Sunburned? Extragalactic Radiation Is a Tiny Bit to Blame If you got a sunburn at the beach this summer, you can put 0.000000001 percent of the blame on radiation from beyond the galaxy.
Every second, every square meter of Earth is bombarded by about 10 billion photons that originated beyond the Milky Way, according to a new study that measured this "extragalactic background light" (EBL) with unprecedented accuracy. (One square meter is equivalent to 10.8 square feet.) That seems like a big number, but those 10 billion photons represent just ten-trillionths of the total number that bathe every square meter of the planet, study team members said. (The vast majority, of course, come from the sun, but the leftover radiation from the Big Bang and a few other sources also make meaningful contributions.)