We’ve all seen a full moon looming large shortly after it rises, when it’s still hugging the horizon. Scientists say that large moon is an illusion, a trick your brain is playing. It’s called the moon illusion. Its causes aren’t precisely known, but the video above, from AsapSCIENCE, offers some explanation.
By the way, a large moon seen low in the sky might also appear red or orange in color. And that color is not an illusion. It’s a true physical effect, caused by the fact that – when the moon is low in the sky – you’re seeing it through a greater thickness of Earth’s atmosphere than when it’s overhead. The atmosphere filters out the bluer wavelengths of white moonlight (which is really reflected sunlight). Meanwhile, it allows the red component of moonlight to travel straight through to your eyes. So a low moon is likely to look red or orange to you.
How do people get those photos of extra big moons seen near a horizon? They’re the result of photographic tricks and techniques, which you can read about here.
Bottom line: The August 10 supermoon is the closest full moon for 2014. It might look super big seen near a horizon. But all full moons seen near a horizon look big, due to a psychological effect called the moon illusion.