In this issue:
"The Exercise Paradox": Studies of how the human engine burns calories help to explain why physical activity does little to control weight—and how our species acquired some of its most distinctive traits.
"Pop Goes the Universe": The latest astrophysical measurements, combined with theoretical problems, cast doubt on the long-cherished inflationary theory of the early cosmos and suggest we need new ideas.
"High-Flying Microbes": Aerial drones and chaos theory help researchers explore the many ways that microorganisms spread havoc around the world.
"Deep-Space Deal Breaker": New studies show cosmic radiation could be even more damaging to astronauts' brains than we thought. Can humanity still live and travel among the stars?