Real kryptonite: the science behind Superman

Kryptonite is made up, of course. But a real mineral in London comes surprisingly close, and British physics students have spent years working out exactly how impossible Superman is. Here’s the real science behind the Man of Steel.

Jadarite: the kryptonite that came to London

Geologists from the mining company Rio Tinto found some unusual nodules in drill core from the Jadar basin in Serbia, where they’d discovered a deposit in 2004. They asked the Natural History Museum in London for help.

Mineralogist Dr Chris Stanley and colleagues confirmed in 2006 that it was a brand-new mineral. They named it jadarite, after the place it was found, and published it in the European Journal of Mineralogy in 2007. It couldn’t be called kryptonite, because it contains no krypton.

Then, in April 2007, the press spotted something. In Superman Returns (2006), the kryptonite’s case is labelled as sodium lithium boron silicate hydroxide with fluorine. Jadarite is almost exactly that:

The museum reportedly put a sample on display in 2007 (Likely), and Dr Stanley is said to have called it the coincidence of a lifetime. For the fictional version, see kryptonite, and for the film itself, Superman films in order.

Why jadarite matters beyond Superman

Jadar is reported to be one of the world’s largest lithium deposits, and lithium is what batteries are made from (Likely). The Natural History Museum still runs a research project on how to process this kind of lithium-boron ore. Serbia reportedly cancelled Rio Tinto’s mine plan after protests in January 2022, but we haven’t checked what has happened since.

Superman vs physics: what Leicester students worked out

The University of Leicester’s Department of Physics and Astronomy runs the Journal of Physics Special Topics, a peer-reviewed journal where students write short papers. Course tutor Dr Mervyn Roy has said the point is to teach how peer review and scientific publishing work, and Superman has come up more than once.

Superman as a solar cell

In the comics, Superman draws his powers from the yellow sun (see solar battery). So the students treated him as a solar panel, and the sums didn’t add up:

• Flying for eight hours at 30 km up would take about 207 billion joules to push through the air.
• Sunlight falling on him would give only about 1,096 joules a second.
• To make up the difference he’d need to be about 656,000% efficient. The best solar cells on Earth manage 44.7%.

Even a perfect, 100% efficient Superman would run out of energy, which breaks the conservation of energy. The authors suggested escape routes such as neutrinos, or stored energy. The university publicised the paper on 30 July 2014.

Catching Lois

Another student paper looked at the famous catch in Superman (1978) and worked out the pressure on landing, about 90,000 pascals on Superman’s arms. The verdict: Lois would survive unharmed (Likely: we’ve only seen summaries of this paper).

The best-equipped superhero

In June 2016 Leicester reviewed its students’ superhero papers from 2009 to 2016 and ranked Superman as the best-equipped superhero, ahead of Wolverine, Mystique and Thor.

What would kryptonite do to you?

In the comics, green kryptonite doesn’t harm humans at all. Real radiation is a different story: it would trouble Lois long before it bothered Clark.

To give a sense of scale, here are some figures from the UK government. Doses are measured in millisieverts (mSv).

These are general figures from GOV.UK’s dose comparisons, shared for fun and context. They aren’t medical or safety advice. If you have questions about a scan or about radiation, ask a doctor or see GOV.UK.

More to explore

Kryptonite first appeared not in the comics but on radio, in “The Meteor from Krypton” in 1943: see Superman myths busted. For more British Superman connections, see Superman and Britain, for everything that can hurt him, Superman’s weaknesses, and for the British-made films, Superman filmed in Britain.