The Metric System

and  Dunkirk  

 

Interpretive signs are big around the area now and they are very effective.  Most all of the distances are given in metric with no Imperial equivalent.  It appears that this limits some of the visitors experience.  The point in question today in the community was defining the gap in the Harbour of Refuge as 122  metres wide on a big sign..  The oldsters would be happy with 400 feet, but we need to measure it.

Most people think they know the metric system and hold up their nose at the old Imperial measure or what those backward mortals south of the border still use for distance, temperature and weight.  I don't think we should be so smug.  Here is why:

There is no official standard called the Metric System anymore.  It's known as Systeme International d'Unites or SI for short or in English (smile) International System of Units.

It has ONLY seven basic units of measure far less than the old and obsolete thing we call the metric system and far less still than the older Imperial System.  Here are the units.

Type Unit Name Symbol
length metre m
mass kilogram kg
temperature degrees Kelvin K
time second s
electric current ampere amp
amount of substance mole moll
luminous intensity candela cd

Notice there is no weight mentioned because mass which is unchanged on the moon or the earth, but weight is not.  So we make a big fudge and use weight for mass ignoring they mountains and valleys.

Here is another surprise.  What's this degrees Kelvin?  We use C for Centigrade, don't we?  The SI system does not recognize C.  In Centigrade zero degrees is freezing, but that's very imprecise, isn't it? Like 100 C is supposed to be boiling.  But that differs with altitude and purity of the water. 

Kelvin sets zero being absolute zero which is where all activity stops.  So if it's a sizzling  summer day in Toronto with 40 C, it would be 313 K.  104 F is very hot.

Also, notice that there is no base unit called a Liter.  It just exists as a combination of the unit m and the calculation of volume.

First Try at the  Metre.

The French in 1793 decided the  metre should be 1/10,000,000 of the distance from the North Pole running near Dunkirk and terminating at the equator.  The political force behind this was  Talleyrand

 

                  Talleyrand

 

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I wonder how many troops at Dunkirk knew that they were near the line defining the metre?

I can't think of any more obscure way to do it, can you?  Just imagine, these difficulties:

  • Nobody had been to the North Pole
  • Dunkirk was in France that's for sure.
  • Where the heck was the exact location of the equator?
  • What was the circumference of the earth?
  • How about bumps and flat spots?

They had a really artful way of estimating things and it really did not matter.  The thing that is bothersome is that the distance used as a base seems so ill advised and unrelated to human experience.

It seems that the  metre was more puzzling and far harder to measure than the Emperor's single stride.  But it did not matter much because they just cast a brass rod and called it a  metre's length.  Yup, just cast it up and name it and store it some place.  It seems that they could have taken Napoleon's or Tallyman's stride and had them strut back and forth  and all would have been fine.  They could have taken the average of 100 strides too  That's a nice number..

In order not to disturb everything metric they did the following things to fudge the original brass bar's length and bring things up to date without changing sheets of plywood at the lumber yard in France.

  • 1960 -- One  metre equals 1,650,763.73 wavelengths in vacuum of the radiation corresponding to the transition between levels 2p10 and 5d5 of the krypton-86 atom.  That's the spirit!  But where the heck is the North Pole?
  • 1983 -- One  metre equals the length travelled by light in vacuum during 1 / 299 792 458 of a second.  That's a little better, but where is all this vaunted times 10 stuff in that?  Yes, yes, I know.... now we just carve it up by tens and multiply it by tens.

So from trying to find the distance from the North Pole to the Equator and assuming a nice round globe, we've gotten to a universal constant called the speed of light.  Not bad.  They used absolute zero for temperature and that's pretty good too.

The rascals were stopped dead in the water when they proposed the 10 hour clock with a 100 minute hour and a 1000 second minute.  They also wanted a 400 degree circle.  The clock makers and followers of geometry did not want to change.  They could have