Families with three or more boys, for example, are more likely to have another boy than a girl as the next child.

Burning of fossil fuels, forests and grasslands sends small particles called aerosols into the air. High levels of aerosols can create a thick haze, cutting back on sunlight reaching Earth’s surface ...

Nuclear deterrence is no longer a two-player game, and emerging technologies further threaten the status quo. The result is a ...