Clock History - Clock Timeline
3500 BC to 2000 AD
3500 BC Sundial - A vertical stick, gnomon, or obelisk that casts a shadow|
1400 BC Water Clocks - or Clepsydras in Egypt
Candles - Marking time in China
Hourglass or Sand Clock - The Sand Clock is an instrument for measuring time, it is of ancient origin. The date of its invention is unknown. The Sand Clock was used by navies as a timekeeper and to find the speed of the ship.
1285 AD Mechanical Clocks - with an escapement with a verge and foliot which were used to sound a bell.
1335 Mechanical Clocks - with only one hand, the hour hand
1400 Mechanical Clocks - Weight driven clocks were regulated by a verge and foliot escapement or balance beam with a crown wheel
1510 Spring Powered Clock - Invented by Peter Henlein. The spring-powered clock had its problems, the slowing down when the mainspring unwound. To solve this problem Jacob Zech of Prague, in about 1525, used a Fusee to equalize the uneven pull of the spring.
1577 The Minute Hand - Jost Burgi has been credited with having invented this. However, it was not until the invention of the pendulum-regulated clock after 1656 that a minute hand became practical.
1583 Pendulum - Galileo demonstrated that successive beats of a pendulum always take place in the same length of time, regardless
1656 Pendulum - Christiaan Huygens designed the first weight-driven clock with a pendulum instead of a verge and foliot escapement or balance wheel, and this made it possible to have some accuracy in timekeeping
1761 Chronometer - John Harrison built the first marine chronometer with a spring and balance wheel escapement. It kept time on board a rolling ship to about one-fifth of a second a day during sea trials in 1762. This Chronometer gave the means of determining longitude to within one-half degree.
1840 Electrical Clock - The first Battery clock used an electrical impulse to operate the dials of a centrally located master clock
1866 Tuning Fork Clock - The first fork-clock by N. Niaudet which was shown at the Academy of Sciences expositions
1870 Time Zones - Charles Dowd invents the idea of time zones dividing the United States by meridians into zones one hour, and 15 degrees apart using Greenwich, England, as zero meridian.
1883 Railroad Time - On the recommendation of Dowd, the railroads adopt four time zones for the continental United States.
1884, Greenwich, England, is officially named the world's prime meridian by a vote at an international conference in Washington, D.C.
1906 Electrical Clock - The first self contained battery driven clock was invented. The master clock system using electricity gives a direct impulse to the pendulum which in turn moves the clocks gear train
1916 Electrical Clock - The synchronous electric motor patented by Henry Ellis Warren which runs in step with the frequency of the electric power source which in the USA is 60 cycles per second
1918 Standard Time Act - The United Stated Congress passes this act authorizing the Interstate Commerce Commission to establish standard time zones within the United States, and establishing Daylight Savings Time.
1923 Time via Radio - The National Bureau of Standards begins broadcasting time signals on shortwave radio station WWV in Washington, D.C.
1929 Quartz Crystal Clock - The piezoelectric effect was discovered by the Curie brothers in 1880. W.A. Marrison and J.W. Horton invented the original quartz clock
1949 Atomic Clock - The National Bureau of Standards (now the National Institute of Standards and Technology, or NIST) built the first atomic clock, using ammonia
1967 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
1993 Atomic Clock - NIST-7 located at the Boulder facility. NIST-7 in service from 1993 to 2000, has been the primary atomic time standard for the United States, and is among the best time standards in the world.
2000 Atomic Clock - NIST F-1, the new cesium atomic clock at NIST's Boulder facility, began its role as the nation's primary frequency standard by contributing to an international pool of the world's atomic clocks that is used to define Coordinated Universal Time (known as UTC), the official world time. It is the most accurate clock in the world.
2001 and Beyond ..... New Projects,
Technology development that is in the works
The Ultra-miniature Rubidium (Rb) Atomic Clock, 40 cubic centimeters in volume and using a minuscule one watt of power, doesn't weigh much more than a matchbox either. And
it will lose only about one second every 10,000 years !!!
How We Keep Time
Our clock and calendar measure the movement of the Sun, the Moon and the Stars as seen from Earth. That's how mankind keeps time and how we became timekeepers.
A day comes from the rotation of the earth on its axis, which takes about 24 hours, and the time of day comes from the Sun appearing to travel across the sky at about 15 degrees every hour.
The cycles of the Moon's phases is used to measure a Month. The moon takes 29.5 days to return to the same point in the sky, as referenced to the Sun, this is called a synodic month. There are about 7 lunar phases as observed from the Earth.
One year is the time taken for Earth to complete one orbit around the Sun relative to the stars, and is called a sidereal year. However, we measure a year to be the period between two successive spring equinoxes known as the Vernal Equinox and is on or about March 21, and this period is called a tropical year. The tropical year is about 20 minutes shorter than the sidereal year.
The Moon has a spin of 27.3 days which exactly coincides with one orbit around the Earth. This is the reason that we see the same face of the moon all the time, we never see the back side of the moon. That is because the Moon is in synchronous rotation with the Earth.
The Moon rotates on its own axis one time every 27.3 days.
The Moon takes 27.3 days to orbit the Earth one time, this is known as a sidereal month.
The Moon takes 29.5 days to return to the same point on the celestial sphere (stars) as referenced to the Sun because of the motion of the Earth around the Sun is known as a synodic month (moon-th).
How fast is the Earth spinning?
about 1040 miles/hr - 1670 km/hr - 0.5 km/sec
How fast is the Earth revolving around the Sun?
about 18.5 miles/sec - 30 km/sec - 30 km/sec
How fast is the Earth,
along with the Solar System
moving around the Milky Way Galaxy?
about 155 miles/sec - 250 km/sec
How fast is our Milky Way Galaxy moving through space?
about 185 miles/sec - 300 km/sec
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History of Timekeeping
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We are riding on the razor edge bow-wave of Time,
The past just fell behind us,
The present is only a microsecond and
It just ended,
The future is at hand.