# The Naked Scientists Forum

### Author Topic: How fast does gravity travel  (Read 2251 times)

#### Tyron

• Guest
##### How fast does gravity travel
« on: 16/11/2008 10:40:29 »
Hi Chris,

thanks for your input with Talk Radio 702, I always look forward to it!

could you possibly answer this question I have, because nobody I speak to has a clue...
*Does gravitational force travel at a particular speed?
for example, if the sun had to suddenly be taken away we would still have light for about 8min. and 20 seconds right?
but what about our orbit around the sun, would we IMMEDIATELY go out of orbit, or would that also take time??

that's my ever-elusive mind boggler!
I personally think that it would be IMMEDIATELY, because I can't see how it could be something physical...

many thanks

Tyron Crowe

What do you think?

• Neilep Level Member
• Posts: 1451
##### How fast does gravity travel
« Reply #1 on: 16/11/2008 12:28:34 »
The theory is that gravitons travel at the same speed as light, so yes, if the sun were to inexplicably vanish we would remain in our orbit for 8 minutes or so.

#### lyner

• Guest
##### How fast does gravity travel
« Reply #2 on: 17/11/2008 15:06:12 »
You don't need anything as unthinkable or extreme as the Sun's disappearance. You would expect a varying gravitational potential from any pair of mutually orbiting bodies, for instance two massive binary stars*. The phase of that variation would lag behind their motion but, of course, be in phase with what you saw from your observation point because the light and G variations would take the same time to reach there.

*Despite what people say, the position of the Centre of Mass doesn't tell the whole story if you are not actually at 'infinity'.

#### The Naked Scientists Forum

##### How fast does gravity travel
« Reply #2 on: 17/11/2008 15:06:12 »