The next talent on the list is Superman's X-Ray vision. I always thought this was a ridiculous power that couldn't possibly happen in real life, but several biological examples, the cinematography of the movie, and a recent class I took about satellites and remote sensing has changed my mind completely. You just need to suspend your disbelief for a few minutes and assume that Kryptonians have evolved to have retinal cells that respond to nearly every wavelength of electromagnetic radiation. I'll lead in with some Earthly examples that show this to be biologically possible. First, bees have an extended visual spectrum that allows them to actually see UV light. We've named this color "bee purple," and plants have evolved together with the bees to take advantage of another visual cue they can use to attract pollinators. In the picture of a cucumber flower below, the left image is what we see, and the right image is a false-color composite of approximately what the bee sees. The bees have a slight trade-off in that they can't see as far into the red end of the spectrum as humans can. The mantis shrimp, on the other hand, compromises nothing! Well, that's a little bit of an exaggeration. They also don't see as well in the red end of the spectrum since that is the first wavelength absorbed by water, but have been found to adapt their vision when raised in shallower environments. They have a complicated vision system that may reach far beyond human eyesight nonetheless. Humans have 4 kinds of photoreceptors in our retinas (rods and 3 colors of cones). Mantis shrimp have 16. We can't even imagine what they see! The shrimp see many colors we can't detect, but due to their smaller invertebrate brains they can't actually tell apart colors as closely as we can. They just group light stimuli of several wavelengths into a single category like one shade of green if that group of receptors is activated. Still, this is an amazing sensory system which I'm sure leads them to appreciate their colorful appearance. Additionally, mantis shrimp have incredibly strong limbs that they use to crack mollusk shells (no easy task as anyone who tried to eat a closed clam can tell you). These punching pincers snap with the speed and force of a gunshot, which is so fast that it momentarily boils the water near them and creates heat and light! They are sounding more and more like Superman... Their power is only exceeded by the similarly pugilistic snapping shrimp. Another animal that takes more advantage of the electromagnetic spectrum for locating food is the pit viper. These snakes are so named for the pits below their eyes that sense infrared radiation. So no, these sensors aren't actually retinal, but they are integrated well enough into the brain that the viper can use this extra sense to find its prey. In some cool research going on at the Grace laboratory at the Florida Institute of Technology, they are blindfolding the snakes to get a better measure of their heat-sensing accuracy. Those are the biological limits of electromagnetic sensing, but mechanically we have come much further in extending our range of "sight." X-ray machines, heat sensors, and satellites take advantage of different wavelengths of radiation to give us another point of view. The advantage of using different wavelengths of light is that we can "see" deeper than the surface of an object. X-rays that look at our bones are the best example of this, and it's usually what you see Superman doing with his heightened senses: looking through surfaces. Different wavelengths can also show differences between objects that can't be seen in only visible light. The infrared heat-sensing image below shows a stark contrast between the warm-blooded human hand and room temperature lizard. We can easily distinguish humans from lizards in the light, but IR vision becomes more valuable in the dark. It's also useful when trying to tell apart objects that appear the same visually. There was an episode of Buffy the Vampire that showed members of the high-tech secret government organization called "The Initiative" using a heat sensor to pick out cold-blooded vampires from crowds of normal humans because outwardly they look the same. Well, as normal as you can be when you live on a Hellmouth... IR spectra are also handy for picking out differences in vegetation, like different crops, the health and moisture content of plants, or AstroTurf vs. real grass. In the left photo of the University of Wisconsin, Madison stadium, the football field is indistinguishable from the green grass and trees of the area. The right image, however, is a false-color composite where high IR reflectance is displayed in red (plants reflect a lot of IR so that they don't heat up). The trees and grass light up in red, but the turf of the stadium remains dark, showing us that it's not planted with real grass. One of the coolest applications of "seeing" other electromagnetic wavelengths would be if Superman could see radio waves. Then he would literally have radar! This suddenly makes his reckless flying through clouds seem much less reckless when you realize that he knows exactly what's on the other side since his radar vision penetrates the atmospheric moisture. So why was he de-powered when dragged into a ship with Kryptonian atmosphere? Why did Zod become overwhelmed with all of these super-senses only when his breather helmet broke and he was exposed to Earth's atmosphere? This can also be explained through the science behind satellites! Satellites are limited to using wavelengths of light that can easily penetrated the planet's atmosphere, especially since the signal has to travel through this boundary twice: first to reach the Earth's surface, then to bounce up to the satellite. Here's a diagram of what parts of the spectrum are the most absorbed by the atmosphere: It is no coincidence that the range we can see, visible light, is also one of the ranges least absorbed by our atmosphere. Animal eyes evolved to take advantage of this abundant, but not very damaging, radiation. So now I'm going to take the evolution proposition from before one step further: Kryptonians came from Earth, but then developed on a different planet where their eyesight had to evolved to see beyond visible light because it didn't penetrate very well, and only after that did they move on to colonize Krypton. On Krypton, the atmosphere was very dense, and blocked out almost everything except visible light. So the enhanced sight that had previously evolved became a vestigial trait that wasn't used until Kal-El came to Earth where more radiation was visible to him. This is a good explanation for his super hearing as well. If Krypton had a dense atmosphere, it is possible that sound didn't propagate very well, and hearing senses had to be more acute to pick up anything.
What I really enjoyed about the movie was Clark's struggles as a child to understand and control these enhanced senses. He has the equipment to see any wavelength of light, but he doesn't know how to focus it on just one part of the spectrum. Hence his vision becomes muddled with overlapping images of his skin, his bones, and his thermal signature all at once. It's an overwhelming experience for any kid! My only scientific qualm with the vision examples used in the movie is the trick he did of reading someone's ID badge through a one-way mirror AND through his pocket. Seeing people on the other side of the mirror would have been easy with IR or X-rays, but unless the name on the badge is written with a radioactive tracer or something special, there's no way Clark should have been able to read it. The letters are only distinguishable with visible light, and those wavelengths simply will not propagate through cloth or mirrors. Nice try, alien.
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Alanna DurkinExploring the realm of biologically inspired design one superhero example at a time, with some other natural sciences mixed in. Archives
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