Quantum physicists Andrew White & Martin Ringbauer explain how they used photons to simulate an encounter between a time traveller and its younger self. The results violate Heisenberg's Uncertainty Principle and other quantum laws.

Extended interview with founder of inflation theory Alan Guth, who reviews the doubts cast on the BICEP2 announcement of the discovery of primordial gravitational waves. He also discusses the implications if the results stand up for grand unified theories, the multiverse, and the Planck data.

Physicist Malcom Fairbairn calculates that the Higgs boson combined with primordial gravitational waves should have caused the universe to collapse -- unless there is other new physics.

Investigating the connection between entropy in thermodynamics and information theory could explain why reality is described by quantum theory, as physicists Jon Barrett and Matt Leifer explain to reporter Colin Stuart.