# A Bus travelling at a very high speed.

1. Sep 4, 2011

### Naveen123

A bus travels at a very high speed. It's time slows down.

What's the mechanism by which this happens?

2. Sep 4, 2011

### HallsofIvy

No, it doesn't. As far as people in the bus are concerned, everything happens at normal speed. Their watches run at normal speed, they breath normally, they walk up and down the aisle as usual.

Also, remember that this is relativeity. It makes no sense to say "travels at a very high speed" without specifying relative to what that speed is measured. If a bus went by me at relativistic speed, relative to me, and it were possible to observe the people on the bus, I would see them moving slowly, breathing slowly, their watches running slow, etc.

However, again, this is "relative". From the point of view of the people in the bus, they are stationary and I am moving very fast relative to them. They would see me moving slowly, breathing slowly, my watch running slowly, etc.

What do you mean by "mechanism"?

3. Sep 10, 2011

### Agerhell

Actually if the bus is travelling westwards clocks on board that bus will tick faster then they would it the bus had stayed in the garage. If, on the other hand, the bus would travel eastward clocks on the bus will start ticking slower. This is becaue the earth rotates "eastwards".

What actually matters is what velocity the bus will have in relation to the center of the earth... This has been confirmed in an experiment called the "Hafele and Keating experiment". You can google it. In that expreiment they were using aeroplanes and not busses but the physics is the same.

I am not qualified to explain why general relativity predicts this...

4. Sep 10, 2011