At What Point Does Spacetime Shift Into Quantum?
Summary
PBS Space Time explores the mesoscale, where classical and quantum physics intersect, to probe the nature of gravity. The episode discusses modern refinements of the Cavendish experiment to measure gravity at milligram scales and uses LIGO data to search for entanglement between macroscopic mirrors. By making gravity small and quantum effects large, researchers aim to detect gravitationally mediated entanglement, potentially revealing the quantum properties of spacetime in laboratory settings.
Topics discussed
Intro: Quantum gravity and the mesoscale
The quantum-classical transition mystery
Defining the mesoscale and experimental goals
Newton, Mitchell, and the need to measure G
Cavendish's torsion pendulum experiment
Why gravity might change at small scales
Challenges in measuring tiny gravitational forces
Vienna experiment with milligram gold spheres
Results and future limits of Cavendish tests
Quantum entanglement and decoherence
Optomechanics and mesoscopic mirror entanglement
Searching for entanglement in LIGO data
Proposals for gravity-mediated entanglement
Sponsorships and closing remarks
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