The Moon: Earth's Satellite and Your Daily Mood

What is the Moon?

The Moon is Earth’s only natural satellite, a rocky body 3,475 km across, about a quarter of Earth’s width. It orbits Earth at an average of 384,400 km, between about 356,400 km at its closest (perigee) and 406,700 km at its farthest (apogee), so its light reaches us in about 1.3 seconds. It goes around Earth once every 27.3 days, and it always shows us the same face. Its phases, from New Moon to Full Moon and back, take 29.5 days, because Earth moves along its own orbit in the meantime.

Where the Moon is in the sky

The ecliptic is the path the Sun appears to follow across our sky over a year, the plane of Earth’s orbit seen from Earth. Positions along it are measured in degrees, from 0° at the March equinox to 360°. The zodiac divides it into twelve equal 30° parts named after signs: Aries covers 0° to 30°, Taurus 30° to 60°, and so on. The signs are counted from the equinox, not from the star patterns they were named after; those constellations now sit about 24° further along, because Earth’s axis slowly wobbles (precession).

The Moon’s orbit is tilted about 5° to the ecliptic, so the Moon wanders up to about 5° north or south of it. It is the fastest body in the zodiac: about 13° a day, so it changes sign every two to three days and goes all the way around in 27.3 days. It always moves forward: it never goes retrograde.

The Moon in astrology

In astrology the Moon stands for feelings, instincts, moods and the need for comfort and home. Because it changes sign every two to three days, it sets the emotional tone of each day, which is why daily horoscopes follow it closely. The Moon rules Cancer.