Why is the Day 24 Hours?

The only reason a day 24 hours in it is that man has decided he would like to work pout time that way. Nothing occurs in nature or in the world that has anything to do with hours or minutes or seconds. These divisions of time were made up by man for his convenience. But something does happen that has to do with what we call a "day".

And that something is the rotation of the earth on its axis from west to east. Every time it goes around once, a specific amount of time has passed. We call that time a "day". Scientists can measure that time exactly and they use the star to do it. Observatories have what are called "sidereal" clocks.

A sidereal day begins the instant that a given star crosses a meridian and last until the instant that it recrosses the same meridian. Since man has broken up the day into hours, minutes, and seconds, we can say how long a sidereal day is. It is 23 hours 56 minutes and 409 seconds long, which means that there are 366 sidereal days in a year.

Hence we have a leap year every fourth year where there is one extra day, to make. To early people, a day meant simply the space between sunrise and sunset. The hours at night were not counted. The Greek counted they day from sunset to sunset. For the Romans, it was from midnight to midnight. Before clocks were invented, day and night were divided into 12 hours each.

This division was not practical as the length of the two periods differs with the seasons. Today, most countries have a day which, by law, extend  over the 24-hours period from midnight to midnight, following the Roman method.

Post a Comment