The phases of the Moon

If you look at the sky on a clear night, you may see the Moon round like a coin and, a few days later, thin like a smile. Is it shrinking? Is someone taking bites out of it? Neither. The Moon always has the same shape: what changes is the part of it that we see lit up.

The Moon makes no light of its own

The Moon is a huge ball of rock that does not produce light. It shines because the Sun lights it, just as a flashlight lights up a ball in a dark room. One half of the Moon is always lit by the Sun and the other half is in the dark.

A trip of almost a month

The Moon travels around the Earth and takes about 29 and a half days to complete one trip. While it moves, we look at it from different angles. Sometimes we see almost its whole face lit; other times only an edge, or nothing at all.

The four main phases

New Moon: the Moon is between the Sun and the Earth and shows us its dark side, so we hardly see it. First quarter: we see the right half lit (in the northern hemisphere) and each night the bright part grows. Full Moon: the Earth is between the Sun and the Moon and we see its whole face lit. Last quarter: we see the other half lit and each night the bright part gets smaller. Then it all starts again.

A tip to remember it

In the northern hemisphere, if the lit part is on the right, the Moon is growing; if it is on the left, it is shrinking. In the southern hemisphere it is exactly the opposite.

Activity: your Moon diary

For one month, look out of the window at the same time every night and draw the Moon in a notebook. If it is cloudy, write that down. At the end, put the drawings in order and you will see a complete cycle. You can repeat it as a family with a flashlight and a ball to watch how the shadow changes.

One last curiosity

Even though its look changes, from the Earth we always see the same face of the Moon, because it takes the same time to spin once as to travel around our planet.

💡 We always see the same side of the Moon from Earth.