Astrophysics

• What is cosmic background radiation

  the electromagnetic background radiation leftover from the big bang.
• How is CMBR evidence for the big bang

  Appears to be the same in all directions

  Implies that all parts of the Universe were in contact a long time ago

  Microwave has increased as the Universe expanded

  Universe was significantly hotter a long time ago

  .:. Large explosion where energy was released (Waves of electromagnetic radiation)
• Define Redshift

  The fractional increase in wavelength OR decrease in frequency due to the source and observer moving away from each other
• Define the doppler effect

  The change in frequency / wavelength due to the relative motion between a source of sound / light and an observer
• Two properties which are observed to have changed due to the doppler effect

  Frequency, Wavelength
• Fill the gap - Doppler effect

  • When the source starts to move away from the observer, the wavelength of the wave broadens; 
  • For sound waves, sound therefore appears at a lower frequency to the observer; 
  • For light waves, the light shifts towards red due to its lower frequency; 
  • When the source starts to move towards the observer, the wavelength of the wave shortens; 
  • For sound waves, sound, therefore, appears at a higher frequency to the observer; 
  • For light waves, the light shifts towards blue due to its higher frequency; 
  • This is because red light has a longer wavelength than blue light; 
• Fill the gaps - red shift

  • After the discovery of Doppler redshift, astronomers began to realise that almost all the galaxies in the universe are receding; 
  • This led to the idea that the universe must be expanding; 
  • This caused the light waves to stretch out as they travel through space, shifting them towards the red end of the spectrum; 
  • The more shifted the light from a galaxy is, the faster the galaxy is moving away from Earth;