Sean Carroll | in truth, only atoms and the void

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I'm a theoretical physicist, specializing in quantum mechanics, gravitation, cosmology, statistical mechanics, and foundations of physics, with occasional dabblings elsewhere. This site contains information about me, including research and my CV, plus news, books, videos, and other activities.

Sean Carroll | in truth, only atoms and the void

1M ago

George Field, brilliant theoretical astrophysicist and truly great human being, passed away on the morning of July 31. He was my Ph.D. thesis advisor and one of my favorite people in the world. I often tell my own students that the two most important people in your life who you will (consensually) choose are your ..read more

Sean Carroll | in truth, only atoms and the void

10M ago

This year we give thanks for a feature of nature that is frequently misunderstood: quanta. (We’ve previously given thanks for the Standard Model Lagrangian, Hubble’s Law, the Spin-Statistics Theorem, conservation of momentum, effective field theory, the error bar, gauge symmetry, Landauer’s Principle, the Fourier Transform, Riemannian Geometry, the speed of light, the Jarzynski equality, the moons of Jupiter, space, black hole entropy, electromagnetism, and Arrow’s Impossibility Theorem.)
Of course quantum me ..read more

Sean Carroll | in truth, only atoms and the void

1y ago

Just a few years ago, Australian Catholic University (ACU) established a new Dianoia Institute of Philosophy. They recruited a number of researchers and made something of a splash, leading to a noticeable leap in ACU’s rankings in philosophy — all the way to second among Catholic universities in the English-speaking world, behind only Notre Dame.
Now, without warning, ACU has announced plans to completely disestablish the institute, along with eliminating 35 other academic positions in other fields. This leaves the faculty, some of which left permanent jobs elsewhere to join the new institute ..read more

Sean Carroll | in truth, only atoms and the void

1y ago

This year we give thanks for Arrow’s Impossibility Theorem. (We’ve previously given thanks for the Standard Model Lagrangian, Hubble’s Law, the Spin-Statistics Theorem, conservation of momentum, effective field theory, the error bar, gauge symmetry, Landauer’s Principle, the Fourier Transform, Riemannian Geometry, the speed of light, the Jarzynski equality, the moons of Jupiter, space, black hole entropy, and electromagnetism.)
Arrow’s Theorem is not a result in physics or mathematics, or even in physical science, but rather in social choice theory. To fans of social-choice theory and voting m ..read more

Sean Carroll | in truth, only atoms and the void

2y ago

Just in case there are any blog readers out there who haven’t heard from other channels: I have a new book out! The Biggest Ideas in the Universe: Space, Time, and Motion is Volume One of a planned three-volume series. It grew out of the videos that I did in 2020, trying to offer short and informal introductions to big ideas in physics. Predictably, they grew into long and detailed videos. But they never lost their informal charm, especially since I didn’t do that much in the way of research or preparation.
For the book, by contrast, I actually did research and preparation! So the topics are ..read more

Sean Carroll | in truth, only atoms and the void

2y ago

As far as I remember, the first time I stepped onto a university campus was in junior high school, when I visited Johns Hopkins for an awards ceremony for the Study of Mathematically Precocious Youth. (I grew up in an environment that didn’t involve spending a lot of time on college campuses, generally speaking.) The SMPY is a longitudinal study that looks for kids who do well on standardized math tests, encourages them to take the SATs at a very young age, and follows the progress of those who do really well. I scored as “pretty precocious” but “not precocious enough to be worth following up ..read more

Sean Carroll | in truth, only atoms and the void

3y ago

This year we give thanks for something we’ve all heard of, but maybe don’t appreciate as much as we should: electromagnetism. (We’ve previously given thanks for the Standard Model Lagrangian, Hubble’s Law, the Spin-Statistics Theorem, conservation of momentum, effective field theory, the error bar, gauge symmetry, Landauer’s Principle, the Fourier Transform, Riemannian Geometry, the speed of light, the Jarzynski equality, the moons of Jupiter, space, and black hole entropy.)
Physicists like to say there are four forces of nature: gravitation, electromagnetism, the strong nuclear force, and the ..read more

Sean Carroll | in truth, only atoms and the void

3y ago

The nature of consciousness remains a contentious subject out there. I’m a physicalist myself — as I explain in The Big Picture and elsewhere, I think consciousness is best understood as weakly-emergent from the ordinary physical behavior of matter, without requiring any special ontological status at a fundamental level. In poetic-naturalist terms, consciousness is part of a successful way of talking about what happens at the level of humans and other organisms. “Being conscious” and “having conscious experiences” are categories that help us understand how human beings live and behave, while c ..read more

Sean Carroll | in truth, only atoms and the void

3y ago

Conservation of energy is a somewhat sacred principle in physics, though it can be tricky in certain circumstances, such as an expanding universe. Quantum mechanics is another context in which energy conservation is a subtle thing — so much so that it’s still worth writing papers about, which Jackie Lodman and I recently did. In this blog post I’d like to explain two things:
In the Many-Worlds formulation of quantum mechanics, the energy of the wave function of the universe is perfectly conserved. It doesn’t “require energy to make new universes,” so that is not a respectable objection to Man ..read more

Sean Carroll | in truth, only atoms and the void

4y ago

This year we give thanks for one of the very few clues we have to the quantum nature of spacetime: black hole entropy. (We’ve previously given thanks for the Standard Model Lagrangian, Hubble’s Law, the Spin-Statistics Theorem, conservation of momentum, effective field theory, the error bar, gauge symmetry, Landauer’s Principle, the Fourier Transform, Riemannian Geometry, the speed of light, the Jarzynski equality, the moons of Jupiter, and space.)
Black holes are regions of spacetime where, according to the rules of Einstein’s theory of general relativity, the curvature of spacetime is so dra ..read more