1912 US astronomer Vesto Slipher discovers the high redshifts of spiral nebulae, suggesting they are moving away from Earth at high speeds.
1923 Edwin Hubble confirms that the spiral nebulae are distant, independent galaxies.
1980 US physicist Alan Guth proposes a brief period of dramatic inflation in the early universe to produce the conditions we see today.
1992 The COBE (Cosmic Background Explorer) satellite detects tiny ripples in the cosmic microwave background radiation (CMBR)—hints of the first structure that emerged in the early universe.
The idea that the universe began with a Big Bang, expanding from a ...