Still, I’m looking forward for your e-mail…

Dude, I suggest that you re-install your sense of humour software because, obviously, it is not responding.

@DrFlimmer (#30),

I’ve found some interesting papers on the subject of co-/counter-rotating binary black holes; I’ll need to study them for a bit, so I’ll e-mail my response to you in due course.

From what I gathered later, they do have characteristics of a spinning body, but that’s it. They don’t spin the same way Sun spins, but they affect whatever it is they affect in a similar (if not exact) way. My original question doesn’t seem to be applicable.

..the only problem is that Reissner-Nordstrøm Black Holes are not spinning. You need Kerr blackholes for that.

Mathematically speaking you are right. This is a serious problem.

@Messier Tidy Upper:

If you consider the other three dimensions x,y,z – they have vanished. What is left is time.

See Reissner-Nordstrøm Black Holes. The outer event horizon is a boundary where time and space flip. This means that the singularity is no longer a point in space, but one in time.

“Do humans exist who really understand this,,,”

As I recall, it was Richard Feynman who said “If you think you understand quantum mechanics,,,you don’t.”

What we understand is the math. Being able to conceptualize these arcane subjects would likely require a much bigger brain,,,and I expect any woman who had to birth such a mutant would object most vociferously.

30. DrFlimmer

“I think that there is also an upper limit on the spin for a black hole”

¥es. It is subject to the same limitations as apply to any mass/energy approaching light speed(in relativity). Yah can’t go as fast as light(unless there are such things as tachyons)(and they can’t go as SLOW as light).

Gary 7

The fact that the initial state of the building’s contents is unknown is the point of the silly math .

It is somewhat analagous to not knowing the interior conditions of a black hole .

Hm. Still. They can only become tidally locked, if their spin vectors are at least a bit lined up. Now, take the situation that the vectors are exactly opposite, that is to say, one of the black holes rotates the other way around compared to the other one. I don’t think, they can become locked in such a situation.
If we assume, now, that their respective spins would be the same in magnitude, they should cancel. This means, the spin of the resulting hole should come from the angular momentum of the orbital motion. And it should also be the prime contribution, even if the spins do not cancel.

To answer my question:
Yeah, this should to a hellish spin.

Btw: I’m not quite sure, but I think that there is also an upper limit on the spin for a black hole. IIRC, a too high spin would lead to a naked singularity, which is forbidden. But don’t ask me for details. I don’t want to look them up, now.

Not to forget:

2 + 2 = 5
for very large values of 2

@14. Practice asks : “I’m confused. Is black hole a three-dimensional body?”

No, actually, a black hole is (at least) a *four* dimensional one existing in the usual three spacial dimensions plus a fourth dimension – time!

@24. nomuse & #22. IVAN3MAN_AT_LARGE :

Reminds me of all the non-two ways of summing one plus one for instances :

1 + 1 = 0 when you add a particle of anti-matter to one one particle of matter.

1 + 1 = 11 when you add a written numeral 1 right besides another written numeral 1.

1 + 1 = X (lots!!!) when you add a male to a female rabbit and wait a while!

Hence the joke about a math prof waiting for a classroom to empty. He’s been told there are still six people inside. He watches as seven leave. And stands there waiting for one person to go IN so the number of people inside will be zero.

Do there exist humans who understand all this with some level of certainty?

I too can make theories, given 5-10 years of continuous company of mathematicians, but juggling equations is trivial compared to being able to perceive or comprehend, even somewhat, the things we discuss here.

We were not built by nature to comprehend such scales, but we manage well by fitting models and linking them together in chains of perceptions. For example, the first time I understood integration, I was overjoyed. But then I found it was the simply the rate filling of water into a glass from a tap.

To comprehend superfast spinning denseness, maybe we should play with many large and small tops or lead wheels first?

How do I imagine all this?
I’ve watched a huge load of science fiction series and movies, but this is much more than those visual-soundbites (so to say).

Can anyone hold 5-10 constraints consistently in your awesome mental imagery? I can’t hold 2 properly.

Any secret tricks like meditation?

But the assertion that black holes at the centers of distant galaxies in the past had less spin than present day galaxies, I believe, will turn out to be an invalid conclusion based upon future observations and evaluations.

your math is wrong. The only way you can reach the conclusion that the building is now empty is that it was empty to start. I.e. your initial assumption of 0 (in the 0+2) step. But in step 2 you see 3 come out, so you know your initial assumption is wrong. Continuing on using incorrect assumptions does not make your result interesting, it makes it incorrect.

…, just because it’s ALLOWED by the math doesn’t mean something we know nothing about may prevent such from actually occurring.

For example: two people enter a building; then three people leave the same building; then one person enters that building; therefore, mathematically, the building is now empty (0 + 2 = 2; 2 – 3 = -1;
-1 + 1 = 0).

Naw, that’s not odd. Now, the idea that the universe as a whole has a net angular momentum – that I find odd.

Wait… Really? Does the universe as a whole have a non-zero net angular momentum?

*puts on physics dunce cap*

If so, that’s cool but, based on my very limited understanding of physics *points to cap* utterly surprising to me. I would have expected the net angular momentum to be zero.

Given all the matter in the accretion disk has angular momentum of its own, could it be the case that eating that matter is also adding to the angular momentum of the black hole? Or would that be negligible on the scales involved?

Also: If you have two black holes orbiting each other contra-spin, would there be a tidal effect that would slow one or the other down or perhaps speed them up? Or again, would that be negligible on the scales involved?

Interesting to think about.

“and in order to conserve angular momentum when something gets smaller (all other conditions being kept the same) it has to spin faster, why don’t black holes wind up spinning infinitely fast?”

What goes on inside a black hole is unknown(and may be, theoretically,UNknowable) to us. What we refer to as a black hole is the event horizon, the boundary beyond which no light, or any other energy, can escape to carry information to us. Mathematically, all the matter inside the black hole should collapse toward infinite density, thereby forming a singularity however,,,,just because it’s ALLOWED by the math doesn’t mean something we know nothing about may prevent such from actually occurring. As far as we KNOW, inside the event horizon there could exist an entire universe.

,,,and there have been a few stories written about that.

Gary 7

Re: what is spinning?

According to a very brief scan of the Wiki page on Black Holes, it appears that it’s the singularity that spinning. Weird for something with an infinite property (gravity), and what I thought was described as a point (zero width). Now my brain hurts…

Surly

What is extraordinary about the conservation of momentum in this case?