- 1500-1300 BC Sundials were first used in Egypt to measure the time of day by the sun’s shadow.
- 400 BC Greeks Used a water clock, which measured the outflow of water from a vessel ,to measure time.
- 980 AD Alfred the Great(a Saxon king)
used burning candles to measure time. - 1000 AD At the time of sung Dynasty ,candles and burning incense marked time in china.
- 1400AD Mechanical clocks were built in Europe ,using a mainspring and balance wheel.
- 1583 AD Galileo Galilee realized that the frequency of a pendulum’s swing depended on its length.
- 1657 AD Christian Huygens invented the first pendulum clock, capable of far greater accuracy than any preceding timekeeper. But the clock did not work at sea.
- 1759 AD John Harrison built a clock that last only 5 seconds on a voyage from England to Jamaica.
- 1839 AD Telegraph
invented, allowing instant transmission of time signals. - 1840 AD time ball was dropped at noon each day at the US naval Observatory. Ships in the harbour used the ball to set their clocks.
- 1850 AD Regional time zone established in New England to coordinate railroad schedules, halting confusion due to using local Sun time at every station.
- 1884 AD Twenty-five countries accept Greenwich, England, as the prime meridian . The prime meridian gradually became the basis for time throughout the world.
- 1905 AD A radio signal was transmitted from Washington DC to help ships find longitude.
- 1928 AD W.A. Marrison of Bell laboratories built the first Quartz clock,accurate to within 1-2 thousandths of a second per day. Quartz technology was later adopted for use in wristwatches.
- 1945 AD Physicist Isador Rabi suggested making a clock based on the study of atoms , using a method called atomic beam magnetic resonance.
- 1949 AD National Bureau of Standards (now the National Institute of Standards and Technology, or NIST) built the first atomic clock, using ammonia.
- 1967 AD A second was formally defined as 9192631770 vibrations of the Cesium atom.For the first time, time was made independent of astronomical bodies.
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