8.2 Red-Shift

• What is the phenomenon called when an object emits waves and the wavefronts spread out symmetrically?

  Galactic Red-shift
• What happens to waves when the source of the waves moves?

  The waves can become squashed or stretched
• What is the effect of a moving object on the wavelength and frequency of waves?

  • Wavelength in front decreases (λ – Δλ)
  • Frequency in front increases
  • Wavelength behind increases (λ + Δλ)
  • Frequency behind decreases
• What is the Doppler effect defined as?

  Change in frequency or wavelength due to motion

  
• How does the Doppler effect affect light when an object moves towards an observer?

  The wavelength of light decreases

  
• What is the term for light that moves towards the blue end of the spectrum?

  Blueshift

  
• What happens to the wavelength of light when an object moves away from an observer?

  The wavelength of light increases
• What is redshift defined as?

  Increase in wavelength due to motion away

  
• What does light from a star moving towards an observer do?

  It is blueshifted

  
• What does light from a star moving away from an observer do?

  It is redshifted
• What do observers in different positions see regarding blue and red shifts?

  • Observer in front sees blueshift
  • Observer behind sees redshift

  
• What does redshift in light from distant galaxies indicate?

  Galaxies are moving away from us

  
• What does the observation of redshift from distant galaxies support?

  The Big Bang theory
• What is the relationship between the distance to a galaxy and its redshift?

  Greater distance means greater redshift

  
• What color of light has the longest wavelength in the visible spectrum?

  Red light
• How does the sound of a motorbike illustrate the Doppler effect?

  • As it approaches, pitch increases
  • As it moves away, pitch decreases
  • Frequency decreases as it moves away
  • Wavelength increases as it moves away
• What does the graph showing distance to a galaxy and redshift illustrate?

  Greater distance correlates with greater redshift

  
• When did the first observations of distant galaxies receding faster occur?

  In 1998
• What does the redshift of light from distant galaxies indicate about the universe?

  The universe is expanding

  
• What happens to matter during an explosion in the context of the universe's expansion?

  • Matter is densely packed initially
  • It moves out in all directions
  • Matter travels at different speeds
• What would happen if you traveled back in time regarding the separation of galaxies?

  They would be closer together
• How does the speed of galaxies relate to their distance from each other?

  Faster galaxies move further away
• What evidence suggests there is more matter in the universe than accounted for?

  • Rotation and motion of galaxies
  • Unseen matter is called dark matter
• What does the accelerated expansion of the universe suggest?

  It may be caused by dark energy
• What is the expected effect of gravity on the universe's expansion?

  Everything should come closer together
• What is the proposed role of dark energy in the universe?

  It pushes everything apart