The lunar cycle

The Moon changes shape every night. In a little under a month, twenty-nine and a half days, it goes from dark to full and back to dark, then starts over. It's the most visible cycle in the sky, and the oldest tool we have for measuring time.

The circle has two halves. From the New Moon to the Full Moon the lit part grows: this is the waxing half. From the Full Moon to the next New Moon the light fades: this is the waning half. Each half divides in two again, and the hinge is a quarter, the moment you see exactly half a Moon: the First Quarter halfway up, the Last Quarter halfway down.

Four moments mark the cycle, then: New Moon, First Quarter, Full Moon, Last Quarter. The waxing half is where you start and build, the waning half where you gather and let go; the two quarters are the tensest passages, where something gets decided. Knowing where you are in the circle is good for exactly this: working with the moment instead of forcing it. The four chapters take them one at a time.

• New Moon, beginning
• The waxing phase, pushing
• Full Moon, seeing and letting go
• The waning phase, lightening