Any way you shake it, the meter is an extremely important unit of measurement. It is one of the seven base units used in the International System of Units, commonly known as the metric system. Almost every country on Earth uses a meter to measure distance. And before the Americans, Liberians or Myanmar (the only three countries in the world that still officially use the Imperial system) shout: We don’t use the meter! We use our feet! We would ask them to consider this: The US government officially defines a foot as 0.3048… meters. That’s right, even if you don’t want to, the meter is how we define length and distance almost everywhere on Earth.
But where did the meter come from? Who decided how long a meter is? How do we know something is exactly one meter? Well, the story of this simple measurement is long, incredibly overcomplicated – and absolutely fascinating.
40 rods to a pig’s head
Let’s go back to the beginning, to before the meter even existed. That was in the days when measurements were more of an art than a science. When a foot was… the length of one’s foot. Whose leg exactly? No one can say. When an inch was the length of your thumb, or the king’s thumb, or even three grains of barley, dry and round, placed end to end, lengthwise. It does not take a rocket scientist to realize that these measurements are not very precise. To make matters worse, the measurements varied greatly from region to region. Maybe you use an inch of barley, but they use a thumb-inch, or maybe they don’t use inches at all, but something else entirely. According to one author, a quarter of a million different measurements were used at one time in France alone. Hey, those were the old days – what else could you expect? But then the old days became the not-so-old days, and science became more and more complex. People began to realize that these inconsistent and highly imprecise measurements made scientists’ jobs difficult. They began to call for a universal measure. One measurement to rule them all. This is the beginning of the metro’s life, but it took centuries to get to where it is today.
Very close…
So we had the idea of coming up with a single, universal measurement of distance, but how did we decide what it should be? Well, one of the first ideas came from the English architect Christopher Wren in the late 1600s. He proposed that the new universal measure should be the length of the second pendulum. Basically, if you make a pendulum that takes exactly one second to swing completely in one direction, the length of that pendulum will be one meter. Sounds like a pretty good idea, right? After all, this would mean that everyone on Earth could build their own seconds pendulum and know exactly how long
meter long. Perfect! No more grains of barley! Well, not quite. Unfortunately, the pendulum per second varies depending on where you are
you find in the world – not very much, but enough that it cannot be a universal measure.
The metric system is a tool of the devil
A bunch of other ideas were thrown around, but no one made much headway. Then something happened – and that something was called the French Revolution. France ushered in what it hoped would be a new age of science and knowledge. As such, the French Academy of Sciences has decided that it is high time to settle this whole thing with universal measures once and for all. After years of talks, they finally appointed a commission to actually do it.
This commission was headed by a man named Jean-Charles de Borda. If there’s one thing this guy likes, it’s decimalization. That is, he liked things that could be divided evenly, and we can partly thank him that there are 1,000 grams in a kilogram, 1,000 meters in a kilometer, etc. Now, if Borda had his way, we would have 100 minutes in an hour, 100 seconds in a minute. and 400 degrees in a circle—not all of his ideas stuck—but his committee eventually decided to define a meter: It should be exactly one ten-millionth of the distance from the North Pole to the equator.
Dunkirk to Barcelona
Now that that was decided, all we had to do was measure the distance from the North Pole to the equator, do some quick calculations, and above all change – oh, we have a universal measure. Simple, right? It is not OK. In the late 18th century, measuring such a great distance was no easy feat. In the end, a plan was made. Instead of measuring the end, the researchers would simply measure the distance from Dunkirk, France to Barcelona, Spain. These two
cities were located on the same longitude, so if you knew exactly how far apart they were, you could calculate the distance from the equator to the North Pole.
Grueling Work
Two astronomers, Pierre Machen and Jean-Baptiste Delambre, were hired to make the measurements. Mechain started down to Barcelona, and Delambre to Dunkirk, and they went about their business. But unfortunately, exploring so many kilometers was still an extremely daunting task. Plus, the aforementioned French Revolution ensured chaos reigned in the countryside. It’s not exactly the easiest environment to do tedious and precise calculations.
Holy meter
The time has come to make a meter. Using Mechain and Delambre’s measurements, mathematicians were able to calculate the distance from the equator to the North Pole. Then they divided that by ten million and we ended up with. Meter. Universal measure. With the magic number finally found, the Academy of Sciences had a physical object, a rod made of platinum, made to that exact dimension. Since then, that bar, known as the meter des Archives, has been the literal yardstick for one meter. First of all, the number that Mechain and Delambre came up with? That’s wrong. There were small errors in the calculations, which threw everything off. These errors would haunt Mechain for the rest of his life, and he eventually contracted yellow fever and died while in the field, trying to correct the calculations. Now the number was not far off: it was shorter than a real meter by only two tenths of a millimeter. But remember, the whole point of this was to make a meter that was exactly one ten-millionth of the distance from the North Pole to the equator. Why go through all that work just to get it wrong? Well, maybe you skipped all the measurements and just made a meter of some arbitrary length and called it a meter.
In fact, it was more than a century before we invented the ideal solution: the laser. The laser allowed scientists to measure the distance light particles travel, and since the speed of light is constant, we finally had a perfect way to define a meter. A way that will never change and could be repeated all over the world. That is why the definition of a meter used today is the length of the path traveled by light in a vacuum during a time interval of 1 / 299 792 458 seconds. It may sound complicated, but it’s something that will never change. Sure, it doesn’t have the same kitschy appeal of barley grains, but oh well. You can’t have everything.
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