ultrafilter: It’s important to note that the ancients probably had no idea that planets were unlike stars.
Not quite true. They certainly had no way of knowing what planets were actually made of via spectroscopy or anything like that, but the classical cosmological models certainly considered planets (including the sun and moon) to be different from stars. The stars were considered to be much farther away and to be located on a single outermost sphere (stellar parallax and proper motion weren’t known at the time). The planets were bigger to the naked eye (sun and moon certainly, but even the five star-planets look somewhat different from stars because they’re not far enough away to be point sources of light).
I believe Aristotle considered, though, that all celestial objects (moon on outwards) were made of a different substance than the four elements of Earth, Air, Fire, and Water that composed the “sublunar” world in variously proportioned mixtures. The more perfect celestial objects were a fifth element or “quintessence”.
LM: There’s a Hermetic text (generally called The Discourse on the Eight and Ninth,) found at Nag Hammadi, which contains a certain amount of astrological/astronomical metaphor, and refers to a hidden “eight and ninth” beyond the revealed seven.
Could be (and probably is) just meaning to imply celestial orbs or spherical shells that were part of the standard geocentric cosmology, not additional planets. I think the eighth orb was generally that of the fixed stars and the ninth that of the Unmoved Mover or some such Neoplatonic concept.
Odion: I once read that the morning star aspect of Mercury was called Apollo before they figured out it was the same planet.
I never heard that, but it’s true that some classical sources refer to earlier authorities as having thought that the evening and morning appearances of the same inferior planet (usually Venus, not Mercury) were actually different objects. This was kind of a dig by the classical Greeks at their more backwards ancestors who hadn’t figured out periodic planetary motions yet.
CM: Exactly why seven is seen as a mystical number isn’t extremely obvious. Odd numbers definitely seem to have mystic significance […] By why should we have a week of seven days? Because the period of the moon is 29 days and change, and 28 is close to that, and is easily divisible by two and four. Divide by two and you getr fourteen day periods (a fortnight). Divide by four and you get seven – the week. (I suppose you could round up instead and get three ten day “weeks” in a month, but I never heard of anyone trying that experiment.)
They certainly did:
The linked site is almost certainly incorrect, though, in stating that the seven-day week came from the “Assyrians”. Akkadian-using Mesopotamians, Assyrians and Babylonians alike, reckoned a 29- or 30-day lunar month but identified all its days individually, without smaller “week”-like units. As far as I’ve ever been able to find out, the seven-day week is a Hebrew invention, and may indeed have come about exactly as Cal hypothesizes.
Cal’s also right that the mystic nature of seven is probably more closely related to this weird-odd-indivisible number phenomenon than to any notion of the planets. Note also that seven is the first “does not divide” number in Mesopotamian base-sixty mathematics, dating back at least into the third millennium BCE; division was performed by multiplying by the number’s base-60 reciprocal (3 = 60 x 0;20, 4 = 60 x 0;15, and so on). Mesopotamian division tables (still preserved on a lot of cuneiform clay tablets) looked something like this:
1 60
2 30
3 20
4 15
5 12
6 10
7 does not divide
8 7 30
9 6 20
10 6
11 does not divide
And so on. The numbers that didn’t have finite base-60 reciprocals—that “didn’t divide” 60—were definitely perceived as kinda weird and special mathematically. How much that influenced their mystic aura, however, I don’t know.
