I was thinking that given that GW's can be created by the merger of both black holes and neutron stars I don't see why any two colliding objects wouldn't also be able to create gravitational waves, such as two hands clapping. What do people think of this?

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    $\begingroup$ Yes, but they’d be very faint. $\endgroup$ – knzhou Apr 14 '18 at 11:53
  • $\begingroup$ You create gravitational waves every time you walk, or every time your heart pumps, or almost any time anything moves. $\endgroup$ – Javier Apr 14 '18 at 17:18

I once saw an estimate to the effect that if you spun a nuclear submarine around its short axis at $10^6$ rpm (corrected by Ben Crowell) you would radiate GW having a power equivalent to an ant walking up a hill. So yes, but you get the idea. That's why you need enormous mass acceleration to be able to see anything. Just as knzhou says.

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    $\begingroup$ For your nuclear submarine, I get $(G/c^5)(mr^2)^2\omega^6\sim10^{-29}\ \text{W}$. For an ant crawling up a hill, I get $\sim10^{-6}\ \text{W}$. To get the sub's radiation up to ant-power levels, I have to make the frequency $10^6$ rpm. $\endgroup$ – Ben Crowell Apr 14 '18 at 14:56
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    $\begingroup$ This may be a bit off-topic, but any two particles interacting should produce gravitational waves. Even though infinitesimally low energy, they should still carry spin. Why don't we observe missing spin in those interactions? $\endgroup$ – S. McGrew Apr 15 '18 at 5:33

Yes, hands clapping is physically comparable to an oscillating spring as shown here https://ned.ipac.caltech.edu/level5/ESSAYS/Boughn/boughn.html in Figure 1. The spring emits gravitational waves. Note that a time dependent mass quadrupole moment must exist for any system in order to emit gravitational waves. A counterexample would (theoretically) be a spherical symmetric supernova. In this case the mass quadrupole moment is zero. A 'real' supernova proceeds with some asymmetry though.


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