explain xkcd - User contributions [en]

2201: Foucault Pendulum

2019-09-12T00:54:42Z

162.158.6.238: /* Explanation */ wlink

{{comic
| number = 2201
| date = September 11, 2019
| title = Foucault Pendulum
| image = foucault_pendulum.png
| titletext = Trust me, you don't want to get on the wrong side of the paramilitary enforcement arm of the International Earth Rotation and Reference Systems Service.
}}

==Explanation==
{{incomplete|Created by the International Earth Rotation and Reference Systems Service. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
[[Black Hat]] is attending what appears to be a physics lecture. The professor, [[Megan]], is talking about the {{w|Foucault pendulum}}, a device which demonstrates the rotation of the Earth. Black Hat, being himself, sees an opportunity to cause chaos and seizes it with both hands, quite literally - that is, he grabs the pendulum. The professor objects strongly to this, seemingly for fear of ruining the delicate demonstration. However, the news anchor in the final panel reveals to us that by arresting the motion of the pendulum, Black Hat has somehow stopped the rotation of the Earth. This of course is blatantly impossible since the Foucault pendulum's motion is tied to the earth's rotation, not the other way around. {{Citation needed}}

A Foucault pendulum swings from a bearing that allows rotation in any direction, like your shoulder joint instead of your elbow. If the Earth were stationary, it would continue to swing in the same plane as when it was released. However, because the Earth moves beneath it, over the course of the day the pendulum's motion gradually changes direction relative to the room. The low-resistance bearing doesn't allow the rotation of the Earth to affect the motion of the pendulum, so it stays aligned to its original inertial reference frame rather than the rotating one of the Earth.

The fact that the Earth's rotation does not influence the motion of the pendulum does NOT mean that other things can't affect it - for example, by running up and manually repositioning the pendulum. Of course, the apparent rotation of the pendulum's plane relative to the Earth is an effect of the planet's motion, rather than the cause of it. Thus, stopping a Foucault pendulum manually does not entail pausing the rotation of the Earth.

If it were somehow possible for a Foucault pendulum to control Earth's rotation, Black Hat would probably not want to alter the momentum of the pendulum, unlike most cases where he causes chaos (assuming he was told that it was related to Earth's rotation and assuming that he would prefer to preserve his own life over making chaos). The reason why is because if the rotation of Earth were to be stopped for even very short amounts of time (a few seconds), it would cause everything on Earth that wasn't bolted/fastened to the ground to be sent flying eastward (assuming they are near the Equator) at a speed of 300-360 meters per second, likely causing the death of most lifeforms on Earth within an hour or less, and causing massive windstorms and weather events on a scale not previously observed on Earth. This would likely cause a mass extinction event and wipe out ~90% of humanity. It is possible that Black Hat's grabbing the pendulum would cause a gradual slowing prior to stopping, minimizing the issue, but the results would still be catastrophic.

Randall covered this scenario in detail in his [https://io9.gizmodo.com/xkcds-creator-explains-what-would-happen-if-earth-stopp-1625068208 What If] book.

The title text refers to a (probably) fictional paramilitary enforcement arm of the [https://www.iers.org/IERS/EN/Home/home_node.html International Earth Rotation and Reference Systems Service] and the foolishness of tangling with such a force. If Foucault pendulums were somehow able to influence the rotation of the Earth in any measurable way, the IERS enforcers would probably strictly control their installation and monitor their use (and misuse). Black Hat is likely in for a rough day.

==Trivia==
The Foucault Pendulum in this comic strongly resembles that in the Museum of Science in Boston (both in shape and the way it is knocking over the pegs)

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

[Cueball, Black Hat, Ponytail, and Megan are standing next to a large swinging sphere on a pendulum with markers under it; Megan is pointing at it.]

Megan: This Foucault pendulum demonstrates Earth's rotation. It stays in a fixed plane while the Earth rotates under it.

[Close-up on Black Hat]

Black Hat: Hmm, really. So that means...

[Close-up on Black Hat and pendulum; Black Hat grabs pendulum, and a line points from the pendulum saying "GRAB!"]

Character out of panel: Hey!

Character out of panel: Stop him!

[Blondie is standing next to Black Hat's picture in an inset frame, captioned with "BREAKING NEWS."]

News Anchor: The Earth's rotation was briefly halted today until geophysicists wrestled the intruder to the ground...

{{comic discussion}}

Talk:1339: When You Assume

2015-08-31T04:14:38Z

162.158.6.238:

This explanation is most certainly correct. A quick google search will prove as much. [[User:ImVeryAngryItsNotButter|ImVeryAngryItsNotButter]] ([[User talk:ImVeryAngryItsNotButter|talk]]) 15:19, 8 March 2014 (UTC)

The explanation may sound better if the "assert" in Cueball response is also stressed. In fact, we may suppose that Megan IS the emergency response team, from the starting of the dialog, and the history of the comics. Cueball just did some stupid thing because he assumed something, and the specialist came to fix it. [[Special:Contributions/162.158.6.238|162.158.6.238]] 04:14, 31 August 2015 (UTC)

[[User:Tesshavon|Tesshavon]] ([[User talk:Tesshavon|talk]]) 09:11, 7 March 2014 (UTC) this is a direct reference to the popular saying 'When you ASSUME, you make an ASS out of U and ME'.
:: My donkey is behind a donkey, I am behind my donkey, my entire country is behind me! [[Special:Contributions/141.101.99.7|141.101.99.7]] 05:20, 9 March 2014 (UTC)

I'm not a native English speaker, and I'm just curious. Is there any popular saying about ass-ass-inating someone? [[Special:Contributions/173.245.53.161|173.245.53.161]] 10:25, 7 March 2014 (UTC)
:To the best of my knowledge, there is no such saying, but I'm sure it's a spelling mnemonic used by many. [[User:Jameslucas|jameslucas]] <small>([[User talk:Jameslucas|" "]] / [[Special:Contributions/Jameslucas|+]])</small> 14:18, 7 March 2014 (UTC)

:I have read of badly programed profanity filters that change "assassin" to "buttbuttin". It's a clbuttic mistake. [[Special:Contributions/108.162.250.220|108.162.250.220]] 13:22, 8 March 2014 (UTC)

::Funny that such profanity filters are the ones who gave me the idea of asking. I first heard about them in [http://www.thisistrue.com/blog-2008s_weirdest_stories.html This Is True] (search for "How Embarrbutting" in that page), who took it from The London Telegraph. [[Special:Contributions/173.245.53.161|173.245.53.161]] 15:24, 10 March 2014 (UTC)

Assert is also used in programming (c and such) [[Special:Contributions/108.162.241.11|108.162.241.11]] 13:35, 7 March 2014 (UTC)
::And Python, which I was hacking in yesterday, so that came to my mind. But Randall isn't distracting us with any assert + throw unhandled exception jokes today. — ''[[User:Tbc|tbc]] ([[User talk:Tbc|talk]]) 15:31, 8 March 2014 (UTC)''

Thank goodness for the 'ERT' explanation; I had terrible notions of a [[739: Malamanteau|portmanteau]] involving 'insert'. [[User:Jameslucas|jameslucas]] <small>([[User talk:Jameslucas|" "]] / [[Special:Contributions/Jameslucas|+]])</small> 14:16, 7 March 2014 (UTC)

If Megan was going to phrase it like "You know what happens when you assume something? You make an ass out of you and me.", then she wouldn't be assuming anything. Of course, in spoken English, you could determine which one it is through inflection. Maybe Randall could start making voice-overs for the comics. [[Special:Contributions/103.22.200.80|103.22.200.80]] 18:33, 7 March 2014 (UTC)

Strictly speaking, Megan is asking a rhetorical question; one that she intends to answer herself. However, I once had a dickhead manager try this one on me, so I fully support this comic. [[Special:Contributions/108.162.215.56|108.162.215.56]] 20:32, 7 March 2014 (UTC)

;This comic explain needs some enhancements!!!
xkcd is a webcomic "A webcomic of romance, sarcasm, math, and '''language'''." There is definitively no ASS here, or ERT... That could be mentioned at trivia, not more. This is all about language — assuming vs. asserting — not more or less. Everything more interpretations are like hearing a message by playing a song backwards. This explain isn't incomplete — it's incorrect! --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:21, 7 March 2014 (UTC)
:Um, the explanation is fine. The cheesy "ass" + "u" + "me" pun is well-known, and the comic is quite specifically riffing on it. No pareidolia here. [[Special:Contributions/199.27.128.72|199.27.128.72]] 23:20, 7 March 2014 (UTC)

I saw it as that Megan was on an ERT and that Cueball's assumption was about the emergency (e.g. "The building must be safe by now,") hence the comment about an ERT (although I now also see and agree with the explanation of the play on words). [[User:Z|Z]] ([[User talk:Z|talk]]) 23:32, 7 March 2014 (UTC)
::WOW: Neil Armstrong was just a movie star (I will not talk about 911) or what??? Look at the picture, look at the comic; I'm pretty sure Randall is giggle about all the comments here. I'm pretty sure you can find a ERT at the bible many times; but this isn't that Randall talks about!!!--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 00:36, 8 March 2014 (UTC)
:::Dgbrt, are you rejecting the simple ass-u-me explanation? — ''[[User:Tbc|tbc]] ([[User talk:Tbc|talk]]) 15:31, 8 March 2014 (UTC)''
::::And this explain is still bad because: 1) A hint to use Google as a help is not a proper way. 2) There is also a real language issue on that both different words "assume" and "assert". The joke is about mixing this language issues and all that memes.--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 23:00, 8 March 2014 (UTC)
:::::I know I didn't user Google to search anything, but I knew the "ass out of u and me" joke immediately, same thing with the assert one. That's the comic's joke. [[Special:Contributions/173.245.54.40|173.245.54.40]] 17:36, 12 March 2014 (UTC)

So... nobody else is going to mention that the proper phrase is, "When you assume, you make an ass IN FRONT OF 'u' and 'me'"? Not only is the "ass" in front of those two letters, but if somebody assumes, they're only making an ass out of theirself, not "you and me". Therefore, YOU are making an ass IN FRONT OF yourself and me. Though... are you truly doing so in front of yourself? Either way, more accurate than the innocent bystander being made an ass out of. [[User:Ferretwilliams|Ferretwilliams]] ([[User talk:Ferretwilliams|talk]]) 05:34, 13 March 2014 (UTC)

:I'm not a native English speaker but you seem to be correct and it should be fixed. Other than that, I first read the explanation as it is right now and it's perfect. [[Special:Contributions/108.162.219.125|108.162.219.125]] 04:21, 27 February 2015 (UTC)

I always like to respond with "... Or you make A SUM out of M and E" just to be different.[[Special:Contributions/173.245.54.8|173.245.54.8]]mtndew99