Why do superhero shows mess up the smallest of science details?

In the second episode of season two of Supergirl, Supergirl and Superman team up to take on Metallo, a cyborg with Kryptonite-based powers.  In an early battle, Superman hits Metallo, which left trace amounts of Metallo’s metal exoskeleton on Superman’s hand.  Superman flies off to his Fortress of Solitude, where the analysis reveals that Metallo contains promethium, the “strongest metal known to man,” according to the analysis.  They could use the radioactive signature of promethium to track Metallo.  Winn, a technician at the Department of Extra-Normal Operations (D.E.O.), looks for promethium’s radioactive signal.  He finds it successfully, exclaiming, “Bingo, atomic number 61, come on down,” and Supergirl and Superman rush off to take on Metallo again.

As Winn tracks promethium on his screen, the chemical formula C12H22O11 pops up.

sugar in Supergirl

This isn’t promethium- it’s the chemical formula for sucrose, a sugar.  Sucrose is a molecule that is a disaccharide (double sugar) composed of glucose and fructose linked together.  Sucrose is often extracted and refined from sugarcane or beet sugar to make table sugar and sweeteners for human consumption.

sucrose molecule

Promethium, on the other hand, is an element.  Its symbol is Pm, and it has 61 protons.  All isotopes of promethium are radioactive.  It can be artificially produced as byproducts of uranium fission or by bombarding neodymium-146 with neutrons to make neodymium-147 which beta decays into promethium-147.  Promethium can be used as a light source, in a nuclear powered battery, or potentially as a portable x-ray source.


Now, in looking up research for this article, I ran across some information in the DC Database that indicates that promethium is a metal alloy in the DC universe that has different properties than “real” promethium.  Volatile promethium is used as a power source as it can absorb and generate energy.  Depleted promethium is alloyed with titanium and vanadium to create a near-invulnerable metal.  Basically, promethium is sort of like the DC equivalent of Marvel’s adamantium.

This is perhaps what the show writers were going for- the DC alloy of promethium, not the element.  After all, they say in the episode that promethium is “the strongest metal known to man.”  (In real life, tungsten is considered the strongest natural metal, steel is the strongest alloy, and chromium is the hardest metal.)  However, they definitely borrowed ideas from the element promethium, including calling it element 61 and looking for a radioactive signature.  You could argue that maybe the alloy promethium contains the element promethium, but the chemical formula for sugar isn’t even an alloy.  An alloy is a substance composed of two or more elements, with at least one of those elements being a metal.  C12H22O11 contains carbon, hydrogen, and oxygen- no metal, therefore, not an alloy.

And yes, I realize that it’s silly to complain about such a small detail in a fictional show about superheroes and aliens.  But I’m just offering- writers, if you’re looking for a science consultant, I’m available.


Keep calm and science on.

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