y now, I'm sure everyone has heard that nuclear radiation doesn't give you super powers. In fact, it's sort of bad for you, causing a broad range of genetic and cellular damage which can lead to radiation sickness, cancer and death. Visible mutations may occur in the offspring of a surviving victim (though not the victim himself), but if beneficial ones do occasionally occur, they're masked by the horror show of the awful ones, which vastly outnumber them. If Daily Bugle photographer Peter Parker really was bitten by a radioactive spider—we have only his own word on this—then he is lucky to be alive, and any superpowers he may have acquired must have come from a different source.
"Nanotechnology" is the glib answer put forth by Columbia Pictures in the new Spider-Man movie, but this sort of buck-passing does not change the fact that even molecule-sized machinery is governed by the laws of nature. Some things are possible with machinery and designer mutations, and some are not. So the question is: Which of these categories best describes Spider-Man's many abilities?
Spidey's superior strength is interesting, since his muscle mass appears to be that of a normal human. If he'd simply bulked up on steroids and growth factors, he would look less like a mild-mannered science whiz and more like, well, a comic-book character. One possibility is that his cells have been infused with extra power, in the form of mitochondria. These are microscopic blobs in a cell which oxidize glucose (sugar) to produce a fuel called ATP, and the more of them you have, the more energy the cell can generate. Cells can also generate energy without oxygen—the "anaerobic metabolism" we use during sprinting and weightlifting—when an enzyme called phosphofructokinase is present. Unfortunately, this results in a buildup of lactic acid in the tissues, leading to fatigue, cramping and muscle failure.
Spider-Man's body could also benefit from excess production of endorphins—pain-killing molecules which have been implicated in the feats of great human strength which occur under emergency conditions (e.g., in 1971, 5'4" Jane Hawkins, weighing only 110 lbs, lifted a car off her trapped brother—a story so common it rarely even generates headlines).
Other features which might be overexpressed or slightly mutated include the actin and myosin proteins which slide (or ratchet) together to make muscle cells contract, and the neutrophils and myoblasts which help the body repair damaged muscle fibers after the strain of heavy exercise. An interesting question for Spider-Man chronicler Stan Lee is whether Peter Parker's temperature and appetite are abnormally large after a few hours of Spideying around. Properly speaking, he ought to pack down carbs like a starved pig, and sweat like one, too.
Wall-crawling can really suck
Parker's quickened reflexes are somewhat harder to explain. Real spiders have quick reflexes for the same reason mice do: They're small, so their nerve impulses have only a short way to travel. Electricity travels through nerve and muscle cells at only 300 meters per second—often much slower—so reaction times are longer for large animals such as humans, yaks and blue whales. Unless the nerves are replaced nanotechnologically with something faster, like copper wires, there's no good way to speed this up. Venom, the evil Spider-Man, wears a nanotech-based supersuit which may in fact be capable of carrying nerve impulses, but such a rewiring of Parker's own body has never been described.
However, muscle fibers themselves have a "shortening speed"—the time it takes them to contract—which varies widely in the animal kingdom and even within a single organism. So even if his nerves are slow, Spider-Man's mutations may well include faster muscles. Faster thinking is also a possibility, since certain stimulants (e.g., methamphetamine) can speed up reflexes, increase alertness, boost confidence and energy levels and suppress the symptoms of fatigue. These drugs also suppress appetite and increase aggressive or confrontative behaviors. I hate to say it, but this does sound like our Spidey. This is not to say that Peter Parker is necessarily a meth junkie; possibly the chemicals are produced "naturally" in his own body.
Spider-Man's climbing ability is perhaps the hardest to explain scientifically. Real spiders climb by means of friction: They have tiny barbed hairs on the ends of their feet which permit them to cling to "smooth" surfaces like glass, by snagging on imperfections which are tenths or hundredths of a millimeter in size (the smaller imperfections of highly polished glass are too smooth for even spiders to climb). Considering that the very largest tarantulas weigh only 6 oz (0.17 kg), the equivalent hairs on a human-sized hand or foot would need to cover 533 times as much area, and grip millimeter-sized bumps or larger. And this would ruin the hand for any other use (think of all the lint it would accumulate!), unless the barbs were also retractable—a huge biomechanical problem all by itself.
Geckos, a family of roughly tarantula-sized lizards, are also good climbers and even ceiling-walkers, but use two entirely different mechanisms for it: suction and adhesion. To oversimplify slightly, the pads of their feet are sticky with a natural glue, which adheres to a variety of natural and artificial surfaces. Unfortunately, as any chemist can tell you, there are all sorts of adhesives in the world, and none of them will stick to everything, and most of the really strong ones rely on chemical reactions and the evaporation of solvents before they will stick. Conversely, the always-sticky varieties tend to be weak, and vulnerable to moisture. Imagine climbing a building with Post-It Notes and you'll see what I mean.
Notably, among the many human-sized climbers in the animal kingdom, there are none which can climb glass, or even rough cement. Fortunately, human beings are adept at harnessing principles like suction. The cup-shaped pads of the gecko's foot scale up nicely as the glazier's suction cups used by window repairmen, and a number of "human fly" stuntmen, such as George Goodwin, have adapted these tools for climbing—especially on glass or smooth metal. Porous surfaces like wood and plaster and cement will not hold a good vacuum, so are not climbable in this way. Usually.
Enter a German inventor named Gerald Winkler, whose "Gekkomat" climbing apparatus is powered by tanks of compressed air, and uses a combination of suction and friction to allow a human up to 550 lbs. to climb irregular or porous surfaces for around half an hour, or smooth ones for up to two hours. This is real-life superhero equipment, capable of dealing with vertical walls and even horizontal ceilings, although with hands and feet the size of hubcaps, our would-be vigilante might find the actual apprehension of criminals a bit difficult. Maybe a sidekick could handle that end of the business.
He's got the world on a (sticky) string
One final possibility in the climbing department is Spidey's own web goo, which resembles both natural spider silk and the new "sticky foam" sprays used by our police and armed forces. Both materials are strong, rapidly curing polymers capable of trapping an unwary victim, so a coating of web goo, followed by a secretion of fast-acting, fast-evaporating solvent, might provide enough stick-and-release for our wall crawler.
Where the web goo comes from is the subject of considerable debate. Stan Lee has always maintained that it's Peter Parker's own invention, mixed in secret and shot from a pair of dispensers on the webslinger's wrists. However, Columbia's new movie shows the material being produced directly by a gland in Parker's body. Perhaps both views are true; Canada's Nexia Biotechnologies has recently unveiled genetically modified goats which produce the spider-silk protein, "fibroin," from their milk glands. Since the goats' udders lack the spidery "spinnerette" organs which form the fibroin into fibers, the goats cannot actually spin webs, but it isn't difficult to imagine a mechanical web shooter which performs this function.
It's worth noting that most spiders don't "shoot" their webs at all, but lay them out carefully by hand. However, the existence of "spitting spiders," sticky foam dispensers and Silly String does show that the concept is feasible at least at short range. And since spider silk has three times the tensile strength of steel, it's quite reasonable for Spider-Man to swing around on cables of it.
Of course, centrifugal force is a major consideration: At the bottom of his arc on a 30-meter webline, Spidey's hand will be supporting up to three times his own weight. Without truly superior strength and clinging power, our hero is set for an ignominious tumble to the streets below. Spider silk is also highly elastic, and assuming a thickness of half a centimeter and a Spider-Man mass of 70 kg, the 30m webline (if it's actual silk) will stretch to double its length at the bottom of the swing. Wheee! This will have complex dynamic effects which make the journey more like a brawl in Thunderdome than a swing through Tarzan's jungle. Fortunately, Peter Parker doesn't appear to suffer from motion sickness.
I'll also note that this one cable, all by itself, requires half a liter of fibroin fluid! A more frugal webslinger could get by with only 0.05 liters (about one-seventh of a soda can), making a thread half a millimeter thick, which would elongate by 475% during the swing. Spidey might have to run along the ground for part of the way, before bungeeing back up into the sky again! Also, not only is this cable thin enough to sever a hand under these large forces, but the strain on it is very close to the failure point of the fibroin material—just an eensy bit more force and the thread will break. Never doubt it: A superhero needs special equipment, guts and a lot of luck. Still, these figures are for a full arc from a web shot horizontally. More typically, the webs are shot upward at an angle, and the arc is fairly shallow as Spidey swings first from his left hand, and then from his right, brachiating along between the towers of downtown. In this case, the forces are milder, and the bungee effect is less pronounced.
The most intangible of Spider-Man's abilities is the "spider sense" that alerts him to danger. Real spiders accomplish this by having eight eyes, pointing around in all directions, and several dozen "ears" on their many elbows, and taste organs in their skin, and smell organs on the tips of their feet, and little hairs all over which are sensitive to the minute air currents of moving objects. There is no evidence that Spider-Man has any of these, so I'll point once again to methamphetamine, whose users are notably jumpy and alert to danger (one might almost say delusionally paranoid).
I don't want to start any rumors, but I'm guessing Peter Parker didn't have to take a blood test to land that photography job at The Bugle.
Wil McCarthy is a rocket guidance engineer, robot designer, science fiction author and occasional aquanaut. He has contributed to three interplanetary spacecraft, five communication and weather satellites, a line of landmine-clearing robots, and some other "really cool stuff" he can't tell us about. His short fiction has graced the pages of Analog, Asimov's, Science Fiction Age and other major publications, and his novel-length works include Aggressor Six, the New York Times notable Bloom, and The Collapsium.
