Readers who tucked the December 2004 issue into their travel bags for the holidays could take an armchair tour of a wide assortment of topics and times. They could hike through new evidence about the 19th-century Anglo-French controversy over whose citizen-scientist discovered Neptune first; reflect on the cover story's very 21st-century question, "Are viruses alive?"; and take in culture by exploring whether or not 15th-century artists employed optical projections. Those preferring more exotic climes and times, say, the Cretaceous period, could track Arctic Alaskan dinosaurs.

December also featured the "Scientific American 50," which prompted Brian Miller of Woodland Hills, Calif., to write: "I sincerely want to thank all the outstanding minds who bring us these innovations. And thanks also to Scientific American for giving them the credit they so seldom receive."