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Comment by mike_ivanov | Hacker News Reader

"black holes have a temperature that arises because each particle that falls into a black hole has an entangled particle that can escape as heat"

o_O

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I believe this is referring to Hawking radiation.

I'm not an expert, but normally particles don't have an entangled counterpart. Only virtual ones do, and those which fall in can have a counterpart which ends up being "radiated".

Perhaps the confusion is caused by the current understanding that any information (and mass?) that comes in will eventually get emitted back away.

"virtual ones .. a counterpart which ends up being "radiated"." -- but this is not how Hawking radiation works.

To be fair, it is the usual way HR is described in pop science articles. The reality of pair production outside of the event horizon, and one particle falling in while the other “steals” a bit of energy from the hole’s gravitational field is not described as often. It’s also equivalent to the same pair being produced with the inflating partner having negative energy.

Care to point out the error?

It's a form of redshift effect in curved spacetime. Any massive object stretches the spacetime in a way that the spectrum of the light emitted by that object shifts down from the point of view of a remote observer (remote - this is important). The larger the mass, the stronger the effect.

A black hole would create an infinite redshift (due to singularity inside of it) -- but only if infinitesimal EM frequencies were possible, which in turn would imply continuous spectrum. The energy of photons is quantized, therefore no truly infinite redshift is possible. The same applies to other particles.

Basically it's a raster effect that becomes apparent when you zoom up on a magazine photograph, or equivalently -- when you stretch a photograph printed on a rubber sheet, the only difference is that you stretch spacetime, not just space.

That’s part of it, but then you have to account for the role the event horizon plays, and inherently complicated things like wave packets scattering off of it. I can’t pretend to understand the process well enough to talk about it without resorting to heuristics.

Perhaps this could also help - https://physics.stackexchange.com/questions/251385/an-explan...

I wish science communicators would abandon the whole “virtual particle” terminology altogether. It creates a lot of confusion.

Matt Strassler has a good blog post on the subject.

https://profmattstrassler.com/articles-and-posts/particle-ph...

Part of the problem however is that science communication has become its own “field” typically staffed by miserably unqualified people on a shoestring budget. There are also few laurels and less money to be had in trying to give the public at large a faithful representation of the real science. By contrast rehashing decades old basics about black holes with lots of hand-waving sells papers, clicks, magazines, etc.

As long as fiendishly complicated subjects are relentless dumbed down in the name of “inspiring enthusiasm” rather than instilling facts, we’re stuck with this.

> normally particles don't have an entangled counterpart.

I believe this assumption is incorrect. Most particles do have an entangled counterpart.

https://www.quora.com/What-percentage-of-subatomic-particles...

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