Why do you see a horizon?

Answer 1

You should be able to figure this out on your own, and I can't really explain it if you lack that much spacial awareness.

Stand near the bottom of a small hill or an arched bridge. You can't see past the peak because the land or bridge curves. The same thing happens when you are standing on the surface of a large a sphere such as the earth. In all directions, the earth curves away from you. This creates the horizon. Interesting side note: The higher up you are, the farther you can see. This is why lighthouses were developed to be taller and taller. The taller the lighthouse, the farther away a ship could be and still see the light.

Answer 2

During the day the sun is above the horizon; at night it is below the horizon. This depends upon whether you, the viewer, are on the same side of the planet Earth as the sun is, or on the opposite side.

Answer 3

The horizon is the apparent line where the sky meets the earth or sea. It appears due to the curvature of the Earth; as you look out, the Earth's surface appears to meet the sky in the distance, creating the horizon line.

Answer 4

The Sun does appear larger when it is close to the horizon - but this is an optical illusion. The "actual" size of the Sun in the sky is the same on the horizon or high in the sky,