Look up at the sky at night. Is the Moon round? Is it thin like a smile? It keeps changing! But does the Moon really change shape?
The Moon has no light
The Moon does not make its own light. It is not like a bulb. The Sun shines on the Moon. The Moon bounces that light back to us. It is a bit like a mirror shining back torchlight. So moonlight is really sunlight!
Half bright, all the time
The Sun always lights up half of the Moon. The Moon goes round and round the Earth. As it moves, we see different parts of its bright half.
Sometimes we see the whole bright half. That is a full moon. Sometimes we see none of it. That is a new moon. In between, we see thin crescents and half moons.
Sometimes the bright part grows bigger each night. Then the Moon is waxing. Sometimes it gets smaller each night. Then the Moon is waning.
So the Moon never really changes shape. Only our view of it changes!
The Moon’s own calendar
One full set of shapes takes about 29 and a half days. That is about one month. Then the shapes start all over again.
Scientists give the shapes special names. “Crescent” means a thin curve. “Gibbous” means more than half but not full.
Try this: Look at the Moon every night for one week. Draw its shape each time. Is it growing bigger or getting smaller?