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Picture of the 2 lines on a platinum iridium bar

  1. Mar 2, 2012 #1
    Hello all,

    The standard meter was said to be the distance between two scratches on a platinum iridium bar.


    Where are these scratches? I only see the bar.
  2. jcsd
  3. Mar 2, 2012 #2


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    There doesn't appear to be a good picture on wikipedia. Perhaps some google searching would turn up something else?
  4. Mar 2, 2012 #3


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    I must say, I never thought of that before but those scratches will need to be VERY FINE for the standard length to be precise. You can probably only see them with a lens.
    When they are used for making or calibrating a sub standard, they 'know' pretty well where to look for these tiny scratches because they already have a 'crude' 1m measure. They can't 'lose them'.
  5. Mar 2, 2012 #4


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