Is there an absolute amount of shelf life to them
Very often a virtual particle–antiparticle pair appears and because they’re very happy they started existing, they immediately hug each other not knowing that will cause them to annihilate each other and disappear.
Every once in a while, the pair appears in a very interesting position: one is outside the event horizon of a black hole (let’s call this one Pinocchio) and the other inside it (let’s call it 3735928559). Because nothing can escape a black hole, they can’t really hug, so Pinocchio says “I’m a real
boyparticle” and stops being virtual and becomes real, while 3735928559 continues its descent intomadnesssingularity.Unfortunately, the process means there now exists something (Pinocchio) where there wasn’t anything before and that takes energy. And that energy comes from the particle that stayed behind which is now part of the black hole, so it effectively takes energy out of the black hole. You may have heard that energy cannot be created or destroyed, only transformed, that’s essentially what happens here.
The Pinocchios go away from the black hole, so they can end up basically anywhere in the universe.
As for the timescales, they entirely depend on the black hole’s size. Really tiny black holes evaporate in a matter of seconds, the supermassive ones in a matter of trillions of trillions of trillions of trillions… years.
In fact, black holes will be the last macroscopic structures to exist in the universe because the evaporation is extremely slow - every planet and every star and every gas cloud and every atom will cease to exist long before the last black hole evaporates.
So is the energy that pinnochio gives off the hawking radiation?
Yep, pretty much, though the particle itself is the energy, not some kind of energy it gives off.
Mass and energy are convertible between each other, so you can think of it as the black hole losing mass equal to the mass of the particle, if it helps.
Correct or more accurately it is the Hawking radiation.
I love it when the math checks out years later chefs kiss
I don’t know if this is true but it was very fun to read.
Depends on your definition of “true”. Is it scientifically true? No. Is it the actual science simplified a lot so it can be read by a non-physicist human being? Yes.
Reserving judgment permanently less a day on that exhibit, Counsellor
How can stuff have negative mass in the true sense of that?
In this context, “negative mass” is a mathematical convenience rather than an actual particle having negative mass.
Think of it more like “energy required to pull apart a matter-antimatter pair”. In the vacuum of space, the energy that created the pair gets returned when they annihilate. But when near a blackhole, it had to “burn” some of its energy to interrupt that process. Energy is mass, so the blackhole gets less massive.
Mind you this is a very basic explanation of it. It’s just another quantum whackyness of our universe.
How does adding a particle to the black hole remove energy from it?
It’s not a particle in the regular sense you might know, like an electron. The pair that comes into existence is meant to annihilate immediately (meaning there’s zero energy gain or loss) but because of where it appeared it can’t.
When it appears as I described, there suddenly exists a real particle in the universe outside the black hole, so the universe gained +1 in energy.
But energy can’t be created or destroyed, so that +1 means somewhere there must be a -1. And that somewhere is the black hole which caused the particle to exist in the first place by swallowing its pair.
It’s not very intuitive, that’s the fun part about quantum mechanics: nothing is intuitive.
The entire reason the particles can come in to existance is because the black hole curves spacetime enough to ‘eat’ one of the pair. It only exists because of the black hole. The particle leaving the black hole takes energy away because that area of spacetime now has less energy in it, meaning the black hole shrinks. The black hole isn’t magically adding energy to the space around it in order to create these pairs.
If you throw a ball away from you, yes you feel the force, but now you’ve sent a bunch of energy away from yourself in the ball. In effect, the black hole is ‘throwing’ particles away from itself by the simple act of eating part of the spawned particles.
I’ve explained it poorly, but PBS Spacetime has several great episodes on the specific phenominon.
Deadbeef
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Nearly correct, but it’s not about negative mass, because that doesn’t exist as far as I know. Rather it is about matter and antimatter which have other opposite properties, the mass is the same for both. That’s why it doesn’t matter which particle goes back into the hole, because the creation of the particle pair used up some of the energy (and therefore mass) of the black hole and if both fall back, nothing changes. But if one escapes, a minuscule amount of the mass of the black hole left its event horizon and thereby decreased its mass.
Would it be possible for the antimatter particle to be ejected instead of the ‘real’ matter particular?
The majority of Hawking radiation is composed of photons, and photons are their own anti-particle. But black holes should radiate just as many positrons as electrons.
and photons are their own anti-particle.
How are they their own anti-particle? Because they destructively interfere or something?
🤷♂️ because when we flip all their quantum numbers we still call them a photon? They have no charge, so if you flip their charge they still have no charge. They have no color, so if you flip their color they are still colorless, etc. The ability of a particle to interfere with itself is a general property of all particles, because all particles are probability waves, so this isn’t special to a photon.
“because math” got it.
I did use a lot of words to say “I don’t know” didn’t I.
Yes, and it doesn’t actually matter. The anti-particle will then at some point hit a regular particle of the same type and release energy instead, leaving the universe with more energy which came from the black hole and the destroyed particle.
Ace covered it well enough, and I think you can find their “shelf life” using the math Hawking came up with to predict when a certain mass black hole will be fully evaporated. How accurately I’m not sure.
The actual form of the radiation emmited back into space from evaporation depends on the mass IIRC. So stellar to supermassive would show up as photons and neutrinos. As they shrink they get hotter for some reason (I’m just a layperson too) and then could emit stuff like electrons, muons, etc. Evaporation also accelerates as the black hole mass shrinks.
Not sure what happens when the black hole reaches the mass of something that’s not a black hole like a Neutron Star. Does the black hole singularity explode? Don’t know. That’s one idea vs just shrinking until it winks out of existence.
The evaporation increases because spacetime is bent more rapidly by smaller black holes than big ones. It’s the same reason you can enter a supermassive black hole without being spaghettified, because the curvature never reaches a point where there’s a huge difference between your feet and head, sort of thing.
That curvature drives the evaporation rate, because the particles flying off are virtual particles whos partner fell in to the black hole with it flying outward. That happens far less often when the curvature is so low that any given point around the black hole is almost flat spacetime.
