When two black holes merge together, about 5% of their mass gets lost. Where does that information g

[Judi Lynn]

When two black holes merge together, about 5% of their mass gets lost. Where does that information go?

Ethan Siegel
Jan 5

Do merging black holes lose information? They absolutely must, according to General Relativity and the known laws of physics. Take two black holes, merge them together, and they lose mass. For the ten black hole-black hole mergers LIGO and Virgo have seen so far, each one has lost mass in the process: about 5% of the total, on average. So where does the information that was encoded by that mass go? That’s what our Patreon supporter Pierre Fransson wants to know, asking:

When black holes merge they [lose] energy through gravitational waves. Does this pose the same problem as Hawking radiation does, with respect to loss of information? Or is the information on what has gone into the black hole somehow encoded into the gravitational wave? And if it is could we someday hope to decode what went into the black hole using gravitational waves?

Let’s take a look at black hole information in general, and then let’s examine what happens when they merge.

Black holes used to present a tremendous puzzle for astrophysicists when it came to the idea of information. No matter what it is that you make your black hole out of — whether it’s stars, atoms, protons, electrons, antimatter, heavy elements, or exotic particles — there are only three things that matter for the properties a black hole possesses: its total mass, electric charge, and angular momentum.

More:
https://medium.com/starts-with-a-bang/ask-ethan-do-merging-black-holes-create-an-information-loss-paradox-6252874e14b9

[Igel]

1. Yeah, I like "Ask Ethan."

Might use some of his columns in a class I'm teaching. Sort of play "spot your ignorance" with my high-schoolers, who'll jump to the conclusion and when asked about the reasoning behind it has no clue whatsoever.

Worse yet, they'll have no clue that their eyes skimmed over 10 logical connection between facts that they have no clue about and didn't realize they were ignorant until specifically asked. Now, there's no way I can explain all the details, but at least I have a clue what the actual claims are, pros and cons, context and competition.

More of the "appeal to authority" approach if they like what it says--such authority must not be questioned; and "ignore authority" if they don't, because, well, ad hominem. The last thing that's wanted is understanding, whether they like or loathe the claim.