explain xkcd - User contributions [en]

Talk:2641: Mouse Turbines

2022-07-06T03:28:24Z

172.68.133.159: Lol

Is anybody going to try to calculate the amount of power such a turbine could collect? -- [[User:Dtgriscom|Dtgriscom]] ([[User talk:Dtgriscom|talk]]) 19:24, 4 July 2022 (UTC)
:Good idea; what should we use for an estimate of the geometry for https://www.omnicalculator.com/ecology/wind-turbine ? The final panel makes it look like the blade diameter is about twice the size of a fist. [https://www.sciencedirect.com/science/article/pii/S2215098616300830] says "exhaled air velocity varies from 2.2 m/s to 9.9 m/s (5.66 ± 1.57 m/s, mean ± SD) and exhalation time varies from 2.10 s to 8.21 s (4.42 ± 1.73s, mean ± SD)."
:I guessed 10 cm radius and used that mean breath speed. I should have used the top 9.9 m/s though, shouldn't I? [[Special:Contributions/172.70.214.185|172.70.214.185]] 20:56, 4 July 2022 (UTC)
:After a closer look at that article, the mean is more appropriate. [[Special:Contributions/172.70.206.95|172.70.206.95]] 21:19, 4 July 2022 (UTC)

Although these miniscule wind turbines don't generate much power, mice probably don't need much. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 21:17, 4 July 2022 (UTC)
:That's certainly a fair point. How much power would a mouse-sized fridge need? [[Special:Contributions/172.70.206.95|172.70.206.95]] 21:23, 4 July 2022 (UTC)
::Mice consume a lot more food per body weight (especially for body heat because heat transfer scales with surface area, not mass/volume) than humans. Mouse-sized fridge efficiency would also be poor both because of the same size issue and reduced room for insulation. [[User:627235|627235]] ([[User talk:627235|talk]]) 11:13, 5 July 2022 (UTC)
::A 480 ml insulin travel fridge uses 5 watts on a 3% duty cycle depending on the ambient temperature and how much it's loaded, so that's in the realm of possibility, and seems large enough. I used to feed lab mice about 5 grams of Purina Lab Rodent Chow daily, which was maybe 8ml volume, but it doesn't need to be refrigerated. Googling suggests field mice can get all the water they need from a diet of seeds. It seems to me that if mice could use electricity, they'd need it more in the winter than the summer. [[Special:Contributions/172.70.211.52|172.70.211.52]] 22:01, 5 July 2022 (UTC)

Someone please check my mouse energy needs math and assumptions. I made a couple misplaced decimal mistakes getting to where it is now, and I'm going to have another beer. [[Special:Contributions/172.70.211.52|172.70.211.52]] 22:17, 4 July 2022 (UTC)
:Not sure about numbers but some (if not most) energy requirements scale by surface area ({{w|Square–cube law}} or other measurements. There are also efficiency issues with at least lots of human-made miniature machines. [[User:627235|627235]] ([[User talk:627235|talk]]) 11:13, 5 July 2022 (UTC)
::What energy requirements scale by surface area? Pumping water, cooking, and refrigerating scales by mass. Converting footcandles to lumens depends on area, but that doesn't account for much lower mouse ceilings. [[Special:Contributions/172.69.34.6|172.69.34.6]] 22:27, 5 July 2022 (UTC)

I'm confused by the statement that smaller turbines are less "efficient". There's nothing about efficiency at that link. [[Special:Contributions/172.70.114.43|172.70.114.43]] 22:33, 4 July 2022 (UTC)
:The graph shows the ratio between size and output has risen from about half to 85%. What is a better term for this? I'm pretty sure one of the multiple definitions of efficiency is technically correct, but it can never hurt explaining better. [[Special:Contributions/172.69.33.113|172.69.33.113]] 22:42, 4 July 2022 (UTC)
:Changed to "relative power output" but I'm not sure that captures the idea very well either. [[Special:Contributions/172.69.33.113|172.69.33.113]] 22:44, 4 July 2022 (UTC)

Well wind turbines may not scale down ideally but still better than nuclear power plants. I suspect those have fixed minimal size and it's pretty big. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 23:32, 4 July 2022 (UTC)

:Apparently nuclear power can be [https://technology.nasa.gov/patent/LAR-TOPS-294 "as small as a button cell"] but mice are vulnerable to radioactive hazards, and haven't solved the waste disposal problem. [[Special:Contributions/172.70.214.185|172.70.214.185]] 23:45, 4 July 2022 (UTC)

Isn't the power output of a solar panel directly dependent on its size (and wether it's covered with snow, angle to the sun, clouds? And prolly something I'll think of as soon as I hit save).[[Special:Contributions/172.70.131.106|172.70.131.106]] 23:55, 4 July 2022 (UTC)
:Yes, but the power per size doesn't increase with size like wind turbines do. [[Special:Contributions/172.69.33.63|172.69.33.63]] 00:01, 5 July 2022 (UTC)

What is the smallest Tesla Powerwall available for purchase? [[Special:Contributions/172.70.206.163|172.70.206.163]] 02:00, 5 July 2022 (UTC)
:You probably want an {{w|18650}} or similar cell, which are [https://www.youtube.com/watch?v=PsJMj7FtroY frequently discarded on the street] and thus easily obtainable by mice. [[Special:Contributions/172.69.33.171|172.69.33.171]] 03:02, 5 July 2022 (UTC)

Why doesn't pico hydro have the same problems scaling down as wind? They're both fluid turbines. [[Special:Contributions/172.70.214.185|172.70.214.185]] 02:24, 5 July 2022 (UTC)
:For the same reasons that small fans have several vanes, but large wind turbines have only three. I remember reading something about the physics (it's a laminar versus turbulent thing) but I can't remember the details now. I'll update here if I can find it. [[Special:Contributions/172.70.210.125|172.70.210.125]] 03:08, 5 July 2022 (UTC)
:[https://www.sciencefocus.com/science/why-do-wind-turbines-have-three-blades/ Here's part of it,] but doesn't really get to the heart of the matter. [[Special:Contributions/172.70.210.125|172.70.210.125]] 03:10, 5 July 2022 (UTC)
:I think it has more to do with the relative magnitude of drag in gases instead of liquids. I don't have a good source though. [[Special:Contributions/172.70.211.36|172.70.211.36]] 03:21, 5 July 2022 (UTC)
::Turbine efficiency (especially for very small turbines) mostly depends on pressure differential and mass throughput. Water has three orders of magnitude higher density than air. Also, even with just a meter of water column, water offers a 10 kPa pressure differential while you only rarely get that much of a pressure differential in air (at the same height) even between areas of high and low pressure usually at least dozens (and commonly hundreds) of miles apart (there may be exceptions for things like tornadoes but good luck using their wind power), certainly not between the high and low pressure sides of a turbine. Efficiency in practice mostly depends on moved mass (of turbine blades, etc) compared to moved medium (water or air), friction (mount, generator, maybe a gearbox) compared to total power input and (if electricity is desired) generator efficiency which itself depends on generator size and rotation speed (hence the need for a gearbox). For a very small turbine, all those things would need to be extremely light as well. [[User:627235|627235]] ([[User talk:627235|talk]]) 11:13, 5 July 2022 (UTC)

Who is Beret Guy telling to make a wish - Megan or the mice? -- [[User:Ken g6|Ken g6]] ([[User talk:Ken g6|talk]]) 04:48, 5 July 2022 (UTC)

[https://www.cornel1801.com/animated/Secret-of-NIMH-1982/pictures/64.jpg I must tell you about NIMH.] - [[Special:Contributions/172.70.254.81|172.70.254.81]] 16:13, 5 July 2022 (UTC)

Sometimes the explanation is funnier than the comic. [[Special:Contributions/172.68.133.159|172.68.133.159]] 03:28, 6 July 2022 (UTC)

2203: Prescience

2022-04-02T06:48:31Z

172.68.133.159: /* Explanation */

{{comic
| number = 2203
| date = September 16, 2019
| title = Prescience
| image = prescience.png
| titletext = Lots of people called their ships unsinkable before the Titanic. Voicing your hubris doesn't make failure more likely, just more memorable.
}}

==Explanation==

In this comic, [[Cueball]] states that it's been a long time since there's been a really big {{w|Impact event|meteor impact}}. Due to the {{w|Gambler's Fallacy}}, this is taken to be Cueball implying that a big meteor impact is coming soon. The off-panel voice is annoyed about his statement, but whether from fear of it happening or because he does this all the time is unclear, see more below. The joke is that Cueball does this often, also with other types of major random events, just in case they do actually happen soon. For instance, if there does happen to be an impact soon after he made the statement, it makes him look incredibly {{w|prescient}}, whereas if there isn't one, no one really cares or remembers.

It is also unclear how big an impact he refers to. It has been 60 million years since the {{w|Cretaceous–Paleogene extinction event|impact that killed the dinosaurs}}, but that if that is the type of event he refers to, then maybe no one will be there to remember what he said. So it is likely much smaller impacts he is talking about.

''Prescience'' means to predict the future. It is clear from this comic that [[Randall]] makes fun of both of those that claim to have prescience and of those that have a superstition against talking about something happening that could cause it to happen.

Although only one method is scientifically recognized, there are at least three possible sources of prescience recognized by people.

The first of the two main ways of predicting the future involves a mix of common sense and historical knowledge. By understanding the past, the direction of the future can be guessed at with varying levels of accuracy. This type of prescience is also known sometimes as future modeling, statistical prediction, and even wisdom to name a few.

The second way to predict the future is not scientifically recognized but remains popular in culture and fiction. It can involve magic, psychic power, higher powers (gods), and other such methods. Collectively, they are labeled supernatural; any method to predict the future using this class of method cannot be easily measured by science.

Although not technically a way to predict the future, the third way to predict the future is through superstition. The method involved in this comic effectively boils down to "speak the name of evil, and you will summon it." This superstition can have surprising power in people's lives, however. A woman planning her outdoor wedding may feel the urge to hit her friend if they say "Gosh, I hope it doesn't rain on that day." A doctor working in the Emergency Room may feel the need to kick anyone who says "Wow, it's really quiet around here." Such thoughts spoken aloud do not have the power to control the weather or cause people to seriously injure themselves. Yet people often react emotionally as if not speaking the name of 'evil' will keep it away.

This comic may reflect that emotional reaction when the off-screen character yells at Cueball: "Will you stop that?!". Alternatively, it is one, like [[Megan]], who knows Cueball well enough to know that which is stated in the caption, that he only does this to look good if said thing happens. And the person is so tired of it! Maybe Cueball does it at least once a week, and obviously from the caption, it is not only about meteor impact, but any major random event, that he could then be remembered as having predicted.

The title, Prescience, has a double meaning. The first meaning is about the prescience that would appear if one actually predicts a natural disaster this way. The second meaning involves the fact that it is spelled pre-science - since there are many more scientific ways to predict meteor impacts, even though they aren't entirely accurate.

The title text refers to the {{w|RMS Titanic|RMS ''Titanic''}}, a ship which was claimed to be unsinkable by those promoting its maiden voyage. But then it struck an iceberg in an unfortunate way so more compartments would be filled with water that it could survive, and of course, it could sink. But with all the new stories that had just been published hailing this unsinkable ship as a modern wonder of the world, this shipwreck was particularly ironic. The story of the sinking of the ''Titanic'' has been memorialized in popular culture, most memorably in the 1997 film {{w|Titanic (1997 film)|Titanic}}.

In the title text, Randall thus suggests that lots of ships had been called unsinkable before Titanic. But saying such {{w|hubris}} out loud doesn't make any ship more likely to sink. But when such a ship, like Titanic, then sinks it does, however, increase the value of the story ensuring it will be remembered.

It should be noted that few among the ship's builders or crew boasted the ''Titanic'' to be unsinkable. Most of the boasting came from the owners that used the news media to create hype and promote the ship, just when the ship was finished and dedicated (the ship's builders did, however, boast that the ship exceeded all safety standards of the time). In addition, the hubris was only one small part of the fame of the sinking of the ''Titanic''; the ''Titanic'''s status as a world record setter for most massive ship ever built, the incredible wealth of most of its passengers, and the fact it sank on its maiden voyage all contributed to the fame and hype behind the great maritime tragedy. Ironically part of what caused this disaster was hubris since those that were interested in promoting the ship also wished it to make another record, reaching New York a day before expected. Thus the captain, even though he for sure knew that the ship could sink took some fateful decisions of running at full speed through waters with icebergs during a night with very calm waters, which is known to make spotting icebergs more difficult as there will be no waves with foam around the iceberg's base as there would have been in less calm waters.

==Transcript==
:[Cueball is sitting in an armchair holding a book. He seems to be looking off as he talks to an off-panel person behind him. This person replies.]
:Cueball: You know, it's been a while since there's been a really big meteor impact.
:Off-panel voice: '''''Will you stop that?!'''''

:[Caption below the panel:]
:I say this kind of thing every so often, because I don't believe it affects the outcome and it has a slim chance of looking ''incredibly'' prescient.

==Trivia==
*This comic has a clear resemblance to the [[:Category:My Hobby|My Hobby]] series. This would also make it clear the Cueball in this comic is actually [[Randall]].
*The entire setup and punch line of this comic is very similar to this old comic: [[525: I Know You're Listening]].
*Also [[628: Psychic]] and [[858: Milk]] use the idea of guessing something that will make you look special.

{{comic discussion}}

[[Category:Comics featuring Cueball]]