I Could Tachyons Discredit Relativity?

[BadgerBadger92]

I hear these massless and hypothetical particles could travel faster than light, would that prove relativity wrong?

 

[Orodruin]

Tachyons are not massless.

No, they would not violate relativity per se. They would violate causality.

 

[BadgerBadger92]

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?

 

[Ibix]

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.

 

[MathematicalPhysicist]

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

 

[martinbn]

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.

 

[PeterDonis]

at least according to wiki

Which just illustrates that Wikipedia is not a reliable source.

 

[PeroK]

Which just illustrates that Wikipedia is not a reliable source.

Give that Wikipedia makes clear that $0 < c < \infty$, this illustrates rather that @MathematicalPhysicist is an unreliable source.

https://en.wikipedia.org/wiki/Postu...ty#Mathematical_formulation_of_the_postulates