Units of measurement are practically as old as civilization itself. Yet for most of that history, they came with persistent, frustrating problems.
Chief among these was the sheer inconsistency from one region to the next. Different areas relied on entirely different standards, creating headaches for trade and virtually every other form of cross-border interaction. Even when a powerful central authority managed to impose uniform measurements, those standards had a tendency to erode over time — especially if that authority weakened, faded into irrelevance, or disappeared altogether.
A major root cause? The standards themselves were often rooted in something completely arbitrary. Take the fathom — it was originally defined as the span between a large man's outstretched arms. With foundations that shaky, it's hardly surprising that thinkers began searching for measurement systems anchored to something constant and universal in nature, something that could transcend borders and serve the entire international community.
Amid the sweeping upheaval of the French Revolution, an opportunity presented itself. Revolutionary leaders seized the moment to overhaul and standardize their measurement framework. In 1790, the French extended invitations to both Great Britain and the United States to collaborate on this ambitious undertaking. Both declined, so France pressed forward independently. The meter emerged as the foundational unit of length, defined as one ten-millionth of the length of an Earth quadrant.
The kilogram, meanwhile, became the new standard unit of mass, derived from the mass of a cubic decimeter of water. In 1799, France officially adopted the metric system — a decision that would ultimately pave the way for the International System of Units we use today.