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Author Topic: Is there an up and down in space?  (Read 7538 times)

Sandra Mafnas

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Is there an up and down in space?
« on: 29/04/2011 13:30:03 »
Sandra Mafnas  asked the Naked Scientists:
   
Hi Chris,

I love your show!! 

My question is:
How do astronauts know what is up or down?  We go by the sky is up, earth is down, east, west, north and south.

Thank you,
Sandra Mafnas
Surprise Arizona


What do you think?
« Last Edit: 29/04/2011 13:30:03 by _system »


 

Offline Supercryptid

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Is there an up and down in space?
« Reply #1 on: 29/04/2011 20:17:02 »
Up and down are completely relative; there is no up or down in space.
 

Offline Bill S

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Is there an up and down in space?
« Reply #2 on: 29/04/2011 22:16:12 »
If up and down are completely relative, could one not claim that, in space, up is away from the observer, and down towards the observer?
 

Offline Phractality

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Is there an up and down in space?
« Reply #3 on: 30/04/2011 02:12:00 »
Up is the direction of the gradient of gravitational potential.
 

Offline CliffordK

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Is there an up and down in space?
« Reply #4 on: 30/04/2011 06:07:50 »
When in orbit, you are actually in freefall, not truly zero-G.  So, down technically would still be towards the planet.

However, you might also define up and down with respect to your spacecraft.  So, what you would have called the ceiling on Earth would still be called the ceiling in orbit.
 

Offline imatfaal

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Is there an up and down in space?
« Reply #5 on: 30/04/2011 08:54:26 »
It's fairly arbitrary - Phract is right about gravity.  I think that if we are talking up/down from a human perspective then down is gonna be towards the sun.  Any human habitation within the solar system will have to be able to protect against the solar wind and blinding light with massive and thick protection in one direction- and psychologically that will be the floor.  You have windows/skylights in the walls and the ceiling but the floor is the solid reassuring lump beneath you 
 

Offline Phractality

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Is there an up and down in space?
« Reply #6 on: 30/04/2011 19:20:49 »
It's fairly arbitrary - Phract is right about gravity.  I think that if we are talking up/down from a human perspective then down is gonna be towards the sun.  Any human habitation within the solar system will have to be able to protect against the solar wind and blinding light with massive and thick protection in one direction- and psychologically that will be the floor.  You have windows/skylights in the walls and the ceiling but the floor is the solid reassuring lump beneath you 

Gravitational potential is relative to the reference frame. Relative to the local comoving frame, there is an absolute max potential in the vicinity of the center of the nearest void of the cosmic foam. In the reference frame of the Earth-moon system, there is a relative maximum at each of the L-points. In a rotating space satation with centrifugal gravity, the axis of rotation is a relative maximum. So "up" is relative.
 

Offline Bored chemist

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Is there an up and down in space?
« Reply #7 on: 01/05/2011 12:50:07 »
There is no agreed "up and down" on Earth. My friend in New Zealand and I have more or less totally opposed views on which way is "up".
 

Offline Bill S

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Is there an up and down in space?
« Reply #8 on: 02/05/2011 23:01:30 »
Quote from: Bored chemist
My friend in New Zealand and I have more or less totally opposed views on which way is "up".

Do you and your friend not agree that up is way from the centre of the Earth?
 

The Naked Scientists Forum

Is there an up and down in space?
« Reply #8 on: 02/05/2011 23:01:30 »

 

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