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Metrication matters - Number 95 - 2011-04-10

Dear Friend of metrication,

Metrication matters is an on-line metrication newsletter for those actively involved, and for those with an interest in metrication matters.

You can read all previous issues at /newsletter if you scroll own to the bottom of the page. The latest revised of the Metrication matters web page is at http://www.metrictionmatters.com

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1 Editorial 2 Feedback - notes and comments from readers 3 Oddities - measurements from around the world 4 Tips - pointers and methods to make your measurements easier. 5 Signs of the times 6 Quotations 7 Q&A - readers' questions and answers 8 Rule of thumb 9 History 10 Hidden metric

1 Editorial

Happy birthday to you,

Happy birthday to you,

Happy birthday metric system,

Happy birthday to you.

On Thursday (2010-04-07) the metric system celebrated its 215th birthday as the legal "decimal metric system" for France.

Of the three components of the "decimal metric system", the "decimal" component came from the USA - actively promoted by the USA Ambassadors to France, Benjamin Franklin and Thomas Jefferson. The third "system" part was the invention in 1668, by John Wilkins in England, of applying his "universal measure" so it could be used for all measurements at all times. The word, "metric", was from an Italian translation of Bishop John Wilkins words, "universal measure" into "metro cattolico" that literally means "universal measure" by the architect Burattini.

The "decimal metric system" replaced all previous measuring words in France, of which there were many thousands. One writer suggested that there were sixty thousand different measuring words in France before 1789 just for mass (or weight); and many of these words had multiple meanings.

This French law of 1795 April 7 also made the franc, divided into 100 centimes, legal in France. Again this followed the USA model of dividing dollars into cents, as devised by Thomas Jefferson and George Washington and put into practice by Benjamin Franklin in the 1780s.

2 Feedback - notes and comments from readers

Many of you will recall that I decided to write to all the Members of Congress about the metric system.

Many of you will recall that you advised me against this saying that it would be a waste of time.

Well - I'm here to tell you - you were right and I was wrong.

My first attempt was to try to send all the Members of Congress an email. Did you know that almost all Members of Congress block their emails to people from outside the USA? Next, I decided to send a letter by snail mail. At $2.12 per letter for 541 Members of Congress my calculator got clogged. Finally, with loads of help from Carleton MacDonald in Washington DC, I sent a parcel of letters to Carleton, he stamped them, and then posted them to all the Members of Congress.

The result: nil, nix, nothing, zero, zilch. Not even a courteous, "We thank you for your letter ... "

Oh well, there won't be a next time. See /docs/MemberOfCongressLong.pdf

3 Oddities - measurements from around the world

One of the issues with old pre-metric words was the fact that they had no international coordination. As an example the Guz was an Indo-Arabic word for measuring lengths. A Guz was about 635 millimetres in Saudi Arabia, 940 millimetres in Bengal, 785 millimetres in Bombay, and 1040 millimetres in Iran. Now a metre is exactly 1000 millimetres in Saudi Arabia, 1000 millimetres in Bengal, 1000 millimetres in Bombay, and 1000 millimetres in Iran so these nations can confidently trade with each other.

4 Tips - pointers and methods to make your measurements easier

Body Mass Index

In any classroom it is easy to provide a set of scales in kilograms, a tape on a wall to measure height, and a simple cheap calculator. Next to these you could put a single page recipe for calculating your Body Mass Index maybe like this:

  • Put your body mass into a calculator (say) 74 kilograms
  • Divide this by your height (say) 1.75 metres
  • Again, divide this by your height (say) 1.75 metres
  • Push the = button
  • The calculator will now have your Body Mass Index (BMI) on its screen. In this example it reads 24.16326531 but you could round this to the nearest whole number of 24 so your BMI is 24 kilograms per square metre (24 kg/m2).

So what does this mean?

In the USA the averages are about 28 kg/m2 for men and 27 kg/m2 for women.

And what is good?

Nutrition magazines usually say that your ideal BMI is close to 22 kg/m2 for both men and women. As a comparison Miss America winners in the 1920s were close to ideal at 22 kg/m2. Then gradually this declined to a seriously underweight low of 17 kg/m2 in the 1980s. Since then it increased to 18 kg/m2 by 2000 and it is close to 19 kg/m2 by 2010. Maybe Miss America winners were brought up with a Barbie Doll that has a BMI of 14 kg/m2 that has not changed since 1959.

International guidance points for BMI are:

  • Less than 20 kg/m2: underweight
  • Between 20 kg/m2 and 25 kg/m2: Normal range
  • More than 25 kg/m²: Overweight
  • More than 30 kg/m2: Obese
  • Over 35 kg/m2: Morbidly Obese

Changing the subject - slightly - I began to think about what an all metric school might look like at some time in the future. To this end I wrote about a mythical school called the Optimal School and included this idea for a Body Mass Index (BMI) station. You can find this article at /docs/OptimalSchool.pdf and I would appreciate any comments you would like to make. Don't take it too seriously - it’s probably me living in a dream world.

5 Signs of the times

John Mercer, from Canada, sent me an email to let me know about the change of road signs in Canada. John wrote:

Hello Pat.
That was interesting what you said about the road sign change in Australia. In Canada the change from imperial road signs to metric happened over the Labour Day weekend in 1977. There weren't any more accidents after the change than before. The change went smoothly and the kilometre became part of the Canadian talk very quickly. I don't know if the anti-metric groups still try to tell the British people that if the UK changed to metric road signs there would be wide spread panic on the roads. If so the facts don't support it. Have a nice day.
John Mercer.

6 Quotations

Discovery is seeing what everyone else has seen, and thinking what no-one else has thought.
Albert Szent-Györgyi (winner of the Nobel Prize in Physiology or Medicine 1937)

7 Q&A - readers' questions and answers


Duncan Bath, from Ontario in Canada, wrote with some comments on the word "system". He wrote:

It seems to me that there is an inherent error in discussing the Metric System and the Imperial System as if it were a choice between more or less equals.

The error resides in the lack of "system" that is so evident in Imperial measures. Imperial is more a mismatched mixture of measures than it is any sort of a system. There are, undoubtedly, many other "imperials". Hell is the existence in that never-never land somewhere between all of the "Imperials" and the International System of Units (SI). What do you think?


You are right there are many, many, millions of old measuring words and many of these have multiple meanings. Miles is a good example; see http://en.wikipedia.org/wiki/Mile

Sometimes a few of these were put into arrangements called "systems". Examples are foot-pound-second, foot-poundal-second, foot-slug-second but none of these ever tried or pretended to be a system applicable "for all time' for all people" as the metric system is.

Your final thought about "Hell is the existence in that never-never land" (of metric conversion).

I agree that metric conversion is a "never-never land" and, in my opinion, no one should ever go there when they are trying for a smooth and fast upgrade to the full use of the metric system.

8 Rule of thumb

It amuses me how scientists sometimes put off making their upgrade to the metric system reasonable and rational. For example before the metric system was used by meteorologists and the medical community they noticed that their barometers went up higher than 30 inches and went down lower than 30 inches. Without any further thought they decided that the average air pressure was a nice round 30 inches. It was obvious really!

Then, when meteorologists and the medical community "went metric" with air pressure and with blood pressure all they did was to change 30 inches of Mercury to 762 millimetres of Mercury and then to round this down so that "Normal" pressure became a nice round 760 millimetres of Mercury. It sort of put a veneer of metric respectability to cover the 30 inches. It was obvious really!

Later meteorologists actually calculated what a nice round 760 millimetres of Mercury might be in units of the International System of Units (SI), the modern metric system. To do this they firstly made some assumptions:

  • the density of Mercury at 0 °C is exactly 13 595.1 kg/m3,
  • the acceleration due to gravity is exactly 9.80665 m/s2, and
  • you ignore the properties of the vacuum, including the vapor pressure of the Mercury, above the column of fluid.

You then use these assumptions to calculate the pressure exerted by 760 millimetres of Mercury like this:

13 595.1 kg/m3 x 9.80665 m/s2 x 0.760 metres = 101 325.014 4 pascals

Next you fly people from all over the world to hold a scientific conference that decides to round this arbitrary number based on a set of assumptions to 101 325 pascals or 101.325 kilopascals exactly.

Now doesn't that look so scientific? It was obvious really!

However, the number, 101.325 kPa, has no magic associated with it. It is simply an approximate conversion to SI units of the metric (but not SI) 760 millimetres of Mercury, which in turn is a rough approximation of 30 inches of Mercury. As I said, it seems that no one ever bothered to do any rational or even reasonable rounding when the conversion to SI was done.

And all the clever metrologists and medical scientists have done is hide the fact that barometers went up a bit higher than 30 inches and went down a bit lower than 30 inches and that 30 inches was a nice round number somewhere in the middle. It was obvious really!


A better way 1

Do a theoretical calculation based on the actual mass of the atmosphere and the surface area of the Earth.

  • Mass of Earth's atmosphere = 5.1480 x 10^18 kilograms
  • Weight of atmosphere = mg = m x 9.80665 m/s2 = 50.48463 x 10^18 newtons
  • Surface area of Earth = pi r2 = 4 x pi x (6.378 137 x10^6)^2 m = 511.207 8 x 10^12 square metres

By calculation the average pressure at sea level = 98.755 58 x 103 pascals (say) 98.756 kilopascals

A better way 2

Look at actual observations from around the world.

  • The highest air pressure ever recorded on a clear, very cold, day in northern Siberia (with temperatures around -50 °C) was 109.4 kPa.
  • The lowest pressure ever measured was 87 kPa inside Typhoon Tip in the Pacific Ocean.

The mid-point between these two observations is 98.2 kilopascals

The rule of thumb (finally!)

I think of normal air pressure as about 100 kilopascals. And I think of the range of air pressure as going from about 110 kPa as the highest possible with 90 kPa as the lowest air pressure.

9 History

In the 1800s, the USA acquired, from the UK, a copy of the UK Imperial yard and a copy of the UK mass of 1 troy pound. Both of these closely matched, within the accuracy limits of the measuring methods of those times, the UK standards. These became the primary standards for length (initially the Troughton bar, later bronze yard #11) and for mass (troy pound) for measurement in the USA.

These standards continued in use until about 1890 when the USA received primary metric system standards as a result of signing the Treaty of the Meter in 1875. In 1893, the Mendenhall Order changed the primary standards for the USA from the old pre-metric UK standard yard and troy pound to the new metric system standards of the metre and the kilogram. The USA has been fully metric since then.

10 Hidden metric

From the history item (above) we know that every citizen of the USA has used metric inches, metric pounds, metric yards, metric pints, and metric pounds, and so on since 1893. (But, shhh! There are roughly 309 000 000 citizens of the USA who don't seem to want to know this!)

These hidden measurements are one of the great lies of history. The USA is all-metric for all measurement, in all trades, crafts, and professions, all day every day and almost all the citizens of the USA don't know that they are all fully metric!) See /docs/MemberOfCongressLong.pdf

Pat Naughtin

Geelong Australia

Pat Naughtin is a writer, speaker, editor, and publisher. Pat has written several books and has edited and published many others. For example, Pat has written a chapter of a chemical engineering Encyclopedia, and recently he edited the measurement section for the Australian Government 'Style manual: for writers, editors and printers'. Pat has been recognised by the United States Metric Association as a Lifetime Certified Advanced Metrication Specialist.

Pat is the author of the e-book, Metrication Leaders Guide, that you can obtain from /MetricationLeadersGuideInfo.html

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