Do You Know Your Tides?

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Sure, we all think we know how tides work, the gravitational pull of the moon and its cycle around the earth, how our home break works best on what tide and swell combination. But here’s something cool to know, there are more than 400 astronomical cycles that influence the tide.

A great new book called "Tides: The Science and Spirit of the Ocean," by author and surfer Jonathan White, goes into great depth about all the variables associated with tides, tidal bores and inland water ways. It wasn’t until he got stuck by a 14-foot tide in Alaska on a mud flat that he realized he didn’t know enough about tides, and that experience set him forth to investigate. "I thought I'd find my answer in a book or two," he writes, "but the more I read, the more complex and mysterious and poetic the subject became."

SurfersVillage.com released some great facts gathered from the book:

There is a very long wave that travels around the world at 450 miles per hour. It has no beginning and no end. The 12-hour gradual rise and fall we see on the beach is the wave’s passing, first its crest and then its trough.

There is about three terawatts of power in the ocean’s tides — three times the world’s daily energy consumption.

The world’s largest tidal bore – sometimes 25 feet tall – is on the Qiantang River in China. The Silver Dragon has been racing up the Qiantang on every tide, every day, for 2,500 years.

Tide charts repeat themselves every 18.6 years.

Tides create friction — lots of it — by rubbing against the ocean floor. Some of this is dissipated as heat, just like when you rub your hands together. But most of it is transferred into energy that acts as a brake on the earth’s rotation. By a very small amount per day, the earth is turning slower and the days are growing longer, because of the tide.

In the 13th century, Leonardo da Vinci believed the tides were caused by the breathing of a giant beast and tried to calculate the size of its lung.

The book that got Galileo in trouble with the Catholic Church was originally titled: The Flux and Reflux of the Sea. Galileo used the sloshing of the ocean tides as proof that the earth moved, and therefore was not the center of the universe. His tide theory, by the way, was completely wrong, but because of it, he was sentenced to house arrest until the end of his days.

One hundred and sixty billion cubic meters of water rush in and out of the Bay of Fundy, between the Canadian provinces of New Brunswick and Nova Scotia, during an average 12-hour tide cycle. That’s four times the outflow from all the world’s rivers in the same amount of time.

This might be a little far-fetched, but they also write: “When the waters of the Red Sea parted to allow Moses and the children of Israel to escape Egypt, it may have been a tidal event, timed perfectly by Moses, who lived near the Red Sea and knew that on an extreme spring tide, there would be a dry passage across. He may, in fact, have timed his exodus precisely so that the Children of Israel would make it across, but the tide would rush back in while Pharaoh and his pursuing army were only half way across. Pharaoh, who lived on the tideless Nile, would not have been familiar with the Red Sea tides.”

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