Starwatch

This week in Starwatch I want to go back to basics when it comes to the moon. So why does the moon change shape? Why is it a crescent on one night, a half-moon another night, and a full moon on yet another night? Why is it that on some Butler evenings we don’t see the moon at all? It all comes down to two things — the moon’s orbit around the Earth, and the sun’s light reflecting off the moon.

The moon generates no light of its own. It's all sunlight being reflected as the moon revolves around the Earth. The changing angle between the moon, the Earth and the background sun is responsible for the shape, or phase, that we see. The best way to explain the moon’s phases is to look at the different positions in its orbit. New moon

This is when the moon lies roughly in a line between

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