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If the speed of light slows down in a gravitational field and the speed of gravity equals the speed of light then doesn't that imply that the speed of gravity also slows down in a gravitational field? So if the speed of gravity slows down would that not make it less effective in slowing down light?

Quote from: jeffreyH on 21/03/2015 01:04:46If the speed of light slows down in a gravitational field and the speed of gravity equals the speed of light then doesn't that imply that the speed of gravity also slows down in a gravitational field? So if the speed of gravity slows down would that not make it less effective in slowing down light?No. The speed of light refers to speed at which light moves through space. However the speed of gravity is the speed at which changes in the metric, i.e. space. take place. Therefore the same reasoning which shows that light slows down in a gravitational field cannot be used to show that the speed at which changes in the metric, and thus space. take place.

No. The speed of light refers to speed at which light moves through space. However the speed of gravity is the speed at which changes in the metric, i.e. space. take place. Therefore the same reasoning which shows that light slows down in a gravitational field cannot be used to show that the speed at which changes in the metric, and thus space. take place.

Quote from: PmbPhy on 21/03/2015 02:19:31No. The speed of light refers to speed at which light moves through space. However the speed of gravity is the speed at which changes in the metric, i.e. space. take place. Therefore the same reasoning which shows that light slows down in a gravitational field cannot be used to show that the speed at which changes in the metric, and thus space. take place.This doesn't sound correct, since the speed of light is, essentially, the speed of causation and all changes to the speed of light can be represented as time dilation.The standard answer to this question, from General Relativity sources, is that gravity propagates at the speed of light.

If the speed of light slows down in a gravitational field and the speed of gravity equals the speed of light then doesn't that imply that the speed of gravity also slows down in a gravitational field?

So if the speed of gravity slows down would that not make it less effective in slowing down light?

Gravity is gravity. our (ahem) safety net for a universe. Its reach is presumed infinite, and it must be dynamically updating itself constantly as everything is in relative motion. Those 'updates' are what is defined to 'c', but if you think of it in terms of you, doing a sharp course correction in a 'flat space', you will find inertia acting on you. Depending on definitions you can think of that as a result of a Higgs field existing everywhere, or just 'gravity' existing everywhere. But I still think 'c' will be involved in the 'action and reaction'.

The standard answer to this question, from General Relativity sources, is that gravity propagates at the speed of light.

You can find much debate about this.

In particular:...sorry, you cannot view external links. To see them, please REGISTER or LOGIN[For static fields, such as the electrostatic field connected with electric charge, or the gravitational field connected to a massive object, the field extends to infinity, and does not propagate.

Quote from: PhysBangThe standard answer to this question, from General Relativity sources, is that gravity propagates at the speed of light.I agree with that statement. If you thought that I implied otherwise then I don't see how. If so then please point it out for me? Thanks!