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No Naked Black Holes
Posted by
kdawson
on Sun Oct 05, 2008 11:17 PM
from the also-no-hair dept.
from the also-no-hair dept.
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 ..."
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from the also-no-hair dept. (Score:5, Funny)
Oh jeez.
Does anyone else get sad? (Score:4, Insightful)
Does anyone else get sad at the thought that there are so many weird things in the universe you may not learn the answers to in your lifetime? What if everyone posting here never finds out the reason for the cosmic censor? Sort of depressing.
Re:Does anyone else get sad? (Score:5, Insightful)
Does anyone else get sad at the thought that there are so many weird things in the universe you may not learn the answers to in your lifetime?
I would submit that this is the lament of every intelligent being since the dawn of time (assuming there is a dawn of time).
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Re:Does anyone else get sad? (Score:5, Funny)
Having the massive intellect to comprehend the answers to all these questions does not make one less depressed.
Marvin.
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Re:Does anyone else get sad? (Score:4, Insightful)
For in much wisdom [is] much grief: and he that increaseth knowledge increaseth sorrow.
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Re:Does anyone else get sad? (Score:5, Insightful)
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Re:Does anyone else get sad? (Score:4, Insightful)
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Cosmic Censor (Score:5, Funny)
Penrose conjectured that there must be some physical principle â" a 'cosmic censor' â" that forbids singularity nakedness...
God, is that you?
Re:Cosmic Censor (Score:5, Funny)
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Re:Cosmic Censor (Score:4, Funny)
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Re:Cosmic Censor (Score:5, Funny)
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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
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Re:Cosmic Censor (Score:5, Funny)
Now stop touching yourself.
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Singularity nakedness on Slashdot (Score:5, Funny)
There is no singularity (Score:3, Insightful)
Re:There is no singularity (Score:4, Informative)
Photons have no mass but do have momentum.
The Lorentz transform causes a breakdown for E in E=mc^2/sqrt(1-v^2/c^2) where v=c. And when you have enough gravity to bend space such that it folds in on itself - light cannot escape, despite being massless but gaining momentum from the gravity well - you have a singularity.
One can't just say that equations break down, but physics do not. The equations are the language used to express the known physics.
So, there is a singularity, there needs to be, and it isn't magical - unless you mean magical in the sense of wonderful.
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Re: (Score:3, Funny)
That would cause some other hairy problems, spelling being the least of them.
Re: (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 the
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.
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Re:There is no singularity (Score:5, Informative)
A black hole isn't some mystical thing unrelated to the other cosmological objects. Black holes are just stars that have consumed most of their fuel through fusion over billions of years, then collapsed. But consumed doesn't mean the mass is all 'burned up' and gone, but converted from hydrogen and helium into heavier elements that are harder to participate in further fusion reactions, resulting in decreasing internal pressure from energy being released by the star. If the conditions are right, the compacting force of gravity from all the 'star stuff' that's left exceeds the declining expansive pressure provided by the fizzling nuclear reactions inside the star, and it ultimately collapses into an incredibly small size. If the size is less than the Schwarzschild radius, it will become a black hole.
But it's still just a lump of star stuff with mass like what the star had, but in a dramatically smaller package. It doesn't suddenly go on a cosmic rampage, marauding around and sucking up everything in sight. If something external has sufficient distance and velocity that it would have flown by or orbited the former star, then it will fly by or orbit the hole, as these parameters are solely determined by the masses of the star/hole and the external thing. If something would have fallen into the star, it will fall into the hole as well. Whether it falls into a black hole or a star, it's not coming back out.
Astronomers infer the properties of black holes from what they can observe about the objects that are influenced by them, and from what they observe about the progression of stars throughout their lifetimes. Just because we can't see into black holes doesn't mean they are totally mysterious.
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Re: (Score:3, Insightful)
Just as I suspected... (Score:5, Funny)
Right?
Re:Just as I suspected... (Score:5, Funny)
What if you reverse the polarity?
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Re: (Score:3, Funny)
Re:Just as I suspected... (Score:4, Funny)
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Re:Just as I suspected... (Score:5, Funny)
Have you tried logarithms? [xkcd.com]
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Non-Condradiction (Score:5, Interesting)
Re: (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.
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Re: (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.
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Re:Discrete; you know what this means? (Score:4, Insightful)
-1, Unfalsifiable
Dare I elaborate, if you wanted to make up a generic unfalsifiable claim on purpose that's probably what you would come up with.
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Re:Non-Condradiction (Score:5, Funny)
I believe that some solutions have space being discrete at the Planck length, rather than continuous, and this discreteness also removes singluarities.
I spent $82,000 on tube amplifiers and vintage vinyl, and now you tell me God's system is digital? Auuuugghh...
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Penrose is a kill-joy. (Score:5, Funny)
Which is why the DVDs "Physicists Gone Wild" were never really successful. Although the LHC did turn up as the hottest collider in Europe, so far still no naked singularities.
Re:Penrose is a kill-joy. (Score:5, Funny)
They're fixing that coolant leak. Calling them hot is just uncalled for.
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Shhh (Score:4, Funny)
You had me at naked...
Move Violent?... (Score:5, Funny)
...the most violent collision imaginable: two black holes colliding head-on at nearly light-speed.
What about 3 black holes colliding head-on at nearly light-speed?
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:Here come the goatse jokes (Score:5, Funny)
It's already asking a lot for nerdlings to not snicker at any reference to a "hole".
Adding in nakedness just goes beyond any reasonable expectation of restraint.
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Re:Penrose is smart (Score:4, Insightful)
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Re:Black hole collision (Score:5, Informative)
And the boom from a black hole is usually in the form of X-rays or gamma rays radiation and, in energetic terms, it's very loud.
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Re:Black hole collision (Score:5, Informative)
All the mass of a black hole is compacted into an extremely small region at the centre - possibly infinitely small, but at the very least as small as physics allows matter to get. This is the singularity.
When we speak of the size of a black hole, we're actually referring to the region around that central object from which nothing can escape. As you approach the black hole, the gravitational field gets stronger and stronger, and there's a point of no return at which the escape velocity reaches c, the speed of light. Nothing nearer the hole than this can ever escape. This we call the event horizon - because no events beyond the horizon can ever be observed from outside. The more massive the hole, the further out the event horizon: look up 'Schwarzschild radius' for the equation.
The result of this is that any singularities in the universe are expected to be hidden behind event horizons, and cannot be seen. It's occasionally suggested that a naked singularity might form - for instance, a black hole might be spinning so fast as to counteract the effect of gravity and allow the singularity to be viewed from outside. This could have extremely bizarre results for the universe as a whole, so most physicists expect there to be some kind of 'cosmic censorship' principle that ensures that this does not happen. What we're looking at here is one way in which that might happen.
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Re:Black hole collision (Score:5, Interesting)
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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?
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Re:Black hole collision (Score:5, Informative)
So pity not the photon, for even an eternity is less than a moment to it.
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Emmett Brown (Score:4, Funny)
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Re:Physicists... (Score:5, Funny)
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Re:No Naked Black Holes?! Giggidy! (Score:4, Informative)
The equations of relativity, which were used to run the simulation, say nothing about cosmic censorship. The C.S.H. wasn't formulated until 50-odd years after general relativity because of a problem - relativity actually readily admits (physically-implausible) solutions that do have naked singularities, hence the censorship. Apparently, something always conspires to hide them.
This simulation confirmed the hypothesis' prediction: Even in the most violent circumstances physically realizable, the singularity ended up behind an event horizon.
Frankly, it's time we admitted it... the only way we're going to find a naked singularity is to go for a joyride in the direction of the Great Attractor in a sycamore-seed-shaped ship.
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Re:Computer simulation, eh. (Score:5, Informative)
A few years ago, I might have agreed with you. After all, on a basic level you are correct, if we program what we know into a simulation, the simulation will be based on what we know!
Last semester I took a class in complex system, and it really opened my eyes about what computer simulations can do for us in providing unexpected behavior. Most of this is because we have a pretty good grasp on simple systems, and can take those simple systems and program them into a computer with rules of interaction to see how they will interact without human guidance.
Let me give you an example: Most everyone here at one point of time or another have programed "Life [wikipedia.org]" into a computer. We understand the rules, we understand the program itself, and we understand how everything is going to work, but until you actually run the program, you would never have expected the results! How could you have predicted the formations that would develop? The stable formations, the chaotic formations, the moving formations? Much less how these formations would interact when they collide?
I think in a way this is what was being simulated in the program mentioned above. We think we have a pretty good idea about the simple systems which make up a complex entity like a black hole. But how do these simple systems interact when they encroach upon another black hole? Assuming we really do understand these simple systems, and that they stay constant, I think this simulation gives us a reasonable expectation as to how black holes will react to a collision.
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Re:Computer simulation, eh. (Score:5, Insightful)
Anything based on a computer simulation is based on our arbitrarily incomplete knowledge. To base even the least significant conclusions upon it seems laughably irresponsible and unscientific.
We eagerly await your analytical solution to the n-body-problem. I mean, it's really simple stuff, right?
Until you're finished, we'll have to calculate all those spacecraft trajectories with computer simulations.
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