Explain xkcd: It's 'cause you're dumb.
In this comic, the joke is that the "How to Juggle" book assumes that there is gravity and momentum in the place where you are juggling. It seems like there is no gravity or momentum because when Cueball throws the juggling balls up in the air, they don't come down, and also don't continue the trajectory that they had when they left his hands. Additionally, the image text tells us that someone else comes along and sees that the juggling book is still hovering over the trash can and never went into it.
While there are places in our universe with zero gravity (or at least microgravity), there is no place in our universe where objects with mass have no momentum. Some possible explanations might be that Cueball is outside of our universe, that Cueball has just discovered something that's theoretically impossible, or that Randall has taken comedic license on the "momentum" part for the sake of the joke.
- [The panel shows a close up of Cueball reading a book. The book is called "How To Juggle" and has a picture of a person juggling on the cover.]
- [The view now shows the entirety of Cueball. A book is splayed on the floor behind them, and he is holding some juggling balls.]
- [Cueball throws the juggling balls in the air.]
- [He lowers his arms to prepare to catch the balls. The balls are still hovering in mid-air.]
- [Cueball now stands with his arms by his sides. The balls have not moved and are still suspended in mid-air.]
- [Cueball jumps, trying to grab the lowest ball. He can't reach.]
- [Cueball scratches his head and stares at the still floating juggling balls.]
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- [Cueball throws the book into a trash can.]
But if there was no gravity, the balls would have maintained the trajectory and (neglecting air resistance) velocity that they had when they left cueball's hands! -- mwburden 220.127.116.11 23:17, 7 December 2012 (UTC)
- Very true! Please do consider reworking/replacing this explanation so it isn't so misleading! lcarsos_a (talk) 23:22, 7 December 2012 (UTC)
Added "or momentum" to the explanation. -- mwburden 18.104.22.168 13:03, 10 December 2012 (UTC)
It doesn't look like Cueball's jumping to me--just reaching for the balls. 22.214.171.124 08:45, 23 December 2012 (UTC)
- Nah I agree with the transcript. Both feet are noticeably higher than in the previous "standing" panels. And I can't picture anyone raising one leg weirdly like that if the other leg is planted on the ground - if he were looking to reach without jumping, he'd would be on tiptoes instead. - jerodast (talk) 13:18, 23 December 2012 (UTC)
I thought the joke was the book taught you how to levitate things, which Cueball finds useless since he wants to learn how to juggle. 126.96.36.199 08:17, 25 December 2012 (UTC)
I've interpreted this as a joke on how juggling works (as in, what it always looks like) in 2D images. The title text makes a similar joke, in that throwing or dropping something in a 2D image will always make it look like the thing is floating. (Unless they add motion lines and such and such, but even then, "Why are there black lines in the air?") - Jeff
I don't think this explanation is right. I interpreted this joke like this: Cueball is so bad at juggling that the balls don't even fall after being thrown. Perhaps this joke is similar to the ones in the boomerang comics. 188.8.131.52 22:18, 26 January 2014 (UTC)
I was thinking something like that, but instead maybe he just couldn't understand the next step? 184.108.40.206
14:25, 16 April 2014 (UTC)