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

310 | Marc Kamionkowski on Dark Energy and Cosmic Anomalies

Mar 31, 2025

Marc Kamionkowski, a leading cosmologist at Johns Hopkins University, dives into the intriguing realm of dark energy and cosmic anomalies. He discusses the shocking 1998 discovery that the universe is accelerating, exploring the implications of the cosmological constant and its puzzlingly small value. Kamionkowski shares insights on the Hubble tension—discrepancies in the universe's expansion rates—and the potential for dark energy to vary over time. Their conversation showcases the ongoing battle to decode the universe's mysteries through collaborative scientific efforts.

01:26:14

Episode guests

Marc Kamionkowski

AI Summary

AI Chapters

Episode notes

Podcast summary created with Snipd AI

Quick takeaways

Recent findings suggest that dark energy's density may be changing over time, challenging its previous classification as constant.

The Hubble tension highlights a discrepancy in the universe's expansion rate that raises significant questions within the cosmology community.

Ongoing research initiatives like DESI and EUCLID aim to deepen our understanding of dark energy and potential cosmic anomalies.

Deep dives

The Importance of Collaboration in Hiring

Effective hiring hinges on the collaboration of individuals with diverse perspectives and talents. Employers face challenges in promoting job listings across various platforms. Using Indeed's Sponsored Jobs can significantly enhance visibility, placing job postings right at the top for the desired candidates. This method has been shown to deliver up to 45% more applications than regular postings, illustrating the power of strategic hiring practices.

Intro

2min

Unraveling Dark Energy and Cosmology

15min

Exploring the Necessity of Dark Matter in Cosmological Observations

2min

Understanding Cosmology Through Observational Evidence

2min

Exploring Dark Energy and the Cosmological Constant

21min

Understanding the Hubble Tension: Exploring Cosmic Expansion Rates

2min

Navigating the Cosmic Measurements

30min

Navigating the Cosmos: Hubble Tension and Dark Energy

15min

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/

Support Mindscape on Patreon.

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.