Though a satellite of Earth, the moon, with a diameter of about 2,159 miles (3,475 kilometers), is bigger than Pluto. (Four other moons in our solar system are even bigger.). The moon is a bit more than one-fourth (27 percent) the size of Earth, a much smaller ratio (1:4) than any other planets and their moons. This means the moon has a great effect on the planet and very possibly is what makes life on Earth possible.