The Strangest, Most Spectacular Bridge Collapse (And How We Got It Wrong)

At a glance of the edited footage, it’s tempting to think that Gertie was brought down by resonance, given the vivid visual evidence of a bridge that undulates before it collapses, not unlike the wine glass that shatters under the vibrations of a singer’s voice…. How did the incorrect explanation persist for so long? In their paper about the event, Bilah and Scanlan cite 30 sources that mention resonance as a cause of the bridge’s failure. Ultimately, they point their fingers at a mix of rough, semi-empirical guess work and the “telephone” effect. “The primary reason for all this, we believe, is that many post facto accounts or investigations were speculative or reviews of still other accounts,” they write. | It’s easy to see why: the math and physics involved can seem complicated. And the unforgettable image—a bridge undergoing large periodic motion as an external force applies energy to it until it collapses—is, to physics teachers and textbook writers, an irresistible scientific example, an eye-popping way to wake up the kids at the back of the classroom. | “While it is understandable how so many textbooks have, over the years, oversimplified the physics involved,” wrote Bilah and Scanlan, “it is probably time… to offer the next generation of students subtler, more complex and correct explanations.” That was in 1991. —Motherboard