Why is the moon bigger on the horizon?

Answer 1

Its because of the refraction of the light as it comes through the earths atmosphere, you get a similar effect as if you put a finger in a glass of water and it looks shorter when you look at it from the top but if you look at it side on it looks the correct size

Answer 2

it is an optical illusion. The comparison of the moon to the nearby horizon makes it appear larger than comparison with a horizon that's far away (angularly). The moon is dimmer and redder when near the horizon, which makes it easier to perceive against the black surroundings.
Those who answer by quoting Snell's law and the like are wrong, since this would only have the effect of displacing the apparent position of the moon. No magnifying effect occurs by this mechanism, and even if it did, it would only be in vertical direction, stretching the moon into an ellipse shape (which it clearly isn't).

Answer 3

The air that the light from the moon travels through when it is vertical is much less mass than the air the moon's light travels through when it is on the horizon, and the angle of incidence of the light through the earth's atmosphere means the kight from the 'top' of the moon travels at a different angle than the 'bottom' - refraction of the light obeys Snells Law - so the lower angle on the horizon acts like a magnifying glass to make the moon appear bigger...

Answer 4

The reason for the apparent larger and "redder" moon when it is viewed on the horizon vs. when it is viewed from overhead is that the moon's light must travel through the most dense part of the earth's atmoshphere before it reaches our eyes when it is on the horizon.

90% of the earth's atmosphere is found within about 2 miles above its surface, therefore when the moon's light is viewed by us as it rises above the horizon, we are looking at the moon through the thick surface atomosphere and the light is defused and refracted much more than when we look at it through the thinner upper atmosphere when the move is overhead.

As the light travels through the thick surface air, it is bent and slowed so that the "red" portion of the spectrum of light is made visible and the disc of the moon appears to widen.

Answer 5

The other answers you have received are good, although Steve's isn't correct. If it were, then the image of the moon on the horizon would be larger than the image of a moon high in the sky on photographs, too. It isn't.
The explanation I like best is that most people intuitively imagine that the horizon is farther away than overhead. So if two images actually are the same size, but we think (subconsciously) that one comes from an object farther away, we perceive that object as larger. An example of that is the "monster chasing monster" optical illusion. Here is one websit with it: http://www.coolopticalillusions.com/optical_illusions_pictures_3/impossible_monster_triangle_illusion.htm
It's here, too: http://thebrain.mcgill.ca/flash/a/a_02/a_02_p/a_02_p_vis/a_02_p_vis.html

Answer 6

It's not that the moon is bigger on the horizon. It's that he horizon is smaller on the horizon. This makes the moon look bigger by comparison.

The horizon looks bigger when it is straight over your head than when it is laying flat.

Answer 7

It isn't.

It looks larger than when it's high in the sky, because it's visually close to distant landmarks (also on the horizon) which cause us to overestimate its size. But if you measure the actual size of the Moon's disc, you will see it's exactly the same at the horizon as at the zenith, and everywhere in between.

Answer 8

It is an optical illusion. It looks bigger when it is low because there are many things on the horizon to compare it to, size wise.

Answer 9

the larger appearance is due to the curvature of the Earth and the way the Light is bent, the result produces a larger appearing MOON. Check sources for a sketch of this phenom and you will visualize this much better..Good Luck!!!!!!!!

Answer 10

It's not actually bigger, it just looks that way. I'm not sure why. It is always the same distance from the earth, sortof like it's on a pole.