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• Sun's Gravity Bends Starlight
  Observations of stars near the Sun during the eclipse of 1919 show that the starlight bends just as predicted by General Relativity.
• Mount Wilson Astronomer Estimates Milky Way Ten Times Bigger Than Thought
  Astronomer Harlow Shapely finds that the Milky Way is 10 times bigger than previous measurements, using the period-luminosity relationship for Cepheid variables as discovered by Henrietta Leavitt.
• Sidebar: Why a Total Eclipse?
  Describes why observers needed a solar eclipse to make observations of starlight bending around the Sun.
• Expanding or Contracting?
  Einstein's theory of General Relativity predicts that the Universe cannot be static — it must be expanding or contracting. Einstein adds the "Cosmological Constant" to keep the Universe static.
• In Their Own Words
  Snippets of papers published by other astronomers during this time. The snippets here highlight the Cepheid period-luminosity relationship, redshift of galaxies, and the nature of spiral nebulae.

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