Photo courtesy of Randy Stancik
Photo courtesy of Randy Stancik

Stepping Out onto Chicago's 1300-Foot-High Glass Ledge

Photo courtesy of Randy Stancik
Photo courtesy of Randy Stancik

The first step out of Chicago’s Willis Tower Skydeck and onto The Ledge is a doozy, even if you’re not afraid of heights. That's because the boxes extend 4.3 feet from the skyscraper’s facade, 103 floors—that’s 1353 feet, or 6960 deep dish pizzas—above Wacker Drive. And did I mention they're made of glass? Incredibly clear glass, offering unobstructed views up, out, and down … if you can muster up the nerve to look at your feet, which can even be hard for Ledge veterans to do. "I’ve been on this a thousand times, and my damn knees buckle every time I’m out there," Randy Stancik, general manager of the Willis Tower, tells mental_floss. "It is not a natural feeling."


Skydeck has been around since 1974, just a year after the Willis (which was known as the Sears Tower until 2009) opened its doors. But by the 2000s, tourism to the Skydeck had leveled off; about a million people were visiting each year. Stancik was hired from Chicago’s John Hancock tower to revitalize the Skydeck in an $8 million renovation that included revamping a downstairs section into an interactive area that features Chicago history, architecture, sports, music, and pop culture.

Stancik and the architects at Skidmore, Owings & Merrill (who also designed the tower) explored a number of ideas for Skydeck, including having some screened-in areas that would create wind gusts naturally. “I was telling the engineer what I really wanted to do was get people right to the windows,” he says. He was inspired by the scene in Ferris Bueller’s Day Off where the titular character and his friends stood in the Skydeck, foreheads pressed to the glass, trying to catch a glimpse of what was below them. “The architects said, ‘What if we build a glass walkout?’”

Stancik didn’t need convincing, but he did wonder if it could be done. “The truth is, [people] build so much with architectural glass that it was time to do it,” he says. There were engineering challenges beyond just building an enclosed glass box strong enough for people to walk on, though—the boxes would need to retract in order for the building’s windows to be cleaned. “We were going to have rigs that went around them,” he says, “but it defeated the purpose if you have something going underneath it.”

Engineering the four glass balconies—10 feet tall, 10 feet wide, and 4.3 feet deep—took a year. They’re each constructed of three pieces of laminated, low-iron glass, each half an inch thick, weighing a total of 1500 pounds, with structural interlayers of DuPont SentryGlas, each 0.060 inches thick, in between; the interlayers are five times tougher and 100 times stiffer than traditional interlayers. A top protective layer protects the glass from getting scratched and is replaced every 6 to 9 months. Each box hangs from a nearly-invisible steel frame. “The Ledge can hold more human weight than we could ever put on it—5 tons,” Stancik says. The glass and steel balconies were designed by Halcrow Yolles and installed by Chicago-based MTH Industries. And yes, they retract: Creating the motors to pull them flush and then into the building on rails took two months alone.


The Ledge opened in July 2009; these days, between 1.5 and 1.6 million people visit each year. When the weather cooperates, visitors to the Skydeck can see 50 miles, including Chicago landmarks like the Field Museum, the Shedd Aquarium, and Millennium Park, 17 miles of uninterrupted park land, and the Metropolitan Correctional Center, Chicago, where inmates play volleyball during their exercise time. (Last year, two inmates escaped from that prison using bedsheets they had tied together.) In the distance, the shores of Michigan and Indiana are also visible. And that's all before they even step out onto The Ledge on the Tower's west side.

"Not everybody can come into a skyscraper, let alone the second tallest one in the U.S.," Stancik says. (The 1450-foot, 110-story building was dethroned just this year by New York City’s One World Trade Center.) "We never take the views for granted. It’s a great place to start your trip to Chicago, to get your bearings."


It’s a cold, wet day in mid-September when my friend and I visit the Willis Tower. From the street, the balconies that comprise The Ledge are just specks—you can hardly see them. After an ear-popping elevator ride, we find ourselves on the 103rd floor. Earlier, cloud cover had obstructed the view, but the foggy weather has dissipated by the time we get there, and it’s easy to tell, even from my spot inside the building, that you can see all the way down to the street.

Erin McCarthy

Even though I know, logically, that The Ledge can support 5 tons, it’s hard for me to think about walking out there, because I’m afraid of heights. I try not to let that fear stop me from having cool experiences, though, and I am currently cursing myself for that attitude. “Oh god,” I mutter, as I watch Stancik walk onto The Ledge, expecting me to follow him. “Oh god, oh god, oh god.”

“You have to walk out of a perfectly fine skyscraper and trust that we knew what we were doing,” Stancik says. “We really wanted people to think about taking that step or two.”

Believe me, I’m thinking about it. What’s comforting—if you can call it that—is that The Ledge is designed to be an experience I can control: It’s two steps on and two steps off. I can take my time going out, and come back in as quickly as I want. “If somebody’s here against their will, they don’t have to go out there,” Stancik had told me earlier. “We don’t want to force anybody. Lots of people—you’ll see it—they step out, smile for the camera and get out of there. They don’t look down.”

There is an area for people who don’t want to walk out on The Ledge, but I’m determined not to use it—and determined to look down, fear of heights be damned. So, with a death grip on the table where The Ledge’s official photographer is set up, I slowly inch out onto the glass.

Apparently, I’m not going fast enough. “I kind of want to push her!” my friend jokes.

“Oh, no,” Stancik says. “Don’t do that.”

Now, finally, out on the glass, my hands off the photographer’s table, I take a deep breath and look down. From 1300 feet, the taxis look like Matchbox cars, the river a thin ribbon weaving through the city. Even the tops of other skyscrapers seem far away.

It’s dizzying. My knees are shaking, my stomach in knots, but there’s no denying that this is awesome. I take a photo and send it to my mom—who is also afraid of heights—with the message, "1300 feet up on a glass ledge!" "CRAZY !!!!!!!!!" she responds.

Erin McCarthy

In the other boxes, visitors seem more at ease than I am: A woman does a headstand, and a guy plops down in a corner to take a selfie. Meanwhile, it’s all I can do to get into the right spot for the Tower’s photographer to take a picture. “Take a big step back!” he tells me and my friend. I take a small one. “One more…” he urges. Finally, we’re in the right position; he snaps a photo.

Afterward, I step off the glass, back into the safety of the skyscraper, and announce "I did it!" to no one in particular. Stancik is smiling. He sees this kind of thing every day.

All images courtesy of Randy Stancik/Willis Tower unless otherwise noted.

What Happens When You Flush an Airplane Toilet?

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.

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Popcorn Might Be the Cheap, Biodegradable Robot Power Source of the Future

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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