Does the universe have a speed limit? If not, some effects could happen at the same instant as the actions that caused them — and some effects, ludicrously, might even happen before their causes. By one hundred years ago, it seemed clear that the speed of light was the fastest possible speed. Causality was safe. And then quantum mechanics happened, introducing spooky connections that seemed to circumvent the law of cause and effect. Inspired by the new physics, psychologist Carl Jung and physicist Wolfgang Pauli explored a concept called synchronicity, a weird phenomenon they thought could link events without causes. Synchronicity tells that sprawling tale of insight and creativity, and asks where these ideas — some plain crazy, and others crazy powerful — are taking the human story next. Shermer and Halpern discuss:

• Model-Dependent Realism, the idea from Stephen Hawking and Leonard Mlodinow that our understanding of nature depends on the model we apply to it, and that we cannot define science as an asymptotic curve toward Truth,
• from Newton to Einstein to Quantum Physics,
• Platonic ideals/idealism,
• Is the universe mathematical?
• Where/what are "laws of nature"?
• What is gravity?
• What is causality and how is it determined?
• quantum entanglement and what it says about our understanding of causality,
• Bell's inequality,
• backward causality,
• Hume's "constant conjunction" definition of causality and it's limitations,
• Hume's "counterfactual" theory of causality,
• Bogus mechanisms of causality: impetus, ether, energy fields, ESP,
• The friendship of Wolfgang Pauli and Carl Jung,
• Jungian archetypes and how scientists think about them,
• God, religion, and spirituality.

Paul Halpern is a professor of physics at the University of the Sciences in Philadelphia and the author of sixteen popular science books, including The Quantum Labyrinth and Einstein's Dice and Schrödinger's Cat. He is the recipient of a Guggenheim fellowship and is a fellow of the American Physical Society. He lives near Philadelphia, Pennsylvania.