Time is arguably the most important thing we have as humans, and as such it has always been our natural inclination to measure it. The system of time, as we know it, was first introduced by the Sumerians, and also used by the Babylonians. The direct origins of this ancient system are still unknown, largely because it was developed in the period before the invention of writing. It is assumed that it could date back as far as 3500 BCE. This ancient system that they developed is known as a sexagesimal system, which has a basis of 60.

Ancient Babylonian numerals. This was the sexagesimal system which has a basis of 60. / Credit: James Nickel

Remnants of ancient times are still showcased today through our continued use of dividing the hour into 60 minutes, and the minute into 60 seconds. One can presume that it was based on the utility of base 60 vs. base 10. 60 is useful because it can be divided by 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30. A key difference being that 60 can be divided by 3, while 10 cannot.

It is easy for modern day humans to showcase fractions like 1/2, 1/3, or 1/5 using the base of 10. But back in Mesopotamia it wasn’t that simple. Dividing 10 by three would’ve been quite the challenge for our ancient friends without the sexagesimal system that they inherited; 1/3, could be viewed as 20/60. Problem solved. Well, one problem really, as this counting system still had a lot of downsides…

The argument for base 10 (decimal system), base 60 (sexagesimal system), or even base 12 (duodecimal system) can still be disputed. As of now, we typically use the sexagesimal system for things like measuring time, angles, and geographical coordinates. While the decimal system was the basis of different mathematical methods used for Western business and science since the 12th century.

Obelisks (3500 BCE)

Humans used to look up to the stars and use the sunrise and sunset to determine the time. Obelisks form a key part of that history

Obelisks were four sided monuments used to determine time which date back to circa 3500 BCE. The obelisks would have shadows which would move throughout the day, depending on the position of the sun. By reading these shadows, people could get a rough estimate of the time throughout the day, even dividing the area around the obelisk to segment time further.

Ancient Egyptian obelisk / Credit: Watchprosite

The Egyptian Shadow Clock (1500 BCE)

Obelisks eventually evolved into what we know as the Egyptian shadow clock. The Egyptian shadow clock was the first ‘portable’ timepiece. It was constructed from a few parts. First, is that it has a flat rectangle as the foundation. It then has a ‘crosspiece’ which is located on one end only, and is elevated. The base then has six time divisions marked on it. In the morning, the crosspiece would face east, towards the sun. And in the afternoon, the direction would be switched by someone. This would have the crosspiece facing west as night came to fall. The shadow would then mark the time throughout the day.

Early Egyptian shadow clock - 1500 BCE / Credit: Researchgate

The Hemispherical Sundial (280 BCE)

The Hemispherical Sundial is attributed to the Babylonian astronomer Aristarchus of Samos. It was an instrument that consisted of a cubical block that would be cut into a hemispherical shape. A ‘pointer’ would then be equipped to one end, and the shadow that it would create was approximately a circular arc. This pointer’s shadow length and position would change throughout the year and according to the seasons. Details were inscribed into the stone to determine accurate time based on this shadow.

2000-year-old ancient hemispherical sundial. Discovered in 2020 in Turkey. / Credit: Daily Sabah

How A Horizontal Sundial Works

The Sundial / Credit: Encyclopedia Britannica

You have probably seen a horizontal sundial before. The sundial indicates the time of day by the position of the shadow cast by the gnomon. The shadow would move throughout the day, depending on where the sun was in proximity to the gnomon. Sundials were used by a host of different civilizations in ancient times. Very practical really, except when there is no sun…

The Water Clock (1500 BCE)

These were the earliest time keeping devices that didn’t depend on astronomy to do the heavy lifting. The earliest were found in Egyptian Pharaoh Amenhotep I’s tomb who was buried in 1500 BCE.

Later, by around 325 BCE, the Greeks started using them, in which they had also inherited the name ‘clepsydra’ (translating roughly to “water thieves”). These early clepsydras were made with a simple design. There would be two containers total. On the top there was a vessel with sloping sides where water would drip down the slopes into a small hole in the bottom at a constant rate. The container at the bottom would fill up and as the water filled up past the markings, this would indicate the changing time. These water clocks would help keep track of time during the night when the sun was not available.

Early water clock diagram / Credit: Pinterest user

Greek Philosopher Plato (428-348 BCE) also developed an early version of the alarm clock during his time on earth. His addition to the standard water clock was a tube that would allow the water to be emptied into a third container, which was enclosed except for a thin opening. As the air was pushed out, it would make a whistling noise, similar to that of a kettle.

Plato’s alarm clock / Credit: Greece High Definition

Then came the Greek inventor Ctesibius around 250 BCE. Ctesibius invented the first automatic self-regulating clock by improving upon the existing Clepsydra. This clock required no outside intervention between the input and output components of the horology system. A major improvement from the previous designs. This turned out to be the most accurate clock until the advent of the mechanical clock.

Excerpt from the History of Technological Civilization - Ctesibius’ early water clock. / Credit: N. Iwamoto

This was because Ctesibius took a new view on the water clock: instead of measuring the time based on the outflow of water, he would measure the inflow from it, which turned out to be much more accurate.

Although many of these techniques may seem primitive in the face of a tourbillon or what have you, there was still progress to be achieved - even in designed simple water clocks. And it is through looking back at this ancient history that we can really appreciate the horological developments of more recent history. Gone are the days of simply trying to know the precise time, instead, today we often think of superficial things like case materials, colours, style. Quite the ‘horological privilege’ indeed.

By: Eric Mulder

Read more:

Laki, K. “On the Origin of the Sexagesimal System.” Journal of the Washington Academy of Sciences, vol. 59, no. 1/3, 1969, pp. 24, https://www.jstor.org/stable/24535941?seq=1.
Powell, Martin A. Encyclopedia of the History of Science, Technology, and Medicine. Selin, Helaine, Springer, Dordrecht, 2008.
Lamb, Evelyn. “The Joy of Sexagesimal Floating-Point Arithmetic.” Scientific American, September 12th, 2017, https://blogs.scientificamerican.com/roots-of-unity/the-joy-of-sexagesimal-floating-point-arithmetic/.
“Decimal system.” Encyclopedia Britannica, https://www.britannica.com/science/decimal.
“A Walk Through Time - Early Clocks.” National Institute of Standards and Technology, https://www.nist.gov/pml/time-and-frequency-division/popular-links/walk-through-time/walk-through-time-early-clocks.
“Sundial.” Encyclopedia Britannica, https://www.britannica.com/technology/sundial.
“Ancient Greek Technology and Its Marvelous Works.” Greece High Definition, https://www.greecehighdefinition.com/blog/ancient-greek-technology-inventions-ancient-greece.
Norman, Jeremy. “Ctesibius Builds the First Truly Automatic Self-Regulatory Device.” History of Information, https://www.historyofinformation.com/detail.php?id=1946.