What causes the apparent flattening of the sun's disc? A detailed explanation would be preferable.?

Question

Please explain the apparent flattening of the sun's disc at sunrise and sunset. It looks more like a sphere during the day, but when it is at the horizon, it looks like a circle, not a sphere. Why? Please explain the process.

By 'horizon' I mean the sun setting at the sea. When you're at the beach, you have nothing to compare it to. It's just you and the sun.

Answer 1

Refraction of the light rays from the sun as they pass through the atmosphere.

When the sun is low in the sky, its rays pass through air of different densities.

This difference in densities is caused by the different temperatures as the land mass that the sun is leaving behind begins to cool. The part of the earth that is entering into night is cooler than the part that is still in the day, and so is the air that is above.

The rays of the sun must pass through these different layers of air and so the rays are refracted much like how light is refracted between air and water.

This refraction causes the image of the sun to be "distorted."

Answer 2

I'm guessing. I would guess at sunset and sunrise it has things on the horizon you can compare it to. Your brain knows the shape of, say, tree and knows it can go there, so tree is interpreted by your brain as a 3D object. Whereas the thing you can't run to, and as the previous answer stated, parallax is no help get interpreted as the easiest thing your brain knows that fits, a circle.

At Zenith if you have nothing to compare it to, your higher cortex is not busy resolving "tree" and the info that it is a sphere gets into your perception.

You can test this by somehow looking at the sun from under a tree and see if the branches make it seem like a circle not a sphere.

Of course, never stare at the sun, but I assume you are not an idiot, and will just do a quick glance.

Since the big differences of at the horizon are
1) more atmosphere for the image to go through
2) more known objects in visual "frame"
I'd bet those are the difference.

Answer 3

no2 goon reply seam in sunrize to sunset earth round itself
our see angle different like that we cannot see the fact of shape of sun for rays trouble in morning to afternoon seam like sphere in sunset the fact really of size of sun show by compare the line of horizonal

Answer 4

During sun rise and sun set distance of the sun from eye is more than that during mid day, by diameter of the earth.
Which is the cause of dialation.

Answer 5

The sun is far away, so parallax offers no input, and since it's emitting light it shows no shading from other light sources. So it looks like a circle.