This video segment adapted from NOVA scienceNOW examines a developing theory that might explain a 250-million-year-old "murder mystery." While several possible causes have been considered for the mass extinction that occurred at the end of the Permian period, the scientists featured in the video thi
In this video excerpt from NOVA scienceNOW, correspondent and New York Times technology columnist David Pogue learns how cutting an onion triggers chemical reactions that change the properties of the onion. Animations illustrate how enzymes are separated from other molecules inside the cells of an o
In this video excerpt from NOVA scienceNOW, learn about polygraph tests and lie detection. Correspondent and New York Times technology columnist David Pogue commits a staged crime and undergoes a polygraph test to find out how it works. Lying can cause stress, which produces common physiological res
