2

I do not know much physics so please try to answer as simply as possible. I am probably confused but I recently learned that in Special Relativity (you can tell that I don't know much physics), the faster an object is moving, the more time slows down for that object. I also learnt that it is slowed down by a factor $\gamma=1/\sqrt{1-v^2/c^2}$.

However, how is the velocity measured? From my reference frame, I never move. If I walked away from someone, presumably time would slow down ever so slightly for me compared to the other person. However, in my reference frame, I just see the other person moving away from me. Which person does time slow down for and why?

AccidentalFourierTransform
  • 53,248
  • 20
  • 131
  • 253
Matthew Barber
  • 63
  • 2
    If you fly past me in a rocket then your measure of time will appear to me to have slowed down. But for you, on your rocket, time will feel like it's passing normally. Similarly, from your point of view, my measure of time will appear to be slower. So what happens when we come back together and compare time? Well this is the so-called twin paradox. Addressed many times on this site (e.g.). – lemon Feb 28 '16 at 17:00
  • You might want to see my recent very elementary answer to essentially the same question at http://physics.stackexchange.com/questions/240124/time-dilation-confusion/240223#240223 . – WillO Feb 28 '16 at 19:45
  • 1
    The absolute value of the velocity of the movement would be the same from both observer systems. That's part of the facts of relativity: $|{v_{AB}}|=|{v_{BA}}|$. There may be a disagreement about the direction (we usually chose the coordinate systems parallel, so that the two velocities have opposite direction). This leads to exactly the same time dilation factor. – CuriousOne Feb 28 '16 at 20:37

0 Answers0