Slashdot Mirror
Domain: arxivblog.com
Stories and comments across the archive that link to arxivblog.com.
Stories · 108
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Wireless Network Modded To See Through Walls
KentuckyFC writes "The way radio signals vary in a wireless network can reveal the movement of people behind closed doors, say researchers who have developed a technique called variance-based radio tomographic imaging which processes wireless signals to peer through walls. They've tested the idea with a 34-node wireless network using the IEEE 802.15.4 wireless protocol (the personal area network protocol employed by home automation services such as ZigBee). The researchers say that such a network could be easily distributed by the police or military wanting to determine what's going on inside a building. But such a network, which uses cheap off-the-shelf components, might also be easily deployed by your neighbor or anybody else wanting to monitor movements in your home." -
A Galaxy-Sized Observatory For Gravitational Waves
KentuckyFC writes "Gravitational waves squash and stretch space as they travel through the universe. Current attempts to spot them involve monitoring a region of space several kilometers across on Earth for the telltale signs of this squeezing. These experiments have so far seen nothing. But by monitoring an array of pulsars throughout the galaxy, astronomers should be able to see the effects of gravitational waves passing by. They say such an array of pulsars should effectively shimmer as the gravitational waves wash over it, like a grid of buoys bobbing on the ocean. That'll create an observatory that is effectively the size of the entire galaxy. These observations should be capable of monitoring how galaxies and supermassive black holes evolve together, and shed light on the physics of the early universe. Best of all, the next generation of radio-telescope arrays should be capable of making these observations at a cost of around $66 million over ten years. That's a small fraction of the hundreds of millions that Earth-based observatories have already cost." -
Scale Models Can "Compute" Casimir Forces
KentuckyFC writes "Place two conducting parallel plates a few nanometres apart and the well-known but difficult-to-measure Casimir force will push them together. The force depends crucially on the shape of the plates but nobody is exactly sure how. That's because calculations with anything other than flat plates are fiendishly difficult and measurements are even harder. Now a group at MIT has come up with an ingenious new way to investigate Casimir forces. What the team has noticed is a mathematical analogy between the Casimir force acting on microscopic bodies in a vacuum and the electromagnetic behavior of macroscopic bodies floating in a conducting fluid. Their idea is to build a centimeter-scale metal model of the system they want to investigate, place it in salt water, and bombard it with microwaves and see what happens. The team says the experiment does not measure the force on the scale model but instead a quantity that is mathematically related to the force. So the experiment is not a simulator but actually an analog computer that calculates the force (abstract). What's exciting is that the method should for the first time give researchers a way of testing nano-machines designed to exploit the Casimir force." -
Scale Models Can "Compute" Casimir Forces
KentuckyFC writes "Place two conducting parallel plates a few nanometres apart and the well-known but difficult-to-measure Casimir force will push them together. The force depends crucially on the shape of the plates but nobody is exactly sure how. That's because calculations with anything other than flat plates are fiendishly difficult and measurements are even harder. Now a group at MIT has come up with an ingenious new way to investigate Casimir forces. What the team has noticed is a mathematical analogy between the Casimir force acting on microscopic bodies in a vacuum and the electromagnetic behavior of macroscopic bodies floating in a conducting fluid. Their idea is to build a centimeter-scale metal model of the system they want to investigate, place it in salt water, and bombard it with microwaves and see what happens. The team says the experiment does not measure the force on the scale model but instead a quantity that is mathematically related to the force. So the experiment is not a simulator but actually an analog computer that calculates the force (abstract). What's exciting is that the method should for the first time give researchers a way of testing nano-machines designed to exploit the Casimir force." -
Gravitational Waves May Have Been Detected In 1987
KentuckyFC writes "In 1987, a physicist called Joe Weber claimed to have detected gravitational waves at the same time that other scientists spotted a supernova called SN1987A. His claims were largely ignored because of calculations showing that gravitational waves could not be strong enough to be picked up by Weber's equipment, a set of giant aluminium cylinders designed to vibrate as the waves passed by. But these calculations were based on first order effects in the way spacetime can be distorted. Now a new analysis shows that second order effects can enhance gravitational waves by four orders of magnitude, but only when certain asymmetries are present. It turns out that SN1987A possesses just the right kind of asymmetries to make this enhancement possible because the supernova wasn't entirely spherical. Which means that Weber, who died in 2000, may have been the first to see gravitational waves after all." -
Gravitational Waves May Have Been Detected In 1987
KentuckyFC writes "In 1987, a physicist called Joe Weber claimed to have detected gravitational waves at the same time that other scientists spotted a supernova called SN1987A. His claims were largely ignored because of calculations showing that gravitational waves could not be strong enough to be picked up by Weber's equipment, a set of giant aluminium cylinders designed to vibrate as the waves passed by. But these calculations were based on first order effects in the way spacetime can be distorted. Now a new analysis shows that second order effects can enhance gravitational waves by four orders of magnitude, but only when certain asymmetries are present. It turns out that SN1987A possesses just the right kind of asymmetries to make this enhancement possible because the supernova wasn't entirely spherical. Which means that Weber, who died in 2000, may have been the first to see gravitational waves after all." -
Motor Made From Liquid Film
KentuckyFC writes "Last year, a group of Iranian physicists made a puzzling discovery. They placed a thin film of water in a small cell and bathed it in two perpendicular electric fields. To their surprise this caused the water to rotate. They called their device a liquid film motor and posted on the web a cool set of movies showing the phenomenon. The puzzle is this: the electric fields are static, so what's driving the motor? Now another group of physicists has the answer: a complex interaction between the electric field, the cell container and the liquid causes water to move along the cell wall. Crucially, it moves in opposite directions on opposite sides of the cell and so sets up a circular flow. The phenomenon works only when friction and surface tension are significant forces so the effect is entirely scale dependent. That's probably why we haven't seen it before and also why it could have important implications for microfluidic devices such as lab-on-a-chip." -
Motor Made From Liquid Film
KentuckyFC writes "Last year, a group of Iranian physicists made a puzzling discovery. They placed a thin film of water in a small cell and bathed it in two perpendicular electric fields. To their surprise this caused the water to rotate. They called their device a liquid film motor and posted on the web a cool set of movies showing the phenomenon. The puzzle is this: the electric fields are static, so what's driving the motor? Now another group of physicists has the answer: a complex interaction between the electric field, the cell container and the liquid causes water to move along the cell wall. Crucially, it moves in opposite directions on opposite sides of the cell and so sets up a circular flow. The phenomenon works only when friction and surface tension are significant forces so the effect is entirely scale dependent. That's probably why we haven't seen it before and also why it could have important implications for microfluidic devices such as lab-on-a-chip." -
Motor Made From Liquid Film
KentuckyFC writes "Last year, a group of Iranian physicists made a puzzling discovery. They placed a thin film of water in a small cell and bathed it in two perpendicular electric fields. To their surprise this caused the water to rotate. They called their device a liquid film motor and posted on the web a cool set of movies showing the phenomenon. The puzzle is this: the electric fields are static, so what's driving the motor? Now another group of physicists has the answer: a complex interaction between the electric field, the cell container and the liquid causes water to move along the cell wall. Crucially, it moves in opposite directions on opposite sides of the cell and so sets up a circular flow. The phenomenon works only when friction and surface tension are significant forces so the effect is entirely scale dependent. That's probably why we haven't seen it before and also why it could have important implications for microfluidic devices such as lab-on-a-chip." -
First Evidence of Supernovae Found In Ice Cores
KentuckyFC writes "Supernovae in our part of the Milky Way ought to have a significant impact on the atmosphere. In particular, the intense gamma-ray burst would ionize oxygen and nitrogen in the mid to upper atmosphere, increasing the levels of nitrogen oxide there by an order of magnitude or so. Now a team of Japanese researchers has found the first evidence of a supernova's impact on the atmosphere in an ice core taken from Dome Fuji in Antarctica. The team examined ice that was laid down in the 11th century and found three nitrogen oxide spikes, two of which correspond to well known supernovae: one event in 1006 AD and another in 1054 AD, which was the birth of the Crab Nebula (abstract). Both were widely reported by Chinese and Arabic astronomers at the time. The third spike is unexplained, but the team suggests it may have been caused by a supernova visible only from the southern hemisphere or one that was obscured by interstellar dust." -
First Evidence of Supernovae Found In Ice Cores
KentuckyFC writes "Supernovae in our part of the Milky Way ought to have a significant impact on the atmosphere. In particular, the intense gamma-ray burst would ionize oxygen and nitrogen in the mid to upper atmosphere, increasing the levels of nitrogen oxide there by an order of magnitude or so. Now a team of Japanese researchers has found the first evidence of a supernova's impact on the atmosphere in an ice core taken from Dome Fuji in Antarctica. The team examined ice that was laid down in the 11th century and found three nitrogen oxide spikes, two of which correspond to well known supernovae: one event in 1006 AD and another in 1054 AD, which was the birth of the Crab Nebula (abstract). Both were widely reported by Chinese and Arabic astronomers at the time. The third spike is unexplained, but the team suggests it may have been caused by a supernova visible only from the southern hemisphere or one that was obscured by interstellar dust." -
Human Eye Could Detect Spooky Action At a Distance
KentuckyFC writes "The human eye is a good photon detector--it's sensitive enough to spot photons in handfuls. So what if you swapped a standard photon detector with a human eye in the ongoing experiments to measure spooky-action-at-a-distance? (That's the ability of entangled photons to influence each other, no matter how far apart they might be.) A team of physicists in Switzerland have worked out the details and say that in principle there is no reason why human eyes couldn't do this kind of experiment. That would be cool because it would ensure that the two human observers involved in the test would become entangled, albeit for a short period time. The team, led by Nic Gisin, a world leader on entanglement, says it is actively pursuing this goal (abstract) so we could have the first humans to experience entanglement within months." -
Human Eye Could Detect Spooky Action At a Distance
KentuckyFC writes "The human eye is a good photon detector--it's sensitive enough to spot photons in handfuls. So what if you swapped a standard photon detector with a human eye in the ongoing experiments to measure spooky-action-at-a-distance? (That's the ability of entangled photons to influence each other, no matter how far apart they might be.) A team of physicists in Switzerland have worked out the details and say that in principle there is no reason why human eyes couldn't do this kind of experiment. That would be cool because it would ensure that the two human observers involved in the test would become entangled, albeit for a short period time. The team, led by Nic Gisin, a world leader on entanglement, says it is actively pursuing this goal (abstract) so we could have the first humans to experience entanglement within months." -
How To Build a Short Foucault Pendulum
KentuckyFC writes "Set a pendulum in motion and you'll inevitably give it an ellipsoidal motion, which naturally tends to precess. That's bad news if you want to build a Foucault Pendulum, a bob attached to a long wire swinging in a vertical plane that appears to rotate as the Earth spins beneath it. The natural precession always tends to swamp the rotation due to the Earth's motion. There is a solution, however: the behavior of the ellipsoidal motion is inversely proportional to the pendulum's length. So the traditional answer has been to use a very long pendulum (Foucalt's original in Paris is 67 meters long). Now scientists at Carnegie Mellon University have another solution (abstract). They've created a motor that drives a pendulum in a way that always cancels out the precession. That means the effect of Earth's rotation can be seen on much shorter pendulums such as the 3-meter pendulum on which they've tested their motor. That's just the start though. They say there is no limit to how short the new generation of Foucault Pendulums can be, and even talk about the possibility of tabletop devices." -
How To Build a Short Foucault Pendulum
KentuckyFC writes "Set a pendulum in motion and you'll inevitably give it an ellipsoidal motion, which naturally tends to precess. That's bad news if you want to build a Foucault Pendulum, a bob attached to a long wire swinging in a vertical plane that appears to rotate as the Earth spins beneath it. The natural precession always tends to swamp the rotation due to the Earth's motion. There is a solution, however: the behavior of the ellipsoidal motion is inversely proportional to the pendulum's length. So the traditional answer has been to use a very long pendulum (Foucalt's original in Paris is 67 meters long). Now scientists at Carnegie Mellon University have another solution (abstract). They've created a motor that drives a pendulum in a way that always cancels out the precession. That means the effect of Earth's rotation can be seen on much shorter pendulums such as the 3-meter pendulum on which they've tested their motor. That's just the start though. They say there is no limit to how short the new generation of Foucault Pendulums can be, and even talk about the possibility of tabletop devices." -
New Paper Offers Additional Reasoning for Fermi's Paradox
KentuckyFC writes "If the universe is teeming with advanced civilizations capable of communicating over interstellar distances, then surely we ought to have seen them by now. That's the gist of a paradoxical line of reasoning put forward by the physicist Enrico Fermi in 1950. The so-called Fermi Paradox has haunted SETI researchers ever since. Not least because if the number of intelligent civilizations capable of communication in our galaxy is greater than 1, then we should eventually hear from them. Now one astrophysicist says this thinking fails to take into account the limit to how far a signal from ET can travel before it becomes too faint to hear. Factor that in and everything changes. Assuming the average communicating civilization has a lifetime of 1,000 years, ten times longer than Earth has been broadcasting, and has a signal horizon of 1,000 light-years, you need a minimum of over 300 communicating civilizations in the Milky Way to ensure that you'll see one of them. Any less than that and the chances are that they'll live out their days entirely ignorant of each other's existence. Paradox solved, right?" -
New Paper Offers Additional Reasoning for Fermi's Paradox
KentuckyFC writes "If the universe is teeming with advanced civilizations capable of communicating over interstellar distances, then surely we ought to have seen them by now. That's the gist of a paradoxical line of reasoning put forward by the physicist Enrico Fermi in 1950. The so-called Fermi Paradox has haunted SETI researchers ever since. Not least because if the number of intelligent civilizations capable of communication in our galaxy is greater than 1, then we should eventually hear from them. Now one astrophysicist says this thinking fails to take into account the limit to how far a signal from ET can travel before it becomes too faint to hear. Factor that in and everything changes. Assuming the average communicating civilization has a lifetime of 1,000 years, ten times longer than Earth has been broadcasting, and has a signal horizon of 1,000 light-years, you need a minimum of over 300 communicating civilizations in the Milky Way to ensure that you'll see one of them. Any less than that and the chances are that they'll live out their days entirely ignorant of each other's existence. Paradox solved, right?" -
Miscalculation Invalidates LHC Safety Assurances
KentuckyFC writes "In a truly frightening study, physicists at the University of Oxford have identified a massive miscalculation that makes the LHC safety assurances more or less invalid (abstract). The focus of their work is not the safety of particle accelerators per se but the chances of any particular scientific argument being wrong. 'If the probability estimate given by an argument is dwarfed by the chance that the argument itself is flawed, then the estimate is suspect,' say the team. That has serious implications for the LHC, which some people worry could generate black holes that will swallow the planet. Nobody at CERN has put a figure on the chances of the LHC destroying the planet. One study simply said: 'there is no risk of any significance whatsoever from such black holes.' The danger is that this thinking could be entirely flawed, but what are the chances of this? The Oxford team say that roughly one in a thousand scientific papers have to be withdrawn because of errors but generously suppose that in particle physics, the rate is one in 10,000." -
Miscalculation Invalidates LHC Safety Assurances
KentuckyFC writes "In a truly frightening study, physicists at the University of Oxford have identified a massive miscalculation that makes the LHC safety assurances more or less invalid (abstract). The focus of their work is not the safety of particle accelerators per se but the chances of any particular scientific argument being wrong. 'If the probability estimate given by an argument is dwarfed by the chance that the argument itself is flawed, then the estimate is suspect,' say the team. That has serious implications for the LHC, which some people worry could generate black holes that will swallow the planet. Nobody at CERN has put a figure on the chances of the LHC destroying the planet. One study simply said: 'there is no risk of any significance whatsoever from such black holes.' The danger is that this thinking could be entirely flawed, but what are the chances of this? The Oxford team say that roughly one in a thousand scientific papers have to be withdrawn because of errors but generously suppose that in particle physics, the rate is one in 10,000." -
Black Holes From the LHC Could Last For Minutes
KentuckyFC writes "There is absolutely, positively, definitely no chance of the LHC destroying the planet (or this way either) when it eventually switches on some time later this year. And yet a few niggling doubts are persuading some scientists to run through their figures again. One potential method of destruction is that the LHC will create tiny black holes that could swallow everything in their path, including the planet. Various scientists have said this will not happen because the black holes would decay before they could do any damage. But physicists who have re-run the calculations now say that the mini black holes produced by the LHC could last for seconds, possibly minutes. Of course, the real question is whether they decay faster than they can grow. The new calculations suggest that the decay mechanism should win over and that the catastrophic growth of a black hole from the LHC 'does not seem possible' (abstract). But shouldn't we require better assurance than that?" -
Black Holes From the LHC Could Last For Minutes
KentuckyFC writes "There is absolutely, positively, definitely no chance of the LHC destroying the planet (or this way either) when it eventually switches on some time later this year. And yet a few niggling doubts are persuading some scientists to run through their figures again. One potential method of destruction is that the LHC will create tiny black holes that could swallow everything in their path, including the planet. Various scientists have said this will not happen because the black holes would decay before they could do any damage. But physicists who have re-run the calculations now say that the mini black holes produced by the LHC could last for seconds, possibly minutes. Of course, the real question is whether they decay faster than they can grow. The new calculations suggest that the decay mechanism should win over and that the catastrophic growth of a black hole from the LHC 'does not seem possible' (abstract). But shouldn't we require better assurance than that?" -
Google's PageRank Predicts Nobel Prize Winners
KentuckyFC writes "The pattern of citations between scientific papers forms a network that has remarkable similarities to the network formed by the web. So why not use Google's PageRank, the world's most effective search algorithm to rank these papers in the same way it ranks websites? That's exactly what a couple of US researchers have done for physics papers published by the American Physical Society since 1893 (abstract). The results make interesting reading because almost all of the top ten papers resulted in (or were linked to) Nobel Prizes for their authors. Which means that studying the up-and-coming entries on the list ought to be a good way of predicting future winners. Better get your bets in before the bookies get wind of this." -
Google's PageRank Predicts Nobel Prize Winners
KentuckyFC writes "The pattern of citations between scientific papers forms a network that has remarkable similarities to the network formed by the web. So why not use Google's PageRank, the world's most effective search algorithm to rank these papers in the same way it ranks websites? That's exactly what a couple of US researchers have done for physics papers published by the American Physical Society since 1893 (abstract). The results make interesting reading because almost all of the top ten papers resulted in (or were linked to) Nobel Prizes for their authors. Which means that studying the up-and-coming entries on the list ought to be a good way of predicting future winners. Better get your bets in before the bookies get wind of this." -
Chu's Final Breakthrough Before Taking Office
KentuckyFC writes "While preparing for the job of US Secretary of Energy in the incoming Obama administration (and being director of the Lawrence Berkeley National Laboratory and a Nobel Prize winner to boot), Steven Chu has somehow found time to make a major breakthrough in the world of atom interferometry. One measure of an interferometer's sensitivity is the area that its arms enclose. Chu and colleagues have found a way to increase this area by a factor of 2,500 by canceling out the noise introduced by lasers, which work as beam splitters sending atoms down different arms (abstract). One thing this makes possible is the use of different types of atoms in the same interferometer, allowing a new generation of tests of the equivalence principle. (This is the assumption that the m in F=ma and the m's in F= Gm1.m2/r^2 are the same thing). Let's hope he's got equally impressive breakthroughs planned for his encore as US Secretary of Energy." -
Chu's Final Breakthrough Before Taking Office
KentuckyFC writes "While preparing for the job of US Secretary of Energy in the incoming Obama administration (and being director of the Lawrence Berkeley National Laboratory and a Nobel Prize winner to boot), Steven Chu has somehow found time to make a major breakthrough in the world of atom interferometry. One measure of an interferometer's sensitivity is the area that its arms enclose. Chu and colleagues have found a way to increase this area by a factor of 2,500 by canceling out the noise introduced by lasers, which work as beam splitters sending atoms down different arms (abstract). One thing this makes possible is the use of different types of atoms in the same interferometer, allowing a new generation of tests of the equivalence principle. (This is the assumption that the m in F=ma and the m's in F= Gm1.m2/r^2 are the same thing). Let's hope he's got equally impressive breakthroughs planned for his encore as US Secretary of Energy." -
New Memristor Makes Low-Cost, High-Density Memory
KentuckyFC writes "A group of electronics engineers have discovered that a thin layer of vanadium oxide acts as a memristor, the fourth basic component of circuits after resistors, capacitors, and inductors that was discovered last year. At a critical temperature, a current passing through the layer causes it to change from an insulating state to a metal-like state, thereby changing its resistance (abstract). The effect lasts many hours — which is what makes the layer a memristor (a resistor with memory). The team says this could be scaled up to make resistive random access memory, or RRAM, at very low cost, from little more than layers of vanadium oxide." -
New Memristor Makes Low-Cost, High-Density Memory
KentuckyFC writes "A group of electronics engineers have discovered that a thin layer of vanadium oxide acts as a memristor, the fourth basic component of circuits after resistors, capacitors, and inductors that was discovered last year. At a critical temperature, a current passing through the layer causes it to change from an insulating state to a metal-like state, thereby changing its resistance (abstract). The effect lasts many hours — which is what makes the layer a memristor (a resistor with memory). The team says this could be scaled up to make resistive random access memory, or RRAM, at very low cost, from little more than layers of vanadium oxide." -
Graphene Transistors Clocked At 26GHz
KentuckyFC writes "A team at IBM has built the first high quality graphene transistors and clocked them running at 26 GHz . That doesn't quite knock silicon off its perch. The fastest silicon transistors are an order of magnitude faster than that but the record is held by indium phosphide transistors which have topped 1000 GHz. But it's not bad for a new kid on the block. It took silicon 40 years to get this far. By contrast, the first graphene transistor was built only last year. IBM says 'the work represents a significant step towards the realization of graphene-based electronics.' (Abstract)." -
Graphene Transistors Clocked At 26GHz
KentuckyFC writes "A team at IBM has built the first high quality graphene transistors and clocked them running at 26 GHz . That doesn't quite knock silicon off its perch. The fastest silicon transistors are an order of magnitude faster than that but the record is held by indium phosphide transistors which have topped 1000 GHz. But it's not bad for a new kid on the block. It took silicon 40 years to get this far. By contrast, the first graphene transistor was built only last year. IBM says 'the work represents a significant step towards the realization of graphene-based electronics.' (Abstract)." -
Quantum Test Found For Mathematical Undecidability
KentuckyFC writes "Philosophers have long wondered at the profound link between mathematics and physics, but how deep does this connection go? Pretty deep according to the results of a quantum experiment exploring the nature of mathematical undecidability. Here's how: any logical system must be based on axioms, which are propositions that are defined to be true. A proposition is logically independent from these axioms if it can neither be proved nor disproved from them; mathematicians say it is undecidable. In the experiment, researchers encoded a set of axioms as quantum states. A particular measurement on this system can then be thought of as a proposition which, if undecidable, yields a random result — which is what they found. 'This sheds new light on the (mathematical) origin of quantum randomness in these measurements,' say the researchers (abstract)." -
Quantum Test Found For Mathematical Undecidability
KentuckyFC writes "Philosophers have long wondered at the profound link between mathematics and physics, but how deep does this connection go? Pretty deep according to the results of a quantum experiment exploring the nature of mathematical undecidability. Here's how: any logical system must be based on axioms, which are propositions that are defined to be true. A proposition is logically independent from these axioms if it can neither be proved nor disproved from them; mathematicians say it is undecidable. In the experiment, researchers encoded a set of axioms as quantum states. A particular measurement on this system can then be thought of as a proposition which, if undecidable, yields a random result — which is what they found. 'This sheds new light on the (mathematical) origin of quantum randomness in these measurements,' say the researchers (abstract)." -
Quantum Cloaking Makes Molecules Invisible
KentuckyFC writes "An international team of physicists has applied the ideas of cloaking to the quantum world and worked out how to hide quantum objects such as molecules. In the quantum world, seeing is equivalent to detecting a quantum object. In the case of molecules, that means looking for the terahertz radiation they produce when they vibrate (abstract). By designing a 'quantum corral,' an elliptical nanostructures that absorbs terahertz waves at a precise frequency, the team says it is possible to hide molecules that emit at exactly that frequency. They say their quantum corral would be ideally suited to detecting molecules of specific species while ignoring others. And that may mean a new generation of molecular detectors on the horizon." -
Quantum Cloaking Makes Molecules Invisible
KentuckyFC writes "An international team of physicists has applied the ideas of cloaking to the quantum world and worked out how to hide quantum objects such as molecules. In the quantum world, seeing is equivalent to detecting a quantum object. In the case of molecules, that means looking for the terahertz radiation they produce when they vibrate (abstract). By designing a 'quantum corral,' an elliptical nanostructures that absorbs terahertz waves at a precise frequency, the team says it is possible to hide molecules that emit at exactly that frequency. They say their quantum corral would be ideally suited to detecting molecules of specific species while ignoring others. And that may mean a new generation of molecular detectors on the horizon." -
How To Cloak Objects At a Distance
KentuckyFC writes "All invisibility cloaks to date work by hiding an object embedded inside them. Now a group of physicists have worked out how to remotely cloak objects that sit outside a cloaking material. The trick is to make the cloaking material with optical properties that are exactly complementary to the space outside them. Complementary means that the material reverses the effect the space has on a plane wave of light passing through it. To an observer this space would appear to vanish. The scientists say that to cloak an object sitting outside the cloaking material, first measure its optical properties and then embed a "complementary image" of the object within the cloak. So a plane wave is first distorted by the object but then restored to a plane by the complementary image of the object within the cloak (abstract). An observer sees nothing. This method has another benefit. Objects hidden in conventional cloaks are blinded because no light enters the cloaked region. But objects that are remotely cloaked like this should still be able to see their surroundings." -
How To Cloak Objects At a Distance
KentuckyFC writes "All invisibility cloaks to date work by hiding an object embedded inside them. Now a group of physicists have worked out how to remotely cloak objects that sit outside a cloaking material. The trick is to make the cloaking material with optical properties that are exactly complementary to the space outside them. Complementary means that the material reverses the effect the space has on a plane wave of light passing through it. To an observer this space would appear to vanish. The scientists say that to cloak an object sitting outside the cloaking material, first measure its optical properties and then embed a "complementary image" of the object within the cloak. So a plane wave is first distorted by the object but then restored to a plane by the complementary image of the object within the cloak (abstract). An observer sees nothing. This method has another benefit. Objects hidden in conventional cloaks are blinded because no light enters the cloaked region. But objects that are remotely cloaked like this should still be able to see their surroundings." -
Researchers Calculate Capacity of a Steganographic Channel
KentuckyFC writes "Steganography is the art of hiding a message in such a way that only the sender and receiver realize it is there. (By contrast, cryptography disguises the content of a message but makes no attempt to hide it.) The central problem for steganographers is how much data can be hidden without being detected. But the complexity of this problem has meant it has been largely ignored. Now two computer scientists (one working for Google) have made a major theoretical breakthrough by tackling the problem in the same way that the electrical engineer Claude Shannon calculated the capacity of an ordinary communications channel in the 1940s. In Shannon's theory, a transmission is considered successful if the decoder properly determines which message the encoder has sent. In the stego-channel, a transmission is successful if the decoder properly determines the sent message without anybody else detecting its presence (abstract). Studying a stego-channel in this way leads to some counter-intuitive results: for example, in certain circumstances, doubling the number of algorithms looking for hidden data can increase the capacity of the steganographic channel" -
Researchers Calculate Capacity of a Steganographic Channel
KentuckyFC writes "Steganography is the art of hiding a message in such a way that only the sender and receiver realize it is there. (By contrast, cryptography disguises the content of a message but makes no attempt to hide it.) The central problem for steganographers is how much data can be hidden without being detected. But the complexity of this problem has meant it has been largely ignored. Now two computer scientists (one working for Google) have made a major theoretical breakthrough by tackling the problem in the same way that the electrical engineer Claude Shannon calculated the capacity of an ordinary communications channel in the 1940s. In Shannon's theory, a transmission is considered successful if the decoder properly determines which message the encoder has sent. In the stego-channel, a transmission is successful if the decoder properly determines the sent message without anybody else detecting its presence (abstract). Studying a stego-channel in this way leads to some counter-intuitive results: for example, in certain circumstances, doubling the number of algorithms looking for hidden data can increase the capacity of the steganographic channel" -
Number of ET Civilizations In Our Galaxy Is 37,964
KentuckyFC writes "The famous Drake equation calculates the number of advanced civilizations in our galaxy right now. But the result is hugely sensitive to the assumptions you make about factors such as the number of habitable planets that orbit a host star, how many of these actually develop life and what fraction of these go on to become intelligent etc. Disagreements about these figures leads to estimates for the number of advanced civilizations ranging from 10^-5 to 10^6. Now an astronomer in Scotland has worked out how to make the calculations more precise so that different theories about the origin of planets, life and civilizations can be compared. His calculations say that the rare-life hypothesis predicts only 361 advanced civilizations in the Milky Way now. However, the so-called tortoise and hare hypothesis predicts 31,573 and the theory of panspermia says that there ought to be 37,964 extraterrestrial civilizations more advanced than our own in the Milky Way." -
Number of ET Civilizations In Our Galaxy Is 37,964
KentuckyFC writes "The famous Drake equation calculates the number of advanced civilizations in our galaxy right now. But the result is hugely sensitive to the assumptions you make about factors such as the number of habitable planets that orbit a host star, how many of these actually develop life and what fraction of these go on to become intelligent etc. Disagreements about these figures leads to estimates for the number of advanced civilizations ranging from 10^-5 to 10^6. Now an astronomer in Scotland has worked out how to make the calculations more precise so that different theories about the origin of planets, life and civilizations can be compared. His calculations say that the rare-life hypothesis predicts only 361 advanced civilizations in the Milky Way now. However, the so-called tortoise and hare hypothesis predicts 31,573 and the theory of panspermia says that there ought to be 37,964 extraterrestrial civilizations more advanced than our own in the Milky Way." -
Another Way the LHC Could Self-Destruct
KentuckyFC writes "Just when you thought it was safe to switch on the LHC (though it won't be for a while yet), another nightmare scenario has emerged that some critics worry could cause the particle accelerator to explode. The culprit this time is not an Earth-swallowing black hole but a 'Bose supernova' in the accelerator's superfluid helium bath. Physicists have been playing with Bose Einstein Condensate (BECs) for over 10 years now. But in 2001, one group discovered that placing them in a powerful magnetic field could cause the attractive forces between atoms to become repulsive. That caused their BEC to explode in a Bose supernova — which they called a 'Bosenova,' a name that fortunately did not catch on. This was little more than a curiosity when only a microscopic blob of cold matter was involved. But superfluid liquid helium is also BEC. And physicists have suddenly remembered that the LHC is swimming in 700,000 liters of the stuff while being zapped by some of the most powerful magnetic fields on the planet. So is the LHC a Bose supernova waiting to go off? Not according to the CERN theory division, which has published its calculations that show the LHC is safe (abstract). They also point out that no other superfluid helium handling facility has mysteriously blown itself to pieces." -
Another Way the LHC Could Self-Destruct
KentuckyFC writes "Just when you thought it was safe to switch on the LHC (though it won't be for a while yet), another nightmare scenario has emerged that some critics worry could cause the particle accelerator to explode. The culprit this time is not an Earth-swallowing black hole but a 'Bose supernova' in the accelerator's superfluid helium bath. Physicists have been playing with Bose Einstein Condensate (BECs) for over 10 years now. But in 2001, one group discovered that placing them in a powerful magnetic field could cause the attractive forces between atoms to become repulsive. That caused their BEC to explode in a Bose supernova — which they called a 'Bosenova,' a name that fortunately did not catch on. This was little more than a curiosity when only a microscopic blob of cold matter was involved. But superfluid liquid helium is also BEC. And physicists have suddenly remembered that the LHC is swimming in 700,000 liters of the stuff while being zapped by some of the most powerful magnetic fields on the planet. So is the LHC a Bose supernova waiting to go off? Not according to the CERN theory division, which has published its calculations that show the LHC is safe (abstract). They also point out that no other superfluid helium handling facility has mysteriously blown itself to pieces." -
Space Observatory May Have Found Dark Matter
KentuckyFC writes to mention that new data from the orbiting observatory PAMELA may shed some additional light on the question of dark matter. Still only a preliminary announcement, the new findings apparently support the "Minimal Dark Matter" model, in which a particle called a "Wino" is responsible. -
Space Observatory May Have Found Dark Matter
KentuckyFC writes to mention that new data from the orbiting observatory PAMELA may shed some additional light on the question of dark matter. Still only a preliminary announcement, the new findings apparently support the "Minimal Dark Matter" model, in which a particle called a "Wino" is responsible. -
Nuclear Decay May Vary With Earth-Sun Distance
KentuckyFC writes "We've long thought that nuclear decay rates are constant regardless of ambient conditions (except in a few special cases where beta decay can be influenced by powerful electric fields). So that makes it hard to explain two puzzling experiments from the 1980s that found periodic variations over many years in the decay rates of silicon-32 and radium-226. Now a new analysis of the raw data says that changes in the decay rate are synchronized with each other and with Earth's distance from the sun. The physicists behind this work offer two theories to explain why this might be happening (abstract). First, some theorists think the sun produces a field that changes the value of the fine structure constant on Earth as its distance from the sun varies. That would certainly affect the rate of nuclear decay. Another idea is that the effect is caused by some kind of interaction with the neutrino flux from the sun's interior which also varies with distance. Take your pick. What makes the whole story even more intriguing is that for years physicists have disagreed over the decay rates of several isotopes such as titanium-44, silicon-32, and cesium-137. Perhaps they took their data at different times of the year?" -
Nuclear Decay May Vary With Earth-Sun Distance
KentuckyFC writes "We've long thought that nuclear decay rates are constant regardless of ambient conditions (except in a few special cases where beta decay can be influenced by powerful electric fields). So that makes it hard to explain two puzzling experiments from the 1980s that found periodic variations over many years in the decay rates of silicon-32 and radium-226. Now a new analysis of the raw data says that changes in the decay rate are synchronized with each other and with Earth's distance from the sun. The physicists behind this work offer two theories to explain why this might be happening (abstract). First, some theorists think the sun produces a field that changes the value of the fine structure constant on Earth as its distance from the sun varies. That would certainly affect the rate of nuclear decay. Another idea is that the effect is caused by some kind of interaction with the neutrino flux from the sun's interior which also varies with distance. Take your pick. What makes the whole story even more intriguing is that for years physicists have disagreed over the decay rates of several isotopes such as titanium-44, silicon-32, and cesium-137. Perhaps they took their data at different times of the year?" -
Solar Systems Like Ours Are Likely To Be Rare
KentuckyFC writes "Astronomers have discovered some 250 planetary systems beyond our own, many of them with curious properties. In particular, our theories of planet formation are challenged by 'hot Jupiters,' gas giants that orbit close to their parent stars. Current thinking is that gas giants can only form far away from stars because gas and dust simply gets blown away from the inner regions. Now astronomers have used computer simulations of the way planetary systems form to understand what is going on (abstract). It looks as if gas giants often form a long way from stars and then migrate inwards. That has implications for us: a migrating gas giant sweeps away all in its path, including rocky planets in the habitable zone. And that means that solar systems like ours are likely to be rare." -
Solar Systems Like Ours Are Likely To Be Rare
KentuckyFC writes "Astronomers have discovered some 250 planetary systems beyond our own, many of them with curious properties. In particular, our theories of planet formation are challenged by 'hot Jupiters,' gas giants that orbit close to their parent stars. Current thinking is that gas giants can only form far away from stars because gas and dust simply gets blown away from the inner regions. Now astronomers have used computer simulations of the way planetary systems form to understand what is going on (abstract). It looks as if gas giants often form a long way from stars and then migrate inwards. That has implications for us: a migrating gas giant sweeps away all in its path, including rocky planets in the habitable zone. And that means that solar systems like ours are likely to be rare." -
Theorists Make Quantum Communications Breakthrough
KentuckyFC writes "One of the cornerstones of modern physics is Claude Shannon's theory of communication, which he published in 1948. If you've ever made a phone call, watched TV, or used a computer, you've got Shannon to thank for describing how information can be moved from one place in the universe to another using an idea called the channel capacity. But nobody has been able to develop a quantum version of this theory. So physicists have no idea how much quantum information can be sent from one point to another. Now two American physicists have made an important breakthrough by proving that two quantum channels with zero capacity can carry information when used together. That's interesting because it indicates that physicists may have been barking up the wrong tree with this problem: it implies that the quantum capacity of a channel does not uniquely specify its ability for transmitting quantum information (abstract). And that could be the idea that breaks the logjam in this area." -
Theorists Make Quantum Communications Breakthrough
KentuckyFC writes "One of the cornerstones of modern physics is Claude Shannon's theory of communication, which he published in 1948. If you've ever made a phone call, watched TV, or used a computer, you've got Shannon to thank for describing how information can be moved from one place in the universe to another using an idea called the channel capacity. But nobody has been able to develop a quantum version of this theory. So physicists have no idea how much quantum information can be sent from one point to another. Now two American physicists have made an important breakthrough by proving that two quantum channels with zero capacity can carry information when used together. That's interesting because it indicates that physicists may have been barking up the wrong tree with this problem: it implies that the quantum capacity of a channel does not uniquely specify its ability for transmitting quantum information (abstract). And that could be the idea that breaks the logjam in this area." -
NAO Humanoid Robot Set To Hit the Market
KentuckyFC writes "Earlier this year, Paris-based Aldebaran-Robotics picked up $8 million in venture capital funding to help commercialize its NAO humanoid robot. The target market for this device is research labs working on the next generation of robotic hardware and software. Today, the company has posted a detailed spec of NAO on the arXiv saying that it expects the robot to cost about $15,000 each. That's cheap compared to other humanoids. Fuitsu's HOAP humanoids cost $50,000 each and various estimates price Honda's Asimo at $1 million per bot, although they are not for sale. Aldebaran-Robotics says that NAO's cost should come down to about $6,000 as production ramps up."