Is Sun Rays Parallel?

Parallel sunlight

The radiant energy of the sun spreads in every direction. However, since the sun and the earth are far apart, we assume that they are usually almost parallel.
Ancient Greece’s Eratosthenes measured Earth’s size quite accurately, assuming that the sun’s rays are parallel to the Earth’s surface.

Evidence that sunlight is not parallel

In fact, the sun light on Earth is not parallel. The sun is not a point light source. The diameter of the sun is about 109 times that of the earth. The surface is much wider than the earth. Light is emitted in all directions from a very wide open area of the sun.

Shadows created by tall buildings are not clearly defined. This tells us that the sun is a very large object.
Or if you look at the floor under the tree, you can see the image of the sun made by the principle of a needle-hole camera. Normally the image of the sun is a round circle, but in the case of solar eclipse, the shape appears on the bottom. (Pictured below right)