The Science of Superman

"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.