The longest decay

摘要

If you'd been watching since the birth of the universe, you wouldn't have had a hope of glimpsing one. Hang around for a trillion trillion years, long after the stars have fizzled out and cosmic heat death beckons, and you still wouldn't be close. In fact, believe the laws of physics and you could spend an eternity searching in vain. Physicists don't let such odds deter them. Across the planet, thousands are mounting a search for one of the rarest processes in nature: a form of radioactive decay that, if sighted, could reveal why the universe contains anything at all. Radioactive decay is nature's alchemy. It is capable of transforming certain heavier elements into lighter ones, but it runs on its own schedule - some elements have lifetimes of minutes, others millennia. These radioactive processes are vital to our very existence, with one collection known as beta decays helping to power the sun. The most familiar type of beta decay causes a neutron in an atomic nucleus to transform into a proton, ejecting an electron and an antineutrino, the neutrino's antimatter partner, in the process.