UKMA’s Chairman received the following critical letter from a thoughtful correspondent (a student or teacher of physics). As it is better argued than most efforts from defenders of imperial measures, it was thought that it was worth publishing (slightly edited to conceal his identity) – together with Robin’s reply.

This was the original letter:

Dear Robin,

I must say, I’m suprised by the somewhat draconian arguments on the UKMA website that imperial units should be abolished altogether, especially when imperial units have not even been taught in schools for about 30 years. I write as somebody who grew up under the metric system (though exposed to imperial units at home), who used to think everything should be SI, and through experience now realises that the imperial system has a lot to offer.

Fundamentally, there is no reason to adopt any one unit over another, by virtue of the definitions, e.g. the metre is determined by the ratio of 1/(speed of light in m/s) – it could equally be defined in feet (speed of light feet/s). The choice is ultimately for consistency in scientific publications and engineering (and international trading), but there is no reason not to keep it in existence for everyday usage for a number of reasons (and in the same way most foreign people speak English as a second language, but still have their own mother tongue – thus exposed to 2 different ways of thinking). Indeed some of the arguments against imperial actually suggest the very reason why imperial should not be scrapped, but perhaps, with the exception of the Farenheit scale, be re-introduced! Metric units are not even rigidly adhered to in physics, where we revert to units that most conveniently relate to the scales of observation, for example energy in units of eV (the electron-volt) when talking about atomic energy structure, mass in terms of “atomic mass unit” for atoms, or “solar masses” in astronomy (yes there was the classic metric-imperial mistake at NASA on the Mars orbiter, which could have been avoided with a standard international unit, but that is not the argument here).

1) As your site mentions, many people use imperial units in describing length and height: it is precisely because the very origin of imperial units of length – derived from everyday objects – that it is so much more intuitive to use. What’s easier – describing somebody’s height in feet and inches, or in m / cm?

2) Numeracy skills in this country are at an all time low – now why could that be? Imperial measures, by virtue of not being very simple to use, force people to think about numbers and fractions. All units are ratios in one form or another, thus by maintaining the presence of fractions in the notation, we are reinforcing the fundamental nature of measurement; that what quantity you are specifying is not really an absolute number, but a ratio with respect to some pre-defined unit – the basis of which is arbitrary (and on this point, the foot is clearly an easier unit to estimate without a ruler than a metre). The specific ratios also being arbitrary – yes 10 makes it easier, but is no more correct than divisions of a foot by 12, 24 (half an inch) 48 (quarter of an inch) 96 (eigth of an inch) and so on (and here we can see the nice power of 2 relationship) – it is purely convenience, a convenience which encourages laziness in thinking and loses sight of the fundamentals, and consequently a severe dumbing down in science at schools, so that now the only bit of real maths a pupil is given, in the advanced GCSE science questions, is the “equation” for speed, which they are actually given – something which even when I did GCSEs in the 1980’s was expected to be known by heart even by the 2nd year, and was certainly not worthy of “advanced GCSE” status. What next – decimalise the byte?

3) Base 12 is more flexible than base 10, as with 16 ounces in a pound 12 is divisible by 1,2,3,4,6.

10 is divisible by 1,2,5.

5ths are less useful than 4ths and 3rds. And mathematically, base 12 is much nicer than base 10, you are less likely to end up with recurring reciprocals like 3.33333~ if wanting to divide a given length of something into an integer number of sections.

I think that to say everyday measurements in this country are in a muddle is slightly misleading – most of us know what these units mean, having grown up with both – it is only pedantism over having a consistent set of units, where in everyday situations this is not so important. The only circumstance where I can think that the imperial system is a muddle is in the vagueness of plumbing fittings, where for e.g. thread fitting diametres are not actually based on the thread diameters, but on the inner-section of pipe that might pass through them. Ultimately, I feel let down by this country and our declining education system for not having taught both imperial and metric units, irrespective of the need to have one international standard.

Cheers

[name withheld]

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and this was the reply:

Dear zxzxzxzx

Thank you for your comments, which I read with interest. I am not able to reply in full detail but would make one or two brief points.

As you say, because the Government started the metrication process in 1965 and then lost its nerve and has effectively abandoned the whole project, we are now in a situation where both the metric system and imperial units are in widespread use. The problem with this is that most people do not have a secure grasp of either system – let alone both. This does create genuine problems of incomprehension, conversion errors, mistakes and accidents – and in some cases actual costs of having to run both systems – one for internal transactions and another for the public interface. Take a look at our blog article http://www.metricviews.org.uk/2007/10/15/whats-wrong-2-systems/ for further comment. (You are welcome to contribute yourself).

It is quite untrue that imperial units are “intuitive” or natural. How long is your foot? What I think you mean is that imperial units are familiar – just as it is “natural” to speak English. People brought up in metric countries do not think imperial units are “intuitive”. See also blog article http://www.metricviews.org.uk/2007/10/28/imperial-units-natural/ which includes comments from a German and a Dane on this point.

The argument about the advantages of base 12 are academic rather than practical. There is no prospect of converting the world’s counting system from decimal to duodecimal, and it is obviously sensible that the measurement system should be aligned as far as possible with the counting system. In any case imperial units are mostly not to base 12: 16 oz in 1 lb, 14 lbs in a stone, 8 stones in a cwt, 8 pints in a gallon, 3 ft in a yard, 1760 yds in a mile, 43 560 sq ft in an acre. How would you divide a lb or a mile by 3?

The evidence on numeracy skills is patchy, and even if it were true that numeracy skills have declined, this would be more likely to be due to other factors such as flaws in the national curriculum, poor maths teaching and the prevalence of pocket calculators and computers and the general dumbing down of mental processes – e.g. “satnavs” replacing map-reading and navigation skills.

UKMA’s proposals are not particularly draconian. Indeed, they are the method by which Australia, New Zealand and many other countries successfully made the change. Unfortunately, UK governments have adopted policies that are the opposite of those proved to be successful – which is why we are in the present muddle.

At least I think we can agree that successive UK governments have let us down.

Best wishes

Robin Paice

Of course most imperial measurements originally related to natural everyday objects. This was the natural progression in the history of science. The point is that nowadays measurement is a much more complex affair, with such a vast number of things we are likely to measure that it is now impracticable to base our measurement on natural objects; there are just too many.

Our correspondent would like to contemplate why aircraft flying heights are quoted in feet. I wonder how many air passengers try to convert these into miles, a more manageable unit for distances of this size. Of course there are reasons, but not related to the natural size of anything. So even imperial units fail nowadays in this respect.

Regarding body dimensions, this is just an attitude of mind. For an adult to remember their height in metres is no more difficult than remembering the route number of the bus into town. But if people choose to reject the metric system they will.

In any case, the human body has plenty of metric attributes. People like the way I can pick up a nail or screw and accurately describe its length in millimetres, without any ruler nearby. The trick is of course that my hand is near enough 100 mm across and the fingers provide 20 mm divisions. So my hand is a handy visual rule of thumb! (Sorry!) Likewise my waist is exactly one metre above floor level.

There are plenty of examples of metric sizes everywhere; it is just a case of looking out for them. It is a pity that this blog came in nearly 15 years ago; the author is unlikely to see my reply.

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