ELIF: how is time relative?
In: Physics
Lets say you are on Earth, but you have a friend that lives on Mars. For some reason, suddenly the sun goes out/disappears. It takes 8 minutes for the light the sun was emitting to stop reaching you. You just happen to have a magic phone that can talk to your friend on Mars instantly. You call him up and tell him the sun has vanished. He is confused and has no idea what you are talking about because he can still see the sun so he hangs up on you. 4 more minutes later, he calls you back on his magic phone and apologizes, the sun has just disappeared for him too!
Four years later, your distant relative that lives on a planet orbiting Proxima Centauri calls you up on his magic phone asking why the hell the sun just disappeared. Of course this is old news to you by now.
For each of the three people in this story, you, your friend on Mars, and your distant relative on Proxima Centauri, they all saw the same event occur at a different time. Time is relative because things do not travel instantly. It takes time for changes in one area of the universe to propagate to others. This is called the speed of causality and just so happens to be the speed light (and other electromagnetic/gravitational waves) travels as well.
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