Surely the conservation of baryon numbers is just a rule for reactions. I don’t see how crossing the event horizon changes anything. Remember from the POV of the baryon, it never crosses the event horizon. It’s not really ‘destroyed’, it just becomes unobservable to the external universe.
Remember from the POV of the baryon, it never crosses the event horizon. It’s not really ‘destroyed’, it just becomes unobservable to the external universe.
I think this is backwards - for an outside observer nothing ever crosses the event horizon, from the point of view of anything falling towards the event horizon it takes a finite amount of time to cross the event horizon.
How does this interact with the Hawking radiation? ie I throw something into the black hole, how much time do I wait before the Hawking radiation from that matter to manifest itself?
From your point of view - assuming you do not fall into the black hole yourself - nothing you throw into the black hole ever crosses the event horizon so you will have wait forever. You can only see something cross the event horizon if you cross the event horizon yourself and you will see everything cross the event horizon at the moment you cross the event horizon.
My friend is kind of confused. Why wouldn't an observer outside of the event horizon see things falling into it? He says you can glean information from a thing that's outside of the horizon, but a thing falling into it should cease to be observable, at least by his understanding of black holes. My galaxy-sized brain understands this, of course, but my friend's pea-brain doesn't.
An observer outside the event horizon has to accelerate to avoid falling into the black hole itself and in the resulting frame of reference of this observer the horizon of the black hole coincides with future infinity and therefore everything falling into the black hole only reaches the event horizon infinitely far into the future. You can watch Leonard Suskind's lecture on that [1], falling into a black hole starts at about 53 minutes, but depending on your background you may want to start earlier, maybe even several lectures earlier. Looking at those Penrose diagrams is probably the easiest way to see what happens even if it will probably still not make intuitive sense.
True, but from the point of view of an observer at infinity, the baryon falls and comes to a halt, while the event horizon of the black hole expands and encompasses it (or would, if you could measure the diameter of the black hole with sufficient precision).
This is just the essence of the information paradox, expressed in terms of baryon and lepton numbers. Either the Hawking radiation that comes out is ‘correlated’ with the matter that fell in (meaning that black holes have hair) and information is preserved, or they’re not, and information is destroyed. That’s literally the crux of the matter.
That’s a good point, I wasn’t thinking about it in terms of the information paradox, but then the recently proposed solutions look like they have a good chance of panning out.
But anyway I still don’t think this is really an issue regardless. The same could be said of the cosmic event horizon. Vast swathes of the universe are unobservable and causally disconnected from us due to the expansion of the universe separating us at faster than the speed of light. Again, no Baryons are being destroyed in this process, they’re just becoming unobservable _to_us_.
As I see it, there’s a vast cognitive chasm between the cosmic event horizon and the event horizon of a black hole, as the former preserves “continuity of locality” (my term) whereas the latter does not. Basically the the former is only an event horizon for us who are very distant from it, whereas the black hole’s horizon is an abrupt threshold in space. I don’t think it’s healthy to confuse the two.
The locality is all equally continuous in all these cases.
Someone near the black-hole horizon will see nothing unusual, and will not experience a horizon unless they are accelerating like mad to stay there. But someone doing that in flat space will see a horizon too -- see the Rindler coördinatization[1] of Minkowski space. It even has an analogous Rindler horizon, which seems to emit particles from the Unruh Effect[2]. I say seems to because particle number isn't invariant under acceleration. An outside observer will see a particle detector go off, but will interpret the accelerated detector as causing the particles, rather than the horizon.
"Just a rule for reactions" drives quite a lot of physics. Conservation rules are how to describe all of the things that do not happen: why a hammer doesn't vanish, why all of your electrons do not turn into positrons, and so forth.
That's what is so fascinating ... you have this odd topological boundary and it creates a violation in known rules.
