History of Time Part 2: The Base for Timekeeping
We left off last week’s piece at five million, or 0.005 billion years ago when the first human ancestors appeared. Then, we did hypothetical math using collectively adopted timekeeping units to demonstrate the enormity of deep time. This week, we jump forward another 4.998 million, or 0.004998 billion years to the year 2000 BCE. This is where we find the base for modern timekeeping.
The Sumerians, Babylonians, and Egyptians
The title of this piece specifies the three most important numbers in modern human history — 12, 60, and 360. As we’ll discover, it’s also no coincidence each is a factor of the other two. The genesis of these numbers as the base for all timekeeping begins with the Sumerians in 2,000 BCE.
Sumerian Base for Timekeeping: 60 and 360
The Sumerians first observed the Sun’s orbit took 360 days to complete, which they were able to determine given the sun’s relative position to known stars. They then subdivided it further to create the first sexagesimal, or 60-based, system. The Babylonians then inherited this system from them in 1600 BCE and correlated it to the 12 astrological constellations and the known 30-day lunar cycles.
Egyptian Base for Timekeeping: 12
Already familiar with the astrological constellations and the lunar cycle, the Egyptians, already developing an advanced sundial, worked to further divide the day into 12 equal parts. The inherent issue, as we all know, is during different times of year the absolute time between sunrise and sunset varies. They first navigated this issue by identifying a cluster of 36 stars during the night they could use as reference points. They eventually pared this cluster down to 24, then to 12 stars. And so, the 24 hour day was born!
To this day, the Sumerian logic behind the sexagesimal is still debated. Some argue it was due to its ubiquity. As 60 is divisible by 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30, it made commerce easier between early traders. Additionally, it’s factoring into 12 meant people could count by the number of knuckles on each hand — three per finger with four fingers per hand. Regardless of its murky origins, this basis has stood the test of time.
The Greeks
The next major advancements in modern timekeeping would not come for another millennium. In approximately 200 BC, the astronomer Eratosthenes would use the same sexagesimal system to equally divide the earth into lines to latitude.
Hipparchus would build on this system a century later by adding an equally divided longitudinal system based on the Earth’s circular, 360 degree shape. He also postulated the day should consist of 24 hours, a concept he derived from the equal times of day and night observed on the biannual equinoxes.
During Hipparchus’ time, the Greek also constructed one of the most comprehensive timekeeping devices to date — The Tower of the Winds. The tower was an octagonal structure ~40 feet tall with a water clock on the interior and sundials on each of the exterior walls. The eight walls corresponded to one of the eight compass winds and their associated gods. The Tower served an incredibly important function as it enabled the citizens of Athens to properly orient themselves by time of day, year, and prevailing weather.
Another century passed before an improved measurement of the hour necessitated. In 150 A.D., Claudius Ptolemy became the first individual to standardize the length of the hour. He achieved this by further subdividing the latitude and longitude measurements by factors of 60. The first division was partes minutae primae. The second division was partes minutae secundae. These are the terms from which “minute” and “second” are derived. However, these terms wouldn’t become globally adopted until the beginning of the colonial period 1,600 years later.
Timekeeping on a Global Scale
Though we now understand the origins of the factorial systems, we are far from having a relatively comprehensive history of time. We barely entered the A.D. period, which in itself is another debatable timekeeping term. In the next piece, we will discuss the evolution of the mechanical clock and how colonialism enabled the standardization of timekeeping on a global scale.
Be more.
Become polymathic.
Quote of the Week: “Man alone chimes the hour. And, because of this, man alone suffers a paralyzing fear that no other creature endures. A fear of time running out.” — Mitch Albom, The Time Keeper
