Einstein and all the great scientists from that era didn't miss black holes, they thought the idea of black holes were stupid and looked down on people doing that kind of research. Freeman Dyson talks about this in a few interviews - though he doesn't seem to understand why they thought that as he personally loved black hole research.
A singularity is, afterall, a mathematical effect that occurs everywhere in science when the mathematics used to describe the system in one region is no longer valid in another. Only in modern, government funded 'science' do we start to find people taking mathematical errors seriously. Also, to preempt any responses I might get, no, massive dark objects at the center of our galaxy are not even close to being evidence that space-time singularities are real.
Aren't you conflating black holes with singularities, here?
Questions about singularities, I would assume, are inherently non-scientific in the sense that it would be impossible to ever come up with testable predictions about their behaviour. However, black holes, as 'a region of spacetime where gravity is so strong that nothing — no particles or even electromagnetic radiation such as light — can escape from it' (definition ripped from Wikipedia), seem like a testable concept with some evidence for their existence.
Fuzzballs were first proposed as a consequence of superstring theory in 2002, so it would be quite a feat for a scifi author to have come up with them in 1977.
Not the same thing as a black hole. A black hole is a region of spacetime that cannot send light signals to infinity, i.e., bounded by an event horizon. In the simplest such models, there is a singularity inside the event horizon; but that does not mean every possible model with an event horizon must contain a singularity.
Btw, the problem Einstein and others of his time had was with the event horizon, not the singularity; the singularity did not become a significant object of study until a decade or two after Einstein died.
I'm guessing from these responses that 'singularity' has turned into kind of pop-culture term expressing the center of a black hole.
A singularity is just where physical quantities go to infinity. There are many singularities at the event horizon. For example, as you fall into a black hole and approach the event horizon the time of an observer a distance away begins to speed up and approaches infinity - the universe comes to an end before you actually reach the event horizon. Many unphysical things like that happen. These are all singularities.
Importantly also, the energy density of space-time approaches the plank energy and this is a region where general relativity and quantum field theory do not agree with each other. So we know the equations are non-sense in this region for sure.
> I'm guessing from these responses that 'singularity' has turned into kind of pop-culture term expressing the center of a black hole.
It's not a pop culture term at all. It's a precisely defined technical term in GR. Everything I said about it is taken from that precise technical definition.
> A singularity is just where physical quantities go to infinity.
Correct. (Although this itself is something of a pop science version of the actual technical definition. But it will do for this discussion.)
> There are many singularities at the event horizon.
Wrong. All physical quantities are finite at the event horizon. Your counterexamples are based on misconceptions which have been well understood and corrected in the GR literature for decades.
> as you fall into a black hole and approach the event horizon the time of an observer a distance away begins to speed up and approaches infinity
Wrong. If you are free-falling into a black hole, light from the rest of the universe is redshifted, not blueshifted.
If you are hovering at a constant altitude above a black hole's horizon, light from the rest of the universe is blueshifted; but the blueshift is finite for any altitude above the horizon. It is impossible to hover at the horizon.
> the universe comes to an end before you actually reach the event horizon.
Wrong.
> Many unphysical things like that happen.
Wrong.
> the energy density of space-time approaches the plank energy
Wrong. The black hole is a vacuum solution: the stress-energy tensor is zero everywhere.
> this is a region where general relativity and quantum field theory do not agree with each other. So we know the equations are non-sense in this region for sure.
Wrong. The area at which GR and QM create compatibility problems is within a Planck time of the singularity, not the horizon.
As I said above, all of these misconceptions have been known of and corrected in the GR literature for decades.
I didn't believe you so I looked this all up and indeed everything you said is correct. My GR professor was famously one of the worst academics at the department and he never taught us any of that. His specialty was GR too.
Anyway, your response was needlessly hyperbolic. The only two misconceptions you are correcting here is that tidal forces can be quite weak at the event horizon and the universe does not come to an before passing through it.
> My GR professor was famously one of the worst academics at the department and he never taught us any of that. His specialty was GR too.
This is disappointing, but unfortunately I don't find it surprising. I have learned GR by self study over many years, starting with borrowing my office mate's copy of Misner, Thorne & Wheeler when I was in graduate school; I never actually took a course in it. But the reports I had from people who did were that the professors did not do a good job of explaining things. Unfortunately being good at research and being good at teaching are two very different things and not many people have both.
> The only two misconceptions you are correcting here is that tidal forces can be quite weak at the event horizon and the universe does not come to an before passing through it.
I did correct those two misconceptions, but those weren't the only ones in your post.
There's no particular reason to believe the singularity in the math describing black holes has physical existence. Lots of equations have singularities and usually it just means that you're using them outside the domain in which they're defined.
Maybe some heretofore unknown force kicks in and keeps the material inside the black hole from forming a singularity. Maybe they're actually fuzzballs:
You don't really have to have a fully worked-out explanation of why the black hole singularities aren't physical- nobody can see inside the black hole, so all we can say is that the existence of black holes is consistent with there being a physical singularity in the middle. But really anything could be happening in there, we just don't know. The singularity the GR predicts is arguably evidence against GR holding at the center of the black hole; there's very probably something else going on.
This makes no sense. When you apply the mathematics of fluid dynamics to the problem of water leaking through a dam wall, you get singularities.
It makes no sense to say "you either believe the amount of water in a dam wall becomes infinite and the universe collapses in on itself inside a dam, or you have a better theory, what is that theory?" (you would become a famous mathematician if you had that theory by the way).
A singularity is, afterall, a mathematical effect that occurs everywhere in science when the mathematics used to describe the system in one region is no longer valid in another. Only in modern, government funded 'science' do we start to find people taking mathematical errors seriously. Also, to preempt any responses I might get, no, massive dark objects at the center of our galaxy are not even close to being evidence that space-time singularities are real.