Red Shift and Big Bang Theory

• When a source of waves is moving towards a detector, what happens?

  The waves it produces are squashed together as it moves towards the detector , reducing the detected wavelength
• When a source of waves is moving away from a detector what happens?

  The waves it produces are spread apart as it moves away from a detector, increasing the detected wavelength
• When a source of waves moves towards a detector, the detected wavelength is reduced. When a source of waves moves away a detector the wavelength is increased. What is the name of this effect?

  The Doppler Effect
• Give an example of where the doppler effect is noticeable

  The doppler effect is noticeable with sound waves produced by cars - the pitch appears to change if the car is travelling towards or away from an observer
• The doppler effect happens with light in terms of the red shift. Explain what the red shift is

  If a source of light (e.g. a star or galaxy) is moving away from an observer, the wavelength becomes longer and therefore redder
• Complete the statement - The faster the source of light is moving away from an observer:

  The greater the observed increase in wavelength and so the greater the red shift
• Explain the observed red shift from distant galaxies

  The further away a galaxy , the greater the red shift (As there is an observed increase in wavelength)
• What do red shift observation from distant galaxies tells us about the universe?

  Galaxies are moving away from each other , which means the universe is expanding
• The red shift provides evidence that the universe is expanding, and so supports what theory?

  The Big Bang theory
• What did the Big Bang Theory propose?

  It proposes that the universe began from a very small region that was extremely hot and dense
• Why is very little known about the universe?

  The universe is so vast and observations are difficult
• From 1998 onwards, what do observations of supernovae suggest?

  Distant galaxies are receding ever faster and the rate of expansion of the universe is increasing
• Scientists do not know how the increase in expansion of the universe is happening. They have suggested it is linked to dark matter and dark energy , but little is known about these phenomena so more observations are needed for a theory to be agreed