No Naked Black Holes 317
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 ..."
Firing line. (Score:1, Interesting)
""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 â" a 'cosmic censor' â" that forbids singularity nakedness...""
Basically because there's two extreme conditions. Out here and in there. One can't help but have a boundary.
Non-Condradiction (Score:5, Interesting)
Re:Non-Condradiction (Score:3, Interesting)
Re:Non-Condradiction (Score:5, Interesting)
I believe that some solutions have space being discrete at the Planck length, rather than continuous, and this discreteness also removes singluarities.
Re:There is no singularity (Score:3, Interesting)
He's right tough.
Just because we can't look inside, doesn't mean that everything breaks down inside.
People often see a black hole as something magical, and think, the Schwarzschild radius is some magical wall.
It's just the distance, at which gravitation is stronger than everything else, so we can't get useful information from the inside. Although maybe with entangled particle-pairs we could get information out!)
About the inside we know nothing. It's not the physics that break down. It's the formulas and theories, because they result in infinite numbers, which is a typical symptom of formulas being applied outside their useful range.
So we have to fix our theories, but we don't know how, because we can't look inside.
And if nobody especially lucky comes around and finds a method to get that information anyway, it's going to stay that way for a loong time.
And: Yeah, that's kinda sad.
Re:Non-Condradiction (Score:3, Interesting)
Discrete; you know what this means? (Score:4, Interesting)
This means that not only are we living in a simulation [simulation-argument.com], but we're being run on a digital computer.
Re:There is no singularity (Score:5, Interesting)
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.
Re:Black hole collision (Score:5, Interesting)
Re:Penrose is smart (Score:3, Interesting)
That's him. Unfortunately, his quantum consciousness idea doesn't give an explanation of consciousness, it just gives a means for Descartes "ghost in the machine" to interact with the physical -- in other words it just moves the problem. On the other hand, I've not heard any other coherent explanation of consciousness either. And he's made more contributions to mathematics than any other philosophers of the mind that I can think of. So tempted to do my bathrooom in Penrose tiles!
Re:Black hole collision (Score:4, Interesting)
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?
Re:Does anyone else get sad? (Score:2, Interesting)
Re:Black hole collision (Score:3, Interesting)
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/ [astronomycast.com]
Re:Cosmic Censor (Score:5, Interesting)
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 [wikipedia.org]
So keep on gyrating those sacred hips. :p
Re:There is no singularity (Score:2, Interesting)
But it's still just a lump of star stuff with mass like what the star had
Is there any theoretical limit to the formation of new elements? Might there exist, in large black holes, ones with atomic numbers in the thousands? Are we sure that they will continue to behave according to the laws of physics as we know them?
These are not rhetorical questions -- I'm genuinely interested.
Gravity at the speed of light (Score:4, Interesting)
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?
Re:There is no singularity (Score:3, Interesting)
Time is only moving slowly as viewed by an outside observer. An observer would see you take an infinite amount of time to cross the event horizon. But from your point of view, time continues on as normal.
As you cross the event horizon you wouldn't notice anything unusual, you would still see the outside universe behind you and the event horizon would still appear in front of you. In fact, from your own point of view, you would never reach the event horizon, it always appears in front of you at the same distance, until you hit the singularity.
Re:Move Violent?... (Score:2, Interesting)
How about this? Imagine the two objects moving towards the third one from opposite directions.
Re:There is no singularity (Score:3, Interesting)
No, GP is right. Your time would pass normal for you, but the time of everything outside the black hole would pass faster and faster, meaning you'd get more and more radiation and faster and faster star movement, until the sky is completely white. But I guess you'd be dead by then.
Re:Penrose is smart (Score:3, Interesting)
Im not sure but what moving the problem is a significant advance, maybe one Penrose didn't intend. One problem strict philosophical materialism has in practice is it tends to reject all 'supernatural' phenomina, but it does so dishonestly. That is, most believers in it claim to simply be naturalists as a method, because it's pragmatically difficult, perhaps impossible, to apply science to something that can manipulate the very laws of nature.
As I understand it, the more common assumption is that there is nothing that can manipulate the laws of nature from outside, because if there were it would be subject to its own rules and so part of (an expanded understanding of) nature. That's a metaphysical assumption, of course, but one that allows them to retain their naturalism.
Quantum Mechanical explanations aren't technically supernatural, but they tend to certain properties that supernatural explanations also have (Multiple interpretations may have equal validity
Careful! That's why they're called "interpretations", not "theories". Multiple interpretations have equal validity (though not necessarily equal utility) wherever they occur. It just happens that quantum mechanics is a field particularly remote from experience so we have a particular need for interpretations -- metaphors, if you like -- to get an understanding of what's going on.
some odd things are explicitly allowed because they are happening 'outside' of our scale space-time, and the real root causes of phenomena can't possibly be determinate in a strict Newtonian sense.)
Unfortunately, I don't think that helps with consciousness. Newtonian mechanics meant that all my actions are completely predetermined by mechanics. Quantum mechanics means to some extent my actions are randomly determined. That still doesn't seem to leave any room for volition, for choice.
While the quantum realm is often conceptualized as underlying ours, phrases such as 'collapse of the state vector' imply a realm superior to mundane existence, and just abut all QM assumes this realm is timeless/eternal/non-enthropic. (Sounds kind of like heaven, doesn't it?)
Again, as far as I am aware, QM doesn't assume any such thing; it uses it as a metaphor.
So, opening up the discourse to accept possible explanations with such properties proves that science can deal with some things it once thought it couldn't address at all (the contrary argument being that QM itself isn't scientific.)
A third possibility being that Science is dealing with what it's always dealt with, QM is perfectly scientific, and you're confused between the scientific status of theories and interpretations.