Picture of the 2 lines on a platinum iridium bar

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Discussion Overview

The discussion revolves around the physical representation of the standard meter, specifically the two scratches on a platinum iridium bar that define this measurement. Participants explore the visibility and precision of these scratches, as well as the availability of images and information regarding them.

Discussion Character

  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant inquires about the location of the scratches on the platinum iridium bar, noting that they only see the bar in available images.
  • Another participant suggests that searching online may yield better images than those found on Wikipedia.
  • A different participant comments on the precision required for the scratches, stating they must be very fine and likely only visible with a lens, and mentions the calibration process for sub standards.
  • One participant provides a link to a source that purportedly contains a better picture and technical details about the bar.

Areas of Agreement / Disagreement

Participants express curiosity and share information, but there is no consensus on the visibility or exact location of the scratches, indicating that multiple views and uncertainties remain.

Contextual Notes

There are limitations regarding the availability of clear images and the precision of the scratches, as well as the dependence on external sources for information.

fizagic
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Hello all,

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

http://en.wikipedia.org/wiki/Metre

Where are these scratches? I only see the bar.
 
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There doesn't appear to be a good picture on wikipedia. Perhaps some google searching would turn up something else?
 
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'.
 

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