Is it possible to move without friction in space?

  • Thread starter karl22
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  • #1
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Hi
As you may know according to third law of Newton every action has a reaction.But my problem is that as we may know there is the need of friction for moving that you lean on something that you become able to move But as I have heard NASA has developed some gas-powered rocket maneuvering devices to allow astronauts to move freely in space without being tethered to the spacecraft(works according to third law of Newton)
But my question is without any friction and without any gas rocket and without anything that you stick to it,is it possible to move in space like by moving our bodies by ourselves ?
I mean is it possible to move without something that you stick to it or lean on it or without throwing anything from yourself ?
For example you just push your back with your hands then you move ?
Is it possible ???
Thank you very much for your answers
Have a nice day
 

Answers and Replies

  • #2
Doc Al
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Perhaps you can clarify your question. To start moving you need a force. But once you're moving, you'll keep moving. (Newton's first law.)

In space a gas rocket exerts a force on you by pushing out the exhaust gas, in keeping with Newton's third law.
 
  • #3
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Simply, no. You can't 'swim' in space.

You can move your arms, legs or anything you want, but your net movement will always be zero. You need the reaction force or you won't go anywhere.

When you move your arm backwards, your body will move forward. Your centre of mass will remain stationary.
 
  • #4
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Thanks a lot foe the answers.
If this is the case then when the gas rocket of the astronaut becomes broken or it doesn't work anymore and the astronaut is left alone in the space without being able to stick to anything how could he move and change his location??
Is it even possible ?
 
  • #5
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He could start throwing his tools / equipment. It would be slow, but may just do it.

Without expelling something from your person (whether propellant or otherwise) you won't go anywhere.
 
  • #6
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OK thank you so much for the answer
But my my question is that if you throw your hands to one side so fast then pull you hands to your side again but slowly this time won't you move ?
 
  • #7
Doc Al
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But my my question is that if you throw your hands to one side so fast then pull you hands to your side again but slowly this time won't you move ?
No. When you move your hands to one side, the rest of your body will move to the other side a bit to compensate. But your center of mass doesn't move (or rather it continues to move at the same velocity). It doesn't matter how fast or slow you move your hands.
 
  • #8
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No. When you move your hands to one side, the rest of your body will move to the other side a bit to compensate. But your center of mass doesn't move (or rather it continues to move at the same velocity). It doesn't matter how fast or slow you move your hands.
OK thank you so much for the answer
I got what I was looking for.
 
  • #9
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Yeah if you're in space and your gas rocket goes out, you're pretty much screwed. I don't think anyone has confirmed this, but they say that NASA gives astronauts cyanide capsules to bite down on just in case of such an event. Otherwise you can end up drifting sloooowly away until you die.

Perhaps I shouldn't mention this, but theoretically light has momentum, so you CAN accelerate simply by shining a flashlight.

It's important to understand though, that light has VERY little momentum. I'm not going to do the calculations, but I would wager that you would need thousands if not millions of years to get any noticeable velocity from a hand-held flashlight.
 
  • #10
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Yeah if you're in space and your gas rocket goes out, you're pretty much screwed. I don't think anyone has confirmed this, but they say that NASA gives astronauts cyanide capsules to bite down on just in case of such an event. Otherwise you can end up drifting sloooowly away until you die.
I'd prefer to just run out of oxygen, I hear it's not a terrible way to go - the old hypoxia - that would be slowly running out of oxygen so you don't notice it so badly. Just drift off in a "I don't care" kind of way.
Perhaps I shouldn't mention this, but theoretically light has momentum, so you CAN accelerate simply by shining a flashlight.

It's important to understand though, that light has VERY little momentum. I'm not going to do the calculations, but I would wager that you would need thousands if not millions of years to get any noticeable velocity from a hand-held flashlight.
If you've got enough oxygen to last the X months / years it takes to travel the relatively short distance to the ship - and that's assuming you're not moving away to begin with.
 
  • #11
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The only fine point I'd add is the solar wind....it's a negligible "frictional force" in the above considerations ...made up of sparse densities of electrons and protons....
 
  • #12
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The only fine point I'd add is the solar wind....it's a negligible "frictional force" in the above considerations ...made up of sparse densities of electrons and protons....
Well I think it's safe to say that if the situation posed by the OP occurs, there is absolutely nothing you can do to save yourself, especially so far as attempting to 'swim' in space goes.

If they don't come save you, you're in deep trouble.
 
  • #13
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I'd prefer to just run out of oxygen, I hear it's not a terrible way to go - the old hypoxia - that would be slowly running out of oxygen so you don't notice it so badly. Just drift off in a "I don't care" kind of way.
This is true, I didn't think about that. It's supposed to be one of the most pleasant ways to die...to the point where once you start going down the slippery slope, even if you had a chance to save yourself you wouldn't necessarily do it.
 
  • #14
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This is true, I didn't think about that. It's supposed to be one of the most pleasant ways to die...to the point where once you start going down the slippery slope, even if you had a chance to save yourself you wouldn't necessarily do it.
That's what I like about it. You become 'happy' and just don't care.
 
  • #15
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I'd prefer to just run out of oxygen, I hear it's not a terrible way to go - the old hypoxia - that would be slowly running out of oxygen so you don't notice it so badly. Just drift off in a "I don't care" kind of way.
I think it's only a nice way to go if you still can breathe something. But when spaceman Biff's tank approaches empty, he will struggle to breathe and won't be able to get a breath, very unpleasent, like your SCUBA tank going empty. As for the cyanide, how can Biff move it into his mouth?
 
  • #16
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I think it's only a nice way to go if you still can breathe something. But when spaceman Biff's tank approaches empty, he will struggle to breathe and won't be able to get a breath, very unpleasent, like your SCUBA tank going empty. As for the cyanide, how can Biff move it into his mouth?
In scuba, when you breathe out the exhaust is ejected so when the tanks are empty you can't draw anything in - horrible suffocation.

I figured the CO2 would build up in the helmet as the O2 started to get too low. The only way this wouldn't hold is if they have a dedicated pump removing CO2 from the helmet.
 
  • #17
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As for the cyanide, how can Biff move it into his mouth?
I guess the idea is to keep the capsule in your mouth so that you can bite down on it when needed. I don't know, sounds dangerous. It doesn't really matter, it's probably an old wives' tale anyway.
 

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