Sign swapping - spacelike intervals

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Discussion Overview

The discussion revolves around the properties of spacelike intervals in the context of special relativity, specifically focusing on the ability to swap the signs of the difference between two events, denoted as s = x - y. Participants explore the implications of this property and the existence of continuous transformations between the two events.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why the sign of s can be swapped for spacelike intervals (s^2 < 0).
  • Another participant suggests that there exists a continuous transformation between x - y and y - x for spacelike intervals, but not for timelike intervals.
  • A later reply proposes that the ability to choose a reference frame where two events occur simultaneously explains the sign swapping for spacelike intervals, contrasting with timelike intervals.
  • Another participant elaborates on the continuous transformation by describing a geometric rotation of 180° about an axis that is 45° between x and y, asserting that this transformation is valid and continuous.

Areas of Agreement / Disagreement

Participants express differing views on the nature of transformations between spacelike and timelike intervals, with some proposing the existence of continuous transformations while others focus on the implications of reference frames. The discussion remains unresolved regarding the specifics of these transformations.

Contextual Notes

Some assumptions about the nature of spacelike and timelike intervals and the definitions of continuous transformations are not fully explored, leaving room for further clarification.

Svendsen
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Hello guys!

I´ve seen that for spacelike intervals, ie [itex]s^2 < 0[/itex] you´re able to swap the sign of s = x-y = y-x. Why is that?

Thanks!
 
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Supposedly there exists a continuous transform between x-y and y-x for spacelike intervals, but not for timelike ones. Can anyone show me that?
 
Figured it out! The reason is that for spacelike intervals it is possible to choose a reference frame such that the two events x and y occur at the same time. This however is not possible for timelike ones.
 
Svendsen said:
Supposedly there exists a continuous transform between x-y and y-x for spacelike intervals, but not for timelike ones. Can anyone show me that?
Take the axis which is 45° between x and y. Rotate 180° about that axis. Now you have swapped x and y, and since every rotation about that axis less than 180° is also a valid transform, the transform is continuous.
 

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