StarTalk Radio

Cosmic Queries – Expanding Bubble Universes

January 13, 2026

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  • Sending nuclear material to the Sun would be ineffective for reviving it because the Sun operates on fusion, not fission, and sunspots alone are larger than Earth. 
  • The Big Bang is best visualized not as an explosion in space, but as the expansion of the surface of a balloon, where galaxies drawn on the surface move apart as it inflates. 
  • A generational spaceship mission launched today might be overtaken by later missions using superior future propulsion technology, though warp drives might allow for personnel transfer rather than outright overtaking. 

Segments

Movie Science: Saving the Sun
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(00:00:39)
  • Key Takeaway: Nuclear bombs are uncontrolled fusion, which is insufficient to restart the Sun’s core fusion process.
  • Summary: Sending Earth’s nuclear material to the Sun would be ineffective because the Sun runs on fusion, and human-made fission bombs cannot trigger sustained fusion in the Sun’s outer layers. The Sun’s fusion only occurs at its extremely hot core, where hydrogen converts to helium. Recycling existing hydrogen within the Sun by driving convection deep into the core could extend its life for trillions of years.
Temperature Measurement in Space
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(00:07:00)
  • Key Takeaway: Temperature in space is measured by the radiative energy (photons) hitting a thermometer, not the temperature of the surrounding ‘air’ which is absent.
  • Summary: On Earth, a thermometer measures the temperature of the surrounding air, but in space, there is no air to measure. A thermometer facing the Sun will register high temperatures due to radiative heat flux from photons. The side facing deep space will register the cold temperature of the cosmic background radiation.
Generational Ship Launch Timing
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(00:12:05)
  • Key Takeaway: Technological advancement might allow later generational ship missions to overtake earlier ones unless warp drives are employed for retrieval.
  • Summary: A key concern for generational ships is that propulsion technology may advance significantly during the long journey, allowing newer ships to pass the original vessel. If traveling at 20% the speed of light to Alpha Centauri (4 light-years away), the trip would take 20 years. The hosts suggest that if warp drives are invented, the solution would be to pick up the original crew rather than letting the new ship pass them.
Big Bang Diorama Visualization
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(00:18:08)
  • Key Takeaway: The Big Bang is best visualized using an inflating balloon model, where the 3D surface represents space and the inflation represents time.
  • Summary: The Big Bang is not an explosion within existing 3D space, but rather the expansion of space-time itself. For a child’s diorama, galaxies should be drawn on a large balloon, and as the balloon is inflated, the galaxies spread apart, illustrating the expansion of space over time.
Relativity and Shrinking Objects
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(00:19:39)
  • Key Takeaway: As an object approaches the speed of light, observers measure it shrinking only along the direction of motion (front to back), not in all dimensions.
  • Summary: An object traveling near the speed of light does not shrink in all dimensions; only its dimension parallel to the motion is measured to contract by external observers. Traveling at the speed of light requires zero mass, as massive objects would attain infinite mass and zero volume, which is impossible for material substance.
Black Holes and Universe Expansion
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(00:30:30)
  • Key Takeaway: The lack of observed matter influx does not contradict the possibility of living inside a black hole, as not all black holes are actively consuming matter.
  • Summary: If the universe were inside a black hole, matter influx would only be visible if the black hole were actively feeding, like a quasar. Supermassive black holes take an immense time (10^100 years) to evaporate via Hawking radiation. The concept of dark energy/matter being another passing bubble universe is an intriguing, though likely incorrect, explanation.
Warp Drive Acceleration and Speed
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(00:32:28)
  • Key Takeaway: A subluminal warp drive can simply be dialed down from a faster-than-light setting, similar to adjusting a car’s speed.
  • Summary: The Alcubierre drive, which warps space, is fundamentally capable of subluminal speeds by reducing the warp factor, analogous to driving slower than a car’s maximum speed. In Star Trek, impulse power represents speeds less than the speed of light (Warp 1), while warp factors represent speeds at or above light speed.
Black Hole Slingshot Mechanics
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(00:35:38)
  • Key Takeaway: A gravitational slingshot around a black hole will not increase speed because the energy gained from falling in is canceled by the energy required to climb out.
  • Summary: Gravitational slingshots gain speed by stealing orbital energy from a planet, which is not possible with a non-orbiting black hole. Falling toward a black hole and then attempting to climb out results in zero net change in velocity relative to the starting point. However, falling into a supermassive black hole’s event horizon is survivable initially because tidal forces are weak across its large radius.
Simulation Lag and Time Dilation
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(00:43:22)
  • Key Takeaway: If the universe is a simulation, time dilation could be analogous to frame rate drops in complex rendered areas, as the simulator only renders what is being observed.
  • Summary: In a simulated universe, the cosmic engine might slow down time in areas of high complexity (like near a massive object) to conserve computing power. The simulator would only need to render the environment immediately surrounding the observer, saving resources on unobserved regions like the Earth’s interior.
Faster-Than-Light Travel and Time
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(00:46:51)
  • Key Takeaway: Particles traveling faster than light (tachyons) would mathematically move backward in time, but no such particles have been observed.
  • Summary: While light slows down in media like water or glass, particles cannot be accelerated beyond the speed of light in a vacuum. Mathematically, any particle exceeding the speed of light would travel backward in time, known as a tachyon. Tachyons, if they existed, could only be detected at the precise moment their backward time path intersects our forward time path.