Curiosity Weekly – "The End of the Universe"
Host: Dr. Samantha Yammine
Guest: Dr. Katie Mack (Theoretical Astrophysicist)
Date: January 14, 2026
Episode Overview
This episode dives into the ultimate fate of the universe, exploring current scientific theories on how it might all end, featuring an in-depth conversation with Dr. Katie Mack, theoretical astrophysicist and author of The End of Everything (Astrophysically Speaking). Alongside cosmic endings, the show delivers updates on recent discoveries in extremophile biology and groundbreaking research on the links between exercise and cancer outcomes.
Key Discussion Points & Insights
1. Frontiers of Life: The Fire Amoeba
[02:18 – 05:52]
- Topic: Discovery of the fire amoeba (Incendiaba cascadensis), a eukaryote thriving in extreme heat.
- Dr. Samantha Yammine outlines how this newly discovered organism from hot springs at Lassen Volcanic National Park challenges assumptions about complex life limits.
- Previous research suggested only simple organisms (bacteria/archaea) could withstand high heat; now, a eukaryote is proven capable.
- Potential future applications: Developing heat-tolerant proteins and enzymes, e.g., for industrial or consumer products like laundry detergent.
Notable Quote:
"This is like 20 degrees hotter than what we think humans or other mammalian cells can handle. So this is giving biologists a reason to rethink what might be possible for life here on Earth and beyond."
– Dr. Samantha Yammine [05:33]
2. Cosmic Endings with Dr. Katie Mack
[07:48 – 22:50]
a. On Meeting Stephen Hawking & Life as a Theoretical Cosmologist
[08:46 – 11:42]
- Dr. Mack shares her first encounter with Stephen Hawking at 14, and describes her career’s frequent returns to 'the blackboard culture' of theoretical physics.
- Work is more collaborative and interactive than most imagine—lots of brainstorming, chalkboard sessions, and expert discussion.
Notable Quote:
"My vision of a theoretical physicist when I was a little kid was a lone genius, sort of locked in a windowless room somewhere with a blackboard and no one to talk to... and that's not at all what it looks like."
– Dr. Katie Mack [09:59]
b. Connecting the Universe’s Beginning & End
[11:42 – 13:37]
- Exploring the universe’s "boundary conditions": The beginning and end provide crucial clues about fundamental physics.
- Some theories posit that the end of one universe could be the beginning of another (a cosmic cycle).
Notable Quote:
"If there's a particular kind of beginning or a particular kind of ending, that gives us clues that can illuminate the fundamental physics of the Universe."
– Dr. Katie Mack [12:30]
c. Fates of the Universe: Theories & Dark Energy
[13:37 – 17:29]
- Several possible endings: Heat death, Big Crunch, Big Rip—each tied to the nature of dark energy.
- Dark energy, a mysterious force, is causing the universe’s expansion to accelerate—contrary to what gravity alone would predict.
- Studying dark energy involves observing distant galaxies, supernovae, and the clustering of cosmic structures to trace expansion history and speculate on ultimate fate.
Notable Quote:
"Whatever it is, it seems to only really affect the expansion rate of the universe. Right. It changes how spacetime is evolving, but it doesn't bump into things or heat stuff up or whatever.”
– Dr. Katie Mack [15:30]
d. Timescales & Public Perceptions
[17:29 – 18:50]
- Even the most dramatic endings (heat death, Big Crunch, Big Rip) are trillions of years away—no cause for immediate worry.
- Dr. Mack's book addresses public misconceptions; the Big Crunch is no longer the favored model, with "eternal expansion" now better supported by current data.
Notable Quote:
“If we're headed that direction, then in a hundred billion years, everything interesting stops happening, basically. And then beyond that, you still have a long time before the ultimate heat death... don’t even worry about that.”
– Dr. Katie Mack [17:43]
e. Personal Motivations & Fun with Physics
[18:50 – 20:58]
- Dr. Mack is drawn to extremes (cosmic beginnings and ends) because they expose the most fundamental rules of reality.
- Her book aims to update public understanding and make these daunting ideas accessible, fun, and "vaguely thrilling."
Notable Quote:
"A lot of people had ideas about the end of the universe that are a little outdated... It's much more likely that the universe will never recollapse. It'll keep expanding forever. That fits the data better at the moment."
– Dr. Katie Mack [19:50]
f. Aviation, Astronaut Dreams & Hobbies
[20:58 – 22:50]
- Dr. Mack discusses how her passion for flying began with a childhood dream of being an astronaut, developing into a serious hobby during the pandemic.
Notable Quote:
"By the third or fourth lesson, I was, like, completely addicted, you know, listening to aviation podcasts, buying T shirts. That's awesome."
– Dr. Katie Mack [22:08]
3. Research Update: Exercise and Cancer Outcomes
[24:53 – 27:59]
- New studies (Yale & Princeton) using mice indicate that even voluntary exercise can significantly slow tumor growth by redirecting glucose—the "fuel"—away from tumors toward healthy muscles and the heart.
- Most striking results: Tumors nearly 60% smaller in obese mice with access to an exercise wheel versus sedentary peers.
- Prehab benefit: Mice active before cancer exposure fared even better.
- Gene expression changes mirrored those in human cancer patients who exercise, suggesting strong translation potential.
Notable Quote:
“Muscle and tumors both want glucose and exercise changes who gets it.”
– Dr. Samantha Yammine [27:37]
4. Bonus: Chalkboard Lore Among Physicists
[27:59 – 28:43]
- Light-hearted segment: Dr. Mack and Dr. Yammine discuss legendary "Japanese chalk," reputed to improve blackboard physics across institutes, with playful banter on chalk quality as a marker of academic culture.
Notable Quote:
"We couldn't possibly talk to the people. It would ruin all our ideas."
– Dr. Katie Mack [28:31]
Notable Quotes (Quick Reference)
- "This is giving biologists a reason to rethink what might be possible for life here on Earth and beyond." – Dr. Samantha Yammine [05:33]
- "In physics, we would call it the boundary conditions... that can give you some clues about what could be going on inside." – Dr. Katie Mack [12:05]
- "The heat death, if it happens, is so far in the future. Like, we don't even have words to talk about how far in the future that is. Like trillions and trillions and trillions and trillions..." – Dr. Katie Mack [17:43]
- "The idea here is that exercise changes the way the entire body distributes energy, tipping the scales so more glucose goes to the healthy muscle cells instead of tumor cells." – Dr. Samantha Yammine [27:34]
Timestamps for Key Segments
| Segment | Timestamp | |------------------------------------------------------------|------------| | Discovery: Fire Amoeba | 02:18–05:52| | Interview: Meeting Hawking & Life as a Cosmologist | 08:46–11:42| | Theories on the End and Beginning of the Universe | 11:42–13:37| | What is Dark Energy? | 13:37–17:29| | Timescales: Don’t Worry About the End! | 17:29–18:50| | Why Write About Cosmic Endings? | 18:50–20:58| | Flying, Astronaut Dreams & Hobbies | 20:58–22:50| | Latest Science: Exercise and Cancer | 24:53–27:59| | Physicists' Chalkboard Lore | 27:59–28:43|
Summary Tone
The conversation is lively, accessible, and playful, with Dr. Yammine and Dr. Mack making even daunting cosmic concepts engaging for non-specialists. They blend humor and wonder, use clear analogies, and never shy away from scientific nuance.
For more information about Dr. Katie Mack:
- Website: astrokatie.com
- Blue Sky: @astrokatie
- Instagram: @astrokatiemac
Production credits:
Curiosity Weekly is produced by Wheelhouse DNA for Warner Bros. Discovery. Host: Dr. Samantha Yammine.
Stay curious!