StarTalk Radio Cosmic Queries – Total Darkness
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Apr 21, 2026 They tackle absolute zero, quantum limits, and why true darkness is so hard to find. They unpack photons, the cosmic microwave background, and how all matter still emits light. They debate whether galaxies orbit a grand superstructure and whether gravity is a force or geometry. They imagine ambitious telescopes on the Moon and ponder how much the observable universe weighs.
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Why Absolute Zero Is Unreachable
- Absolute zero is unattainable because quantum zero-point fluctuations keep particles in motion even after removing thermal energy.
- Neil de Grasse Tyson explains removing heat requires a lower-energy state to land on, so you can't extract usable energy from vacuum zero-point motion.
How To Dump Heat In Space
- Dump heat somewhere when cooling systems run; on Earth convection plus radiation moves heat away, in space you must radiate to open sky.
- Tyson notes spacecraft need radiators facing empty space because pointing radiators at each other defeats cooling.
Why The CMB Appears As Microwaves
- Everything at nonzero temperature emits photons; colder objects shift emission to longer wavelengths so 3 K objects emit microwaves.
- This shift explains the cosmic microwave background as relic photons from the Big Bang at ~3 K peaking in microwaves.