- World’s Most Precise Clocks Could Reveal Universe Is a Hologram
- Spiral Galaxy Study Yields Super Sharp Images
- Video: Magnetic Twister Erupts on Sun
- Sleeping Mars Rover Finds Evidence of Liquid Water
- Your Fingers Know When You Make a Typo
- Odds of Finding Earth-Size Exoplanets Are 1-in-4
- Climate Change Blurs Definition of Native Species
Posted: 28 Oct 2010 04:11 PM PDT
Our existence could be coded in a finite bandwidth, like a live ultra-high-definition 3-D video. And the third dimension we know and love could be no more than a holographic projection of a 2-D surface.
A scientist's experiment, now under construction in Illinois, will attempt to test these ideas by the end of next year using what will be two of the world's most precise clocks.
Skeptics of a positive result abound, but their caution comes with good reason: The smallest pieces of space, time, mass and other properties of the universe, called Planck units, are so tiny that verifying them by experiment may be impossible. The Planck unit of length, for example, is 10 trillion trillion times smaller than the width of a proton.
Craig Hogan, a particle astrophysicist at Fermilab in Illinois, isn't letting this seemingly insurmountable barrier stop him from trying.
Hogan is following through on a radical idea to confirm Planck units with two of the most precise clocks in the world. Deemed holometers, each L-shaped laser interferometer will have two perpendicular, 131-foot-long arms to scan for pixelation in the very fabric of space and time. If it's there, two laser beams (split from a single source) that run through the arms won't hit a detector at the same time.
"What we're looking for is when the lasers lose step with each other. We're trying to detect the smallest unit in the universe," Hogan said. "This is really great fun, a sort of old-fashioned physics experiment where you don't know what the result will be."
The two holometers, now being built in an earth-covered tunnel on Fermilab's prairie-covered campus, will initially be stacked almost on top of one another to listen for the same Planck-scale "noise." Once the machine is calibrated and environmental interference is accounted for, Hogan says it should only take a matter of minutes to see if the devices simultaneously see it.
Should Hogan's team detect something significant, they will then separate the machines and run the experiment all over again. If the noise they measure next isn't correlated between the machines, it could be the calling card of a limit to space-time's resolution.
Inspiration for the holometer came from such a noise picked up by an experiment called GEO600. Designed to detect gravity waves — ripples in space-time caused by things like colliding black holes — the machine is a laser interferometer like the holometer will be, yet has arms 15 times longer and a lower-frequency laser source (to be sensitive to gravity waves, if they exist).
Experimental physicist Hartmut Grote, of the Max Planck Institute in Germany, said he and his colleagues at GEO600 have been unable to pinpoint the source.
"In the past, [Hogan] became a little bit driven, even excited for some time, that this noise could be a result of the holographic principle," Grote said.
The holographic principle, derived from weirdness theorized to occur at the boundaries of black holes, says reality could be a 3-D projection of a 2-D plane of information. It's much the same way a hologram printed on a credit card creates the illusion of a 3-D object but, as Hogan explained, we can't perceive the 2-D surface.
"We could be living inside that 3-D projection, with the truer vision of it as a 2-D sheet hidden by scale," Hogan said.
Ultra-precise devices such as laser interferometers might be able to detect noisy fluctuations in the projection, which Grote says might "blow up" the pixelation to a larger, detectable size. Yet Grote suggests Hogan's holometers, which are slated to be finished in a year, may be too late if progress with GEO600 continues on-schedule.
"We are not at the point where we can verify the noise we discovered is holographic, but we can falsify it as soon as our instrument is more sensitive than the limits of Hogan's theory," Grote said. "I'm confident we will reach that point over the next half of a year and find the source of the noise."
Hogan maintains his cheeriness for the endeavor, even if much of the physics community remains skeptical. But Grote says Hogan has good reason to be upbeat.
"I think it's a reasonable design to measure this effect, even though I think it's unlikely he's going to measure something," Grote said. "If anything happens, he'll put to rest another exotic theory about the universe."
If he does find a limit to the universe's resolution by exploiting the cosmos' possible holographic underpinnings, however, Grote said it will make waves.
"It would be a very strong impact to one of the most open questions in fundamental physics," he said. "It would be the first proof that space-time, the fabric of the universe, is quantized."
Via: symmetry breaking
Images: Fermilab. 1) A schematic plan of the holometers. 2) Sam Waldman, a physicist at MIT, working on the holometer's first arm. 3) The tunnel housing the first arm of the experiment. 4) A chart showing where, if the holographic principle holds true, the holometer is just beyond the threshold of detecting holographic noise (GEO600 is on the border).
Posted: 28 Oct 2010 03:00 PM PDT
Six spiral galaxies were stripped bare by an infrared camera at the Very Large Telescope in Chile.
By observing in wavelengths of light beyond what the human eye can see, the camera, called HAWK-I, can peer through the gas and dust that obscure galaxies' spiral arms. This makes it ideal for studying how many stars make their homes there.
The six galaxies are part of a study of spiral structure led by Preben Grosbøl at the European Southern Observatory, who is investigating how stars form into such perfect spiral patterns.
The galaxies represent three different classes of spiral shapes. Three of them — dubbed NGC 5247, NGC 4030 and NGC 2997 — are simply designated as spiral galaxies. One galaxy, NGC 1300, is a "barred spiral," with two arms extending from a prominent central bar. Another, NGC 1232, is an "intermediate spiral," lying somewhere between barred and unbarred galaxies. And NGC 4321 (also known as Messier 100) is a "grand spiral," featuring several well-defined, tentacle-like spiral arms.
This growing galactic gallery shows the diversity of galaxy shapes with unusual clarity.
Images: ESO/P. Grosbøl
Posted: 28 Oct 2010 02:35 PM PDT
NASA's Solar Dynamics Observatory caught an enormous plasma twister erupting on the surface of the sun Oct. 28.
The explosion was triggered by a tangled coil of magnetism that suddenly untwisted, acting like a loaded spring and hurling solar matter into space. At its peak, the twister towered more than 217,000 miles above the surface of the sun.
Luckily, the fragments of plasma flung into space were not headed toward Earth, where they could have caused a magnetic storm. Now that the twister has relaxed, it probably won't erupt again — though other sunspots are gathering energy and could produce medium-sized solar flares.
Posted: 28 Oct 2010 01:12 PM PDT
The soft Martian soil that ensnared the rover Spirit holds evidence that liquid water still trickles below the planet's surface. But this serendipitous discovery may be Spirit's last.
Spirit's wheels broke through the crust of a sand pit called "Troy" in April 2009, after five years spent mostly exploring a region called Home Plate. NASA officially gave up on trying to extract the rover in January.
But the soil exposed by Spirit's spinning wheels carries clues that Mars may still be wet. The newly exposed surface layers include minerals thought to be hematite, silica and gypsum, which don't dissolve easily in water. But layers of iron sulfate minerals, which do dissolve easily, lie centimeters below the crust.
These layers suggest water, maybe in the form of frost or snow, seeped into the ground relatively recently and carried the soluble minerals deeper into the soil. The seepage could have happened during cycles in Mars' history when the planet tilted further on its axis.
None of these soluble minerals are exposed at the Martian surface, which indicates the soil interacted with water recently, and probably continuously. Because the Martian surface is constantly being sculpted by wind, these layers would have eroded away if they were laid down long ago.
Water could also have come from fumaroles or hot vents beneath the surface, the rover team reports in the Journal of Geophysical Research.
"On Earth, fumaroles and hydrothermal systems provide the environmental conditions, water, nutrients and energy sources needed to sustain robust microbial communities," the team wrote. A prime example is the acidic, iron-rich hot springs in Yellowstone National Park.
"It seems likely that the region in and around Home Plate may have likewise supported a habitable environment," the team wrote. Although there may not have been enough water to sustain life for long.
In 10 attempts to break free, Spirit only managed to drive 13 inches backwards through the soft soil before NASA gave up in January. Spirit shut down completely on March 22 to hibernate through the Martian winter. If the rover wakes up again when Martian spring arrives next month, there will be fresh soil to explore. The researchers also plan to take advantage of Spirit's immobilization to investigate whether Mars's core is liquid or solid by precisely tracking the rover's radio signal.
But Spirit has sat through colder temperatures this winter than it ever experienced, and its solar panels were stuck facing away from the sun. It may not wake up. Scientists are crossing their fingers, but not holding their breath.
Image: NASA/JPL-Caltech/Cornell University
Posted: 28 Oct 2010 12:03 PM PDT
The brain uses two different checks to guard against sloppy copy, a new study finds. By using a doctored word processor to sneak errors into typed words and surreptitiously fix typists' real errors, researchers teased apart the various ways people catch their own mistakes. The study, published in the Oct. 29 Science, highlights the complexity of performance monitoring.
Psychologist Gordon Logan and his colleague Matthew Crump of Vanderbilt University in Nashville recruited skilled typists — people who typed more than 40 words a minute using all of their fingers. These subjects were able to type a paragraph about the merits of border collies with over 90 percent accuracy.
As the typists pecked away, researchers introduced common typing errors into about 6 percent of the words that appeared on a screen (changing sweat to swaet, swerat or swet, for instance). The program also corrected about 45 percent of the typists' true errors.
In questionnaires after the typing test, subjects by and large took the blame for the introduced errors and took credit for the researchers' corrections. No matter what he actually typed, when the typist saw that the word on the screen matched the word he had intended to type, he assessed his own performance as accurate.
But the speed of the typists' keystrokes revealed something else. After hitting the wrong key, a typist's fingers slowed down for the next keystroke, even if the researchers sneakily fixed the error so that the typist didn't notice it. In these cases, a typist wasn't explicitly aware of the mistake, but the brain's motor signal changed nevertheless.
Logan says that this change in timing reflects a kind of automatic assessment of performance. "The body is doing one thing and the mind is doing another," he says. "What we found was that the fingers knew the truth."
Many psychologists thought that the mind was capable of detecting errors in several ways, but "nobody had pinned it down," says cognitive neuroscientist Jonathan Cohen of Princeton University. "Here, they developed a very clever set of experiments to tease the types of system apart."
The results may reveal a hierarchical method of error correction — with a "lower" system doing the actual work and a "higher" system assigning credit and blame, Logan suggests. These multiple layers of control may be evident in tasks such as playing music, speaking and walking to a destination, Logan says. As a man heads toward a new restaurant, his brain is noticing landmarks and keeping on the right course. Meanwhile, his feet steadily plod along, navigating the terrain automatically.
Whether the two types of error-catching systems operate in tandem or one is subservient to the other isn't yet clear, Cohen says. Having the automatic, fingers-level system answer to the higher system "has a sort of intuitive appeal," Cohen says, "but whether that idea is a convenience until we have a better idea or it's true remains to be seen.""
Posted: 28 Oct 2010 11:00 AM PDT
Nearly one in four sun-like stars should host an Earth-mass planet, according to a new census.
"It's a landmark paper," said exoplanet expert Josh Winn of MIT, who was not involved in the new study. "There's been all this talk, that low-mass planets like the Earth are very common. But this is the first time it's been documented."
The study, published in the Oct. 29 Science, also found plenty of planets in a mass range that astronomers expected to be empty, which may prompt an overhaul of planet-formation models.
Unlike previous surveys, Howard and colleagues were just as interested in stars that lack planets as stars that host them. To avoid biasing the study toward planet-bearing stars, the team selected the nearest and brightest stars in the 120,000-star Hipparcos Catalog.
"It's hard to write a telescope proposal that says, 'We want to look at these stars because we think they don't have planets,'" Howard said. "But that's what we had to do."
Over the course of five years, the team observed each star at least 20 times in search of planets that have masses between 3 and 1,000 times the Earth's mass and that orbit close to their stars.
They found 33 planets around 22 of the stars, some of which had already been discovered and reported by other groups, and 12 candidate planets that still need to be confirmed. Because some stars were observed more often than others, the team included a "missing-planet correction" to account statistically for planets that would probably show up with more observations.
None of these planets was actually the same mass as Earth. Astronomers' instruments aren't yet sensitive enough to detect such small worlds.
"But what we can do is extrapolate," Howard said. "It involves a little bit of speculation, but we're comfortable with that uncertainty."
In general, small planets turned out to be much more common than large ones. The researchers extended that trend down to planets about half Earth's mass.
They found that about 23 percent (give or take about 10 percent) of sun-like stars should have a planet between half and twice the Earth's mass orbiting very close in, about a quarter of the distance from the Earth to the sun. That distance would make the planets far too warm for liquid water. But because planets tend to be more abundant farther from their stars, Howard thinks there should be even more Earth-mass planets in cooler orbits where liquid water is stable.
"I wouldn't be surprised if the true number [of stars hosting Earth-mass planets] is one in two, or one in eight — but I'm almost sure it's not one in 100," he said. "That's a really big improvement on our knowledge."
Surprisingly, the observations also showed a lot of planets between 5 and 30 times Earth's mass, a range that theoretical models of planet formation predicted should be so empty it earned the name, "the planet desert."
"We showed that the desert is in fact closer to a tropical rain forest," Howard said.
The new numbers are a windfall to researches like Winn, who are involved in designing the next generation of planet-hunting telescopes.
"It sets our expectations much more clearly than they were last week," he said. "We were just guessing, to see how to design the instrument. Now we have some much more solid numbers to put in."
Exoplanet expert Sara Seager of MIT, who was not involved in the new study, noted that this is one of the first exoplanet papers that doesn't focus on just one planet or one system of planets.
"Exoplanet [research] is moving from single-planet characterization to statistics," she said. Thanks to the statistical treatment, Seager is more willing to accept uncertainties in Howard's analysis.
"You might not have confirmation of every individual planet, but that's OK," she said. "That shouldn't stop you from making general statements."
The study also prepares the way for the deluge of planets that should come from the Kepler Space Telescope in the next few years, she says. "We want the world to accept things from Kepler, but they have to be primed to believe that statistics are OK."
Image: 1) WMKO 2) NASA/JPL-Caltech/UC Berkeley
Posted: 28 Oct 2010 09:31 AM PDT
GLACIER NATIONAL PARK, Montana — As climate changes, some environments are becoming hostile to the flora and fauna that long nurtured them. Species that can migrate have begun to move into regions where temperatures and humidity are more hospitable. And that can prove a conundrum for officials charged with halting the invasion of non-native species, notes Jon Jarvis, a biologist who for the past year has headed the National Park Service.
One problem: What's native? Species move at will as conditions change. What's native in one century may be gone five generations later. Newly arrived species, meanwhile, may be environmental refugees.
"Policies that are currently in place view those [immigrants] as exotics," Jarvis says — invading homesteaders that should, at all costs, be evicted. But such species may be on the move simply "because this is their last efuge," he points out. "So we have to rethink that policy and how we respond to new species that are coming into our parks."
Each new immigrant has the potential to radically change the neighborhood — welcoming an influx of new predators and parasites, altering soil nutrients and porosity, even changing the amount of moisture and sunlight that reaches ground dwellers. And most of these changes can't be fully anticipated in advance.
Bottom line: With these migrations "we are going to be faced with very fundamental, difficult questions," Jarvis notes: Are the new arrivals weeds or endangered species to be welcomed with open arms?
One example — peccaries.
Jarvis was driving down the southern rim of Grand Canyon National Park a few months ago, when a group of piglike peccaries — also known as javelinas — crossed the road in front of him. The park's superintendent volunteered to Jarvis that "javelinas didn't used to be here." Although an American native, these animals are moving into novel, more-northerly locations, Jarvis observes. "And I think this is going to be true for a lot of species."
There is even talk, he says, about whether to help resettle some species into what for them will be novel sites. It may be the only way to ensure that threatened species survive into the next century, Jarvis told several dozen reporters who were touring Glacier National Park earlier this month.
For instance, much as they might like to, giant sequoias are not going to migrate. They have been literally rooted to their current ecosystem for millenniums. Today, he notes, "they are as iconic to the Sierra as glaciers are to Glacier [National Park]." But the sequoias are feeling the heat and not liking it.
So, he asks: "Are we, as a society, to move them — to plant them in the Cascades?" Actually, he acknowledges, "We're not quite ready to answer such questions. But we're beginning to have to face them."
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