Signatures of gravitational atoms from black hole mergers

I think they are more drawing an analogy between the atom one or more black holes with a cloud of particles around them. Black holes are quantum mechanical and so the resulting system could behave much like an atom, including having things that look like energy levels. The universe rhymes.

> I still do understand what a "gravitational atom" might be.

It's a vague gesture in the direction of a speculative theory of quantum gravity. It's not anything we have any actual evidence for.

> I thought it is pretty well accepted there isn't a "gravaton" like there are photons.

Different branch of physics that we can't quite mesh with GR yet. A graviton is the quantized "piece" of gravity, like phonon is for sound/mechanical waves, or photons for EM. It exists as much as a photon or any other "messenger particles" exists, in that it's a useful mathematical model. It's not something we have isolated/observed with equipment though.

In an atom, the electrons orbiting the nucleus are only allowed to be at discrete energy levels (the energy levels are "quantized"). In a classical model of an orbit, the energy level of a spaceship orbiting a planet can be thought of as the speed it has that allows it to orbit at a certain altitude, assuming no friction or other effects. Velocity is energy in that case (E=m*v^2 in classical mechanics). Unlike electrons in an atom, the spaceship can be in any one of a continuous range of energy levels (up to escape velocity).

The proposal in the article is (I think) that bosons orbit certain black holes in quantized energy states, like electrons would orbit an atomic nucleus.

Speaking of PBS SpaceTime, pretty much every one of their videos starts fine but always lose me around the half point. Anyone feel the same?

As far as I know the existence of the graviton is 100% up in the air, not well accepted either way.

But yeah, particles in energy levels gravitationally bound to a black hole in a similar way electrons are electrically bound to a nucleus.

Regardless of the gravity canceling out in this region (which is more complicated and probably will not happen). The current LIGO and Virgo wouldn't have enough spatial resolution to pinpoint tiny regions between black holes.

To explain what will happen is that gravitational field in region you are describing would have a steep spacetime curvature and a point where it will cancel gravitational forces would be more of a saddle (lagrange point classically) point rather than zero gravity region.

Now you also have quantum fluctuations that now with this strong gravitational field you will have virtual particle - anti particle paris pop in and out of vaccum. This is not going to be only in thia region but all around. Also merging process will enhance this phenomenon but deciding where actually this middle point will be difficult.

Now it would be impossible at least for our current observational tools to have resolution for the scale we are talking about. Event horizon telescope for example is designed to observe areas around singularities on much larger scales that what you are interested in here.

But the interesting part would be If matter and antimatter pairs were produced between merging black holes, they would likely be short-lived. In this intense gravitational environment, any particles created would be rapidly torn apart or accelerated towards one of the black holes. The annihilation of such pairs might emit gamma rays, but this signal would be extraordinarily faint compared to the other high-energy processes occurring during a black hole merge.

So the answer is probably No, at least with our current technology.

> between two singularities merging

Two black holes merging does not mean two singularities merging. The singularity (singular, not plural) is a moment of time that is to the future of all other moments inside the hole. If two black holes merge, there is just one singularity inside the merged hole.

Remember that GR is a model of spacetime, not space. In spacetime, a single black hole looks, heuristically, like a cylinder, and the singularity inside is at the future end of the cylinder. Two black holes merging look, heuristically, like a pair of trousers, and the (one) singularity inside the merged hole is at the future end of the trousers (the "waist").

One odd thing that never occurred to me until now is that two black holes that pass each other at near light speed, if they intersect by even a nanometer, will be guaranteed to merge. That nanometer has to fall into both singularities due to the properties of black holes, so transitively they have to merge. Kind of weird. I'm guessing it would create a bunch of angular momentum and throw out almost all their masses as gravitational waves. Will be a fun experiment for someone in a few hundred years.

What you're asking for is a naked singularity. Nothing can produce that, not even another black hole.

Each black hole has tiny spot with zero gravitation in the centre.

yes, just heard about it on Physics Frontiers. Monsalve & Kaiser are talking about primordial black holes, and are offering a theory that if they were imbalanced in color charge, they could be surrounded by a particle cloud, in a big quantum state.

https://pca.st/episode/f0db6ab1-18ff-4201-a6b2-a30b780a266a

Let's not forget that the radius of the observable universe is ~= the Schwarzschild radius i.e. we're all almost certainly inside a black hole ;)

https://en.wikipedia.org/wiki/Black_hole_cosmology

> Then there’s spooky shit like: > https://en.m.wikipedia.org/wiki/Black_hole_electron

From the article:

> However, Carter's calculations also show that a would-be black hole with these parameters would be "super-extremal". Thus, unlike a true black hole, this object would display a naked singularity, meaning a singularity in spacetime not hidden behind an event horizon. It would also give rise to closed timelike curves.

I wonder if there's a fun sci-fi story in the discovery that all electrons are in fact naked singularities.

If we did have a tennis-ball-sized black hole out beyond Neptune, it would be far beyond our capabilities to locate and track - we can barely track debris that small in low Earth orbit, and black holes aren't even courteous enough to provide a radar return. We would not be able to send probes near it any time soon.

> The universe could be full of black holes in the asteroid mass range the size of hydrogen atoms.

? Not if there's Hawking radiations.

Why wouldn't the primordial black holes condense into bigger ones like the matter that makes up planets and stars did?

Black holes can't be dark matter.

Dark matter is a WIMP

The universe was built on a scaffold of dark matter like an old spiderweb that slowly collects dust.

> But gravity is the curvature of space caused by mass, it is not described as a form of mass.

Gravitational waves carry momentum and energy (and therefore mass), just like electromagnetic waves. Theoretically, you can extract that energy from gravitational waves, by using oscillating masses tuned to the wave's frequency.

> We were told that nothing can escape a black hole.

Stephen Hawking told otherwise, actually: https://en.wikipedia.org/wiki/Hawking_radiation

In 1974, and that's now 50 years ago.

> How do you understand this process of matter escaping a black hole?

No matter escapes. Gravitational waves are not matter. They are spacetime curvature. Nor do they "escape" the black hole; they are emitted from outside the horizon. The reason the mass of the merged hole can be smaller than the combined masses of the original holes, with the difference being emitted as gravitational waves, is that black holes are not made of matter, they are made of spacetime curvature, and when they merge, some of the spacetime curvature doesn't get included in the merged hole. That's just how spacetime curvature works.