What is the theory of relativity?

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Discussion Overview

The discussion revolves around the theory of relativity, specifically addressing the concepts of absolute motion versus relative motion. Participants explore the implications of these ideas within the framework of special relativity (SR) and Lorentz Ether Theory (LET), as well as their relevance to classical mechanics.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants question whether the theory of relativity posits that there is no absolute movement, only relative movement between frames, or if there is absolute movement that cannot be measured.
  • Others differentiate between the interpretations of relativity, noting that the former aligns with standard special relativity while the latter corresponds to Lorentz Ether Theory, which is generally considered deprecated.
  • A participant points out that the concept of relative motion is not exclusive to relativity and is also applicable in classical mechanics.
  • There is a discussion about a hypothetical scenario involving three spaceships moving in different directions, with some arguing that one must be moving in an absolute sense, while others contend that this assumption lacks experimental consequences.
  • One participant emphasizes that according to standard special relativity, the notion of "absolute motion" does not hold meaning.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of absolute versus relative motion, with no consensus reached on the validity or implications of these interpretations within the context of relativity.

Contextual Notes

Some claims depend on interpretations of motion and the definitions of absolute and relative movement, which remain unresolved in the discussion.

Ross Arden
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Is the Theorey of relativity that there is no absolute movement, only movement of one frame relative to another or that there is absolute movement but we cannot measure it ?
 
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What would be the difference?

As I understand it, the former is vanilla SR; the latter is Lorentz Ether Theory. The latter is generally deprecated because it has an extra assumption, but it makes no difference to the maths.
 
This is part of relativity, yes. But it is not exclusive to special and general relativity as it is also the case in classical mechanics.
 
Ross Arden said:
Is the Theorey of relativity that there is no absolute movement, only movement of one frame relative to another or that there is absolute movement but we cannot measure it ?

Experimentally, the two are indistinguishable, and there is an interpretation of special relativity that takes the second option; however, that interpretation (usually referred to as "Lorentz Ether Theory") is not used in modern SR and is not a suitable topic for discussion here:

https://www.physicsforums.com/insights/pfs-policy-on-lorentz-ether-theory-and-block-universe/
 
so if you have three space ships one pointing along the x axis, one on the y-axis and one on the z axis and then they all blast off, surely the assumption can credibly be made that one of them must be moving in an absolute sense, not in a relative sense?
 
Depends on whether or not "absolute motion" means anything. Vanilla SR says it doesn't.
 
Ross Arden said:
surely the assumption can credibly be made that one of them must be moving in an absolute sense

You can make this assumption, but since it has no experimental consequences at all, there's no point.
 
Closing this thread as discussions of LET are out of bounds, per the link already provided.
 

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