History’s worst technological catastrophes could kill millions or billions of people in this century, and to prevent them, society may need to consider restricting specific types of scientific research, says Sir Martin Rees, Britain’s astronomer royal, in the book, “Our Final Hour.”

His concerns include gray goo (nanobots out of control) and experiments that could create a black hole. “I think the odds are no better than 50-50 that our present civilization on Earth will survive to the end of the present century,” Rees says.