Spiderman, Batman, the Fantastic Four, Ironman—seems like every time we go to the movies, there’s some guy in a unitard saving the world with acts of unnatural physics. We realize that these are works of fantasy, so we don’t get too upset when the science portrayed in them comes from some alternative universe. Nevertheless, it can be fun and instructive to point out the violations and/or conflicts with physical reality that we often encounter in film.
With that in mind, let’s take a brief look at eight of our favorite superheroes (and super-villains) and see what science can add to the discussion.
Adam Weiner is the author of Don’t Try This at Home! The Physics of Hollywood Movies
Superman is without a doubt the granddaddy of cinematic superheroes. Among his plethora of powers is the ability to fly. But how does he do that? Consider Superman simply hovering above the city. According to Newton’s Second Law, there must be some upward force to balance the downward force of his weight. Expressed mathematically: F – mg = ma = 0. But what could cause that upward force? One possibility is that he is able to emit high-velocity streams of air through the pores of his skin. As he forces the air out of his body, according to Newton’s Third Law, the expelled air must push back. And since Superman can survive in space, his lungs clearly aren’t needed for respiration—maybe they’re auxiliary air tanks.
A classic superhero conundrum: Where do these people get the energy to perform their superhuman feats? In the X-men movies, the “mutant” Storm is able to generate bolts of lightning at will. The energy released in a normal lightning bolt is about 500 million joules, which is equivalent to 120,000 food calories. To produce even a single lightning bolt, Storm would have to eat at least 60 times the recommended daily amount for an adult female. But we don’t see her constantly cramming down food in the movie, do we? If her stomach has mutated into some type of nuclear-fusion reactor, however—or better yet, a matter/anti-matter reactor—she could do it. Applying relativity (E = mc2), a single gram of mass converted completely into energy would yield 90 trillion joules. That’s 18 million lightning bolts!
One of the best ways to become a superhero is to be bombarded with tremendous doses of either cosmic rays or high-energy electromagnetic radiation. Although the effect of high doses of these types of radiation on humans (in the real world) are well-documented–the typical result is severe and debilitating cell destruction, followed by death–in the superhero world, this normally lethal experience results in a sequence of fortuitous “mutations.” These physiological changes always create abilities so astonishing that it might convince the most cautious of us to risk spending a couple days in the reaction chamber of a high-energy particle accelerator. After Bruce Banner exposes himself to a “lethal” dose of high-energy gamma rays, he transcends the expected symptoms of high-intensity radiation exposure and turns into the giant, green, astonishingly strongantihero we know and love.
The Human Torch
Johnny Storm, “the Torch” from the Fantastic Four comics and movies, combines each of the attributes that we touched upon with our first three superheroes. Having been exposed to “lethal” doses of cosmic radiation, Johnny (of course) develops formidable superpowers, just like the Hulk. He can fly, so as with Superman, we hypothesize that he forcibly expels gas at high velocities in the appropriate directions. And he also has a Storm-like propensity for churning up energy: Applying a little thermodynamics, we can calculate that he would have to generate around 940 million joules to “flame on” to a temperature of 5,000˚C. That’s pretty amazing considering that amino acids, the building blocks of life as we know it, break down at temperatures not much over 100˚F. How Johnny’s DNA is able to withstand such high heat is a mystery—not to mention that all the water in his body should long since be vaporized by the time he ignites.
X-man Magneto is a super-villain with the ability to create extremely powerful magnetic fields at will. Since magnetic fields are produced by electric currents, we can roughly approximate the current that might be coursing through Magneto when he’s up to one of his evil deeds. For simplicity, let’s model his interior electrical circuitry as a large solenoid (coil). The magnetic energy stored in a solenoid is given by: U = ½(μ0n2AL)I2 Where U is the energy, μ0 is a constant equal to 4π x 10-7 N/A2 , n is the number of coils in the solenoid, A is the cross-sectional area of the solenoid, L is the length of the solenoid, and I is the current generating the magnetic field. Phew. Let’s assume that Magneto’s internal solenoid has 1,000 turns, has a cross-sectional area of 0.01m2 and is approximately 2 meters long. Now let’s say that he uses that energy to lift a 1,000kg automobile 10 meters off the ground, increasing its potential energy by an amount U = mgh = (1,000 kg)(10m/s2)(10m) = 100,000 J. Plugging this value into the first equation and solving for I, we get that in order to store this much energy in his magnetic field, Magneto must generate a current of around 2,900 amps. That might not be so good for his heart–assuming he has one.
The Sandman, that reluctant super-villain from Spiderman 3, represents the metaphysical end point of all superpowers. He exists so far into the realm of fantasy that we just have to enjoy the astonishing computer graphics. Created in another generic high-energy-particle experiment, he is able to defy all laws of physical and biological probability. Somehow the matter in his body is all converted into sand (SiO2) in the ill-fated experiment. Apparently he has no internal organs (he can disintegrate and reconstitute himself at will), he can move without muscles, and he can even fly through the air as a cloud of dust. How does he produce energy? Can he metabolize food? How does he exert forces? Only the CGI magicians at Sony know for sure.
We all know that Batman has no superpowers. He’s just a highly motivated and highly skilled crime fighter with a lot of tech support. Or is he? In fact, to survive intact some of the impacts he undergoes, Batman actually might require super strength. A classic movie-physics blunder is the sudden stop. Now, we see this in a variety of forms in the original Batman. At one point, he plunges from the top of a building, along with Kim Basinger, to what appears to be certain death. Their fall, however, is arrested by a (decidedly inflexible) rope before hitting the ground. The thing is, it doesn’t matter if you hit the ground or not. If the time it takes for the rope to bring you to a stop is the same as if you hit the ground, then the force exerted on you will be the same in each case. In this example: Frope – mg = ma If a (acceleration) is large, so is F(rope). Ouch.
This one is for homework. Like Batman, Ironman has no superpowers, but he does have that amazing iron suit. In the trailer, we see him flying around in his nifty suit next to some military jets. There are little rocket flames coming out of the bottoms of his shoes, apparently providing the necessary thrust. Questions: What is he using for fuel? Based on what we see, it looks like rocket fuel. But where are his fuel tanks? And what volume of rocket fuel would he need to maintain the necessary thrust for at least several minutes? Would it be difficult for him to stay aloft in a stable trajectory? What does he wear underneath his suit? Stay tuned for answers (or at least conjectures) after the movie’s May 2 release. Adam Weiner is the author of Don’t Try This at Home! The Physics of Hollywood Movies