“Necessity is the Mother of Invention”, or so the saying goes. Hundreds of years ago it became necessary for humanity to organize their time into a chronological orderly system. As far back as the eighth century Hesiod wrote about celestial bodies in conjunction with the growing of crops. Crops must be harvested when certain stars were rising and the fields should be ploughed when the stars go down.
Even today some farmers still believe that crops should be planted according to the wax and the wane of the moon.
Initially the first way for people to tell the time was by watching the sun as it moved across the sky. They saw that when the shadows were shortest and the sun was directly overhead, it was the middle of the day, and when the sun was rising or setting close to the horizon it was the beginning or the end of the day. This was not an exact science.
Sundials
Sundials are the oldest devices used for measuring time. As the sun moves from East to West, the shadow of the pointer moves around the dial. When using the sundial to tell the time one looks to the number where the shadow of the sundial is pointing. The drawback with a sundial is that one can only tell the time when the sun is shining, so if it is night time, cloudy or raining then one must use other measures.
Last year I visited the picturesque village of Hawkshead in the Lake District where the famous poet William Wordsworth attended school. Over the entrance door into the school is a beautiful sundial. I had never seen a sundial before that was vertical and not horizontal.
Water Clock
A clepsidra (water thief) or water clock was invented by the Egyptians around 1400 B.C. Time was measured by water escaping from a vessel. Two containers were used and one container was placed higher than the other. Water from the higher container traveled down to the small container via a tube. Marks were placed on the containers, and the level of the water where the marks were placed on the containers told the time.
Many improvements were made to the water clocks over the years. The Greeks used them and added floats and gears attached to a stick which turned a wheel as the water rose.
The Year Divided into Months and Days
It was the Greeks who worked on a system taken from the ancient Babylonians and Egyptians. They devised that it took the Earth a year to travel around the sun, and a circle has 36o degrees. A year has 365 days so the original calender had twelve months of 30 days each with 5 days left over at the end of the year. It was also noted that it takes about thirty days to move from one zodiac sign to the next, hence the 30 day months.
Dividing the Day into Hours and Seconds.
Babylonians and Greeks divided the day into 12 hours each of light and dark in that the hours from Sunrise to Sunset was 12 hours and from Sunset to Sunrise was 12 hours. This was based on the equinox days. Unfortunately the hours are different every day which meant the water clock had to be adjusted daily to account for the difference it times between light and dark each 24 hours. Hipparchus figured out the 24 hour cycle around between 147 to 127 B.C. but most people still used the seasonal hours for many centuries. No one knows who finally figured out that it was much easier to combine the two 12 hours to make a 24 hour day. We still use the 12 hour time in most cases, whereas the Military and Medical Centers use the 24 hour clock.
Hipparchus along with other Greek astronomers used techniques devised by astronomers that had been developed by Babylonians who dwelt in Mesopotamia. The astronomical calculations used the Sumerial sexagesimal system which was a base of 60. It is not known why the number 60 was used, but it is the smallest number that is able to be divided by the first six counting numbers, and it is also divisible by the numbers 10, 12, 15, 20 and 25. This makes it convenient for determining fractions of the hour.
The Pendulum Clock
Many years passed before Peter Henlein in Germany built a spring loaded Clock around 1510, and this invention was not very precise. Another sixty plus years passed before a Clock with a minute hand was invented by Jost Burgi and this also did not work very well. Then in 1656 Christian Hugyens made a Pendulum Clock that worked very well, but it would be another few years before the minute hand was added to the clock.
The Pendulums in the first clocks had a mighty swing of around 50 degrees, and as the clocks evolved the swing lessened to about 10 to 15 degrees. By 1840 the clocks were working with external batteries and by 1940 the batteries were inside the clock.
Quarts Crystal Clocks
Quartz Crystal is a rock that looks like glass, and it is the second most abundant in the earth’s crust. An electronic oscillator is used and regulated by the quartz crystal to keep time. The signal is created by the crystal oscillator with very precise frequency, and these clocks are found to be more accurate than the mechanical clocks. Since 1970 the quartz crystal clock have been the most popular clocks used in timekeeping technology.
Modern Day Clocks.
Now we have Digital Clocks, and the popular Projection Clocks where one does not have to raise or turn his head to see the time. One has only to look at the ceiling or the wall where the light and time of the clock is projected. We have Atomic Clocks which keep the most accurate time with the use of Radio Signals from the NASA clock. Many clocks do not have to be reset when one travels or when the time is changed for Daylight Savings Time. No more excuses about the clock being wrong when one is late for work.
