Why Does Earth Have Only One Moon?

Most planets have several moon friends. Jupiter has dozens! Mars has two tiny rocks. But Earth is a bit of a lone wolf. We only have one big best friend in the sky. This happens because long ago, something huge crashed into our planet. Imagine throwing a ball at a hula hoop; if it hits just right, the hoop keeps the ball close. The crash broke off part of Earth, and that piece stayed with us instead of floating away. It grew bigger over time while other potential moons either fell down to Earth or drifted out into space where they did not have enough pull to stay nearby.