Unnatural situation, my ass. When I was that age I was worried about soil erosion, overfishing, acid rain, desertification, the greenhouse effect, global political instabilities, deforestation, air- and water pollution, population growth, nuclear waste, overuse of fertilizers and pesticides, and a dozen other 'unnatural situations' that are still problems today (and that I'm still worried about). So here's my message to the YouTube generation: if you have too much time on your hand, and have already re-applied make-up three times today, why don't you talk about these infinitely more pressing problems? Because somebody could expect you do something about it?
And how 'natural' do you think YouTube is to begin with, maybe we better shut it down - I am sometimes very sure it will cause the end of the world as we know it.
Following some further links, I eventually came via another video titled "Did Nostradamus predict the LHC will create a Black Hole?" to a site called revelation13.net where you can read the following nonsense
"But perhaps creation of a black hole is a holographic parallel to the world reaching 6.66 billion population in 2008, and the rise to power of the Antichrist in Russia. If a black hole is created by LHC, then initially it might not be noticed, but it could gravitate to the center of earth and start swallowing the earth's core, perhaps over years. Perhaps such an event could be the cause of the Mayan calendar prophesy of the December 2012 destruction of earth. Lets hope for the best in this situation. If that should happen then nothing could be done about it. I think it is an interesting coincidence that CERN is turned on as the world population reaches 6.66 billion (in April 2008), 666 being the number of the Antichrist, and as the possible Antichrist Putin reached 666 months age in April 2008. Note that 666 is the number of the Antichrist in Revelation 13, the Antichrist or Beast being a Satanic imitation of Christ. In Greek, the original language of the Bible's New Testament, each letter is also a number, and therefore a word can be connected to a number by adding the letter-numbers."
And another great find is this: Black hole eating the earth, artist's impression
And what am I doing while the end of the world is coming close and the antichrist is apparently on his way? (Or is it 'her way'? Does the antichrist have a penis? Anybody knows?) Well, what I was doing today, besides wondering whether the antichrist has a penis, is preparing a colloq I'm supposed to give next week about, guess what, black holes at the LHC. (Look at this, they've even put together a poster, isn't that nice?) Too bad I can't download the above video, I'd have loved to embed it, it is just hilarious.
So, here is again all the reasons why the LHC isn't going to create a black hole that will cause the end of the world:
- To begin with, please notice that the creation of a black hole at the LHC is *not* possible in the standard framework of Einstein's theory of General Relativity. To produce black holes at the energies LHC can reach, it needs a modification of General Relativity at small distances. This could potentially be the case if our world had large extra dimension. There is however no, absolutely no, evidence so far this is really the case. The scenario is pure speculation, a hypothesis, a theory, or call it wishful thinking .
- It is not only that there must be compactified extra-dimensions, but the parameters of that model (their size and number) have to be in the right range. We know that the case with one dimension is excluded, and two should also already have shown up in sub-mm measurements, so this case too is strongly disfavoured. There are further various constraints from astrophysics that put strong bounds on the cases with three and four. But most importantly, there is no good reason known why these extra-dimensions should have the radius they need to have so quantum gravity is observable at the LHC - no reason other than it would be nice to have it shown up at these energy scales.
- Now to come to the issue of the black holes should they be created. Hawking showed in '75 using quantum field theory in the curved spacetime caused by a collapsing matter distribution that black holes emit thermal radiation. The temperature of this radiation is inverse to the radius of the black hole. The black holes that would be produced at the LHC would be extremely tiny, ~ 10-18 meters, and thus be extremely hot ~ 1016 K (that's a 1 followed by 16 zeros). They would decay within a time scale of roughly 1 fm/c, that is 10-23 seconds. They would not even reach the detector, instead they would decay already in the collision region. The only thing that could be measured are the decay products.
- The temperature of these black holes is so hot, they can not grow even if they pass through matter of very high density, like e.g. a gluon plasma or a neutron star. The mass gain from particles coming in the black hole's way (which depends on the density) is far smaller than the mass loss from the evaporation. The density of the earth is further several orders of magnitude smaller than that of nuclear matter, so there is no way the black hole could grow. Even if you assume the black hole has a high γ-factor (and thus experiences a higher density), this is not sufficient to enable it to grow.
- Hawking radiation is *not* a quantum gravitational effect. Hawking's calculation uses two very well known ingredients that are classical General Relativity and quantum field theory. It is true that we do not know quantum gravity, but quantum gravitational effects would only become important in the very late stages of the decay, when the black hole comes into the quantum gravitational regime. This would then affect the observables (and this ambiguity is thus somewhat of an annoyance), but it does not mean the black hole could grow. The reason is that if the black hole grew, it would come into the regime where Hawking's calculation applies to very good approximation, and it would lose mass as predicted. The scale for quantum gravitational effects to be important is the curvature at the horizon, which falls with M/R3 when the black hole grows, where M is the mass of the black hole and R is its radius (which again is a function of the mass).
As to the claim that there are 'people' who doubt black holes radiate, let me first reduce 'people' to 'physicists' since there are apparently also 'people' who doubt that the earth is more then 20,000 years old, or is a sphere (at least to very good accuracy). I know exactly no physicist who doubts that black holes radiate. The one work that I know of has sometimes been referred to is that by Adam Helfer. However, even he states in his paper (gr-qc/0503053) explicitly: "[These results] do not, as emphasized above, mean that black holes do not radiate [...]" .
- As has been said many times before, the earth is constantly hit by cosmic rays which undergo in interactions with particles in the earth's atmosphere collisions with a higher center-of-mass energy than the LHC will reach. If it was possible to produce a black hole this way which would then swallow the earth, this would not only very likely already have happened some billion years ago, but we should also see stars disappearing more often, especially neutron stars because of their high density. There is no evidence for that.
- It has then further been argued that the black holes at the LHC would be created in a different center of mass system, and thus not have the same average velocity with respect to the earth. This is correct but there are two points to be said here.
For one, the protons at the LHC will be accelerated to 99.9999991% of the speed of light, which is really fast. I mean, really. If you bang them together it is extremely unlikely the created particles will be in rest or even slow moving relative to the earth. Indeed, as Stefan has explained very nicely previously, their velocity will typically be far higher than the escape velocity of the earth. Pictorially speaking, consider a car crash. Things usually fly around quite a lot, already at 0.0000001% of the speed of light.
Second, even for the few black holes for which that wouldn't be the case, again, they would decay even before they hit the detector. In any case they would definitely not collect in the middle of the earth (or 'gravitate to the center of the earth' or whatever). This is a totally absurd idea that I have however come across several times. It is absurd because the center of the earth would generally not be on the produced object's trajectory (having an initial velocity), and even if it was they wouldn't stop in the center of the earth, why should they? Ever heard of energy conservation? As said previously, they are far to small (cross-section to small) to interact noticeably with the earth's matter so they wouldn't slow down. (If one really pushes it one can now go and estimate how long it would take them to slow down until they get stuck and so on. But frankly, this scenario is already so absurd that such a speculation is totally moot, and an utter waste of time, mine and yours.)
- About the claim that the LHC's risk report is biased because it has not been performed by people at "arm's length". Yes, to get a reasonable report about the difficulties the LHC might be facing I would think you ask experts. These experts are usually people working in the field. Would you prefer them to be random sampled from a phone-book? I honestly do not understand why anybody would think people working in theoretical physics have a larger interest in destroying the planet than other human beings.
To be somewhat cynical here, you'd instead think that a lot of theoretical physicists should be really nervous about the LHC because it will test their theories. And no matter what, very many of these theories will be outruled, dead, speculations no longer viable. One of these theories that can be tested is the one with large extra-dimensions. And if it isn't found hundreds of people who have worked on it must face that they have wasted their time, their publications do not describe nature, and the topic is no longer something you can use for a grant proposal.
- Finally, let me say that there is always some amount of uncertainty in everything we do. Yes, there is the possibility we are all wrong. There is also the possibility that you wake up tomorrow morning an have turned into a monstrous bug, because a cosmic ray has modified some virus to being capable altering your DNA. Or, as Arkani-Hamed put it so aptly in the recent NYT article: There is some minuscule probability, he said, “the Large Hadron Collider might make dragons that might eat us up.”
I, and I believe many of my colleagues, would really appreciate if the media - TV, print and online - would not support such catastrophe-scenarios and scientifically completely absurd scary stories just because they sell well. There is, in the community, no argument about whether mini-black holes at the LHC are a risk worth worrying about. The answer is simply no, they are not. The story about black holes created in particle colliders that swallow the earth came up first time in '99 regarding RHIC, so it has a long beard in 2008, and it's getting longer every day. If you are running out of topics for the science section, why don't you go and ask some scientists for inspiration?
I have no specific relation the theories investigated here, in fact, not being influenced by subjective preferences is part of what it means to be a scientist (whether we like that or not). I'm not telling you what I wrote here because I want money or publicity for collider physics, or any other reason of personal advantage you could accuse me of. I am telling you that just because black holes at the LHC is not something you should worry about. Worry about some real problems instead.
Further reading (strongly recommended before asking redundant questions):
Note added May 2nd: Clifford from Asymptotia asked me to clarify that with 'quantum gravity' I mean a theory in which gravity is quantized.
 And if you don't take into account the presence of large extra dimensions, you will find correctly that there is a factor 1032 missing. Before you suggest this factor has been overlooked in hundreds of peer-reviewed publications, maybe consider redoing your calculation.
 It seems to me that even if one bought his approach they would evaporate only faster. It's hard to say though because he states "it is unrealistic at present to expect to be able to make quantitative theoretic predictions".
TAGS: LHC, PHYSICS, BLACK HOLES, NOSTRADAMUS, NONSENSE, PARTICLE PHYSICS