The Big Bang

The Big Bang Theory

13.75 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 at the Bell Labs, radio astronomers Amo Penzias and Robert 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 in every direction). 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. As space cooled, material condensed and atomic particles, then elements, molecules, stars, and galaxies formed. 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, and the expansion of the Universe ensued.

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 has 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
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3 thoughts on “The Big Bang

  1. I am a sophomore physics major, and I am writing a brochure that describes topics in physics at a middle school level. I was wondering if you would be willing to grant me permission to use the big bang image at the top of this page in one of my brochures? The brochures are not-for-profit and will be available through the Cornell synchrotron. Thank you!
    SIncerely,
    Sarah Marie

    • Hi Sarah Marie,

      I found that particular photo through Google. I believe the Big Bang photo is from scienceblog.com. If you search for Big Bang in Google images, it will be there. Since I made this blog for fun, I just noted on the home page that the photos are either from NASA or Google.

      Good Luck,
      Tina

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