Are you ready for the world’s oldest optical illusion? This begs the question that they didn’t exist before Man was around to see them, which in Europe’s case seems to be around 1.2 million years as the tooth of one such individual was found at the Atapuerca site in Spain this week. This ancient 25 year-old lived in Burgos and maybe holidayed nearby in my favourite resort, San Sebastian. He probably started a timeshare business…
Back to the optical illusion our ancient Spaniard would have seen. The moon. You must have noticed how the full moon ofen seems HUGE when rising or setting. Well surprise surprise, the moon is actually the same size whether it is overhead or just above the horizon. I’m not referring to that other nonsense red-herring, the alleged magnifying effect of the atmosphere – it doesn’t happen! The varying apparent size is an illusion created by your mind. You are used to the perspective of objects on the horizon being ‘smaller’ than the same objects when overhead – eg clouds, airplanes and birds. So you think the moon looks bigger. According to an article in space.com here you can test this hypothesis by taking a photo at moonrise and overhead, or sellotape a rolled paper, compare with the eraser on a pencil end, and so forth. The article also refers to the variations in the moons position due to its orbit.
It seems to me that when I see the full moon on the horizon that I see the craters more clearly as if they are enlarged so maybe the moon is enlarged but only by my brain – there must be a little magnifying lens and a screen in my head. Overhead, of course, the moon is much brighter – almost hurts, and yet it reflects much less sunlight than the Earth does from the moon. I love other facts about the moon, such as it is moving away from the Earth at an annual rate of 3.8 cm, which is why the Earth is slowing its axis rotation. One day the moon’s outward momentum will be equal to the gravity pull by the Earth, then the latter will pull it back — and it won’t stop.
Do we have another moon? Yes, and I don’t mean the Space Station and hundreds of artificial satelites. In 1999 another 3 miles diameter rock was found to be orbiting Earth. I think the United Nations should hurry up and put its flag on it before a real estate company, or MacDonalds does!
Hey, I’ve finished writing my science fiction 86,000 word novel, Exit, Pursued by a Bee. Does anyone want to read it? Please form a queue in my inbox. Publishers have preemptive priority…