Sun

The sun is a rotating sphere. It has a diameter of 32 miles and is located approximately 3000 miles above the surface of the earth.

Spotlight effect

The Sun's area of light is limited to a circular area of light upon the earth much like the light of a lighthouse is limited to a finite circular area around it. The rotating light on a lighthouse does not propagate infinitely into the distance. This means that only certain portions of the Earth are lightened at a time. It also describes how night and day arise on a Flat Earth. The apparent view of rising and setting are caused by perspective, just as a flock of birds overhead will descend into the horizon as they fly into the distance.

Rendered picture of the Sun in relation to the Earth

Not to scale: http://theflatearthsociety.org/forum/index.php?topic=1264.0

More:

• Temperature Variations of sunlight
• Distance to the Sun
• The Seasons
• The Setting of the Sun
• Constant Speed of the Sun
• Magnification of the Sun at Sunset, or how the sun maintains its size throughout the day.