Science Says Superman Should Be Black

Superman should be black.

By that I mean he should have dark skin, and not that he's African-American or any other person of color. After all, the Man of Steel is from the planet Krypton, not Earth. That said, Superman could indeed be played by a black actor in future superhero movies.

READ MORE: Superman Is An Alien, But His Ancestors Were Human

My argument for why Superman should be black is based on science. Before I explain the reasoning, however, we need to address a sensitive subject: race. Many people use skin color as shorthand for ethnicity, but 'race' has little meaning in biology – it's a social concept that describes recent ancestry.

Race matters for superheroes because it contributes to their identity. And over the past few decades, comic book publishers and movie studios have increasingly changed characters to reflect a society's ethnic diversity.

While that should be applauded in principle, identity changes are often short-term publicity stunts. It might sound cynical, but if publishers and studios had pure intentions, changes would be permanent. As long-time comic fans know, major heroes almost inevitably revert back to their original identities.

Rather than promoting diversity just for diversity's sake, I believe the case for changing a character's identity is made stronger if the rationale makes sense based on origins and powers. The change is more likely to be welcomed – and become permanent – if it's based on logic, not gimmick. And that brings us to Superman.

Because most superpowers break the laws of physics, explaining why they're impossible is a pointless exercise. For the science of superheroes, it's more fun to focus on what's plausible. So while Superman's powers probably require unrealistic amounts of energy to work, we can at least imagine how to maximize the energy he'd need.

Solar-powered cells

In the movie Man of Steel, Superman asks his biological father why he's different from humans. As Jor-El explains: "Earth's Sun is younger and brighter than Krypton's was – your cells have drunk in its radiation, strengthening your muscles, your skin, your senses."

The fact Superman is powered by solar radiation – light – is also shown in Batman v Superman: Dawn of Justice. In one scene, he regenerates after bathing in the Sun's rays, paying homage to the comic that inspired the film, 'The Dark Knight Returns', when he tells Mother Earth: "The Sun's power... fuels us both."

Almost all life on Earth is ultimately powered by the Sun via photosynthesis: plants and other organisms use light to make food (carbohydrates) from CO2 and water. Their photosynthetic cells also release oxygen, which can be used to burn the energy-rich carbs that fuel metabolism.

Superman's cells would carry out a process similar to photosynthesis. Instead of making carbs, maybe he synthesizes fictional molecules that store even larger amounts of chemical energy.

Light rays consist of photons, subatomic particles that behave as both waves and pure energy. The length of a wave determines a photon's energy: short wavelengths – gamma rays, x-rays and UV light – are at one end of this spectrum, long wavelengths like infrared at the other.

High-energy radiation such as UV damages living tissue and can trigger genetic mutations (potentially causing cancer), whereas low-energy radiation is harmless but has low energy. As a consequence, Superman would absorb photons from the visible spectrum.

In complex organisms, photons are harvested by specialized compartments, such as the chloroplasts in plant cells. Chloroplasts contain proteins that funnel photons toward pigments, which convert energy from light.

When photons hit a pigment molecule, its electrons gain enough energy to leave their associated atoms. Electrons are then passed along chain reactions to produce molecules that can later release the energy stored in their chemical bonds, which is used to synthesize carbs.

Colored pigments

On Superman's home planet of Krypton, the best pigment color for absorbing solar radiation would be black.

Light-capturing pigments act as antennas tuned for picking-up photons with a particular energy, and their colors – how they look to our eyes – is determined by which photons they absorb. Blue photons have more energy than red photons, but few manage to reach our planet's surface.

Air and water filter-out certain wavelengths. On Earth, land plants have evolved to use the red-absorbing pigment chlorophyll, which looks green. Not all photosynthetic organisms are green, however: some plants have red leaves, while purple bacteria can even absorb infrared.

Photosynthetic organisms on distant worlds would use whichever pigments are most appropriate to the available wavelengths of light. Green may be common on Earth, but other colors could be more popular on other worlds. This could be exploited to detect signs of extraterrestrial life, as described in a brilliant article in Scientific American by biometerologist Nancy Kiang of the NASA Goddard Institute for Space Studies.

As Kiang explains in her article, 'The colour of plants on other worlds': "The limiting factor is not the feasibility of novel pigments but the light spectrum available at a planet's surface, which depends mainly on the star type."

While the light that reach the surface is affected by which wavelengths penetrate the atmosphere, it's ultimately dictated by which rays are emitted by nearby stars.

And as comic fans know, Krypton orbits a red star and Superman gains his powers thanks to Earth's yellow Sun.

NEXT: Why Krypton's environment drives the evolution of dark-colored skin.

In Man of Steel, Jor-El sends his son to a planet "orbiting a main sequence yellow star." What does that mean? Many stars have a lifespan lasting billions of years, which often includes a 'main sequence' – the period when it carries out nuclear fusion, forcing hydrogen atoms together to create helium. This generates massive amounts of light energy.

Sun of Krypton

Astronomers classify stars according to 'spectral type' – basically, temperature and luminosity. There are 6 types (O, B, A, F, G, K and M). Rare O-type stars are hot, bright and look blue, whereas M-type stars – such as red dwarfs and red giants – are relatively cool and dim. Our Sun is somewhere in-between, a warm and yellow G-type star.

After accounting for atmosphere, the peak wavelength of light reaching Earth's surface is around 685 nanometers. For an M-type star like Krypton's Sun, it's about 1045 nm. In Man of Steel, a Kryptonian soldier says atmospheric conditions on their spaceship isn't compatible with humans, so the peak wavelengths would be slightly different due to filtering by air and water vapor.

Photosynthetic species – including a Kryptonian like Superman – living on a world orbiting a relatively inactive star would therefore need dark pigments to harvest light.

As Dr Nancy Kiang explains in her Scientific American article: "A planet around a quiescent M star would receive about half the energy that Earth receives from our Sun... Evolution might favour a greater variety of photosynthetic pigments to pick out the full range of visible and infrared light. With little light reflected, plants might even look black to our eyes."

Dark skin

The dark pigment that Superman's cells would need to absorb sunlight has a different function to melanin, the brown pigment that humans and other mammals use to protect against damaging UV radiation.

After humans migrated out of Africa 200,000 years ago, those populations exposed to less light would have been under weaker evolutionary pressure to spend metabolic resources on making UV-blocking pigments, which is why their descendants now have white skin.

Characteristic features of species are usually the result of natural selection, adaptations to their local environment. Because Superman has powers, light-capturing pigments must be useful to the survival of Kryptonians.

How did superpowers evolve? One possibility is that abilities were favored by evolution on Superman's home planet, and his ancestors lost their powers when the star turned red. Alternatively, they never evolved super-strength or super-senses – light was simply an energy source for ordinary metabolism – and Earth's yellow Sun artificially boosts their abilities.

Will we ever see a black Superman? In fact, Kryptonians of color already feature in comics. On an alternate version of Earth, for example, Calvin Ellis is not only Superman, but President of the United States (the character was modelled on Barack Obama).

But ethnic diversity hasn't always been politically correct. One issue of Superman describes Vathlo Island as 'home of a highly developed black race'. Such cringeworthy statements were typical back in the 1970s, but as comics writer Mark Waid points out, "A lack of ethnicity was an error of omission, and I'm not sure given the time that it's fair to call that 'racist'." It's less forgivable that the Kryptonians in Man of Steel (released in 2013) were all white.

DC Comics regularly relaunches its continuity, but it's unlikely the company would make Superman black, partly because he has so much history. A hero's race influences whether people identify with that character too.

But there is a precedent for changing ethnicity. Most famously, Nick Fury – traditionally depicted as white – was reimagined as Samuel L Jackson in comics. Life then imitated art as the actor was cast in the Marvel cinematic universe. Fury is a relatively minor character, however, and changing a major superhero might be met with more resistance from long-term fans.

The companies that own superheroes – publishers and movie studios – could follow the example of their heroic characters and make brave decisions. Henry Cavill will play Superman in Warner Bros' Justice League films, but what about the inevitable reboot in a few years' time?

Science says Superman should be black. Hopefully the next time we see him on screen, the Man of Steel will be a more realistic, solar-powered superhero.