StarTalk Radio

Cosmic Queries – Quantumly Stupid

November 11, 2025

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  • A four-dimensional being observing three-dimensional creatures would see inside their organs, similar to how we can see inside a two-dimensional being's body. 
  • Space elevators, while technically conceivable, are currently considered impractical because the cost and efficiency of rocket-based space access (like SpaceX's) have significantly improved. 
  • Light can do physical work, as demonstrated by solar sails which use the pressure of reflected sunlight for propulsion, potentially accelerating probes to 20% the speed of light. 

Segments

Four-Dimensional Observation
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(00:02:57)
  • Key Takeaway: Four-dimensional beings would see inside the organs of three-dimensional creatures.
  • Summary: A question from a listener in Bucharest, Romania, prompts a discussion on observing lower-dimensional beings. If a 2D creature turns sideways to a 3D observer, it disappears due to having zero thickness. Conversely, a 4D observer would see directly into the internal organs of a 3D being, as the 3D skin encloses them like a line encloses a 2D being.
Space Elevator Feasibility
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(00:08:47)
  • Key Takeaway: Space elevators are technically conceivable but are now considered a solution to a non-problem due to falling launch costs.
  • Summary: The concept of a space elevator, as depicted in Asimov’s Foundation, is technically possible, requiring a tether to geosynchronous orbit (about 23,000 miles high on Earth). However, innovations in rocketry, particularly by SpaceX, have made access to space routine and cheaper, diminishing the need for this massive infrastructure project.
Alien Digestion and Waste
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(00:18:24)
  • Key Takeaway: An alien whose blood is acid could dissolve human flesh completely, potentially eliminating the need for digestive waste products.
  • Summary: A listener questioned whether an alien consuming human flesh with acid blood would produce waste. If the alien uses 100% of the food through direct molecular dissolution, it would not need to excrete waste. A plant-based alien, by contrast, would have oxygen as its waste product.
AI vs. Human Teaching Connection
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(00:20:36)
  • Key Takeaway: The human connection and the ability to intuit and readjust teaching methods for individual student needs remain essential beyond AI’s current capabilities.
  • Summary: While an AI could replicate a teacher’s knowledge and style, it currently lacks the capacity to intuit subtle changes in a student’s condition or maturity. True teaching requires the creative ability to repackage knowledge to reach a specific student’s curiosity, a skill tied to the ever-changing human condition.
Spacetime Curvature Restoration
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(00:23:05)
  • Key Takeaway: Spacetime curvature caused by mass/energy is expected to revert to a flat state once the mass/energy is removed.
  • Summary: The curvature of spacetime is a manifestation of the matter and energy within it; removing that matter and energy leaves no reason for the curvature to persist. The overall shape of the universe (open, closed, or flat) is a large-scale property distinct from local gravitational distortions.
Observing the Past in the Sky
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(00:24:50)
  • Key Takeaway: Looking at distant stars means observing light emitted long ago, effectively viewing the past, but this is the only interaction possible.
  • Summary: When observing a star millions of light-years away, we are seeing the light as it was emitted millions of years ago, meaning the star may no longer exist. However, this is the only way to interact with that distant light, so speaking of it in the present tense regarding the light reaching us is standard practice.
Time Travel Coordinates and Paradoxes
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(00:27:11)
  • Key Takeaway: Accurate time travel requires calculating not only Earth’s rotation but also the movement of the solar system and galaxy, and potentially the universe’s expansion.
  • Summary: To travel accurately through time and return to the exact point of departure, one must account for Earth’s rotation, the solar system’s revolution, the galaxy’s movement, and the expansion of the universe. Physicist Rich Gott suggests that time travel might be mathematically possible near black holes, though paradoxes like preventing one’s own birth remain a theoretical hurdle.
Galaxy Collisions and Black Hole Mergers
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(00:41:27)
  • Key Takeaway: Colliding galaxies pass through each other, and their central supermassive black holes will eventually merge in the resulting settled structure.
  • Summary: Galaxies are mostly empty space, so when they collide, the stars generally pass through one another in a cosmic ballet choreographed by gravity. As the system settles, the heaviest components—the supermassive black holes—sink to the center and merge, doubling their mass.
Spacetime as a Cosmic Lattice
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(00:48:03)
  • Key Takeaway: The idea that spacetime is a solid crystal lattice could explain time loops and suggests LIGO’s echoes might be fingerprints of this structure.
  • Summary: A listener proposed that spacetime acts like a crystal lattice rather than just a fabric, where defects could create natural time loops that resolve paradoxes. If spacetime is a lattice, the behavior of energy passing through it would depend on the direction of travel, similar to light in a crystal.