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  • richardmitnick 9:14 am on October 17, 2019 Permalink | Reply
    Tags: "Physicists have found quasiparticles that mimic hypothetical dark matter axions", , , If axions exist as fundamental particles they could constitute a hidden form of matter in the cosmos- dark matter., Science News, The axions analogs within the crystal are a type of quasiparticle a disturbance in a material that can mimic fundamental particles like axions., The new study reveals for the first time that the phenomenon has a life beyond mere equations., , Within a crystal a wave of varying density of electromagnetic charge forms. When that wave slides back and forth it is mathematically equivalent to an axion.   

    From Science News: “Physicists have found quasiparticles that mimic hypothetical dark matter axions” 

    From Science News

    October 15, 2019
    Emily Conover

    1
    Scientists have spotted a solid matter analog to hypothetical subatomic particles called axions. Within a crystal, a wave of varying density of electromagnetic charge forms. When that wave slides back and forth, it is mathematically equivalent to an axion. sesame/DigitalVision Vectors/Getty.

    An elusive hypothetical particle comes in imitation form.

    Lurking within a solid crystal is a phenomenon that is mathematically similar to proposed subatomic particles called axions, physicist Johannes Gooth and colleagues report online October 7 in Nature.

    If axions exist as fundamental particles, they could constitute a hidden form of matter in the cosmos, dark matter. Scientists know dark matter exists thanks to its gravitational pull, but they have yet to identify what it is. Axions are one possibility, but no one has found the particles yet (SN: 4/9/18).

    Enter the imitators. The axions analogs within the crystal are a type of quasiparticle, a disturbance in a material that can mimic fundamental particles like axions. Quasiparticles result from the coordinated jostling of electrons within a solid material. It’s a bit like how birds in a flock seem to take on new forms by syncing up their movements.

    Axions were first proposed in the context of quantum chromodynamics — the theory that explains the behaviors of quarks, tiny particles that are contained, for example, inside protons. Axions and their new doppelgängers “are mathematically similar but physically totally unrelated,” says theoretical physicist Helen Quinn of SLAC National Accelerator Laboratory in Menlo Park, Calif., one of the scientists who formulated the theory behind axions. That means scientists are no closer to solving their dark matter woes.

    Still, the new study reveals for the first time that the phenomenon has a life beyond mere equations, in quasiparticle form. “It’s actually amazing,” says Gooth, of the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany. The idea of axions is “a very mathematical concept, in a sense, but it still exists in reality.”

    In the new study, the researchers started with a material that hosts a type of quasiparticle known as a Weyl fermion, which behaves as if massless (SN: 7/16/15). When the material is cooled, Weyl fermions become locked into place, forming a crystal. That results in the density of electrons varying in a regular pattern across the material, like a stationary wave of electric charge, with peaks in the wave corresponding to more electrons and dips corresponding to fewer electrons.

    Applying parallel electric and magnetic fields to the crystal caused the wave to slosh back and forth. That sloshing is the mathematical equivalent of an axion, the researchers say.

    To confirm that the sloshing was occurring, the team measured the electric current through the crystal. That current grew quickly as the researchers ramped up the electric field’s strength, in a way that is a fingerprint of axion quasiparticles.

    If the scientists changed the direction of the magnetic field so that it no longer aligned with the electric field, the enhanced growth of the electric current was lost, indicating that the axion quasiparticles went away. “This material behaves exactly as you would expect,” Gooth says.

    See the full article here .


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  • richardmitnick 12:16 pm on October 3, 2019 Permalink | Reply
    Tags: , Monika Schleier-Smith, , Science News   

    From Science News: “Monika Schleier-Smith leads elaborate quantum conversations” 

    From Science News

    October 2, 2019
    Elizabeth Quill

    The fussy experimental work could be a boon for timekeeping and computing.

    “I like it if I can run uphill and be rewarded with a view of the bay,” says Monika Schleier-Smith.

    1
    Monika Schleier-Smith combines persistence and clarity of vision to do impressive experimental work. Dawn Harmer/SLAC National Accelerator Laboratory.

    She’s talking about a favorite spot to exercise around Palo Alto, Calif., but the sentiment also applies to her scientific work. A physicist at Stanford, Schleier-Smith, 36, has a reputation for embracing the uphill climb. She’ll push, push, push the smallest details of an experiment until she achieves what others thought near impossible.

    Her reward? Seeing large ensembles of atoms do her bidding and interact with one another over distances that are incredibly vast, at least for the quantum realm.

    “She tends to persist,” says Harvard physicist Susanne Yelin, who follows Schleier-Smith’s research. She gets results, even though “everything that exists in nature” is working against her experiments.

    Quantum physics describes a microworld where many possibilities reign. Unobserved atoms and particles don’t have clearly defined locations, and information can be shared by widely spaced parts of a system. “We have equations that describe quantum mechanics well, but we can’t solve them when we are dealing with more than a few particles,” Schleier-Smith says.

    That’s a shame, because understanding how large numbers of these small entities interact is essential to figuring out how our world works at the most fundamental level. Getting atoms to behave in just the right ways also has some practical benefits. It could lead to the most precise clocks yet, a boon for precision measurement, and to quantum computers that can solve problems that are too hard for today’s supercomputers.

    Schleier-Smith’s experimental setups use elaborate tabletop arrangements of mirrors, lasers, vacuum chambers and electronic parts to cool atoms, pin them in place and then manipulate them with light. It’s a clutter of essential components, the construction of which requires an exacting understanding of the physics at play plus engineering know-how.

    3
    Monika Schleier-Smith and her team trap cold atoms between two mirrors (shown). The setup allows the team to image the atoms.Schleier-Smith Lab

    As a graduate student at MIT, Schleier-Smith worked with a small team that pushed the precision of an atomic clock beyond what’s known as the “standard quantum limit,” a result reported in 2010 [Physical Review Letters]. Though people knew this was theoretically possible, many thought it was too hard to try to pull off. Schleier-Smith spent weeks optimizing and troubleshooting the control circuitry that kept the experiment’s lasers at the right frequency, says Ian Leroux, who was on the MIT team and is now at Canada’s National Research Council Metrology Research Centre in Ottawa. She has “that blend of care, dexterity, observation and attention to detail that lets her make an apparatus work better than it has any right to.”

    In a more recent experimental feat, reported in January in Physical Review Letters, Schleier-Smith and her Stanford team used laser light to create long-distance interactions in a cloud of some 100,000 cold rubidium atoms. The atoms chatted up other atoms half a millimeter away — a great distance for atoms. At Schleier-Smith’s direction, an excitation in the atoms, in this case a flip in a property called spin, hopped from one side of the atom cloud to another, using a photon to bypass the atoms in between. What’s more, the team found a way to image that hopping.

    5
    In a recent experiment, an excitation in trapped atoms, in this case a flip in a property called spin, was observed hopping across the atom cloud. The three cigar shapes show the hopping in a single cloud (spin states +1, -1 and 0, from top to bottom).Schleier-Smith Lab

    Schleier-Smith traces her interest in physics back to high school, when a chemistry teacher told her to think of an electron as “spread out like peanut butter.” The idea fascinated her. She sensed that a deeper understanding meant studying quantum mechanics.

    It’s not an insight you’d expect from the average high schooler. But such clarity of vision has been a characteristic of Schleier-Smith’s work.

    She quickly identifies ideas that are both interesting and experimentally feasible, says graduate student Emily Davis, who has worked in Schleier-Smith’s lab since 2013. (About half of the current lab members are female, atypical in such a male-dominated field.)

    “I tend to be fairly intuitive,” Schleier-Smith says. “I think it is a matter of how my brain works.”

    And she readily sees through other scientists’ questionable assumptions, Leroux says. With a cloud of thousands of atoms, her spin-hopping setup bucks a commonsense argument that you need to hold atoms in a very small space to get good control of their electromagnetic interactions.

    That setup might also have value in studying black holes. Theories that attempt to connect quantum physics with Albert Einstein’s theory of gravity — general relativity — lead to specific predictions about what happens to information that falls into black holes. The information might get mixed up exponentially quickly through long-range interactions analogous to those Schleier-Smith has demonstrated.

    “She has built an exceptionally powerful platform for exploring these phenomena in the lab,” says Stephen Shenker, a theoretical physicist at Stanford who works at the intersection of quantum physics and gravity.

    Could pursuing connections to black holes reveal something interesting about how atoms interact, as well as how to control those interactions? Schleier-Smith can’t say for sure, but she sees the potential.

    See the full article here .


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  • richardmitnick 11:38 am on October 3, 2019 Permalink | Reply
    Tags: "Brett McGuire searches space for the chemistry of life", , , , , , , , , Science News   

    From Science News: “Brett McGuire searches space for the chemistry of life” 

    From Science News

    October 2, 2019
    Lisa Grossman

    Cosmic molecules may point to the origins of carbon-based life.

    In a different reality, space might smell like almonds. After all, scientists surveying the chemicals in the cosmos have found benzonitrile; just a bit of the compound would fill your nostrils with a bitter almond scent.

    But our cosmos is too vast. “Space smells like nothing,” says astrochemist Brett McGuire. “There’s not enough to get an actual whiff.”

    2
    Astrochemist Brett McGuire combines skills in chemistry and astronomy to search for complex molecules in space. Courtesy of B. McGuire

    McGuire, 32, of the National Radio Astronomy Observatory in Charlottesville, Va., confirmed the presence of benzonitrile in a dark cloud in the Milky Way. He also discovered some of the other most complex molecules in space to date. By figuring out which molecules are out there, he and others hope to learn how the organic chemistry that undergirds all life on Earth — and perhaps anywhere else in the universe — gets started in space.

    McGuire got his start in space as an undergraduate chemistry major at the University of Illinois at Urbana-Champaign. During a talk, Ben McCall, now a sustainability expert at the University of Dayton in Ohio, explained what he does for a living. He said something like, “I blow shit up, torture it with lasers and then I look for it in space,” McGuire recalls.

    Enough said. McGuire spent that summer working in McCall’s lab, building a spectrometer to study how hydrogen gas, H2, reacts with H3+ — three hydrogen atoms with only two electrons. Some of McCall’s research included zapping gases of simple molecules with electricity — “an actual miniature lightning bolt,” McGuire says — to force atoms to recombine into new compounds that can’t be bought in a bottle.

    “Brett was a very precocious young scientist,” McCall says. “This was the only time I’ve had a student who really started a new instrument from scratch as an undergrad.”

    3
    The discovery of benzonitrile in a dust cloud in the Milky Way suggests that complex molecules can form from the buildup of smaller molecules in space. (Carbon is black, hydrogen white and nitrogen blue.) Ben Mills and Jynto/Wikimedia Commons

    Because space is so big and mostly empty, at least by Earth standards, it can take millions of years for two molecules flying around like billiard balls to get close enough to interact. “But it’s not just neutral billiard balls out there,” McGuire says. A charged molecule, like H3+, which has been discovered in interstellar space, can pull other molecules closer. “More or less all chemistry in space can trace itself back to H3+ at some point.”

    And all that chemistry includes some tantalizingly lifelike stuff. In 2016, McGuire and colleagues reported discovering propylene oxide in a gas cloud within the Milky Way.

    4
    MOLECULE CLUE A gas cloud (Sagittarius B2) near the center of the galaxy (Sagittarius A*) is loaded with propylene oxide, a molecule that comes in mirror-image configurations. B. Saxton, NRAO/AUI/NSF from data provided by N.E. Kassim, Naval Research Laboratory, Sloan Digital Sky Survey.

    That was the first molecule seen in space that, like the amino acids that make up proteins and are essential to life on Earth, has two forms that are mirror images of each other. Large rings of carbon and hydrogen, called polycyclic aromatic hydrocarbons, or PAHs, have also been spotted around dead or dying stars — though it’s been hard to tell how many carbons and hydrogens the PAHs contain.

    PAHs are thought to be the seeds of dust, planets and organic chemistry in our galaxy and other galaxies, McGuire says. So how do they form? “How do you go from H3+ to things that literally click together to make the building blocks of life?” he asks.

    The work of enumerating what’s out there mostly takes place in a lab on Earth. McGuire injects a puff of gas of the molecule he’s interested in into a large vacuum chamber, where the low temperature and pressure make the gas expand. Then he hits the gas with a pulse of intense microwave or radio radiation, sending the molecules tumbling. As they tumble, the molecules emit photons at a specific frequency. That light signature, called the molecule’s rotational spectrum, is what McGuire looks for when he searches for those molecules in space.

    Once McGuire knows the molecular fingerprint he’s after, he turns to radio telescopes to find the same print in space. Many scientists focus on one branch of this process or the other, the laboratory spectroscopy or the interstellar astronomy; only a few have expertise in both. “Brett is one of those very few people,” McCall says.

    To sniff almonds in space, McGuire and colleagues focused the Robert C. Byrd Green Bank Telescope in West Virginia on TMC-1, a dark cloud about 450 light-years from Earth “where maybe there are stars that are considering starting to form,” McGuire says. Forty hours of observing confirmed that benzonitrile, a benzene ring with a cyanide molecule stuck on the end, was there [Science].

    Green Bank Radio Telescope, West Virginia, USA, now the center piece of the GBO, Green Bank Observatory, being cut loose by the NSF

    6
    Scientists have detected complex molecules in TMC-1, a stellar nursery in the Milky Way. The cloud lacks big, bright stars, and its dust grains glow only faintly (shown in orange). ESO

    Lately, McGuire and colleagues are closing in on a bigger prize: specific PAHs in the space between stars. Knowing the makeup of PAHs in space will help reveal how they click together from smaller molecules, McGuire says. Finding these molecules would show that advanced chemistry is happening, in some cases before stars begin forming.

    Benzonitrile and the more complex molecules it hints at are “the first clear marker” of carbon-based chemistry in space, says Ryan Fortenberry, an astrochemist at the University of Mississippi in Oxford who wasn’t involved in the benzonitrile finding. “Before this, we were just kind of wandering around in the wilderness,” Fortenberry says. “Now we have found the trail.”

    See the full article here .


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  • richardmitnick 9:24 am on September 17, 2019 Permalink | Reply
    Tags: , , , , , , , Ringing black holes, Science News   

    From Science News: “Gravitational waves from a ringing black hole support the no-hair theorem” 

    From Science News

    September 16, 2019
    Emily Conover

    General relativity suggests the spacetime oddities can be fully described by their mass and spin.

    1

    After two black holes collide and meld into one, the new black hole “rings” (illustrated), emitting gravitational waves before settling down into a quiet state. M. Isi/MIT, NASA

    For black holes, it’s tough to stand out from the crowd: Donning a mohawk is a no-no.

    Ripples in spacetime produced as two black holes merged into one suggest that the behemoths have no “hair,” scientists report in the Sept. 13 Physical Review Letters. That’s another way of saying that, as predicted by Einstein’s general theory of relativity, black holes have no distinguishing characteristics aside from mass and the rate at which they spin (SN: 9/24/10).

    “Black holes are very simple objects, in some sense,” says physicist Maximiliano Isi of MIT.

    Detected by the Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, in 2015, the spacetime ripples resulted from a fateful encounter between two black holes, which spiraled around each other before crashing together to form one big black hole (SN: 2/11/16).

    MIT /Caltech Advanced aLigo

    In the aftermath of that coalescence, the newly formed big black hole went through a period of “ringdown.” It oscillated over several milliseconds as it emitted gravitational waves, similar to the way a struck bell vibrates and makes sound waves before eventually quieting down.

    Reverberating black holes emit gravitational waves not at a single frequency, but with additional, short-lived frequencies known as overtones — much like a bell rings with multiple tones in addition to its main pitch.

    Measuring the ringing black hole’s main frequency as well as one overtone allowed the researchers to compare those waves with the prediction for a hairless black hole. The results agreed within 20 percent.

    That result still leaves some wiggle room for the no-hair theorem to be proved wrong. But, “It’s a clear demonstration that the method works,” says physicist Leo Stein of the University of Mississippi in Oxford, who was not involved with the research. “And hopefully the precision will increase as LIGO improves.”

    The researchers also calculated the mass and spin of the black hole, using only waves from the ringdown period. The figures agreed with the values estimated from the entire event — including the spiraling and merging of the original two black holes — and so reinforced the idea that the resulting black hole’s behavior was determined entirely by its mass and spin.

    But just as a mostly bald man may sport a few strands, black holes could reveal some hair on closer inspection. If they do, that might lead to a solution to the information paradox, a puzzle about what happens to information that falls into a black hole (SN: 5/16/14). For example, in a 2016 attempt to resolve the paradox, physicist Stephen Hawking and colleagues suggested that black holes might have “soft hair” (SN: 4/3/18).

    “It could still be that these objects have more mysteries to them that will only be revealed by future, more sensitive measurements,” Isi says.

    See the full article here .


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  • richardmitnick 9:21 am on September 3, 2019 Permalink | Reply
    Tags: , , Science News, Scientists have calculated that a hydrogen-rich compound could conduct electricity without resistance at temperatures up to about 200° Celsius., , The newly predicted superconductor — a compound of hydrogen; magnesium; and lithium — comes with its own complications however., The proposed superconductor must be squeezed to extremely high pressure nearly 2.5 million times the pressure of Earth’s atmosphere.   

    From Science News: “A predicted superconductor might work at a record-breaking 200° Celsius” 

    From Science News

    August 30, 2019
    Emily Conover

    1
    A theoretical type of superconductor, made of atoms of lithium (illustrated in green), magnesium (blue) and hydrogen (red), could function even at temperatures above the boiling point of water, scientists say. H. Liu

    The hydrogen-rich material would still need to be squeezed to extremely high pressures.

    Scientists have calculated that a hydrogen-rich compound could conduct electricity without resistance [Physical Review Letters] at temperatures up to about 200° Celsius — well above the 100° C boiling point of water. If that prediction is confirmed experimentally, the material would stand in stark contrast to all other known superconductors, which must be cooled below room temperature to work (SN: 12/15/15).

    The newly predicted superconductor — a compound of hydrogen, magnesium and lithium — comes with its own complications, however. It must be squeezed to extremely high pressure, nearly 2.5 million times the pressure of Earth’s atmosphere, physicist Hanyu Liu and colleagues, of Jilin University in Changchun, China, report in the Aug. 30 Physical Review Letters [link above].

    Scientists previously have used similar techniques to predict that a pressurized compound of lanthanum and hydrogen would be superconducting at higher temperatures than any yet known. That prediction seems likely to be correct: In 2018, physicist Russell Hemley and colleagues reported signs that the compound is superconducting up to a record-breaking −13° C (SN: 9/10/18).

    If the new calculation is confirmed, the purported superconductor would smash Hemley and colleagues’ temperature record. “This is an important prediction using a level of theory that has proven quite accurate,” says Hemley, of the University of Illinois at Chicago, who was not involved in the research.

    See the full article here .


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  • richardmitnick 10:32 am on August 18, 2019 Permalink | Reply
    Tags: "Totalitarian principle", Another hypothetical particle permitted by the laws of physics- the neutrino-did eventually turn up after nuclear reactors produced the particles copiously enough to enable their detection., , “Principle of plenitude”, “What is considered physically or genuinely possible” Kragh writes “depends on the best scientific knowledge at any given time.”, , Equations are precisely stated descriptions of nature’s behavior that enable scientists to make accurate predictions about how things happen in the world., Everything not forbidden is compulsory., Failure to find magnetic monopoles led to investigations that produced the theory of cosmic inflation- the best current explanation of the early history of the universe., Helge Kragh-confusions posed by the totalitarian principle., In science the official rulebook consists of the laws of nature., , One example of plenitude reasoning in physics (without naming it that) came from Paul Dirac the physicist who in 1931 predicted the existence of half magnets. He called them magnetic monopoles., , Plato believed that all possible ideal “forms” should actually exist in physical reality., Science News, Science’s unwritten rules aren’t strict. They are merely guidelines: suggestions for how best to play the game but without the totalitarian force of true natural law., Subsequent searches have failed to find monopoles., Whatever can exist does exist, Whatever the laws of nature allow must in fact exist or happen.   

    From Science News: “Murray Gell-Mann’s ‘totalitarian principle’ is the modern version of Plato’s plenitude’ 

    From Science News

    August 18, 2019
    Tom Siegfried

    Idea that whatever can exist does exist can guide scientific pursuits.

    1
    Plato’s principle of plenitude is reborn in the modern belief, credited to Murray Gell-Mann (right), that whatever can exist must exist. Left: © Marie-Lan Nguyen/Wikimedia Commons (CC-BY 2.5); Right: Joi/Wikimedia Commons (CC-BY 2.5)

    Science, like baseball, has a lot of unwritten rules.

    Every baseball player knows that you don’t flip your bat after hitting a home run, you never steal a base when you have a big lead, and you cover your mouth with your glove when having a conference on the mound. None of those regulations are codified in the official rules — it’s just how pros play the game.

    In science, the official rulebook consists of the laws of nature — equations or otherwise precisely stated descriptions of nature’s behavior that enable scientists to make accurate predictions about how things happen in the world. Science’s unwritten rules aren’t so strict. They are merely guidelines, suggestions for how best to play the game but without the totalitarian force of true natural law.

    One such less-than-totalitarian principle is known as the … totalitarian principle. It is commonly expressed as “whatever is not forbidden is compulsory.” In other words, whatever the laws of nature allow must, in fact, exist or happen.

    That sounds a little bit like the opposite of totalitarianism, which would seem to require doing only what is compulsory, with everything else forbidden. And that’s just one of the confusions posed by the totalitarian principle discussed in a new paper by the historian Helge Kragh.

    Kragh notes that the origin of the totalitarian principle in physics is usually attributed to Murray Gell-Mann, the Nobel laureate who died in May at the age of 89. But many sources, Kragh notes, claim that Gell-Mann borrowed the phrasing from T.H. White, author of the King Arthur story The Sword in the Stone.

    True enough, White used the phrase “everything not forbidden is compulsory” in The Sword in the Stone; it was on signs above tunnel entrances in an ant colony. But that ant colony appeared only in the 1958 edition of The Once and Future King, in which The Sword in the Stone was incorporated. Nothing like the totalitarian principle phrasing was found in previous versions, Kragh reports.

    Yet Gell-Mann first described the idea in 1956, two years earlier. In a paper concerned with new particles and the strong nuclear force, Gell-Mann asserted that for some particles “any process which is not forbidden by a conservation law actually does take place.” He called it an assumption that “is related to the state of affairs that is said to prevail in a perfect totalitarian state. Anything that is not compulsory is forbidden.”

    Kragh doesn’t think Gell-Mann articulated the principle very clearly. For one thing, he was talking only about the strong force. And though he described his idea as related to totalitarianism, he had inverted the phrasing. So Kragh suggests that Gell-Mann doesn’t really deserve credit for originating the idea. Nevertheless, subsequent physicists often attributed the principle to Gell-Mann and sometimes labeled it as totalitarian. A 1969 paper, for instance, mentioned “an unwritten precept in modern physics, often facetiously referred to as Gell-Mann’s totalitarian principle, which states that in physics ‘anything which is not prohibited is compulsory.’”

    In any case, the underlying idea definitely did not originate with Gell-Mann. It rather descends from the philosophy of Plato, who believed that all possible ideal “forms” should actually exist in physical reality. In the 1930s, philosopher-historian Arthur Lovejoy referred to that idea as the “principle of plenitude” and discussed how it had been applied by other philosophers throughout history. But while the plenitude principle’s influence was widely recognized in biology, its use by physicists seems relatively recent. Kragh suggests that the totalitarian principle is in essence the successor of the plenitude principle “specially adapted to modern physics.”

    One example of plenitude reasoning in physics (without naming it that) came from Paul Dirac, the physicist who in 1931 predicted the existence of half magnets. (He called them magnetic monopoles — magnets with only a single pole, not both a north and a south.) Dirac’s quantum equations seemed to allow particles with a single magnetic pole to exist, and so, he decided, they probably did.

    Subsequent searches have failed to find monopoles. But another hypothetical particle permitted by the laws of physics, the neutrino, did eventually turn up after nuclear reactors produced the particles copiously enough to enable their detection.

    When Gell-Mann first mentioned the totalitarian principle, he recognized that depending on it posed a danger: Maybe there are laws you don’t know about. Thus the totalitarian principle offers physicists a two-sided blade. One, it suggests that if you discern that something is not forbidden, it’s a good idea to design an experiment to look for it. Two, if you look for it but don’t find it, then maybe that’s a sign that there’s some previously unknown law of nature that prevents it, and you should begin theoretical inquiries to look for the missing law. Kragh cites the discovery of baryon conservation in the 1950s as a consequence of failure to detect the decay of certain particles called baryons.

    Similarly, failure to find magnetic monopoles led to investigations that produced the theory of cosmic inflation, the best current explanation of the early history of the universe. (Inflation indicates that monopoles very well could exist but that the rapid expansion of space in the early universe diluted their concentration so much that we would be unlikely to encounter one in our neighborhood today.)

    In spite of such fruitful results from applying the totalitarian principle, it remains a mere guideline for scientific pursuits, not a guarantee of success. For one thing, it might not imply that anything that can exist does exist now — perhaps some possible things will come into existence only in the future. And saying that anything that’s possible must exist is inherently ambiguous because of the fuzzy meaning of the word possible. You never really know for sure what’s possible and what isn’t.

    “What is considered physically or genuinely possible,” Kragh writes, “depends on the best scientific knowledge at any given time.”

    See the full article here .


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  • richardmitnick 9:14 am on August 15, 2019 Permalink | Reply
    Tags: , , , , , , Science News   

    From Science News: “Astronomers just quintupled the number of known repeating fast radio bursts” 

    From Science News

    August 14, 2019
    Lisa Grossman

    The find could help reveal what causes these cryptic flashes of radio waves from deep space.

    1
    CONSTANT VIGILANCE A Canadian telescope called CHIME scans the sky each night for brief, bright bursts of cosmic radio waves. Now CHIME has spotted eight new bursts that flash over and over. Andre Renard/Dunlap Institute/University of Toronto/CHIME

    Astronomers have found eight new fast radio bursts that repeatedly flash on and off.

    That haul brings the total of known repeating fast radio bursts, or FRBs, to 10, compared with the 60 or so nonrepeating FRBs that have been spotted, researchers report August 9 at arXiv.org [Astrophysical Journal Letters]. Studying the cryptic bursts could reveal what phenomena cause these brief, brilliant flares of radio waves from deep space.

    The first nonrepeating burst was discovered only in 2007, so “FRBs are still quite new,” says astrophysicist Cherry Ng of the University of Toronto. But “the repeater population is larger than we might think. They’re not that unique,” she says.

    Ng and colleagues spotted the newly discovered repeating FRBs using the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, in British Columbia. The telescope also found the second known repeating FRB in August 2018 (SN: 2/2/19, p. 12).

    The new batch of repeat bursts could help astronomers start to figure out the sources of these flashes of radio energy, as well as how they might be different from their nonrepeating kin.

    For instance, radio waves from the first known repeat FRB, reported in 2016, were scrambled and tossed around by electrons on the way to Earth. That suggests the repeating FRB’s source is in a dense, turbulent environment, such as a supernova remnant or a neutron star orbiting a black hole (SN: 2/3/18, p. 6). But the energy from some of the new bursts seems to have had a less tumultuous journey, suggesting that these repeating FRBs hail from a calmer environment.

    Each burst from a repeat FRB also seems to last longer than an individual FRB, about 10 milliseconds per repeat burst versus one millisecond for a nonrepeater. That finding could support the idea that the two types of radio blasts have entirely different sources, although Ng thinks it’s too soon to be sure (SN: 8/3/19, p. 10). “Maybe don’t bet too much money on it,” she says.

    CHIME also has found many more nonrepeating FRBs in the last year, Ng says. That research is yet to be published, but “it will be a game changer,” she says.

    See the full article here .


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  • richardmitnick 11:40 am on August 2, 2019 Permalink | Reply
    Tags: "Stars may keep spinning fast, , , , , long into old age", , Science News   

    From Science News: “Stars may keep spinning fast, long into old age” 

    From Science News

    August 2, 2019
    Lisa Grossman

    The idea that older stars continually slow their rotation may be wrong.

    1
    SLOWDOWN Sunlike stars start as fast-spinning balls of gas (illustrated at left). As this type of star ages, its spin slows and it puffs up, before dying as a nebula (middle and right). But the spin of these aging stars might not slow as much as thought. S. Steinhöfel/ESO

    Stars may keep some of their youthful vigor as they age. Astronomers have spotted a star in its twilight years that spins much faster than expected. The discovery supports a new idea that, rather than continually slowing with age, some stars may have a magnetic midlife crisis that keeps them on a roll.

    “This process of slowing rotation … that we assumed happened indefinitely over the lifetime of a star may be interrupted in the middle of a star’s life,” says astronomer Travis Metcalfe of the Space Science Institute in Boulder, Colo. He presented new measurements of the star’s age July 30 at the first TESS Science Conference.

    The star, 94 Aquarii Aa, is a member of a triple-star system in the constellation Aquarius about 69 light-years from Earth. Its color and brightness suggest that it’s in the part of a star’s life cycle called the subgiant stage, which happens near the end of a sunlike star’s life as it starts running out of fuel.

    But it’s difficult to pinpoint a star’s age. Theories of stellar evolution predict that young stars rotate quickly but slow as they age and lose angular momentum, a process called spinning down. So astronomers often use a star’s spin rate to estimate age.

    Recently, though, data have emerged that raise questions about whether that aging scenario is correct.

    NASA’s Kepler space telescope, which watched distant stars for signs of orbiting planets from 2009 to 2018 (SN Online: 10/30/18), tracked how oscillations, or “starquakes,” ripple through a star’s interior, a technique called asteroseismology.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    Those ripples’ speeds are closely linked to the star’s mass and interior structure. Structure changes over the course of a star’s life, so asteroseismology is a good way to estimate a star’s age. In 2016, Metcalfe and colleagues reported in Nature that Kepler was finding old stars that rotated too fast for their ages. Young stars followed the spin-down trends, but around middle age, stars’ spin speed leveled off.

    As an aging subgiant, 94 Aquarii Aa made a good test case, Metcalfe said. He used NASA’s Transiting Exoplanet Survey Satellite, or TESS, the successor to Kepler, to estimate the star’s age and mass using asteroseismology. It’s about 6.2 billion years old, he found, and 1.2 times the mass of the sun. (In comparison, the sun is 4.5 billion years old.)

    If it had been spinning down its whole life, a star of that mass should now be rotating once every 78 days. But previous measurements made from ground-based telescopes had shown that the star rotates once every 47 days.

    “The only way to explain a star of that age having that rotation period is that this stalled rotation has to kick in around middle age,” Metcalfe says. “It’s a smoking gun.” He hopes to repeat the experiment with hundreds of more stars over the course of the TESS mission.

    Stars might stop slowing their rotation because of a midlife change in their magnetic field. A star’s magnetic field drives its stellar wind, which carries mass and angular momentum away from the star, contributing to its slowdown (SN Online: 7/29/19). But if the magnetic field changes its geometry around the middle of a star’s life, shifting from dominating the entire star to a more small-scale field, that could weaken the magnetic field’s control over the star’s rotation, Metcalfe says.

    “This is the first time we’ve seen convincing evidence that you have to invoke [the stalled slowdown] to explain the rotation of a subgiant,” says Jason Curtis, an astronomer at Columbia University. Astronomers had a lot of skepticism about Metcalfe and colleagues’ previous work using Kepler data, he says, but “every time they look at it from a different angle, it becomes more convincing.”

    Unfortunately, the result might mean that astronomers can’t use stars’ spin speeds to guess ages anymore. “If that stops working in old stars, that’s a bummer,” Curtis says.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 5:20 pm on July 29, 2019 Permalink | Reply
    Tags: “We’re not re-creating the sun because that’s impossible” says plasma physicist Ethan Peterson of the University of Wisconsin–Madison. “But we’re re-creating some of the fundamental phys, , NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker, Parker spiral named after solar physicist Eugene Parker who predicted the existence of the solar wind in 1958., , , Science News, , The magnet in the center of the ball mimics the sun’s magnetic field and carefully applied electric currents send the plasma spinning and a wind streaming., The sun spews a constant stream of charged particles-called the solar wind out into space - though scientists aren’t sure exactly how., The team used a 3-meter-wide aluminum vacuum chamber called the Big Red Ball heated to 100000° Celsius at the Wisconsin Plasma Physics Laboratory.,   

    From University of Wisconsin Madison via Science News: “In a first, physicists re-created the sun’s spiraling solar wind in a lab” 

    U Wisconsin

    From University of Wisconsin Madison

    via

    Science News

    July 29, 2019
    Lisa Grossman

    Some of the sun’s fundamental physics have been re-created with plasma inside a vacuum chamber.

    1
    SUN IN A BALL This view shows the inside of the Big Red Ball, a 3-meter-wide aluminum sphere at the University of Wisconsin–Madison that can mimic properties of the sun. Carefully applied magnets and electric currents make the plasma spin and send out streams of charged particles, like the solar wind. Univ. of Wisconsin-Madison

    Physicists have created mini gusts of solar wind in the lab, with hopes that the charged particle streams can help to resolve some mysteries about our nearest star [Nature Physics].

    “We’re not re-creating the sun, because that’s impossible,” says plasma physicist Ethan Peterson of the University of Wisconsin–Madison, who reports the new work July 29 in Nature Physics. “But we’re re-creating some of the fundamental physics that happens near the sun.”

    The sun spews a constant stream of charged particles, called the solar wind, out into space — though scientists aren’t sure exactly how (SN Online: 8/18/17). As the sun rotates, its magnetic field twists the wind into a helical shape called the Parker spiral, named after solar physicist Eugene Parker, who predicted the existence of the solar wind in 1958.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    NASA last year launched its Parker Solar Probe to directly investigate the source of the solar wind (SN: 7/21/18, p. 12). But Peterson and colleagues found a way to mimic the Parker spiral much closer to home.

    The team used a 3-meter-wide aluminum vacuum chamber called the Big Red Ball at the Wisconsin Plasma Physics Laboratory to confine a ball of plasma heated to 100,000° Celsius. A magnet in the center of the ball mimics the sun’s magnetic field, and carefully applied electric currents send the plasma spinning and a wind streaming.

    There are some unavoidable differences between the Big Red Ball and the sun, including size, gravity and temperature. Even so, the wind organized itself into a clear Parker spiral, as expected. The wind also occasionally ejected little blobs of plasma, each about 10 centimeters across. The sun ejects similar blobs, called plasmoids, but no one is sure why. The Big Red Ball could help provide an answer, Peterson says.


    BALLERINA SKIRT The Parker spiral, which has also been described as a “ballerina skirt,” is the shape that the solar wind takes on as the sun rotates, twisting the wind into a helix as seen in a NASA simulation. Scientists mimicked this spiral in plasma in the lab. This video shows a smaller Parker spiral appearing in a ball of hot, spinning plasma inside a vacuum chamber. The bright spiraling structures follow the plasma’s magnetic field.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
  • richardmitnick 9:59 am on July 28, 2019 Permalink | Reply
    Tags: , Among the leading candidates are weakly interacting massive particles- WIMPs, Among the leading candidates are weakly interacting massive particles- WIMPs but scientists have hunted for them for decades with no success., , Dark Matter Macros, EVERY AXION HAS ITS DAY Physicist Gray Rybka of the University of Washington in Seattle and colleagues have created a detector sensitive enough to potentially find hypothetical dark matter particles c, , Physicists think the invisible dark matter must exist because they can see its gravitational effects on visible matter throughout the cosmos. But no one knows what it’s actually made of., Science News, So physicists are turning to other theoretical candidates.   

    From Science News: “Dark matter particles won’t kill you. If they could, they would have already” 

    From Science News

    July 25, 2019
    Lisa Grossman

    A lack of mysterious deaths from hypothetical ‘macros’ suggests dark matter is small and light.

    1
    STRIKETHROUGH Hypothetical dark matter particles called “macros” could stream through space and constantly bombard Earth. Some could seriously injure any unlucky humans they pass through, but a lack of mysterious deaths suggests the biggest potential macros don’t exist. NASA JPL-Caltech

    The fact that no one seems to have been killed by speeding blobs of dark matter puts limits on how large and deadly these particles can be, a study posted July 18 at arXiv.org suggests.

    “In the last 30 years, if someone had died of this, we would have heard of it,” says physicist Glenn Starkman of Case Western Reserve University in Cleveland.

    Physicists think the invisible dark matter must exist because they can see its gravitational effects on visible matter throughout the cosmos. But no one knows what it’s actually made of. Among the leading candidates are weakly interacting massive particles, or WIMPs, but scientists have hunted for them for decades with no success (SN: 6/23/18, p. 13).

    2
    WIMPING OUT The XENON1T experiment (contained inside the large tank above, at left) reports no hint of any interactions from particles of dark matter within, despite a yearlong search.

    So physicists are turning to other theoretical candidates (SN Online: 4/9/18).

    4
    EVERY AXION HAS ITS DAY Physicist Gray Rybka of the University of Washington in Seattle and colleagues have created a detector sensitive enough to potentially find hypothetical dark matter particles called axions.

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

    Starkman and colleagues focused on macroscopic dark matter, or macros, first proposed by physicist Edward Witten in the 1980s (SN Online: 10/7/13). If they exist, macros would be made up of subatomic particles called quarks, just like ordinary matter, but combined in a way never before observed.

    Theoretically, macros could have almost any size and mass. And because dark matter doesn’t interact with regular matter, there would be nothing to stop these particles from zipping around unimpeded. So Starkman — along with Case Western physicist Jagjit Singh Sidhu and physicist Robert Scherrer of Vanderbilt University in Nashville — decided to do a gut check using human flesh as a dark matter detector.

    If a macro as small as a square micrometer zipped through your body at hypersonic speed, it would deposit about as much energy in your body as a typical metal bullet, the team calculated. But the damage it caused would be different from that of a bullet: A macro would heat the cylinder of tissue in its wake to about 10,000,000° Celsius — vaporizing the tissue and leaving a path of plasma.

    “It’s like if you were in Star Wars, and a Jedi hit you with their lightsaber, or someone shot you with their phaser [gun],” Starkman says.

    There would be nothing you could do to shield yourself from such a macro strike. Still, there’s no reason to worry, Starkman says. Considering there have been no reports of anyone suddenly suffering a mysterious lightsaber wound, the researchers concluded that if macros exist, they have to be smaller than a micrometer and heavier than about 50 kilograms.

    “The odds of dying from this are less than 1 in 100 million,” Starkman says.

    As wacky as this might sound, physicist Katherine Freese thought these calculations were worth doing. “This study is fun,” says Freese of the University of Michigan in Ann Arbor. “Looking for macros in already existing detectors, such as the human body, is a good idea.” Though she wasn’t involved in the macro research, she and colleagues did a similar thought experiment with WIMPs in 2012 [Physics Letters B]. “But weak interactions are so weak as to be harmless” to human bodies.

    Next, Starkman and Sidhu plan to look for macro tracks in slabs of granite, which would appear as cylinders of black obsidian running straight through the rock. They’re starting with a cemetery near the Case Western campus.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
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