Students measure sunspot speeds and shapes across the solar disk to determine whether the spots are on the Sun or are planets revolving around it (Galileo's dilemma). Includes links to hands-on demonstration of concepts.

Three European organizations provide electronic access to the Codex 72, part of the Galilean Collection at the Biblioteca Nazionale Central in Florence, Italy. Codex 72 discusses "theorems on motion published in the ...

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...

In this activity students are asked to interpret a graph that represents the sunspot cycle from 1900 to 1990, then they are asked to graph the number of sunspots that occurred from 1995 to 2003 in order to understand...

Galileo pioneered astronomy as the first person to study the celestial objects through a telescope. His observations, including the discovery of moons around Jupiter, helped revolutionize the way people thought about the...