Moving Faster Than Light: Are There Symmetrical Rules?

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Discussion Overview

The discussion revolves around the concept of relative motion in the context of objects moving away from each other at speeds potentially exceeding the speed of light. Participants explore the implications of symmetry in such scenarios, questioning whether established theories of motion apply similarly to superluminal speeds and how this relates to observable phenomena in cosmology.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions if the symmetry of motion applies to objects moving away at superluminal speeds, suggesting that if an object is receding from them, they are also receding from it at the same rate.
  • Another participant argues that nothing is "moving" in the traditional sense, stating that the distance between comoving observers can increase faster than light without implying actual relative motion.
  • A later reply emphasizes that the concept of superluminal velocity is a coordinate artifact with no physical significance, comparing it to an apparent superluminal motion observed in a local context.
  • One participant mentions that physical insights should derive from measurable invariants, such as redshift, rather than from superluminal velocities.
  • Another participant introduces a comparative scenario involving a race between an object with mass and a beam of light, asserting that the light will always prevail.

Areas of Agreement / Disagreement

Participants express differing views on the nature of motion and the applicability of symmetry in the context of superluminal speeds. There is no consensus on whether traditional theories of motion hold for objects moving faster than light.

Contextual Notes

Participants highlight the importance of precise terminology and the potential confusion arising from the use of superluminal velocities, indicating that further clarification may be necessary to address the underlying concepts accurately.

roineust
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Would it be correct to say, that we are moving away from stars at the edge of the universe, at the same rate that these stars are moving away from us? I am relating to stars that are moving in relation to us, at a speed that is faster than the speed of light.

Is the symmetry that maintains that if an object in space is moving away from me at a certain rate, then to all regards i am moving away from the object at the same rate, also true for objects moving away from me at a speed higher than the speed of light? Is symmetry the correct term in this context?

This question is asked for both momentary speed, for acceleration and for unnatural (hypothetically human made) constant speed.

Does modern physics assume that all theories that relate to objects moving away (or towards) us at a speed lower than the speed of light, are also correct for objects moving away from us, at speeds higher than the speed of light and that the matter of being unable to observe these objects, is just a question of non-significance in this context of theories ratification?
 
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Nothing is "moving" relative to anything else here. The distance* between comoving observers may grow faster than the speed of light, but this has nothing to do with actual relative motion. Relative motion can only be defined locally (i.e., in a region of spacetime small enough for spacetime curvature to be negligible).

* For the particular definition of "distance" typically used in cosmology.
 
Orodruin said:
Nothing is "moving" relative to anything else here. The distance* between comoving observers may grow faster than the speed of light, but this has nothing to do with actual relative motion. Relative motion can only be defined locally (i.e., in a region of spacetime small enough for spacetime curvature to be negligible).

* For the particular definition of "distance" typically used in cosmology.

I will try to rephrase my questions later, according to the terminology that you use here, it might take me some time.
 
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roineust said:
I will try to rephrase my questions later, according to the terminology that you use here, it might take me some time.
It's not just a matter of terminology. The superluminal velocity that you're considering here is completely a coordinate artifact. It has no more physical significance, and no more can be used sensibly as a velocity, than the apparent superluminal velocity of Alpha Centauri when I sit on my porch and watch it move halfway around around a circle of radius four light-years in just one night.

Any physical insight into the situation will come from studying the directly measurable invariants, such as the redshift of light signals exchanged between us and the distant stars.
 
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Another way to look at is that in a race between some object (with mass) and a beam of light, the beam of light will always win.
 

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