StarTalk Radio: Cosmic Queries – Dimensional Waterfall
Host: Neil deGrasse Tyson
Episode Release Date: April 15, 2025

Neil deGrasse Tyson, renowned astrophysicist and Director of New York's Hayden Planetarium, teams up with his comic co-host, Chuck Nice, in this engaging episode of StarTalk Radio. Titled "Cosmic Queries – Dimensional Waterfall," the episode delves into a series of listener-submitted questions, blending science, pop culture, and humor to explore complex astrophysical phenomena. Here’s a detailed summary of the episode’s key discussions, insights, and conclusions.

1. Gravitational Waves and Their Detection

The episode kicks off with a listener question from Writer's Eye, who inquires about the current state of tracking gravitational waves and the potential to map the universe's edge-to-edge through their detection.

Key Points:

• Gravitational Waves vs. Gravity Waves: Neil clarifies the distinction between gravitational waves (ripples in spacetime caused by massive objects like colliding black holes) and gravity waves (similar to sound waves in a medium).

  “[00:34] Neil DeGrasse Tyson: So gravitational waves. So we detect them when they wash over us.”
  “[01:12] Chuck Nice: Gravitational waves, Right.”

• Current Detection Methods: The discussion highlights LIGO's groundbreaking ability to detect gravitational waves, which earned the Nobel Prize, and the potential future research program aimed at monitoring pulsars to track gravitational waves more comprehensively.

  “[05:06] Neil DeGrasse Tyson: So here's what I learned recently. That, yes, we can detect certain energy levels of gravitational waves that wash over Earth.”

• Future Prospects: Neil and Chuck explore the ambitious idea of using pulsar timing arrays to observe gravitational waves passing through multiple pulsars simultaneously, which could allow scientists to map their propagation across space.

  “[06:27] Chuck Nice: Would see the consistency across each pulsar. Correct.”

Notable Quote:

“[05:15] Chuck Nice: Right.”

2. The Topology of the Universe

Maurice van der Linden from Harlem, Netherlands, poses a thought-provoking question about the universe's shape, asking if a perfectly 4D spherical universe would allow our line of sight to loop around back to our position, making the universe appear smeared across the cosmic horizon.

Key Points:

• Open vs. Closed Universe: Neil explains that current evidence supports an open universe that is expanding indefinitely, meaning sight lines cannot loop back to the observer's position.

  “[10:25] Chuck Nice: Right.”

• Cosmic Microwave Background (CMB): They discuss how the CMB has been scrutinized for repetitive patterns that would indicate a closed universe, but no such patterns have been found, reinforcing the open universe model.

  “[12:17] Chuck Nice: No, that's a great answer.”

Notable Quote:

“[10:25] Chuck Nice: Right.”

3. Higher Dimensions and Dark Energy

Igor Vihanik from an undisclosed location asks about the possibility that the expansion of our universe could be influenced by our 3D space interacting with a higher dimension, likening it to a waterfall falling into another dimension.

Key Points:

• Dimensional Interaction: Neil articulates that there's no evidence to support the notion of one dimension affecting another in the manner suggested. Using a 2D analogy, they explain how higher-dimensional objects interact with lower-dimensional spaces without direct influence.

  “[16:11] Neil DeGrasse Tyson: So there's no evidence that one dimension is susceptible to another dimension in that way.”

• Dark Energy Implications: While the idea remains speculative, they ponder whether phenomena like dark energy could, in theory, relate to higher-dimensional physics, though current understanding does not support this.

  “[20:35] Neil DeGrasse Tyson: So he was trying to account for the dark energy.”

Notable Quote:

“[16:00] Chuck Nice: Yes, send us some of that Croatian weed over here.”

4. Understanding Internal Structures of Planets

Stetson from Japan raises a question about how scientists determine the internal structures of other planets, given that direct observation is challenging.

Key Points:

• Scientific Inference: Neil explains that scientists use measurements of mass, density, and composition based on the periodic table to infer internal structures. For instance, Mercury's higher mass compared to its size suggests a significant iron core.

  “[24:32] Neil DeGrasse Tyson: Great question, great question. So we make educated Guesses. And then we test the guess.”

• Asteroid Composition: They also touch upon how studying asteroid densities helps in understanding whether these bodies are solid rocks or "rubble piles," impacting strategies for planetary defense.

  “[28:04] Neil DeGrasse Tyson: So how do you have rock that has less mass than rock?”

Notable Quote:

“[27:24] Chuck Nice: That's dope.”

5. The Arbitrary Nature of Magnetic Poles

Jared Higby from Alamo, Nevada, questions whether the north and south poles of a magnet are fundamentally different beyond their attractive and repulsive interactions.

Key Points:

• Arbitrary Definitions: Neil clarifies that the designation of north and south poles is a matter of human convention rather than an inherent difference in the universe.

  “[38:37] Chuck Nice: Do tell.”
  “[38:48] Chuck Nice: Aha.”

• Right-Hand Rule: The conversation delves into the right-hand rule used to define magnetic poles based on Earth's rotation and magnetic field orientation, emphasizing the human choice involved.

  “[41:04] Chuck Nice: Cause from where we're sitting, well, the.”
  “[41:35] Chuck Nice: Yeah, look at that. So that's it.”

Notable Quote:

“[38:48] Chuck Nice: Aha.”

6. Unexpected Discoveries by the James Webb Space Telescope (JWST)

Logan Sinnett from Phoenix, Arizona, asks about unexpected discoveries made by the JWST and which ones Neil finds most intriguing.

Key Points:

• Early Findings: Neil highlights the JWST's discovery of galaxies at a redshift of 14, which corresponds to the "Dark Ages" of the universe—periods before the formation of the first stars—which were previously thought to lack such structures.

  “[43:54] Neil DeGrasse Tyson: When I was coming up, there was the record for what's the farthest object in the universe?”
  “[45:00] Chuck Nice: Oh my gosh. 14. That's crazy.”

• Implications for Cosmology: These findings challenge existing models of galaxy formation and suggest that our understanding of the early universe may need to be revised.

  “[44:53] Chuck Nice: If steppally, you just have another axis that's up there?”

Notable Quote:

“[43:03] Neil DeGrasse Tyson: It would. We would know for sure whether there was life elsewhere in the solar system, not on Earth.”

Concluding Insights

Throughout the episode, Neil and Chuck seamlessly blend humor with scientific discourse, making complex topics accessible and entertaining. They emphasize the importance of scientific inquiry and the evolving nature of our understanding of the universe. From gravitational waves and cosmic topology to the arbitrary labeling of magnetic poles and the groundbreaking discoveries of the JWST, the episode offers listeners a comprehensive exploration of contemporary astrophysical questions.

Final Notable Quote:

“[43:03] Neil DeGrasse Tyson: It would. We would know for sure whether there was life elsewhere in the solar system, not on Earth.”

As the episode wraps up, Neil encourages listeners to continue their curiosity and stay engaged with the ever-expanding field of astrophysics.

“[45:40] Chuck Nice: Yes. That was great.”

“[46:10] Unknown Speaker 5: For all of life's adventures. The all new 2025 Chevrolet Equinox is the SUV to help you do it...”

Stay tuned to StarTalk Radio every Tuesday for more insightful and entertaining discussions about the cosmos. Keep looking up!