Metrication matters - Number 30 - 2005-11-10
Metrication matters is an on-line metrication newsletter for those actively involved, and for those with an interest in metrication matters.
1 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
7 Q&A - readers' questions and answers
8 Rule of thumb
10 Hidden metric
You might remember that http://ww2jerrycans.com/ has an interesting site on the history of 20 L 'Jerry cans' used for fuel and water during the WWII era. These cans were so successful that when the British and Americans copied the cans, they left the capacity at 20 litres. Several readers wrote to tell me that the 20 litre 'Jerry can' was consistent with the 200 litre drum as this is a neat decimal 10 times the size of the 20 litre Jerry can. The 200 litre drum is also widely distributed around the world; in the UK and other 'imperial' countries it is known as a '44' because 200 litres is about 44 imperial gallons and in the USA the 200 litre drum is called the 55 because 200 litres is about 55 gallons in the USA.
One of the truly great advantages of the metric system over all previous methods that have gone before is the ability to do all calculations without using fractions.
That's right, 'without using fractions' at all'.
The metric system sometimes has a use for decimal fractions but rarely does it have a need for common or vulgar fractions.
To use this feature of the metric system, you simply choose metric prefixes for your everyday activities that avoid any and all fractions. The example that I am most familiar with is the Australian building industry where they only use millimetres to measure even the largest buildings. To add or subtract numbers such as 9650 mm and 4315 mm you can do this simply and easily especially with a calculator.
I was reminded of this when I received an email about fractions from Bill Hooper in Florida. Note that a calculator would not be of much use with the problems that Bill proposes.
The problem with using common fractions (also called 'vulgar') is that, when they are used they invariably lead to the need to do arithmetic with them. If we need 1.5 kg of cheese for something and the grocery store has packages of 1/3 kg, 3/4 kg and 4/5 kg, what combination will give me about 1.5 kg that I need.
This leads to the necessity of teaching the arithmetic of common fractions (adding, subtracting, and even multiplying and dividing them), which is a royal pain in the butt and requires an inordinate amount of class time in our schools. Try adding '1 and 7/16' to '3 and 5/12'. (It's even hard to decide how to type those numbers; I've added the word 'and' in the hope of making their meaning clear.)
(However), in common use there is nothing wrong with using the words half and quarter (and three quarters). Little more needs to be known than that two quarters make a half. It doesn't take an extra year of school arithmetic classes to learn that. But learning how to manipulate the plethora of other combinations of common fractions DOES take that much extra time.
Teaching metric only and omitting both Olde English units AND the common fractions associated with them would save enormous amounts of time and money and effort in our educational system. That time and money and effort could be put to better uses.
Regular readers of 'Metrication matters' and regular users of the 'Metrication matters' web page at: http://www.metricationmatters.com will be pleased to know that you have helped to make http://www.metricationmatters.com one of the most popular 'metrication' web sites. If you use Google, MSN, or Yahoo to search for the word 'metrication' you will find http://www.metricationmatters.com listed in the top 10 on all three of these search engines.
When I learned that a pelican can hold up to 15 litres of water in the pouch on its lower beak it made me wonder about this old rhyme:
A wonderful bird is the pelican, / his beak holds more than his belly can.
It turns out that the pelican's stomach can only hold about 5 litres, so the rhyme is quite accurate. Apparently the pelican uses its large beak to scoop up a lot of water that also contains small fish; it then strains out the fish to swallow them without the water.
(By the way, a human stomach can normally hold between 1 litre and 2 litres, but it can be distended up to about 7 litres in extreme circumstances. When I researched this, I found out about Sonya, the Black Widow, at http://www.sonyatheblackwidow.com/ but I don't suggest that you go there. It is best not to know about some things.)
For years, I have estimated people's heights by knowing that the average person in a room is about 1.75 metres if they're male and about 1.65 metres if they're female. When I walk into a room full of people I scan until I find the average sized male and the average sized female, and then I use these people to guess anyone else's height. By the way, it is best not to tell your average measuring people just how average they are!
By the way, it is quite difficult to estimate people's height to much greater precision than about 50 millimetres or 0.05 metres; so if you are in a height guessing competition its best to keep your answers so that your guesses end with a zero or a five (and when in doubt round them up to the next highest 0 or 5 so that people will feel good about the height you guess).
This technique would also work in North America. Knowing that the average height of a North American male is also about 1.75 metres and a female is 1.65 metres you can quickly find the average height of people at a party and then estimate everyone else's height by knowing that the width of your fist is 100 millimetres or 0.1 metres.
Don't forget that there are many more tips in the articles that you can download freely from http://metricationmatters.com
5 Signs of the times
This month, the Midland Memorial Hospital in Texas, adopted the computer software system used by the U.S. Department of Veterans affairs, called the Computerized Patient Record System. This system supports the use of metric units only. Prescribers will no longer be able to enter apothecary or household units such as teaspoons and tablespoons as part of a medication order. In reporting this advance, Paul Trusten R.Ph., a pharmacist at the hospital first of all said 'Yay' quite loudly, and then added, 'This change is a few centuries overdue!'
Pierre Abbat, from Charlotte NC, reported that he went to a bike shop where he found that:
The dimensions of bike tires are metric and that the dimensions on the bike pumps are also metric. One bike pump was labelled: Bore: 31 mm, Stroke: 540 mm (actually that's the length of the tube, the stroke is 513 mm), and Volume: 410 cc (sic).
Fast is fine, but accuracy is everything.
Twenty years from now you will be more disappointed by the things you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbour. Catch the trade winds in your sails. Explore. Dream. Discover.
You have mentioned before that a military pace is 750 millimetres. How long should my normal walking pace be?
There is no definite answer to your question as everyone has a pace that has its own individual length. However, if you know the length of your own normal pace this information can be quite useful.
To find out the length of your own pace measure a length such as 100 metres; 10 metres or 20 metres will do, but 100 metres is more accurate. Count how many steps it takes you to walk this distance using your normal pace. (Tip: Find an athletics track where the 100 metres track is already marked out.)
Do this a few times until you are comfortable that your average number of paces is consistent. Finally divide 100 000 millimetres by the number of paces; this gives you your average pace length in millimetres.
Many people (mostly in the military but also in non-military occupations such as surveying) are taught to measure distance by counting their own measured paces. For more formal training in calibrating your step length go to: https://atiam.train.army.mil/soldierPortal/atia/adlsc/view/public/5161-1/accp/is0788/lsn3.htm and scroll down to '8 Determining Distance by Pace Count'.
For those of you who run, you might find that your running pace is quite close to one metre. However you will need to check this out for yourself. A friend of mine checks his running pace by running around a 400 metre track; he says that he is always within about half a pace of 400 paces for the 400 metre distance.
8 Rule of thumb
Phil Hall passed on an extension to an old rule of thumb that I have used here before. I said that a millimetre of rain falling on a square metre of roof would collect 1 litre of water. Phil added that 1 mm of rain is exactly 10 cubic metres of water per hectare. This is a useful rule of thumb for irrigators or for those who have to deal with floodwater.
Han Maenen from Nijmegen in the Netherlands recently posted a cautionary tale about how to read old records on the USMA mailing list. It appears that 'Dutch pound' is an old name for a kilogram and a 'Dutch ell' is an old name for a metre.
The Old Archive of Nijmegen grew slowly through the years, decades and centuries. The condition under which it was stored around 1830 was abysmal; it was stored in what was called the Trash Attic, an expression that shows the low regard for records at that time.
Then a civil servant and two city sweeps were assigned to reduce that archive. In the course of some years about 8500 Dutch pounds of records were destroyed. People nowadays tend to think that must be somewhat more than 4 metric tons. However, 'Dutch pound' was the official designation for kilogram in the 19th century, all authorities had to use the official measuring units, so this means that no less than 8500 kg or records went to the dogs. We will never know how many archival treasures were being lost. Probably many 'difficult to read records' were earmarked for destruction and carted off to their doom. But very often those are the most precious ones.
Now such wanton destruction is unthinkable; we have a state of the art strongroom, fireproof, secure, with 16 km (a pure co-incidence) of mobile shelving. We converted from fixed to mobile shelving recently, this caused a lot of inconvenience, as it made records and other materials inaccessible for a time.
The old unit names can still confuse people nowadays. A law suit about land for instance involving 19th century deeds: land measured in Dutch ells. Errors have been made during court cases as people thought that a 'Dutch ell' was about 70 cm; however, before metrication the ell was used only for cloth and in the 19th century the 'Dutch ell' was the official name for the metre. 100 ells was therefore not 70 m, but 100 m.
10 Hidden metric
When I was in the USA earlier this year, I noticed that the post office in the USA often uses limits such as 22 pounds, 44 pounds, and 79 inches. Quick calculations reveals that these are 10 kilograms, 20 kilograms, and 2 metres respectively. It looks like the U.S. post office is using metric units then hiding the fact that they do this from their staff and from the public.
Last month I tried to get your feedback on how you use 'Metrication matters' and on any of your thoughts that might help to improve 'Metrication matters' to make it more suitable for your purposes.
Unfortunately the computer code I used was the wrong sort for this newsletter I took it from a web page and it simply didn't work. I'm sorry if this inconvenienced anyone. So let me try again. This question is a deliberate attempt to provoke feedback and any of your thoughts that might be useful to share with other readers of 'Metrication matters'.
What do you think is the greatest problem preventing the final and rapid acceptance of the metric system worldwide?
Just send your response to with the words 'greatest problem' in the title.
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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 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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