Spacetime distortion - question

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Discussion Overview

The discussion revolves around the concept of spacetime distortion in relation to two objects of the same mass, one moving and the other at rest. Participants explore the implications of relativity on the ability to discern motion based on spacetime distortion, touching on theoretical aspects of General and Special Relativity.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • One participant questions whether it is possible to determine which object is moving based solely on spacetime distortion at a specific moment.
  • Another participant argues that motion is relative, suggesting that each object perceives the other as moving, leading to reciprocal distortions that cannot be fixed.
  • A participant expresses frustration with relativity, referencing Einstein's assertion that moving objects distort spacetime more, which affects the flow of time around them.
  • It is noted that in General Relativity, both momentum and energy can warp geometry, emphasizing the frame-dependent nature of motion.
  • One participant points out an error in the assumption that both objects can be considered still at a moment in time, referencing Zeno's paradoxes to illustrate the concept of relative motion.
  • Another participant seeks clarification on whether velocity can be inferred from spacetime distortion, suggesting that it might be possible to derive velocity from such information.
  • A later reply confirms that this was indeed the original intent of the question regarding the relationship between spacetime distortion and velocity.

Areas of Agreement / Disagreement

Participants express differing views on the nature of motion and spacetime distortion, with no consensus reached on whether velocity can be determined from spacetime distortion alone.

Contextual Notes

The discussion highlights the complexities of relativity, including the dependence on reference frames and the implications of acceleration, which remain unresolved.

Tail
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Let's say there are two objects of the same mass. One of the is moving, the other not. Now let's look at both of them at a certain moment of time. In this MOMENT both are still, they occupy a certain space. Can you tell which one is moving based on spacetime distortion (theoretically)?
 
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"One of them is moving and the other not". Relative to what? Each of them will see the other as moving and apply reciprocal "distortions" to explain the data they receive. There is no "fixed space distortion" for you to examine.
 
Damn. I've always hated relativity.

But didn't Einstein state that things in motion distort spacetime more = time flows slower around them?
 
In General Relativity, momentum is one of the things, along with energy, that can warp geometry. The point, though, is that even more than Special Relativity, GR is slave to the frame. Einstein called it General Covariance; all your physics has to be true no matter what frame of view you adopt (up to smooth changes of coordinate). So it is still true that in one frame A is moving and in another it is B that is moving. This is all based on unaccelerated motion. acceleration is a whole nother question in GR, see the equivalence principle.
 
Originally posted by Tail
In this MOMENT both are still,

NO, that's the error in one of Zeno's paradoxes (so it goes back a lot longer than than relativity!). At a given instant an object moving relative to another still has a velocity.
 
I think what tail was asking was that given simply, a freeze frame "shot" of the two objects and of the space/time distortion around them, can you tell how fast they are going, relative to one another of course.

Can you obtain velocity from the information about space/time distortion. Maybe you can. Isn't the inverse possible.
 
Yes, that was exactly what I meant!
 

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