# can someone help explain

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#### jasonpply

##### Guest
Me and the wife were watching a movie the other day. ( Mission To Mars ) at one point one of the astronauts started to fall away from his crew to the planet. after the big dramatic rescue attempt failed he commited suicide. she asked me why he couldnt just start flailing his arms in a swimming motion to get back to his crew.? i was unable to giveher a good answer can someone help me out with that?
thanks Jason

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#### nimbus

##### Guest
Conservation of momentum.. E.g. when a cat twirls around to land on its legs, the center of gravity will always remain the same, as far as its flailing around affects.
And stronger gravity than the little amount of air for the astronaut could overcome by flapping his arms and legs like a bird.

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#### MeteorWayne

##### Guest
IIRC, he was well above the atmosphere at that point, so all the flailing in thw world (or mars) wouldn't help. His mass was being pulled in by the gravity of Mars, and he was going to burn up when he hit the atmopshere like any other meteor.

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#### nimbus

##### Guest
... because being in orbit, as they were in that scene, means that you're at the velocity where you're going fast enough (tangentially) to neither be drawn into the planet (or atmosphere and then slow down due to drag, etc; and orbital speed = 0 means you fall like a rock, like Kittinger did) nor escape its gravity. That speed's fairly fast.

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#### origin

##### Guest
When you swim you push against the water and that is what moves you forward. I assume that in a weightless environment if there was air (such as the space station) you could move yourself forward by 'swiming'. Because of the extremely low viscosity of air relative to water the 'air swiming' would hardly move you at all but I bet there would be some detectable movement. Unfortunately the hapless astronaut was in the vacuum of space and there was nothing he could do, there was no medium to push against.

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#### Saiph

##### Guest
Yep, they've got it right. At best he'd be able to turn himself about. But without rockets, or something to throw one way so he could move the other, he isn't going to change his overall path away from the crew. He's no more able to swim or fly in that setting than you can sitting on your couch watching the movie.

In order to get any sort of 'swimming' effect you describe, he'd have to have something like an earthlike atmosphere, but with gravity akin to the moon. Then, if he strapped on some wings to flap around he might have a chance...

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