Red Shift

• What is a red shift?

  • An observed increase in the wavelength of light from distant galaxies
• Velocity : The further the galaxy is..

  • The faster they are moving
  • The greater the observed increase in wavelength
• What causes change in theories?

  • New evidence / observations that cannot be explained by the former theory.
  • New evidence that disprove current theories.
• What does the red shift provide evidence for?

  • Evidence that the universe is expanding
  • Supports the Big Bang Theory
• Greater wavelength 


  • Further away
• What information can scientists find out about a galaxy when they measure the size of the red-shift the galaxy produces?

  • Distance
  • Speed galaxy is moving
• How does red-shift provide evidence that the universe is expanding? 

  (3 points)

  1. Distant galaxies are red-shifted, showing that they are moving further away.
  2. Galaxies that are further away = moving faster.
  3. The Universe is expanding.
• Describe the Big Bang Theory

  1. At first, all of the matter in the universe was in one tiny point.
  2. This point was very hot and very dense.
  3. This tiny point began expanding and is continuing to expand. 
• Observations : Since 1998 onwards: Provides evidence that the galaxies are moving further away at an ever faster rate

  Observations of supernovae suggest that distant galaxies are receding/ moving away at a faster rate.
• What do we still not understand about the Universe?

  • Dark mass
  • Dark Energy
• How are theories developed?

  1. Use of observations
  2. Patterns in data
  3. These form predictions
• The ‘steady state’ theory :

  • The Universe has always existed.
  • It is continually expanding.
  • New galaxies are formed, as older galaxies die out.
• The fact that light from a distant galaxy seems to move towards the red end of the spectrum :

  • The Universe is expanding
• Explain, in as much detail as you can, the scientific evidence for the “big bang” theory of the origin of the Universe (5 marks).

  1. Galaxies show a red shift.
  2. But more distant galaxies show a bigger red shift.
  3. As galaxies move away, the Universe is expanding.
  4. But more distant galaxies move away faster.
  5. So all Universe once in one place.
• Compare the observed red shift of two galaxies, where one is further away

  1. The galaxy that is further away = travelling faster
  2. The observed greater red shift
• What two ideas could explain the universe's increasing rate of absorption?

  1. Existence of dark mass and dark energy that can't be detected.
  2. These cannot be fully understood by scientists and are still being developed.
• Prior to existence of supernovae, the rate of expansion of the universe was supposed to be slower : 


  • Gravitational forces would cause this to slow down