Sunburned? Extragalactic Radiation Is a Tiny Bit to Blame

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. 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.