10.6 How Fast Does Time Slow?

office hours

Is time dilation real or a matter of perception?

I’ve heard that these effects of motion on time affect the GPS (global positioning system). How is that?

If there is no universal notion of time when objects are in motion, how do we talk about the age of the universe? After all, the universe is expanding, so galaxies are all moving apart from each other.

What would happen if you had a version of the light clock with the ball of light replaced by a baseball whose speed behaved in the manner Newton would have predicted?