The photographer Sebastiao Salgado, in New York City on Thursday, says we are at a "special moment" — our world now needs to be protected from climate change and other forces. Misha Friedman for NPR hide caption

itoggle caption Misha Friedman for NPR

This human-scale lab rat cage is parked near a skate park in Denver, Colo., to make a point about the lack of science on marijuana. Richard Feldman Studio/Sukle Advertising and Design hide caption

itoggle caption Richard Feldman Studio/Sukle Advertising and Design

Dr. Harold Varmus, a Nobel Prize winner, cancer biologist and director of the National Cancer Institute. Manuel Balce Ceneta/AP hide caption

itoggle caption Manuel Balce Ceneta/AP