The Oh-My-God Particle

http://www.fourmilab.ch/documents/OhMyGodParticle/

On the night of October 15, 1991, the Fly's Eye detected a proton with an energy of 3.2±0.9×10²⁰ electron volts.[1,2] By comparison, the recently-canceled Superconducting Super Collider (SSC) would have accelerated protons to an energy of 20 TeV, or 2×10¹³ electron volts—ten million times less. The energy of the Oh My God particle seen by the Fly's Eye is equivalent to 51 joules—enough to light a 40 watt light bulb for more than a second—equivalent, in the words of Utah physicist Pierre Sokolsky, to “a brick falling on your toe.” The particle's energy is equivalent to an American baseball travelling fifty-five miles an hour.