I’ve alway liked clocks. I suppose I could tell quite a few “clock stories,” but I won’t — at least not now. A few weeks ago I got a clock, from Anne, for my birthday. It’s very small in a precisely machined “box.” It’s suppose to look like a present. It’s pretty cool in and of itself, but I was particularly impressed by the precision with which it’s made — I had to take it apart to put a battery in it.
Well, this got me to wondering… how come this clock, and every other clock in the world has 12 numbers, or “marks.” signifying 12 hours? How did 12 become significant in our perception of time?
We got Locke a “Fitbit” watch for his last birthday. I wanted to get him an analog watch so he’d learn to tell time — not just read numbers on his “watch.” Emily, who just turned 11 still has a bit of trouble telling time on an analog clock. Why is that? Well, when you think about it, it’s no wonder kids have trouble learning how to tell time. Just look at the way we divide up a day….
24 hours are divided into two parts — the “day” lasting 12 hours and the “night”lasting 12 hours.
One of those hours contains 60 minutes and each of those minutes has 60 seconds. And to go even further, each second is then divided into 1000 milliseconds.
So how did this all come to be? Today, we typically use the decimal number system — a system that is believed to have originated because it made it easy for us to count things on our fingers. Way, way back, when humans were still exploring the wonders of the world and finding answers to their many questions, many other numerical systems were commonly used.
The Egyptians and Babylonians were the first to divide the day into smaller parts and used duodecimal (base 12) and sexagesimal (base 60) numeral systems.
The 24-hour day concept comes from the ancient Egyptians. They divided the day into 10 hours using devices like shadow clocks and then added one hour at each end ( one for twilight and one at the end of the day.) Later, the Egyptians made a T-shaped bar that was calibrated to divide the time between sunrise and sunset into 12 parts. But — the absence of sunlight made it hard to divide the time at night. So their nighttime division of time was based on the observation of stars. Without getting into all the details, they chose 36 star groups (small constellations that rose consecutively on the horizon as the earth rotated.) These constellations were called “decans.” Again, skipping the details, the rise of each decan marked an hour and they ended up with 12 hours in each night.
At that point in time, the hours didn’t have a fixed length. It was the Greek astronomers that helped make life simpler by equally dividing 24 hours using the Babylonian’s sexagesimal (base 60) system for astronomical calculations. So, for convenience, they further divided an hour into 60 minutes and each minute into 60 seconds. (The concept of milliseconds is very modern and since we use a base 10 system, each second is divided into 1000 milliseconds.) So I think that’s kind of how we got to where we are today.
Of course for many thousand of years, nobody needed a clock. They got up at dawn to tend their fields, when they were done, they went home and when it got dark, everyone went to sleep. Nobody ever asked “what time is it?” They could guess how far along the day was by the height of the sun and approximate the passing of a month from the waxing and waning of the moon.
But today we take knowing the time, and the day of the year, for granted. And even though the units for measuring time sometimes don’t make logical sense, they seem to be here to stay. But the way we measure time has changed significantly over the centuries. The Egyptians used sundials and watercocks that were also used by several civilizations after them. Hourglasses were an important time-keeping device before the invention of mechanical clocks. The development of quartz watches and atomic clocks has make it possible to measure time with increasing accuracy.
Today, the standard definition for time is no longer based on the rotation of the Earth around the Sun, but on atomic time. A second is defined as: “9,192,631.770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133, atom.”
Based on that information, I think it’s time for a drink…..
—60 —