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Here's How Engineers Plan to Stop the Flow of Niagara Falls

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Getty Images

When you want to stop Niagara Falls from flowing, install a cofferdam. The New York State Parks Commission is hoping to do just that as early as 2019.

At a public meeting yesterday, the commission discussed details of a proposal to build two new bridges to replace the existing structures, which date to the turn of the 20th century. The current bridges, which stretch from the mainland to Green Island and from Green Island to Goat Island, are in bad shape: They were temporarily closed in 2004 so that trusses could be installed to stabilize them and allow access to Goat Island, but pieces continue to fall into the water below.

The parks commission determined in 2015 that rehabilitation of the bridges wouldn’t be possible—both the initial construction methods (reinforced concrete with earth-filled arches) and extensive deterioration meant new bridges would be necessary. And to build new bridges, they’d have to dry up the American side of the Niagara River, which sends as much as 150,000 gallons of water per second over the American and Bridal Veil Falls.

To accomplish the dewatering, a temporary cofferdam would be installed, probably at the upstream end of Goat Island. It would stretch from the island—which sits at the edge of the falls and divides the American side from Canada’s Horseshoe Falls—over to the mainland and divert flow from the river entirely to the Canadian side. (Only 15 percent of the falls flow to the American side; 85 percent gushes toward Canada.) 

Once the area is dry, the project could proceed in one of two ways. In the first, the Falls would be water-less from August to December. During that time, the existing structures would be demolished and workers would install piers, according to ABC News Buffalo; water flow would begin again at the end of December, and the next year, workers would resume construction on the bridges. The process would be completed in two years. The second option, which would last a year, would require a nine-month dewatering starting in April and round-the-clock construction.

The commission has been looking at rehabilitating or replacing the bridges since 2009, but the project doesn’t yet have funding and isn’t approved. It estimates that construction costs will range from $21.37 million to $37.32 million, depending on the design chosen, and notes that the state parks department "will need to secure special capital funding from state and/or federal sources prior to advancing this project to the construction phase."

If it does move forward, the work will begin in 2019. It will be the second time the American side of the falls has stopped flowing thanks to humans: In 1969, the U.S. Army Corps of Engineers diverted the flow of the river to the Canadian side using a 600-foot cofferdam constructed of 27,800 tons of rock. The goal? To study the accumulation of boulders and rock from rock slides at the bottom of the falls. The dried-up falls drew many tourists, and after six months of investigation, a decision was made to leave the falls as they were. The cofferdam was removed in November of that year.

You can read the full PDF report of the proposal here.

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What Happens When You Flush an Airplane Toilet?
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For millions of people, summer means an opportunity to hop on a plane and experience new and exciting sights, cultures, and food. It also means getting packed into a giant commercial aircraft and then wondering if you can make it to your next layover without submitting to the anxiety of using the onboard bathroom.

Roughly the size of an apartment pantry, these narrow facilities barely accommodate your outstretched knees; turbulence can make expelling waste a harrowing nightmare. Once you’ve successfully managed to complete the task and flush, what happens next?

Unlike our home toilets, planes can’t rely on water tanks to create passive suction to draw waste from the bowl. In addition to the expense of hauling hundreds of gallons of water, it’s impractical to leave standing water in an environment that shakes its contents like a snow globe. Originally, planes used an electronic pump system that moved waste along with a deodorizing liquid called Anotec. That method worked, but carrying the Anotec was undesirable for the same reasons as storing water: It raised fuel costs and added weight to the aircraft that could have been allocated for passengers. (Not surprisingly, airlines prefer to transport paying customers over blobs of poop.)

Beginning in the 1980s, planes used a pneumatic vacuum to suck liquids and solids down and away from the fixture. Once you hit the flush button, a valve at the bottom of the toilet opens, allowing the vacuum to siphon the contents out. (A nonstick coating similar to Teflon reduces the odds of any residue.) It travels to a storage tank near the back of the plane at high speeds, ready for ground crews to drain it once the airplane lands. The tank is then flushed out using a disinfectant.

If you’re also curious about timing your bathroom visit to avoid people waiting in line while you void, flight attendants say the best time to go is right after the captain turns off the seat belt sign and before drink service begins.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Popcorn Might Be the Cheap, Biodegradable Robot Power Source of the Future
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If you've ever put a flat bag of kernels into the microwave and pulled out a full bag of fluffy popcorn two minutes later, you've witnessed a fascinating bit of food chemistry at work. Now, IEEE Spectrum reports that scientists are looking into applying the unique properties of popcorn to robotics.

For their study, presented at this year's IEEE International Conference on Robotics and Automation, Cornell scientists stuffed the movable parts of a robot (a.k.a. the actuators) with unpopped kernels of corn. Usually actuators are powered by air, hydraulics, or electric currents, but as the researchers found, popcorn works as a cheap single-use alternative.

When heat is applied to popcorn kernels, the water trapped inside them turns to steam, creating enough pressure to peel back the tough exterior and release the starchy endosperm. A sudden drop in pressure causes the endosperm to quickly expand, while the cool outside air solidifies it.

The results can be dramatic: When popping extra small white kernels, the cheapest popcorn tested, researchers saw them expand to 15.7 times their original size. Inside a soft robot, this amounts to building interior pressure that moves the actuator one way or another.

A similar effect can be achieved using air, and unlike popcorn, air can be pumped more than once. But popcorn does offer some big advantages: Using popcorn and heat is cheaper than building air pumps, plus popcorn is biodegradable. For that reason, the researchers present it as an option for robots that are designed to be used once and decompose in the environments they're left in.

You can get an idea of how a popcorn-powered robot works in the video below.

[h/t IEEE Spectrum]

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