Published on January 30th, 2014 | by msalt

Human Waves

Waves are a classic natural phenomenon; why else would you thrown a rock in the water?

That makes it all the more amazing when people can recreate them, regaining that natural flow through effort and practice. No wonder then that the army of Thailand, a Buddhist country and the only Asian nation that was never colonized by a Western power, is the one that pulled off this amazing video. (The fun begins about 17 seconds in.)

Humans show waves in unplanned, spontaneous behavior too; cocktail party conversation, or even the push and pull of a relationship. One of the best examples is the traffic jam. Once someone explains to you that people reacting to the brake lights in front of them collectively form wave patterns without anyone thinking about it, you can feel it in slowdowns quite easily.

You’re flying along, then people brake suddenly. Then you drive fast again, not as long, and the next slowdown is a bit more gradual. The pulses even out until you either keep moving steadily, or hit a dead stop jam. Time lapse video of traffic makes this quite clear.

Chris Barrett, a pioneering scientist in this practical field of study, said “Traffic is particles with motive. I think it’s cool as hell.” More recent research has extended the metaphor into phases: fast-flowing traffic moves freely like a gas, congestion coalesces it into a liquid, and an absolute jam solidifies like ice.

Scientists at MIT, McGill and Temple found a slightly different metaphor. They see traffic as resembling “detonation waves produced by explosions” and invented a unit of traffic jam that they call the “jamiton.” Mathematicians at the Unversities of Exeter, Bristol and Budapest describe it as a ‘backward traveling wave’ that can move several miles upstream in a few minutes.

Foot traffic, Fisherman's Wharf

I used to live next to Ghiradelli Square in San Francisco, a place at the end of Fisherman’s Wharf that has tremendous amounts of foot traffic (and makes a lot of money for the shops there.) What puzzled me is that there are shops just outside the square that are dying from lack of business. A convenience store, pizza place, that kind of thing. Stores that have no equivalent inside of Ghiradelli Square.

You would think that they would make a lot of money just from spillover traffic. If only 5% of of people who visited this tourist attraction wanted some earthier food or bandaids or a 5-hour energy shot, there should be plenty of business to keep their shop owners in the pink.

It was only after several years of living there that I realized why. Humans flowing spontaneously behave like a fluid, with waves, whirlpools — and eddies. And that was problem. If you have ever river rafted or fished or spent much time at any river, you have noticed the eddies — the little pieces of water outside of the main current, where swirling water can do some very odd things.

I have seen the fluid pressure cause sections of a river to run back upstream, to form whirlpools, to undercut riverbanks, even to stack up in the air higher than the rest of the river.

One time my brother and I ran a rapid on the Deschutes River called Rattlesnake Falls that we had no business chancing, a class 4 rapid we braved in two tiny rubber duckies (a four-man and a six-man). I remember doing a half-assed job of scouting the river, not even getting out of the water but just standing on the frame.

Rattlesnake Rapid, Deschutes River

“Is that Rattlesnake Falls?” “Can’t be, I don’t even see any whitewater.” The reason we couldn’t see the whitewater is that the river dropped so suddenly that it was out of our view from that low angle. We moved ahead, and quickly realized our mistake. Giant waves and boulders were all around us. We moved nimbly, dodging obvious dangers, and with great luck made our way through.

But as if to remind us of how lucky we were, at one point we hit a mid-river eddy, something I’d never seen before (and haven’t seen since.) The counter-flow sucked us back up river 8 feet in an instant, casually like a giant vaguely waving at a fly, just to remind us how much power we were blundering past.

What I recognized at Ghiradelli Square was a human eddy, the massive flow of foot traffic into the square creating a counter-pressure just outside, leaving those poor shop owners on the wrong side of a strong current. That current was just as powerful as the one that filled the Crabcakes Lounge’s coffers. It illustrated just how important it is to feel and understand the flow before you put your boat in the water.

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About the Author

Mark Saltveit is a writer, standup comedian, skimboarder and dad based in Portland, Oregon. He is also the reigning World Palindrome Champion.



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