Henry Cavill as Superman
Henry Cavill as Superman Clay Enos—DC Comics/Warner Bros.

The Science of Superman

Mar 25, 2016
Jeffrey Kluger is Editor at Large for TIME magazine and the author of Apollo 8.

I didn't want it to come to this. I wanted to believe, I really did—and for a long time I did believe. But I don't anymore and it's time to speak out: Superman is a fraud—and he has been since the moment he put on that red cape.

I know, I know, it's a bad time to be bringing something like this up, what with the recent release of Batman v Superman and fans across the country taking sides in the big smackdown. There was a time when I would have been one of them—firmly in the Superman camp. What's Batman got, after all? Big car, bondage costume, no superpowers whatsoever. But say this for the Caped Crusader: the dude's honest.

You can't say the same for Superman. That whole super strength, super speed, born on Krypton thing is—sorry to say—a hoax. Call me a Super-birther if you want, but there are a lot of us out there and we won't be silent any longer. So let's look at the facts of the Superman story (sorry, the "facts" of the Superman story) and see what the science tells us.


Start with how he got here. Superman was born, we are told, as the baby Kal-el on the planet Krypton, but was launched toward Earth in a rocket ship built by his father, the scientist Jor-el, who had correctly predicted that Krypton was about to explode. The cause of Krypton's destruction is not explained, but all of the illustrations ever produced of the event show it blowing up—as if an explosive charge had been buried in its core. There is no natural phenomenon that could account for this.

It's possible that Krypton's orbit around its sun had begun to decay and was spiraling down to what's known as the Roche limit, a point about 2.4 times higher than the radius of the central body (in this case the star) at which point gravity tears the orbiting body (in this case Krypton) apart. Again, that's not what the pictures show, but let's give the Superman apologists that one.

Tougher to explain is Superbaby's rocket—a Tomorrowland sort of thing with a pointed nose, a fat body, a tapered aft end and pronounced fins. No precise measurements of the rocket are given, but using Jor-el as a scale and assuming he's six feet tall, the rocket would be about 20 feet long. Small but serviceable. The illustrations show a yellow-orange flame emerging from the rocket's bottom, which suggests an ordinary chemical engine. For simplicity's sake, let's stipulate a fuel mix of liquid oxygen and RP-1—or kerosene. Nothing warp drive-y or super fast about that.

Escape velocity from Earth's gravity is a minimum of 25,000 mph. Since we're told that Krypton was a larger planet with a more powerful gravity field, let's double that to 50,000 mph and assume that the rocket could sustain that speed the entire way to Earth. So when would Superbaby arrive?

Krypton, we are told, orbits a red star. The closest such star to Earth is Gamma Crucis, 88 light years (or 528 trillion miles) away. That means that even going as fast as it was, a rocket from Krypton would not reach Earth for 1.2 million years–by which time Superbaby would have long since turned into super bones. And before you start saying, Yes, but aging slows down when you fly through space, remember that's only if you're traveling at or near light speed, which is 186,282 miles per second, or 670,616,629 miles per hour. Superbaby's speedometer gets only 0.00745 percent of the way there.

Reaching Earth would have been the last—and certainly the ugliest—problem. If you know your Superman history, you know that his rocket landed in Smallville, on a farm owned by Ma and Pa Kent, who adopted him and named him Clark. Again, if we are to believe the illustrations, the rocket had no braking system or landing legs, and simply came skidding to a safe if bumpy landing, burying its nose slightly in the ground. Not likely.

Entering Earth's atmosphere at its 50,000 mile per hour cruising speed, the rocket would either have been torn apart by aerodynamic forces or been incinerated by the 5,000° F (2,760° C) heat of entry. If it exploded in the atmosphere—which would be likely, no matter how robust the ship—it would produce a 15-kiloton blast, roughly equivalent to the Hiroshima bomb. So goodbye Smallville. If it somehow reached the ground, it would produce a similar-sized blast, leaving a deep, wide crater as well.

None of these problems even touch on the issue of Superman's super powers. We are told that these result partly from the effect of a yellow sun on a person born under a red sun, and partly from the lighter gravitational pull of Earth, which contributes to Superman's ability to fly. But the light of a red sun has a very different electromagnetic profile from that of a yellow sun. The principle effect would be on plants, which would be a different color—reddish or yellow or even a dusky white—to make the best use of the available light. On Earth, the skin of humans and animals has adapted to the comparatively high ultraviolet output of a yellow sun. Superman, born under a lower-UV red sun, would have no such protection and would likely blister and burn.

Similarly, life in a lighter gravity field would not be a picnic. Yes, it might make Superman feel a little more buoyant for a while, but he comes from a species adapted to a higher gravity field, which means that over time his bones would decalcify, his joints would degenerate and his muscles would atrophy. Never mind flying; he'd be lucky to get out of his lawn chair.

I'll leave it to legal analysts to consider the other holes in the Superman story. Has he ever knocked before crashing through a wall and nabbing the bad guys? No, he hasn't. Has he ever read suspects their Miranda warnings? Not that I've seen. And as for evidence gathered by x-ray vision without a warrant? Can you say "inadmissible?"

Sorry folks, it's been fun, but the Supe has had us duped. Batman versus Superman? Put me down with the guy from Gotham, who is at least the real deal. If I ask nice, he may even give me a spin in that car.

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