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Comment by sampo | Hacker News Reader

I find this a better explanation:

> But the team's calculations showed there were differences in the gravitational field around the black hole. Specifically, information about the composition of the black hole was stored in gravitons, a hypothetical elementary particle that mediates gravitational forces in quantum gravity. "We found that quantum gravity enables us to find the difference in the gravitational field," Calmet said. "There's a memory in the gravitational field of what went into the black hole."

https://www.livescience.com/black-hole-quantum-hair

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I’m confused how you can find that something is stored in a hypothetical particle. Is it only hypothetically stored?

The particle is hypothetical in the sense that scientists hypothesize it exists, but it hasn't been proven to exist. If it helps, you might think of it similar to the Higgs boson before the Large Hadron Collider.

They do calculations using a theory where gravitons are assumed to exist, and then their results are valid in that theory.

Wouldn't that just prove the theory is internally consistent, without any further indication it can explain real-world observations?

I think the way to think about it is, they "invented" a particle that has all the right properties to explain real world data. Then they can say, if this is right, we can do such and such experiments to observe it.

Note that the design of the experiment needs to be able to disprove theory. That is to say if the results don’t match calculations then their theory is falsified and we make progress.

Interesting to think that a successful experiment is one that disproves a theory, or, in other words, one where the numbers aren't the ones one expected.

https://en.wikipedia.org/wiki/Falsifiability

A successful experiment can also support a prediction. I.e., "using this model, we predict that a bagel with blueberry cream cheese will remain on the counter for 94+/-4 seconds before disappearing." The team will then release the data from their experiment, which either supports or disproves a model.

This kind of work is critical to refining theories and highlighting/fill gaps in knowledge.

Having a hypothesis that is consistent with both relativity and quantum mechanics, as they are currently conceived, is no small matter. According to one of the paper's authors:

"It was generally assumed within the scientific community that resolving this paradox would require a huge paradigm shift in physics, forcing the potential reformulation of either quantum mechanics or general relativity.

"What we found—and I think is particularly exciting—is that this isn't necessary."

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