How Fast Is the Universe Really Expanding? | PODCAST: The Joy of Why
One of the most contested issues in astrophysics is our understanding of the Universe’s expansion. Nobel laureate Adam Riess discusses why there is disagreement and what might resolve it.“The Joy of Why” is a Quanta Magazine podcast about curiosity and the pursuit of knowledge. The mathematician and author Steven Strogatz and the cosmologist and author Janna Levin take turns interviewing leading researchers about the great scientific and mathematical questions of our time. For more episodes visit Quanta Magazine: https://www.quantamagazine.org/tag/the-joy-of-why/
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0:00 Intro
3:19 Adam Riess: student to Nobel laureate
5:50 Why supernovae?
10:16 Measuring cosmic distances
15:36 Type Ia supernovae
20:56 Hunting supernovae
25:06 1998: the universe is accelerating
29:47 Einstein's cosmological constant and dark energy
35:52 The Lambda-CDM model
43:13 The Hubble tension: 73 vs. 67
56:35 New telescopes and the joy of mystery
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One of the biggest mysteries in cosmology seems to keep getting bigger. Astronomers have known since the 1930s that the universe is expanding, but in the 1990s, the discovery that this expansion is accelerating rather than slowing down came as a huge shock to the field. Something had to be driving that acceleration, and dark energy was proposed as the cause. What began as a seismic shock in cosmology eventually led to a Nobel prize.
But this story has a sequel, and it comes with another major plot twist. The two main methods for estimating the universe's present-day expansion rate are producing significantly different answers. As a result, how fast the universe is really expanding has become a matter of considerable debate — with no small amount of angst — and the discrepancy has become known as the Hubble tension. Perhaps most surprising of all is that one of the loudest voices raising concern is Adam Riess, the astrophysicist whose Nobel Prize-winning work helped ignite the acceleration debate in the first place.
Riess joined co-host Steven Strogatz on The Joy of Why to explain how we got to this point, what the Hubble tension might be telling us, and what may happen next.
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The Joy of Why is a podcast from Quanta Magazine, an editorially independent publication supported by the Simons Foundation. Funding decisions by the Simons Foundation have no influence on the selection of topics, guests, or other editorial decisions in this podcast or in Quanta Magazine. The Joy of Why is produced by PRX Productions. The production team is Caitlin Faulds, Jade Abdul-Malik, Genevieve Sponsler, and Merritt Jacob. The executive producer of PRX Productions is Jocelyn Gonzales. Edwin Ochoa is our project manager. From Quanta Magazine, Simon Frantz and Samir Patel provided editorial guidance with support from Samuel Velasco, Simone Barr, and Michael Kanyongolo. Samir Patel is Quanta’s editor-in-chief.
The episode art is by Chanelle Nibbelink and our logo is by Jaki King and Kristina Armitage. Special thanks to Garth Avery at the Cornell Broadcast Studio.
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