Hi, I'm Craig. Much like the show 24, this video takes place in real time over a period of less than three minutes, and this is Mental Floss video. Today I'm gonna answer freedom fanboys big question, "Why are there 24 hours? Why not 25? Or 100?" Let's get started.

The Egyptians usually get credit for the 24 hours in a day system, but they're probably inspired by the ancient Sumerians before them, and the number 24 actually has to do with the fact that the day's got split into three parts, a 10-hour day, two hours for twilight, and a 12-hour night.

There's evidence that Egyptians used sundials, so they were probably the first ones to efficiently measure the day. They probably did this for agricultural reasons. The earliest sundials were just made of a stake in the ground so they could note the shadow. By around 3,000 BCE, Egyptians use 10 as a base number for a lot of things, like the number of days in their weeks.

There are 36 and a half weeks in the Egyptian calendar, so they chose 36 stars called decans to represent each weeks. These 36  stars were evenly distributed in the night sky, so on a summer night 12 rose above the horizon at more or less equal intervals, with each star representing a start of a new hour. Or it's possible that 12 was used because it correspond with the number of lunar cycles in a
year. Or maybe the number of unicycles in a year I don't know, were there unicycles in ancient Egypt?

By around 1500 BCE they had created a sundial with a t-shaped bar in the middle. It was adjusted into twelve parts but confusingly because the lengths of the days vary, the lengths of the 12 hours were also different throughout the year. They also created an annual calendar based on the movement of the stars around 2500 BCE. Time is hard guys.

Eventually a Greek astronomer named Hipparchus proposed a clock that was more similar to what we use today. He used the equinoxes to measure out 12 hours of sunlight and12 hours of darkness. This made both the hourly clock in the annual calendar a little more rigid. And in case you're wondering why there's 60 minutes in an hour and 60 seconds in a minute, well I'm happy to answer because it allows me to say the word sexagesimal, which actually gets attributed to the ancient Babylonians, as opposed to a 12 or 10 based system they actually use a sexagesimal one, which means
60. It doesn't mean anything dirty, grow up. It probably inspired the Greeks, like Hipparchus 

Thanks for watching Mental Floss video which is made with the help of all these and they sexagesimals. If you have a big question of
your own that you'd like answered leave it below in the comments. See you next time.