OMG indeed. I don't completely understand this, however: However only a small fraction of this energy would be available for an interaction with a proton or neutron on Earth, with most of the energy remaining in the form of kinetic energy of the products of the interaction[citation needed]. I mean, what is the alternative that is being assumed? It smashes the proton or neutron to bits. What I want to know, is if those bits could in turn smash other neutrons and protons apart, and so on. What if it his a proton in my nose?
From search result depths, I stab at thee! When a proton or neutron (or any baryon) are collided with at energies high enough to 'smash to bits', we should start introducing quantum chromodynamics terms. Essentially, the moment you have enough energy to split a baryon, you have to overcome the colour confinement (strong force effect translating to energy binding quarks together). The energy required to accomplish that is enough to create antiquarks of complementary colours, so instead of loose quarks - aka free quarks, that can't exist below the wishy-washy string theory gluon soup energies - you get new particles. Those also carry their share of initial kinetic energy, which can produce further particles. The only 'limit' are total energy and conservation laws (energy, momentum, quantum numbers, the whole shabang). That's why you get those cascades from even a simple proton-proton collision. As to what could happen when one hits you in the nose, Anatoli Bugorski could point you in a general direction. I'd back-of-the-envelope estimated the collision to be less likely to occur by about four orders of magnitude because it's a single particle through a nose, not a packed beam through skull, but that's a good starting point for any what-ifs.
Subatomic particle interaction isn't the same as newtonian interaction. They can say "yeah, this thing has the same kinetic energy as a fastball" but that bit you read is their way of saying "but if it hit you you'd never f'ing notice because gamma rays rip right the hell through you, too, and most of them don't interact either (gamma radiation is a problem when there's an assload of gamma rays). Neutrinos are worse - they sleet through you all the time but maybe one or two in your life will knock an atom out of place. OUCH! that was mine. Not. If you haven't checked out just what a bitch it is to even detect neutrinos, here's an awesome shot of Super Kamiokande: http://www.stfc.ac.uk/PPD/resources/image/jpg/super-kamiokan...
