Space-time

The effort to unify quantum mechanics and general relativity means reconciling totally different notions of time.

String theory has so far failed to live up to its promise as a way to unite gravity and quantum mechanics. At the same time, it has blossomed into one of the most useful sets of tools in science.

Just months after their discovery, gravitational waves coming from the mergers of black holes are shaking up astrophysics.

Richard Feynman's famous diagrams weren’t just a way to do calculations. They represented a deep shift in thinking about how the universe is put together.

The spokesperson for the Laser Interferometer Gravitational-Wave Observatory called it “a promising start to mapping the populations of black holes in our universe.”

A satellite spotted a burst of light just as gravitational waves rolled in from the collision of two black holes. Was the flash a cosmic coincidence, or do astrophysicists need to rethink what black holes can do?

The path from a revolutionary set of equations to the detection of gravitational waves was strewn with obstacles and controversy, explains the physicist Daniel Kennefick — and the struggle continues.

Ripples in space-time have been detected a century after Einstein predicted them, launching a new era in astronomy.

Bizarre quantum bonds connect distinct moments in time, suggesting that quantum links — not space-time — constitute the fundamental structure of the universe.