theoretical physics

Richard Feynman’s path integral is both a powerful prediction machine and a philosophy about how the world is. But physicists are still struggling to figure out how to use it, and what it means.

Two teams have made photons act as if time were simultaneously flowing in two directions. The experiments demonstrate a way to potentially boost the performance of quantum devices.

Maintenance of the software that’s used for the hardest physics calculations rests almost entirely with a retiree. The situation reveals the problematic incentive structure of academia.

The unprecedented experiment explores the possibility that space-time somehow emerges from quantum information.

Two physicists have calculated that the universe has a higher entropy — and is therefore more likely — than alternative possible universes.

The past and the future are tightly linked in conventional quantum mechanics. Perhaps too tightly. A tweak to the theory could let quantum possibilities increase as space expands.

Physicists have discovered that the ring of photons orbiting a black hole exhibits a special kind of symmetry, hinting at a deeper meaning.

Quantum field theory may be the most successful scientific theory of all time, but there’s reason to think it’s missing something. Steven Strogatz speaks with theoretical physicist David Tong about this enigmatic theory.

The key to understanding the origin and fate of the universe may be a more complete understanding of the vacuum.