Contrary to what scientists previously thought, it’s not only the power of a dog’s muscles that limits how fast the animal can accelerate; instead, it’s the need to keep those front paws on the ground and avoid doing a backflip. Although animals clearly don’t have wheels, the authors have branded this potential imbalance a quadrupedal “wheelie,” according to a study (pdf) published in the journal Biology Letters.
The ability to gain speed quickly is crucial for survival, but there’s a limit as to how rapidly an animal can accelerate. Researchers wondered whether the “wheelie” problem experienced by cars during a drag race could be a factor in four-legged animals’ ability to speed up. They came up with a simple mathematical model… to see how fast a quadruped could accelerate without tipping over backward. The model predicts that the longer the back is in relation to the legs, the less likely a dog is to flip over and the faster it can accelerate. Then the researchers tested the model by going down to the local track, London’s Walthamstow Stadium, and video-recording individual greyhounds as they burst out of the gate in time trials. The acceleration approached–but never exceeded–the limit predicted by the model [Science NOW]. That means that at low speeds, it’s the ability to keep his front end from pitching up that determines a dog’s maximum acceleration.
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The sand that runs through an hourglass may look like a smooth and regular stream of particles, but if you had a big enough hourglass and a fancy enough camera, you’d see that those grains of sand behave in strange ways, not like a regular solid. In fact, the stream of grains begins to look more like a liquid as it falls, with the particles clustering together to form “droplets.”
For the study, published in Nature, researchers created a stream of tiny glass beads, each about the width of a human hair. The team dropped an $80,000 high-speed camera in free fall with the glass to capture still pictures of the same three-centimeter-long section of the grain flow [Science News], and watched as the stream separated into distinct droplets over the course of falling three feet. In another experiment, researchers examined two individual beads under an atomic force microscope, and found that the attraction between the two can be explained by an extremely weak surface tension in the beads. Previously, scientists thought grains did not display surface tension, or if they did, the effects were too small to change the flow of the particles. “But this experiment says that if we look very carefully, we find surface tension is almost zero, but it is not exactly zero” [Science News], says study coauthor Heinrich Jaeger.
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Who knew this spring’s soggy weather fell under the umbrella of physics research? Scientists found that when raindrops fall faster than physics predicts, the drops have actually broken into smaller droplets, according to a study in the journal Geophysical Research Letters. And because weather services gauge rainfall based on the velocity at which droplets fall–conventional wisdom holds that large drops should hit the ground at a higher speed than do smaller droplets–these results could improve the way we predict weather.
All falling objects have a so-called terminal velocity, a speed they can’t surpass due to air resistance. Therefore, larger drops generally should fall faster because their heftier size helps them power through air resistance more easily than little drops. (In the extreme case, think of fog: water droplets so small they don’t fall at all.) But data showing small drops sometimes impact the ground at the same speed as larger ones showed this conventional wisdom was wrong, and has puzzled scientists for years. To solve the mystery, the researchers collected a shower of data using optical equipment over a period of several years. The team clocked about 64,000 raindrops falling in Mexico City. The researchers measured their sizes and velocities only in extremely calm conditions, so the wind that often accompanies rain could not skew the data. They found that some drops plummeted faster than the so-called terminal velocity for their size [ScienceNOW Daily News].
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The sun has been surprisingly quiet lately, and until now astronomers couldn’t figure out why. An 11-year cycle governs solar flares and sunspots, and researchers knew that we were at the end of a cycle in a “solar minimum” or quiet period–but that somnolence has continued for an extra year beyond the point at which researchers expected sunspot activity to resume. Comments Australian astronomer Phil Wilkinson: “We have had a drought of sunspots…. This is the longest period the sun has been quiet since the start of the Space Age. Seeing the sun doing nothing is really exciting,” he said, adding it made physicists wonder how little they really understood [Sydney Morning Herald].
Now, new observations announced at a meeting of the American Astronomical Society reveal a possible explanation: “sluggish” solar jet streams 4,350 miles below the surface of the sun. Every 11 years, the sun simultaneously generates twin streams of plasma at each of its poles. Unlike the jet streams on Earth, the solar versions are magnetized and travel only toward the equator. This migration takes place very slowly–at about 10 kilometers per hour. For reasons still not understood, when the streams reach 22 degrees of latitude, north and south, they touch off a new solar cycle, and the sunspots reappear [ScienceNOW Daily News].
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In several labs around the world, sound waves are doing things they’ve never done before. Teams working in England and the Ukraine have made a sonic laser, or “saser,” which operates in the terahertz range, with sound waves oscillating more than a trillion times per second. Meanwhile, in an Israeli lab, researchers say they’ve created the first ever sonic black hole that traps sound waves and won’t let them escape.
The saser uses packets of sonic vibrations called “phonons” much like a regular laser uses photons. Specifically, the acoustic laser device consists of a sonic beam traveling through a “superlattice” constructed of 50 sheets of material each only atoms thick that are alternately made of gallium arsenide and aluminium arsenide, two materials found in semiconductor [CNET]. The phonons bounce back and forth inside the lattice, which causes more phonons to be released and amplifies the overall signal. The result is the formation of an intense series of synchronised phonons inside the stack, which leaves the device as a narrow saser beam of high-frequency ultrasound [New Scientist].
At the moment the terahertz saser, described in a paper published in the journal Physical Review B, is mainly a neat trick, but it may find practical applications down the line, says lead researcher Tony Kent. “Fifty years ago many eminent scientists said that light amplification by the stimulated emission of radiation [lasers] was no more than a scientific curiosity,” says Kent, but lasers are now used for everything from digital storage and cancer treatment to weaponry [New Scientist]. Kent says the new saser technology could lead to breakthroughs in imaging for tiny, nanoscale objects.
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When North Korea announced on May 25th that it had conducted its second underground test of a nuclear weapon, scientists weren’t surprised: They had already picked up seismic readings indicating a subterranean explosion. While seismologists say the readings carried subtle signatures that strongly suggest that the blast was caused by a nuclear device rather than conventional explosives, scientists were still waiting for one more piece of evidence–detecting radionuclide evidence in the form of radioactive gas is the “smoking gun”. And the big news here is that they have not found that signal [BBC Two].
Unlike other nuclear debris, xenon, an unreactive noble gas, can filter out through fissures in the rock after an underground test. Once in the atmosphere, plumes of xenon isotopes can be blown for thousands of miles. In 2006, for example, a [nuclear monitoring] station in Yellowknife, Canada, detected traces of xenon-133 two weeks after North Korea’s first test [Nature News]. But monitoring stations set up by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) have failed to detect any trace of xenon following the May blast, and now it may be too late. Researcher Lassina Zerbo of the CTBTO notes that these xenon isotopes rapidly decay in the atmosphere. This long after the blast, he says, “there is very little chance that we will pick up anything” [Nature News].
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Researchers in Germany produced element 112 in 1996, and now that it has been recognized by the International Union for Pure and Applied Chemistry, it will be the newest addition to the periodic table of the elements. It’s currently known as ununbium, Latin for ‘one-one-two,’ but it will be given an official name before it’s added to the chart.
The new element is one of only 22 elements that are man-made, and it’s 277 times heavier than hydrogen, making it the weightiest element on the periodic table. To make it, scientists at Germany’s Centre for Heavy Ion Research fused the the nuclei of zinc and lead. The atomic number 112 refers to the sum of the atomic numbers of zinc, which has 30, and lead, which has 82. Atomic numbers denote how many protons are found in the atom’s nucleus [Reuters]. Creating new elements isn’t just a why-not-do-it challenge: It has also helped researchers to understand how nuclear power plants and atomic bombs function [Reuters].
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Researchers have recalculated the mass of a gigantic black hole at the core of the M87 galaxy, and found that it’s about two times as massive as previously estimated: The new study says that M87’s black hole weighs the same as 6.4 billion suns. Researchers say the findings may indicate that many black holes have been underestimated, and also say that the results from this “local” galaxy only 50 million light-years away may solve a mystery regarding the extremely distant black holes known as quasars.
Astronomers had previously estimated M87’s total mass, calculating how much of that mass came from both the galaxy’s stars and its central black hole. But previous models didn’t have the supercomputing power to estimate the mass contributed by the galaxy’s “dark halo.” The dark halo is a spherical region surrounding the galaxy that extends beyond its main visible structure. It contains “dark matter”, an as yet unidentified material that cannot be directly detected by telescopes but which astronomers know is there from its gravitational interaction with everything else that can be seen [BBC News].
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The battle of the light bulb may not be quite over. While traditional incandescents will soon be phased out in the United States and abroad, researchers are plugging away to create more efficient versions that comply with looming new standards — while also providing an alternative for consumers who find compact fluorescents objectionable [The New York Times, blog]. In one new study, researchers have demonstrated how an incandescent bulb can be modified to give out much more light without requiring more power.
Lead researcher Chunlei Guo and his colleagues were experimenting with the effect of ultrafast laser pulses on metals when they noticed that pulses lasting only a few femtoseconds–quadrillionths of a second–could fundamentally change the molecular arrangement of metals without melting them [ScienceNOW Daily News]. The laser blasts caused the metal to turn black, which boosted its ability to absorb light. Because the law of thermal radiation state that materials that can absorb a great deal of energy will also emit large amounts of energy, the researchers decided to see if their laser treatment would boost the light output of the metal filament in an ordinary light bulb.
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In chunks of rock quarried from a Russian mountain range, physicists have found perfect “quasicrystals,” a type of material that researchers previously thought could only be created in a lab. Quasicrystals display ordered arrangements and symmetries but are not periodic—that is, they are not defined by a single unit cell (such as a cube) that simply repeats itself in three dimensions [Scientific American]. Instead, quasicrystals have two different geometric structures that alternate, and that are organized in ways which create complex patterns and symmetries. When such a pattern is laid out in two-dimensions, the resulting design is often called Penrose tiling.
Quasicrystals were first created in the lab in 1984, and physicist Paul Steinhardt, a coauthor of the current study, says the hunt for naturally occurring quasicrystals began about 10 years ago. “The latest issue surrounding quasicrystals has been could nature ever make them? … When we make them in the lab we try very hard to make perfect quasicrystals, but nature has no such goal” [Discovery News]. The researchers put out a call to mineralogists around the world, asking them to send in likely rock samples for testing.
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In the realm of quantum mechanics, atoms and subatomic particles just don’t follow the rules that we’re governed by in the larger world of classical mechanics. For example, the theory of quantum mechanics predicts that two or more particles can become “entangled” so that even after they are separated in space, when an action is performed on one particle, the other particle responds immediately. Scientists still don’t know how the particles send these instantaneous messages to each other, but somehow, once they are entwined, they retain a fundamental connection [LiveScience].
Now, a new study has dragged entanglement a little bit closer to our classical world. Researchers managed to entangle two pairs of vibrating ions so that when the motion of one pair of ions was changed, the other pair reflected the change as well. Previously, researchers have entangled particles in much more esoteric ways, coordinating the spin of electrons or the polarization of photons. With this study, says coauthor John Jost, “We’ve entangled something that has never been entangled before, and it’s the kind of physical, oscillating system you see in the classical world, just much smaller” [LiveScience].
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Last week’s official dedication of the National Ignition Facility, the massive experiment in nuclear fusion, has set some physicists to plotting ways in which nuclear fusion could be put to work in a new generation of nuclear power plants. Although doubters say that NIF may not even be able to produce a controlled fusion reaction, the same reaction that occurs in the heart of the sun and in thermonuclear weapons, boosters such as U.S. Energy Secretary Steven Chu are already discussing how fusion energy could best be harnessed.
Chu notes that the Obama administration’s decision to halt construction of the Yucca Mountain repository for nuclear waste has renewed interest in reactors that could actually reduce the nuclear waste produced by traditional nuclear power plants. There are “a resurgence of hybrid solutions of fusion fission where the fusion would impart not only energy, but again creates high-energy neutrons that can burn down the long-lived actinides” [Technology Review], says Chu. Actinides are a group of radioactive chemical elements, including plutonium and uranium, which compose some of the radioactive waste from traditional fission reactors.
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Researchers have more evidence that takes aim at the old stereotype that boys are better at math than girls. Psychologist Janet Hyde had previously studied scores on standardized math tests in the United States, and found no difference in performance between girls and boys. Her new study expands the scope of the work by analyzing international data. She and her colleague analyzed studies from around the world on math performance along with gender inequality as measured by the World Economic Forum’s Gender Gap Index. This index measures the gap between men and women in economic opportunity, educational attainment and other socioeconomic factors [LiveScience].
They found that countries with poor gender equality, like India, had a larger gender gap in math, while in countries with excellent gender equality, like the Netherlands, girls performed as well as boys. If males really did have an innate advantage in math, the researchers note, that advantage should be obvious throughout all these cultures. Instead, the study suggests that cultural issues are the basis of the math gender gap.
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Luminaries gathered today at a lab in Livermore, California to toast the opening of the National Ignition Facility, a massive physics experiment aiming to recreate the reaction that takes place in the hearts of stars: nuclear fusion. “Bringing Star Power to Earth” reads a giant banner that was recently unfurled across a building the size of a football stadium [The New York Times]. Scientists are now ready to begin firing the world’s most powerful laser, comprised of 192 separate beams, at a target the size of a match head. Yet for all the celebration and hoopla, doubters note that there’s no guarantee that the fusion researchers will achieve their goal.
The project’s director, Ed Moses, said that getting to the cusp of ignition (defined as the successful achievement of fusion) had taken some 7,000 workers and 3,000 contractors a dozen years, their labors creating a precision colossus of millions of parts and 60,000 points of control, 30 times as many as on the space shuttle. “It’s the cathedral story,” Dr. Moses said…. “We put together the best physicists, the best engineers, the best of industry and academia” [The New York Times]. The project has also cost at least $3.5 billion. NIF’s researchers will spend the next year gradually increasing the energy of the laser beams, and say serious ignition experiments will begin next year.
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A new optical storage technique that records in five dimensions could hold up to 10,000 times what a standard DVD can store. The new technology could see a whopping 1.6 terabytes of information fit on a DVD-sized disc [BBC], whereas a DVD now can hold only 8.5 gigabytes and a Blu-ray disc up to 50.
Discs started out storing information in two dimensions and more recently have been stepped up to three. By using gold nanorods [the researchers] were able to add two additional dimensions, one based on the colour spectrum, and the other on polarisation [PhysOrg]. The key for his team was to find a material for the disk that could store this extra information…. That ideal material contains gold, rod-shaped nanoparticles of different sizes and orientations [Nature].
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