When it comes to the eventual end of our universe, cosmologists have a few classic theories: the Big Crunch, where the universe reverses its expansion and contracts again, setting the stars themselves on fire in the process. Or the Big Rip, where the universe expands forever—but in a fundamentally unstable way that tears matter itself apart. Or it might be heat death, in which matter and energy become equally distributed in a cold, eventless soup.These theories have continued to evolve as we gain new understandings from particle accelerators and astronomical observations. As our understanding of fundamental physics advances, new ideas about the ending are joining the list. Take vacuum decay, a theory that’s been around since the 1970s, but which gained new support when CERN confirmed detection of the Higgs Boson particle. The nice thing about vacuum decay, writes cosmologist Dr. Katie Mack in her book The End of Everything: (Astrophysically Speaking), is that it could happen at any time, and would be almost instantaneous—painless, efficient.The End Of Everything is our SciFri Book Club pick for April—you can join in on the community conversation and maybe even win a free book on our book club page. In this interview from 2020, Mack joins Ira to talk about the diversity of universe-ending theories, and how cosmologists like her think about the big questions, like where the universe started, how it might end, and what happens after it does.Also, Nobel Prize-winning psychologist Dr. Daniel Kahneman died this week at the age of 90. His work turned many traditional ideas about economics upside-down, arguing that people often make bad decisions that go against their own self-interest. It’s something he continued to study throughout his career, and that he wrote about in the 2022 book Noise: A Flaw in Human Judgment. At the end of this segment, we revisit an interview from 2022 with Kahneman in remembrance of his long career studying cognitive biases.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

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