The problem with precision

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Simon Winchester’s latest book is The Perfectionists: How Precision Engineers Created the Modern World. He is also the author of The Professor and the Madman, The Map That Changed the World and Krakatoa, among other works.

It may be straining credulity a little to suppose that anything made of so desirable a substance as platinum could possibly ever feel forlorn.

Yet I have little doubt that one particular piece, which has been kept for the past century-and-a-quarter under three nested glass cloches in a locked and climate-controlled vault in a western suburb of Paris, is about to suffer a crisis of confidence of historic proportions. Stoic and imperturbable though the 78th element may be, this specimen, known informally across the world as Le Grand K, is understandably dejected, beyond all hope of consolation.

For late this fall, it will be spurned – by almost everyone on the planet.

Le Grand K is the world’s standard kilogram, a highly polished little cylinder of solid metal, about the size of a Zippo lighter and so exactly made that it was never, ever allowed to be touched by human hand. Since September, 1889, it has been the ultimate arbiter of mass, against which all others on Earth are measured. It stands at the head of a system of measurement that begins with the humble scale, the kind of device – household, industrial or medical – that is used whenever something in the world needs to be measured.

So, whether it’s a bag of sugar in a country store in Nigeria, a brand-new passenger jet just off the assembly line in Seattle or an aspiring hockey player at his gym in Ontario, each has a measurable mass that can be expressed in kilograms. And the proving of this measurement all boils down, ultimately, to Le Grand K.

That’s because the scales that initially declare these masses to be what they are, by law and by custom, are currently checked against master copies. In the aforementioned three cases, they are the standard Nigerian government kilogram kept in Lagos, the standard U.S. equivalent maintained in a gigantic complex in Gaithersburg, Md., and, for the would-be Maple Leaf, one of the three standard Canadian base units of mass locked away deep inside a secure suite of government offices at 1200 Montreal Rd. in Ottawa.

Then again, these national measuring standards – and scores more just like them in countries around the world – are all checked regularly for correctness against a family of formidably well-guarded platinum kilogram cylinders, the so-called témoins, or witness cylinders – the almost-perfect arbiters of mass, cast at the same time in 1889 from the self-same platinum alloy used for all the rest. (One of Canada’s, engraved with the number K74, is carried off to Paris regularly; the other two – K50 and K106 – remain uncomplainingly at home, to be checked against K74 when it returns from its Gallic excursion.)

Finally, from time to special time, these Paris-based témoins are themselves measured against the superaccurate, perfectly perfect mother and father of them all, Le Grand K in Sèvres. It has only happened four times in the past 130 years, so sedulously is the geriatric grandee cared for and protected. But by doing so, by making this comparison and thus employing the principle known as traceability – where every physical property of everything (mass being one property, length and time being others) can be traced back to one ultimate source of exactness – is the world’s weights and measures system, so essential to us all, kept in precise and perfect order.

Except – and here’s the reason for the dolorous mood of the moment – come November, the mass of the world’s everything won’t be traced to Le Grand K, not any more.

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The stubby little cylinder is about to be demoted from ultimate arbiter to museum piece. It will suddenly have no function. It will officially and literally be useless. Once upon a time, it was a thing revered, for it was, quite literally, the kilogram, everything being compared to it – and it quite literally beyond compare. Now this elegant and beautiful artifact is destined only to gather dust and be forgotten. Small wonder that it is enveloped in an air of metrological melancholy.

But more than that. The formal abandonment of the physical kilogram has implications that spread well beyond the basement where it is stored: An era of measurement that has operated for thousands of years will come to its long-drawn-out but inevitable end.

Now, I am far from being a Luddite – indeed, I count myself among the early adopters of shiny new technologies and have more computing devices than I can throw a stick at – but I confess to some misgivings. Do we need to abandon this and a handful of other, similarly time-honoured creations and concepts with such indecent haste? For abandoned they most certainly will be.

Ever since the Egyptians, five thousand years ago, came up with the cubit, the length of a pharaoh’s forearm, so humans have used the dimensions of bits of themselves or their environment as scales by which to measure things. The thumb was an inch, the foot was a foot, a thousand strides (the mille passus, as the Roman legions grumbled) made, more or less, a modern mile. Some were variable – the length of a Chinese li depended on whether the road went uphill or down. Some were improbable – the Koreans had a unit of time defined by how long it took a granite mountain outside Seoul to be worn to sea level by the wings of an angel who brushed the summit with her wings once a year. For eons, the human scale was everything.

But then the 18th-century French cast romance aside and declared the only true invariable to be Earth itself, not the arms or fingers or wings of its inhabitants. So an intricately careful survey was made of the length of a part of the meridian between Paris and Marseilles, then carefully extrapolated into the exact length of a full quadrant of the planet, pole to equator. The resulting number was divided by 10 million, and lo! The metre was born. A platinum rod was fashioned of exactly that length and formally declared to be the official prototype metre. Copies of it were distributed around the world, so that every bolt of cloth or width of street or length of newborn child could be known, accurately, checked against a trusted scale that, in theory, could be compared to this platinum rod.

But then came James Clerk Maxwell, physicist, originator of the electromagnetic theory of light and spoilsport-in-chief. In a famous speech at the annual meeting of the British Association for the Advancement of Science, held in Liverpool in the fall of 1870, the Scotsman challenged the wisdom of measuring things against physical objects, and by doing so shivered the timbers of millennia of tradition.

Earth, he declared to his Liverpool audience, was not nearly so fixed and stable as those Frenchmen who measured the meridian had supposed, despite their hauteur. It expands and contracts, slows down and speeds up. Large volcanoes and powerful earthquakes can change its shape. It may one day be covered with layers of meteorites or knocked off balance by a collision with an asteroid. To use Earth as a fixed standard for measurement was as ill-conceived a notion as using an arm or a leg or the touch of an angel. The only absolute invariables, Maxwell declared, were to be found in the world of molecular bodies – meaning we must seek our standards of length, time and mass “in the wavelength, the period of vibration and the absolute mass of these imperishable and unalterable and perfectly similar molecules.”

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It took almost 60 years for those who ran the scientific world to agree with him. Hardly, I must admit, the indecent haste I mentioned above – although, in millennial terms, it is somewhat hasty. The six-decade delay was largely occasioned by the old-timers of the metrology establishment, for whom the old ways seemed to be quite good enough, thankee kindly. But Maxwell’s reputation loomed large and long. And as the demands for ever-increasing precision in measurement began to assert themselves – with masses in the 1920s being calculated to micrograms, lengths to microns, time being checked to nanoseconds, electrical currents to millivolts – so his views started to gain traction, and the old ways began, creakily, to give way.

The first to fall was the unit of length, the metre.

In 1927, it was realized that the frequency of radiation emitted by a heated sample of the silvery-blue and very poisonous metal cadmium could be determined with great exactitude. Once the radiation’s frequency was known, by the simple arithmetical process of dividing it into the speed of light, its wavelength could be determined also. A specific number of these tiny wavelengths was then formally declared to be the metre.

At first, only the scientists agreed. But after much tinkering and argumentation, official recognition of this principle was granted internationally – the only difference being that the metal cadmium was replaced by the gas krypton. A ceremony was held in Paris on Oct. 14, 1960, where it was officially announced that the platinum bar that had been the metre since 1889 was no longer deemed to have “sufficient precision for the needs of today’s metrology” and had been consigned to the rubbish bin of history. A bloodless and bewildering confection of numbers, all based on the frequency of the radiation of krypton gas, replaced it.

I have no hesitation in saying that each time I hear the sequence of numbers spoken, I shudder. For some reason, they remind me of the opening lines of The War of the Worlds, in which H.G. Wells writes with magnificent prescience of “those intellects vast and cool and unsympathetic” – the Martians – who are about to take over our little planet. I feel that with the metre expressed in terms of barely explicable sets of numbers, the world is somehow set to spin out of control, if just a little. It is then that I wish for the rod of platinum to be returned to glory and to its meritorious standing in the world.

And it is why I feel just the same for the metal cylinder that is, for now at least, the kilogram.

This poor little beauty of a thing has but a few months left in its distinguished life. It will go just as the thumb and the foot and the wings – and now the platinum rod – have gone. Come November, the kilogram is to be defined – and one has to take a deep breath before launching into Draft-Concise-summary-2018.pdf" title="" class="" target="_blank">this monstrosity of a definition – “by taking the fixed numerical value of the Planck constant h to be 6.62607015×10⁻³⁴ when expressed in the unit J⋅s, which is equal to kg⋅m²⋅s⁻¹, where the metre and the second are defined in terms of c and Δν_Cs.” Whatever that means.

Of course, what it does mean is that intellects vast and cool and unsympathetic have come, it seems to me, one small step closer.

There are good reasons for all of this. The demands of a world so dominated by extreme precision – a world with, it is said, more transistors than leaves on all the trees – are such that metres and kilograms and seconds and units of electricity and light intensity now have to be measured and calibrated in concert, to tolerances that were barely imaginable when the Victorian metal smelters first cast their ingots of platinum. I accept these reasons and acknowledge that my regrets are those of a poor romantic.

Still, I confess that I derived some small pleasure recently when I learned that Canada, for one, is not going gently into that dark night, that it will not be turning its back entirely on platinum to embrace in its entirety the world of krypton frequencies and their kin.

(It has to be said that one of the extraordinarily complex balances – a Kibble balance, named in honour of one of its creators – which employs electrical charge as counterweight and can compute mass to hitherto unimagined degrees of precision, is in Ottawa. But this is for another essay, maybe.)

No, Canada, is keeping a firm hold on its three cylinders of platinum, come what may in November. It is not spurning precious metal the way those pesky Parisians are. Canada is proud of its trove and how it has cared for it. It acquired K50 in 1949. It bought K74 in 1992 and got hold of K106 just five years ago. K74 turned out to be so impeccable that it was formally designated the national standard.

Once Le Grand K suffers its humiliating demotion this fall, the need for K74’s working holidays in Paris ceases. But it turns out that Canada – using its fancy Kibble balance – will do the job of checking it, of keeping everyone honest, itself.

I find this somewhat thrilling – and most reassuring. That in matters pertaining to measurement, Canada is displaying the virtue of self-reliance, surely that most admirable of Canadian qualities. And so it seems to me that in Canada, at least, the romance of using solid metal as a metrologic talisman, albeit to a limited but symbolically significant degree, will be preserved. Meaning, maybe, that the advance elsewhere in the world of the vast and cool and unsympathetic will be halted, or at least slowed, on the brave banks of the Ottawa River.