

Does physics have to be causal and local?
13 snips Sep 18, 2025
In this enlightening talk, Sean Carroll, a theoretical physicist and philosopher known for his work on quantum foundations and cosmology, dives into the intricacies of locality and causality in physics. He breaks down what locality means in relation to quantum mechanics and relativity, discussing how entanglement challenges traditional views. Carroll also explores the definition of causality, the implications of quantum fluctuations, and even speculates on quantum gravity and the emergent nature of space. A mind-bending journey into the universe's fundamental principles!
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What Locality Means In Physics
- Locality means interactions occur at the same point or neighboring points in space-time rather than instant action at a distance.
- Fields mediate distant effects by having local values that influence neighbors, producing apparent long-range forces.
Quantum States Are Fundamentally Non‑Local
- Quantum mechanics replaces localized particles with a global wavefunction describing systems together.
- That wavefunction is manifestly non-local when multiple particles are entangled, challenging naive locality.
Laplace Localized Newtonian Gravity
- Laplace rewrote Newtonian gravity as a field theory, introducing the gravitational potential field at every point in space.
- This made Newtonian gravity describable by local differential equations rather than instantaneous action at a distance.