eli5: What do we use to measure the accuracy of the worlds most accurate clock?

Question

The Optical Lattice clock will lose one second every 15 billion years.
How do we know?

In: 0

Answer 1

Today, the most precise clocks are based on a natural atomic resonance of the cesium atom—the atomic equivalent of a pendulum.

[src](https://www.laserfocusworld.com/test-measurement/research/article/16556429/alloptical-atomic-clock-may-be-worlds-most-precise)