Man-Made Black Holes Looming? 300
camusflage writes: "The New York Times has a story that some physicists think it might be possible to make black holes at the under construction Large Hadron Collider at CERN, slated to come online in 2006. Trying to allay concerns about a man-made black hole blipping us out of existence, they say "The same calculations ... predict that around 100 such black holes a year are `organically' and apparently safely produced in the earth's atmosphere in cosmic ray collisions." As long as we can keep critters from building nests in the singularity, we should be okay."
Re:We should make Afganistan a black hole. (Score:-1, Informative)
You are one sick guy. Lemme tell you something. I too live in a place where Muslims are in a distinct minority *and* have caused enough law-and-order problems. (Hint, there are only a few places in the world which have a large Muslim population but where they are still in a minority)
But to blame all Muslims for the deeds of a bigoted few, or to tar all Muslims with the same 'fundamentalist' brush, is WRONG. How would you feel if I told you that all Aussies are racist? That's tarring all Aussies with the same brush, isn't it? (And don't you dare deny that there are *no* racist Aussies... but that's another topic altogether)
Yes, percentage wise, there probably are *more* Muslim fundamentalists than Christian or Jewish fundamentalists. But to suggest the slaughter of muslims as you do, is no better than what the National Socialist Party did in Germany.
Get real. Killing people is not the solution. Violence only breeds a vicious cycle of more violence.
</rant>
Gravity is a really weak force... (Score:5, Informative)
As everyone knows, gravity is the weakest of all the fundamental forces by a very very long way, something like 40 orders of magnitude weaker than the weakest of the nuclear forces. I remember reading an article here long ago (can't find it and put a link to it because Slashdot search is down...grr) that talked about some speculation that gravity is so weak because the universe has more dimensions than the four that we see (this is also a prediction of superstring theory), and while the other three forces are only capable of propagating there, gravity is able to propagate through these extra dimensions, making it seem weaker. These dimensions are supposed to be curled up small so we don't normally notice them, so one of the implications of this theory is that the value of the universal gravitational "constant" should shoot up dramatically when you try to measure it at smaller scales; the smallest scale at which gravity has been measured so far is on the order of centimeters only. Another implication is that it should be possible to create low mass black holes with less energy than the weakness of gravity as we know it predicts. So if these scientists are successful in making such small black holes, it could go a long way to validating this theory.
Re:Gravity is a really weak force... (Score:3, Informative)
I seem to remember having read somewhere that the whole point of the multiple dimensions in string theory was that they were incredibly tiny and curled up on themselves. And they were supposed to be less than the planck length in total size, if I remember right. I understand how the dimensions could dissipate the force of gravity, but how does the gravitational force increase at small distances? Wouldn't the multiple dimensions of the two particles somehow have to collide/interact? And wouldn't that only occur if the two particles were closer than the planck length, which is closer than they could possibly get anyway? I know I am missing something here, and I am interested to hear exactly what it is.
Re:Gravity is a really weak force... (Score:5, Informative)
The original theory expected curled dimensions on the order of a Planck Length (10^-33 m), but some people later showed that is was possible to modify the theory for dimensions of arbitrary size. The question then falls to experimentalist to say how large they might be. As it turns out, it's easy to show that they aren't as large as a meter (unless you modify string theory in some really weird ways that few people consider plausible). Thus we can easily confirm everyone's ordinary perceptions that life at our scale is 3D. However the types of experiments to test this don't scale well, so the best that experiments can say so far is that there are no hidden dimensions on the order of a millimeter.
Scientists that think that hidden dimensions are really only just beyond the horizon of where we know they aren't are a pretty scant minority right now. Most people expect that they probably are down near the Planck Length and well out of reach. However, the neat experiments and effects (such as black holes) that could be done with access to large extra dimensions make them worth looking for, just in case.
If Sun were a black hole we wouldn't be sucked in (Score:4, Informative)
Black holes have a reputation for being mass-gobbling irreversible singularities, and they are. But this doesn't mean a black hole where the Sun is would swallow the Earth. I'm not an expert so someone can correct me if they know it better or more accurately.
Any amount of mass can be turned into a black hole - you just have to crush it into a small enough space. This is because every bit of matter has an event horizon, including the Sun (or the Earth for that matter). The difference with the Sun and most things is that the event horizon for the amount of matter in the sun is smaller than the Sun. If you crushed all of Sun's matter into a sufficiently tiny space that it was all inside, then everything else that moved inside would collapse and not return.
What most people don't realise is that if the Sun spontaneously turned into a black hole, we wouldn't die from being sucked in. We'd die from lack of solar energy. Because the Sun-black-hole would have the same mass, everything orbiting it would continue to orbit it the same way it is at the moment. The only big difference would be when something happened to wander inside the event horizon at which point it wouldn't leave, if you ignore all the wierd relativity things that go on at that point at least.
So I guess the point is that just because someone says they might be able to make a black hole, it doesn't mean you'll be instantly sucked in tommorrow without any warning.
~Why Black Holes Go Away~ (Score:5, Informative)
Fast forward a few years, scientists make a black hole. Why doesnt it destroy the earth?
1) The black hole weighs no more than the particles slammed together to make it. It has essentially zero pull on anything. A grain of salt would make an incredibly more effective attractor.
So you say, yes, but the black hole will persist and continue to grow in mass by swallowing more and more particles.
But the scientists in the Times article say the black hole will "evaporate".
The following paragraph, from this page [microsoft.com], states it well:
Since the 1970s, it has been known that black holes are not completely black. In fact, they emit very low-energy radiation called Hawking radiation. The lower the mass of a black hole, the higher the energy of the emitted Hawking radiation. As a black hole radiates, its mass decreases, and it starts emitting more and more radiation, causing it to evaporate more and more rapidly. Eventually, it shrinks to around the Planck mass, the point at which its DeBroglie wavelength is equal to the Schwarzschild radius. At this point, we no longer know what happens, since to describe physics at the Planck scale requires a theory of quantum gravity.
Same argument applies, and it's ironclad. (Score:4, Informative)
If they're going to do something which at least sounds dangerous, I would really like it if they could say, "Nothing can possibly go wrong", not, "Our understanding is incomplete."
Actually, there's a pretty ironclad argument for this being safe - the same one that comes up every time the press starts fearmongering about more powerful accelerators:
Cosmic rays with energies far higher than will be produced by any accelerator any time soon have been striking the earth and the moon for billions of years. If high-energy collisioins could cause catastrophy, they would have already, because they've been happening in our neighbourhood for quite a while.
The fact that nothing around here has been sucked into a black hole yet leads us to conclude that if micro-black-holes can be formed, they don't do much.
Our current models of black holes suggest that micro-holes would evapourate in a burst of Hawking radiation almost as soon as they're formed. The smaller the hole, the more intense the Hawking radiation (and so the faster it loses mass).
Re:~Why Black Holes Go Away~ (Score:2, Informative)
The origin of Hawking radiation is not due to the fact that something actually escapes from the black hole; this is still impossible. What's essentially believed to happen is this: something weird happens at the event horizon, causing particle/antiparticle pairs to be created. Most of these pairs are destroyed immediately, but some are aligned in such a way that the particle is ejected outside the event horizon, while the antiparticle falls inside. The antiparticle destroys a particle inside the black hole, while the outside particle escapes and is measured as Hawking radiation. The net result of this process is that something has been "relocated" to the outside of the black hole, even though nothing technically "escaped".
If this happens faster than the black hole can acquire new matter, then it will eventually evaporate.
Re:Nothing can possibly go wrong! (Score:3, Informative)
Small black holes aren't dangerous (Score:3, Informative)
The exact formula is rather complex, but for average environments, a black hole has to be more than a 1000 tons at creation to be of any danger. Considering that particle accelerators never handle material heavier than a few atoms, we are quite a bit on the safe side...