Earlier quoted context omitted.
At 320 EeV, the OMG particle is over 5 orders of magnitude more than 1.4 PeV. It's a completely nuts amount if energy to have in a single particle: about the same as a decently moving baseball. From the particle's frame, it takes only a day to go a billion light years.
> about the same as a decently moving baseball I heard this, but it's hard to believe it's real (or, obviously, I'm misunderstanding it). What would happen if one of these hit a person in space? Would it be the same sort of feeling as getting hit by a baseball? Earlier I wondered how this much energy didn't totally wreck the detector, but someone else posted this link https://www.fourmilab.ch/documents/OhMyGodParticl…
If it does hit an atom, it produces a shower of other particles, most of which will have similarly huge energies and will probably go right through the rest of the detector and start their own showers in other matter. So you'll get a detector with a few atomic dislocations, and the rest of the energy would be distributed amongst a huge number of other interactions.
It's actually similar to x-ray "hardening", where soft x-rays are filtered out by a metal shield, leaving only harder radiation. This is carefully calibrated to allow the radiation to penetrate to a certain depth, leaving shallower tissue unharmed.
In a way, it could be better to be hit by an OMG particle than a less energetic particle, as the amount of energy that gets dumped into you is smaller: the vast, vast majority of it would be shotgunned deep into the ground under you, and only a very few molecules in you are actually affected.