**Ask a monkey a physics question thread**

[MadMojoMonkey]

No idea, I guess it comes down to the quantum nature of energy. QM tells us that energy is quantised, that is comes in integer values and not in between.

Only in bound systems, but the BH is a bound system.

I'm just pointing out that energy is not always quantized. It's the boundary conditions that create quantization of energy and other things.

A particle not confined in any way (meaning a bit of hand waving about it's existence "in" the universe) can have any energy at all. A photon can have any wavelength, and therefore any energy.

Perhaps a black hole with one base unit of energy is unable to evaporate further. What mechanism causes Hawking radiation? I'm not sure if this was a simplification or a correct interpretation, but my assumption was that virtual particles forming at the event horizon emit a particle in one direction and an antiparticle in the other, resulting in a photon escaping and therefore slow decay of mass. In this way, the black hole can only lose half of its mass.

You had me until "half of its mass."
An anti-particle falls in to the black hole, while its non-anti/normal particle partner escaped. It doesn't matter which is anti. The BH ejected mass/energy, which is conserved. If nothing counters this process, the BH evaporates... smaller BH's evaporate faster, so it's a runaway event, albeit with a very slow run-up, even in universal time scales.

If energy is quantised, then we have a problem when the black hole is one unit in mass.

The quantization of mass/energy is a thing, but it's not messing with us, here. At least, not in any way that I understand.

Particles decay into smaller particles all the time. Elementary particles decay into photons. The mass of particles may be quantized, but the energy of the photons they emit is not quantized. They can emit multiple photons at once, so long as all the conservation laws are followed.

I used the term "Planck mass" because I (probably naively) assumed that was one base unit of energy. But maybe it isn't.

Mass and energy are different things. Apples and oranges, if you will.

FYI, 1 unit of Planck Energy is 2 GJ -> 2 billion Joules. It's certainly not an upper or lower limit on anything.

The vid sums up by saying that if this hypothesis is true, it's a problem, because such black holes would be undetectable. We may have a situation arise where the most simple explanation for dark matter is the most difficult to prove, if not impossible. We might never be able to detect dark matter.

That sounds like no change from the current situation. There's something causing a gravitation-like force out there, and we don't see anything that would be the culprit.

We'll get there. The progress of science comes in bursts.

Not sure. Gravitational lensing was used to rule out moon-mass type black holes as dark matter candidates though, so it's not something they overlooked in their hypothesis.

Yeah, I'm not claiming to understand all the nuance, here.

Dark matter doesn't directly influence light, but its gravity does. Dark matter still causes gravitational lensing.

Yeah. I don't consider that light interacting with dark matter, personally. I consider that dark matter interacting with spacetime and photons propagating through that spacetime interact with it. Maybe that's not the best distinction, but its working for me pretty good so far.

My gut says that if a black hole can't completely evaporate, then there will be an enormous amount of these undetectable relics in the universe. It seems like a great candidate for dark matter to me.

IDK. There are plenty of not-yet-explained things out there in the universe. I was hearing about black holes that are simply too big to have formed in the 13.7 billion years the universe has been here. IDK how they determine that, but it just shows that there is a lot of stuff out there that we don't quite understand.