We are alive at the right time for the Moon to appear just big enough to cover the Sun in a total eclipse. Over the billions of years that attraction between the Moon and Earth has gradually slowed our rotation, the Moon has retreated from Earth. ts current distance happens to be precisely 1/388 times the Sun's distance & the Moon also happens to be 1/388 times the size of Sun, so each appears to be the same size from our perspective. The moons of other planets exhibit a wide range of sizes and distances from their planets.