“Hickory Dickory Dock
The mouse ran up the clock
Tic-Toc Tic-Toc...”

Humans have measured time since the beginning of ... time. Some would argue that there was no time before clocks. When the alarm goes off in the morning, most of us dream of returning to those good ole days.

In 1905, while Einstein was rethinking time, Ernest Rutherford invented the radiometric clock to measure the age of rocks. The oldest rocks gave him an idea of the age of the Earth. To measure the age of the Universe, however, requires a clock that men cannot build — yet.