# Why should you care about a tiny grain of sand?

by Elaine Schwartz    •    Jul 21, 2014    •    365 Views

Thanks to a grain of sand, the kilogram is shrinking.

The international prototype kilogram is triple locked under 3 bell jars in a vault in a chateau outside Paris. Handled only 3 times since 1889, it is secured with 3 keys that are each held by a different official. To those in-the-know, it is called Le Grand K.

Le Grand K

From: National Institute of Standards and Technology

While people do have an annual look at Le Grand K, its “witnesses”—the 6 copies that were made long ago—are used for making the reproductions that are used around the world as a global standard. In Maryland, the US copy of Le Grand K sits 60 feet underground in a bell jar behind 3 thick doors. Now though, the US copy and the others to which it has been compared are the weight of a grain of sand heavier than the original. No one knows why.

I guess we could say that the standard kilogram on which we base all other kilograms is no longer a kilogram. Or…is it a kilogram and nothing else is??? The answer really does matter to engineers that require precision in fields like fiber optics.

Where are we going with this? To the global commercial impact of standard weights and measures.

Imagine what commerce was like without shared weights and measures. In 18th century France, there were 250,000 different units and some even had the same name. Assorted fabrics, grain, wood all had their own metric. Traveling from one village to another, you could have seen a 20% difference in the size of a pint.

From here, the story continues with the French Academy of Science appointing 2 scientists who, during the 1790s, identified the size of a meter by calculating the distance from the North Pole to the Equator and dividing it by 10 million. The task was actually a huge trigonometry problem as each one traveled from one place to the next creating huge imaginary triangles to measure the distance. Once they knew the size of a meter, they said the kilogram was “a cubic decimeter of rainwater at 4 degrees Celsius” and then fabricated a platinum kilogram cylinder.

Today, except for the kilogram, the 6 other basic metric units—candela, ampere, second, meter, mole and kelvin—are based on a “constant of nature.” No longer a physical artifact representing a distance, the meter, for example, has become the “distance traveled by light in a given fraction of a second.” Still though, specific manufacturers of items as disparate as batteries and pharmaceuticals differ in their own measures. I just heard about a supply chain being disrupted because batteries labeled with the same voltage in the US and China were not the same. Embedded within other products, the batteries did not function predictably.

Our bottom line: Invisible because we are so used to having universally accepted standards, shared weights and measures are a basic requisite for the globalization of commerce.

Sources and more...Listening to Radio Lab, reading the Wired article, and then concluding with a paper from the Smithsonian was a fascinating process that I truly enjoyed. Do read all and The Measure of all Things if you want the entire story. The topic is fascinating!