Go out on a night when there’s a full moon and find a good spot to watch it rise. There’s a good chance it will look HUGE, whether it’s peeking over the shoulder of a distant mountain, rising out of the sea, hovering behind a cityscape, or looming over a thicket of trees. Here’s the thing: it’s all in your head. The moon’s seeming bigness is actually an illusion, rather than an effect of our atmosphere. You can prove it yourself in a variety of ways. Hold up your outstretched index finger next to the moon. You’ll find that your fingernail and the moon are about the same size. Try looking at the moon through a paper tube, or bend over and look backward between your legs. When you view it that way, the moon will be nowhere near as big as it seemed. Another ironclad way to size-check the moon is to take a photo when it’s near the horizon, and another when it’s high in the sky. If you keep your camera zoom settings the same, you’ll find that the moon is the same width, side to side, in both photos. Why do we see the moon illusion? Brace yourself: no one really knows. There just simply isn’t a rock-solid scientific explanation for it. So, until someone figures out exactly what our brains are up to, it's probably best to just enjoy the moon illusion and the amazing vistas it creates.
