The Physics of Superheroes: Spectacular Second Edition (32 page)

Fig. 25.
A scene from
Amazing Spider-Man # 9,
where the supervillain Electro simultaneously demonstrates an advanced concept in electromagnetism and a significantly less sophisticated fashion sense.

Dillon found that his body could store an electrical charge that enabled him to hurl lethal bolts of electricity. Stories featuring Electro would frequently show him charging up his body at some “abandoned” power station, standing between two transformer towers and letting the electric current flow through his body. (The fact that New York City had fully functioning power stations lying dormant throughout town, available as hideouts for various supervillains, surely accounts at least in part for the high utility bills city residents must now pay.) Fully charged, Dillon could project lightning bolts from his hands, though sometimes he would discharge through other parts of his body. Once his stored charge was depleted, he was basically powerless until receiving another charge. Essentially, the freak accident on the power line turned Max Dillon into a walking rechargeable taser gun.

What does it mean to have “electrical powers,” such that one could hurl electrical bolts at the police and costumed super heroes? Anyone who has shuffled his feet through shag carpeting on a dry winter day and then touched a metal doorknob has verified that matter is composed of electrically charged elements. Unlike the mass of an object, which is always positive, electrical charge comes in two varieties and is arbitrarily labeled “positive” and “negative.” The expression “opposites attract” may or may not be a reliable guide in affairs of the heart, but it does accurately summarize the nature of the force between positively and negatively charged objects. Two objects with opposite charges will be pulled toward each other with an attractive force. Similarly, two objects that are electrically charged with the same polarity, either both positive or both negative, will repel each other. When a shipping box picks up an excess electrical charge due to random frictional rubbing, this charge can be transferred to the foam packing peanuts inside the box. All of the lightweight foam bits then have the same charge, repelling each other and flying into the air when the box is opened.

The negatively charged electrons in an atom are attracted toward the positively charged protons in the nucleus by the attractive electrostatic force. The more protons there are, the larger the positive charge and the greater the force pulling the electron into the nucleus. However, the more electrons in an atom, the greater their mutual repulsion. These two forces—the attraction by the nucleus and the repulsion by the other electrons—tend to roughly cancel out, which is why a uranium atom with ninety-two electrons and an equal number of positively charged protons in its nucleus is approximately the same size as a carbon atom, with six electrons and six nuclear protons.

The attractive force between two oppositely charged objects, or repulsive force for two objects with the same charge, has, remarkably enough, the same mathematical form as Newton’s law of gravitational attraction described in Chapter 2. That is, the force between two objects that have electrical charges (charge 1 and charge 2) is given by the equation:

This expression, attributed to the eighteenth-century French scientist Charles Coulomb, is nearly identical to Newton’s gravitational expression, except that instead of the charge of two objects, we multiplied their masses, and the constant wasn’t called “k” but “G.” Recall from Chapter 2 that Newton’s law of gravity described the force between two masses (mass 1 and mass 2) by the expression:

Mathematically, these two expressions for Force are equivalent when “mass” is replaced by “charge” and the constant G is renamed as the new constant k. Because electric charge is not the same quantity as mass, the units of the constant k are different from the units of the constant G in order for both equations to have the units of a force.

More important than k having different units from G is the fact that the magnitude of k is very much larger than the magnitude of G. Consider a single proton in the nucleus of a hydrogen atom, orbited by a single electron a certain distance away. The attractive force of gravity pulls the electron in toward the proton, and there is an additional attractive force since the positively charged proton is pulled toward the negatively charged electron. The magnitude of the charge on the proton is exactly the same as that of the electron, where the charge of the proton is labeled positive by convention and that of the electron is considered negative. While they may have equal but opposite charges, the mass of the proton is nearly two thousand times larger than that of the electron. However, when k in Coulomb’s expression is multiplied by the product of the electron’s and proton’s charge for a given separation in an atom, the resulting force is ten thousand trillion trillion trillion (a one followed by forty zeros) times stronger than the gravitational attraction. On the atomic scale, gravity is irrelevant, and matter is held together by electrostatics. There’d be no molecules, no chemistry, and no life without static cling.

If gravity is so much weaker than electrostatics, why does gravity matter so much for planets and people? Because it is always attractive. Two masses, no matter how big or small, will always be pulled toward each other due to gravity. While there is such a thing as antimatter, it has a positive mass, and therefore has a normal gravitational attraction to other matter. As far as anyone has been able to experimentally determine, gravitational attraction between masses is always attractive. Certain puzzling astronomical observations have recently been interpreted as indicating the presence of some sort of “antigravity” associated with a mysterious quantity termed “dark energy.” However, this explanation is somewhat controversial, and at the time of this writing, scientists don’t have the foggiest idea what dark energy is.

The situation with electricity is very different. The fact that electrical charges come in two different types—positive and negative—introduces the ability to screen out electric fields. An electron orbiting a proton feels an attractive pull. A second electron brought near this arrangement is pulled toward the proton but is pushed away from the first electron. Until the second electron comes very close to the proton, the sum of the pull and push cancels out, and there is no net force on the second electron. If we could as easily screen out gravitational attraction, then levitating devices such as the Fantastic Four foe the Wingless Wizard’s anti gravity discs would be commonplace. Regardless of whether it has a positive, negative, or no (neutral) electrical charge, all matter has a positive mass and feels an attractive gravitational pull from other matter. In this way, gravity always wins in the end and pulls everything together—even those objects that are electrically neutral.

But make no mistake, electrostatics is the stronger force. Consider the form of Coulomb’s force equation stated earlier. If you had only 10 percent more negative charge than positive charge on your body, the force of electrostatic repulsion would be large enough for you to lift an office building that had a similar 10-percent excess negative charge. On the other hand, while the mass of the office building is much greater than your own, you are not gravitationally bound to the building, despite the occasional dictates of the workplace and your boss.

As he runs, the Flash should pick up an enormous static charge due to the friction between his boots and the ground. This friction is necessary in order for him to run, and an accumulation of excess charge as the Scarlet Speedster sprints is similar to what happens when we rub our feet along a carpet in the winter. The friction of our feet rubbing against the carpet, which is a violent process on the atomic scale, results in the transfer of electrons, which spread out over our bodies. These excess charges repel each other and don’t want to stay on you. When you approach the doorknob, a path for the charges back to the Earth (which is able to take up a few more or less electrons without bother) becomes available. If the charge is large enough, the electrons will jump through the air, the same way a lightning bolt allows the excess charge in a thun dercloud to discharge to the ground. When driving, your car will frequently pick up excess charge due to the friction between the tires and the road, which you can remove by touching the metal door once the car has stopped. The discharge is painful for two reasons: The surface area of your fingers is very small, so the current per area is large, and your fingertips have more nerve endings, so they are more sensitive to the current. Better to touch the car frame or the doorknob with your elbow, or you could adopt my strategy of draping your entire body over the hood of the car. The arch looks you’ll receive will be a small price for the reduced pain (and you’ll find that over time few people will want to park near you!).

This friction- induced electrostatic buildup (technically referred to as “contact electrification”) was acknowledged in
Flash # 208.
The Flash had just finished saving the citizens of Keystone City,
⁵⁵
yet again, from an attack by a subset of his Rogues Gallery, and was being thanked by a group of bystanders. In addition to requests for his autograph, one person patted the Flash’s shoulder and, receiving a shock, noted, “Hey, check it out! His uniform is covered in static electricity!” This excess charge should in general discharge to the first metallic object near the Flash that was connected to electrical ground as soon as he stopped running. The fact that this contact electrification was only noticed in 2004 (and not in the previous fifty years of Flash comics) suggests that during the majority of his crime-fighting career, the Flash, in addition to possessing an ability to ignore air resistance and punishing accelerations, was similarly immune to electrostatic buildup.
⁵⁶

Returning to Electro, his electrical powers no doubt stem from the fact that he is able to store very large quantities of a net electrical charge, either all positive or all negative, within his body. He can then discharge himself at will, in a similar fashion as the spark that leaps from your fingertip to the brass doorknob mentioned earlier. This is consistent with the fact that Electro needs to charge himself up before employing his powers, and if he lets loose with too many electrical bolts, he is, in essence, depleted and susceptible to a good right hook.

More than sixty years ago, a Swiss engineer’s hiking frustration led to a technological innovation. George de Mestral’s investigations into why burrs clung so tenaciously to his woolen hiking pants resulted in the invention of a fastener consisting of millions of tiny hooks and loops, and gave the world Velcro. More recently, Robert Full, Keller Autumn, and coworkers have discovered that the gecko lizard’s ability to climb up smooth walls and ceilings can be traced to millions of microscopic hairs on the lizard’s toes called “setae.” But without miniature hooks in the walls or ceiling, what holds the fibers and the attached gecko in place? Static cling!

The fibers in a gecko’s feet are electrically neutral, but the lizard does not need to shuffle across a shag carpet to cling to a wall, because he makes use of fluctuations of charge in his setae. The electrons in the fibers in the gecko’s toes are constantly zipping around. Sometimes a few more electrons are on one side of the fiber, making that side slightly negatively charged, while other times a few less electrons are on that side, making it slightly positively charged. If the side of the fiber closer to the wall is, just for a moment, slightly negatively charged, then it will induce a slight positive charge in the wall (by repelling those electrons in the wall closest to the surface, exposing the positively charged ions) and an attractive force between the fiber and the wall will result. You would expect that this force (known as the van der Waals force) is very weak, and you would be right, which is why the gecko has millions of these fibers in each toe, so that the total attractive force can be large enough to support the lizard’s weight.