Half a Blue Moon and Other Bits.

I have a question.

I was out in the garden at twilight this evening, topping up the birds’ feeding tables as I’m wont to do, when I noticed something. My eye was drawn to the bright, first quarter moon hanging splendidly about 30° above the horizon against the mid blue of a clear southern sky, and I began to wonder why I could only see the illuminated half.

The dark side must be there, mustn’t it, to the left of the light side? So why is there only uninterrupted blue sky to the left? There isn’t some celestial being adding layers to the moon as it waxes, and then taking them away from the other side as it wanes, is there? (Although maybe I could write a children’s story called The Moon Maker about just such a being, and then I could let some struggling young independent film maker have the film rights free. Much better that than selling them to the Hollywood moguls, soulless Philistines that they are. But I digress…)

So why couldn’t I see the dark half of the moon in silhouette against the blue of the sky? Could it be that the dark half of the moon is exactly the same shade of blue as the sky at 9pm on 12^th August, and is therefore effectively camouflaged? That seems unlikely. As far as I know, and in direct contradiction to the adage and the romantic song, no part of the moon is ever blue. So then I wondered whether it’s some sort of optical phenomenon, but couldn’t work out how. Or could it be that the blue light from the sky somehow bends around the moon and hides it? I believe light is capable of doing that sort of thing. Is there an astrophysicist in the house?

(More importantly, I couldn’t remember how to spell ‘astrophysicist.’ My mind is definitely faltering these days. But at least the birds are coming back. A lady blackbird joined me in the taking of tea in this afternoon’s sunshine. And yesterday evening I had another first: I saw a deer walking down my lane, at the top near the Harry Potter wood. I’ve never seen a deer walking down the road before. I think it was a young Roe Deer, but we have six species of deer in the UK and some of the smaller ones are similar. And I think that’s about it for today.)