New moon and full moon: what each one is for

It is the shortest and most visible cycle in the sky, and the only one anyone can check by looking out of the window.

It lasts 29 and a half days, repeats twelve or thirteen times a year, and organises much of what people do with astrology day to day.

What each one is, astronomically

At the new moon, the Sun and the Moon sit at the same point of the zodiac as seen from Earth. The Moon is on the Sun's side and cannot be seen: the sky is dark.

At the full moon, they face each other, 180 degrees apart. The Moon takes the light head-on and shows whole. It rises as the Sun sets.

About fourteen and a half days pass between those two positions, and the full cycle — new to new — is 29 and a half days.

What each one is used for

The traditional reading is straightforward and needs no decoration.

The new moon is the start of the cycle: the moment to begin, to sow, to decide something while nothing is visible yet. It does not ask for results. It asks for a direction.

The full moon is the middle: what was sown is now visible, for better or worse. It is the moment of conclusions, of what comes to light and what ends. Hence its links to closing, letting go, and also to arguing: everything is more visible, the uncomfortable included.

The sign matters less than it seems

Every lunation falls in a sign, and that sign gives it a theme. A new moon in Virgo speaks of order, health and work; a full moon in Aries, of deciding alone. But that happens to the whole planet at once.

What makes the difference is which house of your chart it lands in. The same Virgo new moon can fall in your sixth house — and be about your job — or in your tenth, and be about your career. That is where the general sky becomes a fact about you, and for that you need your chart.

An honest note

There is a widespread idea that the full moon disturbs people, causes insomnia or fills hospital emergency rooms. It is a very old and very repeated belief, and the studies that went looking did not find it.

The Moon does not alter your behaviour from a distance. What the lunar cycle offers is something more modest and more useful: a natural calendar every two weeks to start something and then review it. It works because it has rhythm, not because it influences.

How to use it without losing the plot

Two notes are enough. At the new moon, write down one thing you want to begin. At the following full moon, two weeks later, read it and see what happened. No further ritual is required, and after three or four cycles you have a record of your own year.

Your natal Moon sign is a different thing from these lunations: that one never changes. And for the current one, see the article on the lunation underway.

The short version

• New moon: Sun and Moon on the same point. Full moon: opposite, 180° apart.
• The full cycle is 29 and a half days, twelve or thirteen times a year.
• New is for beginning; full is for seeing, concluding and letting go.
• The sign gives the general theme; the house in your chart makes it yours.
• It does not alter your behaviour: it works as a calendar, not an influence.

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