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Metrication matters - Number 49 - 2007-06-10

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

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Dear Subscriber,


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

Did anyone notice that the Metrication matters newsletter was four years old with Metrication matters edition number 48?

Guy Le Couteur wrote to ask, 'Shouldn't international metric day be on the thousandth day of the thousandth month?'

John M Steele wrote to add to the discussion that Bill Hooper and I had shared over the size of a tablespoon. To remind you, I had suggested that the tablespoon in the USA was a 'hidden' half-ounce but Bill Hooper disagreed.

John M Steele noted:

However, in the US all measuring spoons have been marked 1 Tablespoon/15 mL, and 1 teaspoon/5 mL for some time.

John referred to NIST Handbook 44 where Appendix C provides definitions of teaspoons and tablespoons on pages C18 and C19. The NIST Handbook defines the measuring cup as 8 fluid ounces exactly. It defines the tablespoon as 3 teaspoons exactly, 1/2 fluid ounce exactly, and 15 milliliters. It defines the teaspoon as 1/3 tablespoon exactly, and 5 milliliters adding that a teaspoon and a tablespoon are rounded to the nearest milliliter.

John then added:

5 mL and 15 mL is sufficiently accurate for any rational purpose, but teaspoon and tablespoon are defined precisely as rational integer ratios of fluid volume measure. If you pound through the chain of NIST Handbook definitions, 1 tablespoon = 231/256 cubic inches and 1 teaspoon = 77/256 cubic inches, and 1 cubic inch = (2.54 cm)^3, thus the exact conversion is more like 14.787 mL and 4.929 mL.

2 Editorial

People can learn about metric measures fairly quickly and easily. For example, it takes very little time to learn enough measuring units to build a house in Australia here they are:

1000 millimetres = 1 metre
1000 metres = 1 kilometre

1000 grams = 1 kilogram
1000 kilograms = 1 tonne

1000 millilitres = 1 litre
1000 litres = 1 cubic metre

1 metre x 1 metre = 1 square metre
1 metre x 1 metre x 1 metre = 1 cubic metre

However, it is the next step that proves crucial for most people as they decide to adopt metric units or not. This is the step of practice they have to do something with their new metric knowledge. This is why I strongly recommend that people measure themselves to memorise some metric measurements that they can then use as 'rules of thumb'. As examples:

  • My little finger nail is 10 millimetres across.
  • My long finger is 20 millimetres across.
  • My hand is 100 millimetres wide.
  • My hand span is 250 millimetres
  • My cubit (elbow to fingertip) is 500 millimetres.
  • On the day I was born I was a big baby at 4650 grams (average is about 3500 grams).

3 Oddities

On average a pencil can write a line about 60 kilometres long. This is enough 'line' to write almost 50 000 words.

Rainwater tanks have been mandated for all new South Australian homes from July 2006. The rainwater tanks must hold at least 1 cubic metre of rainwater. Tanks must be connected to at least one toilet, laundry cold water outlet or a hot water supply and be fed by a minimum 50 m2 of roof area. Systems will also need to include automatic switching between tank and mains water, mosquito control and backflow prevention devices. The South Australian Premier, Mike Rann, said: Adelaide is already leading the nation, with far more rainwater tanks per head of population than any other capital city in Australia. As the driest state in the driest continent in the world, we need to make the most use of our rainfall.

4 Tips

The range of a human male voice that retains some intelligibility in still air is about 180 metres.

5 Signs of the times

Phil Chernack wrote to say that he was watching 'Good Day New York' where a reporter went to the Entenmann's plant in Bay Shore. Phil wrote:

They were making crumb cakes and as the batter was being poured into the tins, the reporter said that it was 330 grams per pie. Later, after the pies were completed and ready for packaging, the reporter asked the floor manager about the final weighing process and was told that they need to make sure that the net weight matches the label which the reporter then said was 453 grams. She, of course stated some general terms in USC such as about 15000 lbs of crumbs are used, etc but when she did use metric, she did not do any conversion. In terms of manufacture, the factory appears to be metric. I guess I won't feel guilty about those chocolate-covered doughnuts anymore.

6 Quotation

Obstacles are those frightful things you see when you take your eyes off your goal. Henry Ford

If you don't know where you are going, you will probably end up somewhere else. Lawrence J. Peter

You might find the article, 'Setting SMAART metrication goals' useful for your work group or for your organisation. You can find the article at /articles.html

7 Q&A

Does the USA Mint use metric or customary measures for coins in the USA?

The USA Mint mostly uses metric units for coins in the USA. If you go to http://www.usmint.gov/about_the_mint/index.cfm?action=coin_specifications you will see that coins are measured in grams for their mass and millimetres for their thickness. However, the diameter of the coins is given in both metric units and also the customary measures of the USA. Of course the customary measures given here are based on the metric definition of an inch, which is 25.4 millimetres exactly.

8 Rule of thumb

A handy mnemonic for the distance to the horizon uses the first four odd numbers (1, 3, 5, 7) from a height of 1 metre the distance to the horizon is 3.57 kilometres.

It's a bit more complicated for other heights. For an observation from 4 metres high, you take the square root of 4 (= 2) and then multiply by the constant 3.57 (= 7.14 kilometres).

If you want to use this idea in a school, you might like to think of it as a part of a metric playground. You will find further ideas in the one-page article 'A metric playground' that you can download from /articles.html

9 History

In about 1400 England had developed a decimal system. This had 100 fathoms in a furlong and ten furlongs in a mile. It had a measure called a 'wand' that in modern terms would be about 1000 mm long, the same as the modern metre. An interesting use of this 1000 mm wand was to make a tun, which was a box one wand long, one wand wide, and one wand high close to a modern cubic metre. This was used to store dried grain for one family for a year. Each full moon you checked progress; if the level had fallen more than the width of a man's hand, rationing was required or the tun would not last till next harvest. Henry VI's advisers changed the developing decimal system in England back to non-decimal methods, somewhere around 1440. More complicated measuring methods have, throughout history, often replaced simple measures, presumably for commercial reasons.

10 Hidden metric

The National Weather Service in the USA calibrates all of their thermometers in degrees Celsius so that temperatures are 'traceable' to international standards. Then, before the temperature data is sent to any of the National Weather Service computers, all the temperatures are dumbed down to degrees Fahrenheit.


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.

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