Author Topic: Metric History  (Read 1432 times)

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Offline smorgasbord

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Metric History
« on: May 28, 2022, 06:45 PM »
A fun bit of history on the definition of a meter: https://www.nist.gov/si-redefinition/meter


Offline SRSemenza

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Re: Metric History
« Reply #1 on: May 30, 2022, 12:17 AM »
Restarted this topic without the political content. Lets keep it that way.

   Thanks,

           Seth

Offline woodbutcherbower

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Re: Metric History
« Reply #2 on: June 07, 2022, 06:28 PM »
Sheesh. Why couldn’t they just use a tape measure?

Offline Bob D.

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Re: Metric History
« Reply #3 on: June 07, 2022, 09:13 PM »
LOL, they couldn't round that up to 1,650,754 ?  [big grin]
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Offline Cheese

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Re: Metric History
« Reply #4 on: June 07, 2022, 11:47 PM »
LOL, they couldn't round that up to 1,650,754 ?  [big grin]

Ya Bob they could...but then they'd be .27 wave lengths off and we now know what kind of serious issues that would present.  [smile]

Offline smorgasbord

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Re: Metric History
« Reply #5 on: June 11, 2022, 07:51 PM »
Sheesh. Why couldn’t they just use a tape measure?

I think it's interesting that the original definition was simply the length of a platinum bar kept in a climate-controlled basement in France. Problem was, anyone who wanted to ensure their meter bar/tape/whatever was correct had to go to great pains to get access to that hunk of platinum. And imagine trying to hold something up to that bar and dropping it or otherwise hitting it hard enough to change its length by even the slightest!

Then, in 1875, they made a new bar. This one had an "X" cross-section and instead of it being the exact length, it was longer but with two scribed marks to indicate the meter length, which had to be measured at the melting point of ice and standard atmospheric pressure. They also made 30 official copies that were distributed to enable companies to measure against them, somewhat more easily. The current standard is something that anyone with enough money can reproduce, so there's no dependence on a single source of truth anymore.

What cracks me up is that originally the meter was supposed to be 1/10,000,000 of the distance between the North Pole and the equator, but they screwed that up and so the real definition of a meter is actually 0.2mm shorter than it should have been. It's actually too bad that the meter wasn't defined as a whole number divided by the speed of light in a second. Then, for instance, the speed of light in a vacuum could simply be 300,000,000 meters per second.