Microwave emitters (called magnetrons) were first created for radar applications during World War II. The cooking benefits of such a device were noted in 1945 when engineer Percy L. Spencer, studying the range of microwave energy emitted from a magnetron, noted that the candy bar he had in his pants pocket had melted. A follow-up experiment with popcorn confirmed the non-military usefulness for this device.
The easier it is for the atoms in an object to move back and forth and rotate with the oscillating electric field, the quicker the temperature of the object will rise. This is why liquids heat up faster than solids in a microwave. You can dig a deep hole in a large chunk of ice and fill it with water. Placing this “ice cup” filled with water in a microwave oven enables you to boil the water while the outside of the ice cup remains cold and solid. Don’t leave the ice cup in the microwave for too long, however, as it will also melt due to the ministrations of the alternating electric field, and in much less time than it would take in a conventional thermal oven.
From the descriptions given in the pages of Tales of Suspense and Iron Man comics, can we infer that the Melter’s weapon used the same principle underlying a microwave oven? Yes and no. Bruno Horgan first appeared in Tales of Suspense # 47 as an industrialist competitor of Tony Stark’s and was embittered when he lost a government contract to build tanks for the U.S. Army once the military discovered that Horgan was using “inferior materials.” Stark’s company then won the Army contract, despite the fact that there was an apparent conflict of interest in the information presented, as the report describing Horgan’s use of inferior components was written by Tony Stark himself. Later, one of Horgan’s laboratory testing devices (built with inferior parts) goes hay-wire while he is examining it and emits an energy beam that melts any iron it strikes.52 When Horgan realizes that the “inspection beam” he has created is actually a melting ray, he redesigns the device into a compact, portable unit and, donning a hideous blue-and-gray costume (sadly reinforcing various stereotypes concerning the fashion sense of engineers), he decides to destroy his enemies and make himself supreme (sadly reinforcing various stereotypes concerning the ethical sense of modern industrialists). His initial success against both Stark Industries and Iron Man is short-lived. Horgan is dumbfounded when he discovers, at the story’s conclusion, that his ray is no longer effective against the Golden Avenger. The Melter is unaware that Tony Stark has surmised his weapon’s weakness: It only works on iron! Creating a suit of “burnished aluminum” that appears indistinguishable from his regular suit of armor, Tony is able to fight the Melter to a standstill, and it is only the accidental melting of an iron drain above a sewer system that enables Horgan to escape to fight another day.
From this story, we must conclude that Horgan’s melting ray is not a portable microwave device. A microwave oven’s oscillating electric field grabs hold of any atom, while Horgan’s weapon works on iron (which contains twenty-six electrons) but not on aluminum (with thirteen electrons). Later on (in Tales of Suspense # 90), Horgan’s melting-ray gun would become even more specific, with dial settings for stone, metal, wood, and flesh (yeesh!). This specificity came to Tony’s rescue when, while in civilian clothes, he was shot in the chest by Horgan with this weapon, yet was unhurt. Bruno Horgan did not know that Tony Stark was also Iron Man, and was therefore unaware that Stark always wore his metal chest plate underneath his shirt (in order to keep the shrapnel near his heart at bay—see Chapter 24) and thus had the gun set to “Flesh,” when “Metal” would have been the correct setting.
Now, it is certainly true that when two atoms form a chemical bond, the lowering of energy is unique to the particular atoms participating. Thus, every chemical bond has its own energy signature, and it is, in principle, possible to design a microwave-type weapon that would be tuned to the chemical bonds in stone and not those in metal. Similarly, tuning the resonant frequency to water would make the beam effective against people (flesh) and not inanimate objects (metal). Just such a microwave-based “heat ray”—a weapon that induces extreme pain, similar to a second-degree burn, while the beam is incident on a person—has in fact recently been developed. The motivation for the development of such a weapon is for use in crowd-control situations, as the heat beam provokes a group of people to disperse from a given location in order to avoid the burning pain of the ray. However, regardless of how the frequency of the oscillating electric field is tuned, the bonds between iron atoms and aluminum atoms in their respective metals are much too similar for a weapon designed for melting iron to not also melt aluminum.
Of course, all this discussion about the Melter and Tony Stark’s metallic union suit raises a question that has long plagued modern man: If we can put a man on the moon, why can’t we put metal in a microwave? The answer is that the free electrons in the metal may cause some serious problems. Metals have high thermal conductivities, and can cause fires when in contact with paper in a microwave oven. Applying an external electric field to the electrons that are able to roam over the entire volume of the metal does more than just push them back and forth as it does the fixed atoms.
Any metal in a microwave is an isolated object, and there is no place for these pushed electrons to go—hence, they can build up at one end of the metal. If there are sharp points or edges, this pileup of electrons can cause a large electric field to be created inside the metallic object. If this electric field becomes larger than 12,000 Volts per centimeter, it can cause a spark, as the air is no longer able to insulate the high-voltage metal from the wall of the oven, and tiny lightning arcs will emanate. Depending on the metal’s curvature, the electric field induced may be less than the critical discharge level, while a sharp corner on a foil-covered stick of butter can be sufficient to create a spark that permanently scars the internal surface of the oven. (Personal note to my wife: Sorry, honey.)
16
ELECTRO’S CLINGING WAYS—ELECTROSTATICS
UP TILL NOW, we have focused primarily on how forces change the motion of objects, and the force that has concerned us almost exclusively has been gravity. Whether slowing Superman down as he leaps or speeding Gwen Stacy up as she fell, it is gravity that has been invoked when a force F is needed in Newton’s second law F = ma. But there are forces other than gravity in this—and the comic-book—universe.
Physicists have discovered that only four basic forces in nature are both necessary and sufficient to account for the wide range of complex physical phenomena observed. These forces are: (1) Gravity, (2) Electromagnetism, and (3) and (4), the unimaginatively named Strong and Weak forces.53 The latter two only operate inside atomic nuclei. The Strong force binds protons and neutrons together in close proximity within the atomic nucleus, and without it, the positively charged protons would repel each other and no stable elements other than hydrogen could exist. The Weak force is responsible for certain forms of radioactivity (such as the nuclear decays that led physicists to suggest the existence of neutrinos, as mentioned in Chapter 12), and without radioactivity, few superheroes or supervillains would exist. Nearly every force we encounter in our everyday dealings, aside from gravity, is electrostatic in nature. The forces generated by our muscles, the force the chair exerts on the seat of your pants to keep you from falling to the floor, the force exerted by the hot gases in your car engine’s cylinders that lead to locomotion, all these and many others are, in the final analysis, electrical. It is thus time for us to consider the twin forces of Electricity and Magnetism, and see how these wonder twin powers activate into one single force properly termed “electromagnetism.”
Very few superheroes have powers that are electromagnetic in origin. Two of the earliest Silver Age comic-book characters whose powers do utilize electricity and magnetism are Lightning Lad and Cosmic Boy. These heroes are from the future, and they first appeared in Adventure # 247 (April 1958) when they, along with Saturn Girl, traveled back in time in order to recruit Superboy into the Legion of Super-Heroes. Lightning Lad is able to create and discharge electrica
l bolts from his hands, while Cosmic Boy can control magnetic objects. The third founding member, Saturn Girl, possessed the superpower of mental telepathy, which we will argue later is intimately connected with electromagnetic-wave propagation. Consequently the three founders of the Legion are direct manifestations of electricity and magnetism theory in action.
The Legion hailed from the year 2958 (current stories take place in 3010) and was comprised of teenagers from different planets who each had a unique superpower. The concept of a club of teenaged superheroes in the future proved very popular with comic readers, and the Legion of Super-Heroes became a regular backup feature in Adventure Comics and eventually squeezed Superboy out of his own comic. The Legion membership grew over time, and currently boasts more than thirty heroes. All of the fundamental forces of nature, as well as several basic symmetries of physical laws, were pressed into service as the writers of Legion stories strained to develop a superpower for each hero. Legionnaires include Star Boy, who could make objects heavier while Light Lass could make them lighter, Element Lad, who was able to transmute one element into another (implying control over nuclear forces), and Colossal Boy, who could grow to great heights, while Shrinking Violet could miniaturize herself. Ferro Lad could transform himself into some sort of organic iron (an early, teen version of Colossus of the X-Men); as a kid I was profoundly shaken when he nobly sacrificed himself in order to destroy the Sun Eater in Adventure # 353.
While only a few heroes draw upon electricity and/or magnetism as the source of their superpowers, supervillains frequently employ these fundamental forces of nature as they seek either financial gain or world domination (and occasionally both). In particular, in the next few chapters, we’ll focus in turn on two such evildoers, Electro and Magneto (I leave it as a challenge to you, Fearless Reader, to determine which villain is associated with electricity and which one is involved with magnetism).
STATIC ELECTRICITY NATURE’S MOST POWERFUL FORCE!
When comic-book readers first met Max Dillon in Amazing Spider-Man # 9, he was a highly skilled but self-centered electrical-utility worker. When a coworker was trapped atop a high-tension line, Max was cavalier about his fate until his foreman offered Dillon a $100 reward (in 1963 dollars, worth about $700 today) to rescue him. Freeing the unconscious colleague and lowering him to the ground with a cable, Dillon then received an unanticipated bonus when he was struck by lightning while grasping the high-tension lines. Just as in the case of Barry Allen (the Flash), Dillon not only didn’t die or suffer any burns or neurological damage from this traumatic event, but he in fact gained the ability to store electrical energy that he could discharge at will in the form of lightning bolts.54
Dillon’s accident may have changed his body, but it left his antisocial attitudes intact. Realizing that he now possessed fearsome electrical powers, he designed a garish green-and-yellow disguise, with a bright yellow lightning-bolt-themed mask, and embarked on a life of crime as Electro, as shown in fig. 25. Personally, if I gained mastery over such a powerful, fundamental force of nature, I don’t think this would necessarily be the costume that I’d choose to wear in public. Perhaps if Max Dillon had not been such a rat, his friends might have gently provided some better fashion advice. But it is exactly such a pattern of bad choices that frequently leads these superpowered miscreants to a life of crime.
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:FORCE = K [(CHARGE 1) × (CHARGE 2)] / (DISTANCE)2
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:FORCE = G [(MASS 1) × (MASS 2)] / (DISTANCE)2
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 an
d 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.
The Physics of Superheroes: Spectacular Second Edition Page 22