNA can be thought as an instruction set to build life. Instructions contain words, and therefore the letters G, A, T, and C can be thought of as the letters that the words in the instructions are made from.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_23.png|In this exhibit the marquee claims that you are more vulnerable to the {{w|Bogeyman|boogie man}} when you are sleeping. "The Boogie Man" is a common legend used to scare young kids; he typically hides in closets and underneath beds, and attacks sleeping children. This story might be believed by children as some believe in the boogie man.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_22.png|In this exhibit the marquee claims that water increases its size to frighten {{w|predator|predators}}. {{w|Ice}} is less dense than liquid {{w|water}}. This is an unusual property as most materials are more dense in solid form. This might be believed by a child because many animals appear to increase there size to frighten away other threatening animals. A {{w|rhinoceros}} although not traditionally a predator, would be a predator of water.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_21.png|In this exhibit the marquee claims that {{w|antimatter|anti-matter}} is composed of half ant and half matter. The prefix anti means "the opposite of", but sounds similar to the word ant. This story might be believed by children because a hyphen is often used to combine two words together with different meanings to create a word with the meaning of both. Combining the words ants and matter could produce a word meaning something composed of both ants and matter.<br />
</gallery><br />
<br />
===Regrettable Pranks: An Interactive Experience===<br />
This section holds falsehoods that a dad might use to frighten his children. Fear is often used to discourage children from disobeying their parents. It is an interactive experience, so visitors can try something for themselves, then learn the frightening fact it indicates.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_19.png|In this exhibit the sign claims that helium makes your voice higher because you are about to explode. Helium makes your voice high-pitched, because sound travels faster in helium than in oxygen, and it does not explode because it is a noble gas. This story might be used by parents to discourage children from inhaling helium. This story might regrettably convince a child that they are dying after they inhale helium.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_18.png|In this exhibit the sign claims that if your middle finger is longer than all the others, you are an alien half-breed. For almost all people the middle finger is longer than all the others. This story might be used by parents to tease their children. This story might regrettably convince a child that one of their parents is a alien, and therefore not to be trusted.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_16.png|In this exhibit the sign claims that one of the cups of {{w|Jell-O|Jello} had a rabbit brain instead of a cherry. Cherries are a common ingredient in gelatin based deserts. One cup is missing and in the hands of the child, possibly eaten. This story might be used by parents to tease their children, or discourage them from eating more dessert. This story might regrettably convince a child that they ate the brain of a small cute fluffy animal.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_17.png|In this exhibit the sign claims that monsters will eat you if you do not make your bed. In some stories monsters specifically prey on children. This story might be used by parents to encourage children to make their beds. This story might regrettably convince a child that there are monsters under their beds and frighten them so they can not sleep.<br />
</gallery><br />
<br />
===Concessions===<br />
This area holds concession stands, which sell food. There are misleading names on each stand. The pop-outs in this section are based on jokes parents tell there children to frighten them about food.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_15.png|In this exhibit the marquee announces the name of the concession stand as KFP. The parent claims that the "P" stands for phoenix, and the operator adds "also ponies". KFP is a a parody of Kentucky Fried Chicken ({{w|KFC}}), a popular fast food chain which specializes in fried chicken. A phoenix is a mythical bird that throws it self into a fire and later rises from the ashes. This story might be believed by children because phoenixes are birds and a fried one may look similar to a chicken.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_14.png|In this exhibit the marquee announces that the concession stand sells {{w|ground beef}} and further enplanes that ground beef is beef that is found on the ground. The word ground sometimes refers to the floor other times is past tense of the word grind. This story might be believed by children because the words are spelled and pronounced the same.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_13.png|In this exhibit the marquee announces that the concession stand sells {{w|ice cream}} and claims that ice cream is really spelled eyes cream, and always composed of eyeballs. This story might be believed by children because the words "eyes cream" sounds similar to "ice cream".<br />
</gallery><br />
<br />
===Conservatory of Poorly Remembered History===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about history. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_11.png|In this exhibit the marquee claims that {{w|Genghis Khan}} achieved his victories by using dragons. Genghis Khan was a Mongolian conqueror who conquered almost all of Asia and much of Europe founding the {{w|Mongol Empire}}, and creating the then-largest continuous land empire in history. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_12.png|In this exhibit the marquee claims that the {{w|Crimean War}} was a war on crime. The Crimean War is an often forgotten Eastern European conflict between Russia and a European coalition with aims to stop Russia's expansion. This story might be believed by children because adding an "a" to a people group sometimes is used to create a country name, making Crimea sounds similar to a nation of criminals. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_10.png|In this exhibit the marquee claims that wizards where in control during {{w|The Renaissance}}. The Renaissance is a cultural movement in Europe that took place after the Dark ages. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_3.png|In this exhibit the marquee claims that {{w|Star Wars}} is actual history. {{w|The Renaissance}}. Star Wars is a fantastical science fiction movie. This story might be believed by children because the movie begins "a long time ago in a galaxy far away", and some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_9.png|In this exhibit the poster claims that {{w|France}} does not exist. The adult in the comic continues to attempt to convince the children that France does not exist. This is supposed to be funny because the knowledge of France as a country is common. This may be parodying the global warming debate, a common theme in both XKCD and SMBC.<br />
</gallery><br />
<br />
===Rotunda of Uncomfortable Topics===<br />
Each exhibit is a display set up to explain uncomfortable topics that children may ask their parents about. The answers given so that the children do not ask further questions.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_8.png|In this exhibit the sign on the box covering up the couple in bed claims that naked wrestling is perfectly normal, but kids should never engage in it. "Naked wrestling" is a common euphemism for sex. A parent may give this explanation if a child walks in on there parents having sex and they feel that the children are too young to understand<br />
<br />
File:guest_comic_week_zach_weiner_smbc_7.png|In this exhibit the sign over the stand claims your parents drink alcohol to prevent you from drinking it as alcohol is a poison. Alcohol is a toxin. A parent may give this explanation to a child who asks there parents why they drink any alcohol if it is bad for you, and did not want to explain the pleasurable experience of alcohol because it might encourage children to drink.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_5.png|In this exhibit the banner claims that mommies have big tummies because storks like chubby girls. Some parents tell there children that storks deliver babies so that they do not have to discuss the topic of sex. A parent may give this explanation to a child who asks why, if a stork delivers babies, there mommies is changing while she is pregnant.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_6.png|In this exhibit the sign claims that grandma did not die, but is going back to Saturn. Some parents tell there children that there loved ones have gone away, instead of telling them the truth that they are dead. Going to Saturn for revenge is added for comic value. A parent may give this explanation to who asks where there loved one is, as telling the child that the loved one is dead may cause pain to both the child and the parent.<br />
</gallery><br />
<br />
===Miscellaneous===<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_4.png|In this exhibit the marquee claims that {{w|dinosaur|dinosaurs}} are made of bones only. The fossil record includes the imprints of the other tissues of dinosaurs including skin, nails, teeth, and feathers. This story might be believed by children because the majority of all displays of dinosaurs in museums only include bones.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_2.png|The Bathrooms have 3 doors. Clicking reveals that there is one for each gender of humans, and one for "Korgmen & Spangs". This is most likely a reference to the Marvel alien species {{w|Korg_(comics)|the Korg}}.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_1.png|In this exhibit the sign (which the children can not see) explains that the {{w|autostereogram|Magic eye}} poster that the children are staring at contains no hidden images. These pictures contain hidden 3D images. To see these images you have to look in front of or behind the image. This takes time and many people find it difficult or impossible to do.<br />
</gallery><br />
<br />
==Transcript==<br />
:In the spirit of xkcd I present a proposal for a new Smithsonian museum:<br />
:The Smithsonian Museum Of Dad-Trolling<br />
:An entire building dedicated to deceiving children for amusement<br />
<br />
:(Click to view exhibits!)<br />
<br />
:The top left room is 'The Hall of Misunderstood Science'. It contains six exhibits.<br />
<br />
:Exhibit: A giant basilisk looms over children.<br />
:Exhibit label: BASILISKS: Real, deadly, under your bed.<br />
<br />
:Exhibit: Four magnets hang from a square arch. A child is touching two of them together.<br />
:Text on the arch: Magnets only leap at each other when they're teenagers. Later, they lose interest.<br />
<br />
:Exhibit: A child on his dad's shoulders looks up at a looming statue of Jesus behind a lectern. There are flakes falling from Jesus onto them both.<br />
:Exhibit label: Snow is Jesus' dandruff. His scalp gets dry when it's cold.<br />
<br />
:Exhibit: A child lies asleep, while hands and a scary face reach up around the bed toward him.<br />
:Exhibit label: Sleep: Now you're vulnerable to the boogie man!<br />
<br />
:Exhibit: An ice block sits on a stand in front of pictures of a wolf and rhinoceros looking frightened.<br />
:Exhibit label: Freezing water: Expands to frighten predators.<br />
<br />
:Exhibit: An insect on a stick is orbited by a small sphere.<br />
:Exhibit label: Anti-matter: Matter that is more than 50% ants.<br />
<br />
:Exhibit: A DNA strand with the letters T, A, C, and G hanging around it.<br />
:Exhibit label: DNA only has four letters because the alphabet was smaller back then.<br />
:Dad, to child: Told you so.<br />
<br />
:Exhibit: A bunch of molecules hang from the ceiling.<br />
:Exhibit label: Molecules? In my day, we only had atoms!<br />
<br />
:The top right room is 'Regrettable Pranks: An Interactive Experience'. There are four exhibits.<br />
<br />
:Exhibit: Five balloons float tethered to a table. A child is holding a sixth balloon. The Dad looks alarmed.<br />
:Sign on exhibit: If this helium makes your voice go higher, it's because you're ten seconds from exploding.<br />
<br />
:Exhibit: An alien face is shown above an outline of several hands next to a ruler. A child holds his hand up to it.<br />
:Sign on exhibit: Measure your middle finger. If it's longer than the others, you're an alien halfbreed.<br />
<br />
:Exhibit: Three cups are on a table. A child is walking away with a fourth cup, the dad's arm around the child's shoulder.<br />
:Exhibit label: Has anyone seen my rabbit brain? It looks like a cherry, and I dropped it in a Jello cup.<br />
<br />
:Exhibit: A monstrous set of jaws open upward around a bed.<br />
:Sign on exhibit: Make your bed or monsters will know a kid lives there.<br />
<br />
:The center right room is 'Concessions'. There are three booths.<br />
<br />
:Booth: A concession stand is labeled 'KFP', and displays a KFC-style bucket. A dad and child are eating.<br />
:Dad: The "P" is for "phoenix".<br />
<br />
:Booth: A concession stand.<br />
:Sign on stand: Ground beef: Beef we found on the ground.<br />
:Dad, to child: Told you.<br />
<br />
:Booth: A stand shaped like a giant eye.<br />
:Booth label: EYES CREAM<br />
:Subtitle: How did you think it was spelled?<br />
:Sign on booth: Now with more of the goo in your eyes. Same as every other creamery.<br />
<br />
:The lower left room is 'Conservatory of Poorly Remembered History'. There are five exhibits.<br />
<br />
:Exhibit: A man is riding a dragon.<br />
:Exhibit label: Genghis Khan: victory through dragons.<br />
<br />
:Exhibit: A criminal in front of some windows.<br />
:Exhibit label: The Crimean War: The first war against crime.<br />
<br />
:Exhibit: A castle with flags hanging on it.<br />
:Exhibit label: The Renaissance<br />
:Subtitle: Long story short, the wizards were in control.<br />
<br />
:Exhibit:A man in Jedi-style robes with a fake beard.<br />
:Exhibit label: Star Wars is a documentary. No, seriously.<br />
:Dad, to children: Kids, this man is a veteran.<br />
<br />
:The lower right room is 'Rotunda of Uncomfortable Topics'. There are five exhibits.<br />
<br />
:Exhibit: A wrestling ring, with a man and woman mostly obscured by the exhibit label.<br />
:Exhibit label: Naked wrestling: perfectly normal. NEVER DO IT.<br />
<br />
:Exhibit: a figure sits at a booth in front of a bowl of food. The dad is holding a bottle.<br />
:Exhibit label: Alcohol is poison. I drink to save you from it.<br />
:Dad: You're welcome.<br />
<br />
:Exhibit: A large bird.<br />
:Exhibit label: Mommies get big tummies before babies come because the stork likes chubby girls.<br />
<br />
:Exhibit: A rocket ship.<br />
:Sign on exhibit: Grandma's not dead. She just returned to Saturn. For REVENGE.<br />
<br />
:In the areas outside the rooms, there are two more exhibits and restrooms, all clickable.<br />
<br />
:Exhibit: A dinosaur skeleton.<br />
:Exhibit label: That's right. Dinosaurs were made entirely of BONES.<br />
:Dad, to kid: If you think about it, it makes sense.<br />
<br />
:Exhibit: A large image hangs on the wall. It is a dense squiggly jumble of lines.<br />
:Dad, to kids: You gotta squint juuust right.<br />
:Sign on exhibit: Magic eye trick that doesn't actually work.<br />
<br />
:Restrooms: There are three doors, each with a sign.<br />
:First door (male logo): Men & Boys<br />
:Second door (female logo): Women & Girls<br />
:Third door (unrecognizable logo): Korgmen & Spangs<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
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[[Category:Comics featuring Beret Guy]]<br />
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[[Category:Star Wars]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=826:_Guest_Week:_Zach_Weiner_(SMBC)&diff=72066826: Guest Week: Zach Weiner (SMBC)2014-07-21T14:39:46Z<p>108.162.216.49: /* Hall Of Misunderstood Science */ Cool addition</p>
<hr />
<div>{{comic<br />
| number = 826<br />
| date = November 26, 2010<br />
| title = Guest Week: Zach Weiner (SMBC)<br />
| before = ''Explainxkcd note: Don't try and click on this image to see the exhibits. Visit [http://www.xkcd.com/826/ the actual comic] instead''<br />
| image = guest week zach weiner smbc.png<br />
| titletext = Guest comic by Zach Weiner of Saturday Morning Breakfast Cereal. When I was stressed out, Zach gave me a talk that was really encouraging and somehow involved nanobots.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Review for grammar}}<br />
This comic is drawn by a guest webcomic artist, Zack Weiner, following the theme of "Guest Week". Zach is the author of the webcomic [http://www.smbc-comics.com/ Saturday Morning Breakfast Cereal]. The [http://www.xkcd.com/826/ original comic] is interactive. It will show images of the exibits (see below) by clicking on them.<br />
<br />
The entire comic is a hypothetical "{{w|Smithsonian Museum}} of Dad-Trolling, an entire building dedicated to deceiving children for amusement." It is an common occurrence that curious children will ask simple questions about science to their parents, such as, "Daddy, why is the sky blue?" and a parent could respond, "Well Susie, the sky is blue to match your dress."<br />
<br />
===Hall Of Misunderstood Science===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about scientific topics. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_27.png|In this exhibit the marquee claims that basilisks exist, and that they live under your bed. The basilisk is a mythological reptilian monster that was described as having the ability to turn other living things to stone with its gaze. This story might be believed by children because children often imagine that a monster or a dangerous creature is hiding under the bed at night, and verifying that the basilisk is under the bed might turn the child to stone. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_26.png|In this exhibit the marquee claims that "In my day" molecules did not exist, and everything was just atoms. Molecules are chains of atoms, and therefore more complex than atoms. This story might be believed by children because old people often tell unbelievable and questionably credible "In my day" stories about how different, or in this case less complicated, things when they where younger. This story may sound no less credible then these stories to a child. Like most "In my day" stories there is at least a grain of truth. The word atom has changed its meaning over time; at one time all discovered molecules were called {{w|atomism|atoms}}, as when they were modified their properties change. Also, according to the {{{w|Big Bang}} theory, there was a period billions of years ago when the universe contained no molecules, yet still contained atoms.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_25.png|In this exhibit the marquee claims that magnets are only attracted to each other when they are teenagers. This is a inside joke that the child is not in on about how there is a loss of sexual desire in adults. This story might be believed because magnets are seen as mysterious and possibly magical by children.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_24.png|In this exhibit the plaque on the statue of Jesus claims that {{w|snow}} is composed of Jesus' {{w|dandruff}}. This story might be believed because some children take the expression that {{w|rain}} is "God's tears", and this would be a logical extension.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_20.png|In this exhibit the marquee claims that the reason that there are only four components of {{w|DNA}} is because there where only four letters back then. The following letters describe the {{w|nucleotides}} that make up DNA chains: "G" {{w|guanine}}, "A" {{w|adenine}}, "T" {{w|thymine}}, and "C" {{w|cytosine}}. This story might be believed by children as DNA can be thought as an instruction set to build life. Instructions contain words, and therefore the letters G, A, T, and C can be thought of as the letters that the words in the instructions are made from.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_23.png|In this exhibit the marquee claims that you are more vulnerable to the {{w|Bogeyman|boogie man}} when you are sleeping. "The Boogie Man" is a common legend used to scare young kids; he typically hides in closets and underneath beds, and attacks sleeping children. This story might be believed by children as some believe in the boogie man.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_22.png|In this exhibit the marquee claims that water increases its size to frighten {{w|predator|predators}}. {{w|Ice}} is less dense than liquid {{w|water}}. This is an unusual property as most materials are more dense in solid form. This might be believed by a child because many animals appear to increase there size to frighten away other threatening animals. A {{w|rhinoceros}} although not traditionally a predator, would be a predator of water.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_21.png|In this exhibit the marquee claims that {{w|antimatter|anti-matter}} is composed of half ant and half matter. The prefix anti means "the opposite of", but sounds similar to the word ant. This story might be believed by children because a hyphen is often used to combine two words together with different meanings to create a word with the meaning of both. Combining the words ants and matter could produce a word meaning something composed of both ants and matter.<br />
</gallery><br />
<br />
===Regrettable Pranks: An Interactive Experience===<br />
This section holds falsehoods that a dad might use to frighten his children. Fear is often used to discourage children from disobeying their parents. It is an interactive experience, so visitors can try something for themselves, then learn the frightening fact it indicates.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_19.png|In this exhibit the sign claims that helium makes your voice higher because you are about to explode. Helium makes your voice high-pitched, because sound travels faster in helium than in oxygen, and it does not explode because it is a noble gas. This story might be used by parents to discourage children from inhaling helium. This story might regrettably convince a child that they are dying after they inhale helium.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_18.png|In this exhibit the sign claims that if your middle finger is longer than all the others, you are an alien half-breed. For almost all people the middle finger is longer than all the others. This story might be used by parents to tease their children. This story might regrettably convince a child that one of their parents is a alien, and therefore not to be trusted.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_16.png|In this exhibit the sign claims that one of the cups of {{w|Jell-O|Jello} had a rabbit brain instead of a cherry. Cherries are a common ingredient in gelatin based deserts. One cup is missing and in the hands of the child, possibly eaten. This story might be used by parents to tease their children, or discourage them from eating more dessert. This story might regrettably convince a child that they ate the brain of a small cute fluffy animal.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_17.png|In this exhibit the sign claims that monsters will eat you if you do not make your bed. In some stories monsters specifically prey on children. This story might be used by parents to encourage children to make their beds. This story might regrettably convince a child that there are monsters under their beds and frighten them so they can not sleep.<br />
</gallery><br />
<br />
===Concessions===<br />
This area holds concession stands, which sell food. There are misleading names on each stand. The pop-outs in this section are based on jokes parents tell there children to frighten them about food.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_15.png|In this exhibit the marquee announces the name of the concession stand as KFP. The parent claims that the "P" stands for phoenix, and the operator adds "also ponies". KFP is a a parody of Kentucky Fried Chicken ({{w|KFC}}), a popular fast food chain which specializes in fried chicken. A phoenix is a mythical bird that throws it self into a fire and later rises from the ashes. This story might be believed by children because phoenixes are birds and a fried one may look similar to a chicken.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_14.png|In this exhibit the marquee announces that the concession stand sells {{w|ground beef}} and further enplanes that ground beef is beef that is found on the ground. The word ground sometimes refers to the floor other times is past tense of the word grind. This story might be believed by children because the words are spelled and pronounced the same.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_13.png|In this exhibit the marquee announces that the concession stand sells {{w|ice cream}} and claims that ice cream is really spelled eyes cream, and always composed of eyeballs. This story might be believed by children because the words "eyes cream" sounds similar to "ice cream".<br />
</gallery><br />
<br />
===Conservatory of Poorly Remembered History===<br />
Each exhibit is a display set up to reinforce the false, sarcastic, or exaggerated answers to typical questions that children may ask their parents about history. The answers given involve just enough information that the child may be satisfied with the answer and repeat it to others while maintaining the irony for adults that the answers are obviously misleading or false. These explanations may be given because the parent does not know how to explain the topic.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_11.png|In this exhibit the marquee claims that {{w|Genghis Khan}} achieved his victories by using dragons. Genghis Khan was a Mongolian conqueror who conquered almost all of Asia and much of Europe founding the {{w|Mongol Empire}}, and creating the then-largest continuous land empire in history. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_12.png|In this exhibit the marquee claims that the {{w|Crimean War}} was a war on crime. The Crimean War is an often forgotten Eastern European conflict between Russia and a European coalition with aims to stop Russia's expansion. This story might be believed by children because adding an "a" to a people group sometimes is used to create a country name, making Crimea sounds similar to a nation of criminals. <br />
<br />
File:guest_comic_week_zach_weiner_smbc_10.png|In this exhibit the marquee claims that wizards where in control during {{w|The Renaissance}}. The Renaissance is a cultural movement in Europe that took place after the Dark ages. This story might be believed by children because some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_3.png|In this exhibit the marquee claims that {{w|Star Wars}} is actual history. {{w|The Renaissance}}. Star Wars is a fantastical science fiction movie. This story might be believed by children because the movie begins "a long time ago in a galaxy far away", and some children associate magical and other fantastic elements with the past instead of fantasy.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_9.png|In this exhibit the poster claims that {{w|France}} does not exist. The adult in the comic continues to attempt to convince the children that France does not exist. This is supposed to be funny because the knowledge of France as a country is common. This may be parodying the global warming debate, a common theme in both XKCD and SMBC.<br />
</gallery><br />
<br />
===Rotunda of Uncomfortable Topics===<br />
Each exhibit is a display set up to explain uncomfortable topics that children may ask their parents about. The answers given so that the children do not ask further questions.<br />
<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_8.png|In this exhibit the sign on the box covering up the couple in bed claims that naked wrestling is perfectly normal, but kids should never engage in it. "Naked wrestling" is a common euphemism for sex. A parent may give this explanation if a child walks in on there parents having sex and they feel that the children are too young to understand<br />
<br />
File:guest_comic_week_zach_weiner_smbc_7.png|In this exhibit the sign over the stand claims your parents drink alcohol to prevent you from drinking it as alcohol is a poison. Alcohol is a toxin. A parent may give this explanation to a child who asks there parents why they drink any alcohol if it is bad for you, and did not want to explain the pleasurable experience of alcohol because it might encourage children to drink.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_5.png|In this exhibit the banner claims that mommies have big tummies because storks like chubby girls. Some parents tell there children that storks deliver babies so that they do not have to discuss the topic of sex. A parent may give this explanation to a child who asks why, if a stork delivers babies, there mommies is changing while she is pregnant.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_6.png|In this exhibit the sign claims that grandma did not die, but is going back to Saturn. Some parents tell there children that there loved ones have gone away, instead of telling them the truth that they are dead. Going to Saturn for revenge is added for comic value. A parent may give this explanation to who asks where there loved one is, as telling the child that the loved one is dead may cause pain to both the child and the parent.<br />
</gallery><br />
<br />
===Miscellaneous===<br />
<gallery class=center widths=432px heights=285px><br />
File:guest_comic_week_zach_weiner_smbc_4.png|In this exhibit the marquee claims that {{w|dinosaur|dinosaurs}} are made of bones only. The fossil record includes the imprints of the other tissues of dinosaurs including skin, nails, teeth, and feathers. This story might be believed by children because the majority of all displays of dinosaurs in museums only include bones.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_2.png|The Bathrooms have 3 doors. Clicking reveals that there is one for each gender of humans, and one for "Korgmen & Spangs". This is most likely a reference to the Marvel alien species {{w|Korg_(comics)|the Korg}}.<br />
<br />
File:guest_comic_week_zach_weiner_smbc_1.png|In this exhibit the sign (which the children can not see) explains that the {{w|autostereogram|Magic eye}} poster that the children are staring at contains no hidden images. These pictures contain hidden 3D images. To see these images you have to look in front of or behind the image. This takes time and many people find it difficult or impossible to do.<br />
</gallery><br />
<br />
==Transcript==<br />
:In the spirit of xkcd I present a proposal for a new Smithsonian museum:<br />
:The Smithsonian Museum Of Dad-Trolling<br />
:An entire building dedicated to deceiving children for amusement<br />
<br />
:(Click to view exhibits!)<br />
<br />
:The top left room is 'The Hall of Misunderstood Science'. It contains six exhibits.<br />
<br />
:Exhibit: A giant basilisk looms over children.<br />
:Exhibit label: BASILISKS: Real, deadly, under your bed.<br />
<br />
:Exhibit: Four magnets hang from a square arch. A child is touching two of them together.<br />
:Text on the arch: Magnets only leap at each other when they're teenagers. Later, they lose interest.<br />
<br />
:Exhibit: A child on his dad's shoulders looks up at a looming statue of Jesus behind a lectern. There are flakes falling from Jesus onto them both.<br />
:Exhibit label: Snow is Jesus' dandruff. His scalp gets dry when it's cold.<br />
<br />
:Exhibit: A child lies asleep, while hands and a scary face reach up around the bed toward him.<br />
:Exhibit label: Sleep: Now you're vulnerable to the boogie man!<br />
<br />
:Exhibit: An ice block sits on a stand in front of pictures of a wolf and rhinoceros looking frightened.<br />
:Exhibit label: Freezing water: Expands to frighten predators.<br />
<br />
:Exhibit: An insect on a stick is orbited by a small sphere.<br />
:Exhibit label: Anti-matter: Matter that is more than 50% ants.<br />
<br />
:Exhibit: A DNA strand with the letters T, A, C, and G hanging around it.<br />
:Exhibit label: DNA only has four letters because the alphabet was smaller back then.<br />
:Dad, to child: Told you so.<br />
<br />
:Exhibit: A bunch of molecules hang from the ceiling.<br />
:Exhibit label: Molecules? In my day, we only had atoms!<br />
<br />
:The top right room is 'Regrettable Pranks: An Interactive Experience'. There are four exhibits.<br />
<br />
:Exhibit: Five balloons float tethered to a table. A child is holding a sixth balloon. The Dad looks alarmed.<br />
:Sign on exhibit: If this helium makes your voice go higher, it's because you're ten seconds from exploding.<br />
<br />
:Exhibit: An alien face is shown above an outline of several hands next to a ruler. A child holds his hand up to it.<br />
:Sign on exhibit: Measure your middle finger. If it's longer than the others, you're an alien halfbreed.<br />
<br />
:Exhibit: Three cups are on a table. A child is walking away with a fourth cup, the dad's arm around the child's shoulder.<br />
:Exhibit label: Has anyone seen my rabbit brain? It looks like a cherry, and I dropped it in a Jello cup.<br />
<br />
:Exhibit: A monstrous set of jaws open upward around a bed.<br />
:Sign on exhibit: Make your bed or monsters will know a kid lives there.<br />
<br />
:The center right room is 'Concessions'. There are three booths.<br />
<br />
:Booth: A concession stand is labeled 'KFP', and displays a KFC-style bucket. A dad and child are eating.<br />
:Dad: The "P" is for "phoenix".<br />
<br />
:Booth: A concession stand.<br />
:Sign on stand: Ground beef: Beef we found on the ground.<br />
:Dad, to child: Told you.<br />
<br />
:Booth: A stand shaped like a giant eye.<br />
:Booth label: EYES CREAM<br />
:Subtitle: How did you think it was spelled?<br />
:Sign on booth: Now with more of the goo in your eyes. Same as every other creamery.<br />
<br />
:The lower left room is 'Conservatory of Poorly Remembered History'. There are five exhibits.<br />
<br />
:Exhibit: A man is riding a dragon.<br />
:Exhibit label: Genghis Khan: victory through dragons.<br />
<br />
:Exhibit: A criminal in front of some windows.<br />
:Exhibit label: The Crimean War: The first war against crime.<br />
<br />
:Exhibit: A castle with flags hanging on it.<br />
:Exhibit label: The Renaissance<br />
:Subtitle: Long story short, the wizards were in control.<br />
<br />
:Exhibit:A man in Jedi-style robes with a fake beard.<br />
:Exhibit label: Star Wars is a documentary. No, seriously.<br />
:Dad, to children: Kids, this man is a veteran.<br />
<br />
:The lower right room is 'Rotunda of Uncomfortable Topics'. There are five exhibits.<br />
<br />
:Exhibit: A wrestling ring, with a man and woman mostly obscured by the exhibit label.<br />
:Exhibit label: Naked wrestling: perfectly normal. NEVER DO IT.<br />
<br />
:Exhibit: a figure sits at a booth in front of a bowl of food. The dad is holding a bottle.<br />
:Exhibit label: Alcohol is poison. I drink to save you from it.<br />
:Dad: You're welcome.<br />
<br />
:Exhibit: A large bird.<br />
:Exhibit label: Mommies get big tummies before babies come because the stork likes chubby girls.<br />
<br />
:Exhibit: A rocket ship.<br />
:Sign on exhibit: Grandma's not dead. She just returned to Saturn. For REVENGE.<br />
<br />
:In the areas outside the rooms, there are two more exhibits and restrooms, all clickable.<br />
<br />
:Exhibit: A dinosaur skeleton.<br />
:Exhibit label: That's right. Dinosaurs were made entirely of BONES.<br />
:Dad, to kid: If you think about it, it makes sense.<br />
<br />
:Exhibit: A large image hangs on the wall. It is a dense squiggly jumble of lines.<br />
:Dad, to kids: You gotta squint juuust right.<br />
:Sign on exhibit: Magic eye trick that doesn't actually work.<br />
<br />
:Restrooms: There are three doors, each with a sign.<br />
:First door (male logo): Men & Boys<br />
:Second door (female logo): Women & Girls<br />
:Third door (unrecognizable logo): Korgmen & Spangs<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Comics featuring Ponytail]]<br />
[[Category:Comics featuring Black Hat]]<br />
[[Category:Comics featuring Beret Guy]]<br />
[[Category:Comics featuring White Hat]]<br />
[[Category:Comics featuring Cory Doctorow]]<br />
[[Category:Comics featuring real people]]<br />
[[Category:Comics with color]]<br />
[[Category:Ferret]]<br />
[[Category:Guest Week]]<br />
[[Category:Interactive comics]]<br />
[[Category:Dinosaurs]]<br />
[[Category:LOTR]]<br />
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[[Category:Science]]<br />
[[Category:Star Wars]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71279681: Gravity Wells2014-07-09T20:58:13Z<p>108.162.216.49: /* Planet-Moon systems */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope gives up energy, while an object traveling along a downward one gains energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy (e.g. by walking, jumping, or rocket) to reach the top of either peak that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Planet-Moon systems ====<br />
# {{w|Mercury_(planet)|Mercury}}<br />
# {{w|Venus_(planet)|Venus}}<br />
# {{w|Earth}}-{{w|Moon}}: The listed depth of the gravity well at Earth is mistakenly listed at 5 478 km (note the difference from the cutout value) and the Moon's is 288 km.<br />
# {{w|Mars}}: The listed depth of the gravity well of Mars is 1 286 km.<br />
# {{w|Jupiter}}-moon: Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}. {{w|Ganymede_(moon)|Ganymede}}, {{w|Io_(moon)|Io}}, and {{w|Europa_(moon)|Europa}}, which are moons of Jupiter, are displayed as well.<br />
# {{w|Saturn}}-moon: The diagram shows the position of the {{w|rings of Saturn}} in Saturn's gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth. {{w|Titan (moon)|Titan}}, a moon of Saturn, is displayed as well. The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
# {{w|Uranus}}: Notably absent is any "your-anus" jokes.<br />
# {{w|Neptune}}: Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== Cut outs and sketches====<br />
The following items are listed from top to bottom and left to right.<br />
<br />
* Mars-moon: The Mars cutout shows the Mars moon system, including the moons Deimos and Phobos. The depth of the gravity well is listed at 1286 km.<br />
* {{w|Deimos (moon)|Deimos}}: The gravity on Deimos, a moon of Mars, is so weak that a bike jump would be sufficient to escape its gravity.<br />
* {{w|Phobos (moon)|Phobos}}: The gravity on Phobos, a moon of Mars, is so weak that you could launch a baseball into space simply by throwing it.<br />
* Your mom-Local football team: The sketch next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The sketch implies that she has a huge gravitational pull and has sex with an entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
* Earth-Moon: The cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was very small and the {{w|Saturn V}} rocket was very large because escaping the Earth's gravity well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well. The depth of Earth's gravity well is listed correctly at 6 379 km (note the difference from the non-cutout number). The depth of the Moon's gravity well is listed at 288 km.<br />
<br />
=== How to calculate gravity wells ===<br />
The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Title text====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71278681: Gravity Wells2014-07-09T20:55:28Z<p>108.162.216.49: /* Cut outs and sketches */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope gives up energy, while an object traveling along a downward one gains energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy (e.g. by walking, jumping, or rocket) to reach the top of either peak that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Planet-Moon systems ====<br />
# {{w|Mercury_(planet)|Mercury}}<br />
# {{w|Venus_(planet)|Venus}}<br />
# {{w|Earth}}-{{w|Moon}}: The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
# {{w|Mars}}: The listed depth of the gravity well of Mars is 1286&nbsp;km.<br />
# {{w|Jupiter}}-moon: Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}. {{w|Ganymede_(moon)|Ganymede}}, {{w|Io_(moon)|Io}}, and {{w|Europa_(moon)|Europa}}, which are moons of Jupiter, are displayed as well.<br />
# {{w|Saturn}}-moon: The diagram shows the position of the {{w|rings of Saturn}} in Saturn's gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth. {{w|Titan (moon)|Titan}}, a moon of Saturn, is displayed as well. The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
# {{w|Uranus}}: Notably absent is any "your-anus" jokes.<br />
# {{w|Neptune}}: Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== Cut outs and sketches====<br />
The following items are listed from top to bottom and left to right.<br />
<br />
* Mars-moon: The Mars cutout shows the Mars moon system, including the moons Deimos and Phobos. The depth of the gravity well is listed at 1286 km.<br />
* {{w|Deimos (moon)|Deimos}}: The gravity on Deimos, a moon of Mars, is so weak that a bike jump would be sufficient to escape its gravity.<br />
* {{w|Phobos (moon)|Phobos}}: The gravity on Phobos, a moon of Mars, is so weak that you could launch a baseball into space simply by throwing it.<br />
* Your mom-Local football team: The sketch next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The sketch implies that she has a huge gravitational pull and has sex with an entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
* Earth-Moon: The cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was very small and the {{w|Saturn V}} rocket was very large because escaping the Earth's gravity well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well. The depth of Earth's gravity well is listed correctly at 6 379 km (note the difference from the non-cutout number). The depth of the Moon's gravity well is listed at 288 km.<br />
<br />
=== How to calculate gravity wells ===<br />
The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Title text====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71205681: Gravity Wells2014-07-08T21:48:20Z<p>108.162.216.49: /* Gravity assist */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak (e.g. by walking, jumping, or rocket) that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Planet-Moon systems ====<br />
# {{w|Mercury_(planet)|Mercury}}<br />
# {{w|Venus_(planet)|Venus}}<br />
# {{w|Earth}}-{{w|Moon}}: The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
# {{w|Mars}}: The listed depth of the gravity well of Mars is 1286&nbsp;km.<br />
# {{w|Jupiter}}-moon: Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}. {{w|Ganymede_(moon)|Ganymede}}, {{w|Io_(moon)|Io}}, and {{w|Europa_(moon)|Europa}}, which are moons of Jupiter, are displayed as well.<br />
# {{w|Saturn}}-moon: The diagram shows the position of the {{w|rings of Saturn}} in Saturn's gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth. {{w|Titan (moon)|Titan}}, a moon of Saturn, is displayed as well. The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
# {{w|Uranus}}: Notably absent is any "your-anus" jokes.<br />
# {{w|Neptune}}: Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== Cut outs and sketches====<br />
The following items are listed from top to bottom and left to right.<br />
<br />
* Mars: The Mars cutout shows how weak the gravity Mars's moons really are.<br />
* {{w|Deimos (moon)|Deimos}}: The gravity on Deimos, a moon of Mars, is so weak that a bike jump would be sufficient to escape its gravity.<br />
* {{w|Phobos (moon)|Phobos}}: The gravity on Phobos, a moon of Mars, is so weak that you could launch a baseball into space simply by throwing it.<br />
* Your mom-Local football team: The sketch next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The sketch implies that she has a huge gravitational pull and has sex with an entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
* Earth-Moon: The cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was very small and the {{w|Saturn V}} rocket was very large because escaping the Earth's gravity well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
=== How to calculate gravity wells ===<br />
The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Title text====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71204681: Gravity Wells2014-07-08T21:47:16Z<p>108.162.216.49: /* Cut outs and sketches */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak (e.g. by walking, jumping, or rocket) that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Planet-Moon systems ====<br />
# {{w|Mercury_(planet)|Mercury}}<br />
# {{w|Venus_(planet)|Venus}}<br />
# {{w|Earth}}-{{w|Moon}}: The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
# {{w|Mars}}: The listed depth of the gravity well of Mars is 1286&nbsp;km.<br />
# {{w|Jupiter}}-moon: Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}. {{w|Ganymede_(moon)|Ganymede}}, {{w|Io_(moon)|Io}}, and {{w|Europa_(moon)|Europa}}, which are moons of Jupiter, are displayed as well.<br />
# {{w|Saturn}}-moon: The diagram shows the position of the {{w|rings of Saturn}} in Saturn's gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth. {{w|Titan (moon)|Titan}}, a moon of Saturn, is displayed as well. The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
# {{w|Uranus}}: Notably absent is any "your-anus" jokes.<br />
# {{w|Neptune}}: Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== Cut outs and sketches====<br />
The following items are listed from top to bottom and left to right.<br />
<br />
* Mars: The Mars cutout shows how weak the gravity Mars's moons really are.<br />
* {{w|Deimos (moon)|Deimos}}: The gravity on Deimos, a moon of Mars, is so weak that a bike jump would be sufficient to escape its gravity.<br />
* {{w|Phobos (moon)|Phobos}}: The gravity on Phobos, a moon of Mars, is so weak that you could launch a baseball into space simply by throwing it.<br />
* Your mom-Local football team: The sketch next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The sketch implies that she has a huge gravitational pull and has sex with an entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
* Earth-Moon: The cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was very small and the {{w|Saturn V}} rocket was very large because escaping the Earth's gravity well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
=== How to calculate gravity wells ===<br />
The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Gravity assist====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71203681: Gravity Wells2014-07-08T21:41:46Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak (e.g. by walking, jumping, or rocket) that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Planet-Moon systems ====<br />
# {{w|Mercury_(planet)|Mercury}}<br />
# {{w|Venus_(planet)|Venus}}<br />
# {{w|Earth}}-{{w|Moon}}: The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
# {{w|Mars}}: The listed depth of the gravity well of Mars is 1286&nbsp;km.<br />
# {{w|Jupiter}}-moon: Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}. {{w|Ganymede_(moon)|Ganymede}}, {{w|Io_(moon)|Io}}, and {{w|Europa_(moon)|Europa}}, which are moons of Jupiter, are displayed as well.<br />
# {{w|Saturn}}-moon: The diagram shows the position of the {{w|rings of Saturn}} in Saturn's gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth. {{w|Titan (moon)|Titan}}, a moon of Saturn, is displayed as well. The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
# {{w|Uranus}}: Notably absent is any "your-anus" jokes.<br />
# {{w|Neptune}}: Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== Cut outs and sketches====<br />
The following items are listed from top to bottom and left to right.<br />
<br />
* Mars: The Mars cutout shows how weak the gravity Mars's moons really are.<br />
* {{w|Deimos (moon)|Deimos}}: The gravity on Deimos, a moon of Mars, is so weak that a bike jump would be sufficient to escape its gravity.<br />
* {{w|Phobos (moon)|Phobos}}: The gravity on Phobos, a moon of Mars, is so weak that you could launch a baseball into space simply by throwing it.<br />
* The sketch next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The sketch implies that she has a huge gravitational pull and has sex with an entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
* Earth-Moon: The cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was very small and the {{w|Saturn V}} rocket was very large because escaping the Earth's gravity well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
=== How to calculate gravity wells ===<br />
The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Gravity assist====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71202681: Gravity Wells2014-07-08T21:39:44Z<p>108.162.216.49: /* Cut outs and sketches */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak (e.g. by walking or jumping) that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Planet-Moon systems ====<br />
# {{w|Mercury_(planet)|Mercury}}<br />
# {{w|Venus_(planet)|Venus}}<br />
# {{w|Earth}}-{{w|Moon}}: The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
# {{w|Mars}}: The listed depth of the gravity well of Mars is 1286&nbsp;km.<br />
# {{w|Jupiter}}-moon: Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}. {{w|Ganymede_(moon)|Ganymede}}, {{w|Io_(moon)|Io}}, and {{w|Europa_(moon)|Europa}}, which are moons of Jupiter, are displayed as well.<br />
# {{w|Saturn}}-moon: The diagram shows the position of the {{w|rings of Saturn}} in Saturn's gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth. {{w|Titan (moon)|Titan}}, a moon of Saturn, is displayed as well. The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
# {{w|Uranus}}: Notably absent is any "your-anus" jokes.<br />
# {{w|Neptune}}: Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== Cut outs and sketches====<br />
The following items are listed from top to bottom and left to right.<br />
<br />
* Mars: The Mars cutout shows how weak the gravity Mars's moons really are.<br />
* {{w|Deimos (moon)|Deimos}}: The gravity on Deimos, a moon of Mars, is so weak that a bike jump would be sufficient to escape its gravity.<br />
* {{w|Phobos (moon)|Phobos}}: The gravity on Phobos, a moon of Mars, is so weak that you could launch a baseball into space simply by throwing it.<br />
* The sketch next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The sketch implies that she has a huge gravitational pull and has sex with an entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
* Earth-Moon: The cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was very small and the {{w|Saturn V}} rocket was very large because escaping the Earth's gravity well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
=== How to calculate gravity wells ===<br />
The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Gravity assist====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71201681: Gravity Wells2014-07-08T21:37:52Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak (e.g. by walking or jumping) that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Planet-Moon systems ====<br />
# {{w|Mercury_(planet)|Mercury}}<br />
# {{w|Venus_(planet)|Venus}}<br />
# {{w|Earth}}-{{w|Moon}}: The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
# {{w|Mars}}: The listed depth of the gravity well of Mars is 1286&nbsp;km.<br />
# {{w|Jupiter}}-moon: Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}. {{w|Ganymede_(moon)|Ganymede}}, {{w|Io_(moon)|Io}}, and {{w|Europa_(moon)|Europa}}, which are moons of Jupiter, are displayed as well.<br />
# {{w|Saturn}}-moon: The diagram shows the position of the {{w|rings of Saturn}} in Saturn's gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth. {{w|Titan (moon)|Titan}}, a moon of Saturn, is displayed as well. The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
# {{w|Uranus}}: Notably absent is any "your-anus" jokes.<br />
# {{w|Neptune}}: Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== Cut outs and sketches====<br />
The following items are listed from top to bottom and left to right.<br />
<br />
* Mars: The Mars cutout shows how weak the gravity Mars's moons really are.<br />
* {{w|Deimos (moon)|Deimos}}: The gravity on Deimos, a moon of Mars, is so weak that a bike jump would be sufficient to escape its gravity.<br />
* {{w|Phobos (moon)|Phobos}}: The gravity on Phobos, a moon of Mars, is so weak that you could launch a baseball into space simply by throwing it.<br />
* The sketch next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The sketch implies that she has a huge gravitational pull and has sex with an entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
* The Earth/Moon cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was very small and the {{w|Saturn V}} rocket was very large because escaping the Earth's gravity well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
=== How to calculate gravity wells ===<br />
The text near the bottom of Jupiter's gravity well explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Gravity assist====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71196681: Gravity Wells2014-07-08T18:39:02Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak (e.g. by walking or jumping) that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Inner Planets ====<br />
<br />
* {{w|Mercury_(planet)|Mercury}}<br />
<br />
* {{w|Venus_(planet)|Venus}}<br />
<br />
* {{w|Earth}} & {{w|Moon}} - The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
<br />
* {{w|Mars}} - The listed depth of the gravity well of Mars is 1286&nbsp;km<br />
<br />
==== Cut outs ====<br />
<br />
* The Mars cutout shows how weak the gravity of Mars' moons really are. {{w|Deimos (moon)|Deimos}} is so weak that a bike jump would be sufficient to escape its gravity. On {{w|Phobos (moon)|Phobos}} you could launch a baseball into space simply by throwing it.<br />
<br />
* The drawing next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The joke implies that she has a huge gravitational pull and has sex with the entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
<br />
* The Earth/Moon cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was small and the {{w|Saturn V}} rocket was much larger because escaping the Earth's well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
==== Outer Planets ====<br />
<br />
* {{w|Jupiter}} — Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}.<br />
* Jupiter's moons<br />
** {{w|Ganymede_(moon)|Ganymede}}<br />
** {{w|Io_(moon)|Io}}<br />
** {{w|Europa_(moon)|Europa}}<br />
<br />
* {{w|Saturn}} & its rings — The diagram shows the position of {{w|Rings of Saturn|Saturn's rings}} in its gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth.<br />
*Moons of Saturn<br />
** {{w|Titan (moon)|Titan}} — The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
<br />
* {{w|Uranus}} — notably absent is any "your-anus" jokes.<br />
<br />
* {{w|Neptune}} — Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
=== How to calculate gravity wells ===<br />
The text explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Gravity assist====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71195681: Gravity Wells2014-07-08T18:37:05Z<p>108.162.216.49: /* Gravity assist */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Inner Planets ====<br />
<br />
* {{w|Mercury_(planet)|Mercury}}<br />
<br />
* {{w|Venus_(planet)|Venus}}<br />
<br />
* {{w|Earth}} & {{w|Moon}} - The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
<br />
* {{w|Mars}} - The listed depth of the gravity well of Mars is 1286&nbsp;km<br />
<br />
==== Cut outs ====<br />
<br />
* The Mars cutout shows how weak the gravity of Mars' moons really are. {{w|Deimos (moon)|Deimos}} is so weak that a bike jump would be sufficient to escape its gravity. On {{w|Phobos (moon)|Phobos}} you could launch a baseball into space simply by throwing it.<br />
<br />
* The drawing next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The joke implies that she has a huge gravitational pull and has sex with the entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
<br />
* The Earth/Moon cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was small and the {{w|Saturn V}} rocket was much larger because escaping the Earth's well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
==== Outer Planets ====<br />
<br />
* {{w|Jupiter}} — Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}.<br />
* Jupiter's moons<br />
** {{w|Ganymede_(moon)|Ganymede}}<br />
** {{w|Io_(moon)|Io}}<br />
** {{w|Europa_(moon)|Europa}}<br />
<br />
* {{w|Saturn}} & its rings — The diagram shows the position of {{w|Rings of Saturn|Saturn's rings}} in its gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth.<br />
*Moons of Saturn<br />
** {{w|Titan (moon)|Titan}} — The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
<br />
* {{w|Uranus}} — notably absent is any "your-anus" jokes.<br />
<br />
* {{w|Neptune}} — Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
=== How to calculate gravity wells ===<br />
The text explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Gravity assist====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71194681: Gravity Wells2014-07-08T18:00:01Z<p>108.162.216.49: /* Slingshot */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Inner Planets ====<br />
<br />
* {{w|Mercury_(planet)|Mercury}}<br />
<br />
* {{w|Venus_(planet)|Venus}}<br />
<br />
* {{w|Earth}} & {{w|Moon}} - The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
<br />
* {{w|Mars}} - The listed depth of the gravity well of Mars is 1286&nbsp;km<br />
<br />
==== Cut outs ====<br />
<br />
* The Mars cutout shows how weak the gravity of Mars' moons really are. {{w|Deimos (moon)|Deimos}} is so weak that a bike jump would be sufficient to escape its gravity. On {{w|Phobos (moon)|Phobos}} you could launch a baseball into space simply by throwing it.<br />
<br />
* The drawing next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The joke implies that she has a huge gravitational pull and has sex with the entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
<br />
* The Earth/Moon cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was small and the {{w|Saturn V}} rocket was much larger because escaping the Earth's well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
==== Outer Planets ====<br />
<br />
* {{w|Jupiter}} — Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}.<br />
* Jupiter's moons<br />
** {{w|Ganymede_(moon)|Ganymede}}<br />
** {{w|Io_(moon)|Io}}<br />
** {{w|Europa_(moon)|Europa}}<br />
<br />
* {{w|Saturn}} & its rings — The diagram shows the position of {{w|Rings of Saturn|Saturn's rings}} in its gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth.<br />
*Moons of Saturn<br />
** {{w|Titan (moon)|Titan}} — The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
<br />
* {{w|Uranus}} — notably absent is any "your-anus" jokes.<br />
<br />
* {{w|Neptune}} — Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
=== How to calculate gravity wells ===<br />
The text explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Gravity assist====<br />
The title text indicates that the planets motion can affect the amount of energy for escape velocity. It is possible to change speed by using the planets orbital speed and gravity to gravity assist. This is know as a performing a slingshot or a {{w|Gravity assist|gravity assist}}, and is done to gain speed or to break when needed. On earth the same principle is used when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy of the earth. Launching rockets in a westward direction would require significant additional energy. Because of this most artificial satellites are flying east around the globe. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71193681: Gravity Wells2014-07-08T17:51:57Z<p>108.162.216.49: /* Slingshot */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Inner Planets ====<br />
<br />
* {{w|Mercury_(planet)|Mercury}}<br />
<br />
* {{w|Venus_(planet)|Venus}}<br />
<br />
* {{w|Earth}} & {{w|Moon}} - The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
<br />
* {{w|Mars}} - The listed depth of the gravity well of Mars is 1286&nbsp;km<br />
<br />
==== Cut outs ====<br />
<br />
* The Mars cutout shows how weak the gravity of Mars' moons really are. {{w|Deimos (moon)|Deimos}} is so weak that a bike jump would be sufficient to escape its gravity. On {{w|Phobos (moon)|Phobos}} you could launch a baseball into space simply by throwing it.<br />
<br />
* The drawing next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The joke implies that she has a huge gravitational pull and has sex with the entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
<br />
* The Earth/Moon cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was small and the {{w|Saturn V}} rocket was much larger because escaping the Earth's well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
==== Outer Planets ====<br />
<br />
* {{w|Jupiter}} — Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}.<br />
* Jupiter's moons<br />
** {{w|Ganymede_(moon)|Ganymede}}<br />
** {{w|Io_(moon)|Io}}<br />
** {{w|Europa_(moon)|Europa}}<br />
<br />
* {{w|Saturn}} & its rings — The diagram shows the position of {{w|Rings of Saturn|Saturn's rings}} in its gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth.<br />
*Moons of Saturn<br />
** {{w|Titan (moon)|Titan}} — The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
<br />
* {{w|Uranus}} — notably absent is any "your-anus" jokes.<br />
<br />
* {{w|Neptune}} — Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
=== How to calculate gravity wells ===<br />
The text explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Slingshot====<br />
The Title Text indicates that the planets motion can affect the amount of energy for escape velocity {{w|Gravity_assist|to gain (or loose) speed by using the planets orbital speed to gravity assist}} the speed of vehicle. This is know as doing slingshot around planets, and is done to gain speed or to break when needed. On earth the same principle is used slightly differently when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy. Launching rockets in a westward direction would require a significant additional energy. Because of this most artificial satellites are flying from west. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for these factors. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71192681: Gravity Wells2014-07-08T17:48:23Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. <br />
<br />
Escaping a planet's or moon's orbit requires enough energy to reach the top of either peak that defines the edge of the well. The peak to the left indicates the minimum energy to exit orbit by traveling toward the center of the solar system. The peek to the right indicates the maximum energy to exit orbit by traveling directly away from the sun. In reality, the strength of gravity decreases with distance from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The height of the graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable. As the gravitational potential increases with distance from the sun the graph has a general upward slope. To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. <br />
<br />
The length of each gravity well is scaled to the diameter of the planet and the spacing between the planets is not to scale with distance from the sun. This is necessary to make the graph readable. Because the distance between the planets are condensed the gravitational potential, from the gravity pulling toward the sun, accumulates quicker. This is the reason for the large peeks between the planet. The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. <br />
<br />
Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Inner Planets ====<br />
<br />
* {{w|Mercury_(planet)|Mercury}}<br />
<br />
* {{w|Venus_(planet)|Venus}}<br />
<br />
* {{w|Earth}} & {{w|Moon}} - The listed depth of the gravity well of Earth is 5,478&nbsp;km and the Moon's is 288&nbsp;km.<br />
<br />
* {{w|Mars}} - The listed depth of the gravity well of Mars is 1286&nbsp;km<br />
<br />
==== Cut outs ====<br />
<br />
* The Mars cutout shows how weak the gravity of Mars' moons really are. {{w|Deimos (moon)|Deimos}} is so weak that a bike jump would be sufficient to escape its gravity. On {{w|Phobos (moon)|Phobos}} you could launch a baseball into space simply by throwing it.<br />
<br />
* The drawing next to Jupiter is playing on the classic "Yo Mama" joke. It combines "Yo Mama is so fat" and "Yo Mama is so horny". The joke implies that she has a huge gravitational pull and has sex with the entire football team by demonstrating a football team being falling into her very deep gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
<br />
* The Earth/Moon cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments that the {{w|Apollo Lunar Module|Apollo Lunar Module}} was small and the {{w|Saturn V}} rocket was much larger because escaping the Earth's well takes much more energy than escaping the Moon's. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
==== Outer Planets ====<br />
<br />
* {{w|Jupiter}} — Jupiter is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Had a few dozen times the mass of gasses contained in Jupiter condensed in that location, the gravitational pull would cause the pressure and temperature to increase to a level that is sufficient to ignite {{w|Nuclear fusion|nuclear fusion}}. Had that happen during creation of our solar system, we would have two {{w|Sun|Suns}} and our solar system would be a {{w|Binary system (astronomy)|Binary system}}.<br />
* Jupiter's moons<br />
** {{w|Ganymede_(moon)|Ganymede}}<br />
** {{w|Io_(moon)|Io}}<br />
** {{w|Europa_(moon)|Europa}}<br />
<br />
* {{w|Saturn}} & its rings — The diagram shows the position of {{w|Rings of Saturn|Saturn's rings}} in its gravity well. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth.<br />
*Moons of Saturn<br />
** {{w|Titan (moon)|Titan}} — The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
<br />
* {{w|Uranus}} — notably absent is any "your-anus" jokes.<br />
<br />
* {{w|Neptune}} — Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
=== How to calculate gravity wells ===<br />
The text explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
====Slingshot====<br />
The Title Text indicates that the planets motion can affect the amount of energy for escape velocity {{w|Gravity_assist|to gain (or loose) speed by using the planets orbital speed to gravity assist}} the speed of vehicle. This is know as doing slingshot around planets, and is done to gain speed or to break when needed. On earth the same principle is used slightly differently when launching rockets. Rockets are always launched in a eastward direction to make maximum use of the rotational energy. Launching rockets in a westward direction would require a significant additional energy. Because of this most artificial satellites are flying from west. Also, the use of rocket engines are more effective when used at a high speed. This is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for this factor. Therefore leaving the solar system (or any of the gravity wells of the planets) could require less energy than described by the graph, assuming that the launch and slingshots are properly designed and executed.<br />
<br />
==== Escape Velocities ====<br />
<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=Talk:1391:_Darkness&diff=71164Talk:1391: Darkness2014-07-08T02:16:11Z<p>108.162.216.49: </p>
<hr />
<div>http://tvtropes.org/pmwiki/pmwiki.php/Main/MundaneMadeAwesome --[[User:JakubNarebski|JakubNarebski]] ([[User talk:JakubNarebski|talk]]) 07:07, 7 July 2014 (UTC)<br />
Ugghhh, you just HAD to link to TVTropes... Now I'm gonna get sucked into the vortex! [[Special:Contributions/108.162.216.49|108.162.216.49]] 02:16, 8 July 2014 (UTC)<br />
This narrative was actually the very first story I've read in The Onion back in 2006: [http://www.theonion.com/articles/rotation-of-earth-plunges-entire-north-american-co,1905/] -- [[User:Xorg|Xorg]] ([[User talk:Xorg|talk]]) 08:28, 7 July 2014 (UTC)<br />
<br />
Will Eno has a play, "TRAGEDY: a tragedy", which has a very similar set-up (reporters reporting on the fall of night as if they'd never known it before), but never explains how the situation came about --- now thanks to XKCD, we know how come! -- awhyzip, 7 July 2014<br />
<br />
Isn't there a problem with the wish formulation? If the genie does not remember ever granting any wishes, how come the one in the comic is labelled as his "last wish". {{unsigned ip|173.245.49.181}}<br />
<br />
"There usually is an added stipulation" ... really? Most time I read about genies, it's about someone using some clever way to overcome the limit on number of wishes, if there IS any limit to start with - but what I read may not be representative. This may require more research ... what is the most "traditional" genie story? -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 12:47, 7 July 2014 (UTC)<br />
<br />
:The most traditional would be the character simply carefully choosing all three wishes, using the last one at the very end of e story. Again, not representative either, but from what I've read the concept of "getting around the three-wish limit" seems to be a more recent take on the 'traditional' version. [[User:Zowayix|Zowayix]] ([[User talk:Zowayix|talk]]) 13:00, 7 July 2014 (UTC)<br />
<br />
Um... If the genie cannot remember that each wish was NOT his first, that does not preclude him from keeping track of or remembering how many wishes he has made. It doesn't keep him from remembering other wishes, he simply can't remember which one was NOT first. Perhaps I'm over-thinking this, but the genie would probably say, "I may remember your last wish was only your first, but I distinctly remember the 3 wishes you've made so far, especially the one to screw with my head. So... no more wishes for you." XP -naginalf [[Special:Contributions/108.162.216.40|108.162.216.40]] 13:17, 7 July 2014 (UTC)<br />
:I was more wondering about the genie having pause for thought when (remembering no previous wishes) he hears "for my ''last'' wish...". But with genies generally being the 'manual workers' of the magical world, generally being unimaginative (except for those that tend to twist wishes into causing unintended consequences, possibly something that Wish #1 was used to explore the possibility of) and working to rule (perhaps "twist the wish" is one of the rules?), they don't notice. [i]Or[/i] they're so fed up with "bottled servitude" that they'd be quite happy to go along with this new guy with the new attempt at rules-lawyering, at least until they get bored... [[Special:Contributions/141.101.99.192|141.101.99.192]] 14:07, 7 July 2014 (UTC)<br />
<br />
I took this to be a reference to [//wisegeek.com/what-is-a-news-cycle.htm#didyouknowout news cycles]. The wisher was irritated that news reporting is influenced by an artificial constraint like the [//en.wikipedia.org/wiki/24-hour_news_cycle 24 hour news cycle] and wished the media would forget about it. In classic form, a poorly-worded wish is inconveniently interpreted. [[User:Fewmet|Fewmet]] ([[User talk:Fewmet|talk]]) 15:34, 7 July 2014 (UTC)</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=681:_Gravity_Wells&diff=71138681: Gravity Wells2014-07-07T21:05:35Z<p>108.162.216.49: /* Explanation */ Correct verbage</p>
<hr />
<div>{{comic<br />
| number = 681<br />
| date = December 28, 2009<br />
| title = Gravity Wells<br />
| image = gravity_wells.png<br />
| titletext = This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.<br />
}}<br />
<br />
The xkcd page links to [http://xkcd.com/681_large/ a much larger version].<br />
<br />
==Explanation==<br />
{{incomplete|Fix Grammar}}<br />
<br />
The comic shows the gravitational potential (energy transferred per unit mass due to gravity) for the positions of each planet in the solar system, including some moons and Saturn's rings. An object traveling along an upward slope would be giving up energy, while an object traveling along a downward one would be gaining energy. The graph is scaled to kilometers via the gravitational potential an object has at the given height assuming at a constant acceleration due to earths surface gravity.<br />
<br />
To rise out of each well on the diagram, and therefore escape the planets gravity, it would require the same energy required to rise out of a physical well of that depth at Earth's surface gravity. Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface. In reality, the strength of gravity decreases the further you get from the planet. However, a comparison of energy expended to escape the gravitational pull allows for a simpler comparison between the objects.<br />
<br />
The moons shown in the chart are at the appropriate distance from their respective planets' gravity wells for their orbits. The {{w|Sun|Sun's}} gravity well is not shown in its entirety, but is just indicated on the far left as ''"Very very far down"''. Had it been shown in its full extent it would have made the rest of the drawing so small in comparison that it would have been unreadable.<br />
<br />
The Earth's gravity well's depth in the inset and in the main part of the comic don't match. This is most likely a mistake by Randall.<br />
<br />
==== Inner Planets ====<br />
<br />
* {{w|Mercury_(planet)|Mercury}} — no facts listed<br />
<br />
* {{w|Venus_(planet)|Venus}} — no facts listed<br />
<br />
* {{w|Earth}} & {{w|Moon}} — listed with the depth of the gravity well of 5,478&nbsp;km for Earth and 288&nbsp;km for the Moon. Calculations of depth is explained in the Saturn insert.<br />
<br />
* {{w|Mars}} — listed with the depth of gravity well of 1286&nbsp;km<br />
<br />
==== Cut outs ====<br />
<br />
* The Mars cutout shows how small Mars' moons really are, specifically in terms of gravity. {{w|Deimos (moon)|Deimos}} is so small that a bike jump would be sufficient to escape its gravity well and on {{w|Phobos (moon)|Phobos}} you could launch a baseball into space simply by throwing it.<br />
<br />
* The drawing next to Jupiter is playing on the classic "Yo Mama" joke, combining the aspects of your mom being very fat (having a huge gravitational pull) and very slutty (having sex with the entire football team), represented by the football team being attracted to, and falling into, her gravity well. A "Yo Mama" joke also appears in comic [[89: Gravitational Mass]].<br />
<br />
* The Earth/Moon cut out shows the significant difference in strength between the {{w|gravity well}} of the Earth and the Moon. Cueball comments on how the {{w|Apollo Lunar Module|Apollo Lunar Module}} could be so small and still return to Earth while the {{w|Saturn V}} rocket used to get the moon had to be so huge since it was escaping Earth's well while the Lunar Module only needed to escape the pull of the Moon. The cut out also shows that objects like the {{w|International_Space_Station|International Space Station}}, the {{w|Space shuttle|space shuttle}}, {{w|GPS satellite|GPS satellites}} and {{w|Geostationary orbit|geo-stationary satellites}} at their respective positions within Earth's gravity well.<br />
<br />
==== Outer Planets ====<br />
<br />
* {{w|Jupiter}} — is so massive and dense that it is comparable in mass to a {{w|Brown dwarf}} which is the smallest kind of star. Saturn, while similar in size, is composed of much lighter gas material. Hence Saturn's mass and therefore its gravitational pull are much smaller. Strong gravitational pull is a significant factor in igniting fusion. As gravity pulls matter together the pressure and temperature increase. With sufficient increase in pressure and temperature {{w|Nuclear fusion|nuclear fusion}} begins. Had that happen during creation of our solar system, i.e. had a few dozen times the mass of gasses contained in Jupiter condensed in that location, then we would had two {{w|Sun|Suns}} and our solar system would have been a {{w|Binary system (astronomy)|Binary system}}.<br />
** {{w|Ganymede_(moon)|Ganymede}} -- (Moon of jupiter) -- no facts given.<br />
** {{w|Io_(moon)|Io}} -- (Moon of jupiter) -- no facts given.<br />
** {{w|Europa_(moon)|Europa}} -- (Moon of jupiter) -- no facts given.<br />
<br />
* {{w|Saturn}} & its rings — The "Rings" in Saturn's gravity well are {{w|Rings of Saturn|Saturn's rings}}. The farther you get from a planet, the weaker the effect of its gravity on you, so, at some point, when climbing out of Saturn's gravity well, you've reached the point equivalent to starting your climb from the rings of Saturn, or, in fact, from specific rings of Saturn. Saturn's rings start fairly near the planet and extend out quite far, therefore multiple stripes are shown in the figure. The rings are also shown in multiple colors and roughly match the observed colors from photos take by the {{w|Cassini–Huygens|Cassini spacecraft}} expedition as it passed Saturn. All of the colors of the planets and moons represent the predominant color of that object as observed from earth.<br />
** {{w|Titan (moon)|Titan}} — (Moon of Saturn) The figures on Titan are sirens, a reference to Kurt Vonnegut's ''{{w|The Sirens of Titan}}''.<br />
<br />
* {{w|Uranus}} — notably absent is any "your-anus" jokes.<br />
<br />
* {{w|Neptune}} — Megan's quote is a paraphrase of {{w|Carl Sagan|Carl Sagan's}} quote, "...but from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise." [http://www.youtube.com/watch?v=zSgiXGELjbc Video here]<br />
<br />
==== How to interpret gravity wells ====<br />
<br />
To escape a planet's or moon's orbit, you need merely climb to the highest of the two peaks to ''either'' the left or right of the object. So, for example, to escape Venus, you need merely reach the peak left of it, the slope right of it is part of the Sun's gravity well, and shows how much further you'd need to climb out of the Sun's gravity well to get from Venus to Earth. Likewise, the peak left of Jupiter is slightly lower than the one to the right; this is because the rightmost peak includes the difficulty of moving away from the Sun to get to Saturn, the next planet along.<br />
<br />
The text explains that the depth of the well is mass-of-planet over radius-of-planet with newtons constant and 9.81&nbsp;m/s² as constants, where 9.81&nbsp;m/s² is the acceleration of a free falling body at Earth's gravity.<br />
<br />
The calculation for a gravity well is:<br />
:depth = (G * Planet-mass ) / (9.81 m/s<sup>2</sup> * Planet-radius)<br />
::where G is {{w|Isaac_Newton|Newton}}'s {{w|Gravitational_constant|gravitational constant}}, and<br />
::9.81 m/s<sup>2</sup> is the {{w|Acceleration|acceleration}} rate of a {{w|Gravity_of_Earth|free falling body on earth}} at sea level (g).<br />
<br />
<br />
The Title Text refers to that the planet motions can affect the actual amount of energy for escape velocity {{w|Gravity_assist|to gain (or loose) speed by using the planets orbital speed to gravity assist}} the speed of vehicle -- this is know as doing sling-shoot around planets to gain speed (or to break when needed, breaking is just doing the same in reverse) -- on earth the same principle is used slightly differently when launching rockets -- rockets are always launched in a eastward direction to make maximum use of the rotational energy -- launching rockets in a westward direction would require a significant additional energy, and hence most satellites are flying from west to east as turning them in a different orbit would be requiring more fuel. At the same time the use of rocket engines are more effective when used at a high speed which is know as the {{w|Oberth effect}}. The use of engines are therefore more effective when used as part of a slingshot maneuver. <br />
<br />
The size of the gravity-well as described in this comic is not accounting for this factor, and hence leaving the solar system (or any of the gravity wells of the planets) would require less energy than described by the size of each well if the launch and slingshots are carefully planned and executed.<br />
<br />
==== Escape Velocities ====<br />
<br />
The following table was adapted from the table in {{w|Escape velocity#List of escape velocities|Escape velocity}}, using ''h'' = ''V_e''^2 / 2''g'':<br />
{| class="wikitable" border="1"<br />
| Location || with respect to || Ve (km/s) || Well depth (km) ||<br />
| Location || with respect to || Ve (km/s) || Solar well (Mm) || Total depth (Mm) <br />
|-<br />
| on the Sun, || the Sun's gravity: || 617.5 || 19,435,000 || || || || || || 19,435 <br />
|-<br />
| on Mercury, || Mercury's gravity: || 4.3 || 942 ||<br />
| at Mercury, || the Sun's gravity: || 67.7 || 233.6 || 235 <br />
|-<br />
| on Venus, || Venus' gravity: || 10.3 || 5,407 ||<br />
| at Venus, || the Sun's gravity: || 49.5 || 124.9 || 130 <br />
|-<br />
| on Earth, || the Earth's gravity: || 11.2 || 6,393 ||<br />
| at the Earth/Moon, || the Sun's gravity: || 42.1 || 90.3 || 97 <br />
|-<br />
| on the Moon, || the Moon's gravity: || 2.4 || 294 || <br />
| at the Moon, || the Earth's gravity: || 1.4 || || 91 <br />
|-<br />
| on Mars, || Mars' gravity: || 5 || 1,274 ||<br />
| at Mars, || the Sun's gravity: || 34.1 || 59.3 || 61 <br />
|-<br />
| on Jupiter, || Jupiter's gravity: || 59.5 || 180,400 ||<br />
| at Jupiter, || the Sun's gravity: || 18.5 || 17.4 || 198 <br />
|-<br />
| on Ganymede, || Ganymede's gravity: || 2.7 || 372 || || || || || <br />
|-<br />
| on Saturn, || Saturn's gravity: || 35.6 || 64,600 ||<br />
| at Saturn, || the Sun's gravity: || 13.6 || 9.43 || 74 <br />
|-<br />
| on Uranus, || Uranus' gravity: || 21.2 || 22,907 ||<br />
| at Uranus, || the Sun's gravity: || 9.6 || 4.7 || 28 <br />
|-<br />
| on Neptune, || Neptune's gravity: || 23.6 || 28,400 || <br />
| at Neptune, || the Sun's gravity: || 7.7 || 3.02 || 31 <br />
|-<br />
| on Pluto, || Pluto's gravity: || 1.2 || 73 || || || || || <br />
|-<br />
|at Solar System <br/>galactic radius, || the Milky Way's gravity: || 525 || 14,000 <br />
|}<br />
<br />
==Transcript==<br />
:'''Main Text'''<br />
:Gravity Wells scaled to Earth surface gravity<br />
:This chart shows the "depth" of various solar system gravity wells.<br />
:Each well is scaled such that rising out of a physical well of that depth — in constant Earth <u>surface</u> gravity — would take the same energy as escaping from that planet's gravity in reality.<br />
:Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's ''flat'' surface.<br />
:The planet sizes are to the same scale as the wells. Interplanetary distances are not to scale.<br />
:Depth = (G × PlanetMass) / (g × PlanetRadius)<br />
:G = Newton's constant<br />
:g = 9.81 m/s<sup>2</sup><br />
<br />
<br />
:'''Planetary Descriptions'''<br />
:To Sun, very very far down<br />
:Mercury<br />
:Venus<br />
:Earth - 5,478 km<br />
:Moon - 288 km<br />
:Mars - 1,286 km<br />
:Ganymede<br />
:Io<br />
:Jupiter<br />
::[A drawing of a "very deep" gravity well, "Your mom" at the bottom, several member of "local football team" falling down towards her.]<br />
::Jupiter is not much larger than Saturn, but much more massive. At its size, adding more mass just makes it denser due to the extra squeezing of gravity.<br />
::If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.<br />
:Europa<br />
:Titan<br />
::Two figures: Weeoooeeoooeeooo<br />
:Saturn<br />
::Rings<br />
:Uranus<br />
:Neptune<br />
::Megan: An even more glorious dawn awaits!<br />
<br />
<br />
:'''Mars Inset'''<br />
:[Mars gravity well, the Pathfinder probe on its surface, with its moons Deimos and Phobos as smaller gravity wells.]<br />
<br />
:[Figure of a man (to scale) in Deimos's gravity well.]<br />
:You could escape Deimos with a bike and a ramp.<br />
<br />
:[Figure of a man (to scale) in Phobos's gravity well.]<br />
:A thrown baseball could escape Phobos.<br />
<br />
<br />
:'''Earth Inset'''<br />
:[Zoomed-in view of Earth/moon gravity well, featuring the relative locations of the atmosphere, Low Earth Orbit, the International Space Station, the Space Shuttle, GPS satellites, and satellites in geosynchronous orbit.]<br />
:Cueball: This is why it took a huge rocket to get to the moon but only a small one to get back.<br />
<br />
:It takes the same amount of energy to launch something on an escape trajectory away from Earth as it would to launch it 6,000 km upward under constant 9.81 m/s<sup>2</sup> Earth gravity.<br />
<br />
:Hence, Earth's well is 6,000 km deep.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics with color]]<br />
[[Category:Large drawings]]<br />
[[Category:Your Mom]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=674:_Natural_Parenting&diff=69836674: Natural Parenting2014-06-18T16:25:50Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 674<br />
| date = December 11, 2009<br />
| title = Natural Parenting<br />
| image = natural_parenting.png<br />
| titletext = On one hand, every single one of my ancestors going back billions of years has managed to figure it out. On the other hand, that's the mother of all sampling biases.<br />
}}<br />
<br />
==Explanation==<br />
This comic relates to the anxiety most couples experience after having a child. Often people will advise new parents to "do what comes naturally and trust their instincts", a vague snippet of thought that offers little help to the new parents.<br />
<br />
The couple [[Cueball]] and [[Megan]] find themselves with a child. Both parents experience anxiety over how to manage their life with the child. The father defuses the situation and states that parenting can not be that hard because they should do what comes naturally... only for the couple to find themselves with a second child and still no idea about how to parent. The joke is they took the phrase "what comes naturally" literally and acted upon their base urges, giving into the urge "have more sex", rather than actually focusing on the child(ren).<br />
<br />
The title text claims that parenting can't be too hard because historically all of your ancestors (except possibly your parents if they are not yet grandparents) must have figured it out since they produced at least one child that successfully had children. [[Randall]] jokes that this is the "mother" of all {{w|sampling bias}}es. Out of all of our ancestors the only ones that could potentially fail could be our parents (if we do not produce children). Had any other of our ancestors not been successfully we would not exist. Therefore this sampling is heavily skewed by sampling those that where successful in at least one instance. It also does not take into account the number of times our ancestors failed with the children we are not directly related to.<br />
<br />
This was also the topic of [[441: Babies]].<br />
<br />
==Transcript==<br />
:[Cueball and Megan are standing with a baby in between them.]<br />
:Cueball: Oh man, we made a baby.<br />
:Megan: ''Don't panic. Don't panic.''<br />
:Baby: Baby!<br />
<br />
:Cueball: Parenting can't be that hard. Let's just do what comes naturally.<br />
<br />
:[Beat frame.]<br />
<br />
:Soon:<br />
:[There are now two babies in between them.]<br />
:Megan: Aw, crap.<br />
<br />
==Trivia==<br />
*The baby says, "Baby!", either copying Cueball, or saying its name, Pokémon-style.<br />
*[[441: Babies]] is another strip featuring clueless new parents.<br />
*Natural parenting may be an allusion to {{w|attachment parenting}}. This strategy for child-rearing normally entails extended nursing and encourages positive reinforcement. Sometimes modern medicine and processed foods are restricted as well. Natural parenting approaches can vary greatly from parent to parent. Because of the awkwardness and stigma of breastfeeding as well as its traditionalism, attachment parenting can elicit powerful opinions from both its opponents and proponents. Various media and politicians have seized on this hot topic, as well as motherhood in general. Extreme natural parenting methods became the notorious cover story of TIME Magazine in May 2012.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Romance]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=674:_Natural_Parenting&diff=68877674: Natural Parenting2014-06-04T21:54:22Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 674<br />
| date = December 11, 2009<br />
| title = Natural Parenting<br />
| image = natural_parenting.png<br />
| titletext = On one hand, every single one of my ancestors going back billions of years has managed to figure it out. On the other hand, that's the mother of all sampling biases.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|This explain needs a rework on language. Too many guesses like diapers...}}<br />
This comic relates to the anxiety most couples experience after having a child. Often people will advice new parents to do what comes naturally and trust there instincts. This offers little help to the new parents.<br />
<br />
In this comic a couple finds themselves with a child. Both parents experience anxiety over how to manage there life with the child. The father, to defuse the situation states that parenting can not be that hard, and that they should do what comes naturally. Later the couple find them selves with a second child and still no idea about how to parent. Since the couple was attracted to each other enough to have a child in the first place, doing what comes naturally included having another child. Thus the "natural" instincts for breeding are strong, but the instincts for raising children properly are week, incomplete, or nonexistent.<br />
<br />
The title text claims that parenting can't be too hard because historically everyone's grandparents must have figured it out since they produced a child that successfully bred. Randall jokes that this is the "mother" of all {{w|sampling bias}}es because his ancestors represent only the (possibly small) fraction who successful raised children, instead of the entire sample of people attempting to raise children.<br />
<br />
The baby says, "Baby!", either copying Cueball, or saying its name, Pokémon-style.<br />
<br />
[[441: Babies]] is another strip featuring clueless new parents.<br />
<br />
Natural parenting may be an allusion to {{w|attachment parenting}}. This strategy for child-rearing normally entails extended nursing and encourages positive reinforcement. Sometimes modern medicine and processed foods are restricted as well. Natural parenting approaches can vary greatly from parent to parent. Because of the awkwardness and stigma of breastfeeding as well as its traditionalism, attachment parenting can elicit powerful opinions from both its opponents and proponents. Various media and politicians have seized on this hot topic, as well as motherhood in general. Extreme natural parenting methods became the notorious cover story of TIME Magazine in May 2012.<br />
<br />
==Transcript==<br />
:[Cueball and Megan are standing with a baby in between them.]<br />
:Cueball: Oh man, we made a baby.<br />
:Megan: ''Don't panic. Don't panic.''<br />
:Baby: Baby!<br />
<br />
:Cueball: Parenting can't be that hard. Let's just do what comes naturally.<br />
<br />
:[Beat frame.]<br />
<br />
:Soon:<br />
:[There are now two babies in between them.]<br />
:Megan: Aw, crap.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Romance]]</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=Talk:1350:_Lorenz&diff=64263Talk:1350: Lorenz2014-04-03T19:46:23Z<p>108.162.216.49: Can't it be both?</p>
<hr />
<div>I've had the story loop back to the first frame, so it wouldn't surprise me if this could go on infinitely if it had the available dialogue options.<br />
<br />
This is going to be a hell of a thing. Good luck... [[User:H|H]] ([[User talk:H|talk]]) 15:39, 1 April 2014 (UTC)<br />
:I think this is one of those times when the custom field might come in handy. Duplicating Randall's code seems like it might be difficult, and it might just be easier to link to the original page. Probably. '''[[User:Davidy22|<u>{{Color|#707|David}}<font color=#070 size=3>y</font></u><font color=#508 size=4>²²</font>]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 15:47, 1 April 2014 (UTC)<br />
::I think it should just show a screenshot of the initial image and options [[Special:Contributions/173.245.50.61|173.245.50.61]] 02:49, 2 April 2014 (UTC)<br />
<br />
There's always new story lines, even when you think you've read them all, new ones appear to replace them. I don't think it'll ever be possible to record them all. [[Special:Contributions/108.162.212.192|108.162.212.192]] 15:55, 1 April 2014 (UTC)<br />
:The text changes, but there are recurring themes with the panels. The rocket, the big hole, the little hole, Dinosaurcomics, pokemon, waking up, stranded swimming.........[[User:H|H]] ([[User talk:H|talk]]) 18:03, 1 April 2014 (UTC)<br />
<br />
When I go to XKCD, all I see is the comic from Monday... weird. --[[User:Jeff|<b><font color="orange">Jeff</font></b>]] ([[User talk:Jeff|talk]]) 16:45, 1 April 2014 (UTC)<br />
:Same here... and a lot of space below it. [[User:Z|Z]] ([[User talk:Z|talk]]) 17:43, 1 April 2014 (UTC)<br />
:: I think that happens when you have refreshed the page too many time -- kind of an anti spam for user submissions. I simply create an anonymous browser window and I got back to the real page once xkcd was not able to track me as a returning user. [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 17:59, 1 April 2014 (UTC)<br />
<br />
Currently there appears to be a bug. Instead of the evolving, crowd-sourced comic, I just see an off-center copy of the previous comic, 1349: Shouldn't Be Hard. [http://i.imgur.com/pw2OfOL.png Screenshot here]. <br />
UPDATE: it appears to be a bug in the XSRF-blocking code. Chrome console shows me the error "XMLHttpRequest cannot load http://c1.xkcd.com/graph/1/. The 'Access-Control-Allow-Origin' header has a value 'http://xkcd.com' that is not equal to the supplied origin. Origin 'http://www.xkcd.com' is therefore not allowed access." <br />
FURTHER UPDATE: you can work around this bug by going to http://xkcd.com instead of http://www.xkcd.com!<br />
It also doesn't work if you have HTTPS Everywhere enabled.<br />
[[Special:Contributions/108.162.216.38|108.162.216.38]] 16:46, 1 April 2014 (UTC)<br />
<br />
** I can confirm this bug in Firefox. Weirdly, the work-around functioned one time for me, but now going to "xkcd.com" rather than "www.xkcd.com" just gives me a copy of 1349 as well. [[Special:Contributions/199.27.130.180|199.27.130.180]] 17:40, 1 April 2014 (UTC)<br />
:The workaround didn't work for me, I still got monday's comic on either URL. (Chromium 36.0.1919.0 (260611), Mac OS 10.9.2) [[User:Z|Z]] ([[User talk:Z|talk]]) 17:45, 1 April 2014 (UTC)<br />
:Same here. Used IE and Firefox. Removed the "www." and haven't. (Never used https:// at all.) Tried InPrivate (and FF equivalent) browsers. Gone into the code and can't even fudge it manually from ''<nowiki><div id="comic"><img src="http://imgs.xkcd.com/comics/shouldnt_be_hard.png" title="Every choice, no matter how small, begins a new story." alt="Lorenz" /> <script type="text/javascript">Bernardo.comic({el: $('#comic')})<br />
</script></div></nowiki>'', and the rest, manually. (Indeed, that shows why I get 1349's "shouldn't be hard" image, by default.) Pity. [[Special:Contributions/141.101.89.224|141.101.89.224]] 02:25, 2 April 2014 (UTC)<br />
<br />
This comic introduced(?) a font of its own of Randalls comic type. I don't know if it has been sitting there for long, but I just noticed it: http://xkcd.com/fonts/xkcd-Regular.eot -- phiarc [[Special:Contributions/108.162.219.12|108.162.219.12]] 17:20, 1 April 2014 (UTC)<br />
:Is it the same as was used in Externalities? [[User:H|H]] ([[User talk:H|talk]]) 18:00, 1 April 2014 (UTC)<br />
<br />
Does everyone have these options in some order for the first tile?<br />
*Refresh... No New Email... Refresh .. No New Tweets... Refresh...<br />
*These Stupid Tiles... I'll Just Play One More Game<br />
*Oh. Hey. There's Some Kind Of Politicial Thing Going On.<br />
*Let's See If BSD Is Any Easier to Install Nowadays<br />
--[[User:Jeff|<b><font color="orange">Jeff</font></b>]] ([[User talk:Jeff|talk]]) 17:54, 1 April 2014 (UTC)<br />
<br />
:If so, we can begin to build a map of at least the first set of options before the crowd-sourced ones. --[[User:Jeff|<b><font color="orange">Jeff</font></b>]] ([[User talk:Jeff|talk]]) 17:56, 1 April 2014 (UTC)<br />
::Yes, though the second-tier options have changed [[User:H|H]] ([[User talk:H|talk]]) 18:00, 1 April 2014 (UTC)<br />
:::The first level options may be constant (Im seeing the same as Jeff), but I suspect that the following options is based on some sort of ckick though statitics / machine learning -- which means that the will continue to change until Randall closes off the 'voting' -- if [http://www.explainxkcd.com/wiki/index.php/1193:_Externalities 1193: Externalities] is anything to go by that should be within the next 24-48 hours, at which point automating the collection of story lines may be possible. [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 18:11, 1 April 2014 (UTC)<br />
:::: I'm going to transcript some of what I get at least through the first few levels and then we can start with a list of options for those who don't want to go through them all. --[[User:Jeff|<b><font color="orange">Jeff</font></b>]] ([[User talk:Jeff|talk]]) 18:37, 1 April 2014 (UTC)<br />
::::: I have no idea how one would do this, but it would be cool to render the transcript as a tree of some sort; having one vertical list will be hard to follow for more than a few decisions. [[Special:Contributions/199.27.130.180|199.27.130.180]] 00:14, 2 April 2014 (UTC)<br />
<br />
Ohh, this comic is buggy and the link here at the top gives just the page from Monday, showing errors on debuggers. But removing the WWW from URL helps. Further more I can't see that the result of the choices is dynamic. So let's prove this. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 19:33, 1 April 2014 (UTC)<br />
: Have a look at http://www.explainxkcd.com/wiki/images/2/2b/lorenz_combination1.png and http://www.explainxkcd.com/wiki/images/9/9a/lorenz_combination2.png and you can see the option orders are changing -- this is a typical artifact of A/B testing where randomization of options is needed to avoid selection bias. I have futher observed "your car is on fire" instead of the "dinosaur" option, hence not only the orders are channging but the content as well -- maybe somebody else can capture this. [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 22:08, 1 April 2014 (UTC) <br />
<br />
How are new dialogue suggestions approved? Are they random, by popular vote (unlikely, not very many people would suggest the same thing), or is Randall approving them one by one? [[User:Z|Z]] ([[User talk:Z|talk]]) 20:26, 1 April 2014 (UTC)<br />
: They may not need to be explicitly approved at all -- one of the beutiful things about click though measures is that the public '''votes''' for what is good by clicking -- this is also a factor in search ranking by your favorite search engine where statistics are driving the entire show -- in a search engine some input to the statistical process comes from the web pages, but other comes from what people are actually clicking [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 22:14, 1 April 2014 (UTC) <br />
<br />
What is this a screenshot of? It's zoomed out so far. http://xkcd.com/1350/#p:5b5bd04e-b9d6-11e3-8008-002590d77bdd [[User:Haithere|Haithere]] ([[User talk:Haithere|talk]]) 20:39, 1 April 2014 (UTC)<br />
: you mean this : http://imgs.xkcd.com/comics/a1-2014/Rl92nFEWd9huvXABNkHKHg.png ? [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 22:20, 1 April 2014 (UTC)<br />
:: It appears to be a screen shot from a flight simulator program of some sort, however im not able to tell which, and since it is most likely an 'in-game' screen short we will never find out unless somebody else is playing this precises flight simulator program [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 22:37, 1 April 2014 (UTC)<br />
:: I am not certain, but I strongly suspect that is Kerbal Space Program {{unsigned ip|108.162.242.111}}<br />
::: it really is Kerbal Space Program, or KSP for short {{unsigned ip|108.162.219.65}}<br />
:::: found this image from KSP http://i.imgur.com/UofvQ.png [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 09:07, 2 April 2014 (UTC)<br />
<br />
A transcript is going to be futile. It appears as though the comic may go on indefinitely (I've definitely had some branches continue extending until I've seen frames that were present in other branches). I suspect what's happening here is that... options are "suggested", and those suggestions are displayed at random to people. The ones with the most clickthroughs begin to appear more often, until eventually the top 4 are "locked in" and no more suggestions can be made. Very creative! But I'm not convinced that Randall is making frames in near-real-time, nor am I even convinced he's part of the approval process at all. I suspect it's all automated. [[Special:Contributions/108.162.215.28|108.162.215.28]] 00:29, 2 April 2014 (UTC)<br />
<br />
<br />
It seems it is possible to have the same option appear twice in the first panel. http://xkcd.com/1350/#p:be7a3304-b685-11e3-8001-94de80a03a29 --[[Special:Contributions/173.245.54.48|173.245.54.48]] 10:27, 2 April 2014 (UTC)<br />
: They are not the same options -- the text differes where one option has "I'll" with a captal I and the other option is 'i'll' with a lowercase I -- I guess some prankster submitted a very similar text and somehow that got included. The branching also differs for the two options. [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 17:12, 2 April 2014 (UTC)<br />
<br />
Is it still supposed to work or was it turned off? All I see is Monday comics ... and no errors in firebug console. Oh, wait, there is javascript error:<br />
Timestamp: 04/02/14 12:56:21<br />
Error: TypeError: this.$lastPanel is null<br />
Source File: http://xkcd.com/1350/bernardo.min.js<br />
Line: 2 -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 11:03, 2 April 2014 (UTC)<br />
: It still works for me -- try to clear your cookies or use an anonymous window or go to xkcd.com (no www no https) or some of the other helpful suggestions on this page to overcome some of the buggy nature of this page. [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 17:12, 2 April 2014 (UTC)<br />
<br />
tl;dr, but I applaud Randall's creativity. Added to the Colossal time sinks category. ''– [[User:Tbc|tbc]] ([[User talk:Tbc|talk]]) 13:15, 2 April 2014 (UTC)''<br />
<br />
Has it restarted? It used to work just fine on my browser but now only the first panel is available, after clicking an option it said my suggestion has been submitted. Great when it works though, thanks Randal. Jet_proppeled_elephant[[Special:Contributions/108.162.219.35|108.162.219.35]] 14:53, 2 April 2014 (UTC)<br />
<br />
It feels like there are a bunch of "dead-end panels", that we never really get past. One example the "bright background" strip, in which we only see the shadows of the two characters. Nobody seems to care what happens after those. [[Special:Contributions/108.162.245.8|108.162.245.8]] 18:59, 2 April 2014 (UTC)<br />
<br />
I found a Dinosaur Comics reference, permalink: http://xkcd.com/1350/#p:3d243960-b9b6-11e3-8001-002590d77bdd<br />
Has this been found before?<br />
[[Special:Contributions/173.245.55.73|173.245.55.73]] 20:08, 2 April 2014 (UTC)<br />
<br />
I don't have time to do it myself, but most of the space images from this path are not in the images page. http://xkcd.com/1350/#p:6490cc4a-b9f0-11e3-8009-002590d77bdd<br />
[[User:Zweisteine|Zweisteine]] ([[User talk:Zweisteine|talk]]) 23:33, 2 April 2014 (UTC)<br />
:Ok, I'm gonna add those. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 23:38, 2 April 2014 (UTC)<br />
Great! And now I found another: Pikachu uses Ethylene Dichloride. http://xkcd.com/1350/#p:6f59d766-ba95-11e3-8001-002590d77bdd<br />
I'll add it to the but about pikachu in the comic, but the pictures are up to someone else.[[User:Zweisteine|Zweisteine]] ([[User talk:Zweisteine|talk]]) 23:47, 2 April 2014 (UTC)<br />
<br />
Slightly different space path, in which the rocket expodes: http://xkcd.com/1350/#p:dd99ea0e-ba04-11e3-8017-002590d77bdd [[User:Zweisteine|Zweisteine]] ([[User talk:Zweisteine|talk]]) 23:59, 2 April 2014 (UTC)<br />
<br />
:Good. I've finished adding all images that you mentioned. Also, the two last images of the slightly different space path were not in the images page, now I added them too. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 00:14, 3 April 2014 (UTC)<br />
<br />
Pikachu died! Radicality failed -> Pikachu in shock! http://xkcd.com/1350/#p:5c565bf2-ba05-11e3-8017-002590d77bdd --eternia 7:33, 3 April 2014 (UTC)<br />
:Pikachu uses Graph Theory. How is that not effective?! http://xkcd.com/1350/#p:52f2389c-baaf-11e3-801f-002590d77bdd --eternia 7:47, 3 April 2014 (UTC)<br />
::Pikachu uses Ant Colony. Uwah... http://xkcd.com/1350/#p:2b707ed6-ba97-11e3-8006-002590d77bdd --eternia 8:02, 3 April 2014 (UTC)<br />
:::1 shark instead of 3. http://xkcd.com/1350/#p:9ba111ee-ba96-11e3-8004-002590d77bdd --eternia 8:14, 3 April 2014 (UTC)<br />
::::0 sharks. http://xkcd.com/1350/#p:e0e4d984-baaf-11e3-8026-002590d77bdd --eternia 8:17, 3 April 2014 (UTC)<br />
:::::I'm gonna add those too. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 12:41, 3 April 2014 (UTC)<br />
<br />
Are there any panels that have two speech bubbles that are not dead ends? It seems that there are never any options for the second bubble, and sometimes the first bubble has options that would fit in the second bubble after the other options for the first bubble. Maybe submissions for the second bubble accidentally end up in the first instead? Another bug? [[User:Zweisteine|Zweisteine]] ([[User talk:Zweisteine|talk]]) 23:56, 2 April 2014 (UTC)<br />
<br />
We need some place to discuss certain issues. I give it a shot below [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:10, 2 April 2014 (UTC)<br />
;Transcipt discussion<br />
;Design<br />
*What about four transcripts - one for each of the four first original choices? <br />
*Should these transcripts be on a separate page? It becomes tedious to scroll to the discussion page...[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:13, 2 April 2014 (UTC)<br />
*Could we use the hide option so you only see the options from the first panel. Then you unhide to see the next panel etc. This would be a little like the comic and would make it much easier to read and it would not be such a long page! [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:35, 3 April 2014 (UTC)<br />
*:I'm working on the hide option. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 15:14, 3 April 2014 (UTC)<br />
*::I now implemented the hide option. It looks good! in my opinion. It should be easy to edit. It would be too much work to convert the whole thing to the collapsible version so, sorry but I just removed the whole thing and started from the very beginning. This[http://www.explainxkcd.com/wiki/index.php?title=1350:_Lorenz&oldid=64245] is the link to the old version, in case anyone wants to help converting it to the collapsible version. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 16:46, 3 April 2014 (UTC)<br />
<br />
;Characters<br />
*Where does the name Dave come from for the hairy guy who comes in after the first panel? I can see it once in the transcript - but it is said by White hat the sales guy. I'm not sure it is his name and the chatagory for hairy is assigned to the comic! [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:16, 2 April 2014 (UTC)<br />
** Also he is called Dave here: http://www.xkcd.com/1350/#p:3b1a226e-b9c6-11e3-8001-002590d77bdd [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 21:37, 2 April 2014 (UTC)<br />
*Hat guy? Is it a hat? Is there not a better English word for the type of "hat" worn by the main character from the first panel? It is not a hat like white or black hat! [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:18, 2 April 2014 (UTC)<br />
** I named him Hat Guy originally to make things easier. Feel free to change the name, I guess :) Knit Cap Guy, maybe? If a change is warranted, a simple search-and-replace should do it. Also, I'm not sure it's a guy or a girl... But the previous text was also treating him as male to begin with, anyway. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 21:36, 2 April 2014 (UTC)<br />
*Is the right politician = Cueball?<br />
*Who is the left? [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:23, 2 April 2014 (UTC)<br />
<br />
Isn't is likely that the characters only have names given to them by us readers in our suggestions? They don't necessarily have constant names. [[User:Zweisteine|Zweisteine]] ([[User talk:Zweisteine|talk]]) 23:33, 2 April 2014 (UTC)<br />
<br />
Exactly my point. I think we should stick with hairy guy and maybe Knit Cap Guy! [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:28, 3 April 2014 (UTC)<br />
<br />
:I see you already changed Hat Guy to Knit Cap Guy and Dave to Hairy. Knit Cap Guy is a nice name. Originally, I would disagree with you and insist we should stick to Dave because that's what the character is called in one storyline of the strip itself, but I see he is also called Frank in other timeline. Since he has multiple names, using just Hairy is better in my opinion, too. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 12:40, 3 April 2014 (UTC)<br />
<br />
Knit Cap Guy is probably a Girl. Just sayin'. [[Special:Contributions/173.245.52.28|173.245.52.28]] 12:22, 3 April 2014 (UTC)<br />
<br />
:Probably! Originally I thought it was Megan with a knit cap on. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 12:40, 3 April 2014 (UTC)<br />
<br />
;Other<br />
*Seems like the permalink at the top of the transcript does not work for me anymore - then they will be useless! Else they are the best way to quote different lines of the comic. [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:31, 2 April 2014 (UTC)<br />
Oh, now they work again. ;) [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:31, 3 April 2014 (UTC)<br />
<br />
;Chategories not yet included<br />
Should they be?<br />
*I have seen the word Raptor mentioned - so should velociraptor be a chategory? [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:21, 2 April 2014 (UTC)<br />
*Cueball? I.e. the politician on the right? [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:28, 2 April 2014 (UTC)<br />
<br />
;Images<br />
I created [[1350: Lorenz/Images]] with all the images I could find in the comic. I'm not sure if I should have left them in the main page [[1350: Lorenz]], but feel free to decide what to do with them. Also, I tried using the tag <nowiki><gallery></nowiki>, but I couldn't make it work, so I used a lot of divs. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 23:23, 2 April 2014 (UTC)<br />
:Great idea - just what I hoped someone would and could do. Thanks ;) Is it easy to add new images to the page if they show up? [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:32, 3 April 2014 (UTC)<br />
::You're welcome! :) It's pretty easy... I explained in the images page how exactly you would save a new image if they show up. [[User:Daniel Carrero|Daniel Carrero]] ([[User talk:Daniel Carrero|talk]]) 13:52, 3 April 2014 (UTC)<br />
:Can see there keep appearing new images from the text above. [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:39, 3 April 2014 (UTC)<br />
<br />
;Many-worlds interpretation<br />
<br />
The title text "Every choice, no matter how small, begins a new story" might as well be a hint to Hugh Everett III 's "Many-worlds interpretation"<br />
of quantum theory. {{unsigned ip|108.162.219.74}}<br />
:Except that the title is Lorenz a direct reference to the guy with the butterfly effect... [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:37, 3 April 2014 (UTC)<br />
::Can't it be both? The Butterfly Effect can be seen as one consequence of the Many-Worlds interpretation. A choice as simple as whether (or where) a butterfly flaps its wings can send our entire universe down a different timeline, in which a hurricane occurs. [[Special:Contributions/108.162.216.49|108.162.216.49]] 19:46, 3 April 2014 (UTC)</div>108.162.216.49https://www.explainxkcd.com/wiki/index.php?title=1082:_Geology&diff=589491082: Geology2014-01-29T16:44:03Z<p>108.162.216.49: /* Explanation */</p>
<hr />
<div>{{comic<br />
| number = 1082<br />
| date = July 16, 2012<br />
| title = Geology<br />
| image = geology.png<br />
| titletext = That's a gneiss butte.<br />
}}<br />
<br />
== Explanation ==<br />
Here we have [[Cueball]] and [[Megan]] discussing Geology and the words they use are ripe with puns and {{w|double entendre}}s which also have sexual meanings. In the end they just decide to get it on.<br />
<br />
Specifically, the suggestive terms are "bedding," "spreading," "friction," "cleavage," "deeper in the rift," "orogeny," "huge," and "thrust."<br />
<br />
In the title text, {{w|gneiss}} (pronounced "nice") is a type of rock, and {{w|Butte (geology)|butte}} (rhymes with "cute") is a conspicuous isolated hill with steep, often vertical sides and a small, relatively flat top. Thus, a "gneiss butte" is a play on "nice butt".<br />
<br />
== Transcript ==<br />
:[Two people are doing a geological survey.]<br />
:Megan: Forget the bedding - we were wrong about the whole valley.<br />
:Cueball: The spreading is recent.<br />
:Megan: See the friction breccia?<br />
:Cueball: Oh - flow cleavage! Deeper in the rift.<br />
:Megan: Deeper.<br />
:[An idea pops into Megan's head.]<br />
:Megan: This orogeny<br />
:Cueball: is driven by a<br />
:Megan: ''huge''<br />
:Cueball: ''thrust'' fault<br />
:[The same idea pops into Cueball's head.]<br />
:[They both drop to the ground in a fit of passion.]<br />
:Geology: Surprisingly erotic.<br />
<br />
{{comic discussion}}<br />
[[Category:Comics featuring Cueball]]<br />
[[Category:Comics featuring Megan]]<br />
[[Category:Language]]<br />
[[Category:Romance]]<br />
[[Category:Physics]]<br />
[[Category:Sex]]</div>108.162.216.49