Virginia SOL 6.2 · The Solar System
Use what you know about the solar system, gravity, and the history of astronomy to complete the passage below.
Our solar system includes the sun, eight planets and their moons, dwarf planets, asteroids, comets, and meteors. is distributed throughout the solar system, but the objects in it are very far apart, so most of the solar system is empty . The four inner planets are small and , while the four outer planets are giant worlds made mostly of .
is an attractive force that acts between all objects in the universe. The greater an object's , the stronger its gravitational pull. As the between two objects increases, the force of gravity between them decreases. This force pulled the solar system together long ago, and it keeps each planet traveling around the sun on a predictable path called an .
For most of human history, people believed Earth was the center of the universe. The invention of the gave scientists powerful new observations that challenged this Earth-centered model. Today, robotic spacecraft and powerful computers are examples of that continue to improve our understanding of the solar system.