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The Scale of the Cosmos
    •   “Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.”
    • -- Douglas Adams, The Hitchhiker's Guide to the Galaxy, 1979
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A light-year: Distance Not Time!
  • speed of light = c = 3.0 ´ 108 m/s


  • distance =   speed   ´   time
  • d =      c                     ´     t
  • light-second =  3.0 ´ 108   m/s     ´    1 s
    =  3.0     ´ 108   m
  • light-minute =  3.0 ´ 108   m/s      ´   60 s
    = 180     ´ 108   m
    =  1.8     ´ 1010  m


  • light-year      =  3.0 ´ 108   m/s      ´  3.14 ´ 107 s (i.e. 31.4 million s) =  9.4 ´ 1015  m
    =  9.5     ´ 1012  km
    =  9.5 trillion km
    =  9,500,000,000,000 km