What is Moon in Western astrology?

Definition

Moon is the only natural satellite of Earth, which in Western astrology is treated as a classical planet ruling Cancer and exalted in Taurus, with a fall in Scorpio.

In plain words

The Moon, in Western astrology, is treated as a planet that symbolizes emotion, habit, rhythm, and adaptation, and it is traditionally linked to the sign Cancer. Ptolemy's Tetrabiblos grouped it with Jupiter and Venus as beneficent, and placed it in the feminine and nocturnal classes. These are symbolic table relationships rather than claims about physical control.

Also asked as

• What does Moon represent in Western astrology?
• Which signs does Moon rule?
• How long is Moon's orbit and synodic cycle?
• How often is Moon retrograde?

History

In Ptolemy's Tetrabiblos, the Moon is grouped with Jupiter and Venus among the beneficent planets, because of their tempered nature and because they abound in the hot and the moist. Ptolemy, writing in the Tetrabiblos, presents this grouping as a classical rule of the older astrological tradition, so the Moon's place among the benefics is a historical classification rather than a physical measurement.¹

In Britannica's account, Mesopotamian celestial omens included Sin, the Moon, with omens on lunar phenomena such as first crescents, eclipses, halos, and conjunctions with fixed stars. Britannica's article on astrology treats these early omen records as some of the earliest sky-watching traditions that later shaped Western planetary practice.²

Quick timeline

1. Early record — In Ptolemy's Tetrabiblos, the Moon is grouped with Jupiter and Venus among the beneficent planets, because of their tempered nature and because they abound in the hot and the moist. Ptolemy, writing in the Tetrabiblos, presents this grouping as a classical rule of the older astrological tradition, so the Moon's place among the benefics is a historical classification rather than a physical measurement.¹
2. Classical framework — In Britannica's account, Mesopotamian celestial omens included Sin, the Moon, with omens on lunar phenomena such as first crescents, eclipses, halos, and conjunctions with fixed stars. Britannica's article on astrology treats these early omen records as some of the earliest sky-watching traditions that later shaped Western planetary practice.²
3. Later transmission — Ptolemy's Tetrabiblos holds that most of the Moon's power consists of humidifying, because it is close to the earth and because of the moist exhalations from the earth, while it shares moderately in heating power from the light it receives from the sun.¹
4. Modern usage — The Moon is the ruling planet of Cancer and is exalted in Taurus. In classical Roman mythology, the Moon was Luna, at times identified with Diana, and the Greek counterparts were Artemis and Selene.⁶

What classical and modern sources say

Classical view

Ptolemy's Tetrabiblos holds that most of the Moon's power consists of humidifying, because it is close to the earth and because of the moist exhalations from the earth, while it shares moderately in heating power from the light it receives from the sun.¹

The Moon is the ruling planet of Cancer and is exalted in Taurus. In classical Roman mythology, the Moon was Luna, at times identified with Diana, and the Greek counterparts were Artemis and Selene.⁶

The 1st-century poet Manilius described the Moon, or Luna, as melancholic, though the Moon is more commonly associated with the phlegmatic humor and was said to rule the animal spirits.⁶

Modern view

The Moon's apparent size in Earth's sky is about the same as the Sun's, which lets it completely cover the Sun during a total solar eclipse.³

In astrology, the Moon is associated with a person's intuition, emotions, unconscious habits, rhythms, memories, moods, instincts, and their ability to react and adapt to those around them.⁶

Modern astrology, as described in the Wikipedia article on planets in astrology, links the Moon with intuition, emotions, rhythms, memories and moods. Working with these traits can be treated as a constructive growth practice: a reader might keep a simple daily log of mood and rhythm, then notice patterns in how they respond and adapt to people around them.⁶

Rulership, cycles and traditional nature

Traditional rulership

In Ptolemy's Tetrabiblos, the Moon's house is Cancer, the feminine luminary's sign, which lies nearest the zenith among the twelve signs. Wikipedia's planets-in-astrology article says the Moon rules Cancer and is exalted in Taurus. Rulership and dignity are symbolic table relationships, not claims of physical control.¹⁶

Sect and nature

Ptolemy's Tetrabiblos assigns the Moon to the night sect and describes it as cold and moist, with its power consisting mostly of humidifying because it is close to the earth. These are historical symbolic classifications, not measured facts about the Moon.¹

Orbital cycle

NASA lists an orbital period of 27.3217 days and a synodic period of 29.5306 days.⁴

Physical link

The Moon is large enough for its gravity to affect the Earth, stabilizing its orbit and producing the regular ebb and flow of the tides, and the same side of the Moon always faces the Earth.⁶

The astronomy

The Moon is the only natural satellite of Earth, orbiting Earth in an elliptical path at a varying distance that averages around 378,000 kilometers.³

Tidal forces between Earth and the Moon drive Earth's tides and have caused the Moon to always face Earth with the same near side, a state called tidal locking.³

According to NASA, the Moon consists of three main layers: a crust, a mantle, and a core, with a thin outer crust and a solid core.⁴

NASA lists an orbital period of 27.322 days.⁴

Where astrologers differ

Ptolemy's Tetrabiblos classes the Moon as feminine and nocturnal, reasoning that the moist is especially feminine and that night is more feminine because of its moisture and its gift of rest. Britannica notes that Chinese astrology developed independently, and that Chinese cosmology's five elements are earth, wood, metal, fire, and water, not the Moon's traditional Western rulerships (britannica-astrology). Readers who compare traditions will find that the Western framework is one system among several, and its Moon assignments do not carry over into Chinese cosmology.

Then and now

Then

Ptolemy's Tetrabiblos holds that most of the Moon's power consists of humidifying, because it is close to the earth and because of the moist exhalations from the earth, while it shares moderately in heating power from the light it receives from the sun.¹

Now

The Moon's apparent size in Earth's sky is about the same as the Sun's, which lets it completely cover the Sun during a total solar eclipse.³

Worked out from the evidence

Reasoned from the cited facts, not stated outright by any one source.

Ptolemy's Tetrabiblos places the Moon among the beneficent planets, while Wikipedia's planets-in-astrology article links it with intuition and emotion, so the sources show that the Moon's meaning has shifted between the classical and modern traditions.

Not yet confirmed

• Whether the Moon's tidal and gravitational effects on Earth bear any measurable relation to the symbolic temperament Ptolemy assigned to it is not settled by the sources.
• How the Mesopotamian omen records about Sin relate to the later planetary rulerships of Cancer is not spelled out in the sources.

Follow the parts of Moon

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Questions people also ask

What kind of subject is Moon?

In Ptolemy's Tetrabiblos the Moon is a classical planet of Western astrology, assigned to Cancer as its house. Its rulerships are symbolic table relationships, not measured physical facts about the Moon.¹

Which signs does Moon rule?

The Moon is the ruling planet of Cancer and is exalted in Taurus, according to the Wikipedia article on planets in astrology. Those assignments describe a symbolic table, not a physical control the Moon exerts.⁶

Why do descriptions of Moon differ?

Ptolemy's Tetrabiblos groups the Moon with Jupiter and Venus as beneficent, while modern astrology links it with intuition, emotions and rhythms. Each layer comes from a different period and tradition, so the sources should be read separately.¹⁶

Method and review

Every statement about Moon was checked against the wording of its 6 sources (Ptolemy (LacusCurtius), Encyclopaedia Britannica, Wikipedia and NASA Science), and its positions and boundaries were calculated with Astronomy Engine. How the Machine works.