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A web of intrigue

Back in 1973, the violent death of a supporting character in issue 121 of The Amazing Spider-Man shook the world of comic book fandom to its very core. Gwen Stacy, girlfriend of the web-slinger’s alter-ego, Peter Parker, plunged from the top of the George Washington Bridge after being hurled over the side by the Green Goblin.

In a desperate attempt to save her, Spider-Man fires a web from his wrist and manages to grab one of her legs just before she hits the water. Tragically, however, his efforts are in vain. But what really killed her, was it the fall itself or the effects of being caught by the web?

It’s a conundrum which puzzled comic book fans for years, until James Kakalios – a physics professor at the University of Minnesota’s School of Physics and Astronomy – used science to figure out the answer.

“I was trying to come up with an exam problem which covered Newton’s second law of motion, which hadn’t been done 100 times already,” explains Kakalios, author of The Physics of Superheroes. “It then occurred to me that the death of Spider-Man’s girlfriend would be a textbook illustration of impulse and momentum.” Using scientific methodology, he worked out that it was actually the sudden halt caused by the web which was responsible for her death.

“She had a large momentum when falling and in order to change that momentum you have to apply a force. But the fact that the webbing stopped her in too short a time meant that the force needed to stop her was too large. That’s why we have airbags in our cars. Airbags not only spread the force over a larger area, but they also give a little bit. So they take a little bit more time to slow you down. The more time available to stop you, the less force needed to bring you to rest. It was the very sudden stop that resulted in a very large force which unfortunately led to Gwen’s death. So sadly, the same science and physics that now saves our lives in automobile crashes was responsible for the death of Gwen Stacy.”

Kakalios’ explanation has been accepted to such an extent that comic book writers now incorporate his scientific explanation into their stories. “Whenever Spider-Man needs to stop someone else who’s falling, you can actually see in his thought balloons that he’s solving the physics problem of trying to match his speed to the person who is falling, in order avoid causing too sudden a stop. So today’s storylines are still getting the science right.”

Even the Green Goblin himself has adopted our friendly neighborhood physics professor’s analysis, as Kakalios himself points out during a highly entertaining presentation available on YouTube. He explains to the audience that in Peter Parker Spider-Man comic number 45, the Green Goblin taunts Spider-Man over the death of Gwen Stacy, having realized that it wasn’t the fall that killed her, but the webbing. “I don’t know how well I do with my students or the readers of my book,” comments Kakalios, “but if I can teach a homicidal maniac like the Green Goblin about impulse and momentum, then I’m making a difference.”

To read a more extensive interview with Professor Kakalios, see the May issue of AkzoNobel’s A Magazine.


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