# Question regarding gravitational waves

1. Dec 19, 2011

### blueberrynerd

1. The problem statement, all variables and given/known data
A star 10 light-years away explodes and produces gravitational waves. How long will it take these waves to reach the earth?

2. Relevant equations
The problem is, I don't know what equations to use or if it's just a matter of simple math.

3. The attempt at a solution
My answer is that it takes 10 years to reach the Earth, but something tells me that this is wrong. Can anyone help me solve this problem or tell me if my answer is correct?

2. Dec 19, 2011

### cepheid

Staff Emeritus
As far as I know, gravitational waves propagate with speed c.

3. Dec 19, 2011

### Markus Hanke

The answer will depend on whether you are required to take into account the metric expansion of space; if not than your answer is correct as the waves propagate at the speed of light.

4. Dec 19, 2011

### blueberrynerd

Do all gravitational waves propagate at the same speed? Is it only the magnitude which varies, according to the body of matter that produced the waves?

5. Dec 19, 2011

### Dick

For small amplitude gravitational waves they propagate at speed c. An exploding star counts as a small amplitude wave. Just use c.

6. Dec 20, 2011

### blueberrynerd

Thanks a bunch!