A pulse of light can be stopped, transported, and restarted again using a cloud of super-cold atoms, US researchers have shown. The technique could ultimately be used for advanced computing devices or gravity detectors.The experiments demonstrate physicists’ increasing ability to manipulate light. Being able to control it in this way could be useful for optical or quantum computers, the team suggests.
“The first time I read this paper, I didn’t believe it,” says Michael Fleischhauer, a theoretical physicist at the University of Kaiserslautern in Germany. “Even though theory tells us it should be possible, actually doing it is something else.”
Posts Tagged ‘science’
True in Practice, but is it true in theory?
Wednesday, February 7th, 2007One Step closer to Cyborgs
Friday, February 2nd, 2007A prosthetic arm that moves and feels like the real thing is now a step closer thanks to a new surgical technique which allows the owner to intuitively control her limb and regain her sense of touch.Surgeons working on a female amputee in Chicago, US, have re-routed the ends of the motor nerves – which once controlled her arm’s movement – into the muscles in her chest and side. And the ends of the sensory nerves, which fed signals responding to heat and touch from her now-amputated arm to her brain, have been transferred to the skin on her chest.
Making light of Information Storage
Sunday, January 21st, 2007Researchers at the University of Rochester have made an optics breakthrough that allows them to encode an entire image’s worth of data into a photon, slow the image down for storage, and then retrieve the image intact.While the initial test image consists of only a few hundred pixels, a tremendous amount of information can be stored with the new technique.
The image, a ‘UR’ for the University of Rochester, was made using a single pulse of light and the team can fit as many as a hundred of these pulses at once into a tiny, four-inch cell. Squeezing that much information into so small a space and retrieving it intact opens the door to optical buffering—storing information as light.
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“The parallel amount of information John has sent all at once in an image is enormous in comparison to what anyone else has done before,” says Alan Willner, professor of electrical engineering at the University of Southern California and president of the IEEE Lasers and Optical Society. “To do that and be able to maintain the integrity of the signal—it’s a wonderful achievement.”
Howell has so far been able to delay light pulses 100 nanoseconds and compress them to 1 percent of their original length. He is now working toward delaying dozens of pulses for as long as several milliseconds, and as many as 10,000 pulses for up to a nanosecond.
“Now I want to see if we can delay something almost permanently, even at the single photon level,” says Howell. “If we can do that, we’re looking at storing incredible amounts of information in just a few photons.”
The Stuff Daydreams are made of
Friday, January 19th, 2007Daydreaming seems to be the default setting of the human mind and certain brain regions are devoted to it, U.S. researchers reported on Friday.When people are given a specific task to do, they focus on that task but then other brain regions get busy during down time, the researchers report in Friday’s issue of the journal Science.
‘There is this network of regions that always seems to be active when you don’t give people something to do,’ psychologist Malia Mason of Harvard Medical School and Massachusetts General Hospital said in a telephone interview.
When Mason asked people what was happening during this down time, the answer was clear.
‘It’s daydreaming,’ she said. ‘But I find that the vast majority of time, people aren’t having fanciful thoughts. People are thinking about what they have to do later today.’
Her team has chosen to call it stimulus-independent thought or mind wandering.
The Evolution of Environmentalism
Wednesday, January 17th, 2007Laying down their swords over how we came to exist, leaders from scientific and evangelical communities in the US joined forces today in an unprecedented effort to protect what we have.Speaking at a press conference in Washington DC, members of the newly formed group expressed concerns about planetary threats caused by humans including climate change, habitat destruction, pollution, and species extinction.
The group issued an “urgent call to action” signed by 28 coalition members including university professors, federal biologists, directors of conservation organisations, seminary officials, evangelical organisation leaders, and ‘megachurch’ pastors.
The statement, sent to President George W Bush and Congressional leaders urges fundamental change in public policies and states that “business as usual cannot continue yet one more day”.
Deep reverence
The group was spearheaded by leaders of Harvard University’s Center for Health and the Global Environment in Boston, Massachusetts, and the National Association of Evangelicals (NAE), an umbrella group that encompasses 45,000 churches, and represents 40% of the Republican Party’s supporters. Members from both organisations called for a united front on environmental issues.
“We share a very deep reverence for life on earth, whether that life was created by God or evolved over billions of years, it exists, is sacred to all of us, and is being endangered by human activity,” said Eric Chivian, Director of Harvard’s Center for Health and the Global Environment.
“It doesn’t matter if we are liberals or conservatives, Darwinists or Creationists, we are all under the same atmosphere and drink the same water and will do everything we can to work together to solve these problems.”
Vision leads to language
Saturday, January 13th, 2007It has been repeatedly demonstrated that all great apes, including humans, follow the gaze direction of others. But in previous studies the head and eyes were always pointed in the same direction. Only when we made the head and eyes point in different directions did we find a species difference: humans are sensitive to the direction of the eyes specifically in a way that our nearest primate relatives are not. This is the first demonstration of an actual behavioral function for humans’ uniquely visible eyes.Why might it have been advantageous for some early humans to advertise their eye direction in a way that enabled others to determine what they were looking at more easily? One possible answer, what we have called the cooperative eye hypothesis, is that especially visible eyes made it easier to coordinate close-range collaborative activities in which discerning where the other was looking and perhaps what she was planning, benefited both participants.
If we are gathering berries to share, with one of us pulling down a branch and the other harvesting the fruit, it would be useful — especially before language evolved — for us to coordinate our activities and communicate our plans, using our eyes and perhaps other visually based gestures.
Infant research, too, suggests that coordinating visual attention may have provided the foundation for the evolution of human language. Babies begin to acquire language through joint activities with others, in which both parties are focused on the same object or task. That’s the best time for an infant to learn the word for the object or activity in question.
First Impressions
Tuesday, January 9th, 2007People have eagle eyes when they have just enough time to make a snap decision, a new study suggests. Subjects asked to pick out a single reversed cross on a screen of nearly 660 such symbols did better when they had only a fraction of a second to make a decision.The study supports the idea that we should trust our initial instincts in certain circumstances, say the researchers. They add that the findings demonstrate how higher-level thinking can sometimes steer us away from the right answer.
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The researchers say there is a biological basis for these findings. An image picked up by the eyes first gets processed by a region at the back of the brain known as the primary visual cortex.
This area of the brain is thought to be involved in subconscious processing. The information then travels from this visual processing area to both the parietal region – which recognises shapes – and the decision-making frontal cortex.
Invisible Structures
Monday, January 8th, 2007The distribution of dark matter has been mapped in 3D for the first time, revealing how the mysterious substance has evolved over the lifetime of the universe. The results confirm that dark matter provided the scaffolding that allowed ordinary matter to clump together to form galaxies and clusters of galaxies.Dark matter is an invisible substance that betrays its presence through the gravitational tug it exerts on ordinary matter. It is six times more abundant than ordinary matter and is thought to have seeded the first distinct structures in the universe, which began as a very uniform soup of matter.
Computer simulations suggest that the formation of dark matter clumps attracted surrounding gas, which then condensed to form galaxies and galaxy clusters. But this dark matter clumping process had never been confirmed observationally.
Now, astronomers have mapped the changing distribution of both dark matter and ordinary matter over time. Nick Scoville, of Caltech in Pasadena, US, led the Cosmic Evolution Survey (COSMOS), which combined data from three of the world’s leading observatories to produce the map.
The key to determining the dark matter distribution is an effect called gravitational lensing, by which light rays from a distant object such as a galaxy are bent by the gravity of an intervening concentration of matter. Although dark matter cannot be seen directly, its presence can be inferred by the way its gravity distorts the images of galaxies behind it.
Reborn as Star-Beings
Friday, January 5th, 2007A dying galaxy near the Milky Way appears to be sowing the seeds of its own rebirth and may hold the secret to the apparent reincarnation of several other similar galaxies. The phoenix-like process may also help resolve a longstanding mystery about missing dark matter clumps near the Milky Way.About 20 small galaxies are known to exist around our galaxy. Most fall into two main categories: dwarf spheroidals, which are dead because they lack the gas needed for making new stars, and dwarf irregulars, which have plenty of gas and show signs of ongoing star formation.
Some astronomers have suggested that dwarf galaxies can switch back and forth between the two types by dying and being reborn repeatedly. In the dwarf irregular phase, abundant gas fuels rapid star formation. But the newly formed stars then sterilise the galaxy when some of them explode as supernovae and blow away its gas. The galaxy’s gravity later pulls the gas back in to fuel a new cycle of star formation.
Now, new observations have bolstered that idea by showing that a gas cloud expelled from one such galaxy is moving slowly enough that it will eventually revive the galaxy by falling back into it and triggering new star formation.
Envisioning the Future
Tuesday, January 2nd, 2007Human memory, the ability to recall vivid mental images of past experiences, has been studied extensively for more than a hundred years. But until recently, there’s been surprisingly little research into cognitive processes underlying another form of mental time travel — the ability to clearly imagine or ‘see’ oneself participating in a future event.Now, researchers from Washington University in St. Louis have used advanced brain imaging techniques to show that remembering the past and envisioning the future may go hand-in-hand, with each process sparking strikingly similar patterns of activity within precisely the same broad network of brain regions.
‘In our daily lives, we probably spend more time envisioning what we’re going to do tomorrow or later on in the day than we do remembering, but not much is known about how we go about forming these mental images of the future,’ says Karl Szpunar, lead author of the study and a psychology doctoral student in Arts & Sciences at Washington University.
‘Our findings provide compelling support for the idea that memory and future thought are highly interrelated and help explain why future thought may be impossible without memories.’
