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Homework Help: Converting light years to meters and miles

  1. Sep 25, 2011 #1
    1. The problem statement, all variables and given/known data

    A light-year is the distance that light travels in one year. Find this distance in both miles and meters.

    2. Relevant equations

    Speed of light (c) = 3.00x10^8 m/s

    3. The attempt at a solution

    10^15 m/s
    3.00x10^8 m/s

    That is to find meters...I think I can only find miles after I find meters by dividing that answer by 1609m

    Last edited: Sep 25, 2011
  2. jcsd
  3. Sep 25, 2011 #2


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    Staff: Mentor

    I think google could help you with this.
  4. Sep 25, 2011 #3


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    Homework Helper

    Where did 1015 m/s come from? and what are you doing/trying to do?

    You were told how far light goes in a second, how about a minute? Then how about an hour? a day? 365.24 days? [a year]

    Once you know how many meters, I wouldn't be multiplying by 1609. I don't think anything is more miles away from something that it is meters away from something! The end of my street is about 120 m away, but it is far less than even 1 mile.
  5. Sep 25, 2011 #4
    Right peter, I meant divide. Thanks for that.

    In the book where I get the problem from, it says 1 light year = 9.46 Pm (P being peta (15) and m being meters). I thought that was 10^15?
  6. Sep 25, 2011 #5


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    Homework Helper

    Yes, but then that makes the length of a light-year 9.46 · 1015 m. But if you know this, why divide by the speed of light? That would tell you the length of time it takes light to travel one light-year, yes?

    You are being asked to compute the length of a light-year, given that light travels at (very nearly) c = 3.00 · 108 m/sec . You need to work out the number of seconds in a year. (You may use the distance you looked up as a check...) You then need to convert this value from meters into miles.
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