Explain xkcd: It's 'cause you're dumb.
In the opening panel of this comic an unknown woman sees Cueball sitting on a swing set. She tells him that during his swing he becomes weightless. Cueball then imagines that at the peak of his swing he is able to become permanently weightless, floating above the ground without any support.
When on a swing or other pendulum ride, there is a moment between swinging forwards/backwards and swinging back down again when the forces of gravity, friction, air resistance, etc., bring the velocity of the swing to zero. At this moment, there is no acceleration toward the pivot of the swing (since the centripetal acceleration is proportional to the square of the speed). So the swinger experiences no centrifugal force. Of course gravity still acts on the person, but if the swing is horizontal at that point, then the there is no reaction force, so for one moment the swinger is in free-fall and experiences weightlessness.
In the title text Cueball asks for a pocket fan, believing he could fly around the garden using this small device perhaps as a propeller.
- [Woman talking to Cueball on swing-set.]
- Woman: You know, at the peak of a big swing, you become weightless.
- [Thought bubble from Cueball.]
- [Cueball swings higher and higher. At the peak of a big swing he shoves off the swing. Cueball remains hovering in the air.]
- Cueball: Hey guys. Come check this out.
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A glass with water can be momentarily inverted at this moment and the water will not leave the glass!--DrMath 08:56, 16 November 2013 (UTC)
Isn't the point about illustrating that you do in fact have weight even in instences that are written off as weightless? In space you just happen to be falling at the same velocity of your surroundings, maintaining orbit simply by moving fast enough to miss the Earth. On top of which, in a low enough orbit g is still close to 9.8 m/s^2 if only because altitude is insignificant compared to the radius of the Earth.--Passing Stranger 14:10 August 2014 (UTC)
No, you don't have weight in some instances. Weight is dependent upon gravity, so in deep space with no planets or stars close enough to matter you would be weightless. Mass, on the other hand... 184.108.40.206 01:46, 10 January 2015 (UTC)
The woman appears to be his mother. -- 220.127.116.11 (talk) (please sign your comments with ~~~~)
Weight is actually a description of reaction force; if you're in free fall, and therefore not being pushed on by the floor or pulled on by a rope, you are weightless. If you are being swung on a rope, the direction of your "weight" is constantly changing. This might seem arbitrary, but it avoids things like everyone on a rotating space station being considered "weightless" due to the lack of gravity; a closed physical system can't tell the difference between gravity and uniform acceleration. 18.104.22.168 08:51, 13 May 2015 (UTC)
When I'm alone in elevators, I'll sometimes jump right before the elevator stars to descend. Because I have to fall a longer distance than I jumped, it tricks my brain into feeling a moment of weightlessness more than what I feel at my apogee. I also sometimes like to float underwater for long periods of time, pretending I'm on the ISS. Unfortunately I'm fucking terrified of deep water, and due to my lack of water-based activity, I've quite declined in my ability to hold my breath underwater. I used to be able to do it for at least a minute to a minute and a half when I was 12. I used to either pretend I was Neo, or pretend I was on the ISS or generically in space. Never both, though. Now I can hardly do 20 seconds. Now that I really want to start swimming again, I can't. I grew up with a pool I hardly used, and now I'm in college, and all of our pools are lap-based. i.e. I can't hog 25sqft of space to just be all floaty in. I'd have to take up an entire lane, which I don't want to do. So the only way I'd really be able to experience this is if I scuba dived. Maybe I should do that again. It's the closest, for now, I'll ever get to feeling like I'm in space. Maybe later I can afford a Zero G flight. Maybe later I can do some space tourism stuff. Maybe later I'll be an actual astronaut. Only I'm two inches too short, for now, apparently -3- International Space Station (talk) 09:21, 27 October 2015 (UTC)