Latest StoriesPhysics
    University of Rochester's Optical "Cloaking"

    "Researchers at the University of Rochester Create a Three-dimensional,Transmitting, Continuously Multidirectional Cloaking Device Inspired perhaps by Harry Potter's invisibility cloak, scientists have recently developed several ways-some simple and some involving new technologies-to hide objects from view." I know the Rochester researchers and most of media are calling this "cloaking", but this clever optical trick is far from the invisibility cloak of science fiction and fantasy. The simplest version of this setup uses four off-the-shelf lenses to focus light around objects placed between them, but only for a specific region (eg. in a ring around the edge of the lens, but not at the center). And while the demonstrations in this video show a small lens system being used, it apparently can be scaled up as larger lenses are used. Neat stuff. Research paper here.

    In Brief: Death Valley's Sailing Stones Mystery Solved

    The mystery of Death Valley's famous moving stones has finally been solved. For almost a century, geologists have been puzzled by the movement of stoves along a dry lake bed called Racetrack Playa in the California desert. The moving stones, which weigh up to 700 pounds, travelled up to 3000 feet in their journey, seemingly without any human or animal assistance. To study their movements, geologists in 2011 tagged 15 rocks with GPS loggers and time-lapse cameras, and even buried magnetic triggers beneath some to test popular theories. They found the perfect combination of light wind and layer of thin ice on the lake bed was the cause of the movement. In the video below, Scripps Oceanography paleooceanographer Richard Norris describes the discovery.

    In Brief: Physicists Make a Tractor Beam in Water

    Have you ever sat in the bathtub or swimming pool and made waves on the surface of the water with your hands to push or pull away a rubber duck? That's the basic idea behind what Australian physicists have been experimenting with in what popular media is calling "tractor beams" in water. Researchers at the Australian National University released a paper in Nature Physics describing how precise generation and manipulation of surface flows in a pool of water can force small objects to move against the direction of the resulting waves--returning to the source of the water disturbance. Computer models and tank experiments show how complicated and precise the movements have to be to get a desired result, but the researchers are hopeful that their discovery could be applicable for real-world tasks like collecting oil spills.

    MIT's Gravity-Defying "Magnetic Hair"

    "MIT engineers have fabricated a new elastic material coated with microscopic, hairlike structures that tilt in response to a magnetic field. Depending on the field's orientation, the microhairs can tilt to form a path through which fluid can flow; the material can even direct water upward, against gravity." More information here.

    OverDrive: The Flying Car on Kickstarter

    Over the years, I’ve learned to expect the unexpected from my friend and former NASA colleague, Fitz Walker. I’ve long been aware of his engineering and fabrication talents from projects that I have collaborated with him. Fitz has a secretive side too. The true depth and breadth of his skills always seem to be revealed through random, casual conversations: “That thing? Oh, that’s my RC submarine…I’ve been building them for years.” “What? I didn’t tell you that I built an electric motorcycle?”

    Fitz’s most recent bomb was borderline atomic. He confided that he has spent years working with a team to create an honest-to-goodness flying car--which many consider to be the holy grail of engineering challenges! I was able to get him to divulge a few details, and later met with the project’s originator and driving force, Mitchell LaBiche. I caught Mitch just as he was preparing to launch a Kickstarter campaign for his project. He provided deep insight into his design as well as the regimented approach that he has taken to avoid the pitfalls that foiled so many other flying car entrepreneurs.

    The LaBiche Automotive OverDrive is a flying car project that looks more like an Italian supercar than airplane. Attractiveness was one of the development team’s primary design requirements.

    Tested: You call your flying car design “OverDrive”. How did the concept develop?

    LaBiche: During my early years of flying, I became stranded or delayed at a few destinations on multiple occasions. One such event was when I became stranded at an airport for three days and could not take off. However, just 50 miles away, the weather was clear. If I could have moved my plane down the road to the clear weather, it would have turned my disastrous weekend into a mere inconvenience. That event got me to start thinking of a better way to own, use, and integrate civil aviation/personal aircraft into everyday life.

    During that time, I was employed as an engineer working on the Apache helicopter program and had envisioned that what I (and others) wanted was some sort of vertical takeoff, personal air vehicle. The plan changed when I took a friend’s suggestion to ask a few people what they wanted…and possibly turn my personal project into a money making venture. I invested three years and lots of money in marketing questionnaires which produced over 3,000 data points. From that, I found that what most people actually wanted was a not a vertical takeoff machine, but a personal travel vehicle that could both fly fast and go down the road. That changed everything.

    OverDrive's proposed conversion from car to plane. (Click to play)

    The original R&D project (named the FSC-1, for Flying Sports Car #1 under the LaBiche Aerospace banner) was started to see if a marketable flying car could be designed and built. After nearly 20 years of continuous, low-level development, it was deemed ready to move on to the next phase as a real product in 2012. A new sister company was formed (LaBiche Automotive) and the FSC-1 became “OverDrive” to sell the vehicle under a new name indicative of a product for the advanced automotive market.

    Engineering Fires in The Fire Lab

    From The Atlantic: "Massive wildfires cost billions of dollars and burn millions of acres in the U.S. every year, but we know surprisingly little about the basic science of how they spread. At the Fire Lab in Missoula, Montana, researchers reverse-engineer spreading fires using wind tunnels, fire-whirl generators, and giant combustion chambers. They're finding that fire is a mysterious phenomenon, and the physics behind it is often counter-intuitive." We previously wrote about the study of fire in our profile of combustion engineer Ruddy Mell for our series on awesome field scientists.

    Maker Faire 2014: How Quantum Levitation Works

    At Maker Faire 2014, we met Dylan Dixon, an 8th grade student who built a system to demonstrate quantum levitation for a school project. We chat with him to learn about how quantum levitation works with the manipulation of magnetic fields.

    Regenerating Plastic Grows Back After Damage

    "Professor Scott White discusses the research breakthrough that allows [damaged] plastic to not only heal, but truly regenerate. Self-healing materials have been around for about a decade. But they have never been able to heal damage much larger than the width of a human hair. Now, White and his colleagues Jeff Moore and Nancy Sottos have developed plastic that can regenerate damage as large as a bullet hole. The plastic regenerates when two chemical channels in the material mix at a damaged area. This reaction forms a gel which fills in the hole and eventually hardens, similar to blood clotting in a wound."

    How Scientists Visualize Sound with a Photography Trick

    You can actually see sound waves as they travel through the air thanks to a clever photographic trick. NPR's Adam Cole, who runs the the Skunkbear science Tumblr, produced this video explaining how scientists use a technique called Schlieren Flow Visualization--the combining of two mirrors, a barrier, and a high-speed camera--to visualize the effect of sound waves through space. It's the same technique used to visualize other "invisible" processes, like the turbulence around an airplane wing or rising heat from a hot surface.

    Tested Explains: What The Heck is Inflation Theory?

    If you were conscious on Monday you probably heard there was big news out of the physics community. So big, in fact, that there’s already talk of Nobel prizes and jokes about Einstein patting himself on the back for being proven right...again. Let’s be honest though, big physics news is always kind of hard to understand. There’s always GeV’s and B-modes and jargon and, well, math. So, in the event that you’d actually like to understand what the heck everybody is talking about right now I called up my favorite theoretical physicist, CalTech’s Sean Carroll, to help explain the theory of inflation for those of us that don’t do physics. Here it is, in the simplest possible terms.

    Image credit: California Academy of Sciences

    The universe is the same everywhere we look. No matter where we point our telescopes out into the 14 billion light years of space in all directions, we see the same density of stuff. Same amount of matter and number of galaxies. Same gravitational field. The universe is even basically the same temperature everywhere.

    The theory is that in the very first fraction of a second after the big bang happened, the universe expanded into existence.

    It’s awfully smooth, flat, and uniform -- and there’s gotta be a reason why. Inflation theory explains. Simply put, the theory is that in the very first fraction of a second after the big bang happened, the universe expanded into existence. In other words, everything, everywhere existed all at once and it happened faster than the speed of light.

    That’s it. Pretty simple, right? Well, it sounds simple. Until you try to prove that it’s true. Since we can’t go back in time to watch the creation of the universe (whomp whomp), the best way to know that theory is right is to look for leftovers of its aftermath. So scientists have been trying to spot evidence that the rapid inflation of the universe messed with gravity.

    At NASA, Bugs Get Splattered for Science

    Here’s the thing about airplanes: In order to function at peak efficiency their wings have to be completely smooth. In engineering they call it optimal laminar flow--meaning air can move over the wings without any disruption. But there’s a big problem in achieving optimal flow when you take airplane wings out of an engineer’s wind tunnel and put them into use outdoors. Actually, it’s not a big problem. It’s a bug problem.

    It’s kind of hard to believe, but even the smallest of bumps on a wing can mess up laminar flow. All those accumulated bug guts eventually mess up an airplane’s fuel efficiency by increasing drag. It’s a problem that folks have been attempting to solve for more than 60 years. The good news is NASA is on it. Their Langley-based bug team is working on finding the optimal material for repelling bug innards.

    Photo credit: Flickr user tabor-roeder via Creative Commons

    But why is this problem taking so long to solve? According to Mia Siochi, who heads up the team, when she was first tackling a similar problem more than 25 years ago their focus was on surface tension. They’d look at materials like those you use to create anti-stain surfaces on carpet or Teflon. “These materials let water bead on the surface. For things to stick they have to spread,” she says.

    When a bug goes splat, its body goes through chemistry that thickens its fluids.

    But the problem is that bug guts aren’t nearly as simple as water. Turns out, there’s some interesting chemistry that happens inside a bug when it’s about to die. “When the aircraft hits the bugs it’s going at around 150 miles an hour. That’s high impact dynamics. The components of the bug and the blood, it’s a lot of water, but there are a lot of biological components there too. The bug doesn’t know it’s been catastrophically destroyed. So it’s trying to heal. It goes through chemistry that thickens its liquids,” she says.

    To counteract this problem, the team is now looking at more modern ideas. Specifically, superhydrophobic chemistry and biologically-inspired surfaces. By combining chemicals that repel water with surfaces that are textured on a microscopic level (like a lotus leaf) they have begun to have success.

    To test how their new surfaces work, the team has reverse-engineered a vacuum pump to shoot instead of suck. It was a bit of a challenge because the bug has be alive until it hits the surface. If it gets smashed on the side of the gun on its way out the chemistry will be different once it hits its final destination. Once it smushes, they measure the characteristics of the bug residue--how big is the area that it spreads and how high it is?

    Photo credit: NASA

    According to Siochi: “This is uncharted territory in some ways. When we started we actually used bigger bugs. We thought: what’s alive and easy to get? It’s crickets. We started using a fan and a big opening and we’d drop the crickets in. But when you shoot too many you have bug splat on top of bug splat. And then we went to feeding a single bug in at a time.

    We’re materials people. The aerodynamics expert told us our bug was too big. You wouldn’t be hitting a cricket with a plane. So we decided we had to go smaller, but how small? When I was doing the test 25 years ago we mounted samples to a car and drove around. This was at Virginia Tech and a professor of entomology there could look at the splats and tell which bugs were which. So for this project we went back to that table and tried to figure out what was the largest population of bugs that hit the car. So we got flightless fruit flies. And then we had to learn how to propagate them.”

    Urinal Dynamics: How To Avoid Splash

    BYU's Splash Lab (yep, a real department at the University) recently conducted a series of experiments in urinal dynamics--the study of the physics of bathroom usage. Using high-speed video and simulations of male urination in both toilets and urinals, the researchers prescribe the best angle of attack to reduce hazardous splash. Their recommendation: aim for a vertical surface and at a decreased angle to reduce bounceback, and stand close enough to the urinal to prevent the stream from becoming individual droplets before they hit the surface. Maybe it's time to move those urinal fly decals.

    The Story of the First Recorded Human Voice

    Physicist Carl Haber is one of 2013's MacArthur Fellows, the recipient of a genius grant from the MacArthur Foundation. Haber deserves the genius label. Over the past five years, his work on a system called IRENE at the Lawrence Berkeley National Laboratory has helped play back audio recorded more than 100 years ago, even when the recording medium was obsolete or in terrible condition. If that concept sounds vaguely familiar, it should--earlier this year Haber was the first person to hear Alexander Graham Bell's voice preserved in an 1885 recording.

    As described by the MacArthur Foundation, IRENE (which stands for Image, Reconstruct, Erase, Noise, Etc.) is "a non-contact method for extracting high-quality sound from degrading or even broken analog recordings on two- or three-dimensional media. A disc or cylinder is placed in a precision optical metrology system, where a camera following the path of the grooves on the object takes thousands of images that are then cleaned to compensate for physical damage; the resulting data are mathematically interpolated to determine how a stylus would course through the undulations, and the stylus motion is converted into a standard digital sound file."

    If you try to play a vinyl record on your average turntable, a lot of things can wreck your sound. Scratches create annoying skips. Dust collecting on the needle can muddle playback. And if a record is broken, it's unplayable. But that's not the case with IRENE, which can create a digital image of a record even if it's broken into pieces. IRENE is smart enough to skip over scratches and cracks and, essentially, create a musical photocopy.

    The voice of Alexander Graham Bell holds a special place in the history of technology, since his invention of the telephone revolutionized communication. Bell's recordings weren't the first that Haber helped restore, though. Back in 2008, he helped play back the earliest known recording of a human voice, which was made in 1860--17 years before the invention of the phonograph, and 25 years before Bell's recording. In this case, "recording" doesn't mean exactly what we would think.

    French printer Édouard-Léon Scott de Martinville invented phonautograms in the 1850s and was interested in recording human speech--playing that speech back like a record, however, was not part of the plan. Wikipedia explains that Scott's phonautograph "transcribed sound waves as undulations or other deviations in a line traced on smoke-blackened paper or glass. Intended solely as a laboratory instrument for the study of acoustics, it could be used to visually study and measure the amplitude envelopes and waveforms of speech and other sounds, or to determine the frequency of a given musical pitch by comparison with a simultaneously recorded reference frequency."

    Scott's sound recordings are archived on the website, which chronicles the effort that went into playing them back. For a century and a half, playing them seemed impossible. Then, in 2008, came IRENE. Haber's technology was able to read the lines scratched in soot as though they were the grooves of a record, creating a digital file.

    Playing them back, however, was still a huge challenge.

    Finally, We Know Why and How Tea Kettles Whistle

    The odds are good that you have a tea kettle sitting in your kitchen. Maybe you don't use it to make tea--maybe you heat water in it to make oatmeal or coffee. But just about everyone has a kettle, or is at least familiar with the whistle kettles make when their water heats up. Strangely, even after hundreds of years, no one knew exactly why kettles began to whistle when they reached a certain temperature. Or, more accurately, we didn't know how.

    The why is a simple answer: as steam builds up and heats up within the kettle, it causes vibrations. As the steam escapes the kettle more quickly, the vibrations grow more intense, and the whistling gets louder. But how does that produce the all-too-familiar whistling noise? "Although the sound of a kettle is understood to be caused by vibrations made by the build-up of steam trying to escape, scientists have been trying for decades to understand what it is about this process that makes sound," writes

    As far back as the 19th century, John William Strutt, 3rd Baron Rayleigh and author of the foundational text, The Theory Of Sound, was trying to explain it. In the end...Lord Rayleigh was forced to concede that 'much remains obscure as regards the manner in which the vibrations are excited.'

    Photo credit: Flickr user abject via Creative Commons

    Modern science, however, has cracked the case. A pair of researchers from Cambridge have tackled the problem and come up with an explanation. They modeled (in software) how air flows inside a kettle to explain why it creates a whistling noise. Once the air inside the kettle reaches a certain flow speed, small swirling vortices are created. And it's those vortices that can produce sound.

    "As steam comes up the kettle's spout, it meets a hole at the start of the whistle, which is much narrower than the spout itself," writes "This contracts the flow of steam as it enters the whistle and creates a jet of steam passing through it. The steam jet is naturally unstable, like the jet of water from a garden hose that starts to break into droplets after it has travelled a certain distance. As a result, by the time it reaches the end of the whistle, the jet of steam is no longer a pure column, but slightly disturbed. These instabilities cannot escape perfectly from the whistle and as they hit the second whistle wall, they form a small pressure pulse. This pulse causes the steam to form vortices as it exits the whistle. These vortices produce sound waves, creating the comforting noise that heralds a forthcoming cup of tea."

    The size and shape of the opening spout makes the kettle whistle rather than produce another sound. A shorter kettle spout produces a higher pitched whistle, and a longer spout produces a lower one.

    But here's the coolest part: That classic kettle whistle isn't the only sound kettles make. Just as water begins to boil, the kettle produces another sound, which is always at the same pitch as the whistle. That sound is produced by the same effect that causes sound when you blow across the top of an empty bottle. Air in the neck of the bottle is bouncing up and down, while the rest of the air in the bottle is compressed and then bounced upwards. The whistle of the kettle does the same thing.

    Now that these researchers have cracked the mystery of the kettle, they could likely design one that would produce no whistling noise when its water begins to boil. But who would want a silent kettle?

    Testing the Puffing Gun and Unexpected Food Explosions

    Puffing guns were invented over 100 years ago as a way to explosively puff foods like cereal. It's why we have Corn Pops. At a kitchen laboratory in New York, Dave Arnold and his team of molecular gastronomists are reviving the puffing gun, experimenting with ones used by street food vendors in Asia. The results are a tad unpredictable.