Phases of the Moon

The Moon seems to change shape through the month: a thin curve, a half disc, a full bright circle, and back again. The Moon itself does not change. What changes is how much of its sunlit side we can see from Earth. This page explains the phases. It follows NASA's page on Moon phases, read on 12 November 2026.

The Moon is always half lit

The Moon does not make its own light. Moonlight is sunlight that bounces off it. Like Earth, the Moon has a day side and a night side, and the Sun always lights half of it. As the Moon travels round Earth, we look at that lit half from a changing angle. Sometimes we see all of it, sometimes none, and mostly something in between.

The eight phases, in order

1. New Moon. The lit side faces away from us. The Moon is up during the day and cannot be seen.
2. Waxing crescent. A thin sliver appears. "Waxing" means growing.
3. First quarter. Half the disc is lit. It is called a quarter because the Moon is a quarter of the way round its cycle.
4. Waxing gibbous. More than half is lit, and still growing.
5. Full Moon. The whole face is lit. A full Moon rises at about sunset.
6. Waning gibbous. The lit part begins to shrink. "Waning" means shrinking.
7. Third quarter (or last quarter). Half the disc again, the other half this time.
8. Waning crescent. A thin sliver, before the next new Moon.

How long the cycle takes

NASA gives the length of the cycle as about once a month: every 29.5 days. That is why many calendars, including the traditional Indian ones, measure months by the Moon, and why festivals such as Diwali, Eid and Holi fall on particular phases.

Why we always see the same face

Earth and the Moon are tidally locked. The Moon turns once on its axis in the same time that it goes once round Earth, so the same side always faces us. The far side was first seen in 1959, when a Soviet spacecraft flew past it.

Watch it yourself

• Look for the Moon at the same time each evening for two weeks and draw its shape. You will see it grow from crescent to full.
• In a dark room, hold a ball at arm's length with a lamp behind you and turn slowly on the spot. The lit part of the ball goes through all the phases.
• Notice that the Moon is often in the sky in daytime. Around first quarter it is easy to spot in the afternoon.

Common mix-ups

• The phases are not caused by Earth's shadow. Earth's shadow falls on the Moon only during a lunar eclipse. The ordinary phases come from our changing view of the lit half.
• "Dark side" does not mean unlit. The far side gets just as much sunlight as the near side. We simply never see it from Earth.

More about the Moon's size, gravity and distance is on the Moon page.

Source: NASA, read on 12 November 2026.

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