Astronomy (7.7-7.15)

The expanding universe 

Astronomy topic 7 (7.7 - 7.15)


Red Shift - Element present in stars

  • Light from stars does not emitt all wavelength as some are absorbed by elements in the star
  • So dark lines are present when spectrums of stars are analysed → so we can see what element are present in the star
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Red Shift - Galaxies + Speed

  • When the specrum of light from distant galaxies is observed dark lines show and increase in wavelength and decrease on frequency
  • Lines are shifted to red end of spectrum so it is called red shift
  • Most galaxies emitt red shifted light
  • The space between Earth and the galaxy is expanding and the light waves are being stretched on the journey
  • This shows that the galaxy is moving away from earth, the more red-shifted the light is the faster the galaxy is travelling from earth
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Theories of the Universe - Big bang theory

  • 13.8 billion years ago the universe was a very small, hot region of dense matter
  • From this point everything expanded into the universe today
  • Multiple peices of evidence to back this up
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Theories of the Universe - Evidence from Red shift

  • The further away a galaxy is the more red shifted the light from it is 
  • The further away the galaxy is the faster they are moving 
  • Similar to an explosion→ fastest pieces travel furthest
  • Provides evidence that the universe, including space itself, is expanding
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Theories of the Universe - Evidence from CMBR

  • Cosmic Microwave Background Radiation
  • Comes form all directions in space and has a temp of -270C
  • It is the remains of thermal energy from the Big Bang spread thinly across the while universe
  • Was discovered after a theory predicted it and is strong evidence of the Big Bang Theory
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Theories of the Universe - Steady state theory

  • Theory that the universe has always existed and is slowly expanding and creating matter over time.
  • It is supported by res shift but not CMBR and lost support after discovery of CMBR
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