How We Measure

I hope your week measured up to your expectations.  Speaking of measuring up, how do we measure?  This question has a big impact on all of our lives in many ways, including the impact it has on aviation.

Take for instance the minor, insignificant job of mine at Moore County Airport in Southern Pines, NC where I pump gas into aircraft as well as other line technician duties and responsibilities.  When driving heavy equipment like fuel trucks, we have a maximum ramp (or flight line) speed of 15 miles per hour (mph), reduced to five mph, a brisk walking speed, when within 50 feet of aircraft.  As aircraft fly by they, on the other hand, measure their speed in knots.  A knot is a unit of speed based on the nautical mile.  One knot is one nautical mile per hour.  One knot is equal to 1.1508 statute miles per hour (1.1508 mph).

And we fill up aircraft fuel tanks measuring gallons of fuel.  But for the jet aircraft we fuel, the jet’s pilots set their fuel panels to accept a certain number of “pounds” of fuel, there being about 6.7 pounds in each gallon of JetA (the most common type of jet fuel in the US).  When refueling aircraft, we line technicians bet (a “gentleman’s bet”) on the number of gallons the aircraft will actually take based on the number of pounds of fuel set on the fuel panel by the pilots.

Now take a far more impactful issue of measuring.  None of our measuring at Moore County Airport is done using the metric system.  Our runway is about 7000 FEET long (about 2.1336 kilometers) but our runway is not marked in kilometers.  We drive on the ramp in statute mph vice kilometers per hour. 

But NASA uses the metric system, or is supposed to, in their projects. 

You may remember The New York Times (and many other news organizations) reporting on October 1, 1999 and downloaded below on April 27, 2025 from https://archive.nytimes.com/www.nytimes.com/library/national/science/100199sci-nasa-mars.html#:~:text=OS%20ANGELES%20–%20Simple%20confusion%20over%20whether%20measurements,National%20Aeronautics%20and%20Space%20Administration%20said%20on%20Thursday, “Simple confusion over whether measurements were metric or not led to the loss of a $125 million (that’s a million with an “M” ☹) spacecraft last week as it approached Mars, the National Aeronautics and Space Administration said.

“An internal review team at NASA’s Jet Propulsion Laboratory said in a preliminary conclusion that engineers at Lockheed Martin Corporation, which had built the spacecraft, specified certain measurements about the spacecraft’s thrust in pounds, an English unit, but that NASA scientists thought the information was in the metric measurement of newtons.

“The resulting miscalculation, undetected for months as the craft was designed, built and launched, meant the craft, the Mars Climate Orbiter, was off course by about 60 miles as it approached Mars.

“‘This is going to be the cautionary tale that is going to be embedded into introductions to the metric system in elementary school and high school and college physics till the end of time,’ said John Pike, director of space policy at the Federation of American Scientists in Washington.

“Lockheed’s reaction was equally blunt.

“‘The reaction is disbelief,’ said Noel Hinners, vice president for flight systems at Lockheed Martin Astronautics in Denver, Colo. ‘It can’t be something that simple that could cause this to happen.’

“The finding was a major embarrassment for NASA, which said it was investigating how such a basic error could have gone through a mission’s checks and balances.”

But our failures in standardizing how we measure isn’t for want of trying.

150 years ago, the Metre Convention determined how we measure the world — a radical initiative for the time

Published: April 20, 2025 8:37am EDT

Author  Jonathan Simone Adjunct Professor of Biological Sciences, Brock University

On May 20, 1875, delegates from a group of 17 countries gathered in Paris to sign what may be the most overlooked yet globally influential treaty in history: the Metre Convention.

At a time when different countries (and even different cities defined weights and lengths based on local artifacts, royal body parts or grains of wheat, this rare agreement among nations offered something simple yet undeniably impactful: consistency.

A radical initiative for its time, the Metre Convention ultimately birthed a system of measurement that would transcend language, politics and tradition, and lay the foundation for a new global era of scientific and technological advancement.

Official engraved marble standard metre, at the Place Vendôme in Paris. The standard was promoted during the French Revolution to introduce the metric system to France. (Shutterstock)

A world divided by measurement

By the mid-19th century, the push for standardization had become increasingly urgent. Scientific discovery was accelerating, global trade was booming and industrial projects were growing in scale and complexity. But the world’s measurements were, frankly, a mess.

France had introduced the metric system during its revolutionary years, but other nations were slow — or outright unwilling — to adopt it.

Rivalries simmered not just among empires, but within the scientific community itself. Astronomers couldn’t compare celestial observations across borders because their units didn’t match. Engineers designing railway systems across Europe had to navigate conflicting standards for track gauges, load weights and even timekeeping.

This wasn’t just inefficient. It was a barrier to progress, a strain on economies and a growing source of frustration or a scientific world that aimed to speak in universal truths.

Faced with growing societal demands, the industrial world agreed it was time to act. The Metre Convention was the result.

Scientists and diplomats representing the 17 participating countries collectively established the Bureau International des Poids et Mesures (BIPM), headquartered just outside Paris, as the official keeper of measurement standards. Today, the BIPM is backed by 64 member states and governs the Système International d’Unités (SI), the measurement framework that underpins everything from bridges to smartphones.

And while by today’s standards, the SI may seem like a relic of old-school science bureaucracy, it’s anything but. Standardized measurement is the invisible infrastructure of the modern world. And when it fails, or more specifically when we ignore it, the consequences can be severe.

Take the Gimli Glider incident. In 1983, an Air Canada flight from Montréal to Edmonton ran out of fuel midway through its journey. The cause was a miscalculation caused by confusion between metric and imperial units: the ground crew had used pounds instead of kilograms to measure fuel, and the pilots didn’t catch the error.

The plane lost power at 41,000 feet (around 12,500 metres for those who prefer their near-death experiences in metric), and glided safely to an abandoned airstrip in Gimli, Man., and to the annals of history as a symbol of what happens when we take standards for granted.

Or consider the Mars Climate Orbiter, a US$327 million NASA spacecraft that disintegrated upon entering Mars’ atmosphere in 1999. Engineers at Lockheed Martin had used imperial units, while NASA had assumed metric. The mismatch led to a critical navigation error and the failure of the mission, highlighting the importance of consistency in measurement, even far beyond the confines of Earth’s atmosphere.

The Gimli Glider and Mars Orbiter failures show what happens when consistency breaks down, but they’re more than just cautionary tales. They reveal how much of modern life depends on the shared language of measurement, and how easily that foundation can be cracked.

And therein lies the genius of the Metre Convention. It created a system that allows the world to communicate in the same terms. When someone says “kilogram,” “second” or “volt,” there is no ambiguity. That shared understanding is what makes global collaboration possible.

The Mars Climate Orbiter at the Spacecraft Assembly and Encapsulation Facility in the Kennedy Space Center in Florida. (NASA/KSC)

From man-made objects to universal constants

But as scientists are wont to do, good ideas are refined, and standards evolve. For much of its post-Metre Convention history, the kilogram was defined by a physical artifact — a hunk of platinum-iridium alloy stored in a vault in France. But in 2019, that changed. Now, the kilogram is defined by Planck’s constant, a fundamental feature of the universe. The shift marked the final step in a long journey: every base unit in the SI is now rooted in nature rather than arbitrary human artifacts.

Onward and upward!

Sources:  New York Times, Shutterstock, NASA/KSG, Jonathan Simone Adjunct Professor of Biological Sciences, Brock University