They know more about it than you do obviously.
They know exactly what it's going to do
yea right! .... thats why the thing broke down! 
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here is a 'snippet' from the net, written by someone trying to explaining a few issues in layman's language
decided to write this because I've noticed a lot of people are grossly misinformed about how the LHC (Large Hadron Collider) works, and what it will be doing. I'm not an expert on physics...but I know enough to explain in laymen's terms what will be going on, and the possible doomsday scenarios people talk about. Time to get out my old physics books. I'll start by explaining some simple particle physics.
There are 3 categories of particles - leptons, quarks and bosons (force carrying particles). Quarks and leptons (fermions) are grouped in pairs and there are six of each. Leptons, such as the electron have an associated, low mass, charge-less neutrino. All twelve of these fermions also have an anti-particle that annihilate on collision with the associated anti-particle. Force carriers or bosons transmit the forces of nature. The photon transmits the electromagnetic force, the gluon transmits the strong nuclear force between quarks, intermediate vector bosons transmit the weak force and gravitons haven't been found yet but are believed to carry the force of gravity. Leptons exists individually but are not affected by gravity or the nuclear strong force. Hadrons (a subatomic particle that experience the nuclear strong force) are comprised of three quarks and can form protons and neutrons. The electron and it's corresponding neutrino, and the up and down quarks form most of the matter in our universe as the others exist only in high energy situations and decay rapidly into a more stable form. Neutrons act in keeping the nucleus of atoms more stable by keeping the protons spaced out. Neutrinos (part of the lepton category, is not a neutron - which is a hadron) are so stable that they hardly interact with other matter and all, and pass right through most of it, making it extremely hard to detect. Physicist believe there are six quarks - up (u), down (d), charm (c), strange (s), top (t), and bottom (b) and their antiquarks - antiup, antidown, anticharm, antistrange, antibottom, and antitop. Antiquarks are labelled with a letter with a bar over it. Each meson consists of one quark and one antiquark. A meson cannot be made of two quarks or two antiquarks. Examples of mesons are the pion and the kaon. Here we have a table listing the particles I've just talked about:
And here we have a simple diagram of the carbon atom:
As you can see, the atom is made up of 3 different particles (those particles are made up of smaller particles, except the electron, as you should now know). The amount of protons determines what type of element we have, and the atomic number of that element. We get isotopes of an element by changing the number of neutrons. You should understand by now, what a hadron is. The LHC will be used to collide protons, which are hadrons, hence the name, Large Hadron Collider. Now think about a nuclear bomb, why do you think it's called that? We know Uranium is an unstable element, especially the isotopes of Uranium (Uranium-235, Uranium-233 i.e. yellow cake) they use in nuclear bombs, meaning the atoms randomly decay (making Uranium radioactive). When this happens, we get a release of energy and particles, the binding forces that held that atom together get broken, hence the release of energy, known as nuclear binding energy. The mass of a nucleus is always less than the sum of the individual masses of the protons and neutrons which constitute it (known as mass defect). The difference is a measure of the nuclear binding energy which holds the nucleus together. This binding energy can be calculated from the Einstein relationship:
Nuclear binding energy = Δmc2
i.e. NBE = Change in (Mass multiplied by the Speed of light squared)
The smaller you go, the stronger the particles are bound together. The enormity of the nuclear binding energy can perhaps be better appreciated by comparing it to the binding energy of an electron in an atom, which can be knocked right off the atom if hit by a photon (the photoelectric effect), or on an even larger scale by examining the binding energy of chemical bonds. You should already understand the difference in power when comparing chemical bombs with nuclear bombs.
Mass defect = (Theoretical calculated mass) - (measured mass of nucleus)
i.e. (sum of masses of protons and neutrons) - (measured mass of nucleus)
I'm not going to bother with equations, as I will just lose people, and it's not really that relevant, the point is, binding energy is the key to the power of a nuclear bomb. When the Uranium-235 decays, particles shoot off everywhere, and if you have a mass of Uranium clumped together, if your lucky, a neutron will collide with another U-235 nucleus before it travels through all the U-235, making that nucleus highly unstable, and cause it to split instantly, thus releasing more binding energy. When the mass of Uranium is large enough, you increase the chances of this happening to such a degree where you can cause a chain reaction. The neutron has to travel through more U-235, increasing the chances of a collision with another U235 nucleus. The mass required to cause a chain reaction is called the “critical mass”. So...you have a whole clump of U-235, one atom randomly decays and starts the chain reaction, almost instantly, all the nuclei split and release their binding energy, now you have a nuclear bomb. Picture a sphere of U-235 cut in half, and when placed together they form the critical mass, when the bomb hits, one half slides down and comes into contact with the other half...simple eh?
Ever heard of a hadron bomb? Neither have I...and I don't want to...remember what I said about the binding energy getting greater as you go smaller? So, now instead of splitting nuclei (as you do in a nuclear fission bomb), your splitting hadrons, the things a nucleus is made out of, and the binding energy is much greater. I'm not sure at all...but I'd guess one of those suckers could take out our solar system...and what is the LHC attempting to do? Smash hadrons apart by colliding two of them (protons) into each other. But no need to worry...it's only two...and there would be trillions (or more) of atoms in a clump of U-235. But...what if they start a chain reaction? The pipes they will be sending the particles through should be a vacuum...but the pipe IS matter...so...they blow Geneva to Hell...or cause a chain reaction so violent it transmutes the entire Earth and us along with it? I don't think hadrons decay all that often naturally...if at all...correct me if I'm wrong....and that rubbish Steven Hawking told you about such reactions happening in our atmosphere naturally all the time is rubbish...sneaky word play to stop everyone worrying...we have nuclear reactions happening...true...but I doubt reactions on the hadronic level occur in our atmosphere all the time...now, what if the energy released isn't all that much, but it's so intense and densified (confined to a small area) it tears a hole in space and creates a black hole? All this to see what comes out...to find the “God” particle...give me a break...we all know everything is just vibrating energy in the end.
All should leave Geneva,
Saturn turns from gold to iron,
The contrary raypoz will exterminate all,
Before the coming the sky will show signs.
Migrés, migrés de Geneue trestous,
Saturne d'or en fer se changera,
Le contre raypoz exteriminera tous,
Auvant l'aruent le ciel signes fera.
Nostradamus clearly stated something would destroy Geneva...Saturn will turn from gold to iron? That implies transmutation of elements to me. Contrary raypoz? The positive rays? Protons...positive particles?
EDIT: Also...they have not smashed two protons together yet...they gave the public some story about how it has already been tested...but that wasn't the actual thing...they just ran one proton into a block of lead or something along those lines...also...I don't want it to look like I'm against it...I'm not really...after all...it's just perfectly harmless science right? Oh...and if you want to know how it actually works...if you don't already...it's simple
...the protons have positive charge...meaning they can control the path and propel them using massive super-cooled, superconducting electromagnets..they send them whizzing in opposite directions around the inside of this massive pipe (27 kilometres (17 mi) in circumference) until they get near the speed of light...then collide them into each other...
Pioneer SA-9800 amp
Marantz CD-63 mkII K1 signature
B&W DM2 speakers (1st version transmissions)
Silver High Breed Coherence LE interconnect