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  • richardmitnick 10:10 am on April 28, 2019 Permalink | Reply
    Tags: , , , , , , , Jupiter's Europa moon, , Nautilus, OPAG-Outer Planet Assessment Group   

    From Nautilus: “Why Europa Is the Place to Go for Alien Life” 

    Nautilus

    From Nautilus

    April 18, 2019
    Corey S. Powell

    1
    This image shows a view of the trailing hemisphere of Jupiter’s ice-covered satellite, Europa, in approximate natural color. Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long. The bright feature containing a central dark spot in the lower third of the image is a young impact crater some 50 kilometers (31 miles) in diameter. This crater has been provisionally named “Pwyll” for the Celtic god of the underworld. Europa is about 3,160 kilometers (1,950 miles) in diameter, or about the size of Earth’s moon. This image was taken on September 7, 1996, at a range of 677,000 kilometers (417,900 miles) by the solid state imaging television camera onboard the Galileo spacecraft during its second orbit around Jupiter. The image was processed by Deutsche Forschungsanstalt fuer Luftund Raumfahrt e.V., Berlin, Germany. NASA/JPL/DLR.

    NASA/Galileo 1989-2003

    I have seen the future of space exploration, and it looks like a cue ball covered with brown scribbles. I am talking about Europa, the 1,940-mile-wide, nearly white, and exceedingly smooth satellite of Jupiter. It is an enigmatic world that is, in many ways, almost a perfect inversion of Earth. It is also one of the most plausible places to look for alien life. If it strikes you that those two statements sound rather contradictory—why yes, they do. And therein lies the reason why Europa just might be the most important world in the solar system right now. The Europa Clipper spacecraft is scheduled to launch in 2023 to probe the mysterious moon, according to NASA’s 2020 budget proposal.

    NASA/Europa Clipper annotated

    The unearthly aspects of Europa are literally un-earthly : This is an orb sculpted from water ice, not from rock. It has ice tectonics in place of shifting continents, salty ocean in place of mantle, and vapor plumes in place of volcanoes. The surface scribbles may be dirty ocean material that leaked up through the icy equivalent of an earthquake fault.

    From a terrestrial perspective, Europa is built all wrong, with its solid crust up top and water down below. From the perspective of alien life, though, that might be a perfectly dandy arrangement. Beneath its frozen crust, Europa holds twice as much liquid water as exists in all of our planet’s oceans combined. Astrobiologists typically flag water as life’s number-one requirement; well, Europa is drowning in it. Just below the ice line, conditions might resemble the environment on the underside of Antarctic ice sheets. At the bottom of its buried ocean, Europa may have an active system of hydrothermal vents. Both of these are vibrant habitats on Earth.

    Adding a new twist to the story, Europa’s water may sometimes escape its icy confines. On at least four occasions, the Hubble Space Telescope has detected what appear to be large plumes of water vapor erupting from Europa. That detection has confirmed and expanded on the scientific ideas about what makes Europa such a dynamic world. Europa travels in a slightly oval orbit around Jupiter, causing it to get alternately squeezed and stretched by the giant planet’s gravity. The flexing creates intense friction inside the satellite and generates enough heat to maintain a warm ocean beneath Europa’s frozen outer shell. The presence of a plume suggests that the stretching of Europa also opens and closes a network of fissures that allow buried water to erupt as geysers.

    If the geysers consist of ocean water shooting all the way through the crust, they could carry traces of aquatic life with them. And if the plumes rise high enough, a future spacecraft could fly right through them, sniffing for biochemicals.

    2
    SIGNS FROM BELOW: Salty seawater appears to have breached Europa’s frozen exterior, creating a network of red-brown streaks. Perhaps traces of aquatic life were carried along in the process? This scene is 100 miles wide. NASA/JPL-Caltech/SETI Institute

    You can see why people were giddy at a 2015 OPAG meeting held at NASA’s Ames Research Center. A regular forum for geeking out about ice worlds, the OPAG gatherings—short for Outer Planet Assessment Group—feel halfway between the corporate swarm of a MacWorld expo and a vinyl record fair. They are where true believers mingle with the newbies, showing off the latest science, kicking around speculative ideas, and developing strategies for exploration. With each new bit of data, they have grown increasingly convinced that Europa, not Mars, is the place to go to search for alien life. Finding the plume on Europa was another shot of adrenaline. The room went fervently silent as Lorenz Roth of Sweden’s Royal Institute of Technology, calling in via a fuzzy phone line, reported on the latest search for a recurrence of such water eruptions (no luck yet, alas).

    Another significant piece of news was hanging over the OPAG meeting: The discovery that Europa has plate tectonics, like Earth and unlike any other world we know of. Tectonics describes a process in which the crust moves about and cycles back and forth into the interior. Louise Prockter of Johns Hopkins University’s Applied Physics Laboratory co-discovered this style of activity on Europa by painstakingly reconstructing old images from the Galileo spacecraft, which circled Jupiter from 1995 to 2003. (Analysis of other Galileo data suggests the probe flew right past a Europan water plume in 1997, but scientists didn’t realize it at the time.)

    As Prockter explained to me at the meeting, a mobile crust potentially does two important things. It cycles surface ice, along with all the compounds it develops during exposure to the sun, down into the dark ocean; that chemical flow could be crucial for supplying the ocean with nutrients. The motion of the crust also brings ocean material up to the surface, where prying human eyes can seek clues about the Europan ocean without actually drilling down into it.

    Bolstered by these discoveries, the cult of Europa has now escaped the confines of the OPAG meetings. A successful mission to Europa would bring into focus the incredible ice-and-ocean environment of Europa. It would also help scientists understand ice worlds in general. Icy moons, dwarf planets, and giant asteroids are the norm in the vast outer zone of the solar system, and if they repeat the pattern of Europa they may contain much of the solar system’s habitable real estate. There is good reason to think that ice worlds are similarly abundant around other stars as well. Putting all of these new ideas together suggests that the Milky Way may collectively contain tens of billions of life-friendly iceboxes.

    But if these stunning extrapolations seem to suggest that scientists are starting to get a handle on how Europa works, allow me to suggest otherwise. Europa is still largely a big, icy ball of confusion.

    3
    Under the Ice: An artist’s conception of Europa (foreground), Jupiter (right) and Jupiter’s innermost large moon, Io (middle), shows salts bubbling up from Europa’s liquid ocean to reach its frozen surface. NASA/JPL-Caltech.

    Almost everything we know about the surface of Europa comes from NASA’s Galileo mission, which reached Jupiter in 1995. During its eight-year mission, Galileo mapped most of Europa, but at a crude resolution of about one mile per pixel. For comparison, today’s best Mars images show features as small as three feet. Elizabeth “Zibi” Turtle of the Hopkins Applied Physics Lab promises that the camera on NASA’s upcoming Europa probe will achieve a similar level of clarity. Until then, imagine trying to navigate using a map that doesn’t show anything smaller than one mile and you will get a sense of how far the Europa scientists have to go.

    What’s more, at a very basic level, planetary scientists still do not have a good handle on how geology (or maybe we should say “glaciology?”) works in frozen settings. Ice, you see, is not just ice. Robert Pappalardo of NASA’s Jet Propulsion Laboratory, the ponytail-wielding mission scientist for the agency’s upcoming Europa probe, spelled out some of the complexities to me. On Europa, surface temperatures on a warm day at the equator might rise up to -210 degrees Fahrenheit; at the poles, the lows plunge to -370 degrees Fahrenheit. Under those conditions, water is properly thought of as a mineral, and ice has approximately the consistency of concrete. In many ways it is remarkably similar to rock in how it fractures, faults, and shatters. But even in such a deep freeze, surface ice can sublimate—evaporate directly from solid to gas—in a way that rock does not. Icy material tends to boil off from darker, warmer regions and collect on lighter, cooler ones, producing an exotic kind of weathering that rearranges the landscape without any wind or rain.

    All sorts of other things are happening on the surface of Europa. Jupiter has a huge, potent magnetic field that bombards its satellite with radiation: about 500 rem per day on average, which you can more easily judge as a dose strong enough to make you sick in one hour and to kill you in 24. That radiation quickly breaks down any organic compounds, greatly complicating the search for life, but produces all kinds of other complex chemistry. A lab experiment at the Jet Propulsion Laboratory suggests that the colors of Europa’s streaks are produced by irradiated ocean salts. These and other fragmented molecules, along with a steady rain of organic material delivered by comet impacts, could be used as energy sources for life when they circulate back down into the ocean, where any living things would be well protected.

    The movement of Europa’s crust—its icy outer shell—is another broad area of mystery. On ice worlds, Pappalardo notes, water takes on the role of magma and hot rock deep below the surface, but once again ice and rock are not quite the same. Warm ice turns soft, almost slushy, under high pressure and slowly flows. There could be complicated circulation patterns contained entirely within the crust, which is perhaps 10 to 15 miles thick (or maybe more or less; that is yet another mystery that the Europa mission will investigate). Pools of liquid water might exist trapped within the shell, cut off from the underlying ocean. Plumes of water at the surface might not originate directly from the ocean; it is possible that they come from these intermediate lakes, analogous to the largely unexplored Lake Vostok in Antarctica.

    At the OPAG meeting, seemingly narrow arguments about the circulation of ice sparked colorful debates about prospects for life on Europa and, by extension, on the myriad other ice worlds out there. Britney Schmidt of Georgia Tech wondered if the active geology (glaciology) on Europa occurs entirely within the crust. If material does not circulate at all between surface and ocean, Europa is sealed tight. Life could not get any fresh chemicals from up above, and if it somehow manages to survive anyway we might never know unless we find a way to dig a hole all the way through. Several researchers at OPAG suggested that meaningful answers will require a surface lander; one energetic audience member repeatedly argued for sending an impactor—a high-speed bowling ball, essentially—to smack the surface and shake loose any possible buried microbes.

    As for the Europan ocean itself, that runs even deeper into what you might call aqua incognita . If the surface truly is streaked with salts, as the recent experiments indicate, that suggests a mineral-rich ocean in which waters interact vigorously with a rocky seafloor at the bottom. A likely source of such interaction is a network of hydrothermal vents powered by Europa’s internal heat; such vents could provide chemical energy to sustain Europan life, as they do on Earth. But how much total hydrothermal activity goes on? Are the acidity and salinity conducive to life? How much organic material is down there? The scientists egged each other on with provocative questions that, as yet, have no answers.

    When (or if) we will find out will depend, in large part, on how much of Europa’s inner nature is evident from the outside. The conversations at OPAG sometimes devolved into something resembling a college existential argument: If an alien swims in Europa’s ocean and nobody is able to see it, is it really alive?

    The Europa faithful have been waiting a long time for a mission that would wipe away those kinds of arguments, or at least ground them in hard data. That wait has been full of whipsaw swings between optimism and disappointment. NASA’s planned Europa Orbiter got a green light in 1999, only to be cancelled in 2002. The agency rebounded with a proposal for an even more ambitious, nuclear-propelled Jupiter Icy Moons Orbiter, which looked incredible until it got delayed and finally cancelled in 2006. A proposed joint venture with the European Space Agency never even got that far, though the Europeans are going ahead with their part of the project, which will send a probe to Ganymede, another one of Jupiter’s icy moons, in 2030.

    The Europa Clipper, outfitted with scientific instruments that include cameras and spectrometers, will swoop repeatedly past the moon and produce images that determine its composition. There is a chance the Europa mission will include a lander. Funding does not exist yet, but Adam Steltzner—the hearty engineer who figured out how to land the two-ton Curiosity rover safely on Mars—assures me that from a technical standpoint it would not be difficult to design a small probe equipped with rockets to allow a soft touchdown on Europa. There it could drill into the surface and search for possible organic material that has not been degraded by the radiation blasts from Jupiter.

    What you won’t see, the OPAG boffins all sadly agreed, is one of those cool Europa submarines that show up on the speculative “future mission concept” NASA web pages. Getting a probe into Lake Vostok right here on Earth has proven a daunting challenge. Drilling through 10 miles or more of Europan ice and exploring an alien ocean by remote control is something we still don’t know how to do, and certainly not with any plausible future NASA budget.

    No matter. Even the no-frills version of NASA’s current Europa plan will unleash a flood of information about how ice worlds work, and about how likely they are to support life. If the answers are as exciting as many scientists hope—and as I strongly expect—it will bolster the case for future missions to Titan, Enceladus, and some of Europa’s other beckoning cousins. It will reshape the search for habitable worlds around other stars as well. Right now astronomers are mostly focused on finding other Earthlike planets, but maybe that is not where most of the action is. Perhaps most of the life in the universe is locked away, safe but almost undetectable, beneath shells of ice.

    Whether or not Europa is home to alien organisms, it will tell us about the range of what life can be, and where it can be. That one icy moon will help cure science of its rocky-planet chauvinism. Hey, who you calling cue ball?

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 12:32 pm on April 18, 2019 Permalink | Reply
    Tags: "When Beauty Gets in the Way of Science", , , , , Nautilus, , , , , ,   

    From Nautilus: “When Beauty Gets in the Way of Science” 

    Nautilus

    From Nautilus

    April 18, 2019
    Sabine Hossenfelder

    Insisting that new ideas must be beautiful blocks progress in particle physics.

    When Beauty Gets in the Way of Science. Nautilus

    The biggest news in particle physics is no news. In March, one of the most important conferences in the field, Rencontres de Moriond, took place. It is an annual meeting at which experimental collaborations present preliminary results. But the recent data from the Large Hadron Collider (LHC), currently the world’s largest particle collider, has not revealed anything new.

    LHC

    CERN map


    CERN LHC Tunnel

    CERN LHC particles

    Forty years ago, particle physicists thought themselves close to a final theory for the structure of matter. At that time, they formulated the Standard Model of particle physics to describe the elementary constituents of matter and their interactions.

    Standard Model of Particle Physics (LATHAM BOYLE AND MARDUS OF WIKIMEDIA COMMONS)

    After that, they searched for the predicted, but still missing, particles of the Standard Model. In 2012, they confirmed the last missing particle, the Higgs boson.

    CERN CMS Higgs Event

    CERN ATLAS Higgs Event

    The Higgs boson is necessary to make sense of the rest of the Standard Model. Without it, the other particles would not have masses, and probabilities would not properly add up to one. Now, with the Higgs in the bag, the Standard Model is complete; all Pokémon caught.

    1
    HIGGS HANGOVER: After the Large Hadron Collider (above) confirmed the Higgs boson, which validated the Standard Model, it’s produced nothing newsworthy, and is unlikely to, says physicist Sabine Hossenfelder.Shutterstock

    The Standard Model may be physicists’ best shot at the structure of fundamental matter, but it leaves them wanting. Many particle physicists think it is simply too ugly to be nature’s last word. The 25 particles of the Standard Model can be classified by three types of symmetries that correspond to three fundamental forces: The electromagnetic force, and the strong and weak nuclear forces. Physicists, however, would rather there was only one unified force. They would also like to see an entirely new type of symmetry, the so-called “supersymmetry,” because that would be more appealing.

    2
    Supersymmetry builds on the Standard Model, with many new supersymmetric particles, represented here with a tilde (~) on them. ( From the movie “Particle fever” reproduced by Mark Levinson)

    Oh, and additional dimensions of space would be pretty. And maybe also parallel universes. Their wish list is long.

    It has become common practice among particle physicists to use arguments from beauty to select the theories they deem worthy of further study. These criteria of beauty are subjective and not evidence-based, but they are widely believed to be good guides to theory development. The most often used criteria of beauty in the foundations of physics are presently simplicity and naturalness.

    By “simplicity,” I don’t mean relative simplicity, the idea that the simplest theory is the best (a.k.a. “Occam’s razor”). Relying on relative simplicity is good scientific practice. The desire that a theory be simple in absolute terms, in contrast, is a criterion from beauty: There is no deep reason that the laws of nature should be simple. In the foundations of physics, this desire for absolute simplicity presently shows in physicists’ hope for unification or, if you push it one level further, in the quest for a “Theory of Everything” that would merge the three forces of the Standard Model with gravity.

    The other criterion of beauty, naturalness, requires that pure numbers that appear in a theory (i.e., those without units) should neither be very large nor very small; instead, these numbers should be close to one. Exactly how close these numbers should be to one is debatable, which is already an indicator of the non-scientific nature of this argument. Indeed, the inability of particle physicists to quantify just when a lack of naturalness becomes problematic highlights that the fact that an unnatural theory is utterly unproblematic. It is just not beautiful.

    Anyone who has a look at the literature of the foundations of physics will see that relying on such arguments from beauty has been a major current in the field for decades. It has been propagated by big players in the field, including Steven Weinberg, Frank Wilczek, Edward Witten, Murray Gell-Mann, and Sheldon Glashow. Countless books popularized the idea that the laws of nature should be beautiful, written, among others, by Brian Greene, Dan Hooper, Gordon Kane, and Anthony Zee. Indeed, this talk about beauty has been going on for so long that at this point it seems likely most people presently in the field were attracted by it in the first place. Little surprise, then, they can’t seem to let go of it.

    Trouble is, relying on beauty as a guide to new laws of nature is not working.

    Since the 1980s, dozens of experiments looked for evidence of unified forces and supersymmetric particles, and other particles invented to beautify the Standard Model. Physicists have conjectured hundreds of hypothetical particles, from “gluinos” and “wimps” to “branons” and “cuscutons,” each of which they invented to remedy a perceived lack of beauty in the existing theories. These particles are supposed to aid beauty, for example, by increasing the amount of symmetries, by unifying forces, or by explaining why certain numbers are small. Unfortunately, not a single one of those particles has ever been seen. Measurements have merely confirmed the Standard Model over and over again. And a theory of everything, if it exists, is as elusive today as it was in the 1970s. The Large Hadron Collider is only the most recent in a long series of searches that failed to confirm those beauty-based predictions.

    These decades of failure show that postulating new laws of nature just because they are beautiful according to human standards is not a good way to put forward scientific hypotheses. It’s not the first time this has happened. Historical precedents are not difficult to find. Relying on beauty did not work for Kepler’s Platonic solids, it did not work for Einstein’s idea of an eternally unchanging universe, and it did not work for the oh-so-pretty idea, popular at the end of the 19th century, that atoms are knots in an invisible ether. All of these theories were once considered beautiful, but are today known to be wrong. Physicists have repeatedly told me about beautiful ideas that didn’t turn out to be beautiful at all. Such hindsight is not evidence that arguments from beauty work, but rather that our perception of beauty changes over time.

    That beauty is subjective is hardly a breakthrough insight, but physicists are slow to learn the lesson—and that has consequences. Experiments that test ill-motivated hypotheses are at high risk to only find null results; i.e., to confirm the existing theories and not see evidence of new effects. This is what has happened in the foundations of physics for 40 years now. And with the new LHC results, it happened once again.

    The data analyzed so far shows no evidence for supersymmetric particles, extra dimensions, or any other physics that would not be compatible with the Standard Model. In the past two years, particle physicists were excited about an anomaly in the interaction rates of different leptons. The Standard Model predicts these rates should be identical, but the data demonstrates a slight difference. This “lepton anomaly” has persisted in the new data, but—against particle physicists’ hopes—it did not increase in significance, is hence not a sign for new particles. The LHC collaborations succeeded in measuring the violation of symmetry in the decay of composite particles called “D-mesons,” but the measured effect is, once again, consistent with the Standard Model. The data stubbornly repeat: Nothing new to see here.

    Of course it’s possible there is something to find in the data yet to be analyzed. But at this point we already know that all previously made predictions for new physics were wrong, meaning that there is now no reason to expect anything new to appear.

    Yes, null results—like the recent LHC measurements—are also results. They rule out some hypotheses. But null results are not very useful results if you want to develop a new theory. A null-result says: “Let’s not go this way.” A result says: “Let’s go that way.” If there are many ways to go, discarding some of them does not help much.

    To find the way forward in the foundations of physics, we need results, not null-results. When testing new hypotheses takes decades of construction time and billions of dollars, we have to be careful what to invest in. Experiments have become too costly to rely on serendipitous discoveries. Beauty-based methods have historically not worked. They still don’t work. It’s time that physicists take note.

    And it’s not like the lack of beauty is the only problem with the current theories in the foundations of physics. There are good reasons to think physics is not done. The Standard Model cannot be the last word, notably because it does not contain gravity and fails to account for the masses of neutrinos. It also describes neither dark matter nor dark energy, which are necessary to explain galactic structures.

    So, clearly, the foundations of physics have problems that require answers. Physicists should focus on those. And we currently have no reason to think that colliding particles at the next higher energies will help solve any of the existing problems. New effects may not appear until energies are a billion times higher than what even the next larger collider could probe. To make progress, then, physicists must, first and foremost, learn from their failed predictions.

    So far, they have not. In 2016, the particle physicists Howard Baer, Vernon Barger, and Jenny List wrote an essay for Scientific American arguing that we need a larger particle collider to “save physics.” The reason? A theory the authors had proposed themselves, that is natural (beautiful!) in a specific way, predicts such a larger collider should see new particles. This March, Kane, a particle physicist, used similar beauty-based arguments in an essay for Physics Today. And a recent comment in Nature Reviews Physics about a big, new particle collider planned in Japan once again drew on the same motivations from naturalness that have already not worked for the LHC. Even the particle physicists who have admitted their predictions failed do not want to give up beauty-based hypotheses. Instead, they have argued we need more experiments to test just how wrong they are.

    Will this latest round of null-results finally convince particle physicists that they need new methods of theory-development? I certainly hope so.

    As an ex-particle physicist myself, I understand very well the desire to have an all-encompassing theory for the structure of matter. I can also relate to the appeal of theories such a supersymmetry or string theory. And, yes, I quite like the idea that we live in one of infinitely many universes that together make up the “multiverse.” But, as the latest LHC results drive home once again, the laws of nature care heartily little about what humans find beautiful.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 9:45 am on April 14, 2019 Permalink | Reply
    Tags: "The Day Feynman Worked Out Black-Hole Radiation on My Blackboard", , , , , , Nautilus,   

    From Nautilus: “The Day Feynman Worked Out Black-Hole Radiation on My Blackboard” 

    Nautilus

    From Nautilus

    Apr 11, 2019

    The amazing image of a black hole unveiled Wednesday, along with data from the Event Horizon Telescope, may not substantiate Stephen Hawking’s famous theory that radiation, an example of spontaneous emission at the quantum level, is emitted by a black hole.

    The first image of a black hole, Messier 87 Credit Event Horizon Telescope Collaboration, via NSF 4.10.19

    But the news did remind us of a story that physicist and writer Alan Lightman told Nautilus: Richard Feynman came up with the idea for spontaneous emission before Hawking. Here is Lightman in his own words:

    1
    After a few minutes, Richard Feynman had worked out the process of spontaneous emission, which is what Stephen Hawking became famous for a year later.Wikicommons

    “One day at lunch in the Caltech cafeteria, I was with two graduate students, Bill Press and Saul Teukolsky, and Feynman. Bill and Saul were talking about a calculation they had just done. It was a theoretical calculation, purely mathematical, where they looked at what happens if you shine light on a rotating black hole. If you shine it at the right angle, the light will bounce off the black hole with more energy than it came in with. The classical analogue is a spinning top. If you throw a marble at the top at the right angle, the marble will bounce off the top with more velocity than it came in with. The top slows down and the energy, the increased energy of the marble, comes from the spin of the top. As Bill and Saul were talking, Feynman was listening.

    We got up from the table and began walking back through the campus. Feynman said, ‘You know that process you’ve described? It sounds very much like stimulated emission.’ That’s a quantum process in atomic physics where you have an electron orbiting an atom, and a light particle, a photon, comes in. The two particles are emitted and the electron goes to a lower energy state, so the light is amplified by the electron. The electron decreases energy and gives up that extra energy to sending out two photons. Feynman said, ‘What you’ve just described sounds like stimulated emission. According to Einstein, there’s a well-known relationship between stimulated emission and spontaneous emission.’

    Spontaneous emission is when you have an electron orbiting an atom and it just emits a photon all by itself, without any light coming in, and goes to a lower energy state. Einstein had worked out this relationship between stimulated and spontaneous emission. Whenever you have one, you have the other, at the atomic level. That’s well known to graduate students of physics. Feynman said that what Bill and Saul were describing sounded like simulated emission, and so there should be a spontaneous emission process analogous to it.

    We’d been wandering through the campus. We ended up in my office, a tiny little room, Bill, Saul, me, and Feynman. Feynman went to the blackboard and began working out the equations for spontaneous emission from black holes. Up to this point in history, it had been thought that all black holes were completely black, that a black hole could never emit on its own any kind of energy. But Feynman had postulated, after listening to Bill and Saul talk at lunch, that if a spinning black hole can emit with light coming in, it can also emit energy with nothing coming in, if you take into account quantum mechanics.

    After a few minutes, Feynman had worked out the process of spontaneous emission, which is what Stephen Hawking became famous for a year later. Feynman had it all on my blackboard. He wasn’t interested in copying down what he’d written. He just wanted to know how nature worked, and he had just learned that isolated black holes are capable of emitting energy when you take into account quantum effects. After he finished working it out, he brushed his hands together to get the chalk dust off them, and walked out of the office.

    After Feynman left, Bill and Saul and I were looking at the blackboard. We were thinking it was probably important, not knowing how important. Bill and Saul had to go off to some appointment, and so they left the office. A little bit later, I left. But that night I realized this was a major thing that Feynman had done and I needed to hurry back to my office and copy down the equations. But when I got back to my office in the morning, the cleaning lady had wiped the blackboard clean.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 6:10 pm on April 11, 2019 Permalink | Reply
    Tags: , , , , , , Nautilus, , , ,   

    From Nautilus: “First Black-Hole Image: It’s Not Looks That Count” 

    Nautilus

    From Nautilus

    Apr 11, 2019
    Sabine Hossenfelder

    1
    FIRST LOOK: The Event Horizon Telescope measures wavelength in the millimeter regime, too long to be seen by eye, but ideally suited to the task of imaging a black hole: The gas surrounding the black hole is almost transparent at this wavelength and the light travels to Earth almost undisturbed. Since we cannot see light of such wavelength by eye, the released telescope image shows the observed signal shifted into the visible range.Event Horizon Telescope Collaboration.

    “The Day Feynman Worked Out Black-Hole Radiation on My Blackboard”
    2
    After a few minutes, Richard Feynman had worked out the process of spontaneous emission, which is what Stephen Hawking became famous for a year later.Wikicommons.

    The Italian 14th-century painter, Giotto di Bondone, when asked by the Pope to prove his talent, is said to have swung his arm and drawn a perfect circle. But geometric perfection is limited by the medium. Inspect a canvas closely enough, and every circle will eventually appear grainy. If perfection is what you seek, don’t look at man-made art, look at the sky. More precisely, look at a black hole.

    Looking at a black hole is what the Event Horizon Telescope has done for the past 12 years. Yesterday, the collaboration released the long-awaited results from its first full run in April 2017. Contrary to expectation, their inaugural image is not, as many expected, Sagittarius A*, the black hole at the center of the Milky Way. Instead, it is the supermassive black hole in the elliptic galaxy Messier 87, about 55 million light-years from here. This black hole weighs in at 6.5 billion times the mass of our sun, and is considerably larger than the black hole in our own galaxy [1,000 times the size of SGR A*]. So, even though the Messier 87 black hole is a thousand times farther away than Sagittarius A*, it still appears half the size in the sky.

    The Event Horizon Telescope (EHT) is not less remarkable than the objects it observes. With a collaboration of 200 people, the EHT uses not a single telescope, but a global network of nine telescopes. Its sites, from Greenland to the South Pole and from Hawaii to the French Alps, act in concert as one. Together, the collaboration commands a telescope the size of planet Earth, staring at a tiny patch in the northern sky that contains the Messier-87 black hole.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)


    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile [recently added]

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL [recently added]

    Future Array/Telescopes

    NOEMA (NOrthern Extended Millimeter Array) will double the number of its 15 meter antennas of its predecessor from six to twelve, located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)


    ARO 12m Radio Telescope

    In theory, black holes are regions of space where the gravitational pull is so large that everything, including light, becomes trapped for eternity. The surface of the trapping region is called the “event horizon.” It has no substance; it is a property of space itself. In the simplest case, the event horizon is a sphere—a perfect sphere, made of nothing.

    In reality, it’s complicated. Astrophysicists have had evidence for the existence of black holes since the 1990s, but so far all observations have been indirect—inferred from the motion of visible stars and gas, leaving doubt as to whether the dark object really possesses the defining event horizon. It turned out difficult to actually see a black hole. Trouble is, they’re black. They trap light. And while Stephen Hawking proved that black holes must emit radiation due to quantum effects, this quantum glow is far too feeble to observe.

    But much like the prisoners in Plato’s cave, we can see black holes by observing the shadows they cast. Black holes attract gas from their environment. This gas collects in a spinning disk, and heats up as it spirals into the event horizon, pushing around electric charges. This gives rise to strong magnetic fields that can create a “jet,” a narrow, directed stream of particles leaving the black hole at almost the speed of light. But whatever strays too close to the event horizon falls in and vanishes without a trace.

    At the same time black holes bend rays of light, bend them so strongly, indeed, that looking at the front of a black hole, we can see part of the disk behind it. The light that just about manages to escape reveals what happens nearby the horizon. It is an asymmetric image that the astrophysicists expect, brighter on the side of the black hole where the material surrounding it moves toward us, and darker where it moves away from us. The hot gas combined with the gravitational lensing creates the unique observable signature that the EHT looks out for.

    The experimental challenge is formidable. The network’s telescopes must synchronize their data-taking using atomic clocks. Weather conditions must be favorable at all locations simultaneously. Once recorded, the amount of data is so staggeringly large, it must be shipped on hard disks to central locations for processing.

    The theoretical challenges are not any lesser. Black holes bend light so much that it can wrap around the horizon multiple times. The resulting image is too complicated to capture in simple equations. Though the math had been known since the 1920s, it wasn’t until 1978 that physicists got a first glimpse of what a black hole would actually look like. In that year, the French astrophysicist Jean-Pierre Luminet programmed the calculation on an IBM 7040 using punchcards. He drew the image by hand.

    Today, astrophysicists use computers many times more powerful to predict the accretion of gas onto the black hole and how the light bends before reaching us. Still, the partly turbulent motion of the gas, the electric and magnetic fields created by it, and the intricacies of the particle’s interactions are not fully understood.

    The EHT’s observations agree with expectation. But this result is more than just another triumph of Einstein’s theory of general relativity. It is also a triumph of the astronomers’ resourcefulness. They joined hands and brains to achieve what they could not have done separately. And while their measurement settles a long-standing question—yes, black holes really do have event horizons!—it is also the start of further exploration. Physicists hope that the observations will help them understand better the extreme conditions in the accretion disk, the role of magnetic fields in jet formation, and the way supermassive black holes affect galaxy formation.

    When the Pope received Giotto’s circle, it was not the image itself that impressed him. It was the courtier’s report that the artist produced it without the aid of a compass. This first image of a black hole, too, is remarkable not so much for its appearance, but for its origin. A black sphere, spanning 40 billion kilometers, drawn on a background of hot gas by the greatest artist of all: Nature herself.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 9:38 am on March 27, 2019 Permalink | Reply
    Tags: , , , , Nautilus, , Snowball Earth   

    From Nautilus: “Glaciers May Have Covered the Entire Planet—Twice” 

    Nautilus

    From Nautilus

    Mar 26, 2019
    Laura Poppick

    1
    Ancient rocks suggest that ice entirely covered our planet on at least two occasions. Those events may help explain the rise of complex life that followed. Photo Illustration by pryzmat / Shutterstock.

    The Earth has endured many changes in its 4.5-billion-year history, with some tumultuous twists and turns along the way. One especially dramatic episode appears to have come between 700 million and 600 million years ago, when scientists think ice smothered the entire planet, from the poles to the equator—twice in quick succession.

    Drawing on evidence across multiple continents, scientists say these Snowball Earth events may have paved the way for the Cambrian explosion of life that followed—the period when complex, multicellular organisms began to diversify and spread across the planet.

    When Caltech geologist Joe Kirschvink coined the term Snowball Earth in 1989—merging ideas that some geologists, climate physicists and planetary chemists had been thinking about for decades—many earth scientists were skeptical that these cataclysmic events could really have occurred. But with mounting evidence in support of the theory and new data that help pin down the timing of events, more scientists have warmed up to the idea.

    Paul Hoffman, a geologist at the University of Victoria in British Columbia, has helped pioneer Snowball Earth research over the past 25 years. Among other things, he amassed 50 months’ worth of fieldwork in Namibia, where he gathered evidence of ancient glacial activity in rocks that are interspersed with limestone. Since limestone tends to form in the warmest parts of the ocean, this sandwich-like pattern supports the idea that glaciers covered all of the Earth, cold as well as warm spots, during Snowball Earth episodes. Knowable spoke with Hoffman, who recounts his life work in the Annual Review of Earth and Planetary Sciences, about the evolution of the Snowball Earth theory and what questions remain. This conversation has been edited for length and clarity.

    3
    Snowologist: Paul Hoffman says he is still doing fieldwork in Namibia, as a 77-year-old. “It’s just a large and fascinating problem,” he said. “It’s hard to pull myself away.”
    Illustration by James Provost / Creative Commons.

    What did the planet look like during Snowball Earth?

    The name describes its appearance from outer space—a glistening white ball. The ice surface is mostly coated with frost and tiny ice crystals that settled out of the cold dry air, which is far below freezing everywhere. Gale-force winds howl in low latitudes. Beneath the floating ice shelf, a dark and briny ocean is continually stirred by tides and turbulent eddies generated by geothermal heat slowly entering from the ocean floor.

    What tipped off geologists to the possibility of a Snowball Earth?

    Geologists were struggling to understand what they saw in the geologic record—that not too long before the first appearance of complex life, there was unmistakable evidence of glaciation even in the warmest areas of the Earth. Geologists had a very difficult time understanding how this was possible.

    The deposits that glaciers leave behind are very distinctive. They look like cement that has been dumped out of a cement truck. These Snowball ice sheets would have flowed from the continents out onto the ocean, so we have a lot of deposits that formed in the marine environment where you get what are known as dropstones: pebbles or boulders that are out of place. Very often, you see structures related to the impact, as if the stone was somehow dropped and then plunked into the underlying sediment. It’s difficult to imagine what, other than floating ice, could have possibly transported this debris; trees, which can carry soil and stones out to sea in their roots, had not yet evolved.

    3
    A Seafloor Embrace: A glacial dropstone from Namibia, in rocks that date to the second Snowball Earth. The stone was likely carried and dropped by a floating ice shelf, and when it plunked into seafloor sediment below, that sediment folded around it. (Penny [upper right] shown for scale.)Courtesy of Paul Hoffman.

    How did you start studying Snowball Earth?

    I had known about the hypothesis since even before I was interested in working on the problem myself. Joe Kirschvink at Caltech told me about it a few months after he had the idea in 1989, but he never did anything more with it at that time. I liked it because I like ideas, but there was a credibility gap, so before our work, the hypothesis was dormant.

    The biggest problem was that because the conditions were so different from any other time in Earth’s history, we didn’t understand the implications of the hypothesis well enough to know whether any given bit of geologic evidence was either for or against it. We had to have climate models to see what actually happens under Snowball conditions, and that modeling, developed later, has been extremely important.

    My main contribution was making the case that it was a credible scientific hypothesis by arguing, from different disciplines within geoscience, that there was a lot of geological evidence consistent with the predictions. As I often like to say, new ideas or hypotheses are like small children: It’s best not to judge them too early because you don’t know what they are going to be like as adults. Very often, the problem with new ideas is not that they are wrong, but that they are incomplete.

    What triggered the runaway growth of ice on Earth?

    That’s the “why” question and that’s maybe the most difficult one. I don’t think there is a consensus on this. There are a number of factors that contributed, and it is useful to look at this in two ways. First of all, what was the general condition that made for a colder climate and therefore made the Earth more susceptible to this runaway ice growth phenomenon? And then what was the immediate trigger that tipped it over the edge?

    4
    Snowball Earth Snooping: On a field expedition with Paul Hoffman in 2002, geoscientists Galen Halverson (now at McGill University) and Matthew Hurtgen (now at Northwestern University) collect carbonate rocks from a mountainside in northeastern Svalbard, Norway. The carbonate rocks rest directly above glacial deposits from the second Snowball Earth event. This juxtaposition of carbonates—which form only in warm parts of the ocean—and glacial rocks supports the theory that ice covered the entire planet during the Snowball Earth episodes. Courtesy of Paul Hoffman.

    When the Snowball events occurred, the supercontinent Rodinia was in the process of breaking up. A supercontinent is a state in which all of the continents are clustered together in one group. The reason why people think there is a connection there is that the breakup of a supercontinent would increase rainfall in the continental areas, and that would increase the weathering of crustal rocks. The weathering of rocks actually consumes carbon dioxide, so that would lead to less carbon dioxide in the atmosphere and therefore a colder climate.

    As for what actually caused the immediate trigger, attention has focused in recent years on a sequence of very large volcanic eruptions that occurred in what is now the high arctic of Canada. These eruptions occurred around 717 million and 719 million years ago. When you get fire fountains—lava that comes out of one place over a period of weeks or months—you get a strong thermal upwelling in the atmosphere from the heating effect of that lava. These upwellings can loft sulfur aerosols into the stratosphere where they hang around for a significant amount of time. These sulfur gas particles reflect incoming solar radiation and have a strong cooling effect. Because of the coincidence in timing between these eruptions and the onset of the first and longer of the two Snowball Earths, it’s been postulated that that may have been the immediate trigger.

    What did life on Snowball Earth look like, and how did it change as a consequence of runaway ice growth?

    There were certainly bacteria and there were also algae and unicellular primitive animals, or protists.

    There is also evidence that the first multicellular animals originated at this time, probably something like sponges. Why is a matter of speculation: There are a number of ideas on this, but they are difficult to test. One idea is that on Snowball Earth, ecosystems may have been more isolated from one another and this might be a situation that would be helpful for evolving new forms of life, and particularly forms of life that are altruistic—ones with cells that find that there is an advantage in working together rather than working individually. So more isolation of different ecosystems might have allowed certain ecosystems that had a higher proportion of these multicellular altruists to establish a foothold.

    How was the Snowball theory received by other geologists?

    I underestimated how emotional people would get about it and how wedded people were to the idea that the Earth has never really been greatly different than it is today. In the 19th century, people had a difficult time believing that most of northern Europe and North America were covered by an ice sheet only 20,000 years ago. That was as hard for a 19th-century geologist to accept as Snowball Earth has been for 20th-century geologists.

    For a long time we had a lot of evidence for glaciation at low latitude and in the warmest parts of the Earth, but we didn’t really have a good idea of the dates of these events. It was sort of embarrassing. But between 2010 and 2014 that situation dramatically changed. We now have pretty precise estimates from two very different dating techniques, and it’s impressive that they are giving highly consistent results. Working out the timescale [GeoScienceWorld] has caused a majority of geologists working on the problem to now accept the Snowball hypothesis.

    Alternative theories have arisen over the years, including what is called the Slushball theory—a less extreme version of Snowball Earth. How does pinning down the dates help sort out these alternative theories?

    In the Slushball scenario, carbon dioxide would start building up very quickly, so the glaciation would be short-lived and the ice would retreat gradually. This is not what we see in the geologic record. We now know that the first Snowball lasted for 58 million years and that is completely inconsistent with the Slushball idea. Also, we see the Snowball glaciations terminate extremely abruptly and they are followed by clear evidence of a complete and abrupt climate reversal, a very hot period. That is not explained by the Slushball model.

    I don’t think there are any other alternatives that satisfy the evidence.

    4
    It Was a Seafloor in Another Life: Hoffman has spent a cumulative 50 months collecting evidence of Snowball Earth in the desert mountain ranges of Namibia. The landscape shown here is comprised of an ancient seafloor punctuated with dropstones—sporadically placed stones that researchers believe were carried by ice floating out at sea.Courtesy of Paul Hoffman.

    What other questions about Snowball Earth remain?

    The dating has created a new set of problems. One thing the dating revealed was that the two Snowball Earths occurred in rapid succession and were very unequal in duration. The first one lasted 58 million years [PNAS] and the second one only lasted 5 million to 15 million years. So we don’t know why there is this great disparity in how long the glaciations lasted. And why was it that there was just this short interval between the two? There’s only about 10 million years when there was no ice at all and then suddenly the planet went back into Snowball Earth. So why two in rapid succession? And why wasn’t there a third one or a fourth one? These are new questions that have arisen as a result of our understanding of the timing.

    Could Snowball Earth return?

    I don’t think we are in a very good position to say whether or not it’s likely to happen in the future. The future is a long time. We can say it is not going to happen in the next several tens of thousands of years.

    Why study Earth history?

    The history of our planet is one of the greatest stories. Because we live here and we are dependent on this place, it is very important to understand that the Earth has not always been the way it is today. Snowball Earth is an example of the kinds of amazing things that the Earth has been through that we would never have suspected if we didn’t investigate the geologic record.

    Dealing with Snowball Earth has been fantastic—it’s been the most intense learning experience of my life, and I never anticipated that it would be accepted in my lifetime.

    And you’re still at it, after 25 years?

    I’m still doing fieldwork in Namibia, as a 77-year-old. It’s just a large and fascinating problem. It’s hard to pull myself away.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 11:00 am on February 7, 2019 Permalink | Reply
    Tags: Abraham (Avi) Loeb, , , , , Black Hole Initiative, Black Hole Institute, , , Infrared results beautifully complemented by observations at radio wavelengths, , Nautilus, , S-02, , , The development of high-resolution infrared cameras revealed a dense cluster of stars at the center of the Milky Way   

    From Nautilus: “How Supermassive Black Holes Were Discovered” 

    Nautilus

    From Nautilus

    February 7, 2019
    Mark J. Reid, CfA SAO

    Astronomers turned a fantastic concept into reality.

    An Introduction to the Black Hole Institute

    Fittingly, the Black Hole Initiative (BHI) was founded 100 years after Karl Schwarzschild solved Einstein’s equations for general relativity—a solution that described a black hole decades before the first astronomical evidence that they exist. As exotic structures of spacetime, black holes continue to fascinate astronomers, physicists, mathematicians, philosophers, and the general public, following on a century of research into their mysterious nature.

    Pictor A Blast from Black Hole in a Galaxy Far, Far Away

    This computer-simulated image of a supermassive black hole at the core of a galaxy. Credit NASA, ESA, and D. Coe, J. Anderson

    The mission of the BHI is interdisciplinary and, to that end, we sponsor many events that create the environment to support interaction between researchers of different disciplines. Philosophers speak with mathematicians, physicists, and astronomers, theorists speak with observers and a series of scheduled events create the venue for people to regularly come together.

    As an example, for a problem we care about, consider the singularities at the centers of black holes, which mark the breakdown of Einstein’s theory of gravity. What would a singularity look like in the quantum mechanical context? Most likely, it would appear as an extreme concentration of a huge mass (more than a few solar masses for astrophysical black holes) within a tiny volume. The size of the reservoir that drains all matter that fell into an astrophysical black hole is unknown and constitutes one of the unsolved problems on which BHI scholars work.

    We are delighted to present a collection of essays which were carefully selected by our senior faculty out of many applications to the first essay competition of the BHI. The winning essays will be published here on Nautilus over the next five weeks, beginning with the fifth-place finisher and working up to the first-place finisher. We hope that you will enjoy them as much as we did.

    —Abraham (Avi) Loeb
    Frank B. Baird, Jr. Professor of Science, Harvard University
    Chair, Harvard Astronomy Department
    Founding Director, Black Hole Initiative (BHI)

    In the 1700s, John Michell in England and Pierre-Simon Laplace in France independently thought “way out of the box” and imagined what would happen if a huge mass were placed in an incredibly small volume. Pushing this thought experiment to the limit, they conjectured that gravitational forces might not allow anything, even light, to escape. Michell and Laplace were imagining what we now call a black hole.

    Astronomers are now convinced that when massive stars burn through their nuclear fuel, they collapse to near nothingness and form a black hole. While the concept of a star collapsing to a black hole is astounding, the possibility that material from millions and even billions of stars can condense into a single supermassive black hole is even more fantastic.

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Yet astronomers are now confident that supermassive black holes exist and are found in the centers of most of the 100 billion galaxies in the universe.

    How did we come to this astonishing conclusion? The story begins in the mid-1900s when astronomers expanded their horizons beyond the very narrow range of wavelengths to which our eyes are sensitive. Very strong sources of radio waves were discovered and, when accurate positions were determined, many were found to be centered on distant galaxies. Shortly thereafter, radio antennas were linked together to greatly improve angular resolution.

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    CfA Submillimeter Array Mauna Kea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    These new “interferometers” revealed a totally unexpected picture of the radio emission from galaxies—the radio waves did not appear to come from the galaxy itself, but from two huge “lobes” symmetrically placed about the galaxy. Figure One shows an example of such a “radio galaxy,” named Cygnus A. Radio lobes can be among the largest structures in the universe, upward of a hundred times the size of the galaxy itself.

    2
    Figure One: Radio image of the galaxy Cygnus A. Dominating the image are two huge “lobes” of radio emitting plasma. An optical image of the host galaxy would be smaller than the gap between the lobes. The minimum energy needed to power some radio lobes can be equivalent to the total conversion of 10 million stars to energy! Note the thin trails of radio emission that connect the lobes with the bright spot at the center, where all of the energy originates. NRAO/AUI

    How are immense radio lobes energized? Their symmetrical placement about a galaxy clearly suggested a close relationship. In the 1960s, sensitive radio interferometers confirmed the circumstantial case for a relationship by discovering faint trails, or “jets,” tracing radio emission from the lobes back to a very compact source at the precise center of the galaxy. These findings motivated radio astronomers to increase the sizes of their interferometers in order to better resolve these emissions. Ultimately this led to the technique of Very Long Baseline Interferometry (VLBI), in which radio signals from antennas across the Earth are combined to obtain the angular resolution of a telescope the size of our planet!

    GMVA The Global VLBI Array

    Radio images made from VLBI observations soon revealed that the sources at the centers of radio galaxies are “microscopic” by galaxy standards, even smaller than the distance between the sun and our nearest star.

    When astronomers calculated the energy needed to power radio lobes they were astounded. It required 10 million stars to be “vaporized,” totally converting their mass to energy using Einstein’s famous equation E = mc2! Nuclear reactions, which power stars, cannot even convert 1 percent of a star’s mass to energy. So trying to explain the energy in radio lobes with nuclear power would require more than 1 billion stars, and these stars would have to live within the “microscopic” volume indicated by the VLBI observations. Because of these findings, astronomers began considering alternative energy sources: supermassive black holes.

    Given that the centers of galaxies might harbor supermassive black holes, it was natural to check the center of our Milky Way galaxy for such a monster. In 1974, a very compact radio source, smaller than 1 second of arc (1/3600 of a degree) was discovered there. The compact source was named Sagittarius A*, or Sgr A* for short, and is shown at the center of the right panel of Figure 2. Early VLBI observations established that Sgr A* was far more compact than the size of our solar system. However, no obvious optical, infrared, or even X-ray emitting source could be confidently identified with it, and its nature remained mysterious.

    3
    Figure Two: Images of the central region of the Milky Way. The left panel shows an infrared image. The orbital track of star S2 is overlaid, magnified by a factor of 100. The orbit has period of 16 years, requires an unseen mass of 4 million times that of the sun, and the gravitational center is indicated by the arrow. The right panel shows a radio image. The point-like radio source Sgr A* (just below the middle of the image) is precisely at the gravitational center of the orbiting stars. Sgr A* is intrinsically motionless at the galactic center and, therefore, must be extremely massive.Left panel: R. Genzel; Right panel: J.-H. Zhao

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group

    Andrea’s Favorite star SO-2

    Andrea Ghez, astrophysicist and professor at the University of California, Los Angeles, who leads a team of scientists observing S2 for evidence of a supermassive black hole UCLA Galactic Center Group

    SGR A and SGR A* from Penn State and NASA/Chandra

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    Meanwhile, the development of high-resolution infrared cameras revealed a dense cluster of stars at the center of the Milky Way. These stars cannot be seen at optical wavelengths, because visible light is totally absorbed by intervening dust. However, at infrared wavelengths 10 percent of their starlight makes its way to our telescopes, and astronomers have been measuring the positions of these stars for more than two decades. These observations culminated with the important discovery that stars are moving along elliptical paths, which are a unique characteristic of gravitational orbits. One of these stars has now been traced over a complete orbit, as shown in the left panel of Figure Two.

    Many stars have been followed along partial orbits, and all are consistent with orbits about a single object. Two stars have been observed to approach the center to within the size of our solar system, which by galaxy standards is very small. At this point, gravity is so strong that stars are orbiting at nearly 10,000 kilometers per second—fast enough to cross the Earth in one second! These measurements leave no doubt that the stars are responding to an unseen mass of 4 million times that of the sun. Combining this mass with the (astronomically) small volume indicated by the stellar orbits implies an extraordinarily high density. At this density it is hard to imagine how any type of matter would not collapse to form a black hole.

    The infrared results just described are beautifully complemented by observations at radio wavelengths. In order to identify an infrared counterpart for Sgr A*, the position of the radio source needed to be precisely transferred to infrared images. An ingenious method to do this uses sources visible at both radio and infrared wavelengths to tie the reference frames together. Ideal sources are giant red stars, which are bright in the infrared and have strong emission at radio wavelengths from molecules surrounding them. By matching the positions of these stars at the two wavebands, the radio position of Sgr A* can be transferred to infrared images with an accuracy of 0.001 seconds of arc. This technique placed Sgr A* precisely at the position of the gravitational center of the orbiting stars.

    How much of the dark mass within the stellar orbits can be directly associated with the radio source Sgr A*? Were Sgr A* a star, it would be moving at over 10,000 kilometers per second in the strong gravitational field as other stars are observed to do. Only if Sgr A* is extremely massive would it move slowly. The position of Sgr A* has been monitored with VLBI techniques for over two decades, revealing that it is essentially stationary at the dynamical center of the Milky Way. Specifically, the component of Sgr A*’s intrinsic motion perpendicular to the plane of the Milky Way is less than one kilometer per second. By comparison, this is 30 times slower than the Earth orbits the sun. The discovery that Sgr A* is essentially stationary and anchors the galactic center requires that Sgr A* contains over 400,000 times the mass of the sun.

    Recent VLBI observations have shown that the size of the radio emission of Sgr A* is less than that contained within the orbit of Mercury. Combining this volume available to Sgr A* with the lower limit to its mass yields a staggeringly high density. This density is within a factor of less than 10 of the ultimate limit for a black hole. At such an extreme density, the evidence is overwhelming that Sgr A* is a supermassive black hole.

    These discoveries are elegant for their directness and simplicity. Orbits of stars provide an absolutely clear and unequivocal proof of a great unseen mass concentration. Finding that the compact radio source Sgr A* is at the precise location of the unseen mass and is motionless provides even more compelling evidence for a supermassive black hole. Together they form a simple, unique demonstration that the fantastic concept of a supermassive black hole is indeed a reality. John Michell and Pierre-Simon Laplace would be astounded to learn that their conjectures about black holes not only turned out to be correct, but were far grander than they ever could have imagined.

    Mark J. Reid is a senior astronomer at the Center for Astrophysics, Harvard & Smithsonian. He uses radio telescopes across the globe simultaneously to obtain the highest resolution images of newborn and dying stars, as well as black holes.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 10:01 am on November 8, 2018 Permalink | Reply
    Tags: , , , , Nautilus, Sarah Stewart, Synestia, The Woman Who Reinvented the Moon,   

    From Nautilus: Women in STEM- “The Woman Who Reinvented the Moon” Sarah Stewart 

    Nautilus

    From Nautilus

    November 8, 2018
    Brian Gallagher

    Sarah Stewart is living her ideal life—and it just got sweeter. The University of California, Davis planetary physicist recently won a MacArthur Foundation Fellowship, famously and unofficially known as the “genius grant,” for her work on the origin of Earth’s moon, upending a decades-old theory. She’s been awarded $625,000.

    “It’s an amazing concept to just say, ‘We’re going to give you the opportunity to do something, and we’re not going to tell you anything about what to do.’ That’s very unusual and freeing,” she told Nautilus, referring to the grant program. She was particularly thrilled by the recognition the award represents. The foundation speaks to several dozen of a candidate’s peers as a part of its vetting process. “What I really feel is appreciation for my colleagues,” she said. “That really touches me.”

    Nautilus spoke to Stewart during World Space Week, the theme of which, this year, is “Space Unites the World.” It compelled her to pen a poem, using the theme as a title. Nautilus asked Stewart about that, as well as how her laboratory experiments, which replicate the pressures and temperatures of planetary collisions, informed her model of the moon’s birth.

    1
    Sarah Stewart. John D. & Catherine T. MacArthur Foundation

    How can space bring us together?

    This World Space Week is happening at a time where the world seems to be highlighting divisions. And so I wrote what I wrote as a response to that. Space exploration and discovery of things that are surprising and new is a way to bring everyone together, and enjoy the profound beauty of nature. And I would like us to spend more time talking about the things that bring us together.

    Like the moon. Give us a brief history of its origin theories.

    Next year, 2019, is the 50th anniversary of the Apollo moon landing. The rock samples that the Apollo missions brought back basically threw out every previous idea for the origin of the moon. Before the Apollo results were in, a Russian astronomer named Viktor Safronov had been developing models of how planets grow. He found that they grow into these sub- or proto-planet-size bodies that would then collide. A couple of different groups then independently proposed that a giant impact made a disc around the Earth that the moon accreted from. Over the past 50 years, that model became quantitative, predictive. Simulations showed that the moon should be made primarily out of the object that struck the proto-Earth. But the Apollo mission found that the moon is practically a twin of the Earth, particularly its mantle, in major elements and in isotopic ratios: The different weight elements are like fingerprints, present in the same abundances. Every single small asteroid and planet in the solar system has a different fingerprint, except the Earth and the moon. So the giant impact hypothesis was wrong. It’s a lesson in how science works—the giant impact hypothesis hung on for so long because there was no alternative model that hadn’t already been disproven.

    How is your proposal for the moon’s birth different?

    We changed the giant impact. And by changing it we specifically removed one of the original constraints. The original giant impact was proposed to set the length of day of the Earth, because angular momentum—the rotational equivalent of linear momentum—is a physical quantity that is conserved: If we go backward in time, the moon comes closer to the Earth. At the time the moon grew, the Earth would have been spinning with a five-hour day. So all of the giant impact models were tuned to give us a five-hour day for the Earth right after the giant impact. What we did was say, “Well, what if there were a way to change the angular momentum after the moon formed?” That would have to be through a dynamical interaction with the sun. What that means is that we could start the Earth spinning much faster—we were exploring models where the Earth had a two- to three-hour day after the giant impact.

    What did a faster-spinning Earth do to your models?

    The surprising new thing is that when the Earth is hot, vaporized, and spinning quickly, it isn’t a planet anymore. There’s a boundary beyond which all of the Earth material cannot physically stay in an object that rotates altogether—we call that the co-rotation limit. A body that exceeds the co-rotation limit forms a new object that we named a synestia, a Greek-derived word that is meant to represent a connected structure. A synestia is a different object than a planet plus a disc. It has different internal dynamics. In this hot vaporized state, the hot gas in the disc can’t fall onto the planet, because the planet has an atmosphere that’s pushing that gas out. What ends up happening is that the rock vapor that forms a synestia cools by radiating to space, forms magma rain in the outer parts of the synestia, and that magma rain accretes to form the moon within the rock vapor that later cools to become the Earth.

    How did the idea of a synestia come about?

    In 2012, Matija Ćuk and I published a paper that was a high-spin model for the origin of the moon. We changed the impact event, but we didn’t realize that after the impact, things were completely different. It just wasn’t anything we ever extracted from the simulations. It wasn’t until two years later when my student Simon Lock and I were looking at different plots, plots we had never made before out of the same simulations, that we realized that we had been interpreting what happened next incorrectly. There was a bonafide eureka moment where we’re sitting together talking about how the disc would evolve around the Earth after the impact, and realizing that it wasn’t a standard disc. These synestias have probably been sitting in people’s computer systems for quite some time without anyone ever actually identifying them as something different.

    Was the size of the synestia beyond the moon’s current orbit?

    It could have been bigger. Exactly how big it was depends on the energy of the event and how fast it was spinning. We don’t have precise constraints on that to make the moon because a range of synestias could make the moon.

    How long was the Earth in a synestia state?

    The synestia was very large, but it didn’t last very long. Because rock vapor is very hot, and where we are in the solar system is far enough away from the sun that our mean temperature is cooler than rock vapor, the synestia cooled very quickly. So it could last 1,000 years or so before looking like a normal planet again. Exactly how long it lasts depends on what else is happening in the solar system around the Earth. In order to be a long lived object it would need to be very close to the star.

    What was the size of the object that struck proto-Earth?

    We can’t tell, because a variety of mass ratios, impact angles, impact velocities can make a synestia that has enough mass and angular momentum in it to make our moon. I don’t know that we will ever know for sure exactly what hit us. There may be ways for us to constrain the possibilities. One way to do that is to look deep in the Earth for clues about how large the event could have been. There are chemical tracers from the deep mantle that indicate that the Earth wasn’t completely melted and mixed, even by the moon-forming event. Those reach the surface through what are called ocean island basalts, sometimes called mantle plumes, from near the core-mantle boundary, up through the whole mantle to the surface. It could be that that could be used as a constraint on being too big. Because the Earth and the moon are very similar in the mantles of the two bodies, that can be used to determine what is too small of an event. That would give us a range that can probably be satisfied by a number of different impact configurations.

    How much energy does it take to form a synestia?

    Giant impacts are tremendously energetic events. The energy of the event, in terms of the kinetic energy of the impact, is released over hours. The power involved is similar to the power, or luminosity, of the sun. We really cannot think of the Earth as looking anything like the Earth when you’ve just dumped the energy of the sun into this planet.

    How common are synestias?

    We actually think that synestias should happen quite frequently during rocky planet formation. We haven’t looked at the gas giant planets. There are some different physics that happen with those. But for growing rocky bodies like the Earth, we attempted to estimate the statistics of how often there should be synestias. And for Earth-mass bodies anywhere in the universe probably, the body is a synestia at least once while it’s growing. The likelihood of making a synestia goes up as the bodies become larger. Super-Earths also should have been a synestia at some point.

    You say that all of the pressures and temperatures reached during planet formation are now accessible in the laboratory. First, give us a sense of the magnitude of those pressures and temperatures, and then tell us how accessing them in labs is possible.

    The center of the Earth is at several thousand degrees, and has hundreds of gigapascals of pressure—about 3 million times more pressure than the surface. Jupiter’s center is even hotter. The center-of-Jupiter pressures can be reached temporarily during a giant impact, as the bodies are colliding together. A giant impact and the center of Jupiter are about the limits of the pressures and temperatures reached during planet formation: so tens of thousands of degrees, and a million times the pressure of the Earth. To replicate that, we need to dump energy into our rock or mineral very quickly in order to generate a shockwave that reaches these amplitudes in pressure and temperature. We use major minerals in the Earth, or rocky planets—so we’ve studied iron, quartz, forsterite, enstatite, and different alloy compositions of those. Other people have studied the hydrogen helium mixture for Jupiter, and ices for Uranus and Neptune. In my lab we have light gas guns, essentially cannons. And, using compressed hydrogen, we can launch a metal flyer plate—literally a thin disk—to almost 8 kilometers per second. We can reach the core pressures in the Earth, but I can’t reach the range of giant impacts or the center of Jupiter in my lab. But the Sandia Z machine, which is a big capacitor that launches metal plates using a magnetic force, can reach 40 kilometers per second. And with the National Ignition Facility laser at Lawrence Livermore National Lab, we can reach the pressures at the center of Jupiter.

    Sandia Z machine

    National Ignition Facility at LLNL

    What happens to the flyer plates when they’re shot?

    The target simply gets turned to dust after being vaporized and then cooling again. They’re very destructive experiments. You have to make real time measurements—of the wave itself and how fast it’s traveling—within tens of nanoseconds. That we can translate to pressure. My group has spent a lot of time developing ways to measure temperature, and to find phase boundaries. The work that led to the origin of the moon was specifically studying what it takes to vaporize Earth materials, and to determine the boiling points of rocks. We needed to know when it would be vaporized in order to calculate when something would become a synestia.

    How do you use your experimental results?

    What runs in our code is a simplified version of a planet. With our experiments we can simulate a simplified planet to infer the more complicated chemical system. Once we’ve determined the pressure-temperature of the average system, you can ask more detailed questions about the multi-component chemistry of a real planet. In the moon paper that was published this year, there’s two big sections. One that does the simplified modeling of the giant impact—it gives us the pressure-temperature range in the synestia. Then another that looks at the chemistry of the system that starts at these high pressures and temperatures and cools, but now using a more realistic model for the Earth.

    What was it like to get a call from the MacArthur Foundation?

    It did come out of the blue. They called me in my office, and I answered the phone. There were three people on the other end, and they said they were from the MacArthur Foundation. I knew what it was, and I stopped listening, because it was such a nice surprise. To me it probably is just unreal at the moment, meaning it will probably take some time to really sink in.

    How did you come to study planetary physics?

    I had enjoyed science fiction, not thinking I was going to be a scientist. But while I was in high school I had phenomenal math and physics teachers. That really grabbed my interest, so when I went to college I wanted to be a physics major. I quickly learned that the astronomers very much welcomed undergraduate researchers because the work was very accessible to someone with undergraduate skills. I met amazing scientists, and that sparked a whole career.

    What would you be doing if you weren’t a scientist?

    That’s hard. Because it has been my ideal for a very long time. In college I did a lot of theater. More theater than homework. The best theatrical experience I had was directing Sweeney Todd. It was absolutely amazing. So I did watch with some envy as some of my friends pursued a theatrical life. That is something that you can be wistful about, except that that would have been a hard path.

    NASA is celebrating its 60th anniversary. What does that mean to you as a scientist studying space?

    It feels like we’ve learned so much over 60 years, because we’ve had our first visits to everything in the solar system now. But at the same time, we’re completely surprised every time we arrive at a new object. So in some ways we’re still in the youthful period in planetary science, where we’re trying to work out basic knowledge. That’s a very exciting time. We’re still on a very big growth curve.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 2:23 pm on October 21, 2018 Permalink | Reply
    Tags: Are Black Holes Actually Dark Energy Stars?, , , , , , Nautilus   

    From Nautilus: “Are Black Holes Actually Dark Energy Stars?” 

    Nautilus

    From Nautilus

    Oct 15, 2018
    Jesse Stone

    1
    George Chapline believes that the Event Horizon Telescope will offer evidence that black holes are really dark energy stars. NASA.

    What does the supermassive black hole at the center of the Milky Way look like? Early next year, we might find out. The Event Horizon Telescope—really a virtual telescope with an effective diameter of the Earth—has been pointing at Sagittarius A* for the last several years.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    NSF CfA Greenland telescope

    Greenland Telescope

    Future Array/Telescopes

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    Most researchers in the astrophysics community expect that its images, taken from telescopes all over the Earth, will show the telltale signs of a black hole: a bright swirl of light, produced by a disc of gases trapped in the black hole’s orbit, surrounding a black shadow at the center—the event horizon. This encloses the region of space where the black-hole singularity’s gravitational pull is too strong for light to escape.

    But George Chapline, a physicist at the Lawrence Livermore National Laboratory, doesn’t expect to see a black hole. He doesn’t believe they’re real. In 2005, he told Nature that “it’s a near certainty that black holes don’t exist” and—building on previous work he’d done with physics Nobel laureate Robert Laughlin—introduced an alternative model that he dubbed “dark energy stars.” Dark energy is a term physicists use to describe a peculiar kind of energy that appears to permeate the entire universe.

    Dark energy depiction. Image: Volker Springle/Max Planck Institute for Astrophysics/SP)

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    It expands the fabric of spacetime itself, even as gravity attempts to bring objects closer together. Chapline believes that the immense energies in a collapsing star cause its protons and neutrons to decay into a gas of photons and other elementary particles, along with what he refers to as “droplets of vacuum energy.” These form a “condensed” phase of spacetime—much like a gas under enough pressure transitions to liquid—that has a much higher density of dark energy than the spacetime surrounding the star. This provides the pressure necessary to hold gravity at bay and prevent a singularity from forming. Without a singularity in spacetime, there is no black hole.

    The idea has found no support in the astrophysical community—over the last decade, Chapline’s papers on this topic have garnered only single-digit citations. His most popular paper in particle physics, by contrast, has been cited over 600 times. But Chapline suspects his days of wandering in the scientific wilderness may soon be over. He believes that the Event Horizon Telescope will offer evidence that dark energy stars are real.

    The idea goes back to a 2000 paper [International Journal of Modern Physics A], with Evan Hohlfeld and David Santiago, in which Chapline and Laughlin modeled spacetime as a Bose-Einstein condensate—a state of matter that arises when taking an extremely low-density gas to extremely low temperatures, near absolute zero. Chapline and Laughlin’s model is quantum mechanical in nature: General relativity emerges as a consequence of the way that the spacetime condensate behaves on large scales. Spacetime in this model also undergoes phase transformations when it gains or loses energy. Other scientists find this to be a promising path, too. A 2009 paper [Physical Review A] by a group of Japanese physicists stated that “[Bose-Einstein Condensates] are one of the most promising quantum fluids for” analogizing curved spacetime.

    Chapline and Laughlin argue that they can describe the collapsed stars that most scientists take to be black holes as regions where spacetime has undergone a phase transition. They find that the laws of general relativity are valid everywhere in the vicinity of the collapsed star, except at the event horizon, which marks the boundary between two different phases of spacetime.

    In the condensate model the event horizon surrounding a collapsed star is no longer a point of no return but instead a traversable, physical surface. This feature, along with the lack of a singularity that is the signature feature of black holes, means that paradoxes associated with black holes, like the destruction of information, don’t arise. Laughlin has been reticent to conjecture too far beyond his and Chapline’s initial ideas. He believes Chapline is onto something with dark energy stars, “but where we part company is in the amount of speculating we are willing to do about what ‘phase’ of the vacuum might be inside” what most scientists call black holes, Laughlin said. He’s holding off until experimental data reveals more about the interior phase. “I will then write my second paper on the subject,” he said.

    In recent years Chapline has continued to refine his dark energy star model in collaboration with several other authors, including Pawel Mazur of the University of South Carolina and Piotr Marecki of Leipzig University. He’s concluded that dark energy stars aren’t spherical or oblate, like black holes. Instead, they have the shape of a torus, or donut. In a rotating compact object, like a dark energy star, Chapline believes quantum effects in the spacetime condensate generate a large vortex along the object’s axis of rotation. Because the region inside the vortex is empty—think of the depression that forms at the center of whirlpool—the center of the dark energy star is hollow, like an apple without its core. A similar effect is observed when quantum mechanics is used to model rotating drops of superfluid. There too, a central vortex can form at the center of a rotating drop and, surprisingly, change its shape from a sphere to a torus.

    For Chapline, this strange toroidal geometry isn’t a bug of dark energy stars, but a feature, as it helps explain the origin and shape of astrophysical jets—the highly energetic beams of ionized matter that are generated along the axis of rotation of a compact object like a black hole. Chapline believes he’s identified a mechanism in dark energy stars that explains observations of astrophysical jets better than mainstream ones, which posit that energy is extracted from the accretion disk outside of a black hole and focused into a narrow beam along the black hole’s axis of rotation. To Chapline, matter and energy falling toward a dark energy star would make its way to the inner throat (the “donut hole”), where electrons orbiting the throat would, as in a Biermann Battery, generate magnetic fields powerful enough to drive the jets.

    Chapline points to recent experimental work where scientists, at the OMEGA Laser Facility at the University of Rochester, created magnetized jets using lasers to form a ring-like excitation on a flat surface.

    U Rochester Omega Laser facility

    Though the experiments were not conducted with dark energy stars in mind, Chapline believes it provides support for his theory since the ring-like excitation—Chapline calls it a “ring of fire”—is exactly what he would expect to happen along the throat of a dark energy star. He believes the ring could be the key to supporting the existence of dark energy stars. “This ought to eventually show up clearly” in the Event Horizon Telescope images, Chapline said, referring to the ring.

    3
    Black hole vs dark energy star: When viewed from the top down, a dark energy star has a central opening, the donut hole. Chapline believes that matter and energy rotating around the central opening (forming the “ring of fire”) is the source of the astrophysical jets observed by astronomers in the vicinity of what most believe to be black holes. No image credit.

    Chapline also points out that dark energy stars will not be completely opaque to light, as matter and light can pass into, but also out of, a dark energy star. A dark energy star won’t have a completely black interior—instead it will show a distorted image of any stars behind it. Other physicists, though, are skeptical that these kinds of deviations from conventional black hole models would show up in the Event Horizon Telescope data. Raul Carballo-Rubio, a physicist at the International School for Advanced Studies, in Trieste, Italy, has developed his own alternative model to black holes known as semi-classical relativistic stars. Speaking more generally about alternative black hole models Caraballo-Rubio said, “The differences [with black holes] that would arise in these models are too minute to be detected” by the Event Horizon Telescope.

    Chapline plans to discuss his dark energy star predictions in December, at the Kavli Institute for Theoretical Physics in Santa Barbara. But even if his predictions are confirmed, he said he doesn’t expect the scientific community to become convinced overnight. “I expect that for the next few years the [Event Horizon Telescope] people will be confused by what they see.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 1:39 pm on September 30, 2018 Permalink | Reply
    Tags: , , , Nautilus, Top 10 Design Flaws in the Human Body   

    From Nautilus: “Top 10 Design Flaws in the Human Body” 

    Nautilus

    From Nautilus

    May 14, 2015 [Just now in social media]
    By Chip Rowe Illustrations by Len Small

    From our knees to our eyeballs, our bodies are full of hack solutions [Did G-d do a bad job?].

    1

    The Greeks were obsessed with the mathematically perfect body. But unfortunately for anyone chasing that ideal, we were designed not by Pygmalion, the mythical sculptor who carved a flawless woman, but by MacGyver. Evolution constructed our bodies with the biological equivalent of duct tape and lumber scraps. And the only way to refine the form (short of an asteroid strike or nuclear detonation to wipe clean the slate) is to jerry-rig the current model. “Evolution doesn’t produce perfection,” explains Alan Mann, a physical anthropologist at Princeton University. “It produces function.”

    With that in mind, I surveyed anatomists and biologists to compile a punch list for the human body, just as you’d do before buying a house. Get out your checkbook. This one’s a fixer-upper.

    1. An unsound spine

    Problem: Our spines are a mess. It’s a wonder we can even walk, says Bruce Latimer, director of the Center for Human Origins at Case Western Reserve University, in Cleveland. When our ancestors walked on all fours, their spines arched, like a bow, to withstand the weight of the organs suspended below. But then we stood up. That threw the system out of whack by 90 degrees, and the spine was forced to become a column. Next, to allow for bipedalism, it curved forward at the lower back. And to keep the head in balance—so that we didn’t all walk around as if doing the limbo—the upper spine curved in the opposite direction. This change put tremendous pressure on the lower vertebrae, sticking about 80 percent of adults, according to one estimate, with lower back pain.
    Fix: Go back to the arch. “Think of your dog,” Latimer says. “From the sacrum to the neck, it’s a single bow curve. That’s a great system.” Simple. Strong. Pain-free. There’s only one catch: To keep the weight of our heads from pitching us forward, we’d need to return to all fours.

    2. An inflexible knee

    Problem: As Latimer says, “You take the most complex joint in the body and put it between two huge levers—the femur and the tibia—and you’re looking for trouble.” The upshot is your knee only rotates in two directions: forward and back. “That’s why every major sport, except maybe rugby, makes it illegal to clip, or hit an opponent’s knee from the side.”

    2

    Fix: Replace this hinge with a ball and socket, like in your shoulders and hips. We never developed this type of joint at the knee “because we didn’t need it,” Latimer says. “We didn’t know about football.”

    3. A too-narrow pelvis

    Problem: Childbirth hurts. And to add insult to injury, the width of a woman’s pelvis hasn’t changed for some 200,000 years, keeping our brains from growing larger.
    Fix: Sure, you could stretch out the pelvis, Latimer says, but technologists may already be onto a better solution. “I would bet that in 10,000 years, or even in 1,000 years, no woman in the developed world will deliver naturally. A clinic will combine the sperm and egg, and you’ll come by and pick up the kid.”

    4. Exposed testicles

    Problem: A man’s life-giving organs hang vulnerably outside the body.
    Fix: Moving the testicles indoors would save men the pain of getting hit in the nuts. To accomplish this, first you’d need to tweak the sperm, says Gordon Gallup, an evolutionary psychologist at the State University of New York at Albany. Apparently the testicles (unlike the ovaries) get thrown out in the cold because sperm must be kept at 2.5 to 3 degrees Fahrenheit below the body’s internal temperature. Gallup hypothesizes that these lower temperatures keep sperm relatively inactive until they enter the warm confines of a vagina, at which point they go racing off to fertilize the egg.1 This evolutionary hack prevents sperm from wearing themselves out too early. So change the algorithm, Gallup says. Keep the sperm at body temperature and make the vagina hotter. (And, by the way, there’s no need to draw up new blueprints: Elephants offer a pretty good prototype.)

    5. Crowded teeth

    Problem: Humans typically have three molars on each side of the upper and lower jaws near the back of the mouth. When our brain drastically expanded in size, the jaw grew wider and shorter, leaving no room for the third, farthest back molars. These cusped grinders may have been useful before we learned to cook and process food. But now the “wisdom teeth” mostly just get painfully impacted in the gums.
    Fix: Get rid of them. At one point, they appeared to be on their way out—about 25 percent of people today (most commonly Eskimos) are born without some or all of their third molars. In the meantime, we’ve figured out how to safely extract these teeth with dental tools, which, Mann notes, we probably wouldn’t have invented without the bigger brains. So you could call it a wash.

    6. Meandering arteries

    Problem: Blood flows into each of your arms and legs via one main artery, which enters the limb on the front side of the body, by the biceps or hip flexors. To supply blood to tissues at a limb’s back side, such as the triceps and hamstrings, the artery branches out, taking circuitous routes around bones and bundling itself with nerves. This roundabout plumbing can make for some rather annoying glitches. At the elbow, for instance, an artery branch meets up with the ulnar nerve, which animates your little finger, just under the skin. That’s why your arm goes numb when the lower tip of your upper arm bone, called the humerus or “funny bone,” takes a sharp blow.
    The Fix: Feed a second artery into the back side of each arm and leg, by the shoulder blades or buttock, says Rui Diogo, an assistant professor of anatomy at Howard University, in Washington, DC, who studies the evolution of primate muscles. This extra pipe would provide a more direct route from the shoulder to the back of the hand, preventing vessels and nerves from wandering too close to the skin.

    7. A backward retina

    Problem: The photoreceptor cells in the retina of the eye are like microphones facing backward, writes Nathan Lents, an associate professor of molecular biology at the City University of New York. This design forces light to travel the length of each cell, as well as through blood and tissue, to reach the equivalent of a receiver on the cell’s backside. The setup may encourage the retina to detach from its supporting tissue—a leading cause of blindness. It also creates a blind spot where cell fibers, akin to microphone cables, converge at the optic nerve—making the brain refill the hole.
    Fix: Poach the obvious solution from the octopus or the squid: Just flip the retina.

    3

    8. A misrouted nerve

    Problem: The recurrent laryngeal nerve (RLN) plays a vital role in our ability to speak and swallow. It feeds instructions from the brain to the muscles of the voice box, or larynx, below the vocal cords. Theoretically, the trip should be a quick one. But during fetal development, the RLN gets entwined in a tiny lump of tissue in the neck, which descends to become blood vessels near the heart. That drop causes the nerve to loop around the aorta before traveling back up the larynx. Having this nerve in your chest makes it vulnerable during surgery—or a fist fight.
    Fix: “This one’s easy,” says Rebecca Z. German, a professor of anatomy and neurobiology at Northeast Ohio Medical University, in Rootstown. While a baby is in utero, develop the RCN after sending that irksome neck lump of vessel tissue to the chest. That way, the nerve won’t get dragged down with it.

    9. A misplaced voice box

    Problem: The trachea (windpipe) and esophagus (food pipe) open into the same space, the pharynx, which extends from the nose and mouth to the larynx (voice box). To keep food out of the trachea, a leaf-shaped flap called the epiglottis reflexively covers the opening to the larynx whenever you swallow. But sometimes, the epiglottis isn’t fast enough. If you’re talking and laughing while eating, food may slip down and get lodged in your airway, causing you to choke.
    Fix: Take a cue from whales, whose larynx is located in their blowholes. If we moved the larynx into our nose, says German, we could have two independent tubes. Sure, we’d lose the ability to talk. But we could still communicate in song, as whales do, through vibrations in our nostrils.

    10. A klugey brain

    Problem: The human brain evolved in stages. As new additions were being built, older parts had to remain online to keep us up and running, explains psychologist Gary Marcus in his book Kluge: The Haphazard Evolution of the Mind.2 And that live-in construction project led to slapdash workarounds. It’s as if the brain were a dysfunctional workplace, where young employees (the forebrain) handled newfangled technologies like language while the old guard (the midbrain and hindbrain) oversaw the institutional memory—and the fuse box in the basement. A few outcomes: depression, madness, unreliable memories, and confirmation bias.
    Fix: We’re screwed.

    6

    References

    1. Gallup, G.G., Finn, M.M., & Sammis, B. On the origin of descended scrotal testicles: The activation hypothesis. Evolutionary Psychology 7, 517-526 (2009).

    2. Marcus, G. Kluge: The Haphazard Evolution of the Human Mind Houghton Mifflin, Boston, MA (2008).

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 1:08 pm on September 30, 2018 Permalink | Reply
    Tags: Nautilus, Planck time, , Time, Time can now be sliced into slivers as thin as one ten-trillionth of a second   

    From Nautilus: “Is It Time to Get Rid of Time?” 

    Nautilus

    From Nautilus

    September 20, 2018
    Marcia Bartusiak

    1
    No image credit.

    The crisis inside the physics of time.

    Poets often think of time as a river, a free-flowing stream that carries us from the radiant morning of birth to the golden twilight of old age. It is the span that separates the delicate bud of spring from the lush flower of summer.

    Physicists think of time in somewhat more practical terms. For them, time is a means of measuring change—an endless series of instants that, strung together like beads, turn an uncertain future into the present and the present into a definite past.

    The very concept of time allows researchers to calculate when a comet will round the sun or how a signal traverses a silicon chip. Each step in time provides a peek at the evolution of nature’s myriad phenomena.

    In other words, time is a tool. In fact, it was the first scientific tool. Time can now be sliced into slivers as thin as one ten-trillionth of a second.

    Planck Time. Universe Today

    1
    FromQuarkstoQuasars

    But what is being sliced? Unlike mass and distance, time cannot be perceived by our physical senses. We don’t see, hear, smell, touch, or taste time. And yet we somehow measure it. As a cadre of theorists attempt to extend and refine the general theory of relativity, Einstein’s momentous law of gravitation, they have a problem with time. A big problem.

    2
    Slicing it thin: A hydrogen maser clock keeps time by exploiting the so-called hyperfine transition.Wikimedia Commons

    “It’s a crisis,” says mathematician John Baez, of the University of California at Riverside, “and the solution may take physics in a new direction.” Not the physics of our everyday world. Stopwatches, pendulums, and hydrogen maser clocks will continue to keep track of nature quite nicely here in our low-energy earthly environs. The crisis arises when physicists attempt to merge the macrocosm—the universe on its grandest scale—with the microcosm of subatomic particles.

    Under Newton, time was special. Every moment was tallied by a universal clock that stood separate and apart from the phenomenon under study. In general relativity, this is no longer true. Einstein declared that time is not absolute—no particular clock is special—and his equations describing how the gravitational force works take this into account. His law of gravity looks the same no matter what timepiece you happen to be using as your gauge. “In general relativity time is completely arbitrary,” explains theoretical physicist Christopher Isham of Imperial College in London. “The actual physical predictions that come out of general relativity don’t depend on your choice of a clock.” The predictions will be the same whether you are using a clock traveling near the speed of light or one sitting quietly at home on a shelf.

    The choice of clock is still crucial, however, in other areas of physics, particularly quantum mechanics. It plays a central role in Erwin Schrödinger’s celebrated wave equation of 1926. The equation shows how a subatomic particle, whether traveling alone or circling an atom, can be thought of as a collection of waves, a wave packet that moves from point to point in space and from moment to moment in time.

    According to the vision of quantum mechanics, energy and matter are cut up into discrete bits, called quanta, whose motions are jumpy and blurry. They fluctuate madly. The behavior of these particles cannot be worked out exactly, the way a rocket’s trajectory can. Using Schrödinger’s wave equation, you can only calculate the probability that a particle—a wave packet—will attain a certain position or velocity. This is a picture so different from the world of classical physics that even Einstein railed against its indeterminacy. He declared that he could never believe that God would play dice with the world.

    You might say that quantum mechanics introduced a fuzziness into physics: You can pinpoint the precise position of a particle, but at a trade-off; its velocity cannot then be measured very well. Conversely, if you know how fast a particle is going, you won’t be able to know exactly where it is. Werner Heisenberg best summarized this strange and exotic situation with his famous uncertainty principle. But all this action, uncertain as it is, occurs on a fixed stage of space and time, a steadfast arena. A reliable clock is always around—is always needed, really—to keep track of the goings-on and thus enable physicists to describe how the system is changing. At least, that’s the way the equations of quantum mechanics are now set up.

    And that is the crux of the problem. How are physicists expected to merge one law of physics—namely gravity—that requires no special clock to arrive at its predictions, with the subatomic rules of quantum mechanics, which continue to work within a universal, Newtonian time frame? In a way, each theory is marching to the beat of a different drummer (or the ticking of a different clock).

    That’s why things begin to go a little crazy when you attempt to blend these two areas of physics. Although the scale on which quantum gravity comes into play is so small that current technology cannot possibly measure these effects directly, physicists can imagine them. Place quantum particles on the springy, pliable mat of spacetime, and it will bend and fold like so much rubber. And that flexibility will greatly affect the operation of any clock keeping track of the particles. A timepiece caught in that tiny submicroscopic realm would probably resemble a pendulum clock laboring amid the quivers and shudders of an earthquake. “Here the very arena is being subjected to quantum effects, and one is left with nothing to stand on,” explains Isham. “You can end up in a situation where you have no notion of time whatsoever.” But quantum calculations depend on an assured sense of time.

    For Karel Kucha, a general relativist and professor emeritus at the University of Utah, the key to measuring quantum time is to devise, using clever math, an appropriate clock—something he has been attempting, off and on, for several decades. Conservative by nature, Kucha believes it is best to stick with what you know before moving on to more radical solutions. So he has been seeking what might be called the submicroscopic version of a Newtonian clock, a quantum timekeeper that can be used to describe the physics going on in the extraordinary realm ruled by quantum gravity, such as the innards of a black hole or the first instant of creation.

    Unlike the clocks used in everyday physics, Kucha’s hypothetical clock would not stand off in a corner, unaffected by what is going on around it. It would be set within the tiny, dense system where quantum gravity rules and would be part and parcel of it. This insider status has its pitfalls: The clock would change as the system changed—so to keep track of time, you would have to figure out how to monitor those variations. In a way, it would be like having to pry open your wristwatch and check its workings every time you wanted to refer to it.

    The most common candidates for this special type of clock are simply “matter clocks.” “This, of course, is the type of clock we’ve been used to since time immemorial. All the clocks we have around us are made up of matter,” Kucha points out. Conventional timekeeping, after all, means choosing some material medium, such as a set of particles or a fluid, and marking its changes. But with pen and paper, Kucha mathematically takes matter clocks into the domain of quantum gravity, where the gravitational field is extremely strong and those probabilistic quantum-mechanical effects begin to arise. He takes time where no clock has gone before.

    But as you venture into this domain, says Kucha, “matter becomes denser and denser.” And that’s the Achilles heel for any form of matter chosen to be a clock under these extreme conditions; it eventually gets squashed. That may seem obvious from the start, but Kucha needs to examine precisely how the clock breaks down so he can better understand the process and devise new mathematical strategies for constructing his ideal clock.

    More promising as a quantum clock is the geometry of space itself: monitoring spacetime’s changing curvature as the infant universe expands or a black hole forms. Kucha surmises that such a property might still be measurable in the extreme conditions of quantum gravity. The expanding cosmos offers the simplest example of this scheme. Imagine the tiny infant universe as an inflating balloon. Initially, its surface bends sharply around. But as the balloon blows up, the curvature of its surface grows shallower and shallower. “The changing geometry,” explains Kucha, “allows you to see that you are at one instant of time rather than another.” In other words, it can function as a clock.

    Unfortunately, each type of clock that Kucha has investigated so far leads to a different quantum description, different predictions of the system’s behavior. “You can formulate your quantum mechanics with respect to one clock that you place in spacetime and get one answer,” explains Kucha.

    “But if you choose another type of clock, perhaps one based on an electric field, you get a completely different result. It is difficult to say which of these descriptions, if any, is correct.”

    More than that, the clock that is chosen must not eventually crumble. Quantum theory suggests there is a limit to how fine you can cut up space. The smallest quantum grain of space imaginable is 10^33 centimeter wide, the Planck length, named after Max Planck, inventor of the quantum. On that infinitesimal scale, the spacetime canvas turns choppy and jumbled, like the whitecaps on an angry sea. Space and time become unglued and start to wink in and out of existence in a probabilistic froth. Time and space, as we know them, are no longer easily defined. This is the point at which the physics becomes unknown and theorists start walking on shaky ground. As physicist Paul Davies points out in his book About Time, “You must imagine all possible geometries—all possible spacetimes, space warps and time warps—mixed together in a sort of cocktail, or ‘foam.’ ”

    Only a fully developed theory of quantum gravity will show what’s really happening at this unimaginably small level of spacetime. Kucha conjectures that some property of general relativity (as yet unknown) will not undergo quantum fluctuations at this point. Something might hold on and not come unglued. If that’s true, such a property could serve as the reliable clock that Kucha has been seeking for so long. And with that hope, Kucha continues to explore, one by one, the varied possibilities.

    Kucha has been trying to mold general relativity into the style of quantum mechanics, to find a special clock for it. But some other physicists trying to understand quantum gravity believe that the revision should happen the other way around—that quantum gravity should be made over in the likeness of general relativity, where time is pushed into the background. Carlo Rovelli is a champion of this view.

    Forget time,” Rovelli declares emphatically. “Time is simply an experimental fact.” Rovelli, a physicist at the Center of Theoretical Physics in France, has been working on an approach to quantum gravity that is essentially timeless. To simplify the calculations, he and his collaborators, physicists Abhay Ashtekar and Lee Smolin, set up a theoretical space without a clock. In this way, they were able to rewrite Einstein’s general theory of relativity, using a new set of variables so that it could more easily be interpreted and adapted for use on the quantum level.

    Their formulation has allowed physicists to explore how gravity behaves on the subatomic scale in a new way. But is that really possible without any reference to time at all? “First with special relativity and then with general relativity, our classical notion of time has only gotten weaker and weaker,” answers Rovelli. “We think in terms of time. We need it. But the fact that we need time to carry out our thinking does not mean it is reality.”

    Rovelli believes if physicists ever find a unified law that links all the forces of nature under one banner, it will be written without any reference to time. “Then, in certain situations,” says Rovelli, “as when the gravitational field is not dramatically strong, reality organizes itself so that we perceive a flow that we call time.”

    Getting rid of time in the most fundamental physical laws, says Rovelli, will probably require a grand conceptual leap, the same kind of adjustment that 16th-century scientists had to make when Copernicus placed the sun, and not the Earth, at the center of the universe. In so doing, the Polish cleric effectively kicked the Earth into motion, even though back then it was difficult to imagine how the Earth could zoom along in orbit about the sun without its occupants being flung off the surface. “In the 1500s, people thought a moving earth was impossible,” notes Rovelli.

    But maybe the true rules are timeless, including those applied to the subatomic world. Indeed, a movement has been under way to rewrite the laws of quantum mechanics, a renovation that was spurred partly by the problem of time, among other quantum conundrums. As part of that program, theorists have been rephrasing quantum mechanics’ most basic equations to remove any direct reference to time.

    The roots of this approach can be traced to a procedure introduced by the physicist Richard Feynman in the 1940s, a method that has been extended and broadened by others, including James Hartle of the University of California at Santa Barbara and physics Nobel laureate Murray Gell-Mann.

    Basically, it’s a new way to look at Schrödinger’s equation. As originally set up, this equation allows physicists to compute the probability of a particle moving directly from point A to point B over specified slices of time. The alternate approach introduced by Feynman instead considers the infinite number of paths the particle could conceivably take to get from A to B, no matter how slim the chance. Time is removed as a factor; only the potential pathways are significant. Summing up these potentials (some paths are more likely than others, depending on the initial conditions), a specific path emerges in the end.

    The process is sometimes compared to interference between waves. When two waves in the ocean combine, they may reinforce one another (leading to a new and bigger wave) or cancel each other out entirely. Likewise, you might think of these many potential paths as interacting with one another—some getting enhanced, others destroyed—to produce the final path. More important, the variable of time no longer enters into the calculations.

    Hartle has been adapting this technique to his pursuits in quantum cosmology, an endeavor in which the laws of quantum mechanics are applied to the young universe to discern its evolution. Instead of dealing with individual particles, though, he works with all the configurations that could possibly describe an evolving cosmos, an infinite array of potential universes. When he sums up these varied configurations—some enhancing one another, others canceling each other out—a particular spacetime ultimately emerges. In this way, Hartle hopes to obtain clues to the universe’s behavior during the era of quantum gravity. Conveniently, he doesn’t have to choose a special clock to carry out the physics: Time disappears as an essential variable.

    Of course, as Isham points out, “having gotten rid of time, we’re then obliged to explain how we get back to the ordinary world, where time surrounds us.” Quantum gravity theorists have their hunches. Like Rovelli, many are coming to suspect that time is not fundamental at all. This theme resounds again and again in the various approaches aimed at solving the problem of time. Time, they say, may more resemble a physical property such as temperature or pressure. Pressure has no meaning when you talk about one particle or one atom; the concept of pressure arises only when we consider trillions of atoms. The notion of time could very well share this statistical feature. If so, reality would then resemble a pointillist painting. On the smallest of scales—the Planck length—time would have no meaning, just as a pointillist painting, built up from dabs of paint, cannot be fathomed close up.

    Quantum gravity theorists like to compare themselves to archeologists. Each investigator is digging away at a different site, finding a separate artifact of some vast subterranean city. The full extent of the find is not yet realized. What theorists desperately need are data, experimental evidence that could help them decide between the different approaches.

    It seems an impossible task, one that would appear to require recreating the hellish conditions of the Big Bang. But not necessarily. For instance, future generations of “gravity-wave telescopes,” instruments that detect ripples in the rubberlike mat of spacetime, might someday sense the Big Bang’s reverberating thunder, relics from the instant of creation when the force of gravity first emerged. Such waves could provide vital clues to the nature of space and time.

    “We wouldn’t have believed just [decades] ago that it would be possible to say what happened in the first 10 minutes of the Big Bang,” points out Kucha. “But we can now do that by looking at the abundances of the elements. Perhaps if we understand physics on the Planck scale well enough, we’ll be able to search for certain consequences—remnants—that are observable today.” If found, such evidence would bring us the closest ever to our origins and possibly allow us to perceive at last how space and time came to well up out of nothingness some 14 billion years ago.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
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