knutsen@SRI-UNIX@sri-unix (08/30/82)
From: Andrew Knutsen <knutsen at SRI-UNIX> I sort of asked a question at the end of the FTL discussion on SPACE, and still havent really satisfactorily answered it or had it answered, so here it is again: Is EM radiation affected by time dilation? It seems to me that since a "fast" object experiences less subjective time than the rest frame, a red shift would be observed. If (say) a krypton atom has a certain peroid in one frame, the period might appear longer in the other frame. Of course this effect would add onto the doppler and other (gravitational) effects. My math skills left over from school seem to indicate the effect would be less than doppler by a factor of c^2 at low speeds, but it would dominate at high speeds. Also it seems like it should be independent of direction, so it would add to the red doppler shift but subtract from the blue. To compare the magnitudes I calculated the apparent period from the rest frame: doppler period = t + sc where t is the period in the rest frame and s is the radial distance the source travels during t = t + |Vr|tc where Vr is the radial velocity, and || is vector magnitude time dilation period = gt where g is gamma = t/sqrt(1-v^2/c^2) where v is scalar speed ~= t(1+v/c) or something like that, for low v = t + vt/c However as v approaches c, the doppler approaches (t+t*c^2) but the time dilation effect approaches infinity. Thus for any t there is a v at which the effects are equal, and for any v a t. Knowing some of these would help getting a handle on it... also this would mean an object moving towards us at a certain speed would show no shift at a certain frequency. This is assuming my assumptions and math are correct of course. Is this correct? Is there an article anywhere that explains this? These relativity effects never seem to stop producing interesting questions... Andrew