While H.I.V. rates have fallen in many places, the AIDS crisis remains in some of the U.S.

Normalization of deviance, the process of becoming inured to risky actions, is a useful concept that was developed to explain how the Challenger disaster happened.

Newborns today are tested for genetic and immune disorders that might not be apparent at birth. The tests evolved from the treatment of a patient with a rare diagnosis who became known as “the Boy in the Bubble.”

Is geo-engineering the climate an answer to global warming? Cold War science has some lessons.