3
$\begingroup$

Is it possible that all moving particle release gravitational wave?

I was trying to study gravitational wave and a question stuck in my mind. If any mass can bend space time and is moving it will also create ripple in space time. And as every thing in space is moving, why do we detect only a few gravitational waves.

Improve this question
$\endgroup$

1 Answer 1

Reset to default
5
$\begingroup$

Is it possible that all moving particle release gravitational wave?

No. For example, a mass moving at constant velocity does not radiate gravitational waves. (It has a time-dependent gravitational field, but that field doesn’t carry energy away like a gravitational wave does.) Neither does a spherically-symmetric spinning mass radiate, even though all parts of it are accelerating.

However, asymmetric accelerated motion tends to produce gravitational waves. For example, when you wave your hand you produce a tiny gravitational wave. Unfortunately, this wave is so weak that it cannot be measured with current or foreseeable technology.

Technically, but leaving out some details, a system needs a changing mass quadrupole moment to radiate.

why we can detect only few gravitational waves

It takes very massive objects undergoing high acceleration — such as two black holes spiraling together — to produce a wave strong enough for our current technology to measure.

Improve this answer
$\endgroup$
6
  • $\begingroup$ A body moving at high speed (ex.: v/c = 0.5) is distorting (rotating locally) space-time (RR). Then isn't it creating a gravitational wave due to the move of this space-time distortion? $\endgroup$
    – athena
    Commented Jul 28, 2020 at 7:11
  • $\begingroup$ "at constant velocity" Which reference frame? Do you mean a geodesic? $\endgroup$
    – Valter Moretti
    Commented Jul 28, 2020 at 8:32
  • $\begingroup$ This is a perfectly good answer, but I thought I'd query the quadrupole moment statement. If a body were to oscillate as a dipole, then I think it would radiate. The reason why we mostly need to think about quadrupoles for grav. waves is, I think, simply that an isolated system cannot have a time-dependent dipole moment. But I suppose if two systems interact so that the dipole moment of each oscillates, then they can exchange energy and momentum with each other, or with other things, via the dynamic spacetime. Is that right? Would it be called grav radiation? $\endgroup$
    – Andrew Steane
    Commented Jul 28, 2020 at 13:33
  • $\begingroup$ @AndrewSteane Can you provide an example? I thunk the quadrupole moment of the combined system would be changing, $\endgroup$
    – G. Smith
    Commented Jul 28, 2020 at 16:27
  • $\begingroup$ I haven't thought this through very fully; I just thought you might be interested. For an example, put a big mass into oscillation on a spring, with the other end of the spring attached to planet Earth. To me standing nearby, the mass is moving to and fro so I am getting squeezed by its tidal gravity in some sort of dynamic way, which could for example heat me up. And I think the dipole term (of the local mass distribution, say within a few metres) will dominate if I calculate this. Even though the dipole of the total (mass + spring + Earth) is not changing. But I'm not sure. $\endgroup$
    – Andrew Steane
    Commented Jul 28, 2020 at 19:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.