Anglų rašinys. Though a satellite of Earth, the Moon is bigger than Pluto. The 27.3-day number is what scientists call a sidereal month, and it is how long it takes the Moon to orbit the Earth in relation to a fixed star. Like the four inner planets, the Moon is rocky. The Moon has almost no atmosphere, so a layer of dust -- or a footprint -- can sit undisturbed for centuries. The Moon travels around the Earth at a little more than half a mile per second.