Haven't had one of these for awhile. This thread is for questions or comments that you've felt silly about not knowing/understanding. Let's try to exchange info that seems obvious, knowing that due to the illusion of transparency it really isn't so obvious!
Assume there are observers at A and B, sitting at rest relative to each other. The distance between them as seen by them is X. Their watches are synchronized. Alice, sitting at A, emits a particle when her watch says t0; Bob, sitting at B, receives it when his watch says t1. Define T = t1-t0. The speed of the particle is V = X/T.
If the particle is massive, then V is always smaller than c (the speed of light). We can imagine attaching a clock to the particle and starting it when it is emitted. When Bob receives it, the clock's time would read a time t smaller than T, given by the equation:
t = T (1 - V^2/c^2)^(1/2) (this is the Lorentz factor equation mentioned by Plasmon).
As the speed V of the particle gets closer and closer to c, you can see that the time t that has passed "for the particle" gets closer and closer to 0. One cannot attach a clock to a photon, so the statement that "photons are not moving through time" is somewhat metaphoric and its real meaning is the limiting statement I just mentioned. The photon is not "at two places at once" from the point of view of any physical observer, be it Alice and Bob (for whom the travel took a time T = X/c) or any other moving with a speed smaller than c (for whom the time taken may be different but is never 0).
Thanks, it sounds like Tyson just said something very misleading. I looked up the Lorentz factor equation on Wiki, and I got this:
gamma = 1/[(1 - V^2/c^2)^(1/2)]
Is that right? If that's right, then the Lorentz transformation (I'm just guessing here) for a photon would return an undefined result. Was Tyson just conflating that result with a result of 'zero'?