Host: Chris Mooney

When the devastating earthquake and tsunami struck Japan last month, it left behind not only mass destruction, but also a nuclear crisis that was covered 24-7 by the international media.

Since then, we've been embroiled in a huge debate about nuclear policy—should there be a "Nuclear Renaissance" in the United States, or should we put it on hold?

A central issue underlying all this is the scientific question of risk. How dangerous is radiation, anyway? Do we overreact to reactors?

To tackle that question, we turned to two different guests. One is one of the world's foremost experts on radiation exposure and its health consequences; the other is a journalist who's done a new book about why we often misperceive risk, to our own detriment.

David Brenner is the director of the Center for Radiological Research at Columbia University. His research focuses on understanding the effects of radiation, at both high and low doses, on living systems, and he has published more than 200 papers in the peer-reviewed scientific literature. Dr. Brenner was the recipient of the 1991 Radiation Research Society Annual Research Award, and the 1992 National Council on Radiation Protection and Measurements Award for Radiation Protection in Medicine.

David Ropeik is an author, consultant, and speaker on risk communication and risk perception, and an instructor in the Harvard University School of Education, Environmental Management program. He's the author of the 2010 book How Risky is it Really? Why Our Fears Don't Always Match the Facts.