StarTalk Radio: Cosmic Queries - Flat Universe Host: Neil deGrasse Tyson | Co-Host: Chuck Nice | Release Date: August 12, 2025
In the August 12, 2025 episode of StarTalk Radio, astrophysicist Neil deGrasse Tyson teams up with his co-host Chuck Nice to delve into a series of intriguing listener-submitted questions under the segment "Cosmic Queries". This episode, aptly titled "Flat Universe", explores a wide array of scientific topics ranging from quantum physics to the shape of the cosmos, all while blending humor and pop culture references.
1. Quantum Particles: Gluons vs. Gravitons
Listener: Jordan Senarth from Boston | Timestamp: [03:08] - [05:32]
The episode kicks off with Jordan Senarth's question about the nature of gluons and gravitons compared to photons. "A photon, because it has no mass, must then be pure movement, momentum, or energy," Jordan posits, prompting a detailed discussion from Neil.
Neil explains that gravitons are hypothetical particles associated with gravitational waves, and although not yet detected, they are essential in the quantum gravity framework. "The gluon is the mediating force of baryons and quarks within the nucleus of the atom," Neil clarifies, emphasizing that gluons hold protons and neutrons together despite their repulsive electromagnetic forces. Both gravitons and gluons, unlike photons, embody particles with mass-energy equivalence, as described by Einstein’s famous equation E = mc².
2. Gravity of Small Masses: CO₂ Molecules Orbiting a Person
Listener: Chuck Betlatch from Texas | Timestamp: [05:53] - [07:48]
Chuck Betlatch raises an intriguing question regarding localized gravity: "Can a small mass, such as a CO₂ molecule orbit a larger mass, such as a person?" Neil responds affirmatively, noting that while individual particles possess gravitational pull, the thermal motion of gases typically prevents such orbiting in practice. "You just give it the right speed at the right distance in the right direction, and there you have it," Neil elaborates, highlighting the delicate balance required for molecular orbiting.
3. Alien Communication and Time Systems
Listener: Larry Infante from San Antonio, Texas | Timestamp: [07:53] - [11:20]
Larry Infante critiques the portrayal of alien communications in science fiction, questioning the logic behind hostile aliens giving humanity a constrained time ultimatum based on Earth's 24-hour cycle. "If they said we'll be back in 47 gloops, that's not helpful," Neil notes, emphasizing that intelligent extraterrestrial beings would likely adopt a time system familiar to humans to facilitate communication. The discussion touches on human circadian rhythms and the inherent 24-hour cycle, reinforced by Neil’s reflection on experiments with human subjects living without natural light cues.
4. Pineapple on Pizza: A Humorous Interlude
Listener: Alex Row from Northeast England | Timestamp: [16:18] - [17:56]
Injecting a dose of levity, Alex Row poses the classic culinary debate: "Do you agree with pineapple on pizza?" Neil staunchly opposes the idea, "Pineapple belongs in a piña colada and not on a pizza," creating a playful exchange that underscores the show's signature blend of science and humor.
5. The Shape of the Universe: Flat vs. Spherical
Listener: Hugh Kaley from Richmond, California | Timestamp: [17:57] - [19:44]
Hugh Kaley seeks clarity on cosmological models: "If the universe is flat, does moving in a straight line bring you back to your starting point?" Neil confidently answers "No, you don't come back; it's forever," explaining that a flat universe lacks the curvature needed for such looping trajectories. He contrasts this with a positively curved, spherical universe where continuous straight-line movement would theoretically loop around back to the origin, similar to walking around the Earth. "It's got to have no edge," Neil summarizes, invoking Carl Sagan's metaphor of Earth's surface as "the shoreline of the cosmic ocean."
6. Time Dilation and Interstellar Travel
Listener: Joe Boone from New Zealand | Timestamp: [20:01] - [23:16]
Joe Boone's question intertwines relativity with science fiction: "In reality, wouldn't there be no travel time at light speed, making cryopods unnecessary for interstellar voyages?" Neil affirms Joe's understanding, "You get there as soon as you left," and chuckles at the notion of cryopods being a mere storytelling device. The discussion delves into the limitations imposed by physics, emphasizing that traveling at the speed of light remains theoretically impossible for objects with mass, thus reinforcing the necessity of cryopods within narrative contexts.
7. Neutron Star Material: Extreme Density and Its Implications
Listener: Lorraine Berdu from Montreal | Timestamp: [23:28] - [24:46]
Lorraine Berdu's imaginative query explores the properties of neutron star material: "Would Mount Everest come rushing out of a spoon if we brought neutron star material to Earth?" Neil debunks the scenario humorously, explaining that the immense density of neutron star matter "flattens everything," rendering the idea of mountainous structures rebounding on Earth implausible. "Neutron star flattens everything," he reinforces, illustrating the uncompromising nature of such extreme matter.
8. Energy in Water Dissociation: A Propeller's Motion
Listener: Emory from Florida | Timestamp: [24:54] - [28:34]
Emory presents a thought experiment comparing traditional water electrolysis with a novel method involving propeller-induced cavitation for hydrogen and oxygen collection. Neil emphasizes the fundamental physics: "Hydrogen and oxygen are very tightly bound," and dissociating water requires significant energy input. The discussion acknowledges the innovative idea but reiterates the energy-intensive nature of breaking molecular bonds, highlighting that any alternative method must account for energy conservation laws.
9. The Asteroid Belt and Planet Formation
Listener: Scott W. Peterson from Denver | Timestamp: [43:14] - [45:27]
Scott W. Peterson inquires about the potential for the asteroid belt to coalesce into a new planet. Neil addresses the historical context, referencing early planet discoveries like Ceres, Pallas, Vesta, and Juno, which were later reclassified as asteroids. "If you take all those fragments and glue them together into one object, you get something about 5% the size of the moon," Neil explains, assessing that the remaining mass is insufficient to qualify as a planet, thereby categorizing the asteroid belt as cosmic debris rather than planetary formation.
10. Many Worlds Theory and Universe Splitting
Listener: Tom Isaac | Timestamp: [29:38] - [31:33]
Tom Isaac delves into quantum mechanics with his question on the Many Worlds Interpretation: "Where does all the energy and matter come from to create new universes when the universe splits?" Neil acknowledges the complexity, stating, "The Many Worlds hypothesis is an attempt to make rational sense of something that's otherwise completely irrational." He candidly admits the speculative nature of the theory, noting that the practical origins of energy and matter in this context remain unresolved within the scientific community.
11. Universe Expansion: Observable vs. Total Universe
Listener: Mile Milkovsky from Macedonia | Timestamp: [31:38] - [33:24]
Mile Milkovsky seeks clarification on Neil's book statement regarding the universe's expansion: "Are we referring to the observable universe expanding or the total universe?" Neil concedes a degree of semantic looseness but confirms both interpretations are valid. "The expansion of the universe is the entire universe," he affirms, while acknowledging that discussions often focus on the observable portion due to the limitations of our telescopic vision.
12. Advice for Physics Majors Amidst Defunding
Listener: Jaden Peters from Utah | Timestamp: [47:03] - [51:08]
Jaden Peters voices concerns over the defunding of scientific programs and its impact on astrophysics majors. Neil offers both optimistic and pragmatic advice: "Science is going to be here no matter what," while stressing the foundational role of physics in understanding the broader scientific landscape. "Physics is foundational to... biology... chemistry," he asserts, encouraging perseverance and highlighting the timeless relevance of a physics education regardless of current political climates.
13. Galactic Rotation and Black Holes
Listener: Trisha Lynch from Beaverton, Oregon | Timestamp: [35:30] - [38:38]
Trisha Lynch poses a dramatic scenario: "What would happen if the Milky Way galaxy stopped rotating suddenly or gradually?" Neil responds with stark imagery, "Everything in the galaxy would fall into the black hole," explaining that the galaxy's rotation provides the necessary centrifugal force to counteract the gravitational pull of the central supermassive black hole. Ceasing rotation would result in unimpeded gravitational collapse, leading to a catastrophic convergence of galactic matter.
14. The Casimir Effect: Quantum Vacuum Phenomena
Listener: Monopoly World | Timestamp: [38:38] - [42:55]
Monopoly World seeks an explanation of the Casimir Effect. Neil provides a comprehensive overview: "You have two parallel plates of conducting material in a vacuum. Bringing them closer together creates an attractive force known as the Casimir force," he describes. This quantum mechanical phenomenon arises due to the restricted wavelengths of virtual particles between the plates, leading to a pressure differential that pulls the plates together. "It's a purely quantum mechanical phenomenon," Neil emphasizes, underscoring its lack of a classical analog and its significance in advancing our understanding of quantum field theory.
Closing Remarks
The episode wraps up with Neil and Chuck reflecting on the dynamic interplay between scientific inquiry and imaginative speculation. Their engaging dialogue not only elucidates complex scientific principles but also fosters a sense of wonder and curiosity about the universe.
Notable Quotes:
- Neil deGrasse Tyson at [03:08]: "The gluon is the mediating force of baryons and quarks within the nucleus of the atom."
- Chuck Nice at [14:23]: "Are there any signs we could theoretically look for to confirm that as our origin story?"
- Neil deGrasse Tyson at [24:46]: "Neutron star flattens everything, so we think neutron stars might be the best spheres in the universe because whatever's there just got flattened."
- Chuck Nice at [47:44]: "Einstein was gangsta. Time was defined to make motion look simple."
StarTalk Radio continues to inspire listeners by bridging the gap between complex scientific concepts and everyday curiosities, all while maintaining an entertaining and accessible format.
Stay curious, and as always, keep looking up!