Why Are There 24 Hours in a Day?

After class today, I was curious as to why there are twenty-four hours in a day.  After learning about the 23.5 degree angle of the earth, I wondered if there was a connection between this 23 1/2 and the 24 hours.  While they are not connected, the reason for our 24 hours is very interesting.  This website explains it in a very accessible way:

Why the 24 Hour Days?

Turns out that we can blame the Egyptians (or more accurately, the Sumerians!).  The website explains their use of the 24 hour day as thus:

• The Egyptians used the Sumerian counting system of 12.  Sumerians counted using the tip of their left thumb.  They counted all three knuckles on the four fingers (hence the 12).

• Another explanation for the 24-hour day has to do with decan stars.  A decan star was "a star which rose just before sunrise at the beginning of a 10-day "decade" in Ancient Egypt. 36 "decan" stars marked the passage of a year for the Egyptians (or 36 10 day periods). During summer nights, 12 decan stars rose - one for each "hour"." 

• Hours did not have a fixed time "until the Greeks decided they needed such a system for theoretical calculations. Hipparchus proposed dividing the day equally into 24 hours which came to be known as equinoctial hours (because they are based on 12 hours of daylight and 12 hours of darkness on the days of the Equinoxes). Ordinary people continued to use the seasonally varying hours for a long time. Only with the advent of mechanical clocks in Europe in the 14th Century, did the system we use today become common place."