Space Contraction: Does Moving Frame Affect Observation?

[rahaverhma]

Does space contract when one observes the space from the frame which is moving with relativistic velocity?

 

[Ibix]

What do you mean by "space"? If you have two things separated by a gap of length L at rest then, when observed from a frame where they are moving at constant velocity v they will be separated by ##L\sqrt{1-v^2/c^2}## (edit: and not ##L/\sqrt {1-v^2/c^2}## as I originally wrote - typo, sorry), yes, if that's what you mean. I wouldn't call that "space contraction", though, because that would be rather confusing.

 

[vanhees71]

Usually it's called "length contraction", and it's the length of a moving object measured by an observer relative to whom the object moves. It's not what you see when you watch it. To see how things look when moving at relativistic speeds, see

http://www.spacetimetravel.org/inhalt.html

Roughly speaking, you don't see Lorentz contracted objects but rather rotated ones. The reason is that measuring a distance means that the observer brings into coincidence the two points, defining the distance, simultaneously with his/her ruler. Simultaneously means in the reference frame, where the observer is at rest. Looking at an object, rather, means to see the light that enters your eyes simultaneously, and depending on the shape and velocity of the object that's not the same as the length-measurement description. Have a look at the marvelous animations by Ruder.

 

[A.T.]

Does space contract when one observes the space from the frame which is moving with relativistic velocity?

If anything, space effectively expands for objects that move relative to you, because you can fit more of these objects into the same length, as measured by you. But we usually interpret this as the objects contracting, not as the space expanding.

 

[haushofer]

Does space contract when one observes the space from the frame which is moving with relativistic velocity?

No. A length is defined between to simulteneous events (!) and simultanity is relative, hence length contraction.

 

[phinds]

Does space contract ...

It is never a good idea to impart physical characteristics to space, which really is just geometry. Rather, it makes more sense to talk about the distance between objects and the length of objects, leaving space entirely out of the discussion.

 

[Orodruin]

It is never a good idea to impart physical characteristics to space, which really is just geometry. Rather, it makes more sense to talk about the distance between objects and the length of objects, leaving space entirely out of the discussion.

In particular as what ”space” is is observer dependent.