If I’m standing comfortably outside the hole and watching you fall in, I will never observe you to quite cross the horizon. This will be cold comfort for you, though, because in your reference frame, you’ll cross the horizon and reach the singularity in very short order.
Is there any proof a black hole is a single point? It seems absurd that other extremely dense bodies like a neutron star have diameter of about ~24 km. If we keep adding atoms, you’re telling me that at some point a single atom will cause all matter in the body to shrink to an infinitesimally small point. Just because we crossed the gravitational boundary for light escaping, also means that we broke some law governing the way atoms organize themselves in a very dense body and it shrinks into nothing? It seems more likely that we just have a smaller, extremely dense, and now dark, body.
I think the notion comes from the idea that once on the way to forming a black hole there remains nothing else to stop the collapse. Along the way there are a lot of things that resist collapse to this state. Indeed when you get to a quark star the entire star may be regarded as a single, gigantic, hadron (e.g. a proton or neutron). At that point it is difficult to imagine anything more dense.
Once gravity is strong enough to overcome the quark degeneracy pressure nothing is left. Collapse is complete. In order to suppose a size for the singularity you need to suppose some other mechanism to keep it that size.
As noted it is speculated the singularity may not be a point but may be a Planck sized thing…which is pretty darn small.
My apologies for possibly derailing the thread. I know dracoi and Whack-a-Mole were just trying to help, but sometimes I am a tad slow.
As I noted just above consider a Quark Star. It is essentially a single particle writ very large. There are no more subdivisions. How can you get more dense than that?
When you have enough force to squish it more then there is nothing left to oppose the squishing so it will continue down to some minimum size possible…likely either a point or a Planck length singularity.
IIRC Chronos once corrected me that the Planck size is not the smallest thing possible. It is just the smallest distance we can theoretically measure based on restraints imposed by the Heisenberg Uncertainty Principle, the speed of light and Planck’s Constant. Beyond this humans cannot possibly measure any smaller (as it happens we cannot even get close to that yet but it is an absolute limit).
If so then perhaps there are smaller sizes, just not sizes we could ever measure. Whether there really are smaller things I have no idea.
Really, any definite statement about the Planck scale is premature. All the Planck units are is a back-of-the-envelope guess as to when quantum gravitational effects would start being relevant, and what that means depends on how quantum gravity works, which we don’t know yet. Besides which, even if there is some true relevant Planck scale, nobody would be at all surprised if its actual value were off of our predictions by a factor of 2, or pi, or 137, or whatever, and there are even models which put the fundamental scale at widely different models (perhaps even as large as a micron or so).
There are some models in which there is a smallest possible scale for space, and if you’re going to guess what that scale is, the Planck length is as good a guess as any. But those models may or may not be true, and the Planck length may or may not be the right guess for the fundamental length. We just don’t know.
There is no proof that a black hole is a single point. If the radius was very large, though, we’d expect to be able to tell that.
I think the problem a lot of people have is that they’re so used to think of the Bohr model of the atom - little spheres orbiting clusters of other little spheres. We envision these little spheres to be billiard balls or something else that does have to occupy some minimum volume.
I’m not convinced that it does. I think quantum mechanics, the wave/particle duality, and Einstein’s energy-mass equivalency are really pointing to an altogether different model in which particles are just localized field phenomena rather than “things” in the way we’re used to thinking of them.
Agreed. It is ridiculously dense. And it cannot get any more dense. But just because it doesn’t have any subdivisions, that doesn’t mean it can’t have a SIZE, doesn’t it?
I suspect that your use of the word “squish” may be confusing me and the other novices here. I suspect that what you mean is that it ceases to be matter, and all the energy overlaps so that it takes up no space. Or something like that?
So far as our current theories can tell us, a black hole is composed entirely of vacuum. There is no point in space that has any nonzero density. Any volume of space which does not include the singularity contains no mass, and any volume of space which does include the singularity contains the entire mass of the hole (but the singularity itself isn’t part of the space).
A singularity wouldn’t be one-dimensional. One-dimensional objects have length, such as a line. Singularities are points which are dimensionless.