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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."
See also the Review of the Safety of LHC Collisions which also appeared today, and is a more non-technical summary of the safety review.
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
black holes emit nothing.
Ha!
http://en.wikipedia.org/wiki/Hawking_radiation
how long until
Whatever small compass we shove the matter into, it'll have exactly the same amount of gravity before and after. If we happen to shove it into a tight enough space that it becomes a black hole, it will be spectacularly tiny. It'll only start to accrete matter as it interacts with it. And, it'll have to get close enough to do it.
Gravity being what it is, it seems far more likely that a black hole formed in the lab would get drawn to the Earth's center of gravity (just like everything else on Earth is) rather than causing the Earth's center of gravity to shift. Shifting the Earth's center of gravity dramatically toward the LHC would take way more energy than what we're putting into the particles at the LHC.
Program Intellivision!
- Energy of maximum LHC collision: 14 TeV
- Energy of "Oh My God Particle" cosmic ray that hit the sky over Utah in 1991: 300,000,000 TeV
Sources:Strictly speaking, black holes don't emit anything other than Hawking radiation, the x-rays are a result of rapidly accelerating gases in their accretion disk.
Right? I'm not a physicist.
In short, you are correct. If you were to magically replace our Sun with a black hole of 1 solar mass, the gravitational pull would not change. There would be a whole lot of other stuff going on, but black holes don't magically increase the gravitational pull of a mass.
If I made a blackhole out of the amount of mass that the LHC is accelerating, and put it suspended in a sealed jar on my desk, I would only feel the gravitational pull of the mass that actually is the black hole. So, unless people are having difficulty with the gravitational pull of things on their desk, I wouldn't be too worried about it.
Out of modpoints but really liked a post? 1BDkF6TtmmeZ3yqXbz9yhdYVqRYnwFoXDj
Doubt away...
The Black Hole would be a very tiny mass at creation, so small that the difference between where the earth's center of mass was before and is after is insignificant.
(In effect the before state is equal to finding the gravitational center of the earth, minus the gravitational center of a bunch of electrons that are about to power the LHC, then finding the separate center of those electrons poured into the LHC, and comparing that to the after state - where we have to find the gravitational center of the rest of the earth, and the gravitational center of the mini black hole) The center of the rest of the earth doesn't change significantly in the before and after pictures, and the power put into the LHC wasn't enough to cause any noticible wobble before it was used, was it? So it's not going to cause a wobble afterwards.
Now, assuming a stable black hole, it is drawn towards the center of the earth by gravity. Repulsion by solid matter isn't enough to stop it. (Repulsion is an electromagnetic effect - the cloud of electrons around normal nuclei push and so keep matter from passing through other matter. The hole doesn't have a cloud of electrons, so it falls. It 'wants' to go into a narrow elliptical orbit around the earth's core. (It's not falling straight towards the core, because the spot where it formed on the earth's surface has sideways velocity from the earth's rotation). As the hole falls it eats stuff, but that means it also emits electromagnetic radiation as stuff falls in. This works out in the end as a kind of friction, so the hole slows in its orbit and spirals inward. By the time it is up to a few milligrams weight, it is in a tight little orbit around the earth's core, and we are all alive, waiting for it to gradually gain weight. (If the boffins have told us). This takes a year or so, with us not really noticing anything until the hole weighs kilotonnes, at which point the last twelve hours or thereabouts get very impressive and the earth goes bye-bye.
So yes, you end up with the moon peacefully orbiting the black hole as the hole orbits the sun, in orbits that are so close to the existing ones it would be a real challenge to find the differences.
Now, the side of the moon towards us got some interesting radiation exposures during the final few minutes, perhaps enough to melt crater walls and such. The effect of all that light from the final flash might conceivably be measurable, out in the 20th decimal place or so when someone measures the Moon's rotational velocity.
Fortunately, this is all based on the idea that a black hole barely bigger than a proton is somehow stable, which we doubt very much.
Who is John Cabal?
You obviously haven't tasted CERN coffee - they have expresso machines and its generally very good. Much more likely is "This food is offal". I remember several times going to to the coop and the three dishes of the day were things like calf's head, tripe sausage and tongue...yummmm!
That is the point, it HAS been explored trillions of time already.
Cosmic rays travel through the Universe with enough energies to boil a cup of water (in one single proton). That's up to 100 000 000 times more energy than the LHC. Those particles collide with everything, at a rate of a few per square kilometer per millenium. It might seem small, but consider the size and lifetime of the Earth, the Moon, the Sun, etc; combined. Particles whose interactions with the atmosphere would have the same energy as the LHC's collisions hit us more than 100 times per day per square kilometer. Over the lifetime of the Earth, every event that can happen in 10 years of LHC operation would already have happened hundreds of thousands of times on the Earth alone. Since we're here, there's clearly no need to worry.