Brain Greene had a useful op-ed in yesterday's New York Times. He's discussing all the fuss about the Large Hadron Collider:
After more than a decade of development and construction, involving thousands of scientists from dozens of countries at a cost of some $8 billion, the "on" switch for the collider was thrown this week. So what we can expect?
The collider's workings are straightforward: at full power, trillions of protons will be injected into the otherwise empty track and set racing in opposite directions at speeds exceeding 99.999999 percent of the speed of light -- fast enough so that every second the protons will cycle the entire track more than 11,000 times and engage in more than half a billion head-on collisions.
Interesting stuff. I'm not too sure about this next part, however:
Why might one worry that this would be a problem? Because black holes have a reputation for rapacity. If a black hole is produced under Geneva, might it swallow Switzerland and continue on a ravenous rampage until the earth is devoured?It's a reasonable question with a definite answer: no.
Work that made Stephen Hawking famous establishes that tiny black holes would disintegrate in a minuscule fraction of a second, long enough for physicists to reap the benefits of having produced them, but short enough to avoid their wreacking any havoc.
Seems a bit convenient, wouldn't you say?
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Calculate the time-to-evaporation of a black hole with given mass. Substitute the mass of a proton.
Sometimes, life is convenient.
Blake -
You're obviously part of the conspiracy.
Of course. They have cookies.
The same theory that predicts that the LHC may form micro black holes also predicts that they will evaporate effectively instantly. I don't think there is any model that suggests one without the other.
Jason,
I'm with you here. A few weeks ago I might have called you an uninformed alarmist, but since the news outlets have been saying things like "Skeptics claim that the LHC could produce a black hole that...", I'm on board! After all, I am a skeptic.
Question: wasn't the other argument against Doomsday that high energy energy particles, cosmic rays, shower us on a daily basis? The argument is that under such conditions we should have been eaten by a Black Hole already.
Or are the odds very different?
Anyone who wagers that no black hole will occur and then immediately eat the earth will of course be the only possible winner of that wager.
I did the calculation earlier today because some friends were asking me why they shouldn't worry about a black hole. The time to evaporate is something like 10^-85 seconds. And that is using the total energy (around 2 micro joules of energy), not just the rest mass of a proton (15 nano joules). That is essentially non-existent, considering it is substantially shorter than the Planck time.
too late...
Yeah, I've found using physics to allay fears of the LHC isn't really effective when talking to people who've been taken in by Luddite attention-whore Walter L. Wagner's nonsense (he pulled the same stunt before RHIC came online). It's better to go with what Dan seems to be getting at and point out that cosmic rays hit Earth with far more energy than the LHC can muster about once a second (assuming I didn't screw up my back-of-the-envelope calculation too badly). Hell, we've detected cosmic rays with energies >10^7 the maximum for the LHC (the "Oh-My-God particle").
DA, it's better than that. The whole concept of a black hole is nonsensical below the Planck mass, since its Compton wavelength is then larger than its Schwarzchild radius (in the case of the highest energies the LHC can get to, 30 orders of magnitude bigger).
I second qubit. And I'd also like to point out that the Standard Model is a point-particle theory in which all fermions are smaller than their Schwarzchild radius. Even at rest when their Compton wavelength is maximal.
Theories with extended objects don't fail in this way.
*ducks*
The odds are different; black holes produced by cosmic ray collisions or the LHC don't pose a risk if they are not captured by the Earth. The LHC is special in that the center of mass of the collisions will have low velocity relative to the Earth. That is why white dwarf stars take the place of the Earth in the argument, as they would capture putative black holes produced by cosmic rays.
Anyone who wagers that no black hole will occur and then immediately eat the earth will of course be the only possible winner of that wager.
Peter - thanks for the laugh!
I agree that this experiment would not take place without that assurance based on other understandings that have been proven or at least constructed in reliable physics or math.
Personally, I am ecstatic about this experiment and cannot wait for the outcome :)
Also, in mothersguess's comment - quite true!
KAS
Seems any black hole created would be traveling far faster than escape velocity anyway.
That is why white dwarf stars take the place of the Earth in the argument, as they would capture putative black holes produced by cosmic rays.
I'm scratching my head here trying to understand what you mean by this, Andrew. Why would a supposed black hole produced by cosmic rays somehow go light-years away to a white dwarf against gravity? Or are you saying that a white dwarf would capture a micro black hole that hit it, but Earth wouldn't? Either way, you're wrong, and you'd need to explain why there are no observed black holes below the Chandrasekhar limit (or even close to it) and why white dwarfs last more than a few years.
Oh, and eddie, that's a good point about particles in the standard model. If the Compton wavelength is bigger than the Schwarzchild radius, it's just a particle with no event horizon. Of course, things look different in QFTs where there are no particles.
[my turn to duck]
The latter. But I am wrong as charged black holes produced by cosmic rays would be captured by the Earth (if they lasted long enough).
Indeed, Andrew. Though I guess to be super-pedantic, if it had a kinetic energy over ~10^10 eV it could break through, as that's around where latitude-dependence of cosmic ray flux goes away. Of course, any kinetic energy it had after forming is energy that can't go into its mass, and the more that goes into mass the slower it's moving at the same kinetic energy.
BTW, sorry if I sounded a bit crotchety in my last post (it sure sounds that way to me now). I had just spent 3 hours trying to fix my internet connection without success, so I wasn't feeling the most diplomatic.
^ When nerds get cranky.
Thanks. I didn't take it personally. I hope your posts mean your internet connection is working again; I can get pretty frustrated with computers myself.
Anyone remember this Long forgotton sci-fi movie of the 1980's:
http://www.youtube.com/watch?v=85q6CNo-BRw&eurl=http://www.movieretriev…
After the events of this week someone's bound to do a remake !
I have to say he did not address the fears of people who thought that the project would import
Midget Negro Prostitutes
into Europe. They were concerned because they had heard a lot of converage about mini black ho's.
(sorry)
Supposing a tiny black hole didn't evaporate, what would really happen? Wouldn't something the size of the Planck length have a great deal of trouble finding matter to smack into?
From what I understand, LHC can only produce a black hole if space-time has more than 4 dimensions as string theory predicts. Due to the extra dimensions the evaporation and other formulas slightly alter, to make it just possible. (essentially the minimal mass of a black hole is dimension dependent) Though, still the black hole would almost instantaneously evaporate. It is this evaporation signal that many string theorist are waiting for, because it would be a direct confirmation of part of their theory.
Jianying is right. For the LHC to produce a black hole, not only is it necessary for there to be more than 4 dimensions, but those dimensions have to be a particular size. They have to be small enough to have not been previously detected, but large enough to affect physics at the scales probed by the LHC. In practice, this means they have to be about 10^{16} times bigger than the dimensions generically predicted by string theory. There are theories that include dimensions of that size, but at this point they're highly speculative.
And, of course, even if they do produce black holes they won't destroy the Earth for all the reason that have been mentioned billions of times by now.
The Wagner/Sancho lawsuit in Hawaii has been dismissed. Walter has stated an intention to appeal before October 26. The judge said that the NEPA law only applies to major Federal actions and the construction of CERN is under the control of CERN, not the US Government, and the US Government spent less than 10% of the costs. So by existing precedent, there's no cause to make a Federal case out of it.
http://sciforums.com/showpost.php?p=2029021&postcount=35
Also discussed, the European case represented a contract dispute with CERN over the LEP construction as an anti-LHC-because-it-was-going-to-kill-us suit, and comparisons with creationist rhetoric.