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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 ..."
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.
'a';DROP TABLE users; SELECT * FROM DATA WHERE name LIKE '%'... if you're reading this, it didn't work.
Penrose conjectured that there must be some physical principle â" a 'cosmic censor' â" that forbids singularity nakedness...
God, is that you?
...the maximal Cauchy development of generic compact or asymptotically flat initial data is locally inextendible as a regular Lorentzian manifold.
Right?
Lemmings are silly; dinosaurs are extinct.
In other words, yo momma's so fat, her Schwarzchild radius is visible to the naked eye?
They're fixing that coolant leak. Calling them hot is just uncalled for.
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).
...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?
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.
Real Daleks don't climb stairs - they level the building.
Having the massive intellect to comprehend the answers to all these questions does not make one less depressed.
Marvin.
Remarkably well said.
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.
Against stupidity, the Gods themselves contend in vain. --Friederich Schiller