# Simultaneity

*Most recent answer: 12/02/2009*

Q:

1. Will two events that occur in the same place and at the same time for one observer be simultaneous to a second observer who is moving with respect to the first?
2. What would happen to the mass of a 1 kg mass as it approached the speed of light?
3. Time dilation does not really mean that the mechanism of a moving clock runs slower. What does it really mean?

- Sangbum (age 16)

Canada

- Sangbum (age 16)

Canada

A:

1. Yes.

2. It increases as 1/sqrt (1-v

3. It really runs slower as seen by us. As seen by them, ours really runs slower. (We're discussing simple Special Relativistic effects here. General Relativistic effects are also real, but with agreement between the observers about which clock is slower.)

Mike W.

2. It increases as 1/sqrt (1-v

^{2}/c^{2}).3. It really runs slower as seen by us. As seen by them, ours really runs slower. (We're discussing simple Special Relativistic effects here. General Relativistic effects are also real, but with agreement between the observers about which clock is slower.)

Mike W.

*(published on 12/02/2009)*