I’m asking this because there is a scifi book I’m reading, and in the book there’s a scene where someone is communicating with a person in a spacecraft moving at lightspeed. I know their ability to communicate would probably not be possible, but let’s just put that aside for a second. Hypothetically, if you could communicate with someone moving lightspeed, would the time dilation make it so that they would appear to be moving and speaking very slowly relative to you?
Exactly at the speed of light, the γ-coefficient would be infinite and so would be the time dialation. The eigen time of the moving person would thus be infinitely slower than the non-moving person. From the perspective of the stationary person, the time of the moving person would stand still and thus the person would never say anything. Very close to the light speed, when the coefficients are large, this problem eases but persists. The stationary person would have to wait for very long (and use a massive Doppler shift of the moving signal) to perceive something. At the end of the conversation, it will have lasted much longer for the stationary person, spending years on this. The twin paradox would basically kick in as well. If the moving person is at a speed too close to the speed of light, the stationary person might die before the conversation is over—assuming the stationary person is not immortal. That is kind of a very slow motion, yes. What a dedication, spending a lifetime on a person who can’t slow down ;-) Funny enough, from the perspective of the moving person, the effect is reversed.
Interesting. That makes sense, thanks for explaining