The universe is mostly empty space. Even in a "crowded" region like our solar system, the distances between planets are so vast that they are difficult to imagine. This animation simulates a voyage from the sun past all nine planets. For convenience, the planets are lined up in the same direction. The animation shows each planet's average distance from the sun. At the speed of today's fastest spacecraft (~20 km/second), it would take almost ten years to travel this distance. Even at the speed of light, the trip would last 5 1/2 hours. In this animation, the apparent speed of the viewer is over 300 times the speed of light.