CLOSE
iStock
iStock

5 Surprising Things That Have Broken the Speed of Sound

iStock
iStock

by Kenny Hemphill

You might already know that in 1947, U.S. test pilot Chuck Yeager was the first person to break the sound barrier in a Bell X-1 named the Glamorous Glennis. But aircraft aren't the only things that break the sound barrier. Here are a few other items that may surprise you.

1. PEOPLE

When Felix Baumgartner jumped out of a balloon 24 miles above New Mexico in 2012, he broke more than the world record for the highest-ever freefall. About a third of the way down, Baumgartner reached Mach 1.25 or 843.6 mph, and in doing so became the first person to break the sound barrier while in freefall.

Having beaten a freefall record that had existed for 52 years, however, Baumgartner only held it for two years, when it was beaten again by Google exec Alan Eustace. He also broke the sound barrier, though he didn't hit as impressive a maximum speed as Baumgartner, reaching a measly 822 miles per hour, or Mach 1.23.

2. PING PONG BALLS

Anyone who's watched the top table tennis players in action knows they hit the ball hard and that it travels almost too quickly for the eye to see. But even that pales in comparison to the air-powered cannon built in 2013 by students at Indiana's Purdue University, which fired ping pong balls at more than 900 mph. “You can get really, really high accelerations, the ball comes out of the barrel intact and doesn’t break until it actually hits something,” mechanical engineer Mark French Inside Science. The cannon used a vacuum pump to suck the air from a sealed tube, the air rushed to a nozzle shaped like an hour glass, and the nozzle propelled the ping pong balls at supersonic speed—about 919 mph. Remarkably, given their light weight and poor aerodynamics, the ping pong balls delivered as much energy to their target as a brick falling several stories.

3. WHIPS

You know that crack a bullwhip makes when it's wielded in anger by an expert? That's a sonic boom, the shockwave created when the tip of the whip breaks the sound barrier. Or at least, that had been the presumption until researchers at the University of Arizona spoiled it for everyone.

They were puzzled as to why, if the crack is a sonic boom, it doesn't occur until the whip's tip is traveling at almost twice the speed of sound. It turns out that the cracking noise is actually created by a loop traveling along the whip, picking up speed. And when it reaches the speed of sound, it creates a sonic boom.

4. A TOWEL

Snapping a towel in the changing room is dangerous—you could, in all seriousness, take someone's eye out. The reason it's so dangerous has partly to do with the speed the end of the towel is traveling. Like a bullwhip, it goes very fast indeed.

In 1993, a group of students at North Carolina School of Science and Mathematics set out to prove that a properly whipped towel could break the sound barrier. They rigged up a high-speed photography kit that would allow them to measure the distance the tip of the towel was traveling at the moment they thought the barrier would be broken. After the experiment, it seemed like they had managed to break the barrier—but the students felt their results were inconclusive.

So they tweaked the experimental setup (and, according to some sources, swapped the towel for a cut down bedsheet) which eventually allowed them to break the sound barrier. But there was another caveat: The team cautioned that they still got snaps when it didn’t appear that they had broken the barrier. The theory was that their camera wasn’t fast enough to catch subsequent supersonic moments, but it remains a mystery.

5. AIR

Here's an odd one to finish with. According to one study, when a rock or other such object is dropped into water, an hourglass-shaped cavity of air is created, which then ejects the air at speeds faster than the speed of sound.

nextArticle.image_alt|e
iStock
arrow
science
7 Science-Approved Tips for Walking Across Ice
iStock
iStock

Unless you live in a warm climate year-round where the only ice you experience involves cubes that tumble from your refrigerator door, the issue of slipping on the slick surface presents a serious concern. After all, news segments talk of treacherous conditions where people unable to gain traction slide themselves into oblivion just crossing the street. On the work front, the Bureau of Labor Statistics reports that in 2014, ice, snow, or sleet caused more than 42,000 injuries and illnesses.

And of course, there will always be viral ice-slipping videos floating around, like the one of the man who slid along the entire length of his driveway.

The very act of walking is a balancing act we take for granted. "Walking is like falling and catching yourself over and over," says Kayla Lewis, Ph.D., an assistant professor of physics at New Jersey's Monmouth University. "You lean forward and fall forward, catching yourself with your leading leg to prepare for the next step. But it's the friction between the ground and your shoes that enables you to save yourself this way; it prevents your front shoe from sliding forward and your back shoe from sliding backward."

All of this begs the question: What's the best way to walk on ice to minimize the risk of falling? To safely sashay over ice, follow the experts' advice below. Don't let their words of wisdom, you know, slip away from you.

1. MOVE SLOWLY AND STEADILY.

Clearly, instinct and common sense kicks in the moment you approach the slick surface, telling us it's virtually impossible (and not really wise) to sprint across an ice-covered driveway. Slow and easy wins the proverbial race, right?

Yes. According to Philip E. Martin, Ph.D., professor and chair of the Department of Kinesiology at Iowa State University, minimizing forward and backward force is indeed essential when walking on ice. "What's key is trying to keep force applied to the ground more vertically so there's less force forward and backward—because that's the part that requires friction," he tells Mental Floss.

2. TAKE SHORTER STEPS.

What does reducing forward-and-backward force mean practically? Taking shorter steps. When we do so, the forces applied against the ground in forward and backwards directions are reduced. Therefore, Martin says, we're not pushing as hard and are "adapting our gait to work with the reduced friction that's available to us."

3. AVOID MELTING ICE.

Mark Fahnestock, a glaciologist and research professor at the University of Alaska Fairbanks, has been studying glaciers and ice sheets for the last couple of decades, and during that time has experienced conditions at -40°F in Alaska. He says that how slippery ice becomes can vary by temperatureso being aware of temperatures can help you figure out how easy or challenging it may be to cross ice. "It's easier to walk on ice at 0°F or -20°F," he tells Mental Floss. "Ice is much slipperier when it's really melting."

Chalk that up to a film of molecules on the surface that behaves like water, he says, which "becomes more pronounced" in warmer temperatures. However, this isn't to say you won't ever slip on ice the colder the temperature gets; he emphasizes, "It's not that it's not slippery, it's just that it's not as slippery as when it's warmer."

4. GO AROUND SLOPES AND STAIRS WHEN YOU CAN.

You should also be mindful of the surface you're about to set foot on. A flat surface is one thing, but Fahnestock says that "if it's slanted where your foot meets a driveway, for example, it's not holding your weight—rather, it's your weight that's causing your foot to move."

"Gravity is going to do its thing whether you like it or not," Martin says, especially if there's an icy slope that's in a significantly downhill direction. Unfortunately, in this circumstance, you probably won't be able to adapt your gait to prevent slipping, so it's likely it'll be a score of Ice 1, Human 0.

ice caution sign next to person who slipped on ice
iStock

Stairs can make navigating ice even more treacherous, but we know it's not always possible to avoid them. According to helpful hints for walking on ice from Iowa State University, when dealing with icy steps, be sure to use handrails, keeping your hands out of your pockets, and continue to move slowly.

5. KEEP AN EYE OUT FOR CHANGING SURFACES.

Then there are circumstances where the surface characteristics can change without us realizing it. But Martin says not to fret if you're walking on a straight, dry surface and suddenly encounter an icy patch you weren't expecting. Maximum friction force is reduced when you encounter this abrupt change, causing you to quickly alter your gait. Sure, you may slip a little since it initially throws you off guard, but "humans are pretty adaptable and recognize challenges quickly," Martin says. We pay closer attention to surface characteristics than we may consciously realize, and we adjust our stride patterns automatically.

6. WEAR THE RIGHT SHOES.

And don't forget the benefits of appropriate footwear. Martin encourages people to consider a shoe's material properties, noting that a rigid leather sole is far from ideal as it offers a significantly weaker grip compared to a rubber sole. Of course, traction-improving treads, cleats, or spikes can help too.

Scientists are studying how traction varies among consumer boots. A team of researchers at iDAPT, the research arm of the Toronto Rehabilitation Institute—University Health Network, has tested and rated the slip resistance of nearly 100 boots and spikes in their WinterLab, where they study slips and falls on a floor composed entirely of ice. Testers secured into safety harnesses walk back and forth across the ice as the researchers slowly increase the angle of the floor until the tester slips. The angle at which they slip is called the "maximum achievable angle": The higher the angle, the better the slip resistance.

More than 80 percent of the boots they've tested failed to score high enough on the MAA to earn a single "snowflake" on iDAPT's three-snowflake scale, including those from popular brands like Timberland, Sorel, and Terra. The top ranked, with three snowflakes, are all Stabil spikes, which attach to your regular shoes or boot.

7. WHEN ALL ELSE FAILS, WADDLE.

Consider taking an ice-walking cue from those waddling tuxedoed ice pros: Walk like a penguin. Fahnestock says shuffling helps keep your weight in a straight-down stance, allowing your feet to carry your weight carefully and minimize slipping.

nextArticle.image_alt|e
The North Face
arrow
Design
The North Face's New Geodesic Dome Tent Will Protect You in 60 mph Wind
The North Face
The North Face

You can find camping tents designed for easy set-up, large crowds, and sustainability, but when it comes to strength, there’s only so much abuse a foldable structure can take. Now, The North Face is pushing the limits of tent durability with a reimagined design. According to inhabitat, the Geodome 4 relies on its distinctive geodesic shape to survive wind gusts approaching hurricane strength.

Instead of the classic arching tent structure, the Geodome balloons outward like a globe. It owes its unique design to the five main poles and one equator pole that hold it in place. Packed up, the gear weighs just over 24 pounds, making it a practical option for car campers and four-season adventurers. When it’s erected, campers have floor space measuring roughly 7 feet by 7.5 feet, enough to sleep four people, and 6 feet and 9 inches of space from ground to ceiling if they want to stand. Hooks attached to the top create a system for gear storage.

While it works in mild conditions, the tent should really appeal to campers who like to trek through harsher weather. Geodesic domes are formed from interlocking triangles. A triangle’s fixed angles make it one of the strongest shapes in engineering, and when used in domes, triangles lend this strength to the overall structure. In the case of the tent, this means that the dome will maintain its form in winds reaching speeds of 60 mph. Meanwhile, the double-layered, water-resistant exterior keeps campers dry as they wait out the storm.

The Geodome 4 is set to sell for $1635 when it goes on sale in Japan this March. In the meantime, outdoorsy types in the U.S. will just have to wait until the innovative product expands to international markets.

[h/t inhabitat]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios