A classification system for particles based on how fast they can go lists:

  1. Bradyons - Particles that go less than the speed of light
  2. Luxons - Particles that go at the speed of light
  3. Tachyons - Particles that go faster than the speed of light

It occurred to me we have a category missing, what about a particle that cannot go at any speed whatsoever, a minimum speed particle (the opposite classification to a Luxon). I understand that Tachyons and what-ever-this-is-ons are not "real" particles, but rather math constructs. Rather, using the same steps that one would use with Tachyons, what would a particle that wen't the minimum speed for any observer act like? As a Luxon would always travel at the speed of light in any reference frame, would this always travel at 0c in any reference frame? Theoretically of course.


1 Answer 1


No. The categories you've listed are the only ones consistent with special relativity. If an object has $v=0$ in one reference frame, it will not have $v=0$ in any other frame. If something appears to be still to you and you start walking, it will no longer be still.

The speed $c$ is special, as the only invariant speed allowed in special relativity. You can't have two invariant speeds without giving up on the whole structure of the theory.

  • $\begingroup$ Got it. I can see how that would cause problems. $\endgroup$
    – Terran
    Jan 31, 2018 at 2:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.