But the Japanese themselves have taught us, in the most awful way imaginable, what the actual health danger of radiation like this might be, and we need to keep the lessons of Hiroshima and Nagasaki in mind as we assess how catastrophic events like this actually are.

We know from studying the survivors of those bombings, who were bathed in horrific doses of high level radiation - far worse than anything that could come from the Daiichi plant (or that came out of Chernobyl) - that ionizing radiation from nuclear energy is a carcinogen, but a relatively weak one. The roughly 100,000 survivors of the two atomic bomb blasts are known in Japan as hibakusha, and they are honored, and given special rights.