Origins of Dark Energy with Adam Riess - StarTalk Radio Recap

Podcast: StarTalk Radio

Published: 2025-12-16

Duration: 1 hr 7 min

Guests: Adam Riess

Summary

Nobel laureate Adam Riess discusses the discovery of the accelerating expansion of the universe, known as dark energy, and the ongoing efforts to understand its nature and implications.

What Happened

In this episode, Neil deGrasse Tyson, alongside co-host Paul Mercurio, delves into the intricacies of dark energy with Nobel laureate Adam Riess. Riess recounts the journey to discovering the accelerating expansion of the universe, a breakthrough that challenged the long-held assumption that the universe's expansion was slowing due to gravity. Using data from distant supernovae, Riess and his team found that the universe was actually expanding at an increasing rate, suggesting the presence of an unknown force now called dark energy.

Riess explains the role of supernovae as standard candles in measuring cosmic distances and how these measurements led to the realization of the universe's acceleration. The episode explores the implications of this discovery for cosmology, including how it necessitates a reevaluation of the universe's fate, potentially leading to scenarios like the Big Freeze or Big Rip.

The conversation touches on the challenges of measuring cosmic distances accurately, particularly the impact of cosmic dust, and the methods developed to account for such variables. Riess highlights the cutting-edge technology and telescopes, like the James Webb Space Telescope, that are refining these measurements and providing new insights.

The episode also addresses the so-called 'Hubble tension,' a discrepancy between measurements of the universe's expansion rate, and the potential for new physics to emerge from resolving this tension. Riess notes that while the current model of the universe fits much of the data, these discrepancies suggest there may be more to discover about the fundamental workings of the cosmos.

Finally, Tyson and Riess discuss the broader implications of these discoveries for understanding the universe, including the potential for dark energy to change over time and what this could mean for the future of cosmology. The episode ends with Riess expressing optimism about the capabilities of upcoming astronomical projects and the potential for new discoveries.

Throughout the episode, humor and camaraderie between the hosts and guest make complex scientific concepts accessible and engaging, offering a deep dive into the mysteries of the universe while maintaining an entertaining tone.

Key Insights