When was telling time invented

This shadow clock or sundial permitted one to measure the passage of hours within a day. Another very early form of clock to tell the time was the water clock. The water clock was used by the ancient Greeks. It is believed that the ancient Greeks started using these early timekeeping devices around BC. These clocks were mainly used to determine the hours of nighttime, but they may also have been used for daylight hours as well.

The hourglass is another form of early timekeeping device that was used in ancient times. The hourglass was constructed from two separate glass bulbs that were rounded. These two glass bulbs were connected by a neck of narrow glass that was situated between the bulbs.

This hourglass contained particles of sand within it, and when it was turned upside down, a measured amount of sand particles would drop down from the top part of the glass to the bottom part of the glass. The hourglass of ancient times is said to be the early predecessor for the egg timer of modern times.

During World War I, however, the pocket watch was modified so that it could be strapped to the wrist, where it could be viewed more readily on the battlefield. With the help of a substantial marketing campaign, the masculine fashion for wristwatches caught on after the war. Self-winding mechanical wristwatches made their appearance during the s.

Housed in a partial vacuum to minimize the effects of barometric pressure and equipped with a pendulum largely unaffected by temperature variations, Riefler's regulators attained an accuracy of a tenth of a second a day and were thus adopted by nearly every astronomical observatory.

Further progress came several decades later, when English railroad engineer William H. Shortt designed a so-called free pendulum clock that reputedly kept time to within about a second a year.

Shortt's system incorporated two pendulum clocks, one a master housed in an evacuated tank and the other a slave which contained the time dials. Every 30 seconds the slave clock gave an electromagnetic impulse to, and was in turn regulated by, the master clock pendulum, which was thus nearly free from mechanical disturbances.

Although Shortt clocks began to displace Rieflers as observatory regulators during the s, their superiority was short-lived. In Warren A. Marrison, an engineer at Bell Laboratories in New York, discovered an extremely uniform and reliable frequency source that was as revolutionary for timekeeping as the pendulum had been years earlier. Developed originally for use in radio broadcasting, the quartz crystal vibrates at a highly regular rate when excited by an electric current [ see illustration in box on opposite page ].

The first quartz clocks installed at the Royal Observatory in varied by only two thousandths of a second a day.

By the end of World War II, this accuracy had improved to the equivalent of a second every 30 years. Quartz-crystal technology did not remain the premier frequency standard for long either, however. Subsequent experiments in both the U.

Today the averaged times of cesium clocks in various parts of the world provide the standard frequency for Coordinated Universal Time, which has an accuracy of better than one nanosecond a day. Up to the midth century, the sidereal day, the period of the earth's rotation on its axis in relation to the stars, was used to determine standard time. This practice had been retained even though it had been suspected since the late 18th century that our planet's axial rotation was not entirely constant.

The rise of cesium clocks capable of measuring discrepancies in the earth's spin, however, meant that a change was necessary.

A new definition of the second, based on the resonant frequency of the cesium atom, was adopted as the new standard unit of time in The precise measurement of time is of such fundamental importance to science that the search for even greater accuracy continues. Current and coming generations of atomic clocks, such as the hydrogen maser a frequency oscillator , the cesium fountain and, in particular, the optical clock both frequency discriminators , are expected to deliver an accuracy more precisely, a stability of femtoseconds quadrillionths of a second over a day [see Ultimate Clocks, by W.

Wayt Gibbs, on page 56]. Although our ability to measure time will surely improve in the future, nothing will change the fact that it is the one thing of which we will never have enough.

William J. Andrewes is a museum consultant and maker of precision sundials who has specialized in the history of time measurement for more than 30 years. He has worked at several scholarly institutions, including Harvard University. Andrewes is a museum consultant and maker of precision sundials www. For his contributions to horology, he was awarded the Harrison Gold Medal in Already a subscriber?

Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. Reckoning Dates ACCORDING TO archaeological evidence, the Babylonians and Egyptians began to measure time at least 5, years ago, introducing calendars to organize and coordinate communal activities and public events, to schedule the shipment of goods and, in particular, to regulate cycles of planting and harvesting.

Recent Articles by William J. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Create Account See Subscription Options. Continue reading with a Scientific American subscription. The earliest time measurement devices before clocks and watches were the sundial, hourglass and water clock. Find out more about these types of clock here.

The forerunners to the sundial were poles and sticks as well as larger objects such as pyramids and other tall structures. Later the more formal sundial was invented. It is generally a round disk marked with the hours like a clock.

It has an upright structure that casts a shadow on the disk - this is how time is measured with the sundial. The hourglass was also used in ancient times. It was made up of two rounded glass bulbs connected by a narrow n eck of glass between them.

When the hourglass is turned upside down, a measured amount of sand particles stream through from the top to bottom bulb of glass. Today's egg timers are modern versions of the hourglass. Wonder Words recess clock oven cycle cast means typical shortage device section obelisks natural fortunately appliance appointment constellation hourglass particular Take the Wonder Word Challenge.

Join the Discussion. Maya Apr 4, Life would probably be horrific because you would miss you classes! Apr 4, Isaiah Apr 19, I would probably not survive without time, I don'y think anyone would. Apr 20, Savannah Apr 14, Very educational! This helped me with my lesson in Science class!

Thank you!!! Apr 17, That's great! So you're studying time in science class? Owen McFry Apr 14, Glad you liked it, Owen! How many clocks are in your home? Matthew Jones Apr 14, Aj Feb 28, This could be inappropriate for kids because it says "bladder".

Chellby Apr 14, Mar 1, Feb 6, Matthew Jan 30, Never knew! Thanks for sharing! I know some fun facts as well! Random fact that has nothing to do with this! If you would throw a clock into a black hole, it would appear stopped, but if you jump in, it would look normal. Jan 31, That's crazy, Matthew! Thanks for sharing that with us! Matthew Jan 31, It's no prob! If you wanna learn some more stuff, look up Super Plant Dolan!

Xavier Romer Jan 27, I am learning about sundials.