University of St. Andrews (UK)
University of St. Andrews: Christiaan Huygens
This University of St. Andrews site contains biographical information and findings of Christiaan Huygens.
Concord Consortium
The Concord Consortium: Molecular Workbench: Bunimovich Stadium
Watch as two particles move through a confined area. The emphasis is on their motion in a straight line until they encounter a barrier and are reflected off in a different direction.