The tsunami that wiped out a nuclear plant on the coast of Japan and lead to a triple meltdown has been an enormous setback for the promoters of fission-generated power. But of the four fundamental forces of nature, it is gravity, not nuclear, that has caused the most casualties at Fukushima. The death toll from the crashing waves killed some 20,000 people. But no one, including emergency workers at the plant, has died from the radiation, and no one has yet been diagnosed with a radiation-induced cancer. It is still very early. Ionizing rays†the kind powerful enough to break molecular bonds†can mutate genes, and the effects may not be apparent for decades. All we can do is predict.