What is the deepest level of reality? In this Quanta explainer, Vijay Balasubramanian, a physicist at the University of Pennsylvania, takes us on a journey through space-time to investigate what it’s made of, why it’s failing us, and where physics can go next.
00:00 - The Planck length, an intro to our space-time journey
1:23 - Descartes and Newton investigate space and time as separate variables
2:04 - Einstein's special relativity
2:32 - The geometry of space-time and the manifold
3:16 - Einstein's general relativity, a unified picture of space-time in four dimensions
3:35 - Measuring the mathematical curvature of space-time
4:57 - Breaking down Einstein's field equation
6:04 - Singularities, where general relativity breaks down
6:50 - Intro to quantum mechanics (amplitudes, entanglement, Schrödinger equation)
8:32 - The problem of quantum gravity
9:38 - What happens when we apply quantum mechanics to our manifold?
10:36 - Why particle accelerators can't test quantum gravity
11:28 - What if there is something deeper than space-time?
11:45 - Hawking and Bekenstein discover black holes have an entropy, a big clue about quantum gravity
13:54 - The holographic principle
14:49 - AdS/CFT duality
16:06 - Space-time may emerge from entanglement
17:44 - The path to quantum gravity
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