Three thought experiments involving “demons” have haunted physics for centuries. What should we make of them today?

From a particle smasher encircling the moon to an “impossible” laser, five scientists reveal the experiments they would run ...

The daily routines of people around the world all tend to have this in common. You’ll be happier if yours does too.

Astronomers are a step closer to cracking one of the secrets of dark energy—the mysterious force believed to be causing the universe's accelerated expansion.