Scientists have measured the shortest unit of time ever, the time it takes for a particle of light to cross a hydrogen molecule. A zeptosecond is a trillionth of a billionth of a second, or a decimal point followed by 20 zeroes and a 1.

You can read all about it on space.com

Also, a cool name for a post-rock band, or a part of a song - like: "as lonely as the "1" at the end of the zeptosecond"