The Physics of Superman
When we examine Superman, we need to remember that, in a sense, we’re examining all the superheroes who follow. Superheroes have always been created with broad brushstrokes. Not a lot of time was spent on deducing the limits or nonlimits of our super characters. Even less attention was paid to their interaction with ordinary people and objects. When Superman lifts a car over his head to shake criminals to the ground, no one ever questions why the car doesn’t fall to pieces. Nobody questions how Superman stays perfectly balanced on Earth while waving over his head an item that has a mass twenty times greater than his own.
How often have we seen Superman fly down and pull a car up by the roof into the sky? In the real world, there are few vehicles that would even hold together if Superman yanked them up by the roof. The car would probably continue forward, with the roof ripped off and held by Superman. Every time Superman lifts a building into the air, why don’t all the bricks, held together by cement and pressure, suddenly start falling apart? Those are the types of ordinary problems that seem never to occur in any superhero adventures. Basically, superheroes perform super acts and the logic squad cleans up afterwards.
In Superman’s first appearance in the 1938 Action Comics, we’re informed “that he could leap one-eighth of a mile; hurdle a twenty-Story building . . . raise tremendous weights . . . run faster than an express train . . . and that nothing less than a bursting shell could penetrate his skin!”
The explanation of Superman’s powers, as given in Action Comics #1, left much to the imagination. Their main premise was that Superman came from a civilization much more advanced than ours and thus the inhabitants were physically more advanced than humans. By extrapolation, this argument implies that modem man is physically much stronger than Cro-Magnon man or Neanderthal man. Of course, our ancestors lived only a few hundred centuries before us, while Superman’s race was described as being millions of years ahead of ours. A full-page illustration in Superman #1 (Summer 1939) gave a “scientific explanation of Superman’s amazing strength.”
“Superman came to Earth from the planet Krypton, whose inhabitants had evolved, after millions of years, to physical perfection. The smaller size of our planet, with its slighter gravity pull, assists Super-man s tremendous muscles in the performances of miraculous feats of strength.”
Thus, there were two explanations for Superman’s extraordinary powers. He was an alien from a planet not in our Solar System, and the weak gravity of Earth compared to the gravity of his home world of Krypton gave him amazing strength. Both concepts came right from the pages of science fiction magazines of the time, and few readers questioned the logic of either assumption.
Let’s assume Superman could indeed come to Earth. What powers would he possess that would make him a superman when compared to humans? Going back to the original Superman of Action Comics #1, it’s clear he has tremendous strength and can jump great distances, but he never flies. In Superman #4, for example, he runs from Metropolis to Oklahoma. Siegel and Shuster created a character they thought was believable based on the science of the time.
There was no explanation for flight, so the best Superman could do was jump.
As the years passed and competition increased, Superman’s powers grew as his creators continued to change the character to meet the demands of an ever-increasing audience. By 1943, Superman could fly at speeds faster than light (another impossibility). Needless to say, as his powers grew more incredible, so did his strength. In early issues of Action Stories, Superman lifts an automobile over his head. Within a few years, he’s carrying buses packed with astonished riders. After a few more years, he’s carrying ocean liners. By the 1960s, he’s moving planets.
Siegel and Shuster’s original comic book concept was that Superman’s tremendous strength was the result of being born on a high-gravity planet. Earth’s gravity was much weaker than that of Krypton, so Superman was able to lift heavy objects due to the difference in gravitational fields.
In Superman #58, Supermans powers are explained as follows
“Everyone knows that Superman is a being from another Planet, unburdened by the vastly weaker gravity of Earth. But not everyone understands how gravity affects strength! If you were on a world smaller than ours, you could jump over high buildings, lift enormous weights . . . and thus duplicate some of the feats of the Man of Steel!”
Which leads to our second basic question about Superman: How strong must Krypton’s gravity have been to endow Superman with such incredible strength? Answering this question requires we first answer another: How massive was the planet Krypton that it had such high gravity?
Superman appears to weigh approximately 100 kg (220 lbs). An athlete in top physical condition can lift his own body weight. Running and throwing a heavy object might not be so easy. For our study, we’re going to assume that Superman is 1,000 times stronger than an ordinary Earthman. That would mean he could lift 100,000 kg or approximately 220,000 pounds. This is approximately the weight of three filled semi-trailer trucks or a DC-9 airplane without fuel or passengers. Cranes used to construct bridges can handle about that weight, so we’d have a Superman still well within the bounds of human imagination. Such strength would even enable him to leap a mile with one jump, thus approximating flying in the eyes of most people.
The force necessary to lift an object on a planet is equal to the mass of the object multiplied by the gravitational force present on that planet. Thus, a human who could lift 100 kg on Earth could lift 600 kg on the Moon, which has one-sixth the gravity of Earth. Which would imply that for Superman to be 1,000 times stronger on Earth than he is on Krypton, Krypton would have to be 1,000 times as massive as the Earth.
Earth’s gravity is 9.8 meters/sec squared, or for simplicity’s sake, 10 meters/sec squared. Multiplying that number by 1,000 gives us the gravity of Krypton, 10,000 meters/sec squared.
Could a planet exist with such a gravitational field? According to Brother Guy Consolmagno of the University of Arizona, a planet with even fifty times the gravity of Earth “is essentially impossible to construct, given the physics of solid matter as we understand it.”
Put in even simpler terms, “a body with . . . a surface gravity of 10,000 in/sec squared would have a mass of 6 x 1033kg …, which would be 3,000 times the mass of the sun.”
According to the basic laws of physics, Krypton is impossible. Moreover, for people resembling us to live on Krypton, they’d need muscle and bones 1,000 times stronger than human muscle and bone. No such material exists to create bone or muscle, or the complex internal organs necessary for life as we know it.
On a planet with gravity 1,000 times that of Earth, would it be possible to send a rocket ship, especially a small one as seen in numerous issues of Superman and Action Comics, to Earth? The escape velocity (the speed necessary to break the gravitational pull of a planet) of Krypton would be enormous, approximately 11,000 km/second. That’s about 1/30 the speed of light. No chemical reaction in the universe could produce enough energy necessary to achieve such velocity.
In the 1960s, the explanation for Superman’s powers was revised: his super strength, ability to fly, and more came not only from the high gravity of Krypton but also from growing up under a yellow sun instead of a red one. Unfortunately for Superman, light is light. The light from a red sun would merely have a smaller occurrence of high frequencies than the light from a yellow sun. Infrared light would be more common, but that’s about it. Red star or yellow star, Superman’s powers would be the same.
Superman is one of the most fascinating characters in comic books, and he’s one of the most recognizable characters on Earth. He’s one of those people we wish could exist, but doesn’t. Visitors from other planets are possible. Superman’s not.