Sorry, Stephen Hawking, But Every Black Hole Is Still Growing, Not Decaying
“It remains true that every black hole that exists in the Universe should emit Hawking radiation, and that if you wait long enough, all of these black holes will eventually decay. But in our Universe so far, based on the black holes that actually exist, not a single black hole has even begun to decay in a meaningful way. The amount and energy of the radiation that’s out there, from starlight and left over from the Big Bang, ensures that black holes will absorb it and grow much more quickly than they lose energy from radiating it away.
Even though it’s been more than 45 years since Hawking first figured out that black holes do emit radiation, as well as what that radiation must look like, it’s far too faint and sparse for us to have ever detected it. Unless there’s a surprisingly low-mass black hole or we’re willing to wait an enormous, cosmic time for the Universe to cool, we’ll never be able to see it. Black holes are growing, not decays, and astrophysics teaches us exactly why.”
Yes, black holes emit radiation of exactly the type described by Stephen Hawking: a low-energy spectrum of photons and other particles arising from the physics of quantum field theory in curved spacetime. But, for much longer, we’ve known that black holes must also be absorbing energy over time, from matter, from starlight, and from the cosmic microwave background radiation.