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World 3 · Redshift and Hubble's Law · 14 min · PRO

The distance ladder: how do we know how far?

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World 3: Redshift and Hubble's Law is part of PRO

The first world of Cosmos: Big Bang to Now is free. PRO opens the other 25 lessons in 6 worlds — simulations, quizzes and all.

  • Stretched light: Doppler vs cosmological redshift
  • Reading redshift in a spectrum
  • The Hubble-Lemaître law: v = H₀ d
  • The Hubble tension: two numbers that disagree
  • A hot, glowing young universe: recombination
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