Who decided that the day should be divided into groups of 12 or 24?

Question

Many cultures who had little to no contact with each other (Egypt, Sumeria, India, China and Native America) came up with the same way to divide time (12 hours from sunrise to sunset, 24 from sunrise to sunrise). Why did different cultures come up with different calendars, but end up dividing the day the same way?

Answer 1

First, the 12-hour division is the most basic. The 24-hour division is simply an extension of that system to make daytime and nighttime match. (In fact, many cultures that counted '12 hours' did NOT extend it to a 24-hour Thus the Romans divided the daytime into 12 hours, but the nighttime into four watches".)

The 12-part system is sometimes attributed to BOTH Egyptians and Mesopotamians, but in fact, it is clear that the mathematical system involved came from Mesopotamia and was borrowed (in part) by Egypt. It was "Babylonian mathematics" -- which begins with the ancient Sumerians (4th millenium BC) and was refined by the Babylonians, and was quite advanced -- that gave us the 12-fold division. The Egyptians' own system was decimal, and much more primitive.
http://www.uh.edu/~lpinsky/1305-1.htm

Incidentally, if you're wondering how Egyptians borrowed from Mesopotamia, there was a fair amount of contact between the two. In fact, in the mid second millenium B.C., the language and writing system of the Babylonians was THE international language -- even the Egyptians used it to correspond with, for example, their vassals in Palestine. Other ancient contacts between civilizations, e.g., between China and India, and between India and Mesopotamia, may also have played a role in things these cultures shared... though the earliest clear development of the mathematical and astronomical system involved here, was in Mesopotamia.

Why TWELVE?
This has two roots
1) It fits in with the sexigesimal system (based on 60) used by the Sumerians and developed by the Babylonians. In such a system 6 and 12 already figure prominently. So why 60? Probably because it WORKS so well -- it has many divisors (2, 3, 4, 5, 6, 10, 12, 15, 20, and 30), making calculations easier. Whatever practical or religious factors entered in, the fact that it worked probably settled them on it.

Note also that the division of hours into 60 minutes, and minutes into 60 seconds is due to the system... our homage to the ancient Sumerians.

http://en.wikipedia.org/wiki/Babylonians#Mathematics
http://en.wikipedia.org/wiki/Babylonian_mathematics

2) Astronomy/astrology & the Calendar -- there are, of course, roughly 12 months in the year... Purely lunar calendars leave it at that; the Babylonians and surrounding cultures combined that with a solar year (following the seasons) to devise a "lunisolar calendar" (by periodically adding an extra 'leap month'). Of course, civilizations (like the Babylonians) who studied astonomy (and astrology -- the two were hardly separated) noted the shifting in the stars through the year. From this, and corresponding with the 12 moons/months, they developed a ZODIAC system.

Since different cultures in the world had to deal with the same basic pattern of new and full moons and changes in the night sky through the year, it is hardly suprising if others made a similar connection and division. (In other words, if the Mayans did such a thing, it was likely based on the lunar and star cycles.) But it is the Babylonian/Mesopotamian system that formed the basis for the international system of today.
http://en.wikipedia.org/wiki/Lunisolar_calendar

Answer 2

An Egyptian shadow clock or sundial, possibly the first portable timepiece, came into use around 1500 BCE. This device divided a sunlit day into 10 parts plus two "twilight hours" in the morning and evening. When the long stem with 5 variably spaced marks was oriented east and west in the morning, an elevated crossbar on the east end cast a moving shadow over the marks. At noon, the device was turned in the opposite direction to measure the afternoon "hours."

Answer 3

The hour was originally defined in ancient civilizations (including those of Egypt, Sumeria, India and China) as either one twelfth of the time between sunrise and sunset or one twenty-fourth of a full day. In either case the division reflected the widespread use of a duodecimal numbering system. The importance of 12 has been attributed to the number of lunar cycles in a year, and also to the fact that humans have 12 finger bones (phalanges) on one hand (3 on each of 4 fingers). (It is possible to count to 12 with your thumb touching each finger bone in turn.) There is also a widespread tendency to make analogies among sets of data (12 months, 12 zodiacal signs, 12 hours, a dozen).

The Ancient Egyptian civilization is usually credited with establishing the division of the night into 12 parts, although there were many variations over the centuries. Astronomers in the Middle Kingdom (9th and 10th Dynasties) observed a set of 36 decan stars throughout the year. These star tables have been found on the lids of coffins of the period. The heliacal rising of the next decan star marked the start of a new civil week, which was then 10 days. The period from sunset to sunrise was marked by 18 decan stars. Three of these were assigned to each of the two twilight periods, so the period of total darkness was marked by the remaining 12 decan stars, resulting in the 12 divisions of the night. The time between the appearance of each of these decan stars over the horizon during the night would have been about 40 modern minutes. During the New Kingdom, the system was simplified, using a set of 24 stars, 12 of which marked the passage of the night.

Earlier definitions of the hour varied within these parameters:

One twelfth of the time from sunrise to sunset. As a consequence, hours on summer days were longer than on winter days, their length varying with latitude and even, to a small extent, with the local weather (since it affects the atmosphere's index of refraction). For this reason, these hours are sometimes called temporal, seasona, or unequal hours. Romans and Greeks used this definition; so did the ancient Chinese and Japanese. The Romans and Greeks also divided the night into three or four night watches, but later the night (the time between sunset and sunrise) was also divided into twelve hours. When, in post-classical times, a clock showed these hours, its period had to be changed every morning and evening (for example by changing the length of its pendulum), or it had to keep to the position of the Sun on the ecliptic (see Prague Astronomical Clock).
One twenty-fourth of the apparent solar day (between one noon and the next, or between one sunset and the next). As a consequence hours varied a little, as the length of an apparent solar day varies throughout the year. When a clock showed these hours it had to be adjusted a few times in a month. These hours were sometimes referred to as equal or equinoctial hours.
One twenty-fourth of the mean solar day. See mean sun for more information on the difference to the apparent solar day. When an accurate clock showed these hours it virtually never had to be adjusted. However, as the Earth's rotation slows down, this definition has been abandoned. See UTC.

Answer 4

The Mesoptamians (Sumerians, Assyrians, Babylonians) divided the circle into 360 degrees, then into 60 minutes for one hour, and then 60 seconds in one minute. They also divided the day into 24 hours and the week into 7 days (due to their discovery of seven planets).

Answer 5

OProbable explenation would be that they all come from a same source. Same as the unexplained maps that had antartica drawn out how it looks from underneath the ice sheet.. HOW WAS THAT POSSBLE? Antartica has been covered with ice apparently for over 10 000 years... Te Mayan callendar is te most precise one in the univers which refers even to the alignment of the plantes, and their books repeatedly as well as hte egyptian ones, the bible, the chinese, the quaran, and the rest.. ..mention visitors from the skies.... the heavenly decendants.. I am not making this up, it is all true.
Even the CHristmas island statues are looking up towards the skies...... THe pyramid consistenyl refers to the positions of the stars.... it is all found on Mars as well.. same shapes.. with same distances and measurements...

Conclusion... it is a source which dates back many millenia to a civilization that spawned before us... a more advanced civilization...

Answer 6

I don't know but it is fascinating that happened. I guess it is one of the wonders like the story of Noah's Ark where different cultures tell the same story as the one that is in the Old Testament

Answer 7

its the same thing with the greatest idea since sliced bread, I just wondered what was the best idea before that.

Answer 8

A dozen or two people

Answer 9

what about 60 seconds? It's a conspiracy I tell you...maybe Aliens!!