Bicycles to Save Earth

In an effort to spread the use of environment-friendly bicycles, participants lift their bicycles during a demonstration dubbed “Critical Mass,” in an annual Earth Day (April 22) celebration in Budapest, Hungary, on Monday. Critical Mass is a physics term meaning the minimum amount of a fissile material required to sustain a chain reaction. Tens of thousands of people participated in the event. One of the participants lifted his child, instead of a bicycle.