Astronomers Walter Baade and Fritz Zwicky were haunted by two celestial apparitions. It was the early 1930s, and the star-like specters had appeared—and disappeared— from the skies well before either astronomer had been born. But the brief, bright phenomena had transfixed onlookers. Veteran observer Tycho Brahe, for example, was moved to proclaim one a “miracle” when it materialized above his h...

P rotection. For free traders, this word represents the consummate evil. For environmentalists, it is the ultimate good. Of course, for the trade community, “protection” conjures up dark images of Smoot and Hawley, while the environmental camp sees clear mountain streams, lush green forests, and piercing blue skies. One cannot blame all of the tensions at the trade-environment interface on ling...

Oilbirds are active at night, foraging for fruits using keen olfaction and extremely light-sensitive eyes, and echolocate as they leave and return to their cavernous roosts. We recorded the echolocation behaviour of wild oilbirds using a multi-microphone array as they entered and exited their roosts under different natural light conditions. During echolocation, the birds produced click bursts (...