explain xkcd - User contributions [en]

Talk:1644: Stargazing

2016-02-20T19:27:04Z

108.162.216.20:

?.. is this Brian Cox??? [[Special:Contributions/162.158.152.155|162.158.152.155]] 06:07, 17 February 2016 (UTC)

My first thought was that it was a pisstake of Brian Cox, except I wasn't sure if they had Stargazing Live in America. [[Special:Contributions/162.158.152.143|162.158.152.143]] 08:33, 17 February 2016 (UTC)
: Brian Cox seems like a nice guy and I applaud his enthusiasm, but if you want to see a truly awesome science broadcaster look for a set of broadcasts from the 70s/80s by James Burke titled "The Day the Universe Changed", Mr. Cox's programmes seem to be as much about how many airmiles the production team can accumulate as they are about the science. [[Special:Contributions/162.158.34.147|162.158.34.147]] 09:10, 17 February 2016 (UTC)
:: The airmiles comment above applies to Cox's "Wonders Of The Universe" series, certainly, but my first thought was either that Randall knew of the BBC's semi-regular programme-cluster "{{w|Stargazing Live}}", here in the UK, that Cox co-presents - perhaps via BBC America? - or else there's an equivalent US version (precursor or postcursor) of the same name that perhaps has a celebrity-based core team.
:: (Brian's primary co-host in the programme ''is'' an Irish comedian, but one with a accredited science background who knows what they're talking about. They also have 'guest celebrities' for internal and external segments (from just outside the studio, under the night sky, to a pieces filmed/livecast at some space-relevant location, usually featured across all episodes of that season as a theme so not so much 'gratuitous globe-trotting) but they are all ''interested'' in space-stuff, and many ''also'' have an actual background expertise in physics/astronomy even if that's not what they're publicly known for.)
:: Quickly looking around, I can't see any ''obvious'' astronomy programmes(/programs!) in the US that aren't similarly expert-led, but that's possibly because any that are don't feature as 'proper' programmes on any of the lists I've checked. [[Special:Contributions/162.158.152.89|162.158.152.89]] 14:25, 17 February 2016 (UTC)
:: The title text does imply it is in reference to Brian Cox. He is well known for his very philosophical comments referencing physics in that way. [[Special:Contributions/141.101.70.151|141.101.70.151]] 20:05, 17 February 2016 (UTC)
:: Hmmm... intentional reference to The Infinite Monkey Cage, with infinite choices of branches, then? [[Special:Contributions/162.158.152.89|162.158.152.89]] 12:46, 18 February 2016 (UTC)

I also thought this might be poking fun at the "Celebrity" presenters of TV astronomy programs. [[Special:Contributions/141.101.106.173|141.101.106.173]] 13:16, 17 February 2016 (UTC)

I believe the title text may be referring to the fact that several people think that the sun is the brightest star simply because it's the closest to us, completely disregarding absolute magnitude? I'd change the explanation if I knew how. --[[Special:Contributions/108.162.245.181|108.162.245.181]] 06:39, 17 February 2016 (UTC)

The original statement in the comic is about which star is the brightest *in our sky*, i.e. most visible radiation per square meter hitting Earth, not the star with the most total radiation. You can change the explanation just by hitting the little edit button to the top right of the "Explanation" section.
[[Special:Contributions/108.162.237.91|108.162.237.91]] 06:57, 17 February 2016 (UTC)

I still don't get the main comic, unless its just situational comedy of someone acting like they know what they are talking about, when really they don't even know the meaning of the word "astronomer". [[Special:Contributions/108.162.237.91|108.162.237.91]] 07:01, 17 February 2016 (UTC)

I put my best understanding of the comic in the explanation - I'm not sure I really get it, but I figured it was better than nothing. [[Special:Contributions/108.162.237.91|108.162.237.91]] 07:14, 17 February 2016 (UTC)

This is exactly how I feel about looking at stars and hard core astronomy. I look for the brightest stars, and would like to know something about them, but just the basic facts. I have had a course on astronomy and it was boring to do the math for star formation and cosmology. I learnt that way that I was only interested in the results and conclusions, not in trying to calculate it my self, or counting all the other smaller stars to gain the data needed. I really like Megan here ;-) Space is awesome, astronomy is boring :-) --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 09:08, 17 February 2016 (UTC)

I am pretty sure the last line in the first panel used to read "I'm doctor '''of''' whatever", but now it's clearly "... doctor '''or''' whatever". Has Randall changed the comic? -- [[Special:Contributions/141.101.106.11|141.101.106.11]] 13:06, 17 February 2016 (UTC)
:I wrote the original transcript based on the comic on this site. This has since been corrected to or, which makes sense. But the image file for the comic has not been changed here on xkcd, so had it not been for your comment here, I would just have put it down to a typo on my behalf. I still think so, as I believed she said ''or whatever'' when I wrote about it in the explanation. But the "or" can look a little as "of". It is, however, not unheard of that Randall changes a comic if he spots a mistake after the first release. This has happened several times. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 14:50, 17 February 2016 (UTC)

From now on I plan to present Sirius as the brightest star that can be seen at night, just to take the wind out of the jokers sails... [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 14:34, 17 February 2016 (UTC)

I wonder if the style of speaking is a reference to Donald Trump.
[[Special:Contributions/108.162.237.90|108.162.237.90]] 19:31, 17 February 2016 (UTC)

She'd reminding me an awful lot of [[Beret Guy]] here, kind of scattered and . Is it just me? [[User:N0lqu|-boB]] ([[User talk:N0lqu|talk]]) 20:42, 17 February 2016 (UTC)
:It's not just you... and from that point of view the title text doesn't read like sarcasm to me. Perhaps more a reference to choosing branches of science to explore? Then again, at least one person thought it was sarcastic, and I don't feel strongly enough to change the explanation over it. [[Special:Contributions/108.162.250.161|108.162.250.161]] 01:35, 18 February 2016 (UTC)

Not true there is nothing in interstellar space. Dust, vacuum, photons, even heat energy. 08:02, 18 February 2016 (UTC)

Could the final "Space!" be a reference to the ending of Portal 2? [[User:Condor70|Condor70]] ([[User talk:Condor70|talk]]) 11:02, 18 February 2016 (UTC)

Maybe the title text is referring to that one multiverse theory where every possible outcome creates it's own timeline? i'm spacing out on it's name right now, but i think it's been mentioned a few times in previous comics.--[[User:Flamewolf|Flamewolf]] ([[User talk:Flamewolf|talk]]) 19:44, 18 February 2016 (UTC)

Regarding the Incomplete reasoning: "There may be another joke here. What about the branches in the title text. Is there some well known reference to such a tree. Sound like something with parallel universes and infinite possibilities?"... I must disagree, there's no other joke here. The word "branch" here isn't referring to any tree, but rather the ongoing logical possibilities of a conversation. If you take a video game where you can chose what you say in a conversation (or the choose-your-own-comic xkcd that came out a while ago), and map out all the options, it would look like a "tree", selecting THIS option leads to a new set of options, each of which will lead to ITS own set of options. In the aforementioned comic, selecting "Let me refresh" in the first panel leads to a different set of options for the second panel than if you had selected something else for the first panel. You are now following the "Let me refresh" branch of the conversation. That's all "branch" means in the title, it's referring to the conversation which would result from this, which would "branch off" of such a declaration. - NiceGuy1[[Special:Contributions/198.41.235.215|198.41.235.215]] 06:22, 20 February 2016 (UTC)

The text in the second panel has changed from 'That's andromeda' to 'This is andromeda'. Just an fyi. [[Special:Contributions/108.162.216.20|108.162.216.20]] 19:26, 20 February 2016 (UTC)

Talk:1644: Stargazing

2016-02-20T19:26:01Z

108.162.216.20: /* comic changed */ new section

?.. is this Brian Cox??? [[Special:Contributions/162.158.152.155|162.158.152.155]] 06:07, 17 February 2016 (UTC)

My first thought was that it was a pisstake of Brian Cox, except I wasn't sure if they had Stargazing Live in America. [[Special:Contributions/162.158.152.143|162.158.152.143]] 08:33, 17 February 2016 (UTC)
: Brian Cox seems like a nice guy and I applaud his enthusiasm, but if you want to see a truly awesome science broadcaster look for a set of broadcasts from the 70s/80s by James Burke titled "The Day the Universe Changed", Mr. Cox's programmes seem to be as much about how many airmiles the production team can accumulate as they are about the science. [[Special:Contributions/162.158.34.147|162.158.34.147]] 09:10, 17 February 2016 (UTC)
:: The airmiles comment above applies to Cox's "Wonders Of The Universe" series, certainly, but my first thought was either that Randall knew of the BBC's semi-regular programme-cluster "{{w|Stargazing Live}}", here in the UK, that Cox co-presents - perhaps via BBC America? - or else there's an equivalent US version (precursor or postcursor) of the same name that perhaps has a celebrity-based core team.
:: (Brian's primary co-host in the programme ''is'' an Irish comedian, but one with a accredited science background who knows what they're talking about. They also have 'guest celebrities' for internal and external segments (from just outside the studio, under the night sky, to a pieces filmed/livecast at some space-relevant location, usually featured across all episodes of that season as a theme so not so much 'gratuitous globe-trotting) but they are all ''interested'' in space-stuff, and many ''also'' have an actual background expertise in physics/astronomy even if that's not what they're publicly known for.)
:: Quickly looking around, I can't see any ''obvious'' astronomy programmes(/programs!) in the US that aren't similarly expert-led, but that's possibly because any that are don't feature as 'proper' programmes on any of the lists I've checked. [[Special:Contributions/162.158.152.89|162.158.152.89]] 14:25, 17 February 2016 (UTC)
:: The title text does imply it is in reference to Brian Cox. He is well known for his very philosophical comments referencing physics in that way. [[Special:Contributions/141.101.70.151|141.101.70.151]] 20:05, 17 February 2016 (UTC)
:: Hmmm... intentional reference to The Infinite Monkey Cage, with infinite choices of branches, then? [[Special:Contributions/162.158.152.89|162.158.152.89]] 12:46, 18 February 2016 (UTC)

I also thought this might be poking fun at the "Celebrity" presenters of TV astronomy programs. [[Special:Contributions/141.101.106.173|141.101.106.173]] 13:16, 17 February 2016 (UTC)

I believe the title text may be referring to the fact that several people think that the sun is the brightest star simply because it's the closest to us, completely disregarding absolute magnitude? I'd change the explanation if I knew how. --[[Special:Contributions/108.162.245.181|108.162.245.181]] 06:39, 17 February 2016 (UTC)

The original statement in the comic is about which star is the brightest *in our sky*, i.e. most visible radiation per square meter hitting Earth, not the star with the most total radiation. You can change the explanation just by hitting the little edit button to the top right of the "Explanation" section.
[[Special:Contributions/108.162.237.91|108.162.237.91]] 06:57, 17 February 2016 (UTC)

I still don't get the main comic, unless its just situational comedy of someone acting like they know what they are talking about, when really they don't even know the meaning of the word "astronomer". [[Special:Contributions/108.162.237.91|108.162.237.91]] 07:01, 17 February 2016 (UTC)

I put my best understanding of the comic in the explanation - I'm not sure I really get it, but I figured it was better than nothing. [[Special:Contributions/108.162.237.91|108.162.237.91]] 07:14, 17 February 2016 (UTC)

This is exactly how I feel about looking at stars and hard core astronomy. I look for the brightest stars, and would like to know something about them, but just the basic facts. I have had a course on astronomy and it was boring to do the math for star formation and cosmology. I learnt that way that I was only interested in the results and conclusions, not in trying to calculate it my self, or counting all the other smaller stars to gain the data needed. I really like Megan here ;-) Space is awesome, astronomy is boring :-) --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 09:08, 17 February 2016 (UTC)

I am pretty sure the last line in the first panel used to read "I'm doctor '''of''' whatever", but now it's clearly "... doctor '''or''' whatever". Has Randall changed the comic? -- [[Special:Contributions/141.101.106.11|141.101.106.11]] 13:06, 17 February 2016 (UTC)
:I wrote the original transcript based on the comic on this site. This has since been corrected to or, which makes sense. But the image file for the comic has not been changed here on xkcd, so had it not been for your comment here, I would just have put it down to a typo on my behalf. I still think so, as I believed she said ''or whatever'' when I wrote about it in the explanation. But the "or" can look a little as "of". It is, however, not unheard of that Randall changes a comic if he spots a mistake after the first release. This has happened several times. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 14:50, 17 February 2016 (UTC)

From now on I plan to present Sirius as the brightest star that can be seen at night, just to take the wind out of the jokers sails... [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 14:34, 17 February 2016 (UTC)

I wonder if the style of speaking is a reference to Donald Trump.
[[Special:Contributions/108.162.237.90|108.162.237.90]] 19:31, 17 February 2016 (UTC)

She'd reminding me an awful lot of [[Beret Guy]] here, kind of scattered and . Is it just me? [[User:N0lqu|-boB]] ([[User talk:N0lqu|talk]]) 20:42, 17 February 2016 (UTC)
:It's not just you... and from that point of view the title text doesn't read like sarcasm to me. Perhaps more a reference to choosing branches of science to explore? Then again, at least one person thought it was sarcastic, and I don't feel strongly enough to change the explanation over it. [[Special:Contributions/108.162.250.161|108.162.250.161]] 01:35, 18 February 2016 (UTC)

Not true there is nothing in interstellar space. Dust, vacuum, photons, even heat energy. 08:02, 18 February 2016 (UTC)

Could the final "Space!" be a reference to the ending of Portal 2? [[User:Condor70|Condor70]] ([[User talk:Condor70|talk]]) 11:02, 18 February 2016 (UTC)

Maybe the title text is referring to that one multiverse theory where every possible outcome creates it's own timeline? i'm spacing out on it's name right now, but i think it's been mentioned a few times in previous comics.--[[User:Flamewolf|Flamewolf]] ([[User talk:Flamewolf|talk]]) 19:44, 18 February 2016 (UTC)

Regarding the Incomplete reasoning: "There may be another joke here. What about the branches in the title text. Is there some well known reference to such a tree. Sound like something with parallel universes and infinite possibilities?"... I must disagree, there's no other joke here. The word "branch" here isn't referring to any tree, but rather the ongoing logical possibilities of a conversation. If you take a video game where you can chose what you say in a conversation (or the choose-your-own-comic xkcd that came out a while ago), and map out all the options, it would look like a "tree", selecting THIS option leads to a new set of options, each of which will lead to ITS own set of options. In the aforementioned comic, selecting "Let me refresh" in the first panel leads to a different set of options for the second panel than if you had selected something else for the first panel. You are now following the "Let me refresh" branch of the conversation. That's all "branch" means in the title, it's referring to the conversation which would result from this, which would "branch off" of such a declaration. - NiceGuy1[[Special:Contributions/198.41.235.215|198.41.235.215]] 06:22, 20 February 2016 (UTC)

== comic changed ==

The text in the second panel has changed to 'This is andromeda'. Just an fyi. [[Special:Contributions/108.162.216.20|108.162.216.20]] 19:26, 20 February 2016 (UTC)

1642: Gravitational Waves

2016-02-12T12:52:19Z

108.162.216.20: /* Explanation */

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
{{incomplete|I've added some detailed explanation. Someone please proofread / review it. Might need some copy-editing.}}

A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916. Gravitational waves are ripples in the spacetime fabric itself. This comic came out the day after gravitational waves were publicly announced.

The wikipedia article on {{w|gravitational waves}} describes them well. In simpler/layman's terms, imagine moving a stone through water while it is partly submerged. It will cause waves on surface of water as it moves through it. These waves will spread away from the center of disturbance and as they move, they will cause the water molecules to oscilate around their mean positions. Similar waves are created in space-time fabric when two "heavy" celestial bodies interact with each other. If you concentrate on an area of water-surface (analogous to spacetime fabric) far away from the point of disturbance, you can observe that if the wave causes compression in one direction, it'll cause expansion of the fabric in other. See [http://www.einstein-online.info/spotlights/gw_waves this page] for nice animations (as well as {{w|gravitational waves}} wiki page).

Note that anything with a mass will cause a gravitational wave. Just as waves created by small stones are tiny in comparison to waves created by huge rocks in water, the waves from humans moving around will be tiny compared to the waves created by celestial bodies. Also, the bigger the body, the stronger the wave and the farther away the it will travel. That is why we can only detect gravity waves from heavy bodies like black holes / neutron stars but not from us moving around.

Now consider spacetime fabric as a thin rubber sheet. If you mark any two points on this sheet and stretch/compress it along the axis joining those two points, the relative positions of these points with respect to their neighboring points do not change, but the distance between them changes. {{w|LIGO}} (Laser Interferometer Gravitational-Wave Observatory) is a large-scale physics experiment designed to detect this compression/expansion. Two facts need to be remembered to easily understand the experiment. First, speed of light (c) is a constant and velocity of an object is distance divided by time taken to travel that distance. Second, gravitational waves cause opposite effects (compression and expansion) in directions perpendicular to each other. Putting these two together, at {{w|LIGO}}, an experiment is setup, where two perpendicular long tunnels are constructed with apparatus to emit and detect laser beams. The beam from laser is split into those two tunnels, then after going through tunnel and back again (a few times) brought together. Tunnel lengths are set up in such a way, that in the absence of gravity waves, interference between the two combined beams cancels each other out. When the gravitational wave passes through earth, it is expected that the two tunnel lengths will differ due to the expansion/compression effect described above. The interference will be incomplete, and light will not cancel out. This observation can be concluded as "detection of the gravitational wave passing through".

Megan, Cueball, and Ponytail are observing the results from a gravitational wave detector. From the patterns in the gravitational waves detected by this instrument, it might be possible to guess the nature of the event. e.g. Two bodies with dissimilar masses circling a fixed point, two bodies with equal mass circling each other, collision of two massive bodies, etc. It might also be possible to triangulate the location of event. Based on these two facts (location and nature of event) we might be able to determine which astronomical bodies caused this event (and well-being of those bodies afterwards). Thus, it provides an additional medium of observation of universe in addition to our telescopes. And this new medium might enable us to observe properties that we couldn't observe with our rest of the observation instruments.

However, in case of our heroes in this comic, they seem to be able to tell the events that have less to do with astronomical bodies and more with spam messages like invitations from {{w|Linkedin}}, a job networking site, a mortgage offer, and a social meetup. There is also a joke because the '{{w|Local Group}}' is also the technical name for the group of galaxies containing the Milky Way. It is not clear if these so called "events" are causing gravitational waves to be generated or if someone (alien civilization?) is encoding spam messages in gravitational waves. It is plausible that aliens are using gravity waves to encode their messages, since we do something similar with electromagnetic waves to encode and send our messages. Although this it would take an extremely advanced civilization to achieve gravity wave encoding, since it would require them to control orbits and oscillations of super-massive bodies (think at-least on the scale of the Sun, or typically several hundred times bigger than that). The second conclusion (someone is sending spam encoded in gravity waves) seems more plausible since the title text follows this up with a joke that the message senders have gone such a lengths that they caused the most energetic event recorded ever (maybe they blew up few supernovae). One of the receivers is quite impressed with this and suggests that they have to reply to the spam just because the sender has made such an effort to send the message. The other person is not so impressed.

== Explanation of observed events ==

{| class="wikitable"
| | Event
| | Explanation
|-
| | Black hole merger in Carina (30 M☉, 30 M☉)
| |
Possibly legitimate result from the gravitational wave detector. M☉ is a symbol depicting 1 {{w|Solar Mass}} (1.98892×1030 kg). So the statement means that two blackholes, each weighing 30 times our Sun were observed merging in {{w|Carina (constellation)|Carina}}.
|-
| | Zorlax the Mighty would like to connect on Linkedin
| |
A typical LinkedIn request. Not sure who is Zorlax (the mighty one), but according to title text, he set the record for the most energetic physical event ever observed. He might be looking for a job and this might be him demonstrating (showing-off) his mighty powers instead of simply attaching a resume or filling up his profile. Also, this either means that LinkedIn has now grown outside the Earth, or the Zorlax guy wants to have a job on Earth.
|-
| | Black hole merger in Orion (20 M☉, 50 M☉)
| |
Again a possibly legitimate observation from the gravitational wave detector. It detected blackhole merger of two bodies. One of them is 20 times heavier than Sun, the other is 50 times heavier than the Sun. Both of them are located in {{w|Orion (constellation)|Orion}}.
|-
| | Mortgage offer from Triangulum Galaxy
| |
{{w|Triangulum Galaxy}}, also known as Pinwheel Galaxy is a spiral galaxy approximately 3 million light-years from Earth. It is not clear if the offer is for a house on Earth or if the advertisers want us to buy house in the Triangulum Galaxy. Either way, unless we humans develop a {{w|Wormhole}} or {{w|Faster-than-light}} travel, we may not be able to take up the offer, even if it is legit.
|-
| | Zorlax the Mighty would like to connect on Linkedin
| |
Same guy who sent us LinkedIn invite moments ago. The dude seems desperate.
|-
| | Meet lonely singles in the local group tonight!
| |
The space advertisers are using space-GeoIP technology on a galactic scale to send spam. {{w|Local Group}} is the technical term for group of close-by galaxies that also includes {{w|Milky Way}} (our galaxy). There are more than 54 galaxies and few other celestial objects in the local group. {{w|Local Group}} along with several other local groups form {{w|Virgo Supercluster}}. So, it seems that the advertiser might be targetting ads to everyone in the Virgo Supercluster. However, finding "lonely singles" in 54 galaxies within our local group might be easier said than done for humans here on Earth. This kind of spam was previously joked with in [[713: GeoIP]].
|}

== Trivia ==

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century announcement of the discovery of a clear gravitational wave signal] on February 11, 2016. Gravitational waves were detected through the collision of 2 black holes.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! For the first time, we can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 M☉, 30 M☉)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20 M☉, 50 M☉)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-12T12:50:48Z

108.162.216.20: /* Explanation */

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
{{incomplete|I've added some detailed explanation. Someone please proofread / review it. Might need some copy-editing.}}

A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916. Gravitational waves are ripples in the spacetime fabric itself. This comic came out the day after gravitational waves were publicly announced.

The wikipedia article on {{w|gravitational waves}} describes them well. In simpler/layman's terms, imagine moving a stone through water while it is partly submerged. It will cause waves on surface of water as it moves through it. These waves will spread away from the center of disturbance and as they move, they will cause the water molecules to oscilate around their mean positions. Similar waves are created in space-time fabric when two "heavy" celestial bodies interact with each other. If you concentrate on an area of water-surface (analogous to spacetime fabric) far away from the point of disturbance, you can observe that if the wave causes compression in one direction, it'll cause expansion of the fabric in other. See [http://www.einstein-online.info/spotlights/gw_waves this page] for nice animations (as well as {{w|gravitational waves}} wiki page).

Note that anything with a mass will cause a gravitational wave. Just as waves created by small stones are tiny in comparison to waves created by huge rocks in water, the waves from humans moving around will be tiny compared to the waves created by celestial bodies. Also, the bigger the body, the stronger the wave and the farther away the it will travel. That is why we can only detect gravity waves from heavy bodies like black holes / neutron stars but not from us moving around.

Now consider spacetime fabric as a thin rubber sheet. If you mark any two points on this sheet and stretch/compress it along the axis joining those two points, the relative positions of these points with respect to their neighboring points do not change, but the distance between them changes. {{w|LIGO}} (Laser Interferometer Gravitational-Wave Observatory) is a large-scale physics experiment designed to detect this compression/expansion. Two facts need to be remembered to easily understand the experiment. First, speed of light (c) is a constant and velocity of an object is distance divided by time taken to travel that distance. Second, gravitational waves cause opposite effects (compression and expansion) in directions perpendicular to each other. Putting these two together, at {{w|LIGO}}, an experiment is setup, where two perpendicular long tunnels are constructed with apparatus to emit and detect laser beams. The beam from laser is split into those two tunnels, then after going through tunnel and back again (a few times) brought together. Tunnel lengths are set up in such a way, that in absence of gravity waves, interference between two combined beams cancels them out. When the gravitational wave passes through earth, it is expected that the two tunnel lengths will differ due to the expansion/compression effect described above. The interference will be incomplete, and light would not cancel out. This observation can be concluded as "detection of the gravitational wave passing through".

Megan, Cueball, and Ponytail are observing the results from a gravitational wave detector. From the patterns in the gravitational waves detected by this instrument, it might be possible to guess the nature of the event. e.g. Two bodies with dissimilar masses circling a fixed point, two bodies with equal mass circling each other, collision of two massive bodies, etc. It might also be possible to triangulate the location of event. Based on these two facts (location and nature of event) we might be able to determine which astronomical bodies caused this event (and well-being of those bodies afterwards). Thus, it provides an additional medium of observation of universe in addition to our telescopes. And this new medium might enable us to observe properties that we couldn't observe with our rest of the observation instruments.

However, in case of our heroes in this comic, they seem to be able to tell the events that have less to do with astronomical bodies and more with spam messages like invitations from {{w|Linkedin}}, a job networking site, a mortgage offer, and a social meetup. There is also a joke because the '{{w|Local Group}}' is also the technical name for the group of galaxies containing the Milky Way. It is not clear if these so called "events" are causing gravitational waves to be generated or if someone (alien civilization?) is encoding spam messages in gravitational waves. It is plausible that aliens are using gravity waves to encode their messages, since we do something similar with electromagnetic waves to encode and send our messages. Although this it would take an extremely advanced civilization to achieve gravity wave encoding, since it would require them to control orbits and oscillations of super-massive bodies (think at-least on the scale of the Sun, or typically several hundred times bigger than that). The second conclusion (someone is sending spam encoded in gravity waves) seems more plausible since the title text follows this up with a joke that the message senders have gone such a lengths that they caused the most energetic event recorded ever (maybe they blew up few supernovae). One of the receivers is quite impressed with this and suggests that they have to reply to the spam just because the sender has made such an effort to send the message. The other person is not so impressed.

== Explanation of observed events ==

{| class="wikitable"
| | Event
| | Explanation
|-
| | Black hole merger in Carina (30 M☉, 30 M☉)
| |
Possibly legitimate result from the gravitational wave detector. M☉ is a symbol depicting 1 {{w|Solar Mass}} (1.98892×1030 kg). So the statement means that two blackholes, each weighing 30 times our Sun were observed merging in {{w|Carina (constellation)|Carina}}.
|-
| | Zorlax the Mighty would like to connect on Linkedin
| |
A typical LinkedIn request. Not sure who is Zorlax (the mighty one), but according to title text, he set the record for the most energetic physical event ever observed. He might be looking for a job and this might be him demonstrating (showing-off) his mighty powers instead of simply attaching a resume or filling up his profile. Also, this either means that LinkedIn has now grown outside the Earth, or the Zorlax guy wants to have a job on Earth.
|-
| | Black hole merger in Orion (20 M☉, 50 M☉)
| |
Again a possibly legitimate observation from the gravitational wave detector. It detected blackhole merger of two bodies. One of them is 20 times heavier than Sun, the other is 50 times heavier than the Sun. Both of them are located in {{w|Orion (constellation)|Orion}}.
|-
| | Mortgage offer from Triangulum Galaxy
| |
{{w|Triangulum Galaxy}}, also known as Pinwheel Galaxy is a spiral galaxy approximately 3 million light-years from Earth. It is not clear if the offer is for a house on Earth or if the advertisers want us to buy house in the Triangulum Galaxy. Either way, unless we humans develop a {{w|Wormhole}} or {{w|Faster-than-light}} travel, we may not be able to take up the offer, even if it is legit.
|-
| | Zorlax the Mighty would like to connect on Linkedin
| |
Same guy who sent us LinkedIn invite moments ago. The dude seems desperate.
|-
| | Meet lonely singles in the local group tonight!
| |
The space advertisers are using space-GeoIP technology on a galactic scale to send spam. {{w|Local Group}} is the technical term for group of close-by galaxies that also includes {{w|Milky Way}} (our galaxy). There are more than 54 galaxies and few other celestial objects in the local group. {{w|Local Group}} along with several other local groups form {{w|Virgo Supercluster}}. So, it seems that the advertiser might be targetting ads to everyone in the Virgo Supercluster. However, finding "lonely singles" in 54 galaxies within our local group might be easier said than done for humans here on Earth. This kind of spam was previously joked with in [[713: GeoIP]].
|}

== Trivia ==

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century announcement of the discovery of a clear gravitational wave signal] on February 11, 2016. Gravitational waves were detected through the collision of 2 black holes.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! For the first time, we can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 M☉, 30 M☉)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20 M☉, 50 M☉)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1587: Food Rule

2015-10-07T14:45:57Z

108.162.216.20:

{{comic
| number = 1587
| date = October 7, 2015
| title = Food Rule
| image = food_rule.png
| titletext = I won't eat invertebrates, because I can fight a skeleton, but I have no idea what kind of spooky warrior a squid leaves behind.
}}

==Explanation==
There are various {{w|Vegetarianism|vegetarian}} diets which restrict certain foods for ethical concerns. A {{w|Pescetarianism|pescatarian}} diet omits most sources of meat, but still allows for fish. One rationale for this choice is that fish have a less complex nervous system, and thus experience a narrower range of suffering when farmed. An {{w|Ovo-lacto_vegetarianism|ovo-lacto vegetarian}} will not eat meat, but may consume animal byproducts such as milk, egg, cheese, and honey. A {{w|Veganism|vegan}} diet excludes all animal products entirely. Some vegetarians choose to summarize their eating habits in one sentence, like eating "nothing that once had a heartbeat", "nothing that can have children", "nothing with eyes" or "[https://www.google.dk/search?sourceid=navclient&aq=&oq=%22nothing+with+a+face%22&hl=da&ie=UTF-8&rlz=1T4GGHP_daDK541DK548&q=%22nothing+with+a+face%22&gs_l=hp...0i22i10i30j0i22i30l4.0.0.1.642912...........0.VML4AzjfqPA#hl=da&q=don%27t+eat+anything+with+a+face nothing with a face]" - this last example being the subject of the comic.

[[Randall]] presents two rules about what can be eaten (one in caption below the frame comic and one in the title text). He also presents a list of allowed and forbidden foods but not all of the forbidden foods matches both rules.

Randall is willing to eat food disregarding if it once had a {{w|face}} or not. But his rule in the caption states that he will not eat any food if he needs to use Google to figure out whether it came from something who had a face or not. While it's clear that a cow has a face{{Citation needed}} and an apple does not, some beings are harder to classify into one of these categories. For example, the {{w|squid}} has eyes and mouth, but it would be hard to tell whether that counts as a face. This would be a problem for the vegetarian standard rule of "nothing without a face" and thus openly mocks the vegetarian rule of "nothing with a face". However, {{w|oysters}} definitely have no faces, so the rule can not explain why he does not eat these. And he would not need Google to check this. Also he does know what a squid and a {{w|shrimp}} is, so he would also not need Google to investigate these. Of course it may be discussed on-line if a squid has a face or nor... He could find such a discussion using Google. So the first rule cannot explain Oysters at all and may also not explain the other two forbidden items.

The three omissions are explained by the rule given in the title text. This rule is about not eating {{w|Invertebrate|invertebrates}}. The first four items on the list are meat from four different animals of the type {{w|Vertebrate|vertebrates}} and the last three items are from {{w|Plant|plants}}. These are all OK to eat. But the middle three items are three different animals of the type invertebrates. Randall does not eat these! Specifically they all fit under the term {{w|shellfish}}, which {{w|Jews}} are {{w|Jewish dietary laws|not allowed to eat}}. However, since {{w|pork}} is also not allowed for Jews, this list is not useful for them.

These animals do not have any skeleton. Randall is joking about how the animals he eats might come back to haunt him, and in the case of a cow or fish (or any other vertebrates - with skeletons), he imagines that they would come back as an animated skeletal structure. Any undead creature that returns as a skeleton he believes he will be able to fight. But since he has no idea how an undead squid or oyster (or any other invertebrate) would look, he feels unprepared to fight such a spooky creature and thus declines from eating them. This may be an excuse for not eating certain invertebrate, or a mocking comment on several games where the protagonist is required to fight several animated human skeletons.

Randall has previously mentioned his dislike of certain foods (namely lobster) in [[1268: Alternate Universe]].

===Items on the list===
Here is a list with explanation for each item:
*{{w|Red meat}}, includes meat from most adult {{w|mammals}}, but many people will probably think of {{w|beefsteak}} from {{w|cattle}}.
*{{w|Pork}}, is meat from from {{w|Domestic pig|pigs}}. As this is actually a type of red meat this supports that Randall was thinking of beef, when mentioning red meat above.
*{{w|Poultry}} are domesticated birds, most people will think of {{w| Chicken (food)|chicken}}.
*{{w|Fish}} covers a very large group of animals, most of them are not eaten on a regular basis, but a large group of fish are {{w| Fish as food|used as food}}.
*{{w|Shrimp}} is used to refer to {{w|Decapoda|ten-footed}} {{w|Crustacean}} and some of these are {{w|Shrimp (food)|used for food}}. (In the UK they often go under the name {{w|Prawns}}).
*{{w|Oysters}} refers to a family of {{w|mollusca}} within the class {{w|bivalvia}} (i.e. body enclosed in shells consisting of two hinged parts). Most people will probably think of the {{w|Ostreidae|true oysters}} specifically the {{w|Ostrea edulis|edible oyster}}. Note that {{w| Pearl oyster}} is not a true oyster.
*{{w|Squid}} are {{w|cephalopods}} (also of the mollusca family ) with eight arms arranged in pairs and two longer tentacles. They are related to {{w|cuttlefish}} and {{w|octopuses}}.
*{{w|Fruit}} is a part of a flowering plant. Common fruits are {{w|apples}}, {{w|oranges}}, {{w|bananas}} and {{w|pear|pears}}. But in principle anything that comes from a flower is a fruit, including grains. Although in a culinary sense there is a distinction between vegetables and fruit, any part of a flower is actually a vegetable. See below and also see [[388: Fuck Grapefruit]].
*{{w|Vegetables}} are any kind of plant. But in everyday it refers to any part of a plant that is consumed by humans as food as part of a {{w|Umami|savoury}} meal. Thus excluding both fruit, {{w|Nut (fruit)|nuts}} and cereal grains. For instance a {{w|tomato}} would be seen as a vegetable due to its taste and as a fruit botanically – see the Venn diagram {{w|Fruit#Botanic fruit and culinary fruit|here}}.
*{{w|Grain|Grains}} are small, hard, dry {{w|seeds}}. Usually when mentioning these people will think of breakfast {{w|cereal}} grains. Typical grains are {{w|corn}}, {{w|rice}} and {{w|wheat}}. As mentioned above grains are botanically a fruit.

==Transcript==
:[There is a caption above a list of food with indication whether it is OK or not to eat. Below is another caption.]

:My food rule:
:{| class="wikitable" style="border: 0px;"
|-
| style="border: 0px; text-align: right" | Red meat
| style="border: 0px; color:green;" | ✓
|-
| style="border: 0px; text-align: right" | Pork
| style="border: 0px; color:green;" | ✓
|-
| style="border: 0px; text-align: right" | Poultry
| style="border: 0px; color:green;" | ✓
|-
| style="border: 0px; text-align: right" | Fish
| style="border: 0px; color:green;" | ✓
|-
| style="border: 0px; text-align: right" | Shrimp
| style="border: 0px; color:red;" | X
|-
| style="border: 0px; text-align: right" | Oysters
| style="border: 0px; color:red;" | X
|-
| style="border: 0px; text-align: right" | Squid
| style="border: 0px; color:red;" | X
|-
| style="border: 0px; text-align: right" | Fruit
| style="border: 0px; color:green;" | ✓
|-
| style="border: 0px; text-align: right" | Vegetables
| style="border: 0px; color:green;" | ✓
|-
| style="border: 0px; text-align: right" | Grains
| style="border: 0px; color:green;" | ✓
|}
:I won't eat something
:if I have to Google
:to figure out whether
:or not it has a face.

{{comic discussion}}

[[Category:Charts]]

Talk:383: Helping

2015-03-28T02:25:14Z

108.162.216.20:

Most depressing XKCD ever? [[Special:Contributions/71.201.53.130|71.201.53.130]] 14:24, 22 August 2013 (UTC)
:Every time when I see this comic I'm close before some tear drops running out of my eyes ;( --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:42, 9 December 2013 (UTC)

Waitwaitwait. So the guy was in the building all along, witnessing the suicide/self-harm, and he failed to stop a woman from apparently successfully knocking herself out? 16:19, 24 May 2014 (UTC) {{unsigned ip|141.101.88.205}}

I thought Cueball was choking her![[Special:Contributions/108.162.238.169|108.162.238.169]]
I thought maybe it was about Randall's wife. Just like some of the comics feature her implicitly, I thought maybe this one did.