# Time Measurement

View Notes

## How is Time Measured?

Time measurement is not an easy procedure. It isn't very easy for many. So, how is time measured, you will first need to work on how is a minute, an hour or a day measured. In ancient times, people noted the fact that certain periodic happenings never changed. These included the changes in seasons and the sunset and sunrise. These were probably the very first attempts that our ancestors made towards measuring time. The whole procedure was quite simple and the results gained were pretty accurate. The sundial was the very first device used for measuring time. For the ones who do not know what is the study and science of time measurement called, the answer is horology.

### How is Time Measured Using Periodic Motion?

Periodic motion is the movement of a particular object that tends to repeat itself after a specific time. The time taken by the object for repeating its movement is called the period, which is measured in seconds. The number of movement repetitions taking place every second is called frequency. The unit used for measuring frequency is hertz. Periodic motion or happenings such as sunrise and sunset were formerly used for measuring time. Other periodic movements used for time measurement include the phases of the moon; the changing of the seasons; the water flow and the movements of the stars in the sky.

Here, it is essential to note that the moon takes approximately 29.5 days to change its phase from one full moon to the next phase. Hence, this periodic movement was the most natural way of measuring a month in ancient times. The changes in seasons marked the beginning and the end of a year. Take, for example, monsoon takes exactly a year to return, and thus our ancestors kept track of the number of days in a year by keeping a watch on the changes in seasons. Measuring a year was quite crucial, considering that human beings depended on the rains for their crops. Proper knowledge about the rains was essential for raising a good yield. With advancements made in the field of technology, more sophisticated ways of measuring time came to the forefront. Later, simple pendulums started being used for measuring time. As long as the bob weight and pendulum length remained unchanged, the pendulum oscillates at a constant pace.

### 5 Ancient Time Measuring Devices

This image depicts various types of time measuring devices.Â

There can be no doubt in the fact that time has played an essential role in the existence of human beings on this planet. We live in the times of clocks and watches using the quartz technology for time measurement. But, in ancient times, time was measured using different ways. There were different time measuring devices used in ancient times. Initially, the natural phenomena around were used for the measurement of time in ancient times. The very first instruments used for time measurement were the mountain and the stick. As shadows shortened, it would be noon, and as they lengthened, it would be night. The five most popular ancient time measuring devices are:

Obelisks or Sundials

Sundials were widely used in 1500 B.C for dividing the interval of time between sunrise and sunset in 12 different parts. Obelisks of ancient Egypt made during 3500 B.C were the oldest shadow clocks used for measuring time. Shadows moving to various marks helped the Egyptians in calculating time, and thus they divided a day into two sections.

Sand-Glass

Hour-glasses or sand-glasses made of a couple of conical glasses linked vertically through a narrow neck were used for measuring time in the 14th century. The sand-glass was for measuring the passage of a period. The width and size of the glass along with the sand quantity in both the sections denoted it. Use of a sand-glass was a more accurate way of measuring time than a candle clock or water clock.

Candle Clock or Water Clocks

These instruments were for measuring time by observing the flow of water from a container or into a container. In the candle clock, the candle was marked using numbers, and the melting wax denoted the period. The time calculations varied with the use of these instruments mainly because of variations in the flow of water.

Pendulum

Galileo Galilei came up with the process of using a pendulum for measuring time. The movement of the pendulum was ideal for keeping track of the period. Way back in 1930, the pendulum was considered one of the most accurate instruments for measuring time. It was Christian Huygens who invented the pendulum clock in 1658 and later the motion of the pendulum started being used as a way of measuring time.

Quartz

The Quartz clocks came into being in the 1930s with Albert Eisenstein proposing the theories of relativity and defining time as the fourth dimension.

In these present times, the piezoelectric crystal, known as quartz, is used for measuring time. Instruments used to measure time in physics include lasers and atomic inventions. In the future, other modern forms of time measuring devices will be appearing in the market for sure.