Galileo used thought experiments to test many assumptions, including the notion that heavy objects fall more quickly than lighter objects when they are dropped. Lacking access to either a vacuum chamber or a planetary...

Before the 17th century, people generally believed that Earth was at the center of the universe, a system originally developed by Ptolemy. Galileo, however, was not afraid to challenge existing beliefs when he published...

Authored by Jurgen Geisen, this site has more than sixty-five Java applets. The interactive resources provide detailed solar and lunar data and the daily and annual path of the sun and moon for any location. More...

The folks at the Science Education Research Center (SERC) at Carleton College have worked with a team of colleagues to create these "Guided Discovery Problems." The materials here help students learn about the world of...

This website from the University of Washington Department of Astronomy provides introductory astronomy activities on topics such as: fundamentals of astronomy, observing the sky, the sun, stars, stellar evolution, the...