The Physics of Superheroes: Spectacular Second Edition (34 page)

With so many stories being created every month, there was simply no way that Lee had the time to craft full scripts for all of these comic books. Meanwhile, the artists working for Marvel were freelancers, and would bring in the artwork for one issue, get paid, and then need to pick up instructions for the next issue’s story line (if they weren’t working, they weren’t being paid). I should mention, by the way, that the artists working for Marvel at the time were some of the very best in the business and included such titans as Jack Kirby, Steve Ditko, Don Heck, John Romita, and Gene Colan. The talent of these artists is reflected in the fact that they were able to continue making a living through the comic-book Dark Ages of the mid-1950s, when the entire industry was on the verge of extinction thanks in part to the “Seduction of the Innocent” brouhaha. Consequently, they were experts in how to tell a story in graphic terms, and did not need a comic-book writer holding their hands with panel-by-panel instructions of what should be drawn on every page.

Stan Lee, therefore, hit upon a clever solution to the problem of not enough time and too much available talent: Let the artists tell the story. Lee would write up a brief synopsis, varying in length from a few pages to a few paragraphs,
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describing what the latest issue’s story line would be. In essence, he gave the artists a plot outline of the major points of the story, such as who the villain would be and what his powers were and how he obtained them, as well as how the hero would lose the initial skirmish with the villain, and finally the clever stratagem that would provide the hero’s victory by the issue’s conclusion. The artists would then go back to their studios and construct a graphic story that followed Lee’s synopsis. When the finished artwork would return, Lee would then write the captions and dialogue in each panel, and the comic book would be ready to be sent off to the printer. Consequently, both Lee and the artists could legitimately be said to co-write or co-plot any given issue of a comic book created in the Marvel style. It is therefore on both Lee’s and Ditko’s shoulders that the blame for Spidey’s ignorance of basic electrical-current theory must be placed.

Lee and Ditko may not have had a firm grasp of the concept of electrical grounding, but they understood that electricity plus water equaled a short circuit. The climax of Spider-Man’s battle with Electro in
Amazing Spider-Man # 9
came when Spidey grabs a nearby fire hose, such as used to be commonplace in most professional buildings before the advent of ceiling-based sprinkler systems, and doused Electro with a heavy spray of water. As Spider-Man grabs for the hose and turns open the main pressure valve, he thinks “Say!! What kind of science major am I, anyway? Why didn’t I think of this right away??
”
As he lets Electro have a full blast, he continues, “Water and electricity just don’t mix!!!
”

Well, as mentioned above, we are beginning to have some doubts about just what kind of science major Peter Parker is, but he is certainly correct that water and electricity don’t mix. This is because city water, while technically electrically neutral, contains a high concentration of impurity ions. Ordinary tap water is consequently a pretty good conductor of an electrical current. Electro is at a high potential difference, which is why he is such a lethal threat to superheroes. By dousing him with water, Spider-Man essentially connects a wire between Electro and ground, allowing the large excess charge Dillon has stored to flow out of his body. This is one physics lesson that seems to be well learned in the Marvel universe. When Electro is bested by Daredevil in the second issue of that hero’s comic, the police keep him drenched with a water hose (Electro, that is, not Daredevil) in order to safely transport him to the paddy wagon and the station house.

HOW ELECTRO BECOMES MAGNETO WHEN HE RUNS—
AMPERE’S LAW

I SUPPOSE THAT we should cut Lee and Ditko some slack for their goof described in the previous chapter concerning whether metals can carry an electrical current if they’re not connected to ground. The rush to put out a monthly comic book, combined with the need to tell an exciting story, has certainly accounted for more than a few science blunders at both Marvel and DC over the years. As emphasized earlier, these comic-book tales were never meant to serve as physics textbooks. It is therefore all the more impressive that in the very same issue of
Amazing Spider-Man
that features Electro’s debut, we see a perfect illustration of one of the fundamental properties of electricity.

At one point in the story, following a brazen daytime bank robbery, Electro is shown escaping from the authorities by climbing up the side of a building, as easily as Spider-Man. The panel is reproduced on p. 197 in fig. 25, where we see one observer exclaim, “Look!! That strangely-garbed man is racing up the side of the building!” A second man on the street picks up the narrative: “He’s holding on to the iron beams in the building by means of electric rays—using them like a magnet!! Incredible!”

There are three feelings inspired by this scene. The first is wonder as to why people rarely use the phrase “strangely-garbed” anymore. The second is nostalgia for the bygone era when pedestrians would routinely narrate events occurring in front of them, providing exposition for any casual bystander. And the third is pleasure at the realization that Electro’s climbing this building is actually a physically plausible use of his powers. Utility-pole man Max Dillon (Electro) understands, as does the second passerby in the panel, that electric currents do indeed create magnetic fields. This phenomenon, termed the Ampere effect, was first noted by Hans Christian Øersted (for whom a unit of magnetic-field strength is named) and was fully explained by André-Marie Ampère (after whom the unit of electrical current, the “amp,” is named). Why does Electro’s control of electricity enable him to generate magnetic fields, and wouldn’t fairness therefore dictate that Magneto, the mutant master of magnetism, be able to control electric currents at will? The answer to this question reveals a deep symmetry between electricity and magnetism, found in both comic books and the real world.

We first must begin by defining an “electric field.” An electric charge at rest exerts a force on another electric charge. The farther away this second charge is, the weaker the force and, depending on its polarity, the second charge will be either pulled toward or pushed away from the first electric charge. We can therefore say that there is a “zone of force” surrounding this first electric charge. Another way to describe this “zone of force” is to say that around the first charge is an “electric field.” A second electric charge brought near the first charge will experience a force as it is being pushed or pulled by the electric field of the first charge. The strength of the electric field depends on the magnitude of the electric charge at this point and varies with its distance from the first charge—very close to it, the force on a second charge is large, while as the separation increases, the force decreases as the inverse of the square of the distance (from the Coulomb expression). If the separation of the two charges is doubled, the force goes down by a factor of four, and if the separation triples, the force is only one ninth as large.

There is another field that is created by an electric charge, but only when it is in motion, called a “magnetic field.” If an electrical current flowing through a wire is held near a compass needle, the needle will be deflected just as if an iron magnet had been brought near the compass (this was Øersted’s discovery). In fact, two parallel wires carrying electrical currents will, depending on the direction of the currents, either be attracted toward each other or repelled away from each other, behaving just as two magnets would when oriented north to south poles (attracting) or south to south (repelling). The magnetic field generated by Electro’s “electric rays” does indeed provide an attraction to the magnetic field of the iron beams in the building, enabling him to scale buildings or adhere to passing automobiles (as he did to attempt an escape in
Daredevil # 2
).

The force that arises between current-carrying wires is not electrostatic in nature. The wire is electrically neutral before the current flows, with the number of electrons in the atoms making up the wire evenly balanced by the same number of positively charged atomic nuclei. While a current is passing through the wire, an equal number of electrons enter at one end as leave at the other. The extra force between the wires, present only when carrying a current, is due to the magnetic field they create.

Why is this so? Why does an electric current create a magnetic field, which in all aspects is identical to that of an ordinary magnet? A key clue behind the phenomenon of magnetism is that it involves electric charges in relative motion. That is, the charges must be moving relative to each other.

If two electric charges are moving in the same direction at the same speed, then from the point of view of one of the charges, the other charge is stationary. In this case, the only force between the two charges, from their point of view, is electrostatic. To someone stationary in the lab, however, there is an extra force associated with the motion, called magnetism. That the magnetic force is connected with the relative motion of the electric charges suggests that there’s a simple four-word explanation for the phenomenon of magnetism: Special Theory of Relativity. To explain how Einstein’s theory from 1905 is able to account for magnetic fields will require more than four words, but we’ll try to get by without mathematics.

I’ll use a nice argument given by Milton A. Rothman in his excellent book,
Discovering the Natural Laws,
that illustrates how relative motion of charges creates a force, where the force is absent when the charges are stationary. Think about two very long train tracks lying next to each other, one with a large number of negative charges equally spaced exactly one inch apart, the other with an equal number of positive charges, also one inch apart. We’re making this up as we go along, so we’ll assume that these rows of negative and positive electrical charges extend for miles and miles, and this way we won’t have to worry about running out of charge as they move along the track. We next bring in a test charge—a positive charge, for sake of argument—some distance from these lines of charges. This test charge will feel no net force, as it is pushed away from the line of positive charges as strongly as it is attracted to the negatively charged array. Now the two tracks start moving at the same speed in opposite directions, the negatives to the left and the positives to the right. If the test charge is stationary, then the same number of negative charges and positive charges, in a given length, pass by it, and there is still no net force. An extra force develops, however, if the positive test charge moves to the right at the same speed as the positive charges on the track, also moving to the right.

Back in Chapter 11, when we considered the relativistic effects of the Flash’s great speeds, we discussed the property of the Special Theory of Relativity that, from the point of view of a stationary observer, the length of the moving object is contracted. From the positive-test charge’s “point of view,” moving along with the same speed and direction as the positive charges, it is stationary compared with this array of positive charges. The test charge therefore sees the positive charges on the track as still being spaced one inch apart. The array of negative charges moving in the opposite direction, on the other hand, will be contracted in length and will therefore be closer than one inch apart to the moving test charge. The electrostatic push and pull on the test charge is now unbalanced, and it will now feel a net attractive force. We give this extra force, present to the outside observer when charges are moving relative to each other, a special name: magnetism. From this argument it is clear that a moving object having no net charge (that is, electrically neutral) will not feel any extra force, which is consistent with the experimental observation that magnetic fields are created only by positive or negative currents.

Earlier we noted that the friction between the Flash’s boots and the ground should transfer static charge to the Scarlet Speedster. Because moving electric charges create magnetic fields, it is puzzling that the Flash, whenever he sprints at superspeed, does not simultaneously generate an enormous magnetic field that would pull every iron object not nailed down (and quite a few that are) after him in his wake. We will have to chalk both this missing electric charge and corresponding magnetic fields to the efficacy of his “aura,” that also enables him to avoid the deleterious effects of air resistance.
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It is indeed strange that magnetism is explained by invoking the special theory of relativity for moving electrical charges, as in general it’s easy to ignore relativistic effects when the object in question is moving much slower than the speed of light. There’s only a very slight error if we neglect relativity even when the object is moving at one tenth of the speed of light. Nevertheless, for electrical charges moving much slower than light-speed, there is still a relativistic effect through the creation of a magnetic field. The effect is smaller, to be sure. How much smaller? One can show mathematically that the upper limit of the magnitude of the magnetic field created by a moving charge is equal to its electric field divided by the speed of light. The speed of light is a large number; so, for a given electric field, the magnetic field associated with the moving charge will be quite weak, but it will be there nonetheless. Increasing the magnitude of the electrical current, either by moving more electrical charges, or having them move faster, generates a larger magnetic field.

An understanding of Ampere’s Law, connecting electrical currents and magnetic fields, makes possible useful devices such as electromagnets. An electromagnet is a coil of wire wrapped around an iron magnet core. The current flowing through the coils creates a magnetic field, enhancing that from the iron alone. Just such a device is constructed in
Superboy # 1,
when the Teen of Steel faces off against a gang of thieves who are running around town in a fleet of personal tanks stolen from an Army-surplus depot. The “Smash and Grab Gang” of crooks (yes, that was really their name) then uses these tanks to break into banks and cause mayhem. While he could easily fly around and collect all the tanks by hand, Superboy decides on a more technological approach, as shown in fig. 27. “I’ll only need that locomotive, a dynamo from that power-house, and a few miles of wire,” the Teen Titan explains to a recent victim of the crime gang. Superboy flies a large electrical dynamo to the empty coal car behind a large locomotive engine, and notes, “This dynamo will give the current I need when it’s hooked up! Now for the windings—.” In the next panel, we see him take “a few seconds to wind these miles of wire” as he loops them around and around the body of the locomotive. On the next page (fig. 28) we see the payoff as Superboy starts up the engine (presumably there is enough coal to get it going) and announces, “I’ve got the biggest electromagnet ever made, and one that can go places!” The train tracks conveniently pass not only through the center of town, but right by the vandals’ tanks. “What happened? We’re flying!” one crook cries out as his tank is drawn toward the magnetic locomotive. “It’s that locomotive,” says a more informed villain. “It’s a magnet drawing our steel tanks!”