History of Time
Sundial first used in Egypt to measure the time of day by the sun's shadow. Hours are shorter in winter and longer in summer.
The Egyptians invented the water clock. It consisted of two containers of water, one of which was higher than the other.
The candle clock method was not very efficient though. There are many different types of waxes and incenses, and they do not all melt at the same rate.
The spring-driven clock was the first successful mechanical clock. It was originally constructed by Peter Henlein, a German engineer.
Invented in France in 1338, the hourglass involves an amount of fine sand pouring through a small hole constantly in a certain amount of time.
Invented in Europe, the weight clock was the first mechanical clock ever created.
Twenty-five countries accept Greenwich, England, as the prime meridian. The prime meridian gradually becomes the basis for time throughout the world. Liberia finally adopts it in 1972.
Telegraph invented, allowing instant transmission of time signals.
Christian Huygens invents the first pendulum clock, capable of far greater accuracy than any preceding timekeeper. But the clock does not work at sea.
A second is formally defined as 9,192,631,770 vibrations of the cesium atom. For the first time, time is not defined by the movement of astronomical bodies.
Time is more popular than ever: about half-a-billion watches are sold each year.
National Bureau of Standards builds the first atomic clock, using ammonia.
The quartz clock, invented by Warren A Marrison, is the type of analog clock used in the modern age
A radio time signal starts being transmitted from Washington DC to help ships find longitude.