- 1915: Albert Einstein considers the possibility of a cosmological constant in the field equations of general relativity
- 1922: Alexander Friedmann proposes the Friedmann equations
- 1929: Edwin Hubble observes that the universe is expanding
- 1964: Arno Penzias and Robert Woodrow Wilson discover the cosmic microwave background
- 1980: Alan Guth and Alexei Starobinsky propose a negative pressure field for cosmic inflation
- 1988: Michael Turner coins the term 'dark energy'
- 1998: Saul Perlmutter, Brian Schmidt and Adam Riess lead the High-Z Supernova Search Team and observe that the universe is expanding
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