Is it a bird? Is it a plane? Is it possible?S

I've been interested in superheroes for a long time, and not only because I think telekinesis would be useful. No, what really intrigues me is that your average superhero story is a fantasy dressed up as science fiction.

As I see it, there are three basic types of superheroes:

- The Mutated Hero, who's undergone a genetic change or five which allow him (or her) to channel superhuman abilities. My pet examples are Spider-Man and the X-Men.

- The Not-Of-This-World Hero, whose superpowers are of alien, magical, or divine origin. Think Superman and Thor, and possibly Wonder Woman.

- The Technology Hero, who uses advanced technology and science to achieve his (or her) goals. I always think of Iron Man, though Batman and Green Hornet also fit this model.

How scientifically accurate are the sci-fi elements of these heroes? Generally not very, apart from the Technology Hero. What genetic change would allow someone's limbs to stretch or contort in the blink of an eye, yet retain structural integrity? How can someone control the weather, or magnetism, or another human's actions, with only their body and mind? Would an alien physiology really enable someone to fly or see through objects? Not to mention the problems with mind readers, size changers, teleporters, and human bodies moving supersonically under their own power. The only way to make powers like these plausible is to call them magic - which ties in nicely with the superhero-as-modern-god analogy.

I identified the Technology Hero as an exception because the weapons he uses are generally believable and often based on real-world science. I'll admit to not being solid enough on physics to know if Iron Man's suit would actually be capable of everything it does, but it looks plausible and I'm willing to bet that if we can't do all that today, we will at some point. We can or are working on just about everything in a Technology Hero's arsenal, and if we're not, we'll be able to mimic the technology at some point. We might not achieve forcefields or invisibility, for instance, but we should be able to overlap energy fields or use nano-engineering to achieve a similar effect.

The other types of heroes, though? I think if we stretch our minds we can come up with origins and powers that wouldn't defy the laws of physics (or biology, or chemistry, or…). At least we can if we discount anyone who uses mystical or magical powers.

The alien Not-Of-This-World Heroes, though? As I said above, I don't see the powers Superman and the Martian Manhunter have as being particularly scientifically accurate, even if they can be darn cool all the same. Why would Kryptonians (or Martians) need X-ray vision and laser eye beams on their home world? And why would Superman, who grew up on Earth, retain the full muscle strength of someone raised in Krypton's higher gravity (or, for the alternate explanation of his strength, why would specific wavelengths of light affect strength)?

However, I do think that aliens could have what we'd call superpowers. Advanced stamina? The ability to withstand starvation, air deprivation, extreme temperatures, or other similarly harsh conditions? An amphibious respiratory system, or one that runs on methane? Acidic blood or saliva? Infrared or UV vision? Faster reflexes? More mental processing power? Even hovering or flight, if the world was right. Any of those (and more) could convey an evolutionary advantage, or become stronger on our planet. What if the alien was used to a different gravity or their metabolism was kicked into overdrive by a common Earth molecule such as chlorophyll? So, supposing there is intelligent life on other planets, I'd rank this kind of superhero as a scientific possibility.

Now we come to the last category, the least realistic after the magical and divine heroes. What Mutated Heroes exhibit are basically magical powers couched in science babble. To their credit, they were by and large created when DNA was a new discovery and not as well understood as it is today, and when the Cold War was causing mutation to become a trope, but still-how does a mutation based on exposure to radiation spread through the body and become active in a matter of days? I can understand adults passing latent mutations to their kids, and mutations occurring within the embryo, but not adult-exposure superpowers. In other words, the X-Men are more realistic than the Fantastic Four.

This doesn't mean, of course, that the X-Men are believable. They have some of the wildest, least scientifically plausible powers of any superheroes I've come across. Manipulation of heat energy, wings, telekinesis, invisibility, metallic skin, psionic armor… The only way I see these being possible is through technology, not through mental manipulation of the environment or what have you. Are we talking new kinds of brain waves that can become almost solid or maintain their strength over great distances? A controllable energy deficit within the body that would allow someone to absorb heat and thereby create ice? I'm racking my mind trying to come up with explanations for Storm, Magneto, and most of their colleagues, and I'm coming up short. This cannot be a good sign.

I think we might achieve "Mutant Hero" powers with judicial application of electronic implants, nanotechnology, and the like, which would turn our superheroes into Technology Heroes (and cyborgs). Can we get the same powers through biology and genetics? I highly doubt it, even when we fully understand how DNA works and can create our own versions of the molecule.

I'd love to see superheroes who fit the Mutant or Alien categories and were scientifically accurate. For that matter, I'd love to see Technology Heroes who were too. (Iron Man might have accurate inventions, but he's sure not carrying enough power to run them all, even with the arc reactor.) I enjoy the magical aspects of the heroes, absolutely, but why don't we get more science?

This post originally appeared on Science in My Fiction.