Sharing All of The World

Previous research and first-hand reports suggest that humans have a harder time controlling physical movement and completing mental tasks in microgravity. Astronauts have experienced problems with balance and perceptual illusions -- feeling as if, for example, they are switching back and forth between right-side-up and upside down.
The Spaceflight Effects on Neurocognitive Performance: Extent, Longevity, and Neural Bases (NeuroMapping) study is examining changes in both brain structure and function and determining how long it takes to recover after returning from space.
Researchers are using both behavioral assessments and brain imaging. Astronauts complete timed obstacle courses and tests of their spatial memory, or the ability to mentally picture and manipulate a three-dimensional shape, before and after spaceflight. The spatial memory test also is performed aboard the station, along with sensory motor adaptation tests and computerized exercises requiring them to move and think simultaneously. Astronauts are tested shortly after arriving aboard the station, mid-way through and near the end of a six-month flight.
Structural and functional magnetic resonance imaging (MRI) scans of the brain are done pre-flight and post-flight.
"We are looking at the volume of different structures in the brain and whether they change in size or shape during spaceflight," said principal investigator Rachael D. Seidler, director of the University of Michigan's Neuromotor Behavior Laboratory.
Functional MRIs involve astronauts completing a task during the imaging, which will show researchers which parts of the brain they rely on to do so.
According to Seidler, both the behavioral assessment and brain imaging are important to help identify the relationship between physical changes in the brain and those in behavior.
"On Earth, your vestibular -- or balance -- system tells you how your head moves relative to gravity, but in space, the gravity reference is gone," Seidler said. "That causes these perceptual illusions, as well as difficulty coordinating movement of the eyes and head."
These difficulties could have serious consequences for astronauts, especially when changing between gravitational environments, such as landing on Mars. In those cases, astronauts will need to be able to perform tasks such as using tools and driving a rover, and they must be capable of escape in a landing emergency.
Identifying the physical mechanisms behind changes in behavior and how much time it takes to adapt will help researchers determine how best to help space explorers compensate. The study results could also reveal whether astronauts return to "normal" post-flight because the brain changes back, or if the brain instead learns to compensate for the changes that happened in space.
Scientists know that brain changes and adaptations happen here on Earth as well. As people age, for example, they use more brain networks than a younger person does to perform the same task. Chemotherapy, injury and illness also can trigger such adaptation. Co-investigator Patricia A. Reuter-Lorenz, chair of psychology at the University of Michigan, said a major benefit of this study is that the subjects are fit, healthy astronauts. That will make it possible to apply the findings across a range of causes.
Learning more about how the human brain changes in space will help scientists better understand the ways it can recover and adapt in space, and on Earth.
At least here on Earth, people can usually tell which way is up.

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The above post is reprinted from materials provided by NASA/Johnson Space Center. Note: Materials may be edited for content and length.

The Spanish explorer Vicente Yáñez Pinzón first reported the existence of the Coalsack Nebula to Europe in 1499. The Coalsack later garnered the nickname of the Black Magellanic Cloud, a play on its dark appearance compared to the bright glow of the two Magellanic Clouds, which are in fact satellite galaxies of the Milky Way. These two bright galaxies are clearly visible in the southern sky and came to the attention of Europeans during Ferdinand Magellan's explorations in the 16th century. However, the Coalsack is not a galaxy. Like other dark nebulae, it is actually an interstellar cloud of dust so thick that it prevents most of the background starlight from reaching observers.
A significant number of the dust particles in dark nebulae have coats of frozen water, nitrogen, carbon monoxide and other simple organic molecules. The resulting grains largely prevent visible light from passing through the cosmic cloud. To get a sense of how truly dark the Coalsack is, back in 1970, the Finnish astronomer Kalevi Mattila published a study estimating that the Coalsack has only about 10 percent of the brightness of the encompassing Milky Way. A little bit of background starlight, however, still manages to get through the Coalsack, as is evident in the new ESO image and in other observations made by modern telescopes.
The little light that does make it through the nebula does not come out the other side unchanged. The light we see in this image looks redder than it ordinarily would. This is because the dust in dark nebulae absorbs and scatters blue light from stars more than red light, tinting the stars several shades more crimson than they would otherwise be.
Millions of years in the future the Coalsack's dark days will come to an end. Thick interstellar clouds like the Coalsack contain lots of dust and gas -- the fuel for new stars. As the stray material in the Coalsack coalesces under the mutual attraction of gravity, stars will eventually light up, and the coal "nuggets" in the Coalsack will "combust," almost as if touched by a flame.

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The above post is reprinted from materials provided by ESO. Note: Materials may be edited for content and length.

In this new image of Jupiter a broad range of features has been captured, including winds, clouds and storms. The scientists behind the new images took pictures of Jupiter using Hubble's Wide Field Camera 3 over a ten-hour period and have produced two maps of the entire planet from the observations. These maps make it possible to determine the speeds of Jupiter's winds, to identify different phenomena in its atmosphere and to track changes in its most famous features.
The new images confirm that the huge storm, which has raged on Jupiter's surface for at least three hundred years, continues to shrink, but that it may not go out without a fight. The storm, known as the Great Red Spot, is seen here swirling at the centre of the image of the planet. It has been decreasing in size at a noticeably faster rate from year to year for some time. But now, the rate of shrinkage seems to be slowing again, even though the spot is still about 240 kilometres smaller than it was in 2014.
The spot's size is not the only change that has been captured by Hubble. At the centre of the spot, which is less intense in colour than it once was, an unusual wispy filament can be seen spanning almost the entire width of the vortex. This filamentary streamer rotates and twists throughout the ten-hour span of the Great Red Spot image sequence, distorted by winds that are blowing at 540 kilometres per hour.
There is another feature of interest in this new view of our giant neighbour. Just north of the planet's equator, researchers have found a rare wave structure, of a type that has been spotted on the planet only once before, decades ago by the Voyager 2 mission, which was launched in 1977. In the Voyager 2 images the wave was barely visible and astronomers began to think its appearance was a fluke, as nothing like it has been seen since, until now.
The current wave was found in a region dotted with cyclones and anticyclones. Similar waves -- called baroclinic waves -- sometimes appear in Earth's atmosphere where cyclones are forming. The wave may originate in a clear layer beneath the clouds, only becoming visible when it propagates up into the cloud deck, according to the researchers.
The observations of Jupiter form part of the Outer Planet Atmospheres Legacy (OPAL) programme, which will allow Hubble to dedicate time each year to observing the outer planets. In addition to Jupiter,Neptune and Uranus have already been observed as part of the programme and maps of these planets will be placed in the public archive. Saturn will be added to the series later. The collection of maps that will be built up over time will help scientists not only to understand the atmospheres of giant planets in the Solar System, but also the atmospheres of our own planet and of the planets that are being discovered around other stars.

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The above post is reprinted from materials provided by ESA/Hubble Information Centre. Note: Materials may be edited for content and length.

Sandia-induced changes elevate the plentiful, 37-cents-a-gram molly from being a welterweight outsider in the energy-catalyst field -- put crudely, a lazy bum that never amounted to much -- to a possible contender with the heavyweight champ.
The improved catalyst, expected to be the subject of an Oct. 7 Nature Communications paper, has already released four times the amount of hydrogen ever produced by molly from water.
To Sandia postdoctoral fellow and lead author Stan Chou, this is just the beginning: "We should get far more output as we learn to better integrate molly with, for example, fuel-cell systems," he said.
An additional benefit is that molly's action can be triggered by sunlight, a feature which eventually may provide users an off-the-grid means of securing hydrogen fuel.
Hydrogen fuel is desirable because, unlike gasoline, it doesn't release carbon into the atmosphere when burned. The combustion of hydrogen with oxygen produces an exhaust of only water.
In Chou's measured words, "The idea was to understand the changes in the molecular structure of molybdenum disulfide (MOS?), so that it can be a better catalyst for hydrogen production: closer to platinum in efficiency, but earth-abundant and cheap. We did this by investigating the structural transformations of MOS? at the atomic scale, so that all of the materials parts that were 'dead' can now work to make H? [hydrogen]."
The rind of an orange
in what sense were the parts "dead," one might ask?
Visualize an orange slice where only the rind of the orange is useful; the rest -- the edible bulk of the orange -- must be thrown away. Molly exists as a stack of flat nanostructures, like a pile of orange slices. These layers are not molecularly bolted together like a metal but instead are loose enough to slide over one another -- a kind of grease, similar to the structure of graphene, and with huge internal surface areas.
But here's the rub: While the edges of these nanostructures match platinum in their ability to catalyze hydrogen, the relative immense surface area of their sliding interiors are useless because their molecular arrangements are different from their edges. Because of this excess baggage, a commercial catalyst would require a huge amount of molly. The slender edges would work hard like Cinderella, but the stepsister interiors would just hang out, doing nothing.
Chou, who works on two-dimensional materials and their properties, thought the intent should be to get these stepsisters jobs.
Empowering the center
"There are many ways to do this," said co-author Bryan Kaehr, "but the most scalable way is to separate the nanosheets in solution using lithium. With this method, as you pull the material apart, its molecular lattice changes into different forms; the end product, as it turns out, is catalytically active like the edge structure."
To determine what was happening, and the best way to make it happen, the Sandia team used computer simulations generated by coauthor Na Sai from the University of Texas at Austin that suggested which molecular changes to look for. The team also observed changes with the most advanced microscopes at Sandia. including the FEI Titan, an aberration-corrected transmission electron microscope able to view atoms normally too small to see on most scopes.
"The extended test period made possible by the combined skills of our group allowed the reactions to be observed with the amount of detail needed," said Chou.
Lacking these tools, researchers at other labs had ended their tests before the reaction could complete itself, like a cook taking sugar and water off the stove before syrup is produced, resulting in a variety of conflicting intermediate results.
Ending confusion
"Why Stan's work is impactful is that there was so much confusion as to how this process works and what structures are actually formed," said Kaehr. "He unambiguously showed that this desirable catalytic form is the end result of the completed reaction."
Said Sandia Fellow and University of New Mexico professor Jeff Brinker, another paper author, "People want a non-platinum catalyst. Molly is dirt cheap and abundant. By making these relatively enormous surface areas catalytically active, Stan established understanding of the structural relation of these two-dimensional materials that will determine how they will be used in the long run. You have to basically understand the material before you can move forward in changing industrial use."
Kaehr cautions that what's been established is a fundamental proof of principle, not an industrial process. "Water splitting is a challenging reaction. It can be poisoned, stopping the molly reaction after some time period. Then you can restart it with acid. There are many intricacies to be worked out.
"But getting inexpensive molly to work this much more efficiently could drive hydrogen production costs way down."
'Green' inorganic photosynthesis
Not requiring electricity to prompt the reaction may be convenient in some circumstances and also keep costs down.
"A molly catalyst is essentially a 'green' technology," said Chou. "We used sunlight for the experiment's motive power. The light is processed through a dye, which harvests the light. A photocatalytic process stores that energy in the chemical bonds of the liberated hydrogen molecule.
"It's a kind of photosynthesis, but using inorganic materials rather than plants," Chou continued. "Plants use enzymes powered by sunlight to break up water into hydrogen and oxygen in a delicate process. We're proposing a similar thing here, but in a more rapid reaction and with sturdier components."
Kaehr said, "You could generate hydrogen and use it whenever. Hydrogen doesn't lose charge over time or suffer from conversion inefficiencies as do batteries in a solar car."
Other paper authors were Ping Lu, Eric Coker, Sheng Liu and Ting Luk, all from Sandia Labs, and Kateryna Artyushkova from the University of New Mexico.
The work was supported by the Department of Energy's Office of Science, and through its user facilities at the Sandia/Los Alamos-run Center for Integrated Nanotechnologies and National Energy Research Scientific Computing Center. The Texas Advanced Computing Center also added value.

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The above post is reprinted from materials provided by DOE/Sandia National Laboratories. Note: Materials may be edited for content and length.

AU Microscopii, or AU Mic for short, is a young, nearby star surrounded by a large disc of dust [1]. Studies of such debris discs can provide valuable clues about how planets, which form from these discs, are created.
Astronomers have been searching AU Mic's disc for any signs of clumpy or warped features, as such signs might give away the location of possible planets. And in 2014 they used the powerful high-contrast imaging capabilities of ESO's newly installed SPHERE instrument, mounted on the Very Large Telescope for their search -- and discovered something very unusual.
"Our observations have shown something unexpected," explains Anthony Boccaletti of the Observatoire de Paris, France, lead author on the paper. "The images from SPHERE show a set of unexplained features in the disc which have an arch-like, or wave-like, structure, unlike anything that has ever been observed before."
Five wave-like arches at different distances from the star show up in the new images, reminiscent of ripples in water. After spotting the features in the SPHERE data the team turned to earlier images of the disc taken by the NASA/ESA Hubble Space Telescope in 2010 and 2011 to see whether the features were also visible in these [2]. They were not only able to identify the features on the earlier Hubble images -- but they also discovered that they had changed over time. It turns out that these ripples are moving -- and very fast!
"We reprocessed images from the Hubble data and ended up with enough information to track the movement of these strange features over a four-year period," explains team member Christian Thalmann (ETH Zürich, Switzerland). "By doing this, we found that the arches are racing away from the star at speeds of up to about 40,000 kilometres/hour!"
The features further away from the star seem to be moving faster than those closer to it. At least three of the features are moving so fast that they could well be escaping from the gravitational attraction of the star. Such high speeds rule out the possibility that these are conventional disc features caused by objects -- like planets -- disturbing material in the disc while orbiting the star. There must have been something else involved to speed up the ripples and make them move so quickly, meaning that they are a sign of something truly unusual [3].
"Everything about this find was pretty surprising!" comments co-author Carol Grady of Eureka Scientific, USA. "And because nothing like this has been observed or predicted in theory we can only hypothesise when it comes to what we are seeing and how it came about."
The team cannot say for sure what caused these mysterious ripples around the star. But they have considered and ruled out a series of phenomena as explanations, including the collision of two massive and rare asteroid-like objects releasing large quantities of dust, and spiral waves triggered by instabilities in the system's gravity.
But other ideas that they have considered look more promising.
"One explanation for the strange structure links them to the star's flares. AU Mic is a star with high flaring activity -- it often lets off huge and sudden bursts of energy from on or near its surface," explains co-author Glenn Schneider of Steward Observatory, USA. "One of these flares could perhaps have triggered something on one of the planets -- if there are planets -- like a violent stripping of material which could now be propagating through the disc, propelled by the flare's force."
"It is very satisfying that SPHERE has proved to be very capable at studying discs like this in its first year of operation," adds Jean-Luc Beuzit, who is both a co-author of the new study and also led the development of SPHERE itself.
The team plans to continue to observe the AU Mic system with SPHERE and other facilities, including ALMA, to try to understand what is happening. But, for now, these curious features remain an unsolved mystery.
Notes
[1] AU Microscopii lies just 32 light-years away from Earth. The disc essentially comprises asteroids that have collided with such vigour that they have been ground to dust.
[2] The data were gathered by Hubble's Space Telescope Imaging Spectrograph (STIS).
[3] The edge-on view of the disc complicates the interpretation of its three-dimensional structure.

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The above post is reprinted from materials provided by ESA/Hubble Information Centre. Note: Materials may be edited for content and length.

The ideal clock is merely a convenient fiction, as theorists from the University of Warsaw (UW) and University of Nottingham (UN) have shown. In a study published in the journal Classical and Quantum Gravity they demonstrate that in systems moving with enormous accelerations, building a clock that would precisely measure the passage of time is impossible for fundamental reasons.
"In both theories of relativity, special and general, it is tacitly assumed that it is always possible to construct an ideal clock -- one that will accurately measure the time elapsed in the system, regardless of whether the system is at rest, moving at a uniform speed, or accelerating. It turns out, however, that when we talk about really fast accelerations, this postulate simply cannot apply," says Dr. Andrzej Dragan from the Faculty of Physics, University of Warsaw.
The simplest clocks are unstable elementary particles, for example muons (particles with similar properties to electrons but 200 times more massive). Usually, muons decay into an electron, muon neutrino, and an electron antineutrino. By measuring the decay times and averaging the results for muons moving slowly and those moving at nearly the speed of light, we can observe the famous slowing down of the passage of time: the faster the muons are moving, the less likely the experimenter is to see them decay. Velocity therefore affects the clocks' observed tempo.
What about acceleration? Experiments were performed at CERN in the late 1970s, measuring the decay time of muons undergoing circular motion accelerations even as great as billions of billions of times the acceleration of Earth's gravity (10^18 g). Such acceleration was found to have no impact on the disintegration times.
The Polish-British group of theorists from the universities of Warsaw and Nottingham, on the other hand, were looking at the description of unstable particles moving in accelerating motion in a straight line. The key point for their analysis turned out to be a fascinating effect predicted in 1976 by the Canadian physicist William Unruh.
"Contrary to intuition, the concept of a particle is not completely independent of the observer. We all know the Doppler Effect, for example, which causes a photon emitted by a moving source to appear bluer to an observer toward which the source is approaching, but redder to one it is receding from. The Unruh effect is somewhat similar, except that the results are more spectacular: in an certain area of space, a non-accelerating observer sees a quantum field vacuum, whereas an accelerating observer sees many particles," explains Dr. Dragan.
The equation describing the Unruh effect says that the number of particles visible within a quantum field varies depending on the acceleration experienced by an observer: the greater the acceleration, the more of them there are. These non-inertial effects may be due to the movement of the observer, but their source can also be a gravitational field. Interestingly, the Unruh effect is very akin to the famous Hawking radiation emitted by black holes.
The unstable particles which the physicists from the universities of Warsaw and Nottingham treated as a fundamental clocks in their analysis decay as a result of interactions with other quantum fields. The theory says that if such a particle remains in a space filled with a vacuum it decays at a different pace than when in the vicinity of many other particles interacting with it. Thus if in a system of extreme acceleration more particles can be seen as a result of the Unruh effect, the average decay times of particles such as muons should change.
"Our calculations showed that above certain very large accelerations there simply must be time disorders in the decay of elementary particles. And if the disturbances affect fundamental clocks such as muons, then any other device built on the principles of quantum field theory will also be disrupted. Therefore, perfectly precise measurements of proper time are no longer possible. This fact has further consequences, because losing the ability to accurately measure the passage of time also means problems with the measurements of distance," explains Dr. Dragan.
Until now it has been assumed that the concepts of time and space may lose their traditional senses only when certain phenomena predicted by hypothetical theories of quantum gravity begin to play a vital role. It is believed that the necessary conditions prevailed in the vicinity of the Big Bang.
"In our paper, we show that for problems with the measurements of space-time to arise, such extreme conditions are not needed at all. Time, and therefore space, most likely cease to be accurately measurable even in today's Universe, provided that we try to carry out the measurements in systems moving with great acceleration," notes Dr. Dragan.
The results from the physicists from Warsaw and Nottingham mean that at sufficiently high accelerations, the operational capabilities of any theory built on the notion of time, and thus also space, will be disrupted. This raises interesting questions. If in extremely accelerating systems we cannot build a clock that measures time accurately, is this exclusively a fundamental flaw in our measurement methods? Or maybe something is happening directly to time itself? And do properties which cannot be measured accurately even make physical sense?
Modern accelerators can accelerate particles with accelerations several orders of magnitude higher than in the experiments of the 70s. Thus today we can carry out experiments in which the Unruh effect should be visible -- and so changes in the decay time of particles triggered by acceleration should be observable, too. The conclusions of the Polish-British group of physicists on ideal clocks will thus soon be verified.
"If our predictions are confirmed experimentally, many things related to our understanding of space-time, the passage of time, and its measurement methods will have to be rethought from scratch. It could be... interesting," concludes Dr. Dragan with a smile.

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The above post is reprinted from materials provided by Faculty of Physics University of Warsaw. Note: Materials may be edited for content and length.

In an article published in the Oct. 5 issue of Physical Review Letters, a team of University of Chicago physicists explains how to tune a laser to make atoms attract or repel each other in an exotic state of matter called a Bose-Einstein condensate.
"This realizes a goal that has been pursued for the past 20 years," said Cheng Chin, professor in physics at the University of Chicago, who led the team. "This exquisite control over interactions in a many-body system has great potential for the exploration of exotic quantum phenomena and engineering of novel quantum devices."
Many research groups in the United States and Europe have tried various ideas over the last decade. It was Logan Clark, a graduate student in Chin's group, who came up with the first practical solution. He has now demonstrated the idea in the lab with cesium atoms chilled to temperatures just billionths of a degree above absolute zero, and the technique can be widely applied to other atomic species.
Clark compared the process to a billiards game, when one ball encounters another. "Normally, as soon as the surfaces touch, the balls repel each other and bounce away," Clark said. In Chin's lab, cesium atoms replace the billiard balls, and ordinarily they repel each other when they collide. But by turning up the laser while operating at a "magic" wavelength, Clark showed that the repulsion between atoms can be converted into attraction.
"The atoms exhibit fascinating behavior in this system," he said. By exposing different parts of the sample to different laser intensities, "We can choose to make the atoms attract or repel each other, or pass right through each other without colliding."
Alternatively, by oscillating their interactions, analogous to making the billiard balls rapidly grow and shrink while they roll, the atoms stick to each other in pairs.
The researchers explained two fundamental ways that lasers influence the atomic motion. One is to create potentials, like a bump or valley on the billiard table, proportional to laser intensity. The new way is to alter how billiard balls collide.
"We want our laser to control collisions, but we don't want it to create any hills or valleys," Clark said. When the laser is tuned to a "magic wavelength," the beam creates no hills or valleys, but only affects collisions.
"This is because the magic wavelength happens to be in between two excited states of the atom, so they 'magically' cancel each other out," he said.
Magic is a concept that has no place in science, though the word does enjoy fairly common use among atomic physicists. "Generally it is used to refer to a wavelength at which two effects cancel or are equal, in particular when this cancellation or equality is useful for some technological goal," Clark said.

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The above post is reprinted from materials provided by University of Chicago. Note: Materials may be edited for content and length.

This existential question has been raised by a series of experiments conducted recently at the Large Hadron Collider and the Relativistic Heavy Ion Collider that smash various atomic particles together at nearly the speed of light in order to create tiny drops of primordial soup: the quark-gluon plasma (QGP) that cosmologists are convinced dominated the universe microseconds after the Big Bang before the universe cooled down enough for atoms to form. In fact, the flow characteristic of these droplets is a major topic at a scientific conference, Quark Matter 2015, taking place this week in Kobe, Japan.
As part of the Large Hadron Collider's CMS detector team, Professor of Physics Julia Velkovska, post-doctoral fellow Shenguan Tuo and assistant research professor Shengli Huang at Vanderbilt University have been at the middle of these discoveries.
In 2010, the LHC successfully created sub-atomic blobs of QGP by colliding lead ions together. Smashing these two massive ions -- each containing hundreds of protons and neutrons -- had generated the tremendous temperatures, more than 250,000 times hotter than the core of the sun, that are required for the primordial state of matter to form.
(Unfortunately, the physicists don't have a direct way to measure the number of particles in the quark-gluon plasma, so they use the number of subatomic particles that are created when the plasma evaporates as a measure of their size.)
"Lead ions are very large, each containing hundreds of protons and neutrons. When you smash them together at very high speed, they generate blobs of plasma that produce thousands of particles when they cool down," said Velkovska. "But when the LHC switched to proton-lead ion collisions, we didn't think the collisions would contain enough energy to produce the plasma."
However, Tuo, as part of his doctoral thesis, made detailed measurements of the behavior of the particles produced by these smaller proton-lead collisions and discovered that they were in fact producing liquid droplets that were about one tenth the size of those produced in the lead-lead collisions.
"Everyone was surprised when we began finding evidence for liquid behavior," said Tuo. "It caused some very intense debates."
One of the key properties of a liquid is the ability to flow. Looked at from the point of view of the individual particles in a liquid, the ability to flow means that each particle is exerting an attractive force on its neighbors that is strong enough to effect their movement but not strong enough to lock them together like they are in a solid. So their movements are coordinated and, when released from a container, they retain information about the container's shape. Tuo's measurements showed that small numbers of particles produced in the proton-lead collisions originated on the ellipsoidal surfaces of small QGP droplets.
Because of the computational difficulty involved, physicists normally look for these correlations between pairs of particles, but Velkovska, Tuo and their CMS collaborators took it several steps further. They searched for correlations between groups of four, six and eight particles. In some cases, they went to the extraordinary length of computing the correlations between all the particles in a given collision.
"These measurements confirmed that we were seeing this coherent behavior even in droplets producing as few as 100 to 200 particles," Tuo said. The results were published in Physical Review Letters in June. But that wasn't the end of the story.
The recreation of the quark gluon plasma (QGP) dates back to 2005. Velkovska and her Vanderbilt colleagues -- physics professors Victoria Greene and Charlie Maguire -- were members of the PHENIX science team at RHIC, located at Brookhaven National Laboratory, when they announced that they had created this new state of matter by colliding gold ions together at relativistic velocities. The big surprise was that this primordial material behaved like a liquid, rather than a gas.
To see what happened at even higher energies, the Vanderbilt group joined the CMS science team at the LHC located at the European Laboratory for Nuclear and Particle Physics in Geneva. The more powerful particle collider succeeded in duplicating the RHIC results, first as expected, by smashing lead ions together and then, unexpectedly, in the proton-lead collisions.
The proton-lead results prompted the scientists in the PHENIX team to re-analyze data that had been collected at RHIC in 2000, when the collider had smashed deuterium ions (proton-neutron pairs) and gold ions together at much lower energies than those in the LHC. The re-analysis, led by Shengli Huang, found that the proton-neutron pairs formed two hot spots in the gold ion when they collided which then merged into an elongated drop of QGP.
The RHIC researchers decided to test this further by adding a new run that collided helium ions (two protons and a neutron) with gold ions, and found that the same thing happened, except that three hot spots formed and merged into the QGP droplet. The results were just published in Physical Review Letters.
"Although the LHC collisions release 25 times more energy than the RHIC collisions, we don't see much difference in the droplet-formation process: Once you have reached the threshold, adding more energy doesn't seem to have much effect," said Velkovska. "I guess you can't get more perfect than perfect!"
Not only have the physicists found that the quark-gluon plasma is a liquid, the physicists have also established that it is nearly a perfect liquid: That is a liquid with zero viscosity that flows without any resistance. If you swish a perfect liquid in a glass and set the glass down, then the liquid will continue to swirl around as long as it is not disrupted.
Curiously, the phenomenon that most closely resembles the properties of the hottest known liquid is one of the coldest known liquids: lithium atoms that have been cooled to temperatures one-billionth of a degree above absolute zero using a device called a laser trap. When released from the trap these ultra-cold atoms also behave as a perfect liquid with near-zero viscosity.
"These are both strongly coupled systems. This appears to be an emergent property of such systems," Velkovska has concluded.

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The above post is reprinted from materials provided by Vanderbilt University. Note: Materials may be edited for content and length.

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