Whose idea was it to have 12 signs in the zodiac, 12 months of 30 days each, 360 degrees in the circle?

Answer 1

The Origin of the Zodiac

The myth of a prehistoric 12-constellation zodiac (of equal divisions) is not yet extinguished. The suggestion that the zodiac was originally established as an intended scheme of 12 constellations and 12 equal divisions some 6000 years ago (or even earlier) is untenable. The fact that these ideas have been effectively disposed of seems to be ignored in publications addressed to the jury and not the bench. There is no evidence that the Greek scheme of 12 zodiacal constellations existed anywhere prior to its evolvement in Greece circa 500 BCE. The Assyriologist Peter Jensen was the first to show, in his book Die Kosmologie der Babylonier (1890), that the Greek zodiac (and zodiacal constellation names) was adapted (with few changes) from the (newly developed) zodiacal scheme of the Babylonians.

The tide of claims up to the early 20th-century for the great antiquity of the zodiac (made by many historians, astronomers and Assyriologists) have been definitively discredited by an understanding of relevant Mesopotamian cuneiform sources. (Nineteenth-century arguments made frequent (misplaced) use of mythology and symbolism i.e., Recherches sur le culte public et les mystères de Mithra en Orient et en Occident by (the French archaeologist) Félix Lajard (1867).) The pioneering work on Babylonian astronomy was the monumental Sternkunde und Sterndienst in Babel (1907-1935, 2 volumes and 3 supplements in 7 parts) by the Jesuit mathematician and Assyriologist Franz Kugler. (The idea that a 12-constellation equally divided Babylonian zodiac originated circa 6000 BCE (enthusiastically promoted by the Panbabylonists Fritz Hommel (Semiticist) and Alfred Jeremias (Archaeologist)) did not begin to be entirely discarded until the pioneering work of Franz Kugler began appearing. In his article "Orientation" (Antiquity, Volume 1, 1927, Pages 31-41) Vice-Admiral Boyle Somerville incorrectly held that the zodiac was known in Mesopotamia as early as 5000 BCE.) The later studies of the mathematicians Otto Neugebauer and Bartel van der Waerden on cuneiform astronomy have clearly shown that the zodiac originated in Mesopotamia and not earlier than the 1st millennium BCE.

The three major stages in the development of the zodiac were: (1) the establishment of 12 unequal constellations along the ecliptic, (2) the division of the ecliptic into 12 equal segments based on the 12 constellations, and (3) the division of the 12 equal segments into 12 equal tropical signs.

The zodiac we have inherited is from the Greeks. There is no solid evidence that the Greeks possessed a complete zodiac until the 5th-century BCE. (We know the Greek zodiac was formalised by the latter half of the 5th-century BCE because the two Greek astronomers Meton and Euctemon both used it in their parapegmata (i.e., star calendars based on a division of the year into zodiacal signs). Its purpose lay with the establishment of the solar calendar.) The evidence is clear that the Greek introduction of such was that of a scheme borrowed from the Babylonians - excepting Aries and Libra. (The route of diffusion of astronomical knowledge from Mesopotamia to Greece is not known but during the 6th-century BCE the Babylonians and Ionian Greeks were subjects of a unified Persian Empire.)

The Greeks borrowed and established the zodiacal scheme circa late 6th-century BCE. This act by the Greeks (and Eudoxus' two works on constellations) became the basis for their development of a formal Greek sphaera. (Also, there is no conclusive evidence that the obliquity of the ecliptic was known to the Babylonians before the Greeks became aware of such.) Some Greek constellations were established by at least circa 800-750 BCE. Homer circa 750 BCE in his epic poems the Iliad and Odyssey mentions six constellations and the star Sirius. Hesiod's later poem Works and Days shows that by circa 700 BCE the Greeks had established a cyclical calendar, and an astronomy connected with meteorology and botany (which included observations of the rising and setting points of stars). Hesiod names almost the same constellations as Homer.

The Greeks changed the Babylonian zodiacal constellation "Hired Man" into Aries and the Romans later reintroduced the Babylonian zodiacal constellation Libra. The evidence also indicates that the Babylonian constellations which were to form the final zodiacal 12, though established over time, were formulated into a zodiacal scheme of 12 at the same time and place - Babylonia circa 7th-century BCE.

The formal scheme of Babylonian constellations was established early in the 2nd millennium BCE to mark 3 equatorially-centred stellar paths. These were the Paths of Anu, Enlil, and Ea. (It is doubtful that the Babylonians of the 2nd millennium actually identified the celestial equator.) The dual purpose of the constellation scheme was calendrical and also to serve as sky markers. It was unrelated to the ecliptic (and to the zodiac which was not yet developed). Despite popular assertions to the contrary there is no mention of the zodiacal scheme in Babylonia, or elsewhere in the Occident, prior to the 1st millennium BCE.

Some constellations that later formed part of the zodiac were established in Mesopotamia circa 2000 BCE or perhaps earlier, and some were perhaps originally used as seasonal markers. (The expression "Stars of Elam, Akkad, and Amurru" perhaps suggests that, even very early, at least in Mesopotamia, the constellations originated as independent formal schemes having a calendrical purpose.) However, in the early 2nd millennium BCE these constellations formed part of the Babylonian system of "three stars each" i.e., the Paths of Anu, Enlil, and Ea. (There is some ambiguous evidence of earlier Sumerian constellations. It is reasonable to hold that perhaps the Sumerians originated certain constellations and perhaps they had a formal scheme for such.)

A significant change occurred (during the Assyrian Period) circa 1000 BCE with the astronomy of the Mul.Apin series. The astronomy of the Mul.Apin series established the preconditions for the establishment of the zodiac.

Mul.Apin tablet 1 describes the Path of Sin (= the way of the Moon) which crossed the boundaries between the Paths of Anu, Enlil, and Ea. This referred to 17/18 constellations/stars marking the path of the Moon ("gods standing on the path of the moon."). [See: Note 1 below.] It was a fixed path in the sky. (When the ecliptic started to become a primary reference line the 17/18 (depending on how you interpret the list) constellations/stars marking the path of the Moon were basically formed out of the "three stars each" (i.e., monthly calendar star) system of menologies and other constellations/stars were added.)

Mul.Apin tablet 2 describes the Path of Shamash (= the way of the Sun) which also crossed the boundaries between the Paths of Anu, Enlil, and Ea. The path of the Sun and Planets was identified with the Moon's path. Likewise, it was a fixed path in the sky.

The second Mul.Apin tablet shows that the solar year was divided into a scheme of 12 solar months during which the sun occupied different parts of the sky. It set out: From month 12, day 1, to month 2, day 30, the sun is in the Path of Anu. From month 3, day 1, to month 5, day 30, the sun is in the Path of Enlil. From month 6, day 1, to month 8, day 30, the sun is in the Path of Anu. From month 9, day 1, to month 11, day 30, the sun is in the Path of Ea. (Hence the obliquity of the path of the sun was known to the scribes of the Mul.Apin texts at least circa 700 BCE.) In the Mul.Apin scheme the year was thus divided into 4 astronomical seasons corresponding to the 4-fold division of the ecliptic. Each of these 4 seasons was further divided into 3 solar months.

Prior to the Mul.Apin system of 17/18 constellations/stars (circa 1000 BCE earliest) the ecliptic was not specifically marked (or identified) in Babylonian astronomy. (Not all the 17/18 constellations/stars that were used to mark the path of the Moon were within the ecliptic.) Earlier than circa 1000 BCE there was, in Babylonian astronomy, no intentional system of marking the path of the ecliptic. (However, the Sumerians circa 3rd millennium BCE would seem to have had a formal scheme of "lunar houses.") In the early Babylonian scheme the constellations marking the the approximate "equatorial" pathway of Anu comprised an "equatorial" "zodiac." (It is certain the the Babylonians had no formal concept of the clestial equator.)

The zodiac was a development from the Babylonian scheme of 17/18 constellations/stars marking the path of the moon. The Babylonian system of 17/18 constellations/stars zodiac marking the path of the Moon belongs to the Assyrian Period (and perhaps originated circa 1000 BCE) and was still in use in the 7th-century BCE and contained the constellations that were to form the 12-constellation solar zodiac. At least 5 of these 17/18 constellations/stars are not previously listed but are additional constellations/named stars in the Mul.Apin series.

Post Mul.Apin (i.e., toward the Neo-Babylonian Period) the number of constellations/stars in the Path(s) of Sin/Shamash was limited from 17/18 to 12. Circa 700 BCE a "zodiac" comprising of 12 irregular sized constellations had been developed. Only those 12 constellations/stars nearest to the path of the ecliptic were used. The other 5/6 were discarded as ecliptic markers.

A Babylonian text from circa the 5th-century BCE which lists 12 months (and ignores the intercalary month) and their associated constellations, also assigns both the Pleiades and Taurus to month 2, both Orion and Gemini to month 3, and both Pegasus and Pisces to month 12. This provides an indication of another of the progressive steps towards an eventual zodiac of 12 equal 30 degree divisions and signs.

The issue of reducing from 17/18 constellations/stars as marker's along the Moon's path was connected with the establishment of 12 (ideal) solar months of 30 days each. (The fact that certain stars had become connected with the schematic year of 12 months x 30 days each greatly assisted the development of the reduction of the zodiac to 12 divisions. The calendar was schematic because of the fact that the year does not consist of exactly 360 days. This made it necessary to add an extra 13th month now and then. The periodic intercalation of a 13th lunar month was done to keep the lunar calendar in line with the seasons. It was not based on solar observations.) (This theoretical division of the year into 12 months of 30 days each is indicated as dating back to the Old Babylonian Period circa 1800 BCE.) Hence the system of 12 zodiacal constellations was invented mostly from existing constellations/named stars that originated largely during the 2nd millennium BCE for marking a different i.e., (roughly approximating an) "equatorially-centred", sky system. (The Babylonians had no actual recognition of a celestial equator.) The 12-constellation zodiac replaced the earlier 17/18 constellation/star scheme that it developed from.

Whilst there is relatively clear evidence that perhaps 8 of our 12 present zodiacal constellations existed in the 2nd millennium BCE there were at least 4 constellations - that were to form part of the zodiacal scheme - that most probably did not exist until the 1st millennium BCE. There is no unambiguous evidence that all of our present 12 constellations comprising the zodiac existed prior to the Late Assyrian Period.

Circa the 5th-century BCE the Babylonian skywatchers needed a suitable frame of reference to indicate the positions of the Moon and the planets between the stars along the path of the ecliptic. With the demands of their developing astronomy it was no longer sufficient to continue with a scheme that simply noted that the Moon or a planet was close to this or that star.

Circa 420 BCE the Babylonians substituted the original 12 constellations forming the zodiacal scheme with a sidereal scheme of twelve equal divisions of the ecliptic comprising 30º segments. This followed the Babylonian invention of degrees, which was introduced into mathematical astronomy to enable the measuring of celestial "longitude" from a given point (which was the vernal equinox). (A schematic month was comprised of 30 days and therefore each zodiacal segment or "sign" numbered 30°.) The zodiac of 12 equal signs was never used by the Babylonians as a coordinate system. It was only used as a mathematical abstraction for computing lunar and planetary motion. (The Normal Stars, a set of approximately 30 stars positioned around the ecliptic, continued to be used by the Babylonians for locating the positions of the moon and planets. About the middle of the 3rd-century BCE the zodiacal reference system seems to have finally become established as the norm for such.) Also, the Babylonians always simply defined the starting points of the scheme of zodiacal signs by their positions relative to the fixed stars. Hamal, the brightest star of the Ram (= Babylonian MUL.LU.HUN.GA ("Hired Man") was probably used to mark the vernal equinox. However, the completed zodiacal system of the Babylonians, for reasons still incompletely known, did not start at 0º ecliptic longitude but at about 355º, and this difference extends through the whole zodiac.

The Greeks located the beginnings of the zodiacal signs differently. In the changeover from the Babylonian zodiacal system to the Greek zodiacal system the abandonment of the earlier version of the zodiac measured from the fixed stars occurred.

It would appear it was the Greek astronomer Hipparchus of Rhodes (2nd-century BCE) who first redefined the the boundaries of the 12 signs so that the vernal equinox was placed at the beginning of the (Greek) sign of Aries. This now became the starting point for the zodiacal division of 12 equal signs. This system of Hipparchus, with the "first point of the sign Aries" fixed to vernal equinox, replaced the zodiacal scheme of visible constellations. The astronomer Claudius Ptolemy, in the 2nd-century CE, consolidated this system to get rid of the inconvenience of precessional movement and attendant confusion (regarding the "mismatched" sidereal zodiac and tropical zodiac).

In summary: The 12-constellation zodiac arose during the Late Assyrian Period (the Assyrian Period began circa 1100 BCE) from a deliberate scheme which circa 1000 BCE placed 17/18 constellations/named stars (comprising of 12 existing constellations/stars previously used in marking the equatorially-centred system of the "three stars each," and 6 "new" constellations) for use as reference points along the path of the Moon. The development of the 12-constellation zodiac into 12 equal divisions (i.e., 30 degree signs) occurred later during the 5th-century BCE (for mathematical reasons). In its final form the use of the zodiac also included marking the movements of the planets.

After the Babylonians invented the 12-constellation zodiac they did not immediately regard it as especially important. However, they discarded the old reference system of the "three ways each." (With their establishment of the 12-constellation zodiac the Babylonians became the first to use the ecliptic as the primary celestial reference point.)

Answer 2

I think the 360 degree thing was Babylonian. The other stuff was Egyptian. Egypt is in Africa, but I can't think of any other link to African-Americans besides that. I mean, the zodiac is an ancient idea and nobody came up with it over here--it's an old-world concept and people would have known about it in ancient Mesopotamia, Asia, Europe, Africa...I'm not aware that groups here had the same idea. For instance, the Mayan calendar has 20 signs in the zodiac (I think--I know it's more than 12.) They were American, but they didn't follow the 12-pattern. Zodiac is a Greek term. Month is an Anglo-Saxon term. I'm not sure what you're getting at, but other than the Egyptian link (and I don't think the Egyptians came up with the zodiac themselves--I think they got it from the Middle East), I don't know how it's African-American.