During the night, as we sleep, a beautiful celestial dance is taking place. While Earth seems solid and still, it's actually spinning on its axis and circling the sun. Joining Earth in this orbit around the sun are the other seven planets in our solar system, along with dozens of moons and millions of comets and asteroids. Containing our solar system is the wondrous Milky Way galaxy, with its billions of stars, just like our own sun, swirling and whirling around. And on from there are the billions of galaxies with their own stars swirling and whirling into the ever-expanding space called our universe.