Proton Decay & Black Holes

Even matter itself may not be permanent. Many grand unified theories predict that protons decay, with a half-life of at least 10^34 years and perhaps around 10^36. If so, every atom eventually falls apart, dissolving ordinary matter into lighter particles and radiation. No experiment has caught a proton decaying yet, but Japan's Super-Kamiokande detector keeps watching.

Black holes outlast matter, but not forever. Through Hawking radiation they slowly leak particles and shrink — a stellar-mass black hole evaporates in about 10^67 years, while a supermassive one lasts roughly 10^100 years.