They are about as far apart as two things in science can be: a type of ocean wave that helps drive the El Niño climate cycle, and quantum materials that, thanks to a particularly strange bit of physics, have insulating interiors and conduct current along their surface. Yet, in a remarkable case of lateral thinking, the two disparate phenomena can be explained with the same topological mathematics of shapes with holes in them, a team of physicists reports.
“I’ve been trying to make the case that these two fields really are very closely connected,” says Brad Marston, a physicist at Brown University who led the study. In addition to explaining why ocean and atmospheric waves can become trapped at the equator, the study also suggests that condensed matter physics—the study of liquids and solids, such as the semiconductors that make up computer chips—and earth science could cross-pollinate in other ways, such as using topology to explain waves on other planets and moons, or in astrophysical disks of gas and dust.
Marston and his colleagues applied condensed-matter theory to two types of waves, known as Kelvin and Yanai waves, that can propagate through the seas and air near Earth’s equator. Both are undulations with wavelengths hundreds or thousands of kilometers long that carry energy eastward along the equator, contributing to El Niño, tropical storm systems, and other weather patterns. They result from the interplay of two physical processes. First, gravity competes with buoyancy, causing colder air or water to sink and warmer air or water to rise and making the blobs of air or seawater independently bob up and down. Second, Earth’s rotation to the east creates the so-called Coriolis effect, which makes fluids moving over Earth’s surface veer in opposite directions depending on the hemisphere.