Everyone knows that the sun is much larger than the moon and much further away from earth. In this very context lies a fascinating fact: both celestial bodies appear to be of similar size on the firmament, when observed from earth. Which implies that the sun has to be as many times bigger than the moon, as it is further away from the earth than the moon from the earth …
Once more: If a body is placed at a large distance, it will appear smaller than if placed closer to us. This can be easily understood, when for example, two tennis balls are placed at different distances and when looked at as if they are lying next to each other. The tennis ball that lies further away will appear smaller. Now, if you place two various sized objects (i. e. a ping-pong ball and a tennis ball) at different distances, it is possible to place the smaller ball in the precise position in the foreground, for it to appear of the same size as the larger ball in the background. You can say that the »visual diameters« of the objects are equal.
This is also the case with the moon and the sun when we look at them from earth. The diameter of the sun is almost exactly 400 times bigger than of the moon (diameter sun = 1,391,400 km and diameter moon = 3,476 km). If you compare the distance from earth to the sun with the distance from earth to the moon, it is also about 400 times the value (distance earth-sun = 149,600,000 km and distance earth-moon = 384,400 km as average value, equals approx. 389 times). This value varies in reality and increases and decreases, because distances change due to the orbits of the celestial bodies.
One can say that sun and (full) moon appear as if they have an approximate size and for us people, nearly have the same visual diameter. This difference becomes very apparent during a solar eclipse, where the moon moves in front of the sun, and if it is a total eclipse, covers it completely (see image above). When at this point in time, the moon happens to have a slightly smaller visual diameter, we have a so called annular eclipse, where a very bright ring remains and surrounds the sun.
Some say that it is coincidence that the earth, the moon and the sun are scattered in space the way they are. However, other look at it as a geniality of creation. An excerpt from Erich Kästner’s novel ›Lottie and Lisa‹, in a different context, however, quite suitable describes it like this: »As if the almighty God merely spit it out.«