Hi! I understand that conservation of the moment implies that for a system of two bodies, for instance a pair of neutron stars, when one mass moves or accelerates in one direction, the other moves or accelerates in the opposite direction, which cancels out.

 

Though... Referring to this file pinched at Wiki

http://en.wikipedia.org/wiki/Gravitational_wave

 

the speeds and accelerations of both masses shouldn't attain the observer at the same time, if (not the case of the picture) the observer is in the orbital plane! When the masses are at 45° to the observer, both have a speed and an acceleration, and the effect of the nearest mass should attain the observer first, so they don't cancel out.

 

At least for electromagnetic waves, it would hold. It's a usual way to build antennas.

 

But not for gravitation? No dipolar, far-reaching wave through this phase lag?

 

Thank you!

If you have two separated masses, you should have the sum of the fields. But unlike the E&M case, you do not have opposite signs — the field of two like charges is not the same as for opposite charges. And the behavior for the radiation is a different case than the static field. Accelerating masses do radiate gravitational waves.

Masses are positive but their acceleration are opposite here.

If an accelerating mass radiates, conservation of momentum alone wouldn't suffice to cancel out dipolar radiation, thanks to the phase lag between the radiation by each mass.

I don't know enough about gravity waves to address this. But that's what you should look into.