Space: the dumbest frontier

I really love the Earth's atmosphere. Air to breathe, rain from clouds, clouds that look like bunny rabbits…and an umbrella of atoms and molecules that shelters the surface from a withering onslaught of high energy particles – AKA cosmic rays, usually the nuclei of hydrogen atoms (protons) traveling at very high speeds – coming from space. The density (flux) of these particles is low, but some of them pack quite a wallop: their energy is measured in electronvolts (eV), and although the average cosmic ray has an energy of about 3 x 10 9 eV, some have energies on the order of 10 20 eV, which is about 40 million times more energy than we can create at the Large Hadron Collider! The good news is that our atmosphere is great at shielding the surface of our planet from cosmic rays – it works as well as four meters of solid concrete. But if we travel outside the atmosphere, our umbrella is gone, and we now have a problem.