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The Expanding Universe and Red Shift: Evidence for the Big Bang Theory

Explore the concept of the expanding universe and red shift, and how they provide evidence for the Big Bang theory. Learn about the Doppler effect, cosmic microwave background radiation, and the possible fates of the universe.

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The Expanding Universe and Red Shift: Evidence for the Big Bang Theory

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  1. ESS IS7 Notes 3

  2. Is the Universe expanding?

  3. What is red shift? Scientists examining the light emitted by stars observe dark lines in the spectrum. These dark lines are caused by different elements, such as helium, in the stars being studied. Edwin Hubble observed that the pattern of dark lines in light from distant galaxies is shifted towards the red endof the spectrum. This red shift suggests that distant galaxies are moving away from Earth and supports the idea of an expanding Universe. Red shift occurs because of the Doppler effect, which can be observed in sound waves and electromagnetic waves.

  4. What is the Doppler effect?

  5. How does the Doppler effect work in space? The Doppler effect means that sound moving away from an observer appears to be lower in frequency. The same thing happens with light from distant galaxies, which appears to be shifted towards the low frequency, red end of the spectrum. This means the distant galaxies must be moving away from the Earth. It has also been observed that the further away a galaxy is, the greater the amount of red shift. This means that very distant galaxies must be moving faster than closer ones – this is evidence for the Big Bang theory.

  6. What is the Big Bang theory? The observation of red shift is a key piece of evidence for the Big Bang theory about the origin of the Universe. This states that the Universe “began” withacolossalexplosion 13,700 million years ago and has been expanding ever since. The other key piece of evidence for the Big Bang theory is cosmic microwave background radiation (CMB). CMB is radiation remaining from the Big Bang explosion and fills the whole of the Universe. This radiation has cooled as the Universe has expanded andis now slightly less than 3 degrees above absolute zero.

  7. The Universe from beginning to end

  8. Check your understanding – slide one Objects giving off light 1. What direction is each object moving? 2. If you were located to the right of both objects, what color shift would each object’s light waves have? Object 2 Object 1 3. What is the name for what is going on with both objects’ light being emitted?

  9. Check your understanding – slide two 4. Why do scientists believe the universe started with an very big explosion? (give at least 3 pieces of evidence) 5. What are the three possible fates of the universe?

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