Lesson 12, Topic 4
In Progress

Expansion Evidence

Lesson Progress
0% Complete
  • Light spectrum shift
    • i.e. Doppler effect
    • Occurs in all directions
    • Everything moving away
  • Helium-Hydrogen ratio
    • 25% He, 75% H (actual)
    • Matches Big Bang predictions
  • Cosmic background radiation
    • Gamow – predicted ‘background radiation’ from Big Bang
    • Penzias, Wilson – accidentally found/proved radiation
  • Not enough hot stars
  • Presence of radio galaxies, blue stars
  • Connection btwn. particle physics, cosmologies

Edwin Hubble

  • Californian Astronomer
  • During the 1920s, Hubble pioneered a technique to find the distance to other galaxies and showed that they were beyond our own
  • Discovered 20+ galaxies
  • Examining the light from stars in those galaxies, Hubble found familiar spectra of known elements (e.g. hydrogen, helium) but found all spectra were redshifted
  • Applied doppler shift to galaxies
    • Everything moving away
    • Further away = Moving away faster (found greater red shift)
    • Mathematically direct relationship
  • The reason behind this redshift is not that all objects are moving through the universe away from us, but rather that the universe itself is expanding, stretching the wavelength of travelling light.