World History Encyclopedia
World History Encyclopedia: Archimedes
Illustrated entry provides an account of the life of Archimedes, a pioneer in the fields of mathematics and engineering.
How Stuff Works
How Stuff Works: How Helium Balloons Work
This article explains how helium is able to keep balloons afloat in the air. Compares them to how hot air balloons work. Includes a video, and some activities to try for testing the principles being discussed.