Relativity Question

Discussion in 'Science and Technology' started by ThankQ, Feb 1, 2019.

Joined:
Mar 27, 2003
Location:
Omnipresent
I could preface this question with three pages of posts, but I'll just put it out there and see what shakes lose.

Put two flashlights (torches, lasers, whatever) butt to butt. Then send out two light beams in opposite directions. How fast, realitive to each other, are those light beams traveling? If you picked one photon from Beam West and one photon Beam East and determined their relative velocity, what velocity would that be?

Joined:
Nov 20, 2012
Location:
JirinPanthosa
The speed of light.

Joined:
Feb 12, 2011
Location:
astral plane
Undefined. You can't transform to a photon at rest, for any reason including to see how fast the other is going relative to it, because photons always move at the speed of light.

Joined:
Jan 14, 2004
Location:
Indeterminate
Yeah, there is no inertial frame of reference in which one can be at rest relative to a photon -- kind of a downer answer really as it was Einstein who posed the question about what would it be like to travel with a beam of light.

Of course, if it weren't for the Higgs field, all particles would travel at c and we couldn't have this discussion.

Last edited: Feb 1, 2019

Joined:
Feb 12, 2011
Location:
astral plane
I thought exactly the same thing at first, but on the other hand there is a powerful uniformity to the idea that c is an invariant.