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Why the LHC Won't Destroy the World
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."
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.
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.
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You cannot wash away blood with blood
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.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort.
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!'
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.
Real Daleks don't climb stairs - they level the building.
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.
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.
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 ;)
A polar bear is a cartesian bear after a coordinate transform.
What's this Either/Or crap? Just do both.
Good. Cheap. Fast. Pick Two.