The moon’s shapes

Have you ever noticed that the moon keeps changing?

Some nights it is a big, round, glowing circle. Some nights it is half a circle, like a slice of an orange. Some nights it is just a thin curve, like a smile, or a fingernail. And some nights you cannot see it at all.

Is the moon really changing shape? No. The moon is always a big round ball of rock. It is about a quarter as wide as the Earth. It is also a very long way away. If you could drive there in a car, it would take about six months without stopping.

Here is a secret. The moon does not make any light of its own. It is like a mirror. The light we see is sunlight, bouncing off it.

The sun always lights up half of the moon. But as the moon travels around the Earth, we see different amounts of that lit-up half. When we can see all of it, we call it a full moon. When we can see only a little sliver, it is a crescent. When the lit side is facing away from us, we see nothing, and that is called a new moon.

It takes the moon about twenty-nine and a half days to go through all its shapes and back again. That is about a month. In fact, the word “month” comes from the word “moon”.

The moon does something else as well. It pulls on the Earth’s oceans, a little bit, all the time. That pull helps make the tides. The sea comes up the beach and goes back out again, twice a day.

For thousands of years, people have used the moon as a calendar in the sky. Muslims begin each new month when the first thin crescent is seen after sunset. That is how they know when Ramadan starts, and when it is time for Eid. The Jewish calendar follows the moon too, and the first day of each Jewish month is a small celebration. And Christians work out the date of Easter each year by looking at the moon.

Muslims read in the Qur’an that God measured out the moon’s stages. At the end of each month it comes back thin and curved, like an old palm branch. Jewish people sing a Psalm that says God made the moon to mark the seasons. Once a month, many go outside at night to say a blessing over the growing moon. It is called Kiddush Levanah.

So the moon is a clock, a calendar and a lamp, all at once. And it is always there, even when you cannot see it.

Twelve people have walked on the moon. The first was Neil Armstrong, in 1969. There is no wind or rain on the moon. So their footprints are probably still there today, just as they left them.

Tonight, before bed, have a look out of the window. What shape is the moon?

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