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?
It’s just two objects moving apart. If I drive my car away from yours, it looks exactly the same as if you had driven away from me (once you delete all the frames of reference like the ground, because there is no ground in space). The other person gets smaller at the same rate.
Have you ever been in a car or train where you couldn’t see the ground, only another car or train next to you? And you see the other vehicle moving, but you can’t tell if it’s actually them or you moving? Same thing. It’s all relative.
I’m just confused as to how we could both experience time dilation at the same time. Isn’t our time only dilated in relation to each other? So if both our times were dilated there would be no relative difference and it would look like our clocks were in sync, no?
If you sit in an ambulance with the siren blaring, and you encounter another ambulance with its siren blaring in the opposite lane, you will hear the pitch of its siren at a lower frequency as it drives away from you, from the doppler effect.
The people in the other ambulance will hear your siren’s pitch at a lower frequency as well, for the same reason.
I might be missing something here. Is the doppler effect related to time dilation?
The actually true explanation is that special relativity only applies to reference frames without acceleration or nearby gravity.
So the fact that your clock runs slow as seen from earth and earth’s clocks run slow from your POV doesn’t cause a paradox.
There’s no way to compare clocks at this time, since information can’t travel faster than light.
When you decelerate/accelerate back towards earth, you leave the realm of symmetric time dilation and earth’s clocks will appear to jump ahead as you switch reference frames, so it’ll show more elapsed time when you’re back. But I’ve yet to find an intuitive illustration for that.