Pylimitics

A “soliton” is a special kind of wave. While it appears here and there in publications devoted to quantum physics — because it has to do with quantum or quasiparticle propagation — the word also has to do with other kinds of waves, even the traditional kind you see at the beach. “Soliton” is derived from “solitary,” and that’s what a soliton is; a solitary wave. In an interesting turnabout, it was first used in relation to quantum particles (which, you’ll remember, are also waves), and only later was it applied to waves we can actually see.

There are stories at sea about “rogue waves” that are much larger than others and sometimes even travel in a different direction. Innumerable shipwreck stories rely on those waves as plot devices. But there’s another venue for solitons: rivers and other estuaries . An estuary is any passage the ocean tide follows into land — and the tidal part is important here. Sometimes as a result of a high tide, a single large wave can flow up a river. Rivers typically get narrower and shallower the farther from the ocean they get, and because of the way waves work, the soliton wave keeps its shape and speed while increasing in height. 

This phenomenon has been going on for millennia, but the word “soliton” only dates back to the 1960s when Zabusky and Kruskal used it in Physical Review. You might expect there are some other words for it. And you’d be right! The English word “eagre” is one of them. 

“Eagre” has become pretty rare unless you live in close vicinity to one of the rivers in England known for these waves. This would include the Ouse, the Trent, and the Severn. These are places where an “eagre” is also known as an “aegir,” “hygre,” “higre,” “agar,” and “aigre.” The word dates back to Old English, and it’s been mentioned here and there in English novels, including the 1860 The Mill on the Floss by George Eliot: “Above all, the great Floss, along which they wandered with a sense of travel, to see the rushing spring-tide, the awful Eagre, come up like a hungry monster.”

Bret Harte’s A Protegee of Jack Hamlin’s in 1894 mentions it too: “The steamer Silveropolis was sharply and steadily cleaving the broad, placid shallows of the Sacramento River. A large wave like an eagre, diverging from its bow, was extending to either bank, swamping the tules and threatening to submerge the lower levees.” (“Tules” are rushes.)

The word “eagre” is so old nobody knows where it came from or how it’s derived. One theory was that it was a variation of “Oegir,” the god of the sea in some Scandinavian cultures. However, once it was settled that this was a theory that came from the novel Acadia, written in 1884 by Eliza Chase, everybody changed their minds. There are certainly people around who might still believe it, though, just like some people in real life search for “vril,” a fictional substance used by fictional people to do fictional things. It probably takes a lot of energy to convince yourself about things like that. You’d have to be an eagre beavre.