Mooning

Everyone has experienced seeing a huge full moon rising in the distant sky. And we all have our theories on why the moon appears bigger when it is lower in the sky. Some include refraction through the atmosphere, the tilting of our head, etc. But the truth is, the moon’s apparent size remains the same at any point in the sky.

This is hard to believe when you are driving toward this huge orb, but alas it is. If you were to hold a ruler out at arms length and measure the diameter of the moon at any point in the sky, it would be the same. Our minds are playing a trick on us with something called the Ponzo Illusion:

The Moon, when it’s on the horizon, is interpreted by your brain as being farther away. Since it’s the same apparent size as when it’s high up, your brain figures it must be physically bigger. Otherwise, the distance would make it look smaller.

However, tonight’s moon will be about 12 percent larger than other full moons because it is at its closest point to the Earth along its elliptical orbit.

Add comment October 6th, 2006