In A Very Short Introduction: Black Holes by Katherine Blundell, the author discusses the merger of two black holes in a binary system:

The energy released in the merger of two supermassive black holes in a binary system is staggering, potentially more than all the light in all the stars in the visible Universe. Most of this energy is dumped into gravitational waves, ripples in the curvature of spacetime, which propagate across the Universe at the speed of light. The hunt is on for evidence of these waves.

What's exactly meant by that?

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    $\begingroup$ It's just colloquial language for the energy being converted to gravitational waves. Similar to e.g. friction causing kinetic energy being converted to thermal energy, which is then converted into electromagnetic waves. $\endgroup$
    – pela
    Jun 27 at 13:12

2 Answers 2


When two black holes merge, the gravitational mass of the final black hole is lower than the sum of the masses of the two merging black holes. Where has this mass gone?

The answer is that it has been turned into energy in the form of gravitational waves. These are produced during the merger process at an accelerating rate, with peak power emitted just as the event horizons of the two black holes merge.

The gravitational waves propagate outwards at the speed of light and the energy they carry is lost from the system.

Your text is referring to gravitational waves from merging supermassive black holes. These have not yet been detected because the gravitational waves are emitted at frequencies of about twice the orbital frequency of the merging system. For supermassive black holes, these frequencies are far below the 20-2000 Hz sensitivity window of current ground-based gravitational wave detectors and so other means are necessary to search for them.


Minkowski space-Ricci Tensor curvature explains that when mass is created, it creates a "curve" in space. By doing so, any wave-particle travelling across space-time will eventually dip into this well. When it does, the kinetic energy of going "down" the well causes a gravitational field around it for a split second before reaching ground state. When coming out from the well assuming it hasn't dissipated or been absorbed, it creates 'negative' gravitational fields (i.e. why the Higgs-boson is a big deal), as it gathers mass in order for it to essentially "climb" back up. The whole idea is a bit of a mad-man approach to how energy "dumps" onto a heavy gravitational field, but the idea is pretty swell! Hope this Layman's interpretation tries to explain it.


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