how hot could it get inside a black hole?
Black holes radiate virtually no energy, much less anything we'd consider heat. But that doesn't mean their innards aren't superheated to cosmic extremes...
The old adage about nothing escaping a black hole’s gravitational pull isn’t strictly true. Despite being cosmic vacuum cleaners, ferociously feeding on anything that strays too close and locking the rendered mass of raw quarks, photons, and gluons into infinite quantum states within its dark innards, black holes actually do have an honest to goodness temperature. It’s an infinitesimal fraction of a degree, yes, but it’s there. By contrast, as the dust and gas being consumed by such a gravitational monster can whip around the event horizon so fast, it heats up to millions of degrees, spewing out intense radiation astronomers can detect. So if a feeding black hole has a searing hot disk of material around it and emits just an infinitesimal fraction of a watt to the outside world, what about the temperature inside this bizarre object? Since it’s formed by a sudden, violent implosion that can actually shatter atoms down into their most primitive particles, what would its interior be like?
In previous posts about black holes, I’ve alluded to the idea that inside a black hole should be maelstroms of raw energy, chaotically flowing in opposite directions and yet through one another. We don’t really know if that would be the case since we can’t exactly peek inside the event horizon, but the math which predicts how black holes form hasn’t let us down yet, and it’s the same math showing us how tumultuous the anatomy of objects like this should be. Remember that the core of a star about to collapse in a hypernova could be burning at up to 1 billion °C and as it implodes into a black hole, the annihilation of all the protons and neutrons is bound to crank up the heat even more. But that heat is now trapped in a self-gravitating cavity of space and time. It only cycles in streams and currents, unable to get out until it emits enough Hawking radiation and evaporates over countless trillions of years. Rather than billions of degrees, we’re more than probably talking about as much three magnitudes more, like the quark-gluon plasmas created in particle colliders. When the thermostat is set to roughly 4 trillion degrees, protons and neutrons melt, leaving only quarks and various bosons flowing a bit like a liquid, but with virtually no viscosity, able to move in opposing directions at the same time.
Similar conditions are thought to have been around femtoseconds after the Big Bang, as quark-gluon plasma shot out into the newly formed bubble of space-time, expanded, and cooled to begin baryogenesis. And we’re likely to see something very much like this happening within a black hole where such plasmas are trapped in conditions beyond extreme, compacted to the very limits of meaningful density. But while the early universe is big enough to allow these torrents of energetic point particles to expand, slow down, and combine into matter and antimatter, the conditions in a black hole should be too extreme to allow for that. Any new particle wouldn’t stand a chance, torn apart within an instant of its creation. It could even be possible that quarks are torn apart somewhere deep inside these gravitational monsters into something more primitive, resulting in a current of energy much closer to the instant of the Big Bang. Considering how close black holes’ temperature, pressure, and density should approach the very moment of the universe’s birth, it’s little wonder that so many significant theoretical frameworks for the Big Bang rely on trying to understand the bizarre objects’ structure and internal mechanics. It really is a shame we can’t peer inside these gravitational ghosts because the things we could learn might just rewrite what we think we know about the birth of the cosmos we inhabit.