Who decided how many hours in a day

We probably take it for granted, but there are lots of different ways to measure the passing of time: the one we use just won out over all the other ones. Like the Gregorian calendar, which we discussed in this episode of DNews , the clock we use has gradually evolved over time.

Since the metric system uses base of 10, it may seem like the obvious choice to base our time keeping on, but ancient cultures used all sorts of different bases. The duodecimal system, which has a base of 12, was popular probably because it takes 12 lunar cycles to make one trip around the sun. Despite the fact that they're only actually equal on seasonal equinoxes, days and nights each got assigned 12 hours. The Ancient Babylonians take credit for the hour being made up of 60 minutes.

For reasons that remain unclear, they used a base 60 system of counting. They also divided the circle into parts, which the Ancient Greeks built upon when they tried to divide the Earth into lines of longitude and latitude. They also had a separate system in which a day was divided into equal parts called 'ke', that are sometimes translated as 'mark' into English. Because of this inconvenience, much later on, in the year of our era, the number of ke in a day was reduced to 96," says Lomb.

While many cultures had their own calendars, there doesn't appear to be evidence for equivalent methods for keeping time. In , the Swiss watch company Swatch introduced the concept of a decimal Internet Time in which the day is divided into 'beats' so that each beat is equal to 1 minute The beats were denoted by the symbol, so that, for example, denotes a time period equal to six hours. I think that I am safe in stating that there will be no change from the present system of time measurement in the foreseeable future.

Keeping time While our units for measuring time seem to be here to stay, the way we measure time has changed significantly over the centuries. The Ancient Egypitians used sundials and waterclocks, as did several civilisations after them. Hourglasses were also an important time-keeping device before the invention of mechanical and pendulum clocks.

The development of modern quartz watches and atomic clocks has enabled us 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,,, periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium atom.

Tags: archaeology , inventions , mathematics , physics. Email ABC Science. The clepsydra, or water clock, was also used to record time during the night, and was perhaps the most accurate timekeeping device of the ancient world.

The timepiece--a specimen of which, found at the Temple of Ammon in Karnak, dated back to B. Once both the light and dark hours were divided into 12 parts, the concept of a hour day was in place. The concept of fixed-length hours, however, did not originate until the Hellenistic period, when Greek astronomers began using such a system for their theoretical calculations.

Hipparchus, whose work primarily took place between and B. Despite this suggestion, laypeople continued to use seasonally varying hours for many centuries. Hours of fixed length became commonplace only after mechanical clocks first appeared in Europe during the 14th century.

Hipparchus and other Greek astronomers employed astronomical techniques that were previously developed by the Babylonians, who resided in Mesopotamia.

The Babylonians made astronomical calculations in the sexagesimal base 60 system they inherited from the Sumerians, who developed it around B. Although it is unknown why 60 was chosen, it is notably convenient for expressing fractions, since 60 is the smallest number divisible by the first six counting numbers as well as by 10, 12, 15, 20 and Although it is no longer used for general computation, the sexagesimal system is still used to measure angles, geographic coordinates and time.

In fact, both the circular face of a clock and the sphere of a globe owe their divisions to a 4,year-old numeric system of the Babylonians. The Greek astronomer Eratosthenes who lived circa to B.

A century later, Hipparchus normalized the lines of latitude, making them parallel and obedient to the earth's geometry. He also devised a system of longitude lines that encompassed degrees and that ran north to south, from pole to pole.

In his treatise Almagest circa A. Each degree was divided into 60 parts, each of which was again subdivided into 60 smaller parts. The first division, partes minutae primae, or first minute, became known simply as the "minute. Minutes and seconds, however, were not used for everyday timekeeping until many centuries after the Almagest. Clock displays divided the hour into halves, thirds, quarters and sometimes even 12 parts, but never by In fact, the hour was not commonly understood to be the duration of 60 minutes.

It was not practical for the general public to consider minutes until the first mechanical clocks that displayed minutes appeared near the end of the 16th century. Even today, many clocks and wristwatches have a resolution of only one minute and do not display seconds.