For thousands of years people relied on the sun (at the time thought) moving around the earth. Some of the first documented timekeeping devices date back to Egyptian times where they would raise obelisks and look at the morphing shadow as the day went by.
One of those devices is gnomon (“one that knows or examines”) dated back 3,500 BC was probably the first device for indicating the time of day. The record of the use of gnomon in the ancient book The Rites of Zhou (2nd century BC) confirms the long history of this instrument. The gnomon indicates the time by the length of the shadow of style in the sun. It consists of two parts. The post or stone pillar standing upright on the ground to cast a shadow is called biao (gnomon) and the marked tablet lying north-south is called gui (ruler); hence, the name guibiao. Since time can be measured in the length of the shadow, to describe duration of time with length units like “inch” becomes logical.
In ancient China, the gnomon was useful instrument for astronomical observations through the centuries of Chinese civilization.
Later on Pre-Socratic Greek philosopher, Anaximander (610-546 BC) introduced the instrument to the Greeks. Greek mathematician (geometer) and astronomer, Oenopides (lived ca 450 BC) used the phrase drawn gnomon-wise to describe a line drawn vertically to another. As defined by Hero Of Alexandria, the gnomon was a figure, which when added to another figure, formed a similar figure to the original.
Also an instrument to mark hours by the observation of the shadow cast in the sun, the sundial tells the hours and minutes by the positions of the shadow. Unearthed relics show that the sundial was used before the Han Dynasty (206 BC – AD 220). The sundial had been used often until mechanical clocks were introduced to China. The main parts of a sundial are an erect style and a calibrated disk. As the sun moves in the sky, the shadow cast by the style moves like a clock hand around the disk indicating the hours.
In 2015 an Etsy seller in France has somehow managed to design a remarkable 3D-printed sundial that shows the time as digital numbers that actually change as the day progresses and the sun moves across the sky.
The digital sundial speaks to the ancient desire of keeping track of time. A desire probably as old as the concept of time itself; fascination which has lead to very advanced machines.
Both the gnomon and the sundial measure time by the shadow cast by the sun, so they cannot work on cloudy or rainy days or at night. To solve this problem, people invented the clepsydra, which shows time day and night. The Chinese name for clepsydra, louke, consists of a “lou” (leak), a leaking pot, and a “ke” (notch), a graduated arrow. The pot contains water. On the principle that water drips evenly, people can measure time by watching the number of grades on the arrow. As a time-measuring apparatus, the clepsydra is used more widely than the sundial. Many ancient Chinese men of letters left behind beautiful verses about the clepsydra. Examples are the Tang-dynasty poet Li He’s “Like water from the sea added into a clepsydra / It drips in the abandoned palace the whole night through” and the Song-dynasty poet Su Shi’s “A crescent moon hangs at the bare boughs / The clepsydra is empty, the night dies down.” Before the mechanical clock was imported into China, the clepsydra was the most widely used time-measuring device.
Expansion of ship trade in Europe and ever increasing will of sailing in open seas brought the need of having reliable and precise time measuring devices. Much improved sundial devices that were designed in China became the integral part of every ship who wanted to sail beyond the sight of the coast. From 15th century and onward, dependable and precise sundials became very popular type of clock not only at sea, but also in industry, churches, cooking and more.
By 16th century, mechanical devices started finding their way out of industrial laboratories, and time measuring devices based on pendulums and springs began appearing across the Europe, enabling a new era of dependable and precise time measuring. As centuries went on, their designs became more advanced, their structure smaller, and by the 19th century mechanical pocket, table and wall clocks became commonplace all across the world. Today, when the digital devices can be found in every corner of our civilization, measuring of time has finally become available to everyone.