StarTalk Radio

Cosmic Queries – Your God Is Too Small

February 17, 2026

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  • The speed of light ($c$) remains constant in a vacuum, but light appears to slow down in a medium because photons interact with molecules, which introduces delays that are mathematically modeled by the index of refraction. 
  • Total internal reflection occurs when light strikes a boundary between two media at an angle steep enough that it is entirely reflected back into the original medium, a principle utilized in optics. 
  • The discovery of gravitational waves using lasers (LIGO) is a profound scientific achievement, as Albert Einstein predicted both gravitational waves and the laser principle (stimulated emission) about a century before they were successfully combined for detection. 
  • The concept of a universe-sized black hole suggests that the accelerating expansion of our universe is not due to matter falling in, but rather the expansion of spacetime itself, and the ultimate end of cosmology would be reached when no new galaxies are revealed beyond the observable horizon. 

Segments

Optics and Evanescent Waves
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(00:01:26)
  • Key Takeaway: Evanescent waves during total internal reflection involve photons moving at the speed of light, but their interaction with the medium’s boundary prevents them from propagating normally.
  • Summary: The speed of light is a fundamental law, though it can be effectively slowed by a medium. When light undergoes total internal reflection (TIR), the interaction at the boundary creates an evanescent wave. This phenomenon is explained by the light’s waveform maintaining coherence as it passes through transparent objects, unlike translucent ones.
Light Speed in Media
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(00:03:49)
  • Key Takeaway: The apparent slowing of light in a medium is due to the photon’s constant speed ($c$) between molecules, punctuated by brief interactions where the light is absorbed and re-emitted by the medium’s molecules.
  • Summary: Light travels at $c$ in the vacuum between molecules, but interactions with molecules cause delays, resulting in a slower average propagation speed known as the index of refraction. The index of refraction ($n$) is calculated by dividing the speed of light in a vacuum by the speed of light in the medium ($v = c/n$). For diamond, with $n=2.4$, light travels at only 40% of its vacuum speed.
Total Internal Reflection Explained
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(00:12:29)
  • Key Takeaway: Total internal reflection is the critical angle at which light attempting to pass between two media is completely reflected back into the denser medium because the angle of incidence causes the light path to bend entirely backward.
  • Summary: When light crosses a boundary between two media with different indices of refraction, its path bends (refraction), which is why sunsets are visible slightly after the sun has set below the horizon. If the angle of incidence is made steep enough, the light never enters the second medium, resulting in total internal reflection.
Cosmic Mysteries and Life’s Existence
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(00:16:25)
  • Key Takeaway: The resolution of whether intelligent extraterrestrial life exists may not occur in our lifetimes, but determining if any life exists within our own solar system is a near-term possibility.
  • Summary: One host anticipates discovering the cause of the universe’s accelerating expansion, possibly involving pressure leakage from outside our universe. The other host believes finding life in our solar system (e.g., on Europa) is imminent, but finding intelligent life elsewhere is a longer shot. Discovering we are alone in the universe would be more profound and terrifying than finding alien life.
Theology and Cosmic Scale
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(00:19:47)
  • Key Takeaway: The idea that Earth is the sole object of God’s creation is logically inconsistent with the vastness of the universe, as it implies an inefficient creator who wastes time building trillions of galaxies.
  • Summary: The argument against Earth being unique centers on the inefficiency of a creator who would construct trillions of galaxies just to focus on one planet. This echoes the historical argument made by Giordano Bruno, who was executed for suggesting stars might have their own planets with life. Bruno’s final words reportedly were, “Your God is too small.”
Gravitational Waves and Measurement
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(00:26:12)
  • Key Takeaway: LIGO detects gravitational waves by measuring the differential stretching of two perpendicular laser beams, which cancels out the uniform expansion or contraction of space affecting both arms equally.
  • Summary: A gravitational wave washing over a measuring device would stretch all components simultaneously, potentially canceling out the measured effect if only one dimension were measured. LIGO uses two laser paths at right angles; when a wave passes, the path lengths change differentially, allowing the effect to be isolated and measured.
Einstein’s Prophetic Science
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(00:29:33)
  • Key Takeaway: Albert Einstein predicted the existence of gravitational waves in 1916 using General Relativity and, in the same year, published the foundation for the laser, which was used 100 years later to detect those waves.
  • Summary: Einstein published his General Theory of Relativity in 1915 and predicted gravitational waves a year later, though he doubted they could ever be detected due to their low energy. Coincidentally, in that same year, he published work on stimulated emission, the basis for the laser. The detection of gravitational waves using lasers in 2015/2016 highlights his extraordinary foresight.
Quantum Entanglement and Communication
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(00:31:24)
  • Key Takeaway: While quantum entanglement ensures instantaneous correlation between paired particles, it cannot be used for faster-than-light communication because the information state must already be built into the entangled pair, preventing the transmission of new, controllable data.
  • Summary: It is plausible that an entangled particle sent into a black hole could still instantaneously mirror the state of its external twin upon interaction. However, this mechanism fails as a communication tool because one cannot alter the pre-existing entangled state after the fact to send a new message (like turning left instead of right).
Relativity in Relative Motion
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(00:34:37)
  • Key Takeaway: In a cosmic void with no external reference points, two approaching spacecraft will each perceive themselves as stationary while measuring the other’s velocity and observing time dilation relative to their own clocks.
  • Summary: According to special relativity, if two objects are moving at a constant rate relative to each other in a void, neither has an absolute reference point to determine their individual velocity; both perceive themselves as stationary. Each observer will measure the other’s clock running slower due to time dilation, which is the only measurable effect of their relative motion.
Post-Human Dominant Species
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(00:38:16)
  • Key Takeaway: If humanity disappears, the book After Man suggests that highly adaptable mammals, particularly rodents, are likely candidates to evolve into large, dominant forms due to their size flexibility and ubiquity.
  • Summary: Mammals are uniquely capable of occupying nearly every ecological niche due to their ability to maintain constant body temperature, ranging from the tiny shrew to the massive blue whale. The absence of human predation would remove size limitations, potentially allowing species like rats to grow to human-sized proportions and dominate the terrestrial environment.