# Why 24 hours in a day

## Motion and Time of Class 7

There are many ancient theories about why 24 hour a day. The fact that the day was divided into 12 hours might be because 12 is a factor of 60, and both the Babylonian and Egyptian civilisationsrecognised a zodiac cycle of 12 constellations.

#### Earliest mechanical clock

In the period of development a Dutch scientist Christiaan Huygens made the very first pendulum clock, this clock was based on Galileo pendulum theory that he was given in 1582. But the mechanical clock was built in the year of 1656. Huygens' pendulum clock was so accurate that an error of less than 1 minute 24 hours. After some correction this accuracy was such that the difference in time reduced his to less than 10 seconds a day.

But in that period there was no device for keeping accurate time at sea.In the year 1761 a carpenter and instrument maker John Harrison refined techniques for temperature compensation and reducing friction. It is not known but the mechanical clock was probably invented in medieval Europe.In this device very good arrangements of gears and wheels .

The name clock is given because in French the word clock is ‘cloche’ which means bells.In the earlier time the clock was used for regular pryer.

Eventually, mechanical clocks were designed to strike the hour and even to chime the quarter-hour. However, they had only an hour hand and were not enclosed. Even the best such clocks would gain or lose up to half an hour a day.

But these types of mechanical clocks are very big and used by each and every people.This search end when spring-powered clock invented.In the year of 1500-1510 spring-powered clocks was invented by Peter Henleinof Nuremberg, Germany.Thesetypes of clocks could fit on a shelf and it became very popular among the rich people.

In 1582, Italian scientist Galileo noticed the swaying chandeliers in a cathedral. It seemed to him that the movement back and forth was always the same whether the swing was a large one or a small one. He timed the swaying with his pulse and then began experimented with swinging weights. He found that the "pendulum" was a way of marking off small intervals of time accurately.