# Another retarded question

1. Feb 29, 2008

### Matthieu

Let's assume we have two "somethings" in space, they get away from each others. The speed of one of them is around 150,000kms/sec, very fast but less than the speed of light, the other one goes the totaly opposite way at 200,000kms/sec.

An observer on one of these would see the other element "going back in time" wouldn't he?

2. Feb 29, 2008

### malawi_glenn

no, he would just se the other ones clock go slower than his own.

3. Feb 29, 2008

### NerfMonkey

Wouldn't the observer see the other object flying away at the speed of light? No matter what the speeds of the two objects are their speeds can never add up to more than c, right? So his clock would be moving at normal speed and he would see the other object's clock either stop if it was receding at c, or moving extremely slowly if it was receding at less than that, correct?

Would this observer see the other object moving away at c or slightly less?

4. Feb 29, 2008

### malawi_glenn

Use addition of velocity theorem and time dilation theorem.