The joke here 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.
Or, it could be that in the third panel, it looks like he's juggling, but the next ones show that they're just floating.
The title text draws on the fact the book being thrown into the trash can can also be interpreted as a hovering book, while in a still image form, such as shown in this comic.
While it is possible to reach 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, he has just discovered something that's theoretically impossible, or he is just dreaming, or Randall has taken comedic license on the "momentum" part for the sake of the joke. Or he could be in a place where the surrounding fluid, instead of having the normal properties of earth's atmosphere, is a very thick or viscous fluid in which things simply become stuck.
Also, because Cueball jumps and returns to the ground (panels 6 & 7), it would appear that the effect is limited to the balls and the book, and does not extend to Cueball himself. However, his return could be caused by magnetism, rather than gravity. (In science fiction, boots containing magnets are used to hold astronauts "down" when gravity is not adequate.)
- [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.]
- [Cueball throws the book into a trash can.]
- This comic actually appeared previously in 940: Oversight, due to a bug in the xkcd Android app where instead of the correct comic, an unpublished 'Five Minute Comics' was shown.
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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 184.108.40.206 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 220.127.116.11 13:03, 10 December 2012 (UTC)
But without momentum he wouldn't have been able to 'throw the balls up'. He must instead have placed them there, which he didn't because he can't reach. The only way to save physics I see is that there is something producing very high friction, slowing the balls down until they are trapped. But that's probably not what is happening in the comic. 18.104.22.168 04:30, 9 August 2017 (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 am more than fairly certain that this is the intended interpretation. The transition from the 3rd to 4th panel and the last panel to the mouseover text are plot twists made possible by the fact that a comic can only show snapshots of something we assume to be continuous. 188.8.131.52 Suhail
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. 184.108.40.206 22:18, 26 January 2014 (UTC)
I was thinking something like that, but instead maybe he just couldn't understand the next step? 220.127.116.11 14:25, 16 April 2014 (UTC)
The trick is to use apples. I'm not sure it is a next step though. Perhaps a step back?
I used Google News BEFORE it was clickbait (talk) 12:37, 23 January 2015 (UTC)
This same comic was in the five-minute comics in xkcd 940. Has anyone else noticed this? -Brittany
This comic is very disjointed and awkward. It's not incomplete it just... it needs work Lackadaisical (talk) 21:05, 16 April 2016 (UTC)
- This comment doesn't seem to mean anything. 18.104.22.168 08:07, 30 August 2019 (UTC)
- Check timestamps my friend, although I just realized I made a mistake by saying "comic" when I meant "comic explanation," once upon a time this explanation read very poorly, those issues have since been taken care of by editing. Lackadaisical (talk)