PBS Space Time Season 2018 Episode 33 Quantum Gravity and the Hardest Problem in Physics

PBS Space Time season 2018 episode 33 is titled "Quantum Gravity and the Hardest Problem in Physics" and discusses the challenge of unifying quantum mechanics and general relativity. The episode begins by exploring the theories of quantum mechanics and general relativity and why they are both successful theories in their respective domains but are incompatible with each other. The host explains how current attempts to unify the two theories, such as string theory, loop quantum gravity, and causal dynamical triangulation, have not yet been successful.

The episode then dives into the challenges of reaching a theory of quantum gravity, including the problem of renormalization in quantum field theory, which leads to infinite values when trying to calculate certain quantities. The host also touches on the role of space-time geometry and how it is problematic for quantum mechanics, which treats space and time as separate entities.

To better understand the issue, the host interviews several experts in the field, including particle physicist Nima Arkani-Hamed and cosmologist Sean Carroll. They discuss the idea that space-time itself might not be fundamental, but instead emerges from something more basic, such as quantum entanglement. They also touch on the concept of holography, which posits that a three-dimensional universe can be described by a two-dimensional surface.

The episode closes by acknowledging the difficulty of the problem and the need for new ideas and approaches to reach a theory of quantum gravity. The host emphasizes that though it may seem discouraging, it is important to keep trying and exploring different avenues and approaches.

Overall, "Quantum Gravity and the Hardest Problem in Physics" is a thought-provoking and informative episode that highlights the challenges of unifying quantum mechanics and general relativity. The host does an excellent job of breaking down complex concepts and interviewing experts in the field to provide a comprehensive and accessible discussion on the topic.