I'm sure many will cringe at the mere sight of this question. I've only had a brief introduction to relativity so I am having difficulty conceptually with a problem a professor posed to me. His question is of standard Bob and Alice form. "Bob is on a flatbed train, Alice is in the station. When bob passes Alice (x=0) he flashes a flashlight." Now we both agree Alice and Bob independently will observe the wavefront moving away at c. My issue is I can not conceptualize how in Alice's frame she also sees the wavefront moving away from bob at the speed of light and simultaneously away from herself at c while Bob is clearly moving with some velocity along the direction of propagation of the light flash. Any insight will be much appreciated.