24 hours?
In the early days of time measurement there was no mention of the hour. People used body measurements, for example by measuring the length of their own shadow with their feet, or they built simple tools like this grazing light clock, which consists of three pieces of wood.
Image: Replica of an Egyptian sundial from the time of Seti I (1290 to 1279 BC).
This "clock" was about dividing the time from sunrise to sunset. The crossbar (shadow caster, gnomon) was placed facing east in the morning. The shadow then moved from west to east on the longitudinal beam - from left to right in the picture. When the shadow no longer fell on the measuring rod, the clock was rotated 180° to measure the afternoon time.
Dividing the day into twelve hours was found in the 2nd century BC. BC with the Greek astronomer Hipparchus. The Egyptian counting method was adopted, counting the four by three finger bones instead of the fingers.
The counting of the twelve hours of day began at sunrise and ended at sunset, when the twelve hours of night began. This resulted in temporal hours that varied in length depending on the season.
Since the first wheel clocks only struck the hour, adapting to the different hours was no problem. The weights on the balance beams were moved either inwards (faster - winter) or outwards (slower - summer) depending on the season.
Image: Tower clock from around 1530 in the tower clock room
With a pendulum clock, the weight would have to be shifted up (faster) or down (slower).
Clocks with consistent time display are easier to build and become popular over time. Since astronomers could determine the solar peak to the nearest second, this was determined to be "12 noon."
Graphic: Dial of a wall sundial - temporal hours in black, equinoctial hours in red.
On November 24, 1793, the French introduced decimal time with the revolutionary calendar. The day was divided into 10 hours, an hour into 100 minutes and the minute into 100 seconds. This not only results in hours of equal length, but also the statements "5 a.m. noon" and "10 a.m. midnight".
Image: French decimal pocket watch
Decimal time was hardly accepted by the population. From 1796 onwards it played practically no role.
In order to avoid misunderstandings, 24-hour counting was introduced in many countries - at least for railways and public companies. This happened in Germany in 1927. Railway clocks usually show a double number ring on the dial, but there are also 24-hour clocks.
Image: 24-hour clock at Greenwich Observatory
