When the moon is rising just over the horizon,it appears huge.How is this optical illusion explained?

Question

With my thumb extended at arms length,I can measure the moon at the horizon,and again straight over head to be about 3/4's of my
thumbnail,or about 1/2 degree.Yet the moon at the horizon appears several times larger than it does against the night sky.
Why???

Answer 1

Nice article
http://www.lhup.edu/~dsimanek/3d/moonillu.htm

Answer 2

In part, this has to do with visual references. You see the Moon against the trees or houses and it looks huge. In part this has to do with a lensing effect of the atmosphere.

But there was an interesting experiment performed in a dome, with objects of the same size at various angles of elevation, including overhead and at the horizon. And the things overhead looked smaller than the things at the horizon.

Now in a space that small, there can't be any lensing effect, and there wasn't anything on the horizon to measure the object against. There is just something in the human brain that makes objects appear smaller overhead than at the horizon.

Answer 3

Your test results are not explained by the appearance in relation to objects near the horizon. But think of how much more atmosphere you are looking through when you look toward the horizon. The atmosphere bends the light like a magnifying glass and makes the moon look bigger. It also changes the wave length of the light and gives the moon that rust color.

Answer 4

It's simple.

In my local town, there is a long street down which you can see a distant mountain. When you start down the street from the end away from the mountain, the mountain looks huge and near against the tiny houses and trees at the end of the street. As you drive down the street and the houses and trees at the end get bigger, its as if the mountain recedes, instead of coming towards you.

It is all about seeing the object against familiar objects, and when those familiar objects are distant, it tricks your eye into thinking the object is bigger than it really is.

Note that if you watch the moon rise over the ocean and there is nothing on the horizon, like land or ships, the moon does not look so huge as when it rises and there are distant trees and houses to scale it by.

It is pure optical illusion.

Answer 5

It is distorted because of several affects.
1, it is in the horizon and the size compared to other items, like trees etc.

2. Distortion because you see the moon through more of the earths atmosphere which is stretched out more than simply looking straight up at the sky

3. Depending on where you are on the world where the moon sets and rises cit can be closer to the earth because it's orbit is actually elliptical and not a straight circle, actually making it closer to the earth, probably not close enough to make it noticeable to the eye, but probably noticeable when compared to your thumbnail.

Answer 6

The only explaination is the tidal wave in night, as the closest place near the moon has the gravity that makes moon look larger.The reason of this illusion is how angle of moon was viewed, and the moon was commonly viewed from the far rather than been closer which make it look big.

Therefore, the moon's size changed due to the distance between earth and the moon.

Answer 7

Multiple exposure photography has revealed that the moon does not change apparent size as it rises. The illusion that it is bigger near the horizon is due to the fact that you have visual references for comparison, ie trees, buildings. Astronauts and deep-submersible aquanauts have noted that without visual reference it is impossible to tell size and distance. Something outside the spacecraft may be a 1000 feet long and two miles away or an inch long and just outside the window. Without the 'haze' effect of our atmosphere and other visual clues there's just no way to tell.

Answer 8

I was told that once. It's because you have a visual reference of size when the moon is close to the horizon. It makes your mind think it is bigger when it's the same size as when it's overhead. Weird, but it is the same size in both places. I'd swear it was magnified when it's low too. But if you hold up a ruler, or use some other way to measure, it's the same size no matter where it is.

Answer 9

It is not lensed through the thick atmosphere to look larger (otherwise it would appear to be more than half of a degree hello :) )

It is simply because the trees, mountains, buildings are there near it for reference, something distant to compare it too. Your brain goes "whoa that tree is super far away and looks small but the moon is even farther and doesn't look that small".

Simple as that.

Answer 10

It looks larger since it has something next to it for reference. Once it rises into the sky it sits all by its lonesome with nothing next to it to reference size.