File:Sun-Moon apparent sizes (sequence).gif

English: Apparent sizes of the Sun and Moon depicted to scale. The Sun is about 400 times the diameter of the Moon. But it is also ~400 times farther away, so their apparent sizes when viewed from Earth are roughly the same. Both appear as roughly half a degree in diameter. With the Earth and Moon being in elliptical orbits, the apparent size varies slightly. The Sun's apparent diameter changes from 31' 36" – 32' 42" (0.5267° - 0.5450°), while the Moon has a little more variation changing from 29' 26" - 33' 30" (0.4905° - 0.5583°). Because there are times when the Moon appears larger than the Sun and other times when the Moon appears smaller than the Sun, this enables two distinctly different types of eclipses to occur: total and annular. During a total eclipse, the Moon will fully block the Sun. During an annular eclipse, a full ring of the Sun is still visible when the Moon is centered directly over the Sun.

This gif image cycles through 19 separate frames. Here is the description for each frame:
1 - the Sun's apparent size when the Earth is at aphelion,
2 - the Sun's apparent size when the Earth is at perihelion,
3 - the Moon's apparent size when it is at apogee,
4 - the Moon's apparent size when it is at perigee,
5 - the Moon at perigee (top half) and apogee (bottom half),
6 - the Moon at perigee (top half) and the Sun when the Earth is at perihelion (bottom half),
7 - the Sun when the Earth is at aphelion (top half) and perihelion (bottom half),
8 - the Moon at its smallest centered on the Sun at its largest (as in an annular eclipse)
9 - the Moon at its smallest centered on the Sun at its largest, superimposed with the Sun at its smallest,
10 - the Moon at its smallest centered on the Sun at its smallest (as in an annular eclipse)
11 - the Moon at its largest centered over the Sun at its smallest (as in an total eclipse), but the limb of the Moon has been made partially transparent,
12 - " "
13 - the Moon at its largest centered over the Sun at its smallest & largest, superimposed (as in total eclipses), but the limb of the Moon has been made partially transparent,
14 - " "
15 - the Moon at its largest centered over the Sun at its largest (as in an total eclipse), but the limb of the Moon has been made partially transparent,
16 - " "
17 - the Sun at its smallest (top left) with the Moon at its largest (top right) and the Sun at its largest (bottom left) along with the Moon at its smallest (bottom right)
18 - the Sun at its smallest (top left) with the Moon at its smallest (top right) and the Sun at its largest (bottom left) along with the Moon at its largest (bottom right)
19 - Superimposed quarters of the Moon at its largest and smallest (top left) with the Sun at its largest an smallest (top right) and the Moon at its smallest over the Sun at its largest (bottom left) along with the Moon at its largest over the Sun at its largest but made partially transparent (bottom right).

This similarity with Earth's two most prominent celestial bodies has been taken to be a cosmic coincidence. Some see this fact to be evidence in support of an anthropic principle pointing to intelligent design. A common scientific attitude is to dismiss this fact as a purely random coincidence. An alternative scientific understanding is a theory that there was a causal relationship with the similarity of apparent sizes with these two bodies in being a favorable factor for the evolution of life on Earth, in that the tidal forces caused by the Moon and Sun in this specific configuration helped to stabilize the climate and environment.