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Author Topic: Have any humans ever experienced zero gravity?  (Read 4365 times)

Offline Geezer

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Have any humans ever experienced zero gravity?
« on: 14/11/2009 17:37:46 »
Whadyafink?


 

Offline Karsten

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Have any humans ever experienced zero gravity?
« Reply #1 on: 14/11/2009 21:16:22 »
Whaddayamean? Freefall? Orbiting the planet? Or not exposed to gravity at all?
 

Offline Geezer

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Have any humans ever experienced zero gravity?
« Reply #2 on: 14/11/2009 22:19:52 »
 I would think zero gravity has to mean zero gravity! As in, there ain't none.
 

Offline RD

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Have any humans ever experienced zero gravity?
« Reply #3 on: 14/11/2009 23:16:37 »
Surely astronauts will always experience a gravitational pull, even if it is just towards the center of mass of their craft.
 

Offline Madidus_Scientia

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Have any humans ever experienced zero gravity?
« Reply #4 on: 14/11/2009 23:28:47 »
Well, has anything in the universe ever experienced zero gravity?
 

Offline LeeE

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Have any humans ever experienced zero gravity?
« Reply #5 on: 15/11/2009 01:26:24 »
Well, has anything in the universe ever experienced zero gravity?

Nope.

In the current models of gravity, it decreases with distance, according to the inverse square law, but never reaches zero, so there is nowhere in the universe where there is no gravity.

Gravity can be neutralised, so that the net force over a surface is zero, but it's not true to say that there is no gravity there as there will be a gravitational gradient either side of the surface; the steepness of the gradient will depend upon the size and distance of the opposing masses.

Any object with nonzero size in the plane of the surface of gravitational equipotential must straddle the surface and so will experience gravity.
 

Offline Geezer

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Have any humans ever experienced zero gravity?
« Reply #6 on: 15/11/2009 04:01:53 »
I started to think that the austronauts who went to the Moon might have been in zero gravity at the point where the gravitational attraction of the moon cancelled out the gravitational attraction of the Earth. The net effect would be zero, but, I'm not sure it's legitimate to describe that as zero gravity.
 

Offline Madidus_Scientia

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Have any humans ever experienced zero gravity?
« Reply #7 on: 15/11/2009 09:28:39 »
Well, if you drew a line between earth and the moon and called it the X axis, even if the net effect of gravity was 0 at a certain spot somewhere along it, there would still be attraction from Y and Z directions from other stars/rest of the universe.
 

Offline Bored chemist

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Have any humans ever experienced zero gravity?
« Reply #8 on: 15/11/2009 10:08:58 »
Any finite, massive object like an astronaut will allways be affected by gravity- his head will attract his feet.
 

Offline LeeE

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Have any humans ever experienced zero gravity?
« Reply #9 on: 15/11/2009 12:52:37 »
Well, if you drew a line between earth and the moon and called it the X axis, even if the net effect of gravity was 0 at a certain spot somewhere along it, there would still be attraction from Y and Z directions from other stars/rest of the universe.

This is so if you only think in terms of a straight axis between the Earth and the Moon but in practice there will be a surface of gravitational equipotential.  The surface won't be flat, of course, but curved due to the greater mass of the Earth, and it'll have bumps in it due to distortion by the rest of the universe.
 

Offline Karsten

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Have any humans ever experienced zero gravity?
« Reply #10 on: 15/11/2009 18:59:09 »
So, is canceling of forces allowed?
 

Offline Geezer

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Have any humans ever experienced zero gravity?
« Reply #11 on: 15/11/2009 20:49:45 »
I started to think that the austronauts who went to the Moon might have been in zero gravity at the point where the gravitational attraction of the moon cancelled out the gravitational attraction of the Earth. The net effect would be zero, but, I'm not sure it's legitimate to describe that as zero gravity.

In retrospect, it can't be zero gravity there either. The earth/moon/spacecraft ensemble is still zipping around the sun. If you brought the spacecraft to a complete halt (relative to our solar system say) at the neutral point between the moon and earth, it would start to accelerate towards the sun, not to mention that it would not be a the neutral point for very long.
 

Offline LeeE

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Have any humans ever experienced zero gravity?
« Reply #12 on: 16/11/2009 12:31:37 »
So, is canceling of forces allowed?

Not so much canceled as balanced; you can't remove the gravity without removing the mass, but you can use another mass to balance the gravity from the first mass.
 

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Have any humans ever experienced zero gravity?
« Reply #12 on: 16/11/2009 12:31:37 »

 

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