Moon
The Moon is the fastest-moving of the seven traditional planets by a wide margin, covering roughly 13 degrees of ecliptic longitude a day against the Sun’s own one degree. Its sidereal period, the time to return to the same point against the stars, is about 27.3 days; its synodic period, the time from new moon to new moon, is about 29.5 days, the difference arising because the Sun has itself moved on in the meantime. At that speed the Moon changes tropical sign roughly every two to three days.
That speed has a direct consequence for how sensitive the Moon is to error in the birth record, and it is a different consequence from the one usually raised about a birth chart. The ascendant’s sensitivity to birth time is a matter of minutes, changing sign roughly every two hours; the Moon’s is a matter of the calendar date itself. A birth misdated by a single day, of the kind a time zone conversion or a date-line crossing can silently produce, has a real chance of placing the Moon in the wrong sign entirely, in a way a same-size error almost never does to the Sun, which takes about a month to cross one sign. The Moon is the body a wrong day is most likely to get wrong.
The names
The Greek name is Selene, and, as with the Sun, there is no separate descriptive epithet on record standing before it the way Phainon stands before Kronos for Saturn 1. The Latin name is Luna.
In Akkadian the Moon-god is Sîn, also called Nanna in Sumerian 1. No transparent common-noun meaning for Sîn has been found in the sources checked for this entry. That is the unusual case: the neighbouring entry for Saturn carries Kayamanu, “the steady one,” an Akkadian name whose descriptive sense is plain. Sîn appears instead to be a proper theonym without a transparent gloss behind it, at least on what has been consulted here.
Dignities
| Domicile | Cancer |
|---|---|
| Detriment | Capricorn |
| Exaltation | Taurus, at 3 degrees |
| Fall | Scorpio, at 3 degrees |
| Triplicity | Earth (by night); Water (participating) |
| Bounds held (Egyptian) | none |
The Moon rules Cancer alone, the counterpart to the Sun’s sole rule of Leo, and like the Sun it takes no bounds: the Egyptian bound scheme is built from the five non-luminaries only, so neither luminary appears in it by the scheme’s own construction. The Moon is exalted in Taurus and falls in the opposite sign, Scorpio. Unlike the Sun, which rules one triplicity by day, the Moon holds two separate triplicity roles: night ruler of Earth and participating ruler of Water, a doubling none of the other six planets repeats in quite that combination. The full apparatus, including the three readings of the water triplicity in which the Moon’s own role differs, is set out at Essential Dignity.
Sect
The Moon is a nocturnal planet, and in a chart of the night it is the sect light, the counterpart role to the Sun’s by day. See Sect for the division of all seven planets into the two teams and for how Mercury is assigned separately from the rest.
Tradition
Held byClaudius Ptolemy, Tetrabiblos bk. I ch. 4, Alexandria, c. 150 CE
Ptolemy derives the Moon’s quality from its nearness to the earth and to the moisture he holds rises from it, giving it a predominantly humidifying power with a lesser heating power borrowed from the sunlight it reflects: “Most of the moon’s power consists of humidifying, clearly because it is close to the earth and because of the moist exhalations therefrom. Its action therefore is precisely this, to soften and cause putrefaction in bodies for the most part, but it shares moderately also in heating power because of the light which it receives from the sun” 2 bk. I ch. 4.
Tradition
Held byWilliam Lilly, Christian Astrology bk. I, London, London, 1647
Lilly’s chapter on the Moon follows the same working template as every other planet in his book: nature, colours, trades, bodily parts, and the kinds of person and question it is taken to govern. It is a practitioner’s reference for judging a client’s question, and Lilly treats the Moon at greater length than any planet but the Sun because so much of his working method turns on its condition at the moment a question is asked 3 bk. I.
The Moon and the constellations
Because the Moon moves so quickly, its passage against the fixed stars shows the difference between the tropical, sidereal and constellation frames more vividly than any other body’s does: in the course of one sidereal month it crosses several IAU constellations of very unequal width, entering and leaving some of them in less than a day. Three Reference Frames sets out how many constellations the ecliptic passes through and why their widths are not a fourth zodiac; the Moon is the one body whose speed makes the crossing visible on a human timescale.
Gap in the evidence
Whether the Sun and Moon ever carried a Greek descriptive epithet of their own, in the manner of Saturn’s Phainon, that has not survived in the record, or whether Helios and Selene were their only Greek names from the start, is not settled by the sources consulted for this entry. The absence noted above for Sîn is a stated gap in what has been found.
References
- Claudius Ptolemy, trans. F. E. Robbins. Tetrabiblos. Loeb Classical Library 435. Cambridge, MA: Harvard University Press, 1940 (composed c. 150 CE). bk. I ch. 4. find a copy (catalogue search) recordprimary source
The standard English reference and the chapter-numbering scheme this site adopts and names. Non-Robbins reprints number the chapters differently, so every locus here is given as Robbins numbering.
- William Lilly. Christian Astrology. London, 1647 (composed 1647). bk. I. https://archive.org/details/b30338724 recordprimary source
Second edition 1659. Where a figure differs between the two printings this site says which printing it is quoting.
- Nicholas Campion. A History of Western Astrology, Volume I: The Ancient and Classical Worlds: Continuum, 2009. ISBN 9781441127372 recordscholarly
The standard single narrative survey. Volume I first appeared as The Dawn of Astrology, Hambledon Continuum, 2008. The subtitle is "The Ancient and Classical Worlds", not "The Ancient World"; the shortened form is widely miscited.
Further reading
- NASA Goddard Space Flight Center, Scientific Visualization Studio, Ernie Wright, Noah Petro. CGI Moon Kit (Scientific Visualization Studio entry 4720), 2019.
- B. A. Archinal, C. H. Acton, M. F. A'Hearn, A. Conrad, G. J. Consolmagno, T. Duxbury, D. Hestroffer, J. L. Hilton, R. L. Kirk, S. A. Klioner, D. McCarthy, K. Meech, J. Oberst, J. Ping, P. K. Seidelmann, D. J. Tholen, P. C. Thomas, I. P. Williams. Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015, 2018.