AntiGravity and its effects in space

[noxid]

If i was in a tube of circular cross section that curved on itself (doughnut shaped), and i was in space floating in the center if the tube and the tube was spinning very fast, negating all the effects of real gravity and air inside the tube, would i be attracted to any particular side of the tube???
Follow up question, is it correct to say that i have to be touching the sides of the spinning tube in order to feel the effects of artificial gravity

[pzkpfw]

(See also: http://www.thescienceforum.com/physics/47068-artificial-gravity-its-effects-space.html#post603693 )

 

Gravity is "felt" as acceleration. Standing on Earth you're feeling an acceleration of 9.8 m/s/s

 

For a spinning tube to make you feel "artificial gravity" (you seem to be talking about something like a space-station spinning to give the occupants the feeling of gravity) you'd need that tube to be accelerating you.

 

That means, continually changing your velocity. You're only going to get that if you are being spun by the tube, so your scenario ("floating in the centre") means you'd not feel it. You'd need to be doing something like standing on the inside of the outer wall of the tube. (i.e. follow up question, = yes).

 

See the movie: https://en.wikipedia.org/wiki/2001:_A_Space_Odyssey_(film)

 

(

I don't think your scenario would work. The air would be moving with the tube, which would move you, and make you drift to the outer edge, where you'd touch the tube and start to be accelerated by it, eventually feeling that "artificial gravity".

)

Edited August 3, 2016 by pzkpfw

[noxid]

(See also: http://www.thescienceforum.com/physics/47068-artificial-gravity-its-effects-space.html#post603693 )

 

Gravity is "felt" as acceleration. Standing on Earth you're feeling an acceleration of 9.8 m/s/s

 

For a spinning tube to make you feel "artificial gravity" (you seem to be talking about something like a space-station spinning to give the occupants the feeling of gravity) you'd need that tube to be accelerating you.

 

That means, continually changing your velocity. You're only going to get that if you are being spun by the tube, so your scenario ("floating in the centre") means you'd not feel it. You'd need to be doing something like standing on the inside of the outer wall of the tube. (i.e. follow up question, = yes).

 

See the movie: https://en.wikipedia.org/wiki/2001:_A_Space_Odyssey_(film)

 

(

I don't think your scenario would work. The air would be moving with the tube, which would move you, and make you drift to the outer edge, where you'd touch the tube and start to be accelerated by it, eventually feeling that "artificial gravity".

)

wouldnt the air tend to collect at the outer edge, therefore shouldnt i drift towards the center

[pzkpfw]

wouldnt the air tend to collect at the outer edge, therefore shouldnt i drift towards the center

I don't see why.

 

You are more dense than air.

[MigL]

Was there a bad pun in there ?

[Phi for All]

You are more dense than air.

 

He was just asking a question, no need to be insulting.

 

 

 

 

 

 

 

 

 

 

 

[MigL]

Sorry, I made a bad joke.

[noxid]

I don't see why.

 

You are more dense than air.

yeah but you are not touching the sides of the tube

besides, if the air immediate to the outer edge of tube gets accelerated, i think it would tend to 'stick' to the inner wall of the outer edge, creating a partial vacuum that pull even more air towards this edge. Overtime, it would create a higher pressure of fluid at the outer edge which would tend to push any object towards to inner edge

[swansont]

yeah but you are not touching the sides of the tube

besides, if the air immediate to the outer edge of tube gets accelerated, i think it would tend to 'stick' to the inner wall of the outer edge, creating a partial vacuum that pull even more air towards this edge. Overtime, it would create a higher pressure of fluid at the outer edge which would tend to push any object towards to inner edge

 

 

Vacuums don't pull. Air pressure pushes.

 

Whatever pressure gradient you set up is going to depend on the speed of rotation and the resulting centripetal force. Whether anything gets pushed to the center depends on the density of it. More dense objects will migrate out, because they can displace less dense objects. It's how a centrifuge works.

[pzkpfw]

yeah but ...

I was thinking this may help:

 

There's a standard/common thought experiment, where a person is in a closed elevator. They can't tell if their elevator is at "rest" in a lift shaft on Earth, or out in space (away from noticeable gravity) being accelerated at 9.8 m/s/s by rockets.

 

If a person was in either elevator, would they tend to fall to the floor of the elevator, or rise to its ceiling?

Edited August 3, 2016 by pzkpfw

[noxid]

I was thinking this may help:

 

There's a standard/common thought experiment, where a person is in a closed elevator. They can't tell if their elevator is at "rest" in a lift shaft on Earth, or out in space (away from noticeable gravity) being accelerated at 9.8 m/s/s by rockets.

 

If a person was in either elevator, would they tend to fall to the floor of the elevator, or rise to its ceiling?

they would both obviously tend to fall to the, floor, but i think what i am talking about is different

imaging there is an astronaut in space at constant velocity, now suddenly place the tube structure around him with the center of the tube(center of rotation) moving at a velocity equal to that of the astronaut,i think if there is no air, it is safe to say the astronaut will not be influenced by the doughnut structure (assume it has no mass).

Now if when it appeared around the astronaut it was filled with air, the air would tend toward the outer edge of the tube...........

Now that i think about it air currents may be set up in the direction of motion of the rotation, that will push the astronaut towards the outer wall,.....lets assume the inner walls are smooth...what i want to explore is the centrifugal effects on the air,not the push of the inner walls on the air, the air having less mass and lower density would be much more readily accelerated than the astronaut and so collects a lot quicker on the outer walls creating a pressure differential with a higher pressure at the outer walls, which may or may not be enough to push the astronaut opposite

[Strange]

You don't provide any figures for size, speed, etc so it is hard to be specific. (You really should do the maths to work out what happens.)

 

But compare it to the air on Earth. It is pulled towards the Earth by gravity. But it is still a blanket several miles thick. So your entire tube would be full of air that is ever so slightly denser towards the outside. Therefore your astronaut would be carried around by the air and be thrown towards the outer wall.

 

 

 

 

a higher pressure at the outer walls, which may or may not be enough to push the astronaut opposite

 

Does the higher air pressure at the surface of the Earth push you into the sky?

[noxid]

 

 

Does the higher air pressure at the surface of the Earth push you into the sky?

Good point, however what i was mostly trying to get at was whether or not their will be a pressure gradient that would be set up from the outer to the inner walls, regardless do you think the astronaut will basically stay in the same position

now that i think about it, wasnt this how ringworld keep its atmosphere

[Strange]

Good point, however what i was mostly trying to get at was whether or not their will be a pressure gradient that would be set up from the outer to the inner walls,

 

There might be. It depends on the size and speed of your centrifuge. It will be tiny, for any realistic scenario.

 

regardless do you think the astronaut will basically stay in the same position

 

No. Obviously not. For the reasons you have been given.

 

You seem to want to create some unrealistic / impossible scenario. For what purpose?

 

now that i think about it, wasnt this how ringworld keep its atmosphere

From what I remember, that is the case. The rotation of the ringworld also kept the people on the ground.

[noxid]

It may be unrealistic in terms of scale/size but the concept is hard science, this is what a thought experiment is

[Strange]

It may be unrealistic in terms of scale/size but the concept is hard science, this is what a thought experiment is

 

 

And in a thought experiment you work out what would actually happen, not decide on the impossible conclusion you want and then try and make up arguments to support that.

 

What is the point of this thread now?

[J.C.MacSwell]

I was thinking this may help:

 

There's a standard/common thought experiment, where a person is in a closed elevator. They can't tell if their elevator is at "rest" in a lift shaft on Earth, or out in space (away from noticeable gravity) being accelerated at 9.8 m/s/s by rockets.

 

If a person was in either elevator, would they tend to fall to the floor of the elevator, or rise to its ceiling?

To the ceiling of course...assuming the elevator was filled with water and a good lifejacket was being worn...