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Myth, busted: Apatosaurus didn’t produce sonic booms when whipping its tail

Former Microsoft CTO Nathan Myhrvold did first computer simulations in late 1990s.



No sonic boom: Scientists created a computer simulation showing the tail movement of Apatosaurus. Credit: Simone Conti.

Back in 1997, Microsoft’s then-CTO, Nathan P. Myhrvoldmade headlines when his computer simulations suggested that the enormous tails of sauropods—specifically Apatosaurus—could crack like a bullwhip and break the sound barrier, producing a sonic boom. Paleontologists deemed it an intriguing possibility, although several were skeptical. Now a fresh team of scientists has tackled the issue and built its own simulated model of an Apatosaurus tail. They found no evidence of a sonic boom, according to a new paper published in the journal Scientific Reports. In fact, the maximum speed possible in the new simulations was 10 times slower than the speed of sound in standard air.

While still at Microsoft in the 1990s, Myhrvold—a longtime dinosaur enthusiast—stumbled upon a book by zoologist Robert McNeill Alexander speculating about whether the tails of certain sauropods may have been used like a bullwhip to produce a loud noise as a defensive strategy, a mating call, or other purpose. The structure somewhat resembles a bullwhip, in that each successive vertebra in the tail is roughly 6 percent smaller than its predecessor. It was already well-known in physics circles that the crack of a whip is due to a shock wave, or sonic boom, arising from the speed of the thin tip breaking through the sound barrier.

Myhrvold wanted to put that speculative suggestion to the test, and struck up an email correspondence with paleontologist Philip J. Currie, now at the University of Alberta in Edmonton, Canada. (Fun fact: Currie was one of the inspirations for the Alan Grant character in Jurassic Park.) The two men analyzed fossils, developed computer models, and conducted several computer simulations to test the biomechanics of the sauropod’s tail. They also compared those simulations to the mechanics of whips.

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