How could bees of little brain come up with anything as complex as a dance language? The answer could lie not in biology but in six-dimensional math and the bizarre world of quantum mechanics.
Honeybees don't have much in the way of brains. Their inch-long bodies hold at most a few million neurons. Yet with such meager mental machinery honeybees sustain one of the most intricate and explicit languages in the animal kingdom. In the darkness of the hive, bees manage to communicate the precise direction and distance of a newfound food source, and they do it all in the choreography of a dance. Scientists have known of the bee's dance language for more than 70 years, and they have assembled a remarkably complete dictionary of its terms, but one fundamental question has stubbornly remained unanswered: How do they do it? How do these simple animals encode so much detailed information in such a varied language? Honeybees may not have much brain, by they do have a secret.
This secret has vexed Barbara Shipman, a mathematician at the University of Rochester, ever since she was a child. "I grew up thinking about bees," she says. "My dad worked for the Department of Agriculture as a bee researcher. My brothers and I would stop at his office, and sometimes he would how show us the bees. I remember my father telling me about the honeybee's dance when I was about nine years old. And in high school I wrote a paper on the medicinal benefits of honey." Her father kept his books on honeybees on a shelf in her room. "I'm not sure why," she says. "It may have just been a convenient space. I remember looking at a lot of these books, especially the one by Karl von Frisch."
Von Frisch's Dance Language and Orientation of Bees was some four decades in the making. By the time his papers on the bee dance were collected and published in 1965, there was scarcely an entomologist in the world who hadn't been both intrigued and frustrated by his findings. Intrigued because the phenomenon Von Frisch described was so startlingly complex; frustrated because no one had a clue as to how bees managed the trick. Von Frisch had watched bees dancing on the vertical face of the honeycomb, analyzed the choreographic syntax, and articulated a vocabulary. When a bee finds a source of food, he realized, it returns to the hive and communicates the distance and direction of the food to the other worker bees, called recruits. On the honeycomb which Von Frisch referred to as the dance floor, the bee performs a "waggle dance," which in outline looks something like a coffee bean--two rounded arcs bisected by a central line. The bee starts by making a short straight run, waggling side to side and buzzing as it goes. Then it turns left (or right) and walks in a semicircle back to the starting point. The bee then repeats the short run down the middle, makes a semicircle to the opposite side, and returns once again to the starting point.
It is easy to see why this beautiful and mysterious phenomenon captured Shipman's young and mathematically inclined imagination. The bee's finely tuned choreography is a virtuoso performance of biologic information processing. The central "waggling" part of the dance is the most important. To convey the direction of a food source, the bee varies the angle the waggling run makes with an imaginary line running straight up and down. One of Von Frisch's most amazing discoveries involves this angle. If you draw a line connecting the beehive and the food source, and another line connecting the hive and the spot on the horizon just beneath the sun, the angle formed by the two lines is the same as the angle of the waggling run to the imaginary vertical line. The bees, it appears, are able to triangulate as well as a civil engineer.
Direction alone is not enough, of course--the bees must also tell their hive mates how far to go to get to the food. "The shape or geometry of the dance changes as the distance to the food source changes," Shipman explains. Move a pollen source closer to the hive and the coffee-bean shape of the waggle dance splits down the middle. "The dancer will perform two alternating waggling runs symmetric about, but diverging from, the center line. The closer the food source is to the hive, the greater the divergence between the two waggling runs."
If that sounds almost straightforward, what happens next certainly doesn't. Move the food source closer than some critical distance and the dance changes dramatically: the bee stops doing the waggle dance and switches into the "round dance." It runs in a small circle, reversing and going in the opposite direction after one or two turns or sometimes after only half a turn. There are a number of variations between species.
Von Frisch's work on the bee dance is impressive, but it is largely descriptive. He never explained why the bees use this peculiar vocabulary and not some other. Nor did he (or could he) explain how small-brained bees manage to encode so much information. "The dance of the honeybee is special among animal communication systems," says Shipman. "It conveys concise, quantitative information in an abstract, symbolic way. You have to wonder what makes the dance happen. Bees don't have enough intelligence to know what they are doing. How do they know the dance in the first place? Calling it instinct or some other word just substitutes one mystery for another."
Shipman entered college as a biochemistry major and even spent some time working in a biology lab studying the hemolymph--the "blood"--of honeybee larvae, but she quickly moved her interest in bees to the side. "During my freshman year," she says, aI became more attracted to the beauty and rigor of mathematics." She switched her major and eventually went on to graduate school and to a professorship at the University of Rochester. For several years it seemed as though she had wandered a long way from her childhood fascination.
Then, taking an unlikely route, she found herself once again confronting the mysteries of bees head-on. While working on her doctoral thesis, on an obscure type of mathematics known only to a small coterie of researchers well-versed in the minutiae of geometry, she stumbled across what just might be the key to the secrets of the bee's dance.
Shipman's work concerned a set of geometric problems associated with an esoteric mathematical concept known as a flag manifold. In the jargon of mathematics, manifold means "space." But don't let that deceptively simple definition lull you into a false sense of security. Mathematicians have as many kinds of manifolds as a French baker has bread. Some manifolds are flat, some are curved, some are twisted, some wrap back on themselves, some go on forever. "The surface of a sphere is a manifold," says Shipman. "So is the surface of a bagel--it's called a torus." The shape of a manifold determines what kinds of objects (curves, figures, surfaces) can "live" within its confines. Two different types of loops, for example, live in the surface of a torus--one wraps around the outside, the other goes through the middle, and there is no way to transform the first into the second without breaking the loop. In contrast, there is only one type of loop that lives on a sphere.
Mathematicians like to examine different manifolds the way antiques dealers browse through curio shops--always exploring, always looking for unusual characteristics that expand their understanding of numbers or geometry. The difficult part about exploring a manifold, however, is that mathematicians don't always confine them to the three dimensions of ordinary experience. A manifold can have two dimensions like the surface of a screen, three dimensions like the inside of an empty box, four dimensions like the space-time of our Einsteinian universe, or even ten or a hundred dimensions. The flag manifold (which got its name because some imaginative mathematician thought it had a "shape" like a flag on a pole) happens to have six dimensions, which means mathematicians can't visualize all the two-dimensional objects that can live there. That does not mean, though, that they cannot see the objects' shadows.
One of the more effective tricks for visualizing objects with more than three dimensions is to "project" or "map" them onto a space that has fewer dimensions (usually two or three). A topographic map, in which three-dimensional mountains get squashed onto a two-dimensional page, is a type of projection. Likewise, the shadow of your hand on the wall is a two-dimensional projection of your three-dimensional hand.
One day Shipman was busy projecting the six-dimensional residents of the flag manifold onto two dimensions. The particular technique she was using involved first making a two-dimensional outline of the six dimensions of the flag manifold. This is not as strange as it may sound. When you draw a circle, you are in effect making a two-dimensional outline of a three-dimensional sphere. As it turns out, if you make a two-dimensional outline of the six-dimensional flag manifold, you wind up with a hexagon. The bee's honeycomb, of course, is also made up of hexagons, but that is purely coincidental. However, Shipman soon discovered a more explicit connection. She found a group of objects in the flag manifold that, when projected onto a two-dimensional hexagon, formed curves that reminded her of the bee's recruitment dance. The more she explored the flag manifold, the more curves she found that precisely matched the ones in the recruitment dance. "I wasn't looking for a connection between bees and the flag manifold," she says. "I was just doing my research. The curves were nothing special in themselves, except that the dance patterns kept emerging." Delving more deeply into the flag manifold, Shipman dredged up a variable, which she called alpha, that allowed her to reproduce the entire bee dance in all its parts and variations. Alpha determines the shape of the curves in the 6-D flag manifold, which means it also controls how those curves look when they are projected onto the 2-D hexagon. Infinitely large values of alpha produce a single line that cuts the hexagon in half. Large' values of alpha produce two lines very close together. Decrease alpha and the lines splay out, joined at one end like a V. Continue to decrease alpha further and the lines form a wider and wider V until, at a certain value, they each hit a vertex of the hexagon. Then the curves change suddenly and dramatically. "When alpha reaches a critical value," explains Shipman, "the projected curves become straight line segments lying along opposing faces of the hexagon."
The smooth divergence of the splayed lines and their abrupt transition to discontinuous segments are critical--they link Shipman's curves to those parts of the recruitment dance that bees emphasize with their waggling and buzzing. "Biologists know that only certain parts of the dance convey information," she says. "In the waggle dance, it's the diverging waggling runs and not the return loops. In the circle dance it's short straight segments on the sides of the loops." Shipman's mathematics captures both of these characteristics, and the parameter alpha is the key. "If different species have different sensitivities to alpha, then they will change from the waggle dances to round dances when the food source is at different distances."
If Shipman is correct, her mathematical description of the recruitment dance would push bee studies to a new level. The discovery of mathematical structure is often the first and critical step in turning what is merely a cacophony of observations into a coherent physical explanation. In the sixteenth century Johannes Kepler joined astronomy's pantheon of greats by demonstrating that planetary orbits follow the simple geometric figure of the ellipse. By articulating the correct geometry traced by the heavenly bodies, Kepler ended two millennia of astronomical speculation as to the configuration of the heavens. Decades after Kepler died, Isaac Newton explained why planets follow elliptical orbits by filling in the all-important physics--gravity. With her flag manifold, Shipman is like a modern-day Kepler, offering, in her words, "everything in a single framework. I have found a mathematics that takes all the different forms of the dance and embraces them in a single coherent geometric structure."
Shipman is not, however, content to play Kepler. "You can look at this idea and say, `That's a nice geometric description of the dance, very pretty,' and leave it like that," she says. "But there is more to it. When you have a physical phenomenon like the honeybee dance, and it follows a mathematical structure, you have to ask what are the physical laws that are causing it to happen."
At this point Shipman departs from safely grounded scholarship and enters instead the airy realm of speculation. The flag manifold, she notes, in addition to providing mathematicians with pure joy, also happens to be useful to physicists in solving some of the mathematical problems that arise in dealing with quarks, tiny particles that are the building blocks of protons and neutrons. And she does not believe the manifold's presence both in the mathematics of quarks and in the dance of honeybees is a coincidence. Rather she suspects that the bees are somehow sensitive to what's going on in the quantum world of quarks, that quantum mechanics is as important to their perception of the world as sight, sound, and smell.
Say a bee flies around, finds a source of food, and heads straight back to the hive to tell its colleagues. How does it perceive where that food is? What notation can it use to remember? What teens can it use to translate that memory into directions for its fellow bees? One way, the way we big-brained humans would be most comfortable with, would be to use landmarks--fly ten yards toward the big rock, turn left, duck under the boughs of the pine tree, and see the flowers growing near the trunk. Another way, one that seems to be more in line with what bees actually do, would be to use physical characteristics that adequately identify the site, such as variations in Earth's magnetic field or in the polarization of the sun's light.
Researchers have in fact already established that the dance is sensitive to such properties. Experiments have documented, for example, that local variations in Earth's magnetic field alter the angle of the waggling runs. In the past, scientists have attributed this to the presence of magnetite, a magnetically active mineral, in the abdomen of bees. Shipman, however, along with many other researchers, believes there is more to it than little magnets in the bees' cells. But she tends not to have much professional company when she reveals what she thinks is responsible for the bees' response. "Ultimately magnetism is described by quantum fields," she says. "I think the physics of the bees' bodies, their physiology, must be constructed such that they're sensitive to quantum fields--that is, the bee perceives these fields through quantum mechanical interactions between the fields and the atoms in the membranes of certain cells."
What exactly does it mean to say that the bees interact with quantum fields? A quantum field is a sort of framework within which particles play out their existences. And, rather than assigning an electron to one position in space at one particular time, you instead talk about all the different places the electron could possibly be. You can loosely refer to this collection of all possible locations as a "field" smeared out across space and time. If you decide to check the electron's position by observing it, the interaction between your measuring device and the field makes the electron appear to be a single coherent object. In this sense, the observer is said to disturb the quantum mechanical nature of the electron.
There is some research to support the view that bees are sensitive to effects that occur only on a quantum-mechanical scale. One study exposed bees to short bursts of a high-intensity magnetic field and concluded that the bees' response could be better explained as a sensitivity to an effect known as nuclear magnetic resonance, or NMR, an acronym commonly associated with a medical imaging technique. NMR occurs when an electromagnetic wave impinges on the nuclei of atoms and flips their orientation. NMR is considered a quantum mechanical effect because it takes place only if each atom absorbs a particular size packet, or quantum, of electro-magnetic energy.
This research, however, doesn't address the issue of how bees turn these quantum-mechanical perceptions into an organized dance ritual. Shipman's mathematics does. To process quantum mechanical information and communicate it to others, the bee would not only have to possess equipment sensitive to the quantum-mechanical world; to come up with the appropriate recruitment dance, it would have to perform some kind of calculation similar to what Shipman did with her flag manifold. Assuming that the typical honey-bee is not quite intelligent enough to make the calculations, how does the bee come up with the flag manifold as an organizing principle for its dance? Shipman doesn't claim to have the answer, but she is quick to point out that the flag manifold is common both to the bee dance and to the geometry of quarks. Perhaps, she speculates, bees possess some ability to perceive not only light and magnetism but quarks as well.
The notion that bees can perceive quarks is hard enough for many physicists to swallow, but that's not even the half of it. Physicists have theorized that quarks are constantly popping up in the vacuum of empty space. This is possible because the vacuum is pervaded by something called the zero-point energy field--a quantum field in which on average no particles exist, but which can have local fluctuations that cause quarks to blink in and out of existence. Shipman believes that bees might sense these fleeting quarks, and use them--somehow--to create the complex and peculiar structure of their dance.
Now here's the rub. The flag manifold geometry is an abstraction. It is useful in describing quarks not as the single coherent objects that physicists can measure in the real world but as unobserved quantum fields. Once a physicist tries to detect a quark--by bombarding it with another particle in a high-energy accelerator--the flag manifold geometry is lost. If bees are using quarks as a script for their dance, they must be able to observe the quarks not as single coherent objects but as quantum fields. If Shipman's hunch is correct and bees are able to "touch" the quantum world of quarks without breaking it, not only would it shake up the field of biology, but physicists would be forced to reinterpret quantum mechanics as well.
Shipman is the first to admit that she is a long way from proving her hypothesis. "The mathematics implies that bees are doing something with quarks," she says. "I'm not saying they definitely are. I'm just throwing it out as a possibility." And when she publishes her research, probably sometime next year, no doubt many scientists will be turned off by her dragging quarks and quantum mechanics into the picture.
"The joining of mathematics and biology is a fascinating endeavor and is just getting under way," says William Faris, a mathematician at the University of Arizona. "Connecting quantum mechanics directly to biology is much more speculative. I frankly am skeptical that the bee dance is related to quantum mechanics. The mathematics she uses may be related to a completely different explanation of the bee dance. This is the universality of mathematics. To venture into quantum mechanics may be a distraction."
Shipman isn't the first scientist to go out on a limb trying to link biology to quantum mechanics. Physicist Roger Penrose of Oxford University has postulated that nerve cells have incredibly tiny tubes that serve as quantum mechanical detectors, and other physicists have expressed similar ideas, but they are by no means widely accepted.
It is risky for a young scientist to take on a radical theory. Championing an unproved or unpopular idea is a good way to put your academic career on permanent hold. "My thesis adviser was worried, too," says Shipman. "He was happy to know that I am beginning collaborations with biologists."
However, Shipman is too excited about the ideas to care about the risk. "To make discoveries that cross disciplines, someone has to start. I know there is always resistance to new ideas, especially if you are approaching the problem from a different perspective. Sometimes theory comes before discovery and points the way toward the right questions to ask. I hope this research stimulates other researchers' imaginations."
Monday, January 26, 2009
Honeybees are found to interact with Quantum fields
Monday, January 19, 2009
Our world may be a giant hologram
DRIVING through the countryside south of Hanover, it would be easy to miss the GEO600 experiment. From the outside, it doesn't look much: in the corner of a field stands an assortment of boxy temporary buildings, from which two long trenches emerge, at a right angle to each other, covered with corrugated iron. Underneath the metal sheets, however, lies a detector that stretches for 600 metres.
For the past seven years, this German set-up has been looking for gravitational waves - ripples in space-time thrown off by super-dense astronomical objects such as neutron stars and black holes. GEO600 has not detected any gravitational waves so far, but it might inadvertently have made the most important discovery in physics for half a century.
For many months, the GEO600 team-members had been scratching their heads over inexplicable noise that is plaguing their giant detector. Then, out of the blue, a researcher approached them with an explanation. In fact, he had even predicted the noise before he knew they were detecting it. According to Craig Hogan, a physicist at the Fermilab particle physics lab in Batavia, Illinois, GEO600 has stumbled upon the fundamental limit of space-time - the point where space-time stops behaving like the smooth continuum Einstein described and instead dissolves into "grains", just as a newspaper photograph dissolves into dots as you zoom in. "It looks like GEO600 is being buffeted by the microscopic quantum convulsions of space-time," says Hogan.
If this doesn't blow your socks off, then Hogan, who has just been appointed director of Fermilab's Center for Particle Astrophysics, has an even bigger shock in store: "If the GEO600 result is what I suspect it is, then we are all living in a giant cosmic hologram."
The idea that we live in a hologram probably sounds absurd, but it is a natural extension of our best understanding of black holes, and something with a pretty firm theoretical footing. It has also been surprisingly helpful for physicists wrestling with theories of how the universe works at its most fundamental level.
The holograms you find on credit cards and banknotes are etched on two-dimensional plastic films. When light bounces off them, it recreates the appearance of a 3D image. In the 1990s physicists Leonard Susskind and Nobel prizewinner Gerard 't Hooft suggested that the same principle might apply to the universe as a whole. Our everyday experience might itself be a holographic projection of physical processes that take place on a distant, 2D surface.
The "holographic principle" challenges our sensibilities. It seems hard to believe that you woke up, brushed your teeth and are reading this article because of something happening on the boundary of the universe. No one knows what it would mean for us if we really do live in a hologram, yet theorists have good reasons to believe that many aspects of the holographic principle are true.
Susskind and 't Hooft's remarkable idea was motivated by ground-breaking work on black holes by Jacob Bekenstein of the Hebrew University of Jerusalem in Israel and Stephen Hawking at the University of Cambridge. In the mid-1970s, Hawking showed that black holes are in fact not entirely "black" but instead slowly emit radiation, which causes them to evaporate and eventually disappear. This poses a puzzle, because Hawking radiation does not convey any information about the interior of a black hole. When the black hole has gone, all the information about the star that collapsed to form the black hole has vanished, which contradicts the widely affirmed principle that information cannot be destroyed. This is known as the black hole information paradox.
Bekenstein's work provided an important clue in resolving the paradox. He discovered that a black hole's entropy - which is synonymous with its information content - is proportional to the surface area of its event horizon. This is the theoretical surface that cloaks the black hole and marks the point of no return for infalling matter or light. Theorists have since shown that microscopic quantum ripples at the event horizon can encode the information inside the black hole, so there is no mysterious information loss as the black hole evaporates.
Crucially, this provides a deep physical insight: the 3D information about a precursor star can be completely encoded in the 2D horizon of the subsequent black hole - not unlike the 3D image of an object being encoded in a 2D hologram. Susskind and 't Hooft extended the insight to the universe as a whole on the basis that the cosmos has a horizon too - the boundary from beyond which light has not had time to reach us in the 13.7-billion-year lifespan of the universe. What's more, work by several string theorists, most notably Juan Maldacena at the Institute for Advanced Study in Princeton, has confirmed that the idea is on the right track. He showed that the physics inside a hypothetical universe with five dimensions and shaped like a Pringle is the same as the physics taking place on the four-dimensional boundary.
According to Hogan, the holographic principle radically changes our picture of space-time. Theoretical physicists have long believed that quantum effects will cause space-time to convulse wildly on the tiniest scales. At this magnification, the fabric of space-time becomes grainy and is ultimately made of tiny units rather like pixels, but a hundred billion billion times smaller than a proton. This distance is known as the Planck length, a mere 10-35 metres. The Planck length is far beyond the reach of any conceivable experiment, so nobody dared dream that the graininess of space-time might be discernable.
That is, not until Hogan realised that the holographic principle changes everything. If space-time is a grainy hologram, then you can think of the universe as a sphere whose outer surface is papered in Planck length-sized squares, each containing one bit of information. The holographic principle says that the amount of information papering the outside must match the number of bits contained inside the volume of the universe.
Since the volume of the spherical universe is much bigger than its outer surface, how could this be true? Hogan realised that in order to have the same number of bits inside the universe as on the boundary, the world inside must be made up of grains bigger than the Planck length. "Or, to put it another way, a holographic universe is blurry," says Hogan.
This is good news for anyone trying to probe the smallest unit of space-time. "Contrary to all expectations, it brings its microscopic quantum structure within reach of current experiments," says Hogan. So while the Planck length is too small for experiments to detect, the holographic "projection" of that graininess could be much, much larger, at around 10-16 metres. "If you lived inside a hologram, you could tell by measuring the blurring," he says.
When Hogan first realised this, he wondered if any experiment might be able to detect the holographic blurriness of space-time. That's where GEO600 comes in.
Gravitational wave detectors like GEO600 are essentially fantastically sensitive rulers. The idea is that if a gravitational wave passes through GEO600, it will alternately stretch space in one direction and squeeze it in another. To measure this, the GEO600 team fires a single laser through a half-silvered mirror called a beam splitter. This divides the light into two beams, which pass down the instrument's 600-metre perpendicular arms and bounce back again. The returning light beams merge together at the beam splitter and create an interference pattern of light and dark regions where the light waves either cancel out or reinforce each other. Any shift in the position of those regions tells you that the relative lengths of the arms has changed.
"The key thing is that such experiments are sensitive to changes in the length of the rulers that are far smaller than the diameter of a proton," says Hogan.
So would they be able to detect a holographic projection of grainy space-time? Of the five gravitational wave detectors around the world, Hogan realised that the Anglo-German GEO600 experiment ought to be the most sensitive to what he had in mind. He predicted that if the experiment's beam splitter is buffeted by the quantum convulsions of space-time, this will show up in its measurements (Physical Review D, vol 77, p 104031). "This random jitter would cause noise in the laser light signal," says Hogan.
In June he sent his prediction to the GEO600 team. "Incredibly, I discovered that the experiment was picking up unexpected noise," says Hogan. GEO600's principal investigator Karsten Danzmann of the Max Planck Institute for Gravitational Physics in Potsdam, Germany, and also the University of Hanover, admits that the excess noise, with frequencies of between 300 and 1500 hertz, had been bothering the team for a long time. He replied to Hogan and sent him a plot of the noise. "It looked exactly the same as my prediction," says Hogan. "It was as if the beam splitter had an extra sideways jitter."
Incredibly, the experiment was picking up unexpected noise - as if quantum convulsions were causing an extra sideways jitter
No one - including Hogan - is yet claiming that GEO600 has found evidence that we live in a holographic universe. It is far too soon to say. "There could still be a mundane source of the noise," Hogan admits.
Gravitational-wave detectors are extremely sensitive, so those who operate them have to work harder than most to rule out noise. They have to take into account passing clouds, distant traffic, seismological rumbles and many, many other sources that could mask a real signal. "The daily business of improving the sensitivity of these experiments always throws up some excess noise," says Danzmann. "We work to identify its cause, get rid of it and tackle the next source of excess noise." At present there are no clear candidate sources for the noise GEO600 is experiencing. "In this respect I would consider the present situation unpleasant, but not really worrying."
For a while, the GEO600 team thought the noise Hogan was interested in was caused by fluctuations in temperature across the beam splitter. However, the team worked out that this could account for only one-third of the noise at most.
Danzmann says several planned upgrades should improve the sensitivity of GEO600 and eliminate some possible experimental sources of excess noise. "If the noise remains where it is now after these measures, then we have to think again," he says.
If GEO600 really has discovered holographic noise from quantum convulsions of space-time, then it presents a double-edged sword for gravitational wave researchers. One on hand, the noise will handicap their attempts to detect gravitational waves. On the other, it could represent an even more fundamental discovery.
Such a situation would not be unprecedented in physics. Giant detectors built to look for a hypothetical form of radioactivity in which protons decay never found such a thing. Instead, they discovered that neutrinos can change from one type into another - arguably more important because it could tell us how the universe came to be filled with matter and not antimatter (New Scientist, 12 April 2008, p 26).
It would be ironic if an instrument built to detect something as vast as astrophysical sources of gravitational waves inadvertently detected the minuscule graininess of space-time. "Speaking as a fundamental physicist, I see discovering holographic noise as far more interesting," says Hogan.
Small price to pay
Despite the fact that if Hogan is right, and holographic noise will spoil GEO600's ability to detect gravitational waves, Danzmann is upbeat. "Even if it limits GEO600's sensitivity in some frequency range, it would be a price we would be happy to pay in return for the first detection of the graininess of space-time." he says. "You bet we would be pleased. It would be one of the most remarkable discoveries in a long time."
However Danzmann is cautious about Hogan's proposal and believes more theoretical work needs to be done. "It's intriguing," he says. "But it's not really a theory yet, more just an idea." Like many others, Danzmann agrees it is too early to make any definitive claims. "Let's wait and see," he says. "We think it's at least a year too early to get excited."
The longer the puzzle remains, however, the stronger the motivation becomes to build a dedicated instrument to probe holographic noise. John Cramer of the University of Washington in Seattle agrees. It was a "lucky accident" that Hogan's predictions could be connected to the GEO600 experiment, he says. "It seems clear that much better experimental investigations could be mounted if they were focused specifically on the measurement and characterisation of holographic noise and related phenomena."
One possibility, according to Hogan, would be to use a device called an atom interferometer. These operate using the same principle as laser-based detectors but use beams made of ultracold atoms rather than laser light. Because atoms can behave as waves with a much smaller wavelength than light, atom interferometers are significantly smaller and therefore cheaper to build than their gravitational-wave-detector counterparts.
So what would it mean it if holographic noise has been found? Cramer likens it to the discovery of unexpected noise by an antenna at Bell Labs in New Jersey in 1964. That noise turned out to be the cosmic microwave background, the afterglow of the big bang fireball. "Not only did it earn Arno Penzias and Robert Wilson a Nobel prize, but it confirmed the big bang and opened up a whole field of cosmology," says Cramer.
Hogan is more specific. "Forget Quantum of Solace, we would have directly observed the quantum of time," says Hogan. "It's the smallest possible interval of time - the Planck length divided by the speed of light."
More importantly, confirming the holographic principle would be a big help to researchers trying to unite quantum mechanics and Einstein's theory of gravity. Today the most popular approach to quantum gravity is string theory, which researchers hope could describe happenings in the universe at the most fundamental level. But it is not the only show in town. "Holographic space-time is used in certain approaches to quantising gravity that have a strong connection to string theory," says Cramer. "Consequently, some quantum gravity theories might be falsified and others reinforced."
Hogan agrees that if the holographic principle is confirmed, it rules out all approaches to quantum gravity that do not incorporate the holographic principle. Conversely, it would be a boost for those that do - including some derived from string theory and something called matrix theory. "Ultimately, we may have our first indication of how space-time emerges out of quantum theory." As serendipitous discoveries go, it's hard to get more ground-breaking than that.
via http://www.newscientist.com/article/mg20126911.300-our-world-may-be-a-giant-hologram.html?full=true
Saturday, January 17, 2009
Did dark energy give us our cosmos?
OUR universe may have arisen from seeds preserved in a universe that existed before the big bang - all thanks to dark energy.
One of the models put forward to explain how the universe began proposes that it is just the latest phase in a never-ending cycle. Proposed in 2002 by Paul Steinhardt of Princeton University and Neil Turok from the University of Cambridge, the model argues that our universe exists on a 3D region called a "brane" separated from similar branes by a fourth spatial dimension. Under the right conditions, these branes collide, triggering a big-bang-like event. After the collision, the branes bounce apart, before another collision occurs many billions of years later.
This model initially struggled to explain the ripples in the temperature and density of the universe that can be seen in the cosmic microwave background radiation left over from the big bang. The only way to make calculations based on the cyclic model produce the observed pattern of ripples is to add extra dimensions, as predicted by string theory, on top of the four spatial dimensions that the initial scenario envisaged.
Unfortunately, adding extra dimensions throws up another problem. As two branes approach, the additional dimensions must shrink or grow in sync with the dimension that separates the branes. Otherwise, large areas of the brane become warped, so that most of it ends up as black holes and only a tiny proportion as ordinary, habitable space. After several cycles, this space shrinks to nothing, so the process is unlikely to have led to our universe.
Without dark energy, most of the brane would end up as black holes, leaving only a tiny proportion as habitable space
Now calculations by Steinhardt and Jean-Luc Lehners, also at Princeton, show that when dark energy - the stuff that appears to be causing the expansion of the universe to accelerate - is brought into the picture, the cycling can be sustainable, so long as dark energy dominates for around 600 billion years.
In earlier cyclic models, dark energy has merely kept the cycles stable, and only dominated for the first 10 billion years or so. The pair say their calculations show that dark energy may in fact last much longer, and so is "absolutely essential" for the endurance of habitable regions. After each clash it would stretch the habitable regions so there is enough left after the next clash, and so on in subsequent cycles (see diagram). "Most of the universe is consumed in ashes, but the phoenix universe emerges once again from the small surviving seed," says Steinhardt (www.arxiv.org/abs/0812.3388).
This is not the first use of the term "phoenix universe". It was coined in 1933 by Georges Lemaître, an advocate of the big bang theory. "Our model is a more appropriate use of the name," Steinhardt claims. "We were motivated by the same conceptual issue: what happened at the big bang. Was it the beginning or not?"
Like its predecessors, the pair's work is built on a variant of string theory called M-theory which has yet to be completely fleshed out, says Peter Coles of the University of Cardiff in the UK. Andrew Liddle of the University of Sussex, UK, describes their model as a "neat and novel" picture, but adds that it is "hard to believe that we'll ever make observations that could show whether it is right or not".
However, Martin Bojowald of Pennsylvania State University, University Park, says their model is "more realistic" than previous versions, and that future measurements of dark energy may allow the idea to be tested.
Friday, January 16, 2009
Our world may be a giant hologram
DRIVING through the countryside south of Hanover, it would be easy to miss the GEO600 experiment. From the outside, it doesn't look much: in the corner of a field stands an assortment of boxy temporary buildings, from which two long trenches emerge, at a right angle to each other, covered with corrugated iron. Underneath the metal sheets, however, lies a detector that stretches for 600 metres.
For the past seven years, this German set-up has been looking for gravitational waves - ripples in space-time thrown off by super-dense astronomical objects such as neutron stars and black holes. GEO600 has not detected any gravitational waves so far, but it might inadvertently have made the most important discovery in physics for half a century.
For many months, the GEO600 team-members had been scratching their heads over inexplicable noise that is plaguing their giant detector. Then, out of the blue, a researcher approached them with an explanation. In fact, he had even predicted the noise before he knew they were detecting it. According to Craig Hogan, a physicist at the Fermilab particle physics lab in Batavia, Illinois, GEO600 has stumbled upon the fundamental limit of space-time - the point where space-time stops behaving like the smooth continuum Einstein described and instead dissolves into "grains", just as a newspaper photograph dissolves into dots as you zoom in. "It looks like GEO600 is being buffeted by the microscopic quantum convulsions of space-time," says Hogan.
If this doesn't blow your socks off, then Hogan, who has just been appointed director of Fermilab's Center for Particle Astrophysics, has an even bigger shock in store: "If the GEO600 result is what I suspect it is, then we are all living in a giant cosmic hologram."
The idea that we live in a hologram probably sounds absurd, but it is a natural extension of our best understanding of black holes, and something with a pretty firm theoretical footing. It has also been surprisingly helpful for physicists wrestling with theories of how the universe works at its most fundamental level.
The holograms you find on credit cards and banknotes are etched on two-dimensional plastic films. When light bounces off them, it recreates the appearance of a 3D image. In the 1990s physicists Leonard Susskind and Nobel prizewinner Gerard 't Hooft suggested that the same principle might apply to the universe as a whole. Our everyday experience might itself be a holographic projection of physical processes that take place on a distant, 2D surface.
The "holographic principle" challenges our sensibilities. It seems hard to believe that you woke up, brushed your teeth and are reading this article because of something happening on the boundary of the universe. No one knows what it would mean for us if we really do live in a hologram, yet theorists have good reasons to believe that many aspects of the holographic principle are true.
Susskind and 't Hooft's remarkable idea was motivated by ground-breaking work on black holes by Jacob Bekenstein of the Hebrew University of Jerusalem in Israel and Stephen Hawking at the University of Cambridge. In the mid-1970s, Hawking showed that black holes are in fact not entirely "black" but instead slowly emit radiation, which causes them to evaporate and eventually disappear. This poses a puzzle, because Hawking radiation does not convey any information about the interior of a black hole. When the black hole has gone, all the information about the star that collapsed to form the black hole has vanished, which contradicts the widely affirmed principle that information cannot be destroyed. This is known as the black hole information paradox.
Bekenstein's work provided an important clue in resolving the paradox. He discovered that a black hole's entropy - which is synonymous with its information content - is proportional to the surface area of its event horizon. This is the theoretical surface that cloaks the black hole and marks the point of no return for infalling matter or light. Theorists have since shown that microscopic quantum ripples at the event horizon can encode the information inside the black hole, so there is no mysterious information loss as the black hole evaporates.
Crucially, this provides a deep physical insight: the 3D information about a precursor star can be completely encoded in the 2D horizon of the subsequent black hole - not unlike the 3D image of an object being encoded in a 2D hologram. Susskind and 't Hooft extended the insight to the universe as a whole on the basis that the cosmos has a horizon too - the boundary from beyond which light has not had time to reach us in the 13.7-billion-year lifespan of the universe. What's more, work by several string theorists, most notably Juan Maldacena at the Institute for Advanced Study in Princeton, has confirmed that the idea is on the right track. He showed that the physics inside a hypothetical universe with five dimensions and shaped like a Pringle is the same as the physics taking place on the four-dimensional boundary.
According to Hogan, the holographic principle radically changes our picture of space-time. Theoretical physicists have long believed that quantum effects will cause space-time to convulse wildly on the tiniest scales. At this magnification, the fabric of space-time becomes grainy and is ultimately made of tiny units rather like pixels, but a hundred billion billion times smaller than a proton. This distance is known as the Planck length, a mere 10-35 metres. The Planck length is far beyond the reach of any conceivable experiment, so nobody dared dream that the graininess of space-time might be discernable.
That is, not until Hogan realised that the holographic principle changes everything. If space-time is a grainy hologram, then you can think of the universe as a sphere whose outer surface is papered in Planck length-sized squares, each containing one bit of information. The holographic principle says that the amount of information papering the outside must match the number of bits contained inside the volume of the universe.
Since the volume of the spherical universe is much bigger than its outer surface, how could this be true? Hogan realised that in order to have the same number of bits inside the universe as on the boundary, the world inside must be made up of grains bigger than the Planck length. "Or, to put it another way, a holographic universe is blurry," says Hogan.
This is good news for anyone trying to probe the smallest unit of space-time. "Contrary to all expectations, it brings its microscopic quantum structure within reach of current experiments," says Hogan. So while the Planck length is too small for experiments to detect, the holographic "projection" of that graininess could be much, much larger, at around 10-16 metres. "If you lived inside a hologram, you could tell by measuring the blurring," he says.
When Hogan first realised this, he wondered if any experiment might be able to detect the holographic blurriness of space-time. That's where GEO600 comes in.
Gravitational wave detectors like GEO600 are essentially fantastically sensitive rulers. The idea is that if a gravitational wave passes through GEO600, it will alternately stretch space in one direction and squeeze it in another. To measure this, the GEO600 team fires a single laser through a half-silvered mirror called a beam splitter. This divides the light into two beams, which pass down the instrument's 600-metre perpendicular arms and bounce back again. The returning light beams merge together at the beam splitter and create an interference pattern of light and dark regions where the light waves either cancel out or reinforce each other. Any shift in the position of those regions tells you that the relative lengths of the arms has changed.
"The key thing is that such experiments are sensitive to changes in the length of the rulers that are far smaller than the diameter of a proton," says Hogan.
So would they be able to detect a holographic projection of grainy space-time? Of the five gravitational wave detectors around the world, Hogan realised that the Anglo-German GEO600 experiment ought to be the most sensitive to what he had in mind. He predicted that if the experiment's beam splitter is buffeted by the quantum convulsions of space-time, this will show up in its measurements (Physical Review D, vol 77, p 104031). "This random jitter would cause noise in the laser light signal," says Hogan.
In June he sent his prediction to the GEO600 team. "Incredibly, I discovered that the experiment was picking up unexpected noise," says Hogan. GEO600's principal investigator Karsten Danzmann of the Max Planck Institute for Gravitational Physics in Potsdam, Germany, and also the University of Hanover, admits that the excess noise, with frequencies of between 300 and 1500 hertz, had been bothering the team for a long time. He replied to Hogan and sent him a plot of the noise. "It looked exactly the same as my prediction," says Hogan. "It was as if the beam splitter had an extra sideways jitter."
via http://www.newscientist.com/article/mg20126911.300-our-world-may-be-a-giant-hologram.html?full=true
Monday, January 12, 2009
How to hallucinate with ping-pong balls and a radio
DO YOU EVER want to change the way you see the world? Wouldn't it be fun to hallucinate on your lunch break? Although we typically associate such phenomena with powerful drugs like LSD or mescaline, it's easy to fling open the doors of perception without them: All it takes is a basic understanding of how the mind works.
The first thing to know is that the mind isn't a mirror, or even a passive observer of reality. Much of what we think of as being out there actually comes from in here, and is a byproduct of how the brain processes sensation. In recent years scientists have come up with a number of simple tricks that expose the artifice of our senses, so that we end up perceiving what we know isn't real - tweaking the cortex to produce something uncannily like hallucinations. Perhaps we hear the voice of someone who is no longer alive, or feel as if our nose is suddenly 3 feet long.
via http://www.boston.com/bostonglobe/ideas/graphics/011109_hacking_your_brain/
Saturday, January 10, 2009
Wednesday, January 7, 2009
Did our cosmos exist before the big bang?
Ashtekar wanted to be sure of what he was seeing, so he asked his colleagues to sit on the result for six months before publishing it in 2006. And no wonder. The theory that the recycled universe was based on, called loop quantum cosmology (LQC), had managed to illuminate the very birth of the universe - something even Einstein's general theory of relativity fails to do.
Einstein's relativity fails to explain the very birth of the universe
LQC has been tantalising physicists since 2003 with the idea that our universe could conceivably have emerged from the collapse of a previous universe. Now the theory is poised to make predictions we can actually test. If they are verified, the big bang will give way to a big bounce and we will finally know the quantum structure of space-time. Instead of a universe that emerged from a point of infinite density, we will have one that recycles, possibly through an eternal series of expansions and contractions, with no beginning and no end.
LQC is in fact the first tangible application of another theory called loop quantum gravity, which cunningly combines Einstein's theory of gravity with quantum mechanics. We need theories like this to work out what happens when microscopic volumes experience an extreme gravitational force, as happened near the big bang, for example. In the mid 1980s, Ashtekar rewrote the equations of general relativity in a quantum-mechanical framework. Together with theoretical physicists Lee Smolin and Carlo Rovelli, Ashtekar later used this framework to show that the fabric of space-time is woven from loops of gravitational field lines. Zoom out far enough and space appears smooth and unbroken, but a closer look reveals that space comes in indivisible chunks, or quanta, 10-35 square metres in size.
In 2000, Martin Bojowald, then a postdoc with Ashtekar at the Pennsylvania State University in University Park, used loop quantum gravity to create a simple model of the universe. LQC was born.
Bojowald's major realisation was that unlike general relativity, the physics of LQC did not break down at the big bang. Cosmologists dread the singularity because at this point gravity becomes infinite, along with the temperature and density of the universe. As its equations cannot cope with such infinities, general relativity fails to describe what happens at the big bang. Bojowald's work showed how to avoid the hated singularity, albeit mathematically. "I was very impressed by it," says Ashtekar, "and still am."
Jerzy Lewandowski of the University of Warsaw in Poland, along with Bojowald, Ashtekar and two more of his postdocs, Parampreet Singh and Tomasz Pawlowski, went on to improve on the idea. Singh and Pawlowski developed computer simulations of the universe according to LQC, and that's when they saw the universe bounce. When they ran time backwards, instead of becoming infinitely dense at the big bang, the universe stopped collapsing and reversed direction. The big bang singularity had truly disappeared (Physical Review Letters, vol 96, p 141301).
But the celebration was short-lived. When the team used LQC to look at the behaviour of our universe long after expansion began, they were in for a shock - it started to collapse, challenging everything we know about the cosmos. "This was a complete departure from general relativity," says Singh, who is now at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. "It was blatantly wrong."
Ashtekar took it hard. "I was pretty depressed," he says. "It didn't bode well for LQC." However, after more feverish mathematics, Ashtekar, Singh and Pawlowski solved the problem. Early versions of the theory described the evolution of the universe in terms of quanta of area, but a closer look revealed a subtle error. Ashtekar, Singh and Pawlowski corrected this and found that the calculations now involved tiny volumes of space.
It made a crucial difference. Now the universe according to LQC agreed brilliantly with general relativity when expansion was well advanced, while still eliminating the singularity at the big bang. Rovelli, based at the University of the Mediterranean in Marseille, France, was impressed. "This was a very big deal," he says. "Everyone had hoped that once we learned to treat the quantum universe correctly, the big bang singularity would disappear. But it had never happened before."
Physicist Claus Kiefer at the University of Cologne in Germany, who has written extensively about the subject, agrees. "It is really a new perspective on how we can view the early universe," he says. "Now, you have a theory that can give you a natural explanation for a singularity-free universe." He adds that while competing theories of quantum gravity, such as string theory, have their own insights to offer cosmology, none of these theories has fully embraced quantum mechanics.
If LQC turns out to be right, our universe emerged from a pre-existing universe that had been expanding before contracting due to gravity. As all the matter squeezed into a microscopic volume, this universe approached the so-called Planck density, 5.1 × 1096 kilograms per cubic metre. At this stage, it stopped contracting and rebounded, giving us our universe.
The pre-existing universe was squeezed into a microscopic volume
"You cannot reach the Planck density. It is forbidden by theory," says Singh. According to Bojowald, that is because an extraordinary repulsive force develops in the fabric of space-time at densities equivalent to compressing a trillion solar masses down to the size of a proton. At this point, the quanta of space-time cannot be squeezed any further. The compressed space-time reacts by exerting an outward force strong enough to repulse gravity. This momentary act of repulsion causes the universe to rebound. From then on, the universe keeps expanding because of the inertia of the big bounce. Nothing can slow it down - except gravity.
LQC also illuminates another mysterious phase of our universe. In classical cosmology, a phenomenon called inflation caused the universe to expand at incredible speed in the first fractions of a second after the big bang. This inflationary phase is needed to explain why the temperature of faraway regions of the universe is almost identical, even though heat should not have had time to spread that far - the so-called horizon problem. It also explains why the universe is so finely balanced between expanding forever and contracting eventually under gravity - the flatness problem. Cosmologists invoke a particle called the inflaton to make inflation happen, but precious little is known about it.
Cosmic recall
More importantly, even less is known about the pre-inflationary universe. Cosmologists have always assumed that they could ignore quantum effects and regard space-time as smooth at the onset of inflation, as general relativity requires. This had always been an educated guess - until now. LQC shows that at the time inflation begins, space-time can be treated as smooth. "This is not an assumption any more," says Singh. "It's actually a prediction from loop quantum cosmology."
The models developed by Ashtekar, Singh, Bojowald and Pawlowski represent an enormous step forward. This is the first time that a theory is able to make predictions about what was happening prior to inflation, while correctly predicting what happens post-inflation. "To do both of these things at the same time has been difficult," says Ashtekar.
If the universe we inhabit emerged from a previous cosmos, can we know something about the universe that preceded ours? LQC simulations show that it too would have had stars and galaxies. But opinions differ when it comes to the quantum phase just before and after the big bounce, when it is impossible to pin down the volume of the universe due to quantum fluctuations. Bojowald's calculations show that some of the information about the earlier universe is wiped out as it goes through the big bounce. In other words, there is no "cosmic recall" (Nature Physics, vol 3, p 523). In contrast, another detailed analysis done by Singh and Alejandro Corichi, of the Autonomous National University of Mexico in Michoacán, suggests otherwise (Physical Review Letters, vol 100, p 161302).
Ashtekar likens the spirited spat among his former postdocs and students to watching his children squabble. "It's much ado about nothing," he says. Though arguments about the universe possibly having a cosmic recall may be of philosophical interest, they are premature. "We should be worrying about making contact with experiments today."
That day may be near. The researchers' first target is the cosmic microwave background (CMB), a radiation released long after the universe's quantum phase. Even though the CMB originated 370,000 years after the big bang, its seeds were laid out much earlier, says Bojowald. "That could be a period when quantum gravity effects might play a role."
Bojowald has discovered that such effects would have dominated when, according to LQC, the universe went through a short phase of accelerated expansion before the onset of inflation. Dubbed superinflation, it occurred due to the immense repulsive forces of the high-density quantum universe rather than the presence of inflatons. Exactly how this phase might affect the CMB is unclear, but already there are hints that LQC might predict something different from classical cosmology. "This is what we are going to work on in the next two years. We are going to find robust predictions," says Singh.
Meanwhile, Ed Copeland of the University of Nottingham, UK, and his colleagues have shown that superinflation can produce the kind of quantum fluctuations in the fabric of space-time that eventually became seeds for the formation of galaxies and clusters of galaxies. This suggests that superinflation might make inflation unnecessary, thus removing what has essentially always been an add-on to standard cosmological theory. It is early days for superinflation, though, because it cannot yet solve the horizon and flatness problems that inflation so elegantly resolves.
Copeland says that future experiments might reveal whether our universe underwent inflation or superinflation by looking for a pattern of gravitational waves that only inflation could have created. These ripples in the fabric of space-time would have polarised the CMB, though the effect is too faint for today's instruments to detect. Things might change next year, however, when the European Space Agency launches the Planck satellite, promising the most detailed view of the microwave background to date. Copeland's work suggests that superinflation would suppress the production of gravitational waves at cosmological scales, and that there would be no such imprint in the CMB. "If you do detect them, it would probably count against LQC," he says.
Kiefer cautions that all the predictions of LQC are subject to one big caveat. The predictions of classical cosmology come from solving the equations of general relativity, albeit with certain simplifying assumptions about the universe. Ideally, LQC should be put on the same footing - all its equations should be derived from loop quantum gravity. Instead, Bojowald and others obtained LQC by starting with an idealised universe derived from general relativity and then using techniques from loop quantum gravity to quantise gravity in the model. "From a physicist's point of view, it is fully justified," says Kiefer. "Mathematicians perhaps would not be amused."
Rovelli agrees. To put LQC on a firmer foundation, he and his colleague Francesca Vidotto have been working to reconcile it with loop quantum gravity (www.arxiv.org/abs/0805.4585v1). "The conclusion is very positive," says Rovelli. "We are able to recover the equations of LQC, starting with something much closer to loop quantum gravity."
No wonder Rovelli is looking forward to upcoming experiments that could vindicate the theory. "I hope before dying to know whether loop quantum gravity is correct or not," he says. For a man who turned 50 only recently, he is being unduly pessimistic. A raft of experiments, of which Planck is only the first, will soon be measuring the CMB and looking for gravitational waves. A revolution in our notions of how our universe began may be closer than he thinks.
Will our universe bounce?
According to the big bounce picture formulated by theoretical physicist Abhay Ashtekar and others, the cosmos grew from the collapse of a pre-existing universe. Will the same fate await us?It depends. We used to think that the universe was dominated by the gravity of its stars and other matter: either the universe is dense enough for gravity to halt the expansion from the big bang and pull everything back, or else it isn't, in which case the expansion would carry on forever. However, observations of distant supernovae in the past 10 years have challenged that view. They show not just that the universe is expanding, but also that the expansion is speeding up due to a mysterious repulsive force that cosmologists call "dark energy". So if the universe fails to contract, has it already bounced its last bounce?Perhaps not. Cosmologists are still very much in the dark about dark energy. Some theoretical models speculate that the nature of dark energy could change over time, switching from a repulsive to an attractive force that behaves much like gravity. If that happens, the universe will stop expanding and the galaxies will begin to rush together. A question mark also hangs over the universe's matter and energy density, which we have not measured with sufficient accuracy to be sure that the universe will not eventually stop expanding. If it turns out to be a smidgen greater than current observations, then it is a recipe for cosmic collapse.According to the big bounce, in both scenarios the universe will eventually collapse until it reaches the highest density allowed by the theory. At this point, the universe will rebound and begin expanding again - the ultimate in cosmic recycling.
via
Water Vapor Confirmed on Alien Planet
The unequivocal signature of water vapor has been found on a planet beyond our solar system.
Using NASA's Spitzer Space Telescope, astronomers detected the steamy signature of water vapor in the light coming from a large exoplanet circling around a star about 63 light-years from Earth. Though it's not the first sign of water vapor around this planet, it's the strongest evidence yet.
The planet, HD 189733b, is what's called a "Hot Jupiter" — a boiling, gigantic gas planet more akin to our own Jupiter or Saturn than to a terrestrial planet like Earth. It's not a good candidate itself for alien life, but the successful detection of water vapor here, in the location and quantities that theorists predicted, bodes well for further studies of more promising locales for extraterrestrial life.
"It means we're starting to understand these objects a little bit better than we did when we first started," astrophysicist Adam Burrows of Princeton University told Wired.com. "It’s a trial run for the much more detailed investigations that will be possible in the years to come as we take this stepping stone from giant planets to terrestrial planets."
Though water vapor is thought to be fairly common on planets — even our own Jupiter has it — the discovery of its presence on another world is significant and points the way toward future discoveries, scientists say. Yesterday scientists announced that the Hubble Space Telescope had found carbon dioxide, which under the right circumstances could be connected to life, on the same planet. The presence of methane has also been detected.
Burrows and the research team, led by Carl Grillmair of the California Institute of Technology, used a technique known as the secondary-eclipse method to observe the infrared light coming from the planet. The world is so close to its star that normally the light from the two objects cannot be distinguished. But when the planet orbits behind the star, only the light from the star is visible. By subtracting the star's light from the total light of star plus planet, the scientists were able to isolate only the planet's light. When they separated the image into its constituent colors in a process called spectroscopy, they found the characteristic dip in light of a certain wavelength that results from water in the planet's atmosphere absorbing that light.
"We’re looking at the brightness of the planet, as opposed to the effect of the stellar light," Burrows said. "The data we have is the best spectrum ever taken of a planet outside the solar system."
In an article accompanying the research paper, published Wednesday in the journal Nature, astronomer Drake Deming of the NASA Goddard Space Flight Center in Greenbelt, Maryland, wrote, "We must first learn how to detect abundant molecules such as water before we can advance to identifying the more subtle signatures that scarcer molecules such as molecular oxygen leave in exoplanet spectra. Grillmair and colleagues have taken that first step."
Citation: "Strong water absorption in the dayside emission spectrum of the planet HD 189733b" by Carl J. Grillmair, Adam Burrows, David Charbonneau, Lee Armus, John Stauffer, Victoria Meadows, Jeffrey van Cleve, Kaspar von Braun and Deborah Levine. Nature: doi:10.1038/nature07574.
via http://blog.wired.com/wiredscience/2008/12/embargoed---wat.html
Science of Santa: How Santa Delivers All His Presents in One Night
Newswise — Don’t believe in Santa Claus? Cutting-edge science explains how Santa is able to deliver toys to good girls and boys around the world in one night.
If you’re skeptical of Santa’s abilities to deliver presents to millions of homes and children in just one night, North Carolina State University’s Dr. Larry Silverberg, professor of mechanical and aerospace engineering, can explain the science and engineering principles that allow the Jolly Old Elf to pull off the magical feat year after year.
With his cherubic smile and twinkling eyes, Santa may appear to be merely a jolly old soul, but he and his North Pole elves have a lot going on under the funny-looking hats, Silverberg says. Their advanced knowledge of electromagnetic waves, the space/time continuum, nanotechnology, genetic engineering and computer science easily trumps the know-how of contemporary scientists.
Silverberg says that Santa has a personal pipeline to children’s thoughts – via a listening antenna that combines technologies currently used in cell phones and EKGs – which informs him that Mary in Miami hopes for a surfboard, while Michael from Minneapolis wants a snowboard. A sophisticated signal processing system filters the data, giving Santa clues on who wants what, where children live, and even who’s been bad or good. Later, all this information will be processed in an onboard sleigh guidance system, which will provide Santa with the most efficient delivery route.
Silverberg adds that letters to Santa via snail mail still get the job done, however.
Silverberg is not so naïve as to think that Santa and his reindeer can travel approximately 200 million square miles – making stops in some 80 million homes – in one night. Instead, he posits that Santa uses his knowledge of the space/time continuum to form what Silverberg calls “relativity clouds.”
“Based on his advanced knowledge of the theory of relativity, Santa recognizes that time can be stretched like a rubber band, space can be squeezed like an orange and light can be bent,” Silverberg says. “Relativity clouds are controllable domains – rips in time – that allow him months to deliver presents while only a few minutes pass on Earth. The presents are truly delivered in a wink of an eye.”
With a detailed route prepared and his list checked twice through the onboard computer on the technologically advanced sleigh, Santa is ready to deliver presents. His reindeer – genetically bred to fly, balance on rooftops and see well in the dark – don’t actually pull a sleigh loaded down with toys. Instead, each house becomes Santa’s workshop as he utilizes a nano-toymaker to fabricate toys inside the children’s homes. The presents are grown on the spot, as the nano-toymaker creates – atom by atom – toys out of snow and soot, much like DNA can command the growth of organic material like tissues and body parts.
And there’s really no need for Santa to enter the house via chimney, although Silverberg says he enjoys doing that every so often. Rather, the same relativity cloud that allows Santa to deliver presents in what seems like a wink of an eye is also used to “morph” Santa into people’s homes.
Finally, many people wonder how Santa and the reindeer can eat all the food left out for them. Silverberg says they take just a nibble at each house. The remainder is either left in the house or placed in the sleigh’s built-in food dehydrator, where it is preserved for future consumption. It takes a long time to deliver all those presents, after all.
“This is our vision of Santa’s delivery method, given the human, physical and engineering constraints we face today,” Silverberg says. “Children shouldn’t put too much credence in the opinions of those who say it’s not possible to deliver presents all over the world in one night. It is possible, and it’s based on plausible science.”
Fun with Numbers
The numbers we all use (1, 2, 3, 4, etc.) are known as "arabic" numbers to distinguish them from the "Roman Numerals" (I, II, III, IV, V, VI, etc). Actually the arabs popularized these numbers but they were originally used by the early phonecian traders to count and keep track of their trading accounts.
Have you ever thought why ........ 1 means "one", and 2 means "two"? The roman numerals are easy to understand but what was the logic behind the phonecian numbers?
It's all about angles !
It's the number of angles. If one writes the numbers down (see below) on a piece of paper in their older forms, one quickly sees why. I have marked the angles with "o"s.
No 1 has one angle.
No 2 has two angles.
No 3 has three angles.
etc.
and "O" has no angles
Interesting, isn't it?
An ancient phonecian manuscript explains this and I thought it to be fascinating <g>.
Monday, January 5, 2009
Why You Can’t Travel Back in Time and Kill Hitler
His Life is a Fixed Event in Time
“No Time Like the Past” (The Twilight Zone): Paul Driscoll is a well-meaning but ineffectual time traveler. Not only does he fail to kill Hitler (thanks to the intervention of a suspicious maid), he also fails to warn the Hiroshima police about the atomic bomb and fails to keep the Lusitania from being torpedoed. It turns out that he is unable to change past events, and, when he does effect events in the past, it is only as part of a predestination paradox.
He’s More Clever Than You'd Think
I Killed Adolph Hitler by Jason: When a depressed hitman is contracted to go back in time and kill Hitler, the Fuhrer gets the better of him, stealing his time machine and leaving the hitman in the past to wait and plan his revenge.
You’re Actually Part of a Predestination Paradox
“The Primal Solution” by Eric Norden: An elderly Holocaust survivor discovers a method of mental time travel and seeks to undo the horrors he witnessed in his youth by possessing the body of the young Hitler. He humiliates the young Austrian, then tries to goad Hitler into suicide, but Hitler regains control of his body before the deed can be accomplished. The young Hitler is so haunted by the encounter with the Jewish man’s mind that he resolves that he can only find peace by exterminating the entire Jewish people.
Cradle of Darkness (The Twilight Zone): Katherine Heigl travels to 1889 Austria in order to kill the infant Hitler. She succeeds in killing the baby by jumping into a river with it, but Adolph’s mother buys another baby and raises it as her own. And that baby grows into the Adolph Hitler that Heigl’s character set out to kill.
His Guards Are Used to Dealing with Time Traveling Assassins
Subnormality: In this strip of the webcomic Subnormality, we learn that Hitler’s guards are actually quite adept at killing time travelers before they get to Hitler. And all those attempts have got to make them wonder…
You’ll Be Thwarted By Other Time Travelers
Midnighter: In the first arc of the Midnighter solo series, a man named Paulus claims to have replaced Midnighter’s secondary heard with a bomb, which he will detonate unless Midnighter goes back in time and kills Hitler. Midnighter does try to kill Hitler as a young German soldier, but he is stopped by time police from the 95th Century.
Days of Cain by JR Dunn: A group of rebel time agents seek to undo one of humanity’s greatest atrocities by killing Hitler, or, barring that, dismantling the death camps from within. But a society of time agents known as the Moiety is determined to preserve a certain version of the timeline of any cost, giving their agent Gasper James the unenviable task of ensuring the Holocaust goes forward.
“Wikihistory” by Desmond Warzel: One of the bylaws of the International Association of Time Travelers states that you can’t kill Hitler. The problem is, everybody kills Hitler on their first trip. This leaves more experienced time travelers the onerous task of undoing the historical edits of n00bs.
Killing Him Just Brings About a Potentially Worse Future
Command & Conquer: Red Alert: In the video game, Albert Einstein invents a time machine, which he uses to go back in time and deleted Hitler from time before he could rise to power. But, without a strong Germany, Stalin’s Russia invades Europe, and eventually the United States.
It’s All Just a Dream
via http://io9.com/5094494/why-you-cant-travel-back-in-time-and-kill-hitler
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