Stephen L. Petranek, editor in chief of Discover magazine, looking back at the 10 top science discoveries of 2004. Also, bird flu spreading in Japan; EPA says 223 counties in 20 states are in violation of standards concerning soot; Courts are now ruling on the admissibility of evidence obtained by brain scans, scientists and ethicists concern say this technology is not ready for that; Scientists find gene that helps control colon cancer; Can dental X-rays save your life?.