The Jovian Planets

Jupiter, Saturn, Uranus, Neptune

Try this movie of jupiter as seen from one of its moons.

They are far away:

They are big:

Some of them rotate fast:

Their densities are low: The low densities suggest that these planets are mostly made of gas. They are cold at their cloud tops: Low temperature at start of solar system would allow

We should learn something about the physics of gases.

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA