Who invented the measurement of time?

Who invented the measurement of time?

In the modern era, watches are behind everything people do, from work to school to sleep. Timing is also the invisible chord that makes modern infrastructure work. It is the foundation of high-speed computers that perform financial transactions, and even the GPS system that pinpoints locations on the Earth’s surface with unprecedented accuracy.

But people have probably lived with some version of the clock for a very long time. The ancient Egyptians invented the first water clocks and sundials over 3,500 years ago. Before that, people probably kept track of time with devices that haven’t survived in the archaeological record — like a stick stuck in the ground that served as a primitive sundial — or no device at all, says archaeoastronomer Rita Gautschy. at the University of Basel in Switzerland.

But when did they want to measure time?

“It’s really hard to know when people started timing,” says Gautschy. By simply observing the position of the sun rising and setting each day and noting how high the sun reaches in the sky, a person can construct a primitive calendar. These early human attempts to understand the flow of time left no trace, she says.

The oldest recorded sundial comes from Egypt and was made around 1500 BC. It consisted of a single upright stick and a roughly semi-circular base divided into 12 pie-shaped sections. The stick’s shadow gave an approximate time of day. Other ancient sundials measured time by the length of a rod’s shadow as the sun moved across the sky rather than by the movement of the shadow on the base, Gautschy explains.

“It’s a first step, and if you take that step, you can refine and also adapt to different months,” he says. Sundials must consider both time of year and latitude to be truly accurate.

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Egyptian water clocks

During the night, ancient people could keep track of time thanks to the stars’ apparent movement from east to west, Gautschy explains. And to measure discrete units of time, they used water clocks. These were containers that either had holes for the water to flow out at a steady rate, or were filled from another container and had markings on the inside to show the time steps.

The earliest surviving water clocks have been found in Egypt and Babylon, and the earliest of these date back to around 1500 BC. In China, historical records claim that water clocks were invented by the “Yellow Emperor” or Huangdi, a “half-historic, half-mythical figure,” who is said to have lived between 2717 and 2599 BC, says Zheng- Hui Hwang, a mechanical engineer at National Cheng Kung University in Taiwan, who has written about the history of ancient Chinese timing devices.

The earliest Chinese water clocks were probably flow devices and were known as louke. The ke unit divided the day into 100 equal parts from midnight to midnight. Over time, Hwang says, inventors have made these clocks more sophisticated, fitting them with multiple water supply reservoirs or regulating them in some other way to ensure the water flow remains constant.

Water would eventually lead to highly sophisticated timekeeping: In the early 700s AD, Tang dynasty monks developed a mechanical clock powered by a water wheel, Hwang says. In 1194, Sung dynasty official Shu Song built on this design to develop a 12-meter-tall mechanical clock powered by a waterwheel that functioned like the mechanical clocks that would be invented in Europe some 200 years later. .

12 sections by day, 12 by night

The ancient Chinese timing system also divided each 24-hour day into two-hour segments. This system has also been observed in ancient Japan and Korea, according to a 2004 publication in the journal Publications of the Astronomical Society of Japan.

In modern times, time still has the same length, but ancient people around the world operated with a more complex system, says David Rooney, historian of technology, former curator of timekeeping at the Royal Observatory in Greenwich, London , and author of the book About Time: A History of Civilization in Twelve Clocks (WW Norton, 2021).

Some old timing systems divided daylight into 12 parts and night into 12 parts, but since the length of days and nights varies throughout the year, except at the equator, these “seasonal times” had different duration from day to night and throughout the year. year.

“If your religion requires the time of prayer to be tied to sunrise or sunset, or if you work in the fields, as most people did then, daylight and dark patterns matter more than this idea of ​​a universal time,” says Rooney.

Seasonal time coexisted with universal time until the 15th century in Europe and until the 19th century in Japan, Rooney says. “Before, we lived with a much more complex – and rich and varied – temporal culture,” he adds.

The role of religion over time

Religion has been a big factor in normalizing the weather across cultures, both year-round and day-to-day, Gautschy says.

In ancient Mesopotamia, Anatolia (modern Iraq and Turkey) and Greece, people developed lunar calendars to track rituals and festivals, he says, while the Egyptians focused more on the solar calendar and also had a calendar based on the star Sirius.

People from Islamic cultures, Rooney says, used water clocks to track prayer and fasting, while Christians developed the mechanical clock in 14th-century Europe as a way to time prayer.

After the Romans installed the first public sundial in 263 BC. AD, says Rooney, the Roman playwright Plautus protested the new fashion for measuring time through a character in one of his plays: “May the gods condemn this man who discovered the hours first, and – yes – who was the first to place a sundial here, who broke the day, poor thing! You know, when I was young, my stomach was the only sundial, by far the best and truest of all….. But now what is there, is not eaten unless the sun says so . In fact, the city is so full of sundials that most people are crawling around, wrinkled with hunger.

It’s a remarkably modern thought to be 2,200 years old, says Rooney. “It could be written in the 21st century and said in any office. We are under the tyranny of the clock.”

*Article published on scientificamerican.com

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