How many hours are there in a day? Everyone knows this - 24 hours. But why did it happen? Let's take a closer look at the history of the appearance of the main units of time measurement and find out what a day is, how many hours, seconds and minutes are in a day. And also let's see if it is worth tying these units exclusively to astronomical phenomena.
Where did the clock come from? This is the time of one rotation of the earth around its axis. Knowing little about astronomy yet, people began to measure time in such ranges, including every light and dark time.
But there is an interesting feature here. When does the day start? From a modern point of view, everything is obvious - the day begins at midnight. People of ancient civilizations thought otherwise. It is enough to look at the very beginning of the Bible to read in the 1st book of Genesis: "… and there was evening, and there was morning, one day." The day began at sunset. There is a certain logic in this. The people of that time were guided by daylight hours. The sun has set, the day is over. Evening and night is alreadynext day.
But how many hours are there in a day? Why was the day divided into 24 hours, because the decimal system is more convenient, and much more? If there were, say, 10 hours in a day, and 100 minutes in each hour, would something change for us? Actually, nothing but numbers, on the contrary, it would even be more convenient to make calculations. But the decimal system is far from the only one used in the world.
In ancient Babylon they used the sexagesimal counting system. And the bright half of the day was well divided in half, for 6 hours each. In total, there were 24 hours in a day. This rather convenient division was taken from the Babylonians and other peoples.
The ancient Romans counting time was even more interesting. The countdown started at 6 am. So they counted further from this moment - the first hour, the third hour. Thus, it can be easily calculated that the "eleventh hour workers" commemorated by Christ are those who start work at five o'clock in the evening. Really too late!
At six o'clock in the evening the twelfth hour came. That's how many hours in a day were counted in ancient Rome. But it was still night time! The Romans did not forget about them either. After the twelfth hour, the night watch began. The attendants changed at night every 3 hours. Evening and night time was divided into 4 guards. The first evening watch began at 6 pm and lasted until 9. The second, midnight watch, lasted from 9 to 12 o'clock. The third watch, from 12 at night to 3 in the morning, ended when the roosters sang, which is why it was called “rooster crow”. Last,the fourth watch was called "morning" and ended at 6 in the morning. And it all started again.
The need to divide watches into component parts also arose much later, but they did not retreat from the sexagesimal system even then. And then the minute was divided into seconds. True, later it turned out that it was impossible to rely only on astronomical observations to determine the duration of seconds and days. For a century, the length of the day increases by 0.0023 seconds - it seems to be very little, but enough to get confused about how many seconds are in a day. And that's not all the difficulties! Our Earth does not make one revolution around the Sun in an even number of days, and this also affects the solution of the question of how many hours are in a day.
Therefore, to simplify the situation, the second was equated not to the movement of celestial bodies, but to the time of the processes inside the cesium-133 atom at rest. And to match the actual state of affairs with the revolution of the Earth around the Sun twice a year - December 31 and June 30 - add 2 extra leap seconds, and every 4 years - an extra day.
Total it turns out that there are 24 hours in a day, or 1440 minutes, or 86400 seconds.
