Sean Carroll on Quantum Mechanics, Many-Worlds, and the Evolution of Scientific Understanding

This podcast episode features Sean Carroll discussing quantum mechanics and his book "Something Deeply Hidden," contrasting it with classical mechanics and exploring the philosophical implications of modern physics. The conversation begins by revisiting Isaac Newton's classical mechanics, highlighting his discomfort with "action at a distance" (gravity) and how later figures like Pierre Simon Laplace and Albert Einstein reframed it through field theories and the speed of light limit. Carroll emphasizes that while intuition guides scientific inquiry, it can also be trained and should not dictate the ultimate form of physical laws, challenging the notion that answers must conform to preconceived ideas.

The discussion delves into the nature of understanding and the limits of human cognitive abilities, referencing Noam Chomsky's ideas on biological constraints. Carroll argues that while visualization might have limits, the human capacity for abstract, logical, and symbolic manipulation, akin to a Turing machine, suggests no inherent limits to understanding the scientific world in principle. He posits that our intuitions evolve and can be trained to grasp complex concepts like fields pervading spacetime. A central philosophical point explored is the distinction between the world as it is and the world as we observe it, acknowledging the vast gap between our sensory perception and the underlying reality, which science helps bridge through cognitive capacities.

Carroll identifies the conservation of momentum as the most beautiful idea in physics, explaining how it marked a profound shift from an Aristotelian view of nature's purposes and teleologies to an impersonal understanding of patterns in the universe. He traces this concept's long evolution, from Avicenna's early insights to Galileo and Newton, underscoring its foundational role in modern science. The conversation also clarifies the relationship between mathematics and physics, with math describing the logical structure of all possible worlds and physics describing our actual world, marveling at the "unreasonable effectiveness" and surprising simplicity of mathematics in compressing information about reality.

Finally, the episode defines quantum mechanics as the paradigm that replaced classical mechanics, introducing the concept of a quantum state or wave function governed by the Schrodinger equation. Carroll highlights the unique and perplexing role of measurement or observation in quantum mechanics, where a system's state dramatically changes upon being observed, unlike in classical physics. He also provides a historical overview of the atom and electron, from ancient Greek ideas to Dalton's chemical evidence and Rutherford's discovery of subatomic structure, explaining how electrons are the key players in chemical interactions and electricity, and how quantum mechanics is essential for modeling their behavior.

"Newton almost invented chaos theory as soon as he invented classical mechanics he realized that in the solar system..."

"I leave that for future generations to think about because I don't know what the answer is"

"it rubs me the wrong way to think that we should presume the answer should look one way or the other like if it turned out that there was action at a distance in physics and that was the best way to describe things that I would do it that way"

"our intuitions get trained right like you know I have different intuitions now that I had when I was a baby that's okay that's not an intuition is not necessarily intrinsic to who we are we can we can train it a little bit"

"of all the worries that keep me awake at night the human minds inability to rationally comprehend the world is low on the list"

"conservation of momentum... is the most beautiful idea in physics is because it shifts us from a view of nature's and teleology to a view of patterns in the world"

"very very roughly math is about the logical structure of all possible worlds and physics is about our actual world"

"the surprising thing is not that math works but that the math is so simple and easy that you can write it down on a t-shirt right"

"atoms and molecules are more fundamental than cells and organs quantum fields are more fundamental than atoms and molecules"

"Newton was the greatest scientists who ever lived I mean he met in calculus in his spare time which would have made it the greatest mathematician just all by himself right"

"quantum mechanics unlike any other theory of physics places uh gives a fundamental role to the act of measurement"

"the atom that we think about now the cartoon is that picture you you always seen of a little nucleus and then electrons orbiting it like a little solar system"