What is Time? Sunclocks, Jake Jackson's These Fantastic Worlds

What is Time? Sunclocks

The use of the sun to approximate the time is as old as recorded time itself and there are many different methods of using the shadow created by the sun.

(This is the second post of Time and Clocks, the thread that follows Time and Calendars.)

The first measure of the hours was a simple stick. The Babylonians, in the plains surrounding the Euphrates river before 4000 bc, used such a stick, which they later developed by dividing the day into 12 daylight hours, marked by the stick’s shadow inside a scalloped stone, and 12 night-time hours.

Tibetan priests and Indian fakirs used sundial sticks with a hole at the top and a small peg inserted which cast a small shadow on to a series of units marked on the stick itself.

Of Shadows and Obelisks

The earliest known record of a sun clock is in Egypt, during the time of Thutmosis III, sometime between 1501 and 1448 BCE: a 30-cm (11-in) simple stone device, in the form of a T which, when pointed at the sun, threw a shadow down the length of its stem, marking time against lines scored into the stone. It could be used up until noon when it had to be turned over.

Egypt also made extensive use of obelisks, the oldest being built in 3500 BCE, marking noon, the longest and shortest days and eventually further sub­divisions. Inevitably the Romans, having conquered most of the known world by the last century before Christ, also used obelisks, such as the one built by Augustus in 27 BCE, which still looks out of the Campus Martius in Rome. The ancient Greeks used the measurement of footsteps along the shadow of a column.

Ancient Obelisks were used as sundials

Ancient Obelisks were used as sundial to give basic indications of time.

Large Stone Sundials

These can be found in almost every society at some point in its development, latterly as ornaments. They were, and can still be, found in a number of different forms; indeed in 30 BCE Vitruvius noted at least 13 different types in use through­­­out Italy, Greece and Asia Minor.

There is an early reference to a sundial in the Christian Bible, Kings II, XX:11:

“And Isaiah the prophet cried out to the LORD who brought the shadow ten degrees backward by which it had gone down on the dial of Ahaz.”

King Ahaz ruled Judea between 740 and 728 BCE and these lines seem to refer to the lengthening of the life of the king, using the sort of large stone dial characteristic of the period as a metaphor.

Simple sundials which could show midday and the general passage of the day (morning­tide, noontide, eventide) were placed, hanging down vertically, above doors in medieval Europe, and in the eleventh century, pocket and hand dials were in use, these hand dials performed the function of a pocket watch and were used by farmers and travellers.

Some cathedrals featured a dial on the floor of the nave, with an aperture in the roof so that a sunbeam would illuminate the hours of the day; others featured external sundials.

Ancient and Medieval sunclocks

From the early third century CE at Johannisstraße,Trier, showing Greek philosopher Anaximander of Miletus holding a sundial; from St Mary the Virgin’s Church, North Stoke, Oxfordshire; from Ely Cathedral. Images courtesy of Wikimedia Images.

Modern Sundials

In the thirteenth century, the Moroccan mathematician Abdul Hussan designed what we would understand to be the familiar sundial, with the gnomon (the hand of the dial) pointing to the North Pole and the dial itself divided into equal units. Using trigonometry which would have astonished his European contemporaries, Hussan worked out the formula for making accurate measurements at every latitude.

Since the Middle Ages, the most popular dials were horiz­ontal and became increasingly secondary in use as they provided time for setting mechanical and spring-wound clocks.

Sundials suffer from the weather, though. One intriguing way round this was achieved in first century BCE when the Syrians made a gift of a monumental, octagonal waterclock to the city of Athens. The water device ran independently of the eight sundials which were placed on each side of the clock. Each sundial was held by a wind spirit, lending it the name of the Tower of the Winds, and it became the official timekeeper of Athens.

The next post will cast much further back though, to the waterclocks.

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Posts in the Time & Clocks Thread

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