False vacuum decay is a process where the universe is in a stable state that seems “normal,” but it’s actually not the most stable state it could be. Think of it like sitting in a comfy chair that’s actually a little wobbly. If something triggers it, the chair might suddenly collapse and turn into a better one. In the universe, when this “false vacuum” decays, everything could change very quickly, and the universe would shift to a more stable state. This change could happen at any time, even though we don’t notice it yet.

When you stick a suction cup on a wall, the vacuum that holds it on slowly decays until it falls off. Sometimes you stick it on so firmly and perfectly, that it stays on the wall even after the vacuum is gone, hence “false vacuum decay”.