Chemistry classes will appreciate this color-coded, single-page reference sheet for The Standard Model of particle physics. It is divided into two main sections: elementary particles and compound particles, both with their antiparticles....

What does a graph or equation say about a situation? Lots! The lesson uses the concepts explored in the previous four lessons in the series and applies them to problem solving situations. Learners create an equation from problems posed...

A simulation illustrating Ptolemy's geometrical system of explaining the varying speeds and directions of the planets, sun, and moon.

This site from Open Source Physics offers a file with a simulation of Kepler's theory of planetary motion, tested with the Earth rotating around the sun and another planet of the user's choosing. The download requires Java.

An easy-to-read description and history of Ptolemy's geocentric model of the universe. Geocentric means that Ptolemy believed the Earth was the center of the universe.

Take a journey to the center of the Earth and learn about the structure, material properties, and conditions inside our planet.

This site from the University of Arizona provides a background of Ptolemy's profound influence in the areas of astronomy, geography, and cartography. Includes good pictures and related links.

This site from The Eight Planets shows that Titan may serve as a model of a highly reduced early Earth atmosphere in which the first stages of organic chemical evolution could take place in the atmosphere.