History of Time Measurement

Humanity has observed the movement of the sun, moon, and stars to measure time since ancient times. The sexagesimal system created by the Babylonians is still used for time and angle measurement, and the 24-hour system developed by the Egyptians has become the global standard. Modern atomic clocks use vibrations of cesium-133 atoms to define one second as 9,192,631,770 vibrations.

Interesting Facts

• Planck time (5.4×10⁻⁴⁴ seconds) is the shortest physically meaningful time unit.
• Computer jiffy varies by system, but usually means 1/100 second or 1/60 second.
• A day is not exactly 24 hours. Earths rotation speed is gradually slowing down, and it is expected that a day will be 25 hours in about 100 million years.