[oewolf]

Hmm so if someone moves near the speed of light, time basically stops for everyone?

[ars]

Remember - he isn't moving near the speed of light THEY are. He is standing still.

But if he accelerates then things are quite different, and much more complicated.

[burgerbrain]

From which reference-frame are you asking?

[oewolf]

I'm just trying to wrap my head around the concepts discussed here.

I used to think about it as I explained in my previous comment. But now that ars is making these comments, it seems like I'm grasping something new.

[ars]

I'll do my best to help.

This FIRST thing to remember is that you can only measure speed by comparing with something else. There is no such thing as the concept of "I am moving", but rather "relative to them I (or they, it's interchangeable) are/am moving".

Now when you compare speeds you can also compare clocks, and the same principle applies - you can only measure time by comparing to someone else.