Thanks for posting that reference to the (Pierre) Auger Observatory with links and all. We loved to point out that at current accelerator tech, our high energy

Thanks for posting that reference to the (Pierre) Auger Observatory with links and all. We loved to point out that at current accelerator tech, our high energy events would need a ring with about the same radius as the Earth's distance from the sun. What also blows my mind is that there aren't really credible/supported theories about what process or effect may be able to put as much energy into a single particle. Whatever it is, my money is on that is a process that happens at large scales (just like Fermi acceleration), so the "giant accelerator" bit remains somewhat true, except we don't have to build it. :)