[ruds]

I think the question is: given a 3-body system with objects A, B, and C, is C's gravitational effect on A altered in any way by the position of B, or are B's and C's effects on A independent?

The reason for the question, I think, is because of an intuition built up around EM. In the system

A B C

B can block and otherwise interfere with C's EM radiation so that its effect on A is different depending on B's location.

[fhars]

No, if you want to think of gravity in analogy to light, you can see every mass as analog to a fully transparent light source. There is nothing in this universe that can absorb gravity.

[Steuard]

LIGO was able to detect gravitational waves, which I'm pretty sure must require non-zero transfer of energy in one form or another. (I'm hedging a little only because I know LIGO was measuring relative changes in metric distance, which might possibly not require absorbing energy... but just intuitively it's hard for me to fathom any transfer of information without a transfer of energy: it simply shouldn't be possible.) But 1) it's a remarkably small loss of energy, since the gravitational coupling to matter is so weak, and 2) LIGO is very specifically reacting to gravitational waves rather than to static (or quasi-static) gravitational fields, and the absorptive properties there will certainly be different (just as they are for electromagnetism).

[fhars]

General relativity will probably add some effects like that, but then quantum electrodynamics adds light scattering off of light, so the analogy is still ok as far as analogies go.

[mikorym]

> fully transparent light source

Thanks. So, in the analogy between gravity and light, you have to change all "massive bodies" to "fully transparent light sources" to make the analogy complete.

A nontransparent light source would not translate as a (straightforward) massive body.