Galactic Redshift

• What does redshift in spectral lines indicate?

  Shift towards longer wavelengths

  
• How can redshift be observed?

  By comparing spectra from distant and nearby objects

  
• What realization did astronomers have after discovering redshift?

  Most galaxies are receding from Earth
• What does the expansion of the Universe imply about space?

  Space between galaxies is expanding
• How does the expansion of the Universe affect light waves?

  It stretches light waves towards red
• How can the expansion of the Universe be visualized?

  • Like dots on an inflating balloon
  • Dots move away from each other
  • Space stretches as the balloon inflates
• What relationship exists between distance and redshift of galaxies?

  Greater distance leads to greater redshift

  
• What does a greater degree of redshift indicate about a galaxy's movement?

  It moves away from Earth faster
• Which galaxies appear to be redshifted the most?

  The furthest galaxies
• What is the process to calculate the speed of a distant galaxy?

  1. Identify observed frequency \( f' \)
  2. Identify original frequency \( f \)
  3. Calculate change in frequency \( \Delta f \)
  4. Use Doppler redshift equation
  5. Rearrange for speed \( v \)
• What is the speed of light used in the calculation?

  $3.0 \times 10^{8} \text{ m/s}$
• What is the final calculated speed of the distant galaxy?

  $-1.5 \times 10^{6} \text{ m/s}$
• What does a negative relative velocity indicate about the galaxy's movement?

  It is moving away from Earth
• What does the observed frequency being less than the emitted frequency imply?

  The source is receding from Earth
• What should you keep track of in calculations involving redshift?

  • Keep track of minus signs
  • Indicates direction of movement
• Where can you find the speed of light value?

  In your data booklet