# Gravitational Time and Length Change, Looking for mass formula

1. Nov 12, 2014

### mcjosep

Hi, Just curious if anyone knows of a formula that would show how mass changes in a gravitational field? I have seen the formulas for gravitational time dilation and length contraction (which are rather similar) and was wondering is mass changes the same way.

Thanks

2. Nov 12, 2014

### phinds

Mass does not change in a gravitational field.

3. Nov 12, 2014

### Staff: Mentor

What formulas have you seen for "gravitational length contraction"?

4. Nov 12, 2014

### mcjosep

Just to pick an extreme, a 1kg ball is a meter away from the event horizon of a black hole. So, to an outside observer, time is almost not moving at all for the 1 kg ball and its size has shrunk to almost a point due to gravitational length and time dilation but the ball would still be 1 kg?

5. Nov 12, 2014

### mcjosep

hmm i just figured since planck time and planck length are related by a factor of c that they would change the same.

6. Nov 12, 2014

### Staff: Mentor

What are you basing this on? What formula? Do you have a reference?

The Planck time and Planck length are not the same as the length of an object or its proper time.