physics P1 (6)

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  • Created by: haidee
  • Created on: 02-05-12 19:45

The scale of the universe

  • Moon has a 3500km diameter
  • Earth has a 12500km diameter
  • Solar system has a 12 billion km diameter
  • Milky way galaxy has a 100000light years diameter
  • Universe has a 59 billion light years diameter
  • Astronomical distances are so huge that measurements of distance in kilometres are exceedingly large
  • So the unit of distance used is the light year which is the distance travelled by light in one year
  • Light travels at 300 000 000 m/s
  • One light year = 9 460 000 000 000 000m

Red and blue shifts

  • Light from moving objects will appear to have different wavelengths depending on the relative motion of the source and the observer
  • Observers looking at an object that is moving away from them see light that has a longer wavelength that it had when it was emitted (a red shift), while observers looking at an approaching source see light that is shifted to shorter wavelength (a blue shift)
  • By measuring the amount of shift to the red, we can determine the rate at which objects


Alex Nilsen


all so helpful Haidee, thank you so so much!! :):) from Lottie

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