How Are These Crisscrossing Waves Even Possible?

Illustration for article titled How Are These Crisscrossing Waves Even Possible?

This remarkable image was captured just off the western point of France's Isle of Rhé. It's a beautiful demonstration of a natural phenomenon known as a cross sea — one that can be explained by a little bit of physics and math.

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A cross sea is a marine state with two wave systems traveling at oblique angels. It happens when water waves from one weather system continues despite a shift in the wind. Waves that are produced by the newer system run at an angle to the old. This creates a shifting, dangerous pattern. Indeed, until the older waves dissipate, cross seas are a hazard for boaters and swimmers.

It's an example of the Kadomtsev–Petviashvili (or KP equation) equation at work. It looks a little something like this:

Illustration for article titled How Are These Crisscrossing Waves Even Possible?
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Named after Boris Borisovich Kadomtsev and Vladimir Iosifovich Petviashvili, it's a partial differential equation that describes nonlinear wave motion. The equation can be applied to physics as a way to model water waves of long wavelengths that have particular qualities — like those produced by interacting weather systems.

[h/t @SciencePorn]

Image: Michel Griffon/Wikimedia Commons.

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DISCUSSION

It's what happens when you cross the streams.