Thursday, 30 September 2010

Johnald's Fantastical Daily Link Splurge


Posted: 29 Sep 2010 03:25 PM PDT

Monkeys may possess cognitive abilities once thought unique to humans, raising questions about the nature of animal awareness and our ability to measure it.
In the lab of University of Wisconsin neuroscientist Luis Populin, five rhesus macaques seem to recognize their own reflections in a mirror. Monkeys weren't supposed to do this.
"We thought these subjects didn't have this ability. The indications are that if you fail the mark test, you're not self-aware. This opens up a whole field of possibilities," Populin said.
Populin doesn't usually study monkey self-awareness. The macaques described in this study, published Sept. 29 in Public Library of Science One, were originally part of his work on attention deficit disorder. But during that experiment, study co-author Abigail Rajala noticed the monkeys using mirrors to study themselves.

So-called mirror self-recognition is thought to indicate self-awareness, which is required to understand selfhood in others, and ultimately to be empathic. Researchers measure this with the "mark test." They paint or ink a mark on unconscious animals, then see if they use mirrors to discover the marks.
It was once thought that only humans could pass the mark test. Then chimpanzees did, followed by dolphins and elephants. These successes challenged the notions that humans were alone on one side of a cognitive divide. Many researchers think the notion of a divide is itself mistaken. Instead, they propose a gradual spectrum of cognitive powers, a spectrum crudely measured by mirrors.
Indeed, macaques — including those in Populin's study — have repeatedly failed the mark test. But after Rajala called attention to their strange behaviors, the researchers paid closer attention. The highly social monkeys only rarely tried to interact with the reflections. They used mirrors to study otherwise-hidden parts of their bodies, such as their genitals and the implants in their heads. Mark tests not withstanding, they seemed quite self-aware.
"I think that these findings show that self-awareness is not an all-or-nothing phenomenon," said Lori Marino, an Emory University evolutionary neurobiologist who was not involved in the study. "There may be much more of a continuum in self-awareness than we thought before,"
According to Emory University primatologist Frans de Waal, the new findings fit with his work on capuchin monkeys who don't quite recognize themselves in mirrors, but don't treat the reflections as belonging to strangers. "As a result, we proposed a gradual scale of self awareness. The piece of intriguing information presented here may support this view," he said.
However, de Waal cautioned that "many scientists would want more tests and more controls" — a warning especially salient in light of a high-profile controversy involving Marc Hauser, a Harvard University evolutionary biologist who appears to have overstated the cognitive powers of his own monkeys.
"What you're seeing in the videos is subject to all kinds of interpretations," said Gordon Gallup, a State University of New York at Albany psychologist who invented the mirror test, and has administered it with negative results to rhesus monkeys. "I don't think these findings in any way demonstrate that rhesus monkeys are capable of recognizing themselves in mirrors."
Populin said his monkeys may have developed an unusual familiarity with mirrors, which are given to them as toys during infancy. The presence of saltshaker-sized implants screwed into their skulls may also have captured their interest more readily than an inked mark.
Marino, who helped demonstrate self-recognition in bottlenose dolphins, disagreed with Gallup. "The videos are absolutely convincing," she said. "I have been trying to find an alternative explanation for the results – and haven't come up with one yet."

Marino said the findings fit with other research on monkey cognition, including a since-replicated Journal of Experimental Psychology study in which macaques displayed unexpectedly sophisticated math skills and passed other, non-mirror-based tests of self-awareness.
"There are many ways to look at animals. Mirror tests are not the end-all and be-all," said Diana Reiss, a mammal cognition specialist at the City University of New York.
If research continues to find that monkeys possess higher-than-expected awareness, it could influence how researchers and the public think about biomedical research on monkeys. Macaques were critical in the development of a polio vaccine during the 20th century and, more recently, the refinement of embryonic stem cell techniques.
"I would absolutely hope that we do not stop using them now. Their contributions have been immense," said Populin, who studies how ritalin affects the brain's prefrontal cortex.
"There are decisions I would make with a monkey, that I would not feel comfortable making with a chimpanzee," said University of Wisconsin psychologist Chris Coe, who was not involved in the study. "Some of the other cognitive abilities that monkeys would have to show, I don't believe they do. I don't believe they sit and ponder their fate, or reflect on the past, or fret about the future, because they are able to see themselves in a mirror," he said.
"We don't know whether they have a sense of past or future," said Marino, who called Coe's research distinction an ethical non-sequitur. "Whether an animal has a sense of the past or future is irrelevant to the issue of whether they can suffer in the present."
Even if Coe accepts human-benefiting research involving contagious diseases or invasive procedures in monkeys that he wouldn't in chimps, however, he said the findings underscore the importance of improving research animal conditions. The macaques' unexpected self-awareness certainly influences the equations by which society must continually balance the harms and benefits of research.
"A study such as this one, that pushes our own awareness of what monkeys can and can't do, challenges us," Coe said. "I'm not going to argue that having animals live in small cages is so wonderful. One has to reflect on that."
A more accurate understanding of animal awareness may ultimately require better tools. Many researchers are skeptical of the mirror test, which Marino said "is shaped more by the cognitive limitations of human researchers than anything else."
Wrote Marino in an e-mail, "Other animals may be more deeply contemplative than humans – we just don't know. That's really the bottom line. Any scientist who tells you they know that other animals don't think as richly or as complexly as humans — is, well, not being scientific."
Image & Videos: 1) Rhesus macaques. Paul Asman and Jill Lenoble, Flickr. 2) Rhesus macaque using a mirror to inspect parts of himself that cannot typically be seen./University of Wisconsin. 3) Rhesus macaque using a mirror to study the implant in his head./University of Wisconsin.
Note: From the study: "All efforts were made to ameliorate suffering of the animals. Specifically, all procedures were approved by the University of Wisconsin Animal Care Committee and were in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals."
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Citation: "Rhesus monkeys (Macaca mulatta) do recognize themselves in the mirror: implications for the evolution of self-recognition." By Abigail Z. Rajala, Katharine R. Reininger, Kimberly M. Lancaster, Luis C. Populin. Public Library of Science One, September 29, 2010.
Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on an ecological tipping point project.
Posted: 29 Sep 2010 02:16 PM PDT

After years of saying habitable exoplanets are just around the corner, planet hunters have finally found one. Gliese 581g is the first planet found to lie squarely in its star's habitable zone, where the conditions are right for liquid water.
"The threshold has now been crossed," said astronomer R. Paul Butler of the Carnegie Institution of Washington, one of the planet's discoverers, in a press briefing Sept. 29. "The data says this planet is at the right distance for liquid water, and the right mass to hold on to a substantial atmosphere."
The discovery is both "incremental and monumental," comments exoplanet expert Sara Seager of MIT, who was not involved in the new study. When a recent study predicted the first habitable world should show up by next May, Seager rightly said the real answer was more like "any day now."
"We've found smaller and smaller planets that got closer and closer to the habitable zone," she said. "But this is the first that's in the habitable zone."
The new planet is one of six orbiting the star Gliese 581, a red dwarf 20 light-years from Earth. Two of the planet's siblings, dubbed planets C and D, have also been hailed as potentially habitable worlds. The two planets straddle the region around the star where liquid water could exist — 581c is too hot, and 581d is too cold. But 581g is just right. The discovery will be published in the Astrophysical Journal and online at
The new planet is about three times the mass of Earth, which indicates it is probably rocky and has enough surface gravity to sustain a stable atmosphere. It orbits its star once every 36.6 Earth days at a distance of just 13 million miles.
The surface of a planet that close to our sun would be scorching hot. But because the star Gliese 581 is only about 1 percent as bright as the sun, temperatures on the new planet should be much more comfortable. Taking into account the presence of an atmosphere and how much starlight the planet probably reflects, astronomers calculated the average temperature ranges from minus 24 degrees to 10 degrees above zero Fahrenheit.
But the actual temperature range is even wider, says astronomer Steven Vogt of the University of California, Santa Cruz, who designed some of the instruments that helped find the planet. Gravity dictates that such a close-in planet would keep the same side facing the star at all times, the same way the moon always shows the same face to Earth.
That means the planet has a blazing-hot daytime side, a frigid nighttime side, and a band of eternal sunrise or sunset where water — and perhaps life — could subsist comfortably. Any life on this exotic world would be confined to this perpetual twilight zone, Vogt says, but there's room for a lot of diversity.
"You can get any temperature you want on this planet, you just have to move around on its surface," Vogt said. "There's a great range of eco-longitudes that will create a lot of different niches for different kinds of life to evolve stably."

Another advantage for potential life on Gliese 581g is that its star is "effectively immortal," Butler said. "Our sun will go 10 billion years before it goes nova, and life here ceases to exist. But M dwarfs live for tens, hundreds of billions of years, many times the current age of the universe. So life has a long time to get a toehold."
The discovery is based on 11 years of observations using the HIRES spectrometer at the Keck Telescope in Hawaii, combined with data from the HARPS (High-Accuracy Radial-velocity Planet Searcher) instrument at the European Southern Observatory in La Silla, Chile.
Both instruments looks for the small wobbles stars make as their planets' gravity tugs them back and forth. The HIRES project started looking for planets 25 years ago, back "when looking for planets made you look like a nut," Butler said. At first the instruments could detect changes in a star's velocity that were 300 meters per second or larger. That's why the first extrasolar planets discovered were almost exclusively hot Jupiters: These monstrous planets that sit roastingly close to their stars will exert a bigger gravitational pull.
Since then, techniques have improved so that changes as small as 3 meters per second can be seen. That wouldn't be enough to see Earth from 20 light-years away, Butler says. Because red dwarfs are so small and their habitable zones so close, though, Earth-sized planets have enough gravitational oomph to make a difference.
"The excitement here is that by looking at stars that are small it's much easier to find small planets," said exoplanet expert David Charbonneau of Harvard, who is hunting for small planets that cross in front of dwarf stars. "I think it's great news for those of us looking for this kind of thing around this kind of star."
But finding them takes a long time. In all, 238 measurements of the star's wobbles, went into the discovery, and each measurement took a full night of observing.
For Butler and Vogt, though, 11 years wasn't so long to wait. He's actually surprised that a potentially habitable planet showed up so quickly and so nearby.
"The fact that we found one so close and so early on in the search suggests there's a lot of these things," Butler says. Only about 100 other stars are as close to Earth as Gliese 581, and only 9 of them have been closely examined for planets. Odds are good that 10 to 20 percent of stars in the Milky Way have habitable planets, Vogt says.
Finding them won't take a huge advance in technology, he adds. It will just take more telescope time.
"I have suggested that we build a dedicated automated planet finder to do this kind of work 365 nights a year," he said. "If we had something equivalent to Keck that we could use every night, these things would be pouring out of the sky."

Image: 1) Lynette Cook. 2) The planetary orbits of the Gliese 581 system compared to those of our own solar system. Zina Deretsky/National Science Foundation.
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Posted: 29 Sep 2010 11:47 AM PDT

There may be many more "extinct" mammals waiting to be rediscovered than conservation biologists previously thought.
Categorizing a mammal species as extinct has rested upon two criteria: It has not been seen for more than 50 years, or an exhaustive search has come up empty. But "extinct" species occasionally turn up again, and some species have disappeared more than once. Australia's desert rat kangaroo, for example, was rediscovered in 1931 after having gone missing for almost a century, only to disappear again in 1935 when invasive red foxes moved into the area of the remaining survivors.
In order to determine how often extinct species had been rediscovered, University of Queensland scientists Diana Fisher and Simon Blomberg created a dataset of 187 mammal species that have been reported extinct, extinct in the wild, or probably extinct since 1500, as well as those which have been rediscovered. They also looked at historical data on the threats that caused species to become extinct — or brought them close to it — including habitat loss, introduced species and overkill by humans.
It turns out that rumors of the extinction of more than a third of these species have turned out to be premature, the scientists report in Proceedings of the Royal Society B Sept. 29. At least 67 species — a little more than a third of those presumed to be extinct — were later found again. And in most cases, these were animals that had been hardest hit by habitat loss.
Humans and invasive species have been significantly more efficient killers. It's rare that a species reported extinct due to one of these causes has been seen again.
"If you think that a missing species is extinct and the main cause of decline was introduced predators such as feral foxes, cats or rats, then you are very likely to be right," Fisher said. But, she added, "If the main cause of decline was habitat loss, you are quite likely to be wrong if you say that it's extinct, unless it was restricted to a very small area."

As an example, Fisher cites the Malabar civet, which was thought to be extinct due to habitat loss in 1929 but survived in marginal areas at least until 1987 when it was last seen on a cashew plantation. Unfortunately, that animal was killed by villagers, and no more have been seen since.
The team found species that were relatively sparsely distributed over a larger range were more likely to turn up again. But mammals of any particular evolutionary group or body size weren't more likely to be rediscovered.
"I was a little bit surprised that body size was not important," Fisher said. "I thought that small species might not be found so often, because they don't attract much attention, but that wasn't the case."
With these findings in hand, conservation biologists may be better able to target species that are more likely to still be out there somewhere. While species hunted into extinction — such as the Stellar's sea cow — are almost certainly gone forever, individuals of other species may still exist. Whether we find them again or not seems to be directly influenced by how hard we look.
According to Fisher and Blomberg, one or two searches for a missing species aren't likely to succeed, but missing species that were the subject of three to six searches have often been rediscovered. Chances do not continue to get better past this point, though. Species that have been the subject of more than 11 searches, such as the Tasmanian tiger and the Yangtze dolphin, have not been found.
We may hope for the rediscovery of such charismatic species, but the chances of finding some of the lesser-known species that haven't been looked for yet are significantly better. Among the good candidates for rediscovery Fisher lists are the Montane monkey-faced bat of the Solomon Islands, last seen on Guadalcanal in 1990, and Alcom's pocket gopher, which was abundant in a high-elevation forest in Mexico in the late 1990's but hasn't been seen since.
"We should be trying to protect the habitat of recently extinct species," Fisher said. "But this is not easy, because we don't know where they might be rediscovered. It is not necessarily near where the species was last seen."
Gilbert's potoroo, for example, disappeared sometime around 1879 but was rediscovered in 1994 at Two People's Bay in Australia in a reserve that had been set up to protect an endangered bird. Because many rediscovered species had populations that were spread over a wide area, ecologists have a lot of ground to cover in their search for "extinct" mammals.
Images: 1) Desert rat kangaroo. John Gould/Wikimedia Commons. 2) Tasmanian tiger. Smithsonian Institution/Wikimedia Commons. 3) Gilbert's potoroo. John Gould/Wikimedia Commons.
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Posted: 29 Sep 2010 10:40 AM PDT

About 350 million years ago, evolution took one small step for fish, and a giant leap for every terrestrial animal since. According to a new study, it was all made possible by plants.
Prehistoric oxygen levels extrapolated from ancient mineral sediments suggest aquatic life went into overdrive after plants boosted atmospheric oxygen levels. Oceans became so fiercely competitive that some fish sought safe haven outside them.
Some scientists have proposed as much, but the new research, published Sept. 28 in the Proceedings of the National Academy of Sciences, provides the first solid evidence.
"Before this paper, there was essentially no experimental evidence for how oxygen accumulated through animal history. It was only predicted by theory," said Tais Dahl, an evolutionary biologist at the University of Southern Denmark's Nordic Center for Earth Evolution.

Dahl and study co-author Donald Canfield analyzed prehistoric seafloor samples gathered from around the world and dating to between 1.7 billion to 400 million years past. They were especially interested in molybdenum, a mineral widespread in Earth's soil and carried off by erosion. At sea, the particles circulate for about one million years before coming to sedimentary rest.
As they circulate, the particles' atomic configurations are subtly changed by concentrations of atmospheric and aquatic oxygen, making their stratified deposits a record of Earth's oxygen composition. According to Dahl, it's a far more detailed record than can be read in carbon, the traditional source of oxygen extrapolation.
"As you walk back in time, the uncertainty of those models becomes larger and larger," he said. "If you're off by a little bit at a given time, you end up being completely off." Indeterminate carbon records have given rise to two competing interpretations of Earth's prehistoric oxygen levels, and thus the evolution of its life.

Each accepts that planetary oxygen levels first spiked about 550 million years ago, coincident with the first mobile, symmetrical life forms — a benchmark in animal complexity, set until then by sponges. But after that, the interpretations diverge.
The first, traditional view holds that planetary oxygen levels continued to rise steadily, reaching near-contemporary levels well before Earth's life diversified again, some 400 million years ago. In this narrative, it was only a matter of time — another 50 million years, give or take — before a few lagoon-dwelling creatures ventured onto land. Terrestrial life was a clockwork eventuality. Plants provided more oxygen, but weren't essential.
According to the other interpretation, oxygen levels stayed steady from 550 million to 400 million years ago, when the forerunners of modern plants evolved and flourished. Only then did oxygen jump, allowing fish — until then a small, relatively insignificant part of the animal kingdom — to take large, highly predatory forms.
This is the interpretation supported by Dahl and Canfield's molybdenum patterns. Plants, which release oxygen both while they live and as they decompose, are the key.
"The low oxygen level early in animal history limited evolution for fish. After this second oxygenation event, we begin to see large, predatory fish up to 30 feet long," said Dahl. "When land animals walked out of water in the first place, it was to escape predation. It's oxygen that drove the evolution of large predators in the ocean. It's plants that caused oxygen to rise. In principle, you could connect this all."

Images: 1) Dunkleosteus, a 30-foot-long fish with some of history's most powerful jaws, lived just before the first land animals./University of Texas, Arlington. 2) Tiktaalik, considered to be a bridge between aquatic and terrestrial vertebrates./Zina Deretsky, National Science Foundation. 3) A leaf from a gingko tree, remarkably little-changed in 350 million years./Flickr, Geishaboy500.
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Citation: "Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish." By Tais W. Dahl, Emma U. Hammarlund, Ariel D. Anbare, David P. G. Bond, Benjamin C. Gill, Gwyneth W. Gordon, Andrew H. Knoll, Arne T. Nielsen, Niels H. Schovsbo, and Donald E. Canfield. Proceedings of the National Academy of Sciences, Vol. 107 No. 39, September 28, 2010.
Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on an ecological tipping point project.
Posted: 29 Sep 2010 10:21 AM PDT

A desktop black hole created in a lab in Italy has been shown to emit light, a discovery that could seal one of the biggest holes in theoretical physics and pave the way for physicist Stephen Hawking to win a Nobel Prize.
The eerie glow is called Hawking radiation, and physicists have been hunting it for decades. Hawking calculated in 1974 that, rather than gobbling up everything in their path and giving nothing back, black holes can radiate like the heating element in a toaster.
But astrophysical black holes, the ultradense gobs of mass that lurk at the centers of galaxies and are left behind when stars collapse, radiate too dimly to be seen. So instead of looking at real black holes, a group of physicists led by laser physicist Daniele Faccio of Heriot-Watt University in Scotland, created a miniature analog by shooting short pulses of intense laser light into a chip of glass. The results will appear in Physical Review Letters.
"This is an extremely important paper," said physicist Ulf Leonhardt of the University of St Andrews in Scotland, who built an artificial black hole in a phone line in 2008. "The experiment confirms that Hawking radiation can exist in principle."

The basic idea behind Hawking radiation is that the quantum vacuum is not actually empty. Instead, it is a roiling mess of virtual particles and anti-particles that constantly pop into existence and eliminate each other when they meet. If one member of the particle–anti-particle pair is created on the wrong side of an event horizon — the edge of a black hole beyond which not even light can escape — the particles can never meet to destroy each other. An observer outside the black hole would see a perpetual stream of real particles.
But until now, no one had seen any evidence of these particles. Radiation from a black hole the mass of our sun would be 10 million times colder than the cosmic microwave background radiation, the ambient temperature of the universe left over from the Big Bang, which itself is only a few degrees warmer than absolute zero. Larger black holes would be colder still.
Luckily, conceptual counterparts to black holes and their event horizons are not hard to come by. Two physicists in the 1980s independently suggested this thought experiment: Picture a black hole as a river that flows faster and faster as it approaches a waterfall. Fleet-finned fish headed upstream can escape the falls, but at a certain point the water flows faster than the fish can swim. Any hapless fish caught behind that point are doomed to flop backwards over the falls. Replacing fish with light and the river with gravity yields a good simulation of a black hole.
Replace the fish with any other wave and the river with any fluid moving faster than that wave, and the likeness goes deeper. Physicists have found that the math describing light moving in the warped space-time geometry around a black hole is exactly the same as the math describing waves flowing through moving fluids. The analogy works for white holes, theoretical objects where nothing can get in rather than out, as well. And mathematically, Hawking radiation doesn't need gravity or curved space-time at all. It just needs an event horizon.
In the new study, Faccio and colleagues created an event horizon with two quick pulses of laser light inside a piece of glass.
"Your piece of glass, which is equivalent to the river, you can't think of making this travel at velocities that are faster than the speed of light," Faccio said. "But you can create a perturbation inside it."
Light always moves through a vacuum at the same speed, but it gets slowed down by a factor called the refractive index in a medium like water or glass. A pulse of laser light traveling through the glass can change the refractive index, slowing light down even further.
The physicists sent two pulses of infrared laser light into a small rod of silica glass. The first pulse warped the glass, and the second pulse bumped up against this warp, eventually slowing to a standstill. This is exactly what happens to light trying to enter a white hole, Leonhardt says.
A light detector perpendicular to the laser beam picked up one extra photon for every 100 laser pulses on average, Faccio said. The light was extremely dim, invisible to human eyes, but it was there.
"It was pretty amazing," Faccio said. "My first reaction was, it has to be something else, it can't be so easy."
To make sure the photons weren't coming from somewhere else — particularly the fluorescent glow of the glass itself — Faccio and colleagues changed the velocity at which the warp moved through the glass. Theory predicted that changing the warp velocity should alter the wavelength, and therefore the color, of the extra photons.
"We changed the velocity and saw that the color was changing, and then we changed it again and saw it was still changing, and the original colors disappeared and it had shifted to this new wavelength," Faccio said. "There's no other physical mechanism out there that can give the same effect. Hawking radiation is the only physical model known which can give rise to something like this."
Understanding Hawking radiation could help physicists toward a unified theory of physics that works on the scales of stars and galaxies, which are described by Einstein's general relativity, and on the scales of electrons and quarks, described by quantum mechanics.
"These laboratory analogs are important, because they literally shed light on a mysterious phenomenon that seems to connect three areas of physics: gravity, quantum physics and thermodynamics," Leonhardt said. "They show first of all that Hawking radiation is not a mere theoretical dream, but something real."
"While this measurement can't actually tell you anything about quantum gravity," Faccio said, "it does tell you that some of the simple approaches in this direction do work, and they do give you correct predictions. This means that if you develop a quantum theory of gravity, you have something to test this theory on."
There are a few problems with this particular model black hole, Faccio points out. The biggest is that physicists can see only one photon of the pair supposedly created at the event horizon. That means there's no way to tell whether the two photons are quantum-entangled, a key feature of Hawking radiation. Leonhardt and his colleagues are working on making a radiating black hole in an optical fiber that would show whether or not the photons are entangled.
Physicist Dentcho Genov of Louisiana Tech University, who also makes lab-bench–scale black holes using a class of materials called metamaterials, points out that this is only an indirect proof of Hawking radiation. A direct proof would have to come from observing a tiny black hole radiating away in space.
"To have a direct proof is very difficult. I don't know if in my lifetime or in my kids' or grandkids' lifetime that's going to happen," Genov said. "The actual full-scale experimental validation of Hawking radiation is still far away in the future. But this one I think is sufficient."
Correction: The original version of this story said the team of physicists was led by Franco Belgiorno of the University of Milan. Belgiorno is the first author of the paper, but the lab leader was Daniele Faccio.
Image: 1) Artist's conception of the black hole at the center of the Milky Way. Gallery of Space Time Travel. 2) Laser setup at Faccio's lab. Reproduced courtesy of Daniele Faccio.
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Posted: 28 Sep 2010 01:18 PM PDT

The Earth's shadow painted what looks like a silhouette of Jupiter on top of the sun in a new image from NASA's Solar Dynamics Observatory.
"Now we know what it would look like if Jupiter and the sun had a child," joked engineer Ralph Seguin of the Lockheed-Martin Solar and Astrophysics Lab in a writeup on
SDO sits in a geosynchronous orbit directly above a research station near La Cruces, New Mexico, and transmits data on our local star non-stop to two large dishes on the ground. Usually, this position gives SDO a stellar view (so to speak). But near the spring and autumn equinoxes, Earth gets in the way. Once a day for about an hour, the spacecraft, Earth and the sun line up perfectly, and SDO is briefly blind.
The "Sunpiter" image is a composite of images through multiple color filters and a black-and-white magnetogram taken just as the sun was emerging from blackout. Magnetograms, visual representations of the sun's magnetic field, are compiled from a series of images spread out in time. The Jupiter-esque ribbons of color come from Earth's shadow moving across the sun.
"Errors can be beautiful sometimes," @NASA_SDO tweeted earlier today.
Eclipse season doesn't end until October 6, so we may have a full week of bizarre sun photos to look forward to.
UPDATE: Ralph Seguin wrote in to point out that the image is not the result of a spacecraft or processing error; it's more like a side effect of the spacecraft acting normally.
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Posted: 28 Sep 2010 11:59 AM PDT

By Duncan Geere, Wired UK
Microscopic plants less than half a centimeter across may be able to change the paths of 300-mile-wide tropical storms, due to their ability to change the color of the surface of the sea.
Phytoplankton is as common in the oceans as grass is on land, and blooms when cold, nutrient-rich water upwells from the depths. That bloom turns the ocean surface from a deep dark blue to a murky turquoise, henceforth known as murkquoise.
The murkquoise stops the sun from penetrating as far as it normally does into the surface of the sea, making the surface layer much warmer, and the depths cooler. As a result, hurricanes tend to be stronger and last longer.
While these results haven't been isolated in the real world, and there are plenty of other factors affecting hurricane formation too, results from numerical models suggest that reducing the amount of phytoplankton could also keep hurricanes weaker and confine them to equatorial latitudes.

At the Geophysical Fluid Dynamics Laboratory at the U.S. National Oceanic and Atmospheric Administration, researchers simulated a large-scale "phytocide" in the Pacific Ocean and observed the effects on the sea surface and atmosphere. The results were clear — a 15 percent drop in the number of hurricanes that formed each year.
Those that did form didn't track as far north, either. Instead, they wobbled along the equator before fizzling out. Hurricane activity in the subtropical north-west of the Pacific dropped a whopping 70 percent.
But why? Well, removing the murkquoise and allowing the sun deeper into the ocean cools the surface. That in turn cools the air above the surface of the sea, allowing more cool dry air to descend from above. When the hurricane moves into this large-scale cool, dry, air-descending area, its moist, warm upwelling air is countered by it, and so it weakens.
The sinking air is also carried along the surface to the equator, where it rises again, strengthening the already-powerful western winds in the upper atmosphere in the tropics. These winds, if strong enough, can behead storm systems that are beginning to organize into a hurricane by literally blowing them away.
But before you dig out the industrial-strength herbicide to dump into the ocean and reduce the risk of hurricanes, it might be wise to consider the implications. Killing off phytoplankton would be like removing all grass from land. Grazing herbivores would be deprived of their food source and die, depriving carnivores of their food source too.
Before too long, the oceans would be barren and sterile. Probably too great a price to pay for a slightly lowered risk of hurricanes.
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Posted: 28 Sep 2010 08:45 AM PDT
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Month At The Museum

The Museum of Science and Industry in Chicago is looking for one lucky nerd to eat, sleep, breathe and blog about science for a full month this fall. More than 1,500 hopeful science fans entered the "Month at the Museum" contest for the chance to live in the museum full-time, explore behind the scenes and basically be a science exhibit themselves from Oct. 20 to Nov. 18.
Each contestant submitted a bio, an essay and a one-minute video explaining why they'd be the best museum ambassador ever. Somehow the museum folks whittled it down to just five finalists.
Now it's up to you. Meet the finalists, watch their videos and vote for your favorite at before 5 p.m. October 4.
Above: The winner will live, work and be gawked at in this public display cubicle just inside the museum entrance. The museum denizen will have the option of sleeping in the cube, in private quarters up in the professional office area or in the actual exhibits -- including a coal mine, a U-boat rescued from WWII and a toy factory.
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Image and video credit: Museum of Science and Industry, Chicago
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Tuesday, 28 September 2010

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Posted: 27 Sep 2010 04:11 PM PDT

Fungi don't need a weatherman to know which way the wind blows. They make their own. Forcibly ejecting thousands of spores into still air creates a little puff that can carry the fungal offspring 20 times farther than a single spore travels alone, researchers report online the week of September 27 in the Proceedings of the National Academy of Sciences. By working together to stir the air around them, the spores can dodge nearby obstacles such as leaves, reach other air currents, and ultimately land on real estate prime for infection.
Using high speed video, a team of researchers from Harvard, Cornell and the University of California, Berkeley, clocked the launch speed of spores of Sclerotinia sclerotiorum, an omnivorous fungus that attacks numerous plants. The spores initially blasted off at speeds near 20 miles per hour. But the distance they traveled depended on whether they launched alone or en masse. Spores sprung singly were quickly brought down by drag, traveling a mere 0.1 inches before decelerating to zero. But when the fungus ejected waves of spores in quick succession, it created currents that carried spores farther at a slow but steady pace of just over 1 mile per hour.
Modeling these fungal ballistics revealed that every spore doesn't get to take full advantage of this group-generated gust. Spores that launch first set the air in motion, but don't travel as far as their peers.
When the fungus Sclerotinia launches its spores, the first ones to emerge (blue, on right) create a wind that carries subsequent spores (yellow) higher. The last spores to emerge (red) can fly as high as 20 centimeters, much farther than any single spore could go by itself.
Image and Video: Mahesh Bandi, Agnese Seminara/Harvard University and Marcus Roper/UC Berkeley
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Posted: 27 Sep 2010 10:58 AM PDT

Six wannabe Martians are are taking life on Mars for a test drive here on Earth. In a small cylindrical building in the Utah desert, the would-be space explorers live every moment as if they were the first human outpost on the red planet.
The group is sponsored by the privately-funded Mars Society, a nonprofit whose main goal is to send humans to Mars as soon as possible. NASA is still figuring out when and how the first Martian envoys will get there — Obama's latest vision would get humans into Mars orbit around 2035, relying on private aerospace companies to do the heavy lifting.
But the Mars society doesn't want to wait that long. The organization runs two Mars Analog Research Stations, one in the Canadian Arctic and one in Utah, and has plans for a third in Iceland.
The Utah desert, with its barren expanses of rust-colored dirt, looks like it could well be an alien planet. The station is manned by six Mars enthusiasts (some scientists, some not) who live as close to the way they would on Mars as they can: gearing up in spacesuits whenever they venture outside, eating dehydrated food, and worrying about shower and toilet water.
There are some obvious holes. Pancakes probably flip differently in Martian gravity, and the town of Hanksville is a mere 20-minute drive away — Henry David Thoreau was more isolated at Walden Pond. But the participants take it seriously, and hope to build support for the idea of human life on Mars.
Credit: Motherboard.TV
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Posted: 27 Sep 2010 10:24 AM PDT

By Olivia Solon
The Ecole Polytechnic Federale de Lausanne in Switzerland is developing swarms of flying robots that could be deployed in disaster areas to create communication networks for rescuers. The Swarming Micro Air Vehicle Network (SMAVNET) project comprises of robust, lightweight robots and software that allows the devices to wirelessly communicate with each other.
The flying robots were built out of expanded polypropylene with a single motor at the rear and two elevons (control surfaces that enable steering). The robots are equipped with autopilot to control altitude, airspeed and turn rate. A micro-controller operates using three sensors — a gyroscope and two pressure sensors. The robots also have a GPS module to log flight journeys.
The swarm controllers running Linux are connected to an off-the-shelf USB Wi-Fi dongle. The output of these (the desired turn rate, speed or altitude) is sent to the autopilot.
For the swarming, robots react to wireless communication with either neighbouring robots or rescuers, rather than relying on GPS or other positioning sensors that might be unreliable, impractical or expensive. Software algorithms that know where other nearby bots are can stop them from crashing into each other.
Designing swarm controllers is generally quite challenging because there is no clear relationship between the individual robot behaviour and the resultant behaviour of the whole swarm. The researchers therefore looked to biology for the answer.
Army ants were used as inspiration for SMAVNET, since they lay and maintain pheromone paths leading from their nests to food sources. Similarly the flying robots are required to lay and maintain communications pathways between a base node and users in the environment.
Robots can therefore be deployed as "Node MAVs" and "Ant MAVs". The node MAVs spread out to create a grid onto which virtual pheromone can be deposited and detected through local communication. To maintain their position they turn on the spot describing a 10m radius circle.
Ant MAVs then travel along said grid, communicating with the nodes as they travel along them to explore further air space. When the Ant MAV reaches a position in the grid that is not occupied, it becomes a Node MAV, thus extending the reach of the grid until connection with the target user in the environment is achieved.
EPFL has so far experimented with 10 flying robots, which they believe to be the most robots to be flown together as a swarm to date. Check out the video of the project below:

Image: EPFL
Posted: 27 Sep 2010 04:00 AM PDT
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Using high-speed video cameras that capture more than a thousand frames per second, Andrew Mountcastle's videos reveal an insect ballet hidden to plain sight.
"I refer to high-speed cameras as time microscopes. You see things that you can't see with your naked eye," says the Harvard University biologist, who specializes in the flight dynamics of moths.
While a Ph.D. student at the University of Washington, Mountcastle and labmate Armin Hinterwirth were commissioned to replace the Pacific Science Center's outdated video installation. The pair filmed garden-variety insects in flight, their everyday glory unmasked in slow motion.
"What's commonplace in the life of these insects is new and exciting. That's the really neat thing about high-speed cameras," said Mountcastle. "You can point them in any direction, and before long you're capturing something interesting."
Mountcastle took on a tour of his work.


A bumblebee launches itself from a bloom.
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Video: Andrew Mountcastle
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Sunday, 26 September 2010

Johnald's Fantastical Daily Link Splurge

Posted: 24 Sep 2010 01:28 PM PDT

Bright sand streaks can form in the wake of desert cyclones when the whirlwinds break up popcorn-ball-like clumps of sand, a new study shows. The first-ever sighting of bright, instead of dark, dust-devil tracks on Earth could help decipher how these funny features form on Mars.
"This is the first observation and analysis of bright dust-devil tracks on Earth," said geologist Dennis Reiss of Westfälische Wilhelms Universität Münster in Germany, who led the new study. "They are known from Mars, but their formation mechanism is unknown."
Scientists have spotted dust-devil tracks in satellite images of both Earth and Mars, and the Mars rovers Spirit and Opportunity have even seen the dusty cyclones whipping past.
Most of these streaks are darker than the surrounding sand. The coarser the grains of sand are, the darker they appear. When dust devils swish by, they clear their paths of smaller grains, leaving dark tracks like eerie, swirly tattoos. But occasionally, cameras orbiting Mars have caught glimpses of bright streaks on dark sand.
"They have posed a problem," said planetary scientist Ronald Greeley of Arizona State University, who has researched how dark dust-devil trails form on Mars. "How would that mechanism" — blowing small grains aside — "work with the bright streaks? That's been the puzzle."
Reiss and colleagues may have found an answer in the Turpan desert in northwestern China. The crew went there to hunt for dark dust-devil tracks on the ground. Until their field study, such tracks had been seen only from orbit. They found several of the dark tracks and published an "up close and personal" analysis in the July 28 Geophysical Research Letters.
But on April 18, the team saw several active dust devils leaving surprisingly bright tracks. "It was good luck," Reiss said.

When they looked closer, the researchers realized the streaks weren't actually any brighter than usual — they were filled with the same coarse, millimeter-size sand that dust devils normally suck clean. But the surrounding sand had been darkened by five minutes of rainfall the previous night.
The rain had cemented bits of sand, silt and clay into clumps up to a centimeter wide. When the dust devils came through, they destroyed the fragile clusters, revealing the finer sand grains below. The dust devil tracks appeared bright in contrast to the rain-darkened background. The results will be published in an upcoming issue of the journal Icarus.
While there is obviously no rain on Mars, landers and rovers have observed similar clumps that are held together by electrostatic forces. In 1979, Greeley conducted lab experiments showing that charges build up on dry, wind-blown sand particles in a similar manner to the way charge builds up on a balloon when you rub it on your hair. Just like the charged-up balloon can stick to the wall, charged sand grains pull together to form delicate, "popcorn ball" aggregates.
"The destruction of aggregates on Mars would lead also to bright dust devil tracks," Reiss said.
Greeley thinks the idea makes sense. "This is a plausible model for the formation of the bright tracks on Mars," he said. "This is a very nice study, a very nice result."
Images: 1) Bright dust-devil tracks in China. Dennis Reiss/Icarus. 2) Dust-devil track imaged by the HiRISE camera on the Mars Reconnaissance Orbiter. NASA. 3) Microscope images of the clumps of sand, silt and clay that darken the landscape around the bright tracks. Dennis Reiss/Icarus.

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Posted: 24 Sep 2010 10:53 AM PDT

By Ed Grabianowski, io9
We usually think of terraforming as something we'll do in the future to other planets, but we have thousands of years of experience changing the shape of our own planet in profound ways.
The term "terraforming" was invented by author Jack Williamson in his 1942 short story "Collision Orbit," published in Astounding Science Fiction. In the intervening decades, its literal meaning ("Earth forming") has shifted. It still commonly refers to the speculative act of altering non-Earth planets to make them habitable by humans. But anything that drastically changes geography to suit human interests can be called terraforming, even if it happens here on Earth. If only we all had the same interests.

Destructive Terraforming

Humans have been shaping and changing the Earth for thousands of years, sometimes for the better. All too often, though, our terraforming methods have been destructive – sometimes so destructive that they seem like the opposite of terraforming. Mountain top removal mining, for instance, blows the top off of a mountain and fills a nearby valley with the polluted debris. The resulting blasted landscape looks more like we're turning Earth into Mars than the other way around. Maybe we should call it deterraforming. This series of NASA LANDSAT images (below) shows the Hobet mine gradually obliterating a large swath of West Virginia over the course of about 25 years.

Dams radically alter geography by diverting rivers, creating artificial lakes and changing flood patterns. We've had lots of practice – some Middle Eastern dams are four or five thousand years old, and dams dating to the Roman Empire not only still exist, they still function perfectly well. Modern dams are chart-toppers when it comes to the amount of real estate terraformed. Shasta Dam (below) in California blocks the Sacramento River, creating Shasta Lake. The lake covers almost 50 square miles. What was once a verdant valley ecosystem is now completely under water. Change on that scale has happened at the sites of dozens of large dam projects worldwide.

Cities and populations

Cities, of course, aren't built in a few months, and they don't generally change geography instantly. But every city changes the landscape in a thousand small ways that all add up: leveling terrain for construction projects; shifting waterways for drainage; paving over huge areas; tunnel systems for transportation and infrastructure; the heat island effect. If you could somehow strip away the city and see the land beneath, it would look vastly different from how it did before the city was there.
If we talk about cities and population growth as a part of terraforming, we have to talk about the most pervasive, long-term terraforming project ever undertaken – the introduction of huge quantities of greenhouse gases into the atmosphere. That is ultimately how we'll terraform Mars, if we do it, so we've established an interesting test case here on Earth. Increased global temperatures and decreased polar ice levels would be an important first step in terraforming another planet. If we keep at it for another hundred years or so, we'll have a better idea of how it'll play out.
Of course, it's easy to look at all these "detrimental" terraforming methods purely as environmental evils, but everything has a benefit that we're apparently willing to pay the price for. The irrigation, flood control and power generation provided by dams has been significantly helpful for humans. Our desire for cheap on-demand electricity leads to mountain top removal mining, and how many of us would be willing to forego air-conditioning for the next ten years to save a West Virginia mountain?
There's only one sure thing about terraforming: when you change a planet, there will be consequences, and not always the consequences you expect. We'll get deeper into unintended consequences in part two of this series, when we examine more constructive terraforming methods.
Images: 1) Carajás Mine, Brazil/NASA Earth Observatory. 2) NASA Earth Observatory. 3) Shasta Dam/U.S. Bureau of Reclamation.

Sources: NASA Earth Observatory. "Mountaintop Mining in West Virginia." National Performance of Dams Database. "Dam Name: Shasta."
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Posted: 24 Sep 2010 10:13 AM PDT

The Smithsonian National Zoo now has two litters of extraordinarily cute lion cubs to look at via webcam, after the birth of three new cubs on September 22.
These new cubs are closer than half-siblings with the cubs we have been following over the past couple weeks. They have the same father, 4-year-old Luke, and their mothers, Shera and Nababiep, are sisters.
The lion cub webcam now toggles between four different views, so that you can view both litters of cubs, either playing outside or still snuggling with their mother.
Video: New lion cubs with mother Nababiep shortly after birth, September 22./ Smithsonian National Zoo.
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Posted: 24 Sep 2010 09:22 AM PDT

By Duncan Geere, Wired UK
Many estimates of air pollution in developing countries are innaccurate, as there's no network of surface-based sensors that can find the worst-polluted areas. Scientists regularly have to rely on a few dated observations of questionable veracity.
However, Nasa has just published the first long-term global map that shows density of particulate matter below 2.5 micrometres in diameter. This size is important, because it's small enough to get past the body's defences and accumulate in the lungs, making it dangerous to human health. Epidemologists believe that they cause millions of premature deaths each year.
Satellites can't easily scan the surface of the Earth — they instead scan a column of air in the atmosphere, and the difficulty comes in getting readings at a particular level out of that data. The team who produced the map, Aaron van Donkelaar and Randall Martin at Dalhousie University, in Halifax in Nova Scotia, Canada, blended total-column aerosol measurements from satellites with information about how aerosols are distributed vertically in the atmosphere to obtain the data.
The map, as you can see above, shows a wide band of very high concentrations of particulate matter across the Sahara, Middle East, Central Asia and China, only interrupted by the Himalayas. Central Europe also shows a spike, including the south-east corner of England, and urban areas in North and South America stand out too.

The World Health Organisation's recommended level is 10 micrograms per cubic metre, so anything on the map that's green or above is cause for concern. Once in the lungs, the particles can cause asthma, cardiovascular diseases and bronchitis. Some very fine particles can even get into the bloodstream.
Some of the particulate matter is man-made and some is natural, and scientists haven't quite worked out the relative quantities yet, but both are dangerous to human health. In the Arabian and Sahara deserts, its mostly natural mineral dust lifted by the wind, but in eastern China and Northern India, it's more likely to be soot particles emitted by power plants, factories and cars.
The next step is to try and verify some of these measurements by expanding the ground-based network of sensors, with the eventual goal of finding out how long-term exposure to these particles affects human health on large scales.
"We can see clearly that a tremendous number of people are exposed to high levels of particulates", said Martin. "So far, nobody has looked at what that means in terms of mortality and disease."
Image: NASA
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Posted: 24 Sep 2010 07:26 AM PDT

Three hurricanes — Julia, Igor and Karl — look oddly serene in this footage taken from the International Space Station on September 16.
The video is almost 15 minutes long, but it's worth it. It opens on Hurricane Julia at about 7:45 am EDT from 225 miles above the Earth. Julia has since calmed down, but as it moved across the eastern Atlantic it was a raging Category 2 hurricane, with winds of 105 miles per hour.
Hurricane strengths are measured on the Saffir-Simpson Hurricane Scale, which goes from 1 ("Very dangerous winds will produce some damage") to 5 ("Catastrophic damage will occur").
At around 3:15 the view switches to Hurricane Igor, filmed at 9:15 am EDT. Igor was a Category 4 storm with 145 mile per hour winds, and swirled out to cover almost the entire visible slice of the planet. A different camera catches Igor from another angle starting at about 9:10.
A third storm takes focus around 11:42. The space station's cameras caught what was then Tropical Storm Karl at about 10:45 am EDT. Karl since crossed the Yucatan Peninsula overnight and grew into a Category 1 hurricane over the Bay of Campeche with winds of 75 miles an hour.
Seeing these huge storms slide past in a few minutes gives a striking sense of how quickly the International Space Station moves — it zips around Earth once every 90 minutes at about 17,500 miles per hour.
Video: NASA
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Posted: 24 Sep 2010 07:22 AM PDT

By Kate Shaw, Ars Technica
Mnemiopsis leidyi, a comb jelly, doesn't seem like a very formidable predator: it lacks good vision, isn't capable of sensing nearby food via mechanoreception, and can't move quickly enough to strike at prey. Its common name, "the sea walnut," certainly doesn't strike fear into the hearts of men. However, M. leidyi is an extremely effective stealth predator. A new paper in the Proceedings of the National Academy of Sciences this week details how this seemingly innocuous sea creature can be such a successful hunter.
The researchers used 2D digital particle image velocimetry, or DPIV, to study water movement around feeding M. leidyi. During this process, the water is seeded with particles which are then illuminated with a laser. The movement of these particles can be analyzed to visualize the velocity, direction, and movement patterns of the fluid.
DPIV revealed that M. leidyi use millions of cilia to move water and create feeding currents that trap nearby prey and carry it to their mouth. This technique isn't unique among animals; many bivalves and bryozoans use the same strategy. What makes this comb jelly's strategy different is its ability to create a laminar feeding current that is completely undetectable to the prey that's caught in the flow.

The currents created by other animals, such as oysters and mussels, have very high fluid deformation rates, meaning that the disturbance in the water can alert the prey to the presence of danger and give it the chance to escape. In contrast, the feeding currents created by M. leidyi have extraordinarily low deformation rates that are well below the detection thresholds of their prey.
Thanks to the slow speed of the current and the morphology of the comb jelly's mouth, the prey remains blissfully unaware of the impending danger until it is too late: the fluid deformation rates only exceed the prey's detection threshold once it has entered M. leidyi's critical capture zone. There, sticky tentillae in the comb jelly's mouth capture the prey with a near 100 percent success rate.
With this clever strategy, M. leidyi can feed at the same rate as many higher-level copepods and predatory fish (and possibly an even faster rate, according to less conservative estimates). Moreover, the hydrodynamically silent feeding current is capable of entraining a large variety of prey, including small copepods and even some fish larvae. Despite belonging to a basal lineage and lacking many of the attributes of many higher-order predators, the sea walnut's manipulation of fluid dynamics makes it a master stealth predator.
Source Link: Ars Technica
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Posted: 24 Sep 2010 07:07 AM PDT

By Mark Brown, Wired UK
Like many innovations in engineering, a newly developed matrix of sensors, designed to wrap round aircraft, takes much of its inspiration from the natural world. The device is influenced in shape by spiderwebs, and in purpose by birds.
Scientists at Stanford University say that while planes share many senses with birds — replacing eyes with radar and mouths with radio — they don't have a nervous system to track microscopic changes in their bodies. A bird's nerves and tissues allows the animal to sense whether a dive is putting its body under too much strain, for example, and pull up before hurting itself.
The scientists wanted to bring those senses to an airplane, so they created a cobweb-style matrix of sensors, which stretches around an aircraft and is used to detect strain and temperature. It will hook up to the aircraft's computer and allow a pilot to be aware of any tiny cracks or damages in the plane's body, or detect excess air pressure impacting one part of the craft, before they develop into life-threatening problems.
Its future implementation, the Standard researchers claim, will help ensure a much greater level of safety in air transportation.

The system is made up of lightweight sensors, to avoid adding significant weight to aircraft, laid out on top of a plastic polymer sheet. At first, the sheet is very small and doesn't look like a cobweb. That's until it's stretched out and expanded to more than 265 times its original size, where the strong, durable and almost invisible mesh of wires looks like a giant technological cobweb.
Stanford University scientist Fu-Kuo Chang says just one square foot of the sensor-equipped material could stretch far enough to cover an entire car. Plus, the technology will have implications that stretch further than the airline business. It could lead to smarter cars with similar awareness to external forces and internal measures, and wound dressings that tell doctors how far along the healing process is. Mixed with ultra-sonic sonar technology, the university even claims that pregnant women could wear shirts that show off their unborn child. Very creepy.
Other technology which owe their inspiration to the world of biology include Standford University's own Gecko toe-influenced climbing robots, NASA's honey bee-styled self-sacrificing spaceship swarms and General Electric's sensors based on butterfly wings.
Image: Flickr/Tyron Francis
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Posted: 24 Sep 2010 04:00 AM PDT
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The next Mars rover is only about a year away from taking off, and it's already stretching its arms and spinning its wheels in a lab in California. But scientists are still debating exactly where to drop it.
Curiosity (or more formally, the Mars Science Laboratory) is slated to launch in late 2011, and its chief objective is looking for life. That means landing in a spot where the soils formed in water, and where rocks could have preserved chemical traces of living organisms.
Now, after four years of deliberation, the rover crew has narrowed the choice down to their four favorites: a rugged valley full of water-bearing clays; and three craters that may once have been basins, lakes or river deltas. Hundreds of planetary scientists will descend on Monrovia, California, next week to continue the debate.
Image: NASA
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Posted: 23 Sep 2010 06:32 PM PDT

Exploring the peculiar effects of Einstein's relativity is no longer rocket science. Tabletop experiments at a lab in Colorado have illustrated the odd behavior of time, a strangeness typically probed with space travel and jet planes.
sciencenewsUsing superprecise atomic clocks, scientists have witnessed time dilation — the bizarre speeding up or slowing down of time described by Einstein's theories of relativity. The experiments are presented in the Sept. 24 Science.
"Modern technology has gotten so precise you can see these exotic effects in the range of your living room," says physicist Clifford Will of Washington University in St. Louis. The experiments don't reveal any new physics, Will says, but "what makes it cute and pretty cool is they have done it on a tabletop."
Time dilation arises in two situations. In one case, time appears to move slower the closer you are to a massive object, such as the Earth. So a person hovering in a hot-air balloon, for example, actually ages faster than someone standing below.
Time also ticks by faster for someone at rest relative to someone moving. Einstein dramatized this second strangeness with the twin paradox — one 25-year-old twin traveling in a rocket ship near the speed of light for what he perceives as a few months will return to Earth to find the other has reached middle age.
Previous experiments with rockets and airplanes have demonstrated these odd aspects of general and special relativity. The notion of time running slower closer to Earth was even tested on the scale of a multistory physics building at Harvard.
Now advances in laser technology and the field of quantum information science have allowed researchers to demonstrate Einstein's theories at much more ordinary scales.
The researchers used two optical atomic clocks sitting atop steel tables in neighboring labs at the National Institute of Standards and Technology in Boulder, Colorado. Each clock has an electrically charged aluminum atom, or ion, that vibrates between two energy levels more than a million billion times per second. A 75-meter-long optical cable connects the clocks, which allows the team to compare the instruments' timekeeping.
In the first experiment, physicist James Chin-wen Chou and his colleagues at NIST used a hydraulic jack to raise one of the tables 33 centimeters, or about a foot. Sure enough, the lower clock ran slower than the elevated one — at the rate of a 90-billionth of a second in 79 years. In a second experiment the team applied an electric field to one clock, sending the aluminum ion moving back and forth. As predicted, the moving clock ran slower than the clock that was at rest.
"It's pretty breathtaking precision," says physicist Daniel Kleppner of MIT. Of course scientists are well aware of these relativistic effects, he notes. The clocks on GPS devices are also affected by relativity, and appropriate adjustments are made to keep them working properly.
The experiments have more implications for precision instrumentation than they do for relativity, notes Chou. But they are a nice reminder that relativity is always at hand. "People tend to just ignore relativistic effects, but relativistic effects are everywhere," he says. "Every day, people are moving; they are doing things like climbing stairs. It's interesting to think about — are frequent flyers getting younger [because they move so much] or aging faster [because they spend so much time in the air]?"
Image: AAAS/Science
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Posted: 23 Sep 2010 05:05 PM PDT

A hole in the dust disk surrounding our solar system would tell alien observers there are planets here, a new simulation shows. The new model, which tracks thousands of tiny particles beyond the orbit of Neptune, could help astronomers work out the properties of planets in other stars' dust disks.
"We're trying to create a new planet-search technique, and we're practicing on the solar system," said NASA exoplanet scientist Marc Kuchner, lead author of a paper describing the results in the Sept. 7 Astrophysical Journal.
The cloud of dust comes from the Kuiper belt, the region beyond Neptune that contains small, icy bodies, including Pluto. These giant snowballs sometimes smack into each other, sending up flurries of ice grains. These tiny clots of ice and minerals get tugged around by the gravitational influence of giant planets, as well as the solar wind and small nudges from sunlight.
Similar clouds of dust has been spotted around several other stars, including Fomalhaut, the first star to have its planets directly photographed. Most extrasolar planets are too dim to have their portraits taken directly, but their presence can warp the disk of dust and debris around their stars into distinctive shapes, telling outside observers that planets are there.

Kuchner and co-author Christopher Stark of the University of Maryland wondered how much information these dust clouds can offer.
"This field of studying shapes of debris disks has been around for a while, but it's been qualitative," Kuchner said. "We're trying to make it quantitative. We want to get to where you can give us a picture of a debris disk, and we can say bam — here are the planets, and here's how massive they are."
The researchers used a supercomputer at NASA's Goddard Spaceflight Center to simulate 75,000 particles bumping around the Kuiper belt. Their model is the first to include not just collisions between Pluto-sized bodies, but the tiny dust grains as well.
"You have something like a billion billion million particles, and they're all hitting each other," Kuchner said. "Nobody before had figured out how to keep track of all that stuff."
Rather than directly tracking all those particles, Kuchner's model looked at two separate pictures: how the particles moved without collisions, and the density and velocity of the particles. The model then integrated the two pictures to paint a fuller portrait of the dusty disk.
The results showed that a hole in the dust follows Neptune around in its orbit. Neptune's gravity traps some of the dust grains in a gravitational tango called a resonance, which pulls the dust into clumps that precede and follow the gas giant around the sun. Earlier studies have shown that the Earth does the same thing with dust released from the asteroid belt.
"When you have low dust levels, like in today's solar system, dust moves into resonances and makes a gap, which tells you where Neptune is," Kuchner said.
When the fragile dust grains collide, they can annihilate each other, he said. In today's wide, fuzzy Kuiper belt, the particles don't meet very often, so they stick around long enough to fall into resonances with Neptune. But earlier in the solar system's history — and in planetary systems around other stars like Fomalhaut — the dust grains are destroyed before they have a chance to wander away from where they were created.
Kuchner tweaked his model to simulate the solar system at 700 million, 100 million and 15 million years old. As he turned back the clock, the dust disk collapsed into a dense, bright ring.
"Our models of this ring let us sort of look back in time to when the solar system was young," said Marc Kuchner. "When we do that we find that this ring looks just like the rings we see around other stars, like Fomalhaut."
The model has some shortcomings. For one thing, it ignores grains smaller than a certain threshold, which could be important for creating dust. Also, astronomers don't have a very clear picture of what the Kuiper belt contains, so the model's input parameters could be off.
Still, the model is a welcome addition to other Kuiper-belt researchers. "I'm happy to see another well-studied Kuiper-belt–dust paper in the community. We need it," said astronomer Amara Graps of the Southwest Research Institute in Boulder, Colorado. "The dusty byproduct of those small bodies is still not well-understood, and I believe that Marc made an important contribution."

Images: 1) NASA/Goddard/Marc Kuchner and Christopher Stark 2) NASA/ESA/P. Kalas (Univ. of California, Berkeley) et al.
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