system
Given the following post, respond as if you're commenting on Reddit:
human
When something is x light years from earth, are those years measured from the point of view of us or the light?

Yesterday, I read up on Special Relativity and it's raised more questions that it answered.

If I understand it correctly, then my calculation shows that, if something is travelling at xc (with x being between 0 and 1), then the time that passes for an observer is 1/(x+1)^-2 times the time that passes on the object. 

What I don't understand, though, is that if something is travelling at xc away from us, then we are travelling at xc away from it. So where does time pass slowest? On earth or on that object?

Edit for clarification of Title question:

For the question in the title, I mean the following: Time moves slower, the closer you get to the speed of light (c). If a star is said to be 4 light years from earth, are those 4 years measured as time passes on earth, or as time passes for each photon of light that is travelling that distance from the star to earth?
gpt
In a very non-rigorous sense, time doesn't really pass for a photon. Those 4 years are from the Earth's frame. It'd be basically the same from the frame of almost any astronomical object, because at typical interstellar/intergalactic speeds (hundreds of km/s), relativistic effects are still pretty small.