Are imperial feet “natural” units ?
With the slow transition to metric in the UK, a lot of myths have emerged regarding metric and imperial. With a New Year it is an appropriate time to examine some of these myths starting with the claim that imperial feet are ‘natural’ units.
Despite the end of the British Empire and the demise of the pith helmet, quite a few British people are nostalgic about imperial units. However, many people are not really proficient in using them and often are ignorant about their history and usage. For example many people do not know how many yards are in a mile. When the Times carried out a straw poll in early 2006 answers given for yards in a mile ranged from 52 to 10 000. The vast majority of people - even elderly - cannot explain how an acre is defined.
It has been often claimed in the British news media and by imperial supporters that imperial units are ‘natural’. Yet no evidence is offered to support this. What part of the body weighs a pound? What volume naturally corresponds to a pint? Maybe the obvious example is to say that the imperial foot is a “natural unit”.
However, a little thought shows that this is an empty claim. A unit needs to have a standard size otherwise there would be complete chaos. Human feet are not a standard size and so there is no natural size for the unit. The fact that human feet vary led to many different standard feet in Europe in the past; a key reason why an international system (metric) was needed.
In fact very few people have feet that are as large as the imperial foot; you would need a British “shoe size 12 ½” foot! The vast majority of people have smaller feet (the photo above shows 3 people measuring their feet against a scale in inches). The average human foot is 24 cm versus 30.48 cm for the imperial foot. If an imperial foot is “natural” then by implication most people have unnaturally small feet! If in doubt try measuring your own feet and those of your friends and family.
A much stronger argument is that decimal numbers are “natural” since all able bodied people have ten digits. It is nonsensical to justify keeping imperial on the basis that the units are “natural”; parts of the body are non-standard and so quite unsuitable as the basis of modern measures. Far better to use the accurately-determined and easy-to-use metric units.
[See also related article at http://www.metricviews.org.uk/2007/10/28/imperial-units-natural/ - Ed]
January 1st, 2008 at 12:25
It may be that most people who speak in support of imperial units by saying they are “natural” are really saying they are used to them and can visualise in them.
However I’ll never forget what someone said on a radio phone-in on the subject a few years ago. The presenter challenged a pro-imperial caller by asking him to explain what was supposed to be so natural about feet and inches. The response came “try looking at the end of your leg”. He may have scored a comic point but he revealed his literal interpretation of the word “natural” in that context.
January 1st, 2008 at 21:15
I have just looked up “Natural Units” on Wikipedia (http://en.wikipedia.org/wiki/Natural_units). The opening line of the article states: “In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units.”
The article goes on to list a number of candidate physical constants that could be used in a system based on “natural units”. They are:
• Speed of light in a vacuum
• Gravitational constant
• Planck’s/Dirac’s Constant (the two differ by a factor of 2*pi)
• Coulomb Force Constant
• Elementary charge [charge of an electron]
• Electron Mass
• Proton Mass
• Boltzmann’s constant.
Many of these constants can be measured with a precision of better than one part per million, making them the ideal building blocks for a system of measurements. As SI develops it is slowly moving that way and away from the use of physical artifacts, provided of course that the unit of measure concerned can be reproduced to the same precision. The metre, for example, is currently defined in terms of the second and the speed of light while it is expected that within the next few years, the kelvin will be defined in terms of Boltzmann’s constant rather than the triple point of water.
Without going into too much detail (the reader should read the Wikipedia article for more detail), it is quite obvious that the foot is not one of these units of measure, nor is it based on any of these units other than indirectly via the metre. Apparently apologists for the imperial system of units either do not appear to understand what a system based on “natural units” is about or they have a totally different definition of what “natural units” mean.
January 3rd, 2008 at 04:35
I would be curious to see what the length of the feet of the three persons in the photo would be if they had shoes on. I don’t think the original foot measure was meant to define a bare human foot, but one wearing typical shoes.
People who use there feet to measure don’t normally take their shoes off, thus the error in their foot measurement for the purpose of estimation may not be that far off.
Wasn’t the foot originally defined as the average length of the feet of 12 men chosen randomly coming out of a church on Sunday morning? I’m sure they weren’t measured barefoot.
January 3rd, 2008 at 12:33
I don’t think the foot is a ‘natural’ unit at all. As I was born and raised in a full metric country (The Netherlands), I think in centimeters and meters. When I read in an English book something like “He was 30 feet away” then I calculate in my head “that about 10 meters” and then I can visualise it.
To me a foot seems too large for small things and too small for larger objects. It would be quite cumbersome to renovate your house in feet, switching back and forward between feet, inches and fractions.
But then, I think it is just what you are used to. Someone who has been raised in Imperial would find inches-feet more ‘natural’, someone who has been raised in metric will find centimeter-meter more ‘natural’.
Just my opinion.
January 3rd, 2008 at 13:07
Well, obviously if the woman and two men in the photo had shoes on, their shoes would be of differening sizes and a little bigger than their bare feet. The real point is that whether shoes are worn or not there is no natural constant size for feet.
I have never heard the explanation involving people coming out of church and do not believe it to be true.
A historic account is given at http://www.unc.edu/~rowlett/units/dictF.html
“The modern foot (1/3 yard or about 30.5 centimeters) did not appear until after the Norman conquest of 1066. It may be an innovation of Henry I, who reigned from 1100 to 1135. Later in the 1100s a foot of modern length, the “foot of St. Paul’s,” was inscribed on the base of a column of St. Paul’s Church in London, so that everyone could see the length of this new foot. From 1300, at least, to the present day there appears be little or no change in the length of the foot. “
January 3rd, 2008 at 13:57
Another article appears in Wikipedia - http://en.wikipedia.org/wiki/English_unit. This article catalogues 20 different units of measure that have been used in England for the measurement of length, ranging from the line (about 0.3 mm) to the league (about 5 km). To this we should add the units of measure used in Scotland and elsewhere which would give an enourmous number of units of measure, often with the same name but with slightly different values.
In contrast, the same range of values can be covered in the metric system using just one unit of measure - the metre, plus two of sub-units - the millimetre and the kilometre, or three if we include the centimetre.
January 5th, 2008 at 22:12
Imperial units may be “natural” in the sense that it was natural for the illiterate peasants who developed these systems of measurement to use their body parts to measure things. Thus we have hands, feet, paces etc used for measurement of length. However in the 18th century the rise of education and trade between nations made such measurements cumbersome, and a new universal system had to be designed for the needs of the modern world. It is quite staggering that the UK and the USA, two countries with the very high rates of literacy, should be the only two countries in the world who find SI units so difficult to adopt. Perhaps they just yearn to be ignorant peasants again.
January 10th, 2008 at 12:14
British anti-metricationists have the anti-EU card to play (unlike anti-metricationists in the rest of the Commonwealth), while the Americans feel that they don’t need to metricate because of their superpower status.
April 9th, 2008 at 03:38
The imperial foot is indeed quite large. The Spanish foot is closest to the average natural foot, and may have been defined as such. As the photo above shows, units based on body parts are unreliable. It may have been satisfactory in ancient times, when precise measurements were not needed, but less than adequate after the 1500’s, and useless after 1800. As we have learned from the Mars Orbiter mishap, we need to know what units we are working in. The imperial foot is more likely a multiple of a smaller unit or a fraction of a larger unit, that is reasonably close to a natural foot to be named so.
June 10th, 2008 at 19:34
Whether imperial measures are ‘natural’ or not is totally immaterial. the world is metric! I am not even going to argue whether one system is “better” than the other, because it doesn’t matter. It’s a bit like the old Betamax vs VHS argument - VHS won out, even though many argued that Betamax was technically superior. Rightly or wrongly, the whole world settled on VHS. Same with our measurement systems - the world uses metric, end of story. To try to continue using - or worse, actually imposing the use of - a system that is alien to most of the world is simply self-defeating. But shooting ourselves in the (human) foot is one of our pasttimes.