The Moon’s Shine

Unlike stars that shine and twinkle, the Moon does not.

The Moon does, however, appear to shine as it reflects light from the Sun.

Anaxagoras, a Greek philosopher (510 – 428 BC) is said to be the first person to discover this.  (He also thought the world was flat, so you can make of that as you will.)

And despite the fact that the Moon sometimes seems to shine very brightly indeed, it only reflects between 3 and 12% of the sunlight that hits it.  Imagine how bright it would look reflecting more than that.

The perceived brightness of the Moon, as viewed from the Earth, depends on where the Moon is in its 29.5-day journey around the Earth.  And, at any given point in that journey, only half of the Moon’s surface is facing the Sun.  What this means is, that only half of the Moon’s surface is lit at any one time, and therefore, the other half that is facing away from the Sun is in shadow.

Basic primary school science I know – but wait – there’s more . . .

The Moon is at its brightest when it’s 180° away from the Sun (Sun-Earth-Moon) and the illuminated half of the Moon’s surface, a Full Moon, is visible from the Earth.

On the other hand, when the Moon is between the Sun and the Earth, when we have a New Moon (Sun-Earth-Moon), the side of the Moon that is reflecting sunlight is facing away from us and isn’t visible from our vantage point.

And we thought the Moon had a dark side.

The fact is that the Moon has a far side, not a dark side.

In the days before and after a New Moon, we can sometimes see a faint brightness of the rest of the Moon.  This is the result of what scientists call earthshine – sunlight reflecting off the Earth and slightly illuminating the remaining (dark) disc of the Moon.  Wow!

The Moon’s shine is caused by our star and our planet.

I’ve captured earthshine once (or maybe twice) and, although this photo isn’t the best quality, it does show the Moon reflecting light from both the Sun and the Earth.

– ⋅ o ♥ o ⋅ –

This is my next entry in my Blue Moon Squares as part of Becky’s ‘Blue’ Square in July photo challenge.