Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas

Einstein's general theory of relativity, plus some reasonable assumptions about the universe and what it's made of, has a remarkable implication: that as we trace cosmic evolution into the far past, we ultimately hit a singularity of infinite density and curvature, the Big Bang. Did that really happen? Einstein's theory is classical, after all, and the world is quantum. And whose to say what assumptions are reasonable? Niayesh Afshordi and Phil Halper have written a new book, Battle of the Big Bang: The New Tales of Our Cosmic Origins, that surveys all of the mind-bending possibilities.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/05/26/316-niayesh-afshordi-and-phil-halper-on-the-big-bang-and-before/

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Niayesh Afshordi received a Ph.D. in astrophysics from Princeton University. He is currently a professor of physics and astronomy at the University of Waterloo, and associate faculty in the cosmology and gravitation group at the Perimeter Institute for Theoretical Physics.

• Web site
• Perimeter web page
• Waterloo web page
• Google scholar publications

Phil Halper is a science communicator and a fellow of the Royal Astronomical Society. His astronomy images have been featured in major media outlets including The Washington Post, the BBC, and The Guardian, and he has published several papers in peer-reviewed journals.

• YouTube channel (Skydivephil)

Every time you see an apple spontaneously break away from a tree, it falls downward. You therefore claim that there is a law of physics: apples fall downward from trees. But how can you really know? After all, tomorrow you might see an apple that falls upward. How is science possible at all? Philosophers, as you might expect, have thought hard about this. Branden Fitelson explains how a better understanding of probability can help us decide when new evidence is actually confirming our beliefs.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/05/19/315-branden-fitelson-on-the-logic-and-use-of-probability/

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Branden Fitelson received a Ph.D. in philosophy from the University of Wisconsin-Madison. He is currently Distinguished Professor of Philosophy at Northeastern University. He is a co-founder of the Formal Epistemology Workshop, and winner of the 2020 Wolfram Innovator Award.

• Web site
• Northeastern web page
• PhilPapers profile
• Google Scholar publications
• Wikipedia

There are living creatures dwelling deep below the surface of the Earth, as deep as we are able to drill. These hearty microorganisms are related to more familiar life forms on land and under water, but the operate and survive in ways that are quite different from what we're familiar with. They live off of nutrients that have penetrated from the surface, or sometimes off of pure electrons. Karen Lloyd is a scientist who has traveled around the world studying these organisms, as she explains in her new book Intraterrestrials: Discovering the Strangest Life on Earth.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/05/12/314-karen-lloyd-on-the-deep-underground-biosphere/

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Karen Lloyd received a Ph.D. in marine sciences from the University of North Carolina. She is currently the Wrigley Chair in Environmental Studies and Professor of Earth Sciences at the University of Southern California. Among her awards are a Sloan Fellowship, a Simons Early Career Investigator, and a NASA Early Career Fellowship.

• Lab web site
• USC web page
• Google Scholar publications
• Bluesky

Medical science is advancing at an astonishing rate. Today we talk with leading expert Eric Topol about two aspects of this story. First, the use of artificial intelligence in medicine, especially in diagnostics. This is an area that is a perfect match between an important question and the capabilities of machine learning, to the point where AI can out-perform human doctors. And second, our understanding of aging and what to do about it. Eric even gives some actionable advice on how to live more healthily into our golden years.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/05/05/episode-313-eric-topol-on-the-changing-face-of-medicine-and-aging/

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Eric Topol received and M.D. from the University of Rochester. He is currently the Gary and Mary West Chair of Innovative Medicine in the Department of Translational Medicine at Scripps Research. He is also the Founder, Scripps Research Translational Institute, and Senior Consultant, Scripps Clinic, Division of Cardiovascular Diseases. Among his awards are the Hutchinson Medal from the University of Rochester and membership in the National Academy of Sciences. His books include Deep Medicine: How Artificial Intelligence Can Make Healthcare Human Again, and Super Agers: An Evidence-Based Approach to Longevity.

• Web site
• Scripps web page
• Google Scholar publications
• Wikipedia
• Substack
• Bluesky

Welcome to the May 2025 Ask Me Anything episode of Mindscape! These monthly excursions are funded by Patreon supporters (who are also the ones asking the questions). We take questions asked by Patreons, whittle them down to a more manageable number -- based primarily on whether I have anything interesting to say about them, not whether the questions themselves are good -- and sometimes group them together if they are about a similar topic. Enjoy!

Blog post with AMA questions and transcript: https://www.preposterousuniverse.com/podcast/2025/04/28/ama-may-2025/

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The germ theory of disease is a crowning achievement of science, up there with modern physics, continental drift, and evolution via natural selection. (Even if there will always be cranky skeptics.) But the road to widespread acceptance isn't always an easy one. Why did it take so long between Anton van Leeuwenhoek seeing "animalcules" in a microscope (1670s) to Louis Pasteur's work on pasteurization and vaccination (1860's)? Thomas Levenson is the author of a new book exploring this fascinating history: So Very Small: How Humans Discovered the Microcosmos, Defeated Germs--and May Still Lose the War Against Infectious Disease.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/04/21/episode-312-thomas-levenson-on-the-mutual-history-of-humans-and-germs/

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Thomas Levenson received a B.A. in East Asian Studies from Harvard University. He is currently Professor of Science Writing and director of the graduate program in science writing at the Massachusetts Institute of Technology. He is the author of numerous books and has written and produced a number of science documentaries for television.

• Web site
• MIT web page
• Wikipedia
• Amazon author page
• Bluesky

Questions about consciousness range from the precise and empirical -- what neurons fire when I have some particular experience -- to the deeply profound -- does consciousness emerge from matter, or does matter emerge from consciousness? While it might be straightforward to think that consciousness arises from the collective behavior of atoms in the brain, Annaka Harris and others argue that consciousness could be the fundamental stuff from which matter arises. She talks with a variety of experts in her new audio series, Lights On: How Understanding Consciousness Helps Us Understand the Universe.

Blog post with show notes and transcript: https://www.preposterousuniverse.com/podcast/2025/04/14/311-annaka-harris-on-whether-consciousness-is-fundamental/

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Annaka Harris received a BFA from New York University. She is the author of Consciousness: A Brief Guide to the Fundamental Mystery of the Mind. She is a co-founder of Project Reason.

• Web site
• Wikipedia
• Amazon author page

Welcome to the April 2025 Ask Me Anything episode of Mindscape! These monthly excursions are funded by Patreon supporters (who are also the ones asking the questions). We take questions asked by Patreons, whittle them down to a more manageable number -- based primarily on whether I have anything interesting to say about them, not whether the questions themselves are good -- and sometimes group them together if they are about a similar topic. Enjoy!

Blog post with questions and transcript: https://www.preposterousuniverse.com/podcast/2025/04/07/ama-april-2025/

Support Mindscape on Patreon.

A couple of links relevant to the intro:

• Tariff formula (Snopes)
• Tufts student nabbed by ICE (plus video)

Cosmologists were, let us be honest, pretty stunned in 1998 when observations revealed that the universe is accelerating. There was an obvious plausible explanation, the cosmological constant proposed by Einstein, which is equivalent to a constant vacuum energy pervading space. But the cosmological constant was known to be enormously smaller than its "natural" value, and it seems fine-tuned for it to be so small but not yet zero. Once burned, twice shy, and since then we have been looking for evidence that the dark energy might not be strictly constant, even though that's even more fine-tuned. We talk to cosmologist Marc Kamionkowski about recent evidence that dark energy might be changing with time, and what this might have to do with the Hubble tension and other cosmic anomalies.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/03/31/310-marc-kamionkowski-on-dark-energy-and-cosmic-anomalies/

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Marc Kamionkowski received his Ph.D. in physics from the University of Chicago. He is currently the William R. Kenan Jr. Professor in the Department of Physics and Astronomy at Johns Hopkins University. Among his prizes are the Gruber Cosmology Prize, the Dannie Heineman Prize for Astrophysics, membership in the National Academy of Science, and a Guggenheim Fellowship.

• Johns Hopkins web page
• Google Scholar publications
• Wikipedia
• Kamionkowski and Riess, "The Hubble Tension and Early Dark Energy"
• Dark Energy Spectroscopic Instrument paper and followup
• Dark Energy Survey paper

Consciousness is easier to possess than to define. One thing we can do is to look into the brain and see what lights up when conscious awareness is taking place. A complete understanding of this would be known as the "neural correlates of consciousness." Once we have that, we could hopefully make progress on developing a theoretical picture of what consciousness is and why it happens. Today's guest, Christof Koch, is a leader in the search for neural correlates and an advocate of a particular approach to consciousness, Integrated Information Theory.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/03/24/309-christof-koch-on-consciousness-and-integrated-information/

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Christof Koch was awarded a Ph.D. from the Max Planck Institute for Biological Cybernetics. He is currently a Meritorious Investigator at the Allen Institute for Brain Science, where he was formerly president and chief scientist, and Chief Scientist at the Tiny Blue Dot Foundation. He is the author of several books, most recently Then I Am Myself the World - What Consciousness Is and How to Expand It.

• Web site
• Allen Center web page
• Google Scholar publications
• Amazon author page
• Wikipedia