# Time dilation of baseball

1. Jul 15, 2014

### Tranceform

1. The problem statement, all variables and given/known data
A baseball player at home plate hits a pop fly straight up (the beginning event) that is caught by the catcher at home plate (the ending event). Which one or more of the following obeservers record(s) the proper time interval between the two events? (a) A spectator sitting in the strands (b) A spectator watching the game home on TV (c) The third baseman running to cover the play

2. Relevant equations
$$\Delta t=\frac{\Delta t_{0}}{\sqrt{1-\frac{v^2}{c^2}}}$$

3. The attempt at a solution
As I understood time dilution it occurs when an object is moving and the obeserver is not inertial with the movement of the object. In this case neither of the observers is moving with the object (the baseball) so noone of the observers should be able to records the proper time interval between the two events. Only a clock that was a attached to the baseball itself would do that. Please explain why this view is not correct.

2. Jul 15, 2014

### Staff: Mentor

Is time for the baseball relevant?

Check the problem statement - proper time of what is asked for?

3. Jul 16, 2014

### Tranceform

Proper time between the two events. I guess then that since the events take place at the same place, the proper time is measured according to an observer inertial for those two places, which would be a stationary observer.

However if the time measured would have been only on the baseball going up (but not down), the proper time measured would have had to move along with the baseball?

4. Jul 16, 2014

### Staff: Mentor

Right.

What's the endpoint you consider here?
The highest point of the ball? Then neither is right, as proper time corresponds to the time you see in an inertial (not accelerated!) frame moving from one point to the other. As we do not consider general relativity here, the ball is accelerated.
Still the surface? Then see the original problem.