why sun looks bigger in the evening? although it's closer to the earth during noon?
It's not significantly closer to Earth during noon. Your eye could never percieve the difference.
I would have to guess its for the same reason as the Moon illusion. When the Moon is low, you have foreground to compare it to. That sets up an optical illusion that deceives you into thinking that it is bigger.
The Moon's horizon and overhead distances are slightly greater than insignificant, with it being bigger overhead. But the difference is still small enough that the optical illusion overwhelms it.
One thing I've noticed is that if you lie on the ground looking straight up at the sky, things overhead (clouds particularly) look closer than when you are standing up.
I believe that only happens because you (any person) are on the ground looking up from being too stoned to stand....:rofl:
Didn't you ever picnic in the park with your girl friend?
Yes, many times but I don't recall ever looking UP.
This is true. If you will Google on fovea, you will see how the non-uniformity in the eye and the non-uniformity in the visual cortex work together to give us a magnified and sharpened image in the center of our field of view. This effect is especially pronounced in birds of prey, who often have to locate their food from very high up.
In a word, refraction. The earth's atmosphere magnifies the image.
Thats just a function of positioning.
Not enough for you to notice, and the effect is in the wrong direction, anyway. When you are looking straight up, you are looking through the least amount of atmosphere possible. The apparent largeness and sharpness of things in the center of our field of view is due to the physiology of the eye and to the manner in which the eye is wired to the visual cortex.
Turbo is correct, it's an illusion:
If you're looking at the sun close enough to notice this, you should see an eye doctor. :yuck:
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