The Big Bang Theory

The Big Bang Theory

About 14 billion years ago, the Universe was much smaller and hotter. In the 1960s, Robert Dicke predicted a remnant “glow” from the Big Bang. In 1965, radio astronomers Penzias and Wilson discovered that glow, named the cosmic microwave background radiation. The CBR was seen in all directions in empty space, with a black body curve (temperature ~3K). About 1 second after the Big Bang, the Universe was very hot, at ~1 billion K. At 3 minutes, protons and neutrons combine to form the nuclei of atoms. The hydrogen/ helium ratio (3:1) found today is about the same as what’s expected after the Big Bang. Atoms were “ionized” with electrons roaming free without being bound. At 300,000 years after the Big Bang, the Universe becomes transparent with a temperature of 3,000K. Light red-shifted by a factor of 1000.

Big Bang: Timeline

*Recent measurements show the Big Bang at 13.75 billion years ago. Scientists recently discovered dark energy; the Universe is not only expanding, but accelerating in expansion. So, earlier estimates of the age of the Universe at 15 billion years have been reduced to 13.75 billion years.

The Universe: Main Points

  1. Expansion of the Universe
  2. Cosmic Microwave Background
  3. Primordial Nucleosynthesis
  4. Evolution of Galaxies and Large Scale Structure Over 14 Billion Years

The Universe: Composition

  • 0.03% heavy elements
  • 0.3% neutrinos
  • 4% stars and gas
  • 25% dark matter
  • 70% dark energy