The one idea that explains everything
The Moon makes no light of its own — we only ever see the half of it that the Sun happens to be illuminating. As the Moon orbits Earth once every 29.5 days (a "synodic month"), our viewing angle on that lit half changes, and so the visible shape appears to grow and shrink. The Moon isn't changing; our vantage point is.
The eight phases, in order
- 🌑 New Moon — the Moon sits between Earth and Sun; its lit side faces away from us, so the sky is moonless. Best nights of the month for seeing faint stars and the Milky Way.
- 🌒 Waxing Crescent — a sliver appears in the western sky just after sunset, growing night by night.
- 🌓 First Quarter — half lit. Called "quarter" because the Moon is a quarter of the way through its cycle. It rises around noon and sets around midnight, so it dominates the evening sky.
- 🌔 Waxing Gibbous — more than half lit, swelling toward full.
- 🌕 Full Moon — Earth sits between Sun and Moon, and we see the entire lit face. It rises at sunset and sets at sunrise, shining all night.
- 🌖 Waning Gibbous — shrinking now, rising later each evening.
- 🌗 Last Quarter — half lit again, but the other half. Rises around midnight; an early-riser's moon.
- 🌘 Waning Crescent — a thinning sliver in the pre-dawn east, then back to new.
Waxing or waning? The one-second trick
In the Northern Hemisphere, if the Moon's right side is lit, it's waxing (growing); if the left side is lit, it's waning (shrinking). Southern Hemisphere observers flip the rule. Another memory aid: a waxing crescent and the letter "D" curve the same way; a waning crescent matches "C" — "D for developing, C for closing."
Why full moons have names
Traditional names — Harvest Moon, Wolf Moon, Strawberry Moon — come from seasonal markers in North American and European folk calendars, tied to what farmers and hunters were doing that month. A "supermoon" is simply a full moon that coincides with the Moon's closest approach to Earth (its orbit is slightly oval), making it appear modestly larger and brighter. And a "blue moon" is the second full moon inside one calendar month — a quirk of the 29.5-day cycle not quite fitting our months, occurring roughly every two to three years.
Using the Moon for stargazing and photography
Counterintuitively, the full moon is the worst night for astronomy: its glare washes out everything faint. Planets don't mind, but galaxies, nebulae, and meteor showers want the darkest sky you can get — plan them within a few days of the new moon. Photographers, meanwhile, often prefer the quarter phases for shooting the Moon itself: sideways sunlight throws crater shadows into sharp relief along the terminator line, revealing texture the flat-lit full moon hides.
Check today's phase, plus sunrise and sunset for any city, on our Sun & Moon page.