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History of Time Keeping

History of Time Keeping

Detail of famous astronomical clock Prazski orloj (Prague, Czech Republic)
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We waste time. We save time. We lose time and gain time. We have all the time in the world. But none of us is powerful enough to stop time or slow it down. Time keeping was one of humankind’s earliest achievements and has come a long way since antiquity. Let’s explore the evolution of timekeeping and see how humans went from sundials to today’s digital clocks.

 

A Lot Happens in 24 Hours

Your heart beats around 100,000 times. Lightning strikes the Earth a million times. Astronauts aboard the International space station will see 16 sunrises and 16 sunsets. About 3,87,564 babies are born, and more than a lakh people die daily. Yes, a lot happens in 24 hours. But why is a day divided into 24 hours, and who decided how to calculate it?

 

We’re on the Clock

“Time is money” and “we can buy anything but time.” The history of the clock is a fascinating one. It shows the interest and ingenuity in measuring time from time immemorial.

Archaeological findings suggest that people have been trying to determine time since time began. In the earliest days, people used astronomical phenomena as a guide, reading the time of the day with the help of shadows. We may have used an elementary calendar marking religious festivals and times to plant and harvest. What’s interesting is that timekeeping developed independently in all cultures. It seems to be essential for humans to know the time and be able to record it.

Today, life without calendars and time measurement is unimaginable. And even as the smartphone gradually replaces the wristwatch, timepieces are our everyday companions. In the world of work, production processes, and leisure time – without time measurement, we would not be able to show up on time for meetings, engage in global trade, or make appointments.

There are three main types of clocks: mechanical, electrical, and atomic. They all need a source of power, a device to keep the parts moving at regular intervals, and a way to display the results. Clocks may be strictly functional or highly decorative, but they all provide an invaluable service.

From wristwatches and hourglasses to wall clocks or handmade cuckoo clocks, there’s no escaping the magic of these mysterious everyday objects.

 

Ancient Clocks

The sky and nature have always been our timekeepers. The sun and the moon divided the day into two parts. The first people to develop a means of telling time with calendars and clocks were the ancient Egyptians. By about 2800 BC, the Egyptians established a 365-day calendar based on their observations on the rising and setting of the star, Sirius, and periodic inundation of the Nile upon which their agriculture relied. By 2100 BC, they divided a plan to divide the day into 24 hours.

Stone Sundial against a blue sky and some green tree tops.

Simultaneously, sundials or shadow clocks were developed to measure the time during the day. A sundial indicates the time of day by the position of the shadow of some object on which the sun’s rays fall. The shadow clocks originating in Egypt divided the day into hours. However, the shadow clocks varied the lengths of shadow lines throughout the year and thus were unreliable.

For millennia, people have used sundials to tell the time using the sun’s apparent position in the sky. There are many kinds of sundials, but they all have in common, a gnomon, a thin rod that casts a shadow onto the dial, and a flat plane or platform. As the sun’s position changes, the shadow it casts aligns with the lines marking each hour, indicating the time of the day. The accuracy of a sundial is affected by several factors, including that the angle of Earth’s rotation isn’t perfectly perpendicular, and Earth isn’t perfectly spherical.

The Egyptian shadow clock has a straight base with a raised crosspiece at one end. A scale with time divisions is inscribed on the floor. The clock is set east-west and is reversed at midday. At night the Egyptians observed the positions of the stars to tell time. Their diagonal star clocks used the movements of the constellations, requiring acute observations and complex calculations to establish a reliable time. Another method was to use burning ropes or candles marked at hourly intervals.

By 1500 BC, Egyptian recorders and priests had invented a more accurate way of telling time – the water clock. This device, also known as a clepsydra, uses the steady dripping of water from a vessel to drive a mechanical device that determines the hour. Similar water clocks were also used in Babylonia. In ancient Greece, water clocks were used in court proceedings to limit speaking time; the phrase “Time has run out” comes from the water clock. Water clocks had the great advantage of working at night.

Some water clocks rang bells and gongs, and others opened doors and windows to show little figures of people or moved pointers, dials, and astrological models of the universe. However, the water clocks had limitations as the flow rate was challenging to control precisely, making a high degree of accuracy impossible. The Romans adopted the tenets of water clocks and sundials from other cultures. The Moors and Arabs also used these techniques and continued developing them.

These early time-keeping devices all had their limitations. Shadow clocks and Sundials didn’t work at night; water clocks were notoriously inaccurate as water flows at different rates depending on the ambient temperature, freezing in winter and evaporating in summer.

 

Time in the Middle Ages

In the Middle Ages, religious observances were signaled by the ringing of church bells. The first mechanical clock was installed in 1283 at Dunstable Priory in England. Powered by descending weights, the clock was made possible by the invention of the verge escapement, which controlled and regulated this power. The verge escapement made a greater degree of accuracy possible.

The Church was involved in developing clocks to enable the clergy to say their prayers at the correct times. As the new gadget caught on, more clocks were installed at Exeter in 1284 and St Paul’s Cathedral, London, in 1286.

The clocks in the doorkeepers’ rooms synchronized medieval society with their striking of the hours. With the later emergence of tower clocks, the public could finally tell the time at a glance. Only a few monarchs and wealthy citizens owned a domestic clock – mostly complicated astronomical clocks that were popular for symbolic reasons.

It was in the 14th century that the hourglass was also developed, which served to measure shorter intervals of time. The hourglass is a narrow-waisted glass that measures an hour or other increment of time by the time sand, water, or mercury runs from an upper compartment into a lower one. The quest for good clocks intensified with burgeoning late medieval patronage and scientific investigation. From the 15th century onwards, clockmakers organized themselves into self-reliant guilds.

 

The Development of Modern Timekeeping

The mechanical clock of the mid-1300s was driven by falling weights attached to the gear trains. The clock’s gear train is the totality of the gears and pinions in the movement. Since the gear trains were regulated by friction, they could be inaccurate by as much as two hours a day and needed constant adjustment. Some can still be found today, with examples in England and France dating to the 14th Century. Many are exquisite works of art, like the Prague Astronomical Clock.

These mechanical clocks were the prevailing timepiece until the development of the pendulum clock in the late 17th Century by Christiaan Huygens. In 1656 the Dutch astronomer and physicist Christiaan Huygens designed the first weight-driven clock in which a pendulum controlled the motion. For greater accuracy, many existing tower clocks were converted to the new pendulum mechanism.

Huygens’s breakthrough was only possible due to Galileo. Who illustrated in 1583 that successive pendulum beats always take place in the same length of time, irrespective of the distance through which the pendulum swings.

  

 The Pendulum Clock

About 100 years later, Robert Hooke, an English physicist, invented the anchor escapement, a device that produced the first truly accurate pendulum clock. By 1680 a minute hand was added to the hour hand, and a few years later, the pendulum clock had a second hand.

This type of clock, epitomized by the grandfather clock, has a pendulum end enclosed case. It is driven by a descending weight that causes a drum to rotate. Gears transmit the motion of the drum to an escapement. Each time the pendulum swings, the detent releases the teeth on the escapement wheel, and the drum turns slightly until the other arm of the detent again catches a tooth on the wheel.

Antique wooden grandfather clock

With the invention of the mainspring in the 15th Century, clocks could be portable for the first time. They would gradually reduce the size until pocket watches first appeared in the 17th Century. The development of the balanced spring and clock balance wheels in the mid-17th Century significantly improved timekeeping device accuracy. Despite these advancements, pendulum clocks remained one of the most accurate clock designs well into the 20th Century.

The basic design of this clock remained unchanged for centuries, although its accuracy improved. This same method powers clocks placed in church towers and public buildings, including the most famous tower clock in the world. The clock on the Houses of Parliament in London, England, popularly known as Big Ben, after the giant bell on which the hours are struck.

 

The Further Development of Timekeeping

Even as far back as the renaissance, timepieces were continually being developed. As the first pocket watches were produced, international competition arose among clockmakers, who outdid each other in creating technical and artistic masterpieces. Even minute and second hands were now built into the timepieces, making it possible to measure time more precisely.

Watchmaking took a different turn in America; from the beginning of the 19th century, the industrial production of pocket watches began there. The clock became mass-produced and was available to people from different social classes.

In the 18th century, watches were no longer only in the market as art objects. The colonial powers actively traded in goods they imported from overseas to Europe. Maritime shipping demanded accurate timekeeping to ascertain longitude, which was finally supplied by the marine chronometer invented in 1759

Experimental quartz clocks were built as early as 1927.  This invention was the single most significant contribution to precision time measurement. If the watch says “quartz,” it’s powered by a crystal. Quartz is a transparent mineral made of silicon and oxygen that vibrates at a precise frequency when an electric current is passed through it. But although quartz clocks are pretty accurate, they are still not the most exact form of timekeeping. Quartz crystals vibrate at minutely different frequencies depending on whether they are in a warm or cool environment, making them gain or lose a few seconds over a long period.

 

Atomic Clocks

The most precise timekeepers are atomic clocks. To regulate the electronic components in the clock, nuclear watches use masers, similar in principle to lasers, to amplify and count the microwaves-high-frequency radio waves emitted by vibrating atoms. The first atomic clocks had errors of one second in 30 years—or one part in a billion.

The development of electric and quartz clocks in the late 1800s and early 1900s led to chronometers with accuracies surpassing those of the best mechanical timepieces. In the mid-1950s, quartz chronometers were outmoded by timepieces whose oscillations derived from the vibrations of collections of atoms—the first atomic clocks.

Because atomic clocks are the most accurate type of clock, scientists use them in their work. The nuclear clock has made possible new, exact techniques for measuring time and distance.

 

Into the Future

Timekeeping devices are an integral part of the technology we see around us. GPS satellites have at least two cesium and rubidium atomic clocks on board to calculate the time delay of the signals and provide an accurate location reading. In December 2018, scientists at the National Institute of Standards and Technology developed two clocks using 1,000 atoms of the element of ytterbium in grids of lasers.

These clocks are so precise that they can show the effects of gravity on the earth, helping us measure the space-time continuum. So far, this is the most accurate form of timekeeping, but new technology will emerge in the next decade, century, or millennium. One thing’s certain— we’ve come a long way since the sundial.

 

 

Edited by Michael Moss

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