StarTalk Radio: Cosmic Queries – Understanding Infinity with Stephon Alexander

Original Air Date: February 6, 2026
Host: Neil deGrasse Tyson
Guest: Dr. Stephon Alexander, Professor of Physics at Brown University
Co-host: Negin Farsad (Comedian and host of Fake the Nation)

Episode Overview

In this highly engaging and frequently comedic episode of StarTalk Radio, Neil deGrasse Tyson teams up with comedian Negin Farsad and theoretical physicist Dr. Stephon Alexander to tackle one of the biggest head-scratchers in all of science: infinity. Through a series of “cosmic queries” submitted by Patreon fans, the trio explores where infinity appears in mathematics, physics, and cosmology—diving into black holes, the expanding universe, string theory, the limits of our understanding, and the power (and peril) of mathematical abstraction. Expect playful banter, deep insights, and an unflinching look at the limits of science, sprinkled with metaphors about Tupperware, escalators, and jazz.

1. What Is Infinity? Childhood Encounters and Existential Angst

[03:02 – 09:39]

• Neil shares his first encounter with “infinity” at age five, grappling with the idea of JFK’s “eternal flame.”

  • “At age five, I was like, ‘What? Does this flame never go out? How could it never go out?’” — Neil deGrasse Tyson [04:04]

• Stephon Alexander confesses up front:

  • “Let me admit something to you and Negin—I don't know what infinity is.” — Stephon Alexander [05:55]

• Stephon explains the childlike realization that counting never ends and introduces the idea of infinity as “the number that goes on forever.”

  • “You realize you can just go on counting for eternity…there’s this number, it’s called infinity.” — Stephon Alexander [06:13]

Infinity in Math and Physics

• Using fractions, Stephon connects division by zero to infinity, explaining computer crashes:

  • “If I go smaller than one, which is…one over zero, that number goes…that’s what infinity is. We call that division by zero.” — Stephon Alexander [06:56]
  • “Computers crash, actually, because…these divisions by zero…what would happen?” [08:02]

• Negin brings up the emotional trauma of graphing asymptotes, which Neil describes as “they do touch at infinity.”

  • “I wanted them to touch—it just felt like a missed connection forever!” — Negin Farsad [08:45]
  • “They do touch at infinity. So get your ass to infinity and you’ll see them touch.” — Neil deGrasse Tyson [08:54]

2. Where Infinity Shows Up in the Universe

[09:39 – 20:48]

Physicists vs. Mathematicians vs. Philosophers

• Stephon notes that mathematicians “make a living from infinity,” philosophers obsess over it, but “we physicists try to run away from it.”
  • “We physicists try to run away from it, try to avoid it.” — Stephon Alexander [09:39]

Infinity as a Placeholder for Ignorance? (Fan Question: Captain James Riley)

[10:12 – 16:38]

• Does “infinity” just mean “we don’t know”?

  • Negin reads a fan’s question: Is infinity a cop-out? Is it real, or just a label for what we don’t understand? [10:12]

• Stephon uses black holes as a case study.

  • He describes how Einstein’s equations led to the prediction of black holes, which eventually were observed:
    • “A mathematical prediction…spat out…a black hole.” — Stephon Alexander [11:45]
    • The singularity at a black hole’s center produces “infinite density, an infinity in the forces, right, and an infinity in the curvature.” [14:24]

• Neil and Negin challenge: Is this physical, or a mathematical artifact?

  • Stephon explains, “Some people say…there’s some new physics we do not know. Some people say you have to accept the infinity, and…nature might be censoring our infinities.” [16:21]
  • “It could be that the infinity is the limit of the applicability of this theory.” — Neil deGrasse Tyson [16:26]

3. Can We “Tame” Infinities? Lessons from Quantum Physics

[20:48 – 32:42]

How Quantum Physics Fuzzifies the Infinite

• Stephon recounts how electromagnetism once predicted impossible infinite forces, but quantum mechanics “fuzzifies and softens” the problem.

  • “Quantum physics fuzzifies and softens…you just made up that word!” — Neil deGrasse Tyson [22:20]

• Explanation: Photon exchange (quanta of light) prevents infinite forces as particles get super close, showing quantum effects resolve some classical infinities.

Will Quantum Gravity Save Us from Black Hole Infinities?

• Stephon: Some physicists (e.g., Stephen Hawking, Lenny Susskind) hope a quantum theory of gravity, by analogy, “jumps in and saves the day” as we approach black hole singularities.

  • “What if…quantum gravity…as I go into the singularity of a black hole, you don’t get infinity, but you get new quantum effects.” — Stephon Alexander [24:20]

• But quantum mechanics and gravity are “very incompatible with each other…never reconciled their differences.” — Stephon Alexander [24:37]

  • Neil: “It’s like when I’ve tried to date a Pisces. It never works out.” [24:49]

4. Is the Universe Actually Infinite? (Fan Question: David)

[25:05 – 30:26]

• Patreon listener asks if the universe is “operationally infinite” (escalator metaphor)—and how multiverses fit in.

• Neil’s take: The universe can be finite but “you could just keep walking and never reach the edge,” just like on Earth—a sphere (surface) without a boundary.

  • “Don’t equate reaching an edge with something having to be infinite.” — Neil deGrasse Tyson [26:00]

• Embedding infinities: Two infinite sheets of paper in three dimensions can “both be infinite and never intersect,” so multiple infinite universes are no problem.

• Stephon adds: Even if the universe is finite, time (or expansion) can be infinite—think “a vampire that never dies.”

  • “You can have a finite world, but the clock can continue ticking for…infinity.” — Stephon Alexander [27:53]

5. String Theory, Music, and Infinity (Fan Question: Gavin Bamber)

[30:26 – 38:14]

• Question: Can string theory be represented by music? Would it be a composition that continues into infinity?

The Music of String Theory

• Stephon discusses why string theory appeals: It eliminates some mathematical infinities.
• It replaces point particles (which lead to infinities) with tiny vibrating strings. The vibrations correspond to different particles, analogous to musical notes.
  • “It’s not just any old string—the string, because it’s quantum, has to be vibrating…that generates a spectrum…what we know as a note, a tone.”
  • “String theory really does match on very nicely to the physics of how notes are generated in instruments.” — Stephon Alexander [36:02–37:54]

But…Does It Still Have Infinities?

• Quantum theories themselves can develop new types of infinities (ultraviolet and infrared divergences). But in string theory, “it is an infinity-free theory” if you allow for extra (10) dimensions.
• Neil: “There’s a catch.” [32:42]
• Stephon: “You can go and stuff infinities in those other dimensions.” [32:42]

6. The Human Mind, Infinity, and Jazz (Fan Question: anthropocosmic Dylan)

[38:14 – 41:32]

• Does infinity “make sense” to physicists, or do we force sense onto it? How does Stephon reconcile this gap in his research and through his jazz?

• Stephon: “I adhere to the Neil Principle—the universe is under no obligation to make sense to us…there is a sense in which we have to…embrace the infinities…try to sidestep it and make progress.” [39:02]

• In jazz, too, the process is messy, incomplete, and reliant on improvisation:

  • “You must try to break the rules and stumble and fall to make something new…embracing the mistakes…that’s what jazz improvisation is about.” — Stephon Alexander [40:04]

7. Loop Quantum Gravity, Pixels of Space, and Space-Time Explained (Fan Questions: Bruce Ryan, Abhinav Yadav)

[42:19 – 46:23]

What Is Loop Quantum Gravity?

• Stephon: It’s a framework proposing that the fabric of space-time itself is woven from quantum “loops”—like links in a chain, or “pixels of space.” [43:16]
  • “I can link a fabric of space-time with those loops…pixels of space.”

How Should We Think of Space-Time?

• Stephon describes space-time as “a very faint and invisible fabric…that can support ripples of itself (gravitational waves)…a very special type of medium.” [44:22–45:39]
• Neil: “However fantastical [these ideas] sound, they are still connected to reality in that important way.” [46:23]

8. Does Infinity Exist in the Physical World? (Fan Question: Malcolm Marfan)

[46:39 – 48:29]

• How do we know infinity isn’t just an abstraction? Neil recounts frustrations with the undefined status of “1 divided by 0” in math.

  • “If one divided by zero is undefined, why don’t you guys define it?” — Neil deGrasse Tyson [47:04]

• The episode closes with playful jokes:

  • Negin: “Can I just do a journal article right now and just be like, ‘1 divided by infinity is a bowl of jello’…?” [48:06]
  • Neil: “One divided by zero is an asymptote captured in Tupperware.” [48:16]

9. Notable Quotes & Memorable Moments

• “Nature might be censoring our infinities.”—Neil deGrasse Tyson [16:21]
• “When you embed infinities in higher dimensions, you got no problems at all.”—Neil deGrasse Tyson [26:00]
• “You must try to break the rules and stumble and fall to make something new…that’s what jazz improvisation is about.” — Stephon Alexander [40:04]
• “[The universe] makes no sense, but…these are just words we attach to equations. They make very good predictions and they work very well.” — Stephon Alexander [46:18–46:23]
• “However fantastical [these ideas] sound, they are still connected to reality in that important way.”—Neil deGrasse Tyson [46:23]

10. Engaging, Playful Banter

• Negin’s analogy of jazz and drinking:

  • “When jazz doesn’t make sense, I usually go to the bar, get another drink, and then jazz starts to make a lot of sense.” [41:15]
  • “That’s why jazz is in bars. That’s why all physicists and astrophysicists should be drinking when they talk about infinity.” [41:25]

• Stephon: “I always feel like the outsider physicist that played music. Turned out…the guy that won the Nobel for figuring out infinities…Ken Wilson…played the oboe.” [41:37]
  Negin: “It feels like something you just get saddled with in middle school.” [42:08]

11. Final Thoughts

• The episode ends with the acknowledgment that infinity remains both a mathematical tool and a source of deep philosophical confusion. Physicists often treat infinities as signals of unknown physics rather than “real” physical entities, preferring theories that “tame” or avoid infinities if possible. Whether existing in reality or merely in human minds, infinity—like jazz—might ultimately be “under no obligation to make sense to us.”

For Listeners:
This episode is a great primer into the big questions of physics, framed in a relatable and entertaining way—even if (as the hosts repeatedly admit) “it still makes no sense!” You'll come away with new metaphors, a few laughs, and a deeper (if perpetually incomplete) appreciation of infinity in science.

Key Segments & Timestamps:

• Introduction to Infinity: [03:02 – 09:39]
• Infinity & Black Holes: [10:12 – 16:38]
• Quantum Physics & Taming Infinity: [20:48 – 32:42]
• Is the Universe Infinite?: [25:05 – 30:26]
• String Theory & Music: [30:26 – 38:14]
• Infinity, Mind, and Jazz: [38:14 – 41:32]
• Loop Quantum Gravity & Space-Time: [42:19 – 46:23]
• Physical Reality of Infinity: [46:39 – 48:29]

Summary by StarTalk Podcast Summarizer AI, episode released February 6, 2026.