Moonrise

Thought I might blip the moon this evening but couldn't see it in the sky by about 8.15, so I looked it up with some astronomy software and soon realised that the moon must just be coming over the horizon. Emma and I quickly dashed to the clifftop and sure enough there it was. Within minutes it had made some distance between the sea and sky.

Curiously, the usual effect of the moon appearing big when near the horizon did not happen. This effect is called the moon illusion and I think astronomers have stopped studying it now, and handed the case over to psychologists.

Apart from the strip of the moon which really does have it's light bent by the earth's atmosphere when on the horizon, the rest is an illusion. It is thought that the proximity of the moon to familiar objects like trees, houses, chimneys and so on make our brains change our idea of how big it looks.

So the illusion didn't happen tonight, as the moon rose over the sea and there were no familiar objects to measure it's size against - just sea!

In reality, if you hold a circle or coin at a certain distance from your eye to just cover the moon when it is near the horizon and then repeat this exact procedure (ie same coin and distance) when the moon is overhead, there should be no change.

BTW that was not a pun about coins! :)