How Many Zeptoseconds Are in a Second?

“I’ll be there in a second,” might mean 10 minutes. If you’re serious about being fast, you should say you’ll just be a zeptosecond. It’s the shortest length of time ever measured. A zeptosecond is a trillionth of a billionth of a second. It takes 247 zeptoseconds, for a light particle, to cross a hydrogen molecule.