Some questions in physics seem rather frivolous but actually lead to very interesting debates. One of these was asked by the folks at Sixty Symbols who asked this: what would happen if you stuck your hand into the beam of the Large Hadron Collider? Some answers to that are in the first four minutes of the video there. Phil Plait offers an opinion as well, on his Bad Astronomy blog:
It’s complicated! You have to think about the energy of the beam, of course, but also the energy of a given proton as it moves at 99.9999% the speed of light. But that number doesn’t mean anything if the proton doesn’t actually interact with the matter in your hand, so you have to consider the “cross-section” of the atoms in your hand. Think of it this way: if you shoot a gun at a target, you make a hole. But if you shoot a gun at a fishing net, it might pass right through. Most of the area of a fishing net is holes! The nuclei of atoms are very small compared to the atoms themselves, so in a sense most of you is empty space.
And there’s more. The beam of the LHC is in a small tube that’s a high-grade vacuum — getting your hand in there would be tough. And there’s a magnetic field of ferocious strength there, so I hope you don’t have any metal bits in you. And there are actually two beams going in opposite directions.
So taken in total, I’m not sure what would happen. If the total energy of the beams were dumped into your hand all at once, it would act like dropping a bomb on you. One of the scientists in the video says the total energy in the beams is 300 megajoules, which is equivalent to 75 kilograms (165 pounds) of TNT going off. That’s about 300 sticks of dynamite, if you’re curious.
Don’t Cross the LHC Stream [Bad Astronomy]