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THE FORMATION OF THE UNIVERSE

Unit 4: Cosmology

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COSMOLOGY

  • Cosmology is the study of the structure and evolution of the Universe as a whole
    • How big is the Universe?
    • What shape is it?
    • How old is it?
    • How did it form?
    • What will happen in the future?

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THE BIG BANG THEORY

  • The Big Bang Theory was first proposed in the late 1920’s
  • It states that there was an infinitely small, infinitely dense point that contained everything that is the universe
    • This small, dense, hot point is referred to as the singularity
  • The Big Bang is estimated to have occurred roughly 13.8 billion years ago

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THE BIG BANG: A POEM

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1. THE EXPANDING UNIVERSE

  • In the 1920s Edwin Hubble (astronomer) noticed that light given off by galaxies was shifted to the red end of the EM spectrum
    • Red Shift: Stars moving away from Earth shift toward the red end of the spectrum
    • Blue Shift: Stars moving toward Earth shift toward the blue end of the spectrum
  • This provided evidence that the universe is expanding and led to the proposal of Hubble’s Law

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HUBBLE’S LAW

  • The rate at which a galaxy is moving is directly proportional to its distance from us
  • In other words, the farther away a galaxy is from us, the faster it travels away from us
  • Big Idea: the universe is expanding

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2. COSMIC MICROWAVE BACKGROUND (CMB) RADIATION

  • Cosmic Microwave Background (CMB) Radiation: low levels of energy left over from the Big Bang distributed throughout the universe
    • 1965: 2 scientists found a mysterious microwave signal coming from all directions 🡪 this turned out to be CMB Radiation
    • After the Big Bang, the universe was EXTREMELY HOT (1032 K or 1 x 1042)
    • Current temperature is -270 °C
    • CMB radiation has cooled over time (13.8 billion years), but its presence suggests that it came from the Big Bang

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DETECTING CMB RADIATION

COBE

  • Cosmic Background Explorer (1989)
  • Probe that looked 15 billion light years into space to detect tiny temperature changes

WMAP

  • Wilkinson Microwave Anisotropy Probe (WMAP – 2001)
  • Captured the “glow” of the Big Bang by detecting temperature changes just like COBE
  • WMAP was much more precise

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3. COMPOSITION OF THE UNIVERSE

  • Composition of the Universe: most common elements in universe are hydrogen and helium
    • After the big bang, the first atom to form was a hydrogen nucleus, then as more began forming, some combined to form helium
    • Hydrogen still combines to form helium today through NUCLEAR FUSION
    • Nuclear Fusion takes place in the center of EVERY STAR IN THE UNIVERSE
    • Stars go through fusion until they run out of hydrogen, then they start making elements like carbon, neon, and finally iron
  • Most of our universe is still made up of hydrogen, helium, and the other elements up to iron

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