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Atomic time

Over the years scientists have broken up time into increasingly smaller bits. In the early 2000s, a scientist can measure a millionth of a billionth of a billionth of a second. To divide time with such precision, researchers again turned to something found in nature—a vibrating atom. The negative charges in atoms oscillate at a regular and nonchanging rhythm. Atomic clocks tell time by measuring the frequency of oscillations of one particular atom, cesium. One second is now defined as the time it takes a cesium atom to make 9,192,631,770 oscillations.

The first atomic clock was developed in the 1940s and its accuracy was improved upon in the early 1990s. This clock is so accurate that it loses or gains just one second every 1.6 million years.

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1. Introduction
2. Breaking up time
3. Swing time
4. A mess of times
5. Space-time: It's all relative
6. Atomic time
7. Experiment 1 - Pendulums: How do the length, weight, and swing angle of a pendulum affect its oscillation time?
8. Experiment 2 - Water Clock: Does the amount of water in a water clock affect its accuracy?
9. Design Your Own Experiment