The Moon doesn’t change shapes. It’s always a round ball shape, just like the Earth is. What’s changing is how much of the Moon we can see each night. It doesn’t give off its own light, like the Sun. Instead, it reflects the Sun’s light back to us on Earth.
If the Moon were always in the same place, we’d see it pretty much the same way every night, but it’s not. It travels around the Earth, just like the Earth travels around the Sun. Also, just like the Earth, sunlight only lights up one side of the Moon at any time.
If the entire side of the Moon that is lit up by the Sun is facing us, we see a full moon. If only half of the Moon’s lit-up side is facing us, we see what’s called a “quarter moon,” which looks like half a circle. Some nights there’s no moon in the sky at all. Other nights there’s only a sliver. It all depends on how much of the Moon’s lit-up side we can see from Earth.
Just a Phase
The different Shapes of the Moon are called “phases.” There are a lot of words people use to describe them. Here are some good ones to know.
A new moon is when none of the moon can be seen.
A crescent moon is when less than half of the Moon’s lit-up side can be seen from Earth. (Often looks like the letter “C”)
A quarter moon is when we can see exactly half of the Moon’s lit-up side.
A gibbous moon is when more than half can be seen.
A full moon is when all of the Moon’s lit-up side can be seen from Earth.
As the moon goes from new to full, we say that the moon is “waxing” or getting bigger.
As the moon goes from full back to new, we say that it is “waning” or getting smaller
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