The Arrow of Time and How to Reverse It
Summary
This PBS Space Time episode explores the arrow of time, explaining how the second law of thermodynamics breaks the time-reversal symmetry of fundamental physics through the inevitable increase of entropy. The hosts discuss how the universe’s initial low-entropy state at the Big Bang dictates the forward direction of time, allowing for the expansion of the cosmos and the perception of a distinct past and future. The segment concludes with a brief discussion of listener comments regarding electroweak theory and the philosophical implications of free will in a deterministic universe.
Topics discussed
Sponsors: Progressive Truck Insurance and UKG
Introduction: The mystery of time's direction
Two ways we perceive the arrow of time
Time symmetry in physics and the block universe
Entropy and the Second Law of Thermodynamics
Sponsors: Progressive, UKG, and Anthropic
How low entropy breaks time symmetry
Cosmic expansion and the Big Bang as low entropy
Speculating on a time-reversed universe
Sponsors and transition to viewer comments
Comment: Could fundamental forces break further?
Comment: Free will and information in a deterministic universe
Comment: Philosophical labels in physics discussions
Comment: The superiority of QED
Closing Sponsors: Progressive, UKG, and Anthropic
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