Time was one of the most important inventions in human history. It is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future. Or in simple terms, it is what the clock reads! 😐
Clock, is a device to keep track of time. Without clocks, we wouldn't know if we were late to work, or when you have to take that medication. Clocks made it possible to tell the time. The history of clocks goes back to a past when there were no clocks! However, societies across the globe developed their own methods of time keeping, unified by space! The position of celestial objects plays a major role here. The Indian system was purely based on astrological assumptions. A day was divided into long periods called prahars. Each prahar is three hours long and the whole day was divided into eight prahars, four for the day and four for the night. This was a pretty rough unit of time. The more accurate unit was, hours, with twelve hours a day. Further more accurate, minutes, 60 minutes an hour and seconds with 60 seconds every minute. "60" because of the Babylonians! They didn't have a decade system of numbers but a number system going from 0 to 60! (Why!???)
Early clocks didn't have minute and second hands. They only measured hours and one hour is a very long time. the problem with these clocks was that time was way too inaccurate. At the end of the day, the clocks were deviated by up to 20 minutes from the actual time. So the the sun was high and the only clock in town was turned to 12 from the 20 minutes offset, it was pretty huge change. Such an error was not acceptable while sailing to distant lands. The sailors used to have two clocks, one with the home time and another with local time. When you are at the equator and your local clock is 4 minutes behind the home clock, you have moved about 110km westward or one longitude. An inaccurate clock like of those days was of no use to sailors if the an error of 20 minutes was possible on the home clock.
This lead to the invention of the pendulum clock. It was based on a wheel and lock mechanism with a pendulum. At the initial position of the pendulum, the anchor would lock the wheel. However, with the swing of the pendulum the wheel would escape and rotate by one second. (See the illustration)
This was way more accurate as a person can calculate the exact weight of the bob, length of the rod and the placing of teeth in the gear train to get exactly one second for each escapement. Pendulum clocks were accurate. But they still had a margin of error, a 15 second delay at the end of the day due to various factors.
Until now, we were just calculating the favorable alterations in our system to get an hour or a second. Basically, we were trying to figure out what "changeable" physical quantities are required to get one second. For a more precise time keeping, clock makers now turned to frequency.
Now we had spring driven clocks. A spring driven clock, unlike a pendulum, clock has a huge number of teeth on the gear train of the wheel. You now have to calculate how many "tiks" of the anchor results in one second and precisely prepare gears to run the different hands of the clock. Unlike the pendulum clock, where a temperature change can cause a change in the length of the rod and thus changing the value of one second, a pure gear system depends upon the ratio of the number of teeth on adjacent gears. the circumference of the gears may change a bit due to temperature changes but the change is uniform across the clock and thus the ratio remains the same. Thus, no change in the value of second. This, not only made clocks more accurate but also lead to the creation of pocket watches. Time was now in the pockets.
In the 20th century, it found that Quartz crystal oscillates about 32,768 times every second when subjected to an external voltage. This property of quartz crystal lead to the making of modern quartz clocks. We know almost precisely, how many times the crystal would vibrate every second when subjected to electric voltage. Thus, we can now tell more precisely, the value of a second. You can now see that by using frequency or number of oscillations, we can standardize the most fundamental division of time.
Further developments gave us more precise time keeping devices with oscillators generating frequencies in megahertz, or an oscillation every millionth of a second. Such oscillators are used in modern day computers. In fact, the clocks in computers can oscillate over a billion times a second or in Gigahertz frequency. This gave us a time frame of a nanosecond.
A high frequency can not only be obtained using crystal, but also using oscillator circuits. An RC Oscillator circuit can generate a frequency in kHz, thus providing us with a cheaper and a "good enough" accurate time keeping. These circuits are used in cheap digital watches an clocks for home where accuracy is not a major factor.
Clock, is a device to keep track of time. Without clocks, we wouldn't know if we were late to work, or when you have to take that medication. Clocks made it possible to tell the time. The history of clocks goes back to a past when there were no clocks! However, societies across the globe developed their own methods of time keeping, unified by space! The position of celestial objects plays a major role here. The Indian system was purely based on astrological assumptions. A day was divided into long periods called prahars. Each prahar is three hours long and the whole day was divided into eight prahars, four for the day and four for the night. This was a pretty rough unit of time. The more accurate unit was, hours, with twelve hours a day. Further more accurate, minutes, 60 minutes an hour and seconds with 60 seconds every minute. "60" because of the Babylonians! They didn't have a decade system of numbers but a number system going from 0 to 60! (Why!???)
Early clocks didn't have minute and second hands. They only measured hours and one hour is a very long time. the problem with these clocks was that time was way too inaccurate. At the end of the day, the clocks were deviated by up to 20 minutes from the actual time. So the the sun was high and the only clock in town was turned to 12 from the 20 minutes offset, it was pretty huge change. Such an error was not acceptable while sailing to distant lands. The sailors used to have two clocks, one with the home time and another with local time. When you are at the equator and your local clock is 4 minutes behind the home clock, you have moved about 110km westward or one longitude. An inaccurate clock like of those days was of no use to sailors if the an error of 20 minutes was possible on the home clock.
This lead to the invention of the pendulum clock. It was based on a wheel and lock mechanism with a pendulum. At the initial position of the pendulum, the anchor would lock the wheel. However, with the swing of the pendulum the wheel would escape and rotate by one second. (See the illustration)
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| Courtesy:- en.wikipedia.org Wikimedia Commons |
Until now, we were just calculating the favorable alterations in our system to get an hour or a second. Basically, we were trying to figure out what "changeable" physical quantities are required to get one second. For a more precise time keeping, clock makers now turned to frequency.
Now we had spring driven clocks. A spring driven clock, unlike a pendulum, clock has a huge number of teeth on the gear train of the wheel. You now have to calculate how many "tiks" of the anchor results in one second and precisely prepare gears to run the different hands of the clock. Unlike the pendulum clock, where a temperature change can cause a change in the length of the rod and thus changing the value of one second, a pure gear system depends upon the ratio of the number of teeth on adjacent gears. the circumference of the gears may change a bit due to temperature changes but the change is uniform across the clock and thus the ratio remains the same. Thus, no change in the value of second. This, not only made clocks more accurate but also lead to the creation of pocket watches. Time was now in the pockets.
In the 20th century, it found that Quartz crystal oscillates about 32,768 times every second when subjected to an external voltage. This property of quartz crystal lead to the making of modern quartz clocks. We know almost precisely, how many times the crystal would vibrate every second when subjected to electric voltage. Thus, we can now tell more precisely, the value of a second. You can now see that by using frequency or number of oscillations, we can standardize the most fundamental division of time.
Further developments gave us more precise time keeping devices with oscillators generating frequencies in megahertz, or an oscillation every millionth of a second. Such oscillators are used in modern day computers. In fact, the clocks in computers can oscillate over a billion times a second or in Gigahertz frequency. This gave us a time frame of a nanosecond.
A high frequency can not only be obtained using crystal, but also using oscillator circuits. An RC Oscillator circuit can generate a frequency in kHz, thus providing us with a cheaper and a "good enough" accurate time keeping. These circuits are used in cheap digital watches an clocks for home where accuracy is not a major factor.
When we talk about a second, we used to define it as a sixtieth, of a sixtieth of a tweny-fourth of the period between one noon to another. However, definitions have changed with the Atomic Clock. When it was noticed that a day can vary, we needed a much more accurate definition of a second. With the atomic clock, a second is defined as (brace yourselves!) 9,192,631,770 oscillations of the Cesium-133 atom. The clock loses one second every 138 Million years. These clocks are used in navigation satellites like GPS, GLONASS and NAVIC to accurately pin-point a location and also in the universal time keeping constant, UTC to accurately keep a measure of time. That huge number up there, 9.192x10^9 oscillations of a Cs-133 atom is the universally accepted definition of a second.(Where universe refers to planet Earth and assuming alien life is inexistent!)
That, my readers, was the story of time. From 1 day/24/60/60 to a number long enough to be someone's contact number!
Feel free to put your views in the comments below.
Have a good Day!
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