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Metrication matters - Number 3 - 2003-08-10


1 Feedback - notes and comments from readers 2 Editorial 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 Feedback

Nat Hager III, from the USA, was inspired to get out his old vinyl record collection to check my claim that they have been made in 250 mm and 300 mm sizes since the 1920s. Nat said, 'I got out one of my old LP's from the 1970s and measured it, and you're right!' (It was the exclamation mark that hurt – tee hee!)

Stan Doore, who works at the Smithsonian Institution, wrote: 'You have made the very obvious practical and useful observation that 1 mm of rain per square metre is one litre'. He then pointed out how easy it is to design tanks of the right size by noting that '27 500 litres of water is the same as 27.5 cubic metres and that this water has a mass of 27 500 kilograms or 27.5 tonnes'. Stan concluded by saying, 'This is why the SI (the modern metric system) was developed'.

2 Editorial

Throughout history, there has been a conflict between government regulators and commercial traders over the measurements we use. The traders have always wanted to diversify the number and sizes of measuring units while government regulators have sought to simplify and standardise units of measurement so that trading can be fair to all. Just before the introduction of the metric system, in the 1790s, the French people had to deal with 25 000 diverse measures, many with different names and different definitions – the 18th century traders had clearly gone feral. The modern metric system has a total of 29 unit names and these replace all 25 000 of the old ones.

3 Oddities

The unit tonne always measures mass; and it is always equal to 1000 kilograms. Before the tonne there were tons, and tons, and tons of tons. Here are some of them:

1 ton (coal equivalent) = 3 x 1010 joules*

1 ton (displacement) = 1 cubic metre*

1 ton (force)(long) = 9964.02 newtons

1 ton (force)(short) = 8896.44 newtons

1 ton (Imperial) = 1016.05 kilograms

1 ton (long) = 1016.05 kilograms

1 ton (oil equivalent = 4 x 1010 joules*

1 ton (refrigeration) = 3.516 85 kilowatts

1 ton (refrigeration) = 3516.85 watts

1 ton (register) = 1 cubic metre*

1 ton (short) = 907.185 kilograms

1 ton (TNT equivalent) = 4.2 x 109 joules*

1 ton (USA) = 907.185 kilograms

1 ton (volumetric) = 1 cubic metre*

* Approximation because of various conversion factors. I cannot know if this list is complete – there may be tons more tons of other kinds of old tons. Old 'tons' were used to measure mass, force, power, volume, and (at least) three different kinds of energy while the tonne only ever measures 1000 kilograms of mass. I am indebted to Dennis Brownridge of Arizona for much of this information.

4 Tips

When you walk into a room you can readily guess everybody's height using these steps. Look at a number of people – include males and females – and select a person of average height. In most cases (don't try this if you are at a basketball game) this person will be quite close to 1.7 metres tall. Use the width of your hand (about 0.1 metres) to guesstimate the heights of everyone else to within 0.1 metres. Just keep checking with the height of your chosen person; it's probably best not to tell your reference person how average they are!

5 Signs of the times

The correct symbol for kilogram is kg and the correct symbol for kilograms is also kg – with no 's' on the end. However, I have seen: Kg, kay-grams, KG, Kilo, KGs, kay, kilo, kilog, kgram, k-grams, kilos, kaygees, Kilos, k, kays, Kgs, K, or KGS.

6 Quotation

'Thanks to number, the cry becomes a song, noise acquires rhythm, the spring is transformed into a dance, force becomes dynamic . . .' Joseph Marie de Maistre (1753/1821)

7 Q&A

Q What is a metric building module? A Builders have always used components that have two properties. Firstly, the parts of a building have to be as big as possible to reduce the amount of labor in cutting and fixing them, and secondly, the components have to be small enough to be physically placed in position by a small group of people. Generally this has meant that building components, such as wall panels, have had a relatively consistent size for a long time. In pyramid building times, in Egypt, this building module was called 2 Royal cubits by 4 Royal cubits; in British Imperial times it was called 4 feet by 8 feet; and now, in modern times it is called 1200 millimetres by 2400 millimetres. All of these are quite close to the same size, but the last one is often called a 'metric building module'.

8 Rule of thumb

New born babies have a mass of about 3.5 kilograms and they are about 500 millimetres long. Little babies have a mass below 2.5 kilograms and big ones are more than 4.5 kilograms. Recently (2003 June), I heard of a baby who was born at 340 grams (0.34 kilogram) and 230 millimetres long – check her length on your metric ruler! She survived, and was allowed to go home from hospital when she reached 2 kilograms.

9 History

In 1585, the Flemish engineer and surveyor, Simon Stevin, published ‘De Thiende’ the ‘Book of Tenths’ in which he suggested the use of decimal numbers. He suggested a number of decimal systems for various activities, but, unlike the modern metric system, he made no attempt at coordination. Simon Stevin could see no reason why the following items could not be decimal immediately – in 1585.

  • Compilations of Land Meting – to be divided into decimal Rods and Perches.
  • Measures of Tapestry or Cloth – to be divided into decimal Ells and Poles
  • Measures of Liquor vessels –1 decimal Ame to be equal to 100 Antwerp Pots
  • Stereometry in General – to be divided into decimal Rods and Yards
  • On Astronomical Calculations – the circle to be divided into decimal angles
  • Moneymasters Merchants and all Estates in General – to be divided into decimal Pounds sterling, decimal Livres de gros and decimal Ducats.

This last suggestion by Simon Stevin eventually led to the worldwide use of decimal money. The New York Stock Exchange was among the last to change to decimal money – in 2001 – four hundred and sixteen years later.

You can get a taste for Simon Stevin's original text at http://home.planet.nl/~hopfam/ThiendeMenu.html and this includes a reference to Robert Norton's English translation of 1608.

In 1985, I visited Brugge in Belgium to honor the 400th anniversary of Simon Stevin's decimal achievements – with a Belgian beer in 'Place Simon Stevin' – sadly, I was the only one there. After 400 years Simon Stevin had largely been forgotten, even in his own home town.

10 Hidden metric

From a practical point of view aeroplane manufacturers know that – sooner or later – they are going to use metric units – so they have already done so – and then hidden them. Planes built in the last 10 years or so have electronic flight instrument displays that are built to operate according to ICAO (metric) rules. This practice also fits in with the fact that more and more planes are relying on the, satellite based, Global Positioning System (GPS) to find out where they are. The GPS, too, was designed and operates in metric units.

However, with the push of a button, all of the displays in the cockpit can have conversion factors applied, and have the electronic displays revert to old units. The altitude that was determined in metres and given in metres now appears in feet. The speed that was calculated in kilometres per hour and given in km/h now appears in knots. And payloads and fuel loads that were determined in kilograms now appear in pounds. All the original metric measures are hidden by electronic displays. I sometimes wonder what would happen if someone bumped the button that changes all the readings from the ICAO settings to the old USA values.

Pilot: 'Hey what are these mountain goats doing way up here in the clouds?'

Co-pilot: 'In flight school I learned that these kinds of clouds are called 'cumulo-granite.'

FX: Loud crashing sounds then silence!

All of this reminds me of the Gimli Glider incident, when a commercial airliner ran out of fuel, over Manitoba, because of confusion between kilograms and pounds. The twentieth anniversary of this event occurred two weeks ago (on 2003-07-26). This plane became famous in Canada as the 'Gimli Glider'. You can read Wade H Nelson's famous story about the Gimli Glider at http://www.wadenelson.com/gimli.html – it's fascinating stuff.


Pat Naughtin Geelong, Australia

Pat Naughtin is a writer, speaker, editor, and publisher. Pat has written several books and he has edited and published many others. For example, Pat was the lead writer of 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.

Copyright notice: © 2004 Pat Naughtin All rights reserved. You are free to quote material from 'Metrication matters' in whole or in part, provided you include this attribution to 'Metrication matters'. 'This was written by Pat Naughtin of "Metrication matters". Please contact for additional metrication articles and resources on commercial and industrial metrication'. Please notify me where the material will appear. Copying for any other purpose, whether in print, other media, or on websites, requires prior permission. Contact:

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