Ever notice the moon is bigger when it’s closer to the horizon?

We are bounded in a nutshell of Infinite Space: Free Form #6: Ever notice the moon is bigger when it’s closer to the horizon?

Has the Moon ever looked bigger? Does it change its distance to the Earth throughout the night? Could the Earth’s atmosphere or the amount of photons reflected off the moon have anything to do with it?

Actually, none of these reasons explain why the Moon is perceived by most to be bigger at certain parts of the night, rather the answer actually comes down to an optical illusion. The moon, when close to the horizon, is also much closer to the objects near the ground, giving the human eye a comparison from which to estimate the Moon’s size, but this actually leads us astray. Records since the Ancient Greeks to Immanuel Kant speak as to why this illusion occurs, but Aristotle was quite wrong when it came to Astronomy, as you could tell if you ever read his dialogues on falling objects. He postulated that the Earth’s atmosphere created a lensing effect near the horizon, while there was no evidence if this happening with any other object besides the Sun.

The optical illusion occurs from the eye’s estimate of size based on depth perception, which noticeably changes when the Moon is closer to other objects of similar or apparently larger size (i.e. trees, mountains, among others). Otherwise, when the Moon is well above the horizon, the only point of comparison is the vastness of space, which most definitely makes our eyes believe we are looking at something very far away. Actually, when close to the horizon, the Moon is farther away by a distance slightly longer than the radius of the Earth simply because of how the Earth’s rotation changes our frame of reference. This effect is called the Ebbinghaus Illusion (popularized in a psychology textbook published in 1901), which places two objects of the same size in the middle of other objects of smaller and larger size.

As can be seen in the image, the object placed in between large objects is perceptibly smaller than the object between smaller objects. This is the same effect for the moon, where large expanses of empty space make the Moon seem small (its ordinary size) and when close to the horizon, the smaller trees and relief make the Moon seem like another planet close to ours. In fact, if you were to simply close one of your eyes as you observed the Moon when it’s close to the horizon, you would see it shrink to its regular size. The same goes if you were to block out the features of the horizon and were only looking at the moon. 

References:

https://en.wikipedia.org/wiki/Moon_illusion

https://upload.wikimedia.org/wikipedia/commons/thumb/b/bc/Mond-vergleich.svg/2000px-Mond-vergleich.svg.png

http://i.livescience.com/images/i/000/049/591/original/super-moon-2011-tim-mccord-entiat-wash.JPG?1336008254