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Walter Munk's Astonishing Wave-Tracking Experiment
An anonymous reader writes in with a look at a scientist's interesting wave-tracking experiment and the incredible journeys that waves make. His name is Walter Munk, now in his 90s and a professor emeritus at the Scripps Institution of Oceanography in La Jolla, California. About 60 years ago, he was anchored off Guadalupe Island, on Mexico's west coast, watching swells come in, and using an equation that he and others had devised to plot a wave's trajectory backward in time, he plotted the probable origins of those swells. But the answer he got was so startling, so over-the-top improbable, that he thought, "No, there must be something wrong." His equations said that the swells hitting beaches In Mexico began some 9,000 miles away — somewhere in the southern reaches of the Indian Ocean, near Antarctica. "Could it be?" he wrote in an autobiographical sketch. Could a storm half way across the world produce a patch of moving water that traveled from near the South Pole, up past Australia, then past New Zealand, then across the vast expanse of the Pacific, arriving still intact – at a beach off Mexico? He decided to find out for himself. That is why, in 1957, Walter Munk designed a global, real life, wave-watching experiment.
What kind of non-story is that? One link points to some guy writing about how some other guys went to study waves at different locations. It doesn't say anything about how they did it, or has any technical information. The other link is a PDF scanned from a paper from 1982. Slow day when you have 32 year old news?
c++;
In a plane you are correct - they spread and dissipate.
The earth is not a plane - and the curvature will focus the wave after a certain distance is traveled.
After 1/4 of the Earth's circumference (6000 miles) the wavefront stops dissipating and starts converging.
Just simple geometry:
Imagine a planet completely covered with water. Now throw in a big stone at one of the poles:
This results in a circular wave expanding from the pole, parallel to the latitudes.
As soon as it crosses the equator, it starts converging again, until it arrives as a peak at the
opposite pole.
Distance from pole to equator: circumference/4.
This works with a stone drop at any other point on the globe as well, I just used poles and
equator because it's easier to imagine. In reality, land masses complicate things a bit of course.