Scrat accidentally enters a flying saucer and propels himself into outer space. He travels through the solar system (also by accident), and during his journey finds a solar system, planets, asteroids, and other celestial objects.
While traveling through the solar system, Ms. Frizzle and her class encounter the asteroid belt. There, the class learns what asteroids and the asteroid belt are.
Yakko gives an overview of the universe by describing the celestial objects (stars, galaxies, planets, moons, asteroids, and comets) that exist in the universe and putting into perspective the human race's significance. The song is accompanied by excellent illustrations.
This clip takes us into the universe through a series of steps, with each step being 10x larger than the previous. It illustrates the vastness of the universe and that increasing the field of view by a power of 10 makes a dramatic change in what we see.