The Science that Makes Superman So, Well, Super

The newest movie installment of the Superman franchise opens this week, but some Superman mysteries remain unanswered. Physics professor James Kakalios explains the physics behind the superhero's famous powers.

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(Soundbite of TV show "Superman")

Unidentified Announcer: Faster than a speeding bullet, more powerful than a locomotive, able to leap tall buildings in a single bound...


For six seasons, those words announced the start of every episode of the Superman TV series starring George Reeves as the Man of Steel. Later this week, a new incarnation of the superhero from the Planet Krypton will land on thousands of movie screens around the country. Now ponder this. How fast does Superman have to fly to outpace a bullet or a locomotive? Does he have to get a running start before leaping over that tall building? To learn more about the science behind Superman's super powers, we've contacted James Kakalios. He teaches Physics at the University of Minnesota and he's the author of the Physics of Superheroes, published last year. He joins us from WDST in Woodstock, New York. Welcome to the program.

Professor JAMES KAKALIOS (University of Minnesota): Thank you very much for having me.

HANSEN: Let's start with Superman's home planet, Krypton. What is it - is it the fact that he was born there? Why does that make him different from humans born on earth?

Prof. KAKALIOS: Well, as originally conceived in 1938 by Jerry Siegel and Joe Shuster, the two people who created Superman, Krypton had a larger gravity than that of earth. So someone coming from Krypton to Earth, finding themselves in a much weaker gravity, could lift objects that are much heavier than what we can do on Earth, because their muscles and skeleton structure are adapted to a much heavier gravity. Originally, he couldn't move planets. He could lift a car over his head. He couldn't fly. He could leap great distances. Again, all because his muscles were adapted to a much larger gravity.

HANSEN: Okay, so he couldn't fly initially, but he was able to, what, leap tall buildings?

Prof. KAKALIOS: Leap tall buildings in a single bound, yes.

HANSEN: All right, does he have to get a running start?

Prof. KAKALIOS: In the comics, frequently he wouldn't. He would crouch down, his steely muscles would press against the ground, and thanks to Newton's Third Law of Motion, that for every action there is a reaction, when he pushes against the ground, the ground pushes back against him, lifting him up, up and away. Well, how fast would you have to be going, lifting up off the ground, so that as you slow down due to gravity you would still clear a tall building, say 660 feet? Your liftoff velocity off the ground has to be nearly 140 miles per hour.

HANSEN: Can you explain his hearing? He has super hearing.

Prof. KAKALIOS: His hearing is beyond super. His - because he can hear things before they happen. He can hear things. There have been scenes in the comics where he's on the other side of the planet and he hears the crack of a gun and he flies at super speed and manages to catch the bullet. But the problem is that the sound from the gun emitted at the same time that the bullet leaves the muzzle and the sound travels at only, say, 1,100 feet per second, whereas the bullet is traveling at many thousand feet per second, and so by the time the sound reaches his ears, the bullet has already reached whatever target it was aimed at.

It's equivalent to when we see a flash of lightening and then we hear the thunder many seconds later from a distance storm. By the time you hear the thunder, you can't possibly stop the lightening. The lightening has already happened in the past.

HANSEN: But didn't Superman have time travel capabilities?

Prof. KAKALIOS: Ah yes. I get asked this a lot. In the very first Superman movie, Superman travels at great speeds around the planet and manages to cause time to go backwards, and I'm always asked is this possible, and my standard answer is I wish.

HANSEN: Well, I figuring that's how he stopped, you know, he got there before the bullet.

Prof. KAKALIOS: Well, or maybe he'd hear - yeah, that could be. If he could somehow do that or had some sort of telepathy or some other power or somehow the sound is also creating electromagnetic radiation in some means that we don't understand and he's detecting that.

HANSEN: Why does Kryptonite cause him to lose his powers?

Prof. KAKALIOS: Kryptonite in the comic books is described as a mineral, radioactive remnants of his home planet, and just as radioactive remnants of Earth are harmful to us, Kryptonite is harmful to Superman. And also as he became more and more powerful in the 1960s, you needed some mechanism by which crooks could slow him down somewhat so the story wouldn't be over in a single page.

HANSEN: In 1938, when the comics first came out, I'm thinking about the state of subatomic science, when that happened. Do you think super powers at the time seemed like a future reality?

Prof. KAKALIOS: Yes, to some extent. I mean, there was - there were all sorts of things in science fiction pulps and in the early comic books about what the world of tomorrow would bring. Atomic energy hadn't really broken through to the popular culture at that point. The notion of how we would achieve these flying cars and great powers in the late 1930s was through the harnessing of this new element, electricity. So it was electricity that was going to harness the flying cars and the jet packs in the world of tomorrow that we would have.

HANSEN: James Kakalios wrote the Physics of Superheroes and he teaches Physics at the University of Minnesota. Thanks so much for your time.

Prof. KAKALIOS: Thank you very much.

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