When you're watching the Spiderman movies, you hardly ever stop to think about whether Peter Parker could actually physically swing from buildings on threads of silk. C'mon! Suspend your disbelief! It's a superhero movie! Jeez. Except as this mathematics professor points out, it's freaking possible.
According to Emory professor Skip Garibaldi, Spiderman's silk has a definite tinsel strength defined by Marvel Comics: 120 pounds per square millimeter. Turns out that's very similar to the strength of spider silk in nature—and the strength of steel. In other words, crazy strong. When Spiderman elegantly swings from building to building on very long strands he's using more than enough silk to comfortably glide without any physical jolts. The silk doesn't snap, Spiderman's shoulder doesn't pop out, and Mary Jane gets saved.
But what about stopping a speeding subway car with just silk? Again, it's possible. It just requires five tennis balls' worth of silk, which in the words of Garibaldi, is "kind of a lot." The real problem, though, is that stopping the subway car would rip a regular person's shoulder clean out of its socket even if the silk didn't snap. But remember: It's a superhero movie! Suspend disbelief! [Open Culture]