If you believe the world’s leading physicists, the vast majority of matter in the universe is hiding in plain sight. For nearly a century, evidence has mounted that the gravitational …

“Success in creating effective A.I.,” said the late Stephen Hawking, “could be the biggest event in the history of our civilization. Or the worst. We just don’t know.” Are we …

In 1935, Albert Einstein and two colleagues published a landmark paper revealing that quantum mechanics allows widely separated objects to influence one another, even though nothing travels between them. Einstein called it spooky and rejected the idea, arguing instead that it exposed a major deficiency in the quantum theory.

Proposed a century ago to better explain the mind-bending behavior of the smallest constituents of the universe, quantum theory has implications far beyond the atom. This rich set of laws has applications both practical and extraordinary.

A second doesn’t always feel like a second—time can seem to slow down if you’re riding a death-defying roller coaster, or speed up while you’re having a night out on the town. But just what’s going on inside our heads to skew our perception of time?

Black holes may hold the key to understanding the most fundamental truths of the universe, but how do you see something that’s, well, black? Astronomers think they have the answer. …