# The Naked Scientists Forum

### Author Topic: At what speed does gravity propagate?  (Read 1653 times)

#### George Knight

• Guest
##### At what speed does gravity propagate?
« on: 11/07/2008 10:07:44 »
George Knight asked the Naked Scientists:

Recently I was listening and the comment was made that gravity acts much like light.

I seem to recall that it was said that "if the sun was plucked from the solar system it would take 8 minutes before the earth would begin  a straight trajectory rather than orbital".

This may not be true. Would you please clarify?

Thank you.

What do you think?

#### lightarrow

• Neilep Level Member
• Posts: 4586
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##### At what speed does gravity propagate?
« Reply #1 on: 11/07/2008 12:45:36 »
George Knight asked the Naked Scientists:

Recently I was listening and the comment was made that gravity acts much like light.

I seem to recall that it was said that "if the sun was plucked from the solar system it would take 8 minutes before the earth would begin  a straight trajectory rather than orbital".

This may not be true. Would you please clarify?

Thank you.

What do you think?
A gravitational perturbation (e.g. a grav. wave) propagates at light's speed.
149.5*106 km/299,792.458 km/s = 8 minutes 18 seconds.
« Last Edit: 11/07/2008 19:28:49 by lightarrow »

#### graham.d

• Neilep Level Member
• Posts: 2208
##### At what speed does gravity propagate?
« Reply #2 on: 11/07/2008 13:33:35 »
Yes, gravitational waves propagate at light speed (it is generaly believed) though we have yet to physically detect Gravitational waves. The concept of plucking away the sun as a idea to explain that we would not notice for 8 minutes is OK to a certain level, but it can lead to false conclusions if expanded upon too far. The fact that you can't actually do this is actually part of the laws of physics. You can (in theory) tow the sun away; you cannot just destroy its mass, only move it.

#### The Naked Scientists Forum

##### At what speed does gravity propagate?
« Reply #2 on: 11/07/2008 13:33:35 »