Photo by Sergey Zolkin on Unsplash

Normally, as my readers know, my blogs cover a wide variety of topics. I like to relate and link seemingly unrelated topics to each other in innovative ways. It keeps our critical thinking faculties sharp! However, this blog deviates from the pattern to share two fresh viewpoints on changes in engineering standards. It’s technical, but important. Science textbooks will need to be rewritten!

It doesn’t happen often, but after a November 2018 vote at the Congress Chamber in the Palace of Versailles, four fundamental units of measure have been redefined. An assembly of metrologists (those who study the science of weights and measures) voted to redefine the International System of Units (SI)’s ampere, kelvin, kilogram, and mole. 

These four units join the meter, candela, and second in being defined not in reference to physical artifacts, but in reference to fundamental physical constants. Scientists say redefining these units to be based on a physical constant will make measurements more accurate and stable. 

Science students may not be too happy about having to pay for new science textbook editions, but the unanimous vote was followed by a standing ovation by the assembly’s participants from over 60 countries.

Engineering Standards Must Be Correct

The news was followed up by a Wired blog by Rhett Allain, an Associate Professor of Physics at Southeastern Louisiana University. He agreed the “definition-based standard” was a better choice:

There is a new standard in town, and it’s sort of a big deal…It replaces the old definition of the kilogram that didn’t even have a definition. The old kilogram was an actual object. It was a cylinder made of a platinum alloy and it had a mass of 1 kilogram. It was THE kilogram. If you wanted to find the mass, you had to take it out and measure it. You could then use it to make other kilograms.  

He was behind the new standard of defining the kilogram using another constant—Planck’s constant (the details are in the Wired story). However, Allain also cautioned that there is a wrong way to define the kilogram. “Unfortunately, I have already seen some very poor explanations of this new definition of the kilogram,” he wrote. His fear, he wrote, was that “these super-simple (and technically wrong) explanations might become very popular.”

For example, he cites an example: “The new definition of the kilogram sets it equal to the mass of 1.4755214 x 1040 photons from a cesium atom.” Of this he notes, “That is so bad. I’ve even seen a diagram with a traditional balance. On one side there is a kilogram mass, on the other side a bunch of photons. Please help; please don’t share that kind of stuff. You might as well just say ‘Oh, hey—the kilogram is now defined by some magical spell.’”

For Allain, this change is another argument in favor of his number one rule about science communication:

You can rarely be 100 percent correct in your explanation, but you can be 100 percent wrong. The goal isn’t to be correct in your writing—it’s to not be wrong.

I have to agree with Allain. Scientific writing is hard, but propagating the “wrong information” can have serious consequences. 

I always encourage readers to test, test, test, and look at things with a fresh perspective. Add to my mantras an echo of Allain’s: write with care.