- I know that there are 60 minutes in an hour, but is that just an arbitrary number?
- Are latitude and longitude related to a 24-hour period in terms of distance and time? And why???
- Why are there 360 degrees in a circle…is that based on something?
Also see: more questions.
- I'll try to summarize it as accurately as I can [remember]. Longitude is based on the distance the earth rotates in one hour. It was constructed that way for navigation purposes. A sailor at sea could always know where he was if he knew two things: the position of the pole star and the time of day. Knowing those two things he could consult a book that would list at what time the pole star would be in that position over Greenwich, England. All he had do then was figure out how many hours (lines of longitude) he was from Greenwich, and he would have his position on the globe. The problem for years was how to keep accurate time aboard ship, a problem that was eventually solved by the spring driven clock.
- The polar stars -- the North Star and the Southern Cross --were used to measure degrees of latitude (how far north or south you were from the Equator). The pole stars would not help marking longitude. The North Star would be at the same declination in a given month whether you were at Greenwich, England or the southern tip of Hudson Bay. You mentioned the spring driven clock. That was the only way to compute how many degrees of longitude you had sailed west or east from Greenwich, the Prime Meridian. The first such clock was built by John Harrison around 1760. That may be the connection between degrees of longitude and minutes of hours.
I recommend reading Longitude, by Dava Sobel.
- Astronomers in early civilizations in Mesopotamia knew that the solar year is not 360 days. 360 days would certainly be a much more convenient length year than is 365.25.... however, according to the article "Calendar" in my Britannica (1963 edition - for things historical I prefer older editions) (v.4, p.622-623)- they used a 12 month, 354 day, "lunar" year, and eventually (ca. 9th c. B.C.) realized that it could be adjusted to the solar year by adding (intercalating) seven extra lunar months every 19 years. Other changes were also made to more closely synchronize the solar and lunar calendars.
So, briefly, the Babylonians (who gave us base 60 for time-keeping) did not have a 360-day year. Neither did the Greeks, and these were the major "mathematical powers" of the ancient western world. The article on "Fractions" (v.9, p.576) really explains it. As I am not sure whether this is still in current editions, I'll quote the significant part: "When they decided to take 120 units as the length of the diameter of their standard circle (probably because its numerous factors, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 40 and 60, made the representation of fractions easy), the circle (using the old value 3 for Pi) became 360 units."
Then, as we know, they divided each degree into 60 units (our minutes), and each "minute" into 60 units (our seconds). Yes, the modern divisions of the earth are directly traceable to this. The only real connection between these and the divisions of the day is the penchant of the Babylonians to subdivide units by 60.
