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No Naked Black Holes
Science News reports on a paper to be published in Physical Review Letters in which an international team of researchers describes their computer simulation of the most violent collision imaginable: two black holes colliding head-on at nearly light-speed. Even in this extreme scenario, Roger Penrose's weak cosmic censorship hypothesis seems to hold — the resulting black hole (after the gravitational waves have died down) retains its event horizon. "Mathematically, 'naked' singularities, or those without event horizons, can exist, but physicists wouldn't know what to make of them. All known mechanisms for the formation of singularities also create an event horizon, and Penrose conjectured that there must be some physical principle — a 'cosmic censor' — that forbids singularity nakedness ..."
Quantum physics was baffling to me (still is, actually), but I eventually came to see it as a way that nature avoided some inherent paradoxes and contradictions that were present when you took classic physics down to the level of fundamental particles. I have no doubt that, on a larger scale, the same principle applies: Somehow, someway, the laws of physics will always resolve with no singularities, no contradictions, no divide-by-zero-error, no infinities. If our formulas seem to indicate that one will be found, I suspect our understanding is incomplete.
This means that not only are we living in a simulation, but we're being run on a digital computer.
If I'm recalling correctly Hawking addressed that issue in Brief(Briefer?) History of Time. He explained that for small black holes the difference in how strongly gravity is pulling one end of you(feet) compared to the other end(head) would tear you apart before you could reach the event horizon. Large black holes (on the order of millions of stellar masses, like the ones at the center of galaxies) would be a much more gentle ride intially. In fact he said, you could pass right through the event horizon and not notice anything particularly weird happening. You wouldn't even notice. Nevertheless as you get closer to the singularity at the center you'd still get ripped apart.
But if time is moving infinitely slow, then how does matter ever get to the center? Shouldn't all the matter be concentrated at the event horizon?
But black holes exist within the universe. If time inside a black hole is stopped relative to the rest of the universe, then shouldn't a black hole take infinitely long to form?
As a corollary, shouldn't you be able to look behind you and watch the end of the universe?
I'll take the second point first. And believe me I'm no expert, I mearly take an interest in Astronomy and I've read quite a lot on the subject.
If you 'look' behind you as you enter a black hole you see the light that was entering immediately behind you so you see the static universe as you normally would. But as with a lot of complicated maths and physics, human language and common experience can't really serve as a metaphor for what is going on. It's an unfortunate answer to a great many questions.
Your first question I'm not too sure about, it is a very insightful question. After a black hole is formed then yeah, time slows down to a crawl *if* there was any way to look in (past the event horizon). But I don't really know how to explain the fact that as it creates a sigularity time should slow down. I think an important concept to understand is that there is no universal clock. Imagine everyone in different gravity wells running along different percieved time-scales and you be along the right tracks. Really I'm in over my head though!
Try here for an excellent podcast on black holes and the notes page has a ton of links. This is were I get most of my Astronomy info. The podcast really will stretch your immagination!
http://www.astronomycast.com/black-holes/episode-18-black-holes-big-and-small/
Cosmic pun!
The name is derived from the Latin sacer, "sacred", a translation of the Greek hieron (osteon), meaning sacred or strong bone.[1] This is supposedly because the sacrum was the part of an animal offered in sacrifice. In Slavic languages and in German this bone is called the "cross bone".[2]
- http://en.wikipedia.org/wiki/Sacrum
So keep on gyrating those sacred hips. :p
All rites reversed 2010
Perhaps someone could educate me here but how accurate is this because surely we've never done any study into the effects of gravity at the speed of light. Doesn't gravity act differently at this speed?