Could Tachyons Discredit Relativity?

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Discussion Overview

The discussion centers around the hypothetical existence of tachyons, particles that some propose could travel faster than light, and the implications this would have for the theory of relativity and causality. Participants explore various theoretical frameworks and interpretations related to tachyons and their compatibility with established physics.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants assert that tachyons are not massless and argue that their existence would not violate relativity but would violate causality.
  • One participant proposes the self-consistency principle as a potential way to accommodate tachyons without violating causality.
  • Another participant suggests that a preferred frame could be posited in which tachyons do not travel backwards in time, referencing Lorentz Ether Theory as a means to avoid causal paradoxes.
  • There is a discussion about the interpretation of the second postulate of relativity, with some participants questioning whether it implies that the speed of light is finite or infinite.
  • Concerns are raised about the reliability of Wikipedia as a source, with participants debating its accuracy in the context of the postulates of special relativity.

Areas of Agreement / Disagreement

Participants express differing views on the implications of tachyons for relativity and causality, with no consensus reached on the interpretations or the reliability of sources cited.

Contextual Notes

There are unresolved questions regarding the definitions of massless particles and the implications of tachyons on causality and relativity, as well as the interpretation of the second postulate of relativity.

BadgerBadger92
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I hear these massless and hypothetical particles could travel faster than light, would that prove relativity wrong?
 
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Tachyons are not massless.

No, they would not violate relativity per se. They would violate causality.
 
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Orodruin said:
No, they would not violate relativity per se. They would violate causality.
Sorry for that mistake.

What if the self consistency principle was real and not violate causality?
 
The easiest way to accommodate tachyons in relativity without breaking causality is to posit a preferred frame in which tachyons never travel backwards in time. The choice of frame is consequence-free for non-tachyonic physics, so is just the Lorentz Ether Theory interpretation of relativity, but rules out causal paradoxes such as the tachyonic anti-telephone.

The other obvious way to do it is to note that we require theories to obey causality because our observation is that causality is never violated. If we were to observe tachyons allowing causality violations, we'd have to change that requirement.
 
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Interestingly the second postulate doesn't say if c is finite or infinite, at least according to wiki:
As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body. Or: the speed of light in free space has the same value c in all inertial frames of reference.
https://en.wikipedia.org/wiki/Postulates_of_special_relativity
 
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MathematicalPhysicist said:
Interestingly the second postulate doesn't say if c is finite or infinite, at least according to wiki:

https://en.wikipedia.org/wiki/Postulates_of_special_relativity
I think it is understood that when it says definite value it means finite. Otherwise it is imprecise and needs an edit to make it clearer.
 
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MathematicalPhysicist said:
at least according to wiki
Which just illustrates that Wikipedia is not a reliable source.
 

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