Theoretical physics

A new theory explains the seemingly irreversible arrow of time while yielding insights into entropy, quantum computers, black holes, and the past-future divide.

A conversation with the mathematical physicist Freeman Dyson on quantum electrodynamics, climate change and his latest pet project.

Scientists report the possible discovery of primordial gravitational waves, ripples in space-time that carry a record of how the universe began.

New calculations suggest physicists may someday discover a fundamental theory of gravity, but it could require a radical new perspective on the universe.

Physicists have devised experiments that can probe the interface between quantum mechanics and general relativity.

Physicists have discovered a jewel-shaped geometric object that challenges the notion that space and time are fundamental constituents of nature.

Theoretical cosmologists are piecing together a cosmic origin story from a surprising anomaly in the recently released Planck satellite image.

Decades of confounding experiments have physicists considering a startling possibility: The universe might not make sense.

An interview with the Nobel Prize-winner David J. Gross on the confusing state of theoretical physics.