36. Krypton: It’s A Metric

Like argon, today’s noble gas coincidentally features prominently in science fiction — albeit in name only. But krypton also takes a place in the science factual story of international weights and measures.

Featured above: A glowing ampoule of krypton gas, radiating is soft white light.

Show Notes

Hair Trigger: My apologies if you received an email about this post the day before the episode aired. I accidentally hit “publish” instead of “schedule post,” d’oh!

The Man Of Tomorrow, Today: I really wanted to include a whole lot more about Superman in this episode, but alas, I’m running a chemistry podcast here, not a comics podcast. I do still like talking about comics, though, so that’s what these show notes are for, eh?

Jerry Siegel and Joe Shuster created Superman in the 1930s, and like all great comic book heroes, he’s more than just a supersonic patriotic crime-fighter. His is the quintessential immigrant’s story, and like his creators, Superman speaks particularly to the Jewish American experience.

The alien Kal-El was sent to Earth in a manner suspiciously similar to the way baby Moses floated down the Nile in his own origin story. It’s also worth noting that the Kryptonian naming scheme, with the -El suffix, is similar to a Hebrew syntax. Dani-el, Micha-el, Samu-el, Isra-el, etc. It may or may not be coincidence that Kal-El roughly translates from Hebrew as “The Voice of God.”

Anyway, after crash-landing in Kansas, Kal-El had his name changed to the much more American-sounding “Clark Kent,” and adopted his new home’s ideals of truth, justice, and the American way. Also like many immigrants, his journey to Earth was one of necessity, performed under distressful circumstances: His home planet of Krypton was destroyed. Like the Jews wandering in Egypt, he was a people without a homeland.

This is, of course, not original scholarship on my part. There have been many books written about Superman, his authors, and the resonance his story has for Jewish Americans. But it’s still fascinating, and even if it didn’t quite make the cut for the episode proper, I wanted to spread that information just a little farther.

Incidentally, Supes’ home planet wasn’t named until a year after his original publication, and it seems like the authors just picked a random element off the (still-young!) periodic table, just so it would sound vaguely scientific. Strange to think that Kal-El might just as easily have hailed from Xenon or Argon. He might have instead been The Last Son of Neon!

There is an apocryphal story that the convenient weakness of kryptonite was introduced in the radio serials as a way for Superman’s voice actor to occasionally take a break, but there doesn’t seem to be much evidence for that. Kryptonite actually predates the radio show, first mentioned in a 1940 story called “The K-Metal From Krypton.”

Last but not least, the fact that krypton difluoride is a cold, white crystalline solid? Well, if you ask me, that sounds suspiciously similar to the Fortress of Solitude as seen in 1978…

Sidenote: Is it just me, or is the pacing, well, absolutely glacial? Sorry, I’m sorry, I’ll see myself out. Tip your waitresses. Try the veal.

Episode Script

There is no such thing as kryptonite. The very idea is laughable, isn’t it? That -ite suffix would indicate some kind of mineral compound, but we know that krypton is a noble gas, with a valence shell full of electrons! It shan’t be combining with any other atoms today or any other day.

…Except for that one day in 1963, when one D. R. MacKenzie showed that, when irradiated at extremely low temperatures, krypton can combine with fluorine to create krypton difluoride, a white crystalline solid.

That’s as close as the real world gets to “Kryptonite.” But it’s not particularly dangerous. It’s almost never radioactive, and it disintegrates into its constituent atoms at temperatures warmer than negative thirty degrees celsius.

This makes today’s element slightly difficult for us to display in our collections, but I’m sure Superman will be relieved to hear.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re sizing up krypton.

We’re back in Group 18 today, which means we have once again entered the domain of Scottish chemist William Ramsay. Few people can claim to have discovered so many chemical elements, and certainly not in such a short span of time. In 1894 he discovered argon. The next year, he isolated terrestrial helium. Then, over a period of a few weeks in 1898, he summoned samples of krypton, neon, and xenon out of thin air. Well, actually, it was very thick air, liquefied under immense pressure and carefully boiled off to isolate elements by their boiling point.1

Regardless, it was an incredible feat, made even more impressive because before Ramsay came along, no one even knew this group of elements existed. Consensus was that sodium came immediately after fluorine, potassium came immediately after chlorine, et cetera. Remember, the defining feature of the noble gases is that they don’t react with anything, so no one even thought to look for them until the periodic table started to take shape.2

One scientist in particular was very disturbed by the discovery of the inert gases: Dmitri Mendeleev. He believed there was no way an entire group of undiscovered elements could be lurking in the shadows of his periodic table — and he worried that if there were, his crowning achievement might be as misguided as John Newlands’ Law of Octaves.3

He proposed that the first gas Ramsay had discovered was not a new element, but rather a heavy form of nitrogen, similar to how ozone is a heavy form of oxygen.

Mendeleev was wrong, of course, and once Ramsay pulled off his discovery hat trick in 1898, the noble gases were impossible to deny. Mendeleev could only hide behind his immense beard and grumble with dissatisfaction. For his accomplishments, Ramsay was awarded a Nobel Prize in 1904 — an accolade that Mendeleev never received.

Despite his protests, the periodic table was falling into a rigid and standardized form. And a few decades later, krypton would become the foundation for another, even more popular standard used around the world.

Standard units of measurement weren’t always so important. Centuries ago, the people of France didn’t need to define length or weight in the same units as the people of Japan, because they were practically never going to interact with each other. But this changed over time, of course, so what started as quaint regional differences suddenly became a messy tangle of law and commerce. On the most basic level, merchants on opposite ends of the ocean need to be sure that they’re receiving the right amount of product for the amount they’re paying.

But different units of measurement have caused weirder quirks than a bad bill of goods. Napoleon, for instance, was not a particularly short guy. He was five feet two inches tall — but French feet and inches were longer than the British units, making it sound to English-speakers like he was smaller than average. And that’s how you end up with an emasculating legend that persists for centuries.4

Even today, mix-ups over units of measure cause problems — sometimes costing hundreds of millions of dollars. In 1999, NASA completely lost a Mars orbiter because they work with metric units, but the craft was built by Lockheed-Martin using imperial units.5

There are three material qualities that people needed to agree upon: Distance, mass, and time. Today, we’ll focus on distance.

The first widely accepted standard unit of distance was proposed by the French in the 1790s. It was defined as one ten millionth the distance between the north pole and the equator by way of the meridian that runs through Paris. That distance was called the meter, taken from the Greek word for “measure.”

This was a tremendous feat of surveying ability, especially for the time. As we learned in the episode on copper, measuring such great distances accurately and precisely was a nearly impossible task. Those who had performed the job did so admirably, but alas, it was eventually discovered that the standard meter thus defined was actually two millimeters shorter than it should have been.

Other surveyors dutifully started over, and succeeded in coming up with more precise measurements. But in 1870, James Clerk Maxwell, a Scottish physicist, explained that defining our standard units of measurement as fractional bits of the Earth was a fool’s errand. After all, the Earth is a living planet, and will inevitably change in size and shape over time. In order to be truly constant and universal, he said, our units of measurement would need to be defined by the properties of individual atoms.6

It would take nearly a century of experimentation for scientists to measure such properties with a satisfying level of precision, but it finally happened in 1960. On October 14 of that year, the International Committee On Weights And Measures officially defined the meter as a function of krypton.

As we learned way back in the helium episode, one way to verify the existence of a new element is by the unique pattern of light it displays when heated and viewed through a spectroscope. Krypton’s spectral signature includes one very sharp, bright, orange-yellow line, which was perfect for taking and making precise measurements. The committee decided that henceforth, a meter would be defined as “the length equal to 1,650,763.73 wavelengths in vacuum” of that monochromatic light emitted by krypton.7

We have since moved on to an even more accurate measure of distance. A meter is now defined as the distance light travels in a vacuum in one 199,792,458th of a second. But the kryptonian meter represented the first time distance was defined as something constant and absolute, everywhere and every time in the universe.

Wherever and whenever you are on Earth, you have easy access to krypton — just not very much of it. It exists in our atmosphere at a concentration of about one part per million.8
That was useful information to know during the Cold War. Nuclear reactors unavoidably pollute the surrounding air with radioactive krypton, so by sampling the atmosphere around the world, scientists could deduce which countries were developing nuclear capabilities — even if they claimed that they weren’t.
If you’d like to collect krypton in higher concentrations for your collection, you can turn to another radiation detector: The Geiger counter. These devices are dependent on tubes filled with noble gases for their operation: When an atom of krypton is struck by radiation, it loses an electron. That electron is then attracted to an electrode inside the tube, generating a clicking noise. The more radiation there is, the more electrons get knocked loose — and the more clicking.
Of course, you could turn to something more mundane to add krypton to your collection — it’s commonly found in specialty lights and lasers. But you probably have several of those in your collection by now, and besides — as we move down on the periodic table, a Geiger counter is something that might come in pretty handy.
Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn a whole lot more about Superman, visit episodic table dot com slash K r.

Next time, we’ll sink to rubidium’s level.

Until then, this is T. R. Appleton, reminding you that twelve firkin, six kilderkin, or two hogsheads are all equal to a buttload.9


  1. Chemistry Explained, Timeline: The Discovery Of Elements.
  2. The Telegraph, Dmitri Mendeleev: Everything You Need To Know About The Inventor Of The Periodic Table Of Elements. Rhiannon Williams, February 8, 2016.
  3. Periodic Tales: A Cultural History Of The Elements, From Arsenic To Zinc, p. 85-87. Hugh Aldersey-Williams, 2011.
  4. How Stuff Works, Was Napoleon Really Short? Laurie L. Dove
  5. CNN, Metric Mishap Caused Loss Of Mars Orbiter. Robin Lloyd, September 30, 1999.
  6. Wired, Galileo, Krypton, And How The True And Accurate Meter Came To Be. Simon Winchester, December 18, 2018.
  7. The Physics Teacher, Foundations Of The International System Of Units (SI). Robert A. Nelson, December 1981.
  8. American Chemical Society, Molecule Of The Week Archive: Krypton. December 3, 2018.
  9. Scotch Addict via the Macallan Distillery tour, Scotch Barrel Sizes: Firkin, Kilderkin, Hogshead, Butt and Tun. August 27, 2009.

3 Replies to “36. Krypton: It’s A Metric”

  1. The element collector could maybe find Krypton in his bedroom window. Argon has been used for years in double pane windows and Krypron is used mainly in triple pane windows. The theory is that the heavy gasses will have less air currents moving the heat around and they wont react with anything.

  2. the part about how nobody knew the noble gases existed, and mendeleev didn’t include them on his original periodic table, could have made a nice link to the etymology of krypton’s name: from the greek ‘krupton’, meaning ‘hidden’, as in ‘cryptography’. nonetheless i loved this episode as all the others, it’s quite nice to have some more bitesized ones. thanks as always t r appleton!

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