Al Osborne doesn't have much of an accent anymore, but there's still a bit of the Texas drawl left over from his youth in College Station. And even a few decades in Italy hasn't erased the easy-going attitude and low-key charm that are the hallmarks of a Texas gentleman. When Osborne talks about physics, he tends to drop in an Italian word here or there, along with American colloquialisms like "loaded for bear" when he means "prepared for anything." It's a style that can make Osborne's explanation of the non-linear Schrodinger equation sound more like a cosmopolitan folktale.
Osborne is a leading researcher studying nonlinear dynamics in water - from monster waves, to tidal bores, to unusual ocean currents. His status in the field stems in part from his groundbreaking discovery of enormous, subsurface ocean waves, which turned out to be the largest solitons ever found. "The evidence for the solitons was there all along in a number of satellite observations,"says Osborne, "but nobody understood them until the proper in situ measurements were made." It was a career-changing event for the physicist who started out studying cosmic rays.
Converging Oceaniac Internal Waves, Somalia, Africa
(Nasa Image eXchange)
A soliton is an example of a wave in nonlinear physics. Small waves in many media add linearly - that is, a one meter wave passing through another one meter wave will combine to briefly form a two meter peak. When waves grow large, they no longer add linearly, and the resulting height can be substantially different than the sum of the component waves. Solitons are special solutions of nonlinear wave equations. These robust structures behave more like particles than waves, traveling long distances and scattering off other solitons and waves.
Osborne explains that his own breakthrough echoes the original discovery of solitons by a young naval architect who happened to be riding his horse along Edinburgh's Union Canal in August 1834. John Scott Russell had set out to learn why the water was perpetually draining from the canal when he noticed an odd wave produced at the bow of a barge as it came to a halt. Unlike the waves Russell had studied in school, a single hump of water traveled along the canal "without change of form or diminution of speed." Russell's waves, which were the first solitons ever described, continued to the end of the canal, where they jumped the final containing wall and dumped some of the water out. The discovery simultaneously solved Russell's canal-draining mystery and presaged the modern study of nonlinear physics.
As was the case for Russell, luck and insight were key to Osborne's discovery of ocean solitons. While living in Houston in 1962, Osborne was eager to aid the nation in the space race, and offered his talents to NASA engineers in Houston. He worked on the Apollo program part-time while attending graduate school at the University of Houston. Despite completing a PhD dissertation on cosmic ray physics, Osborne was lured away from aerospace by the oil industry, where he concentrated on oceanographic research for Exxon Production Research Co.
Osborne and oceanographer Terrence Burch discovered oceanic solitons while investigating mysterious currents that were battering an oil drilling vessel off the coast of Sumatra. They studied ocean images taken from the 1975 Apollo-Soyuz space station, which revealed striations over one hundred miles long in the waters surrounding the vessel. Osborne and Burch deployed sensors in the water and discovered subsurface waves of warm water extending a hundred meters down, propagating along the "thermocline" between layers of cooler and warmer water. The waves' temperature profiles resembled the surface profile of Russell's wave. They also maintained their shape and speed over long distances, just as the traveling hump of water had in the Edinburgh canal. Indeed, the waves were simply enormous solitons.
Osborne's seminal paper on oceanic solitons was significant enough to be assigned to the cover of Science magazine. It also inspired Osborne's passion for nonlinear physics, and garnered him a guest spot on the Tonight Show with Johnny Carson. Although Osborne says that so much success and notoriety so early in his career was a generally positive experience, he admits that his subsequent choice to join the faculty of an Italian university was in part a reaction to the excitement that followed his soliton discovery. "I felt like I needed the change to regroup," says Osborne.
These days, Osborne divides his time between the University of Torino (in the Italian city that is home to the Shroud of Turin) and the Office of Naval Research in Arlington, Virginia. Although he studies a range of nonlinear phenomena, much of his work concentrates on surface ocean waves known as rogues that would give a brave sailor nightmares. Rogue waves are surface manifestations similar to solitons that tower over normal waves by a factor of two or more. Occasionally, rogues may be taller than a ten-story office building, or cause equally impressive troughs in the ocean that can swallow a ship. The faces of rogues are steeper than normal waves, leading to walls of water that can split open tankers, blow out bulkheads, or rip the bridge clean off of a ship's decks.
Fortunately for sailors, such enormous rogues are rare. Nevertheless, Osborne has found that significant rogue waves are much more common than was once thought. Marine engineers often design structures to withstand the largest wave likely to come along in a hundred years. "Our measurements show that oil drilling platforms are sometimes experiencing these 'hundred-year waves' several times each year," says Osborne, suggesting that true hundred-year waves must be much larger than anyone expected.
A possible reason for the discrepancy in wave height predictions is the mathematical difficulty of nonlinear computations. Physicists often make their calculations simpler by throwing out everything but the linear terms in their equations, and leaving the nonlinear mathematics to computer simulations. Osborne believes that he has better ways to deal with nonlinear terms, allowing him to keep them in his equations. He says that his techniques provide enhanced insight into a range of nonlinear phenomena, including solitons. And when he explains his ideas in that faded Texas drawl peppered with the occasional Italian, the math doesn't seem so bad - at least until he sketches something on a napkin that looks almost like, but isn't exactly, a phase-space diagram. Clearly, Osborne's work is no mere cosmopolitan folktale.