Quantum gravity

Physicists are reexamining a longstanding assumption: that big stuff consists of smaller stuff.

In a quest to map out a quantum theory of gravity, researchers have used logical rules to calculate how much Einstein’s theory must change. The result matches string theory perfectly.

Physicists have been busy exploring how our universe might emerge like a hologram out of a two-dimensional sheet. New clues have come from the symmetries found on an infinitely distant “celestial sphere.”

Time was found to flow differently between the top and bottom of a single cloud of atoms. Physicists hope that such a system will one day help them combine quantum mechanics and Einstein’s theory of gravity.

For over two decades, physicists have pondered how the fabric of space-time may emerge from some kind of quantum entanglement. In Monika Schleier-Smith’s lab at Stanford University, the thought experiment is becoming real.

The five-decade-old paradox — long thought key to linking quantum theory with Einstein’s theory of gravity — is falling to a new generation of thinkers. Netta Engelhardt is leading the way.

By showing that even large objects can exhibit bizarre quantum behaviors, physicists hope to illuminate the mystery of quantum collapse, identify the quantum nature of gravity, and perhaps even make Schrödinger’s cat a reality.

The Standard Model is a sweeping equation that has correctly predicted the results of virtually every experiment ever conducted, as Quanta explores in a new video.

Even in an incomplete state, quantum field theory is the most successful physical theory ever discovered. Nathan Seiberg, one of its leading architects, talks about the gaps in QFT and how mathematicians could fill them.