Nova production by Providence Pictures, Inc. for WGBH/Boston.
Originally produced as a segment of the television program, Nova, broadcast on Feb. 13, 2001.
Director of photography, Dominic DeSantis ; editor, Gary Glassman ; animation, John Biafore ; colorist, Brian Lovery ; sound recordist, Juan Rodriguez ; music, Ed Tomney.
Closed captioned for the hearing impaired.