Why the LHC Won't Destroy the World 508
An anonymous reader writes "Most people are aware of the recent articles contending that the Large Hadron Collider at CERN might destroy the world. While most scientists have no such concerns, a recent preprint released to arxiv systematically dismantles the notion. The gist of the argument is this: Everything that will be created at the LHC is already being created by cosmic rays. If a black hole created by the LHC is interactive enough to destroy the world within the lifetime of the sun, similar black holes are already being created by cosmic rays. Such black holes would be stopped by dense cosmic objects (neutron stars and white dwarfs). A black hole stopped in one of these objects would eventually absorb it. We see sufficiently old neutron stars in the sky, thus any black hole that could be created at the LHC, even if it is stable, would have no effect on the earth on any meaningful timescale."
Black holes vs. negative strangelets ? (Score:5, Interesting)
Wasn't the actual "danger" in question the creation of stable negative strangelets (which would gobble up regular matter through electrostatic attraction, not through gravity like a black hole) ?
But still, if there was such a thing, cosmic rays would have created one "naturally" by now.
Logic (Score:2, Interesting)
"cosmic rays" argument is bogus (Score:4, Interesting)
Let me be quite clear that I don't think the LHC is likely to destroy the Earth.
However, the argument that what the LHC does is equivalent to collisions of cosmic rays with the atmosphere is bogus. The LHC's collisions between two particle streams with equal and opposite momentum could create things that are more or less at rest with respect to the Earth; a cosmic ray hitting the atmosphere carries momentum that will cause any resultant particles to move away from us very quickly.
Stopped black hole? (Score:4, Interesting)
Re:"cosmic rays" argument is bogus (Score:4, Interesting)
I think it's pretty unlikely that two particles are going to hit each other 100% square on and all that energy will somehow cancel out and the result will just dead stop and drop to the floor. The particles in the LHC are going to be colliding with so much energy that the results are most certainly going to be moving at a very high rate of speed, high enough that something like the Earth's gravity will hardly be noticeable to it.
Why Is It (Score:5, Interesting)
Why is it that physicists on and in favor of this project (and those that are following this story) are even remotely surprised by the "Create a black hole, and destroy the world" rhetoric?
We've heard all the sensational "Black holes are the ultimate destructive force" commentary from Astronomers for decades seen all the cool Black hole animations, etceteras, ad nausium.
In my opinion, all the sensationalism surrounding the Black holes to start with was a ploy for funding. Now that same story line shows it's dark side, and people seemed surprised at the outcry and at overly dramatic fear of the LHC.
I'm not saying that sensationalizing science is a bad thing per se, just that people shouldn't be surprised when it bites them on the ass.
Re:Hang on a minute (Score:5, Interesting)
Actually we wouldn't. The black hole would not be any heavier than the earth (the moon would continue to orbit it as if nothing had happened, and the black hole would happily circle around the sun). Since the earth's mass is not that impressive, the black hole would have to be tiny, so the area around it where the gravity would significantly bend the universe would also be quite small, making our painful (but swift) deaths rather unspectacular.
Yeah I know. 'WOOOOSH!'
Re:Hang on a minute (Score:5, Interesting)
Actually, it will take a while. The event horizon of the hole will be small; the interaction cross-section with ordinary matter in the Earth is tiny. So it will orbit the centre of the Earth, absorbing a few atoms on each pass, gradually increasing in mass.
We'll notice by the time it reaches the mass of, say, a decent-sized mountain. It will cause local tides. Volcanism. Earthquakes. We won't die of spaghettification; we'll die because something awful inside the earth is whipping up the mantle like a blancmange and shredding the whole crust.
Worst case scenario? (Score:3, Interesting)
So, what is the worst case scenario, and, would I notice it?
Black Holes as a power source? (Score:3, Interesting)
Please don't tell me what I'm thinking of is a ZPM, damn stargate Deus Ex machina devices...
Re:"cosmic rays" argument is bogus (Score:1, Interesting)
Is the argument bogus for eVoting too?
Fueling the arguments of paper ballot supporters are incidents such as a 2003 Belgian election in which almost 4,100 extra votes for Maria Vindevoghel's Communist Party were recorded in a precinct of Brussels due to a malfunction triggered by a cosmic ray.
http://catless.ncl.ac.uk/Risks/23.46.html#subj13
http://catless.ncl.ac.uk/Risks/23.47.html#subj7
Group collision mergers (Score:4, Interesting)
They also haven't accounted for all possible group particle mergers and interactions in the LHC. Unlike nature, in a particle accelerator they have groups of high energy particles moving in close proximity. In nature, we have lone high energy particles. We don't know what we can create in group collision mergers of high energy particles and even though these are rare compared with single particle interactions, they can still occur. Even if a black hole like particle was briefly formed and then hit by another particle or two or twenty, then what?. The point is, we simply don't know whats possible, but its very likely to be a different situation than simply a lone particle able to break down. If a group collision merger occured in nature, it would most likely be very rarely occuring, but it could be enough to help account for some fraction of the mass of the universe. We simply don't know, but we do know that in a particle accelerator, its going to happen a lot more often than in nature and we don't know what kinds of reactions group high energy mergers could cause.
While its (mostly) safe to assume single high energy particles are not going to be a problem, as they happen relatively often in nature, we cannot say the same for multiple collsion mergers and all possible interactions of multiple particles, as we simply do not know for sure. The current various theories are not proof its safe and the fact we cannot account for so much energy and mass in the universe is a very good reason to suspect our theories are wrong.
Also the fact they are building the LHC is proof in itself that they build it to learn, so they don't currently know for sure. Also for all their planning, even that magnet failure showed their theories and multi-million dollar design plans about how the machine should function can still go wrong. Humans make mistakes. Thats fine, we all accept that, but making a mistake with the LHC could potentially be the most serious mistake in human history.
What concerns me is their intense desire to learn is going to bias their judgment. (I know my desire to learn has biased my judgment from time to time), but this is the most important experiment in human history, so its vital it doesn't go wrong in any way, or it could be the last experiment.
Re:Hang on a minute (Score:5, Interesting)
It doesn't matter where the black hole is created. It, like all black holes, is infinitesmal in size and infinitely dense. It'll fall right to the center of the Earth as if all the matter in between wasn't even there. Also, having started out life with the mass of a few atoms, it's going to take a looooooooooong time for it to destroy the planet. Black holes don't "suck" matter in. They can only pull matter in with the force of their own gravity--which is going to be very very tiny.
It certainly won't shift the Earth's center of gravity appreciably.
Re:Black holes vs. negative strangelets ? (Score:3, Interesting)
Okay, so it sounds like the theory is that you could create a microscopic black hole that would immediately sink to the center of the earth and orbit there, very slowly accreting matter. But we argue against the possibility saying "cosmic rays would already have created them". Is it possible that they already have and that mini black holes are milling about the earth's center as we speak? Hmm, we have had a lot of earthquakes lately ...
How small are we talking about? (Score:5, Interesting)
Well, exactly how small black holes _are_ we talking about? Because it seems to me that the whole scare is due to a few people's not really understanding physics.
Gravity is actually the weakest force at a particle level. But ok, let's imagine a really really small gravity well.
Arguably the interesting thing about one would be, basically, "up to what distance can it gobble things up." In other words, the the Schwarzschild radius [wikipedia.org].
I'll use simplified version, which is: 3km for something weighing as much as our Sun, and it varies linearly with mass from there. Literally. For Something the size of Earth it would be 9mm, btw, but they won't collide particles weighing the same as _Earth_ there. If they did, I'd worry about _recoil_ before I worry about black holes.
So how big a black hole will they create there? Say, about the weight of two neutrons? _Three_ neutrons? Heck, let's be generous and smash a whole five neutrons together. Each neutron weighs 1.67492729x10^27 kg. So 5 of them is very approximately 8x10^-27 kg. The Sun weighs 1.9891×10^30 kg, let's say 2x10^30 kg.
So we get roughly 3km times 4x10^-57 km, or 4x10^-54 metres. That's the ridiculously infinitesimal size, up to which it could gobble matter. By comparison a helium atom has a radius of 31 picometres, or approx 3x10^-11 metres. Our black hole is about 10 to the 43'th power smaller than that. Write a zero, a dot, 42 more zeroes and a 1. That's how much smaller that black hole is than a helium atom.
To be absorbed by it, another particle would have to come that close to it, overcoming all other forces. Which become pretty damn strong when you try to get that close.
In effect, the _only_ way for that "black hole" to gobble any other particle, is for that other particle to be shot directly at it with an even bigger particle accelerator. With some incredible (and thanks to that guy Heisenberg, also pretty much impossible) accuracy. Otherwise, it will be bounced around by the other atoms, without ever getting close enough to one to actually absorb one and get bigger and meaner.
If that's the big threat to Earth, well, I've seen scarier kittens than that ;)
Re:Hang on a minute (Score:2, Interesting)
Crazy theories (Score:3, Interesting)
My favorite crazy LHC theory is explained in glorious detail in this video [youtube.com]. The guy seems reasonable to start, but he manages to pull in more kook-memes than you'd think possible. Delicious!
Re:Famous "last particle" (Score:5, Interesting)
What's this Either/Or crap? Just do both.
Re:Hang on a minute (Score:3, Interesting)
Wouldn't it evaporate quickly, as small black holes are want to do? How do we know that it would even have a chance to absorb a particle before it fizzes away?
Re:Famous "last particle" (Score:3, Interesting)
Obviously only Ubuntu fans would get that. I don't really care about the karma.
For Microsofties and Apple fruitcakes, the current Ubuntu release is called Hardy Heron. It was initially to be called Hardy Hadron, but luckily Shuttleworth reads /. and got fed up with the phallic jokes.