December 14, 2015 at 4:45 am #45432
Note: This is an excellent summary of the current cosmological crisis of scientific materialism. In my humble view, materialism is bound to fail, it is not multi-dimensional enough. In the language of physics, this could be put as “science doesn’t grasp the possibility of spiritual gravitational forces”. Spiritual = INTELLIGENT multi-dimensional forces.
What happening on the surface of earth (within humanity) is a cosmological crisis. Solution? Cosmological Qigong or Neidangong practice. 🙂 – Michael
Astronomy Crisis Deepens As the Hubble Telescope Sees No Missing Mass
By JOHN NOBLE WILFORD
Published: November 29, 1994
IN their audacious reach for understanding of the universe, cosmologists often draw back hands that are maddeningly empty. They know, for example, there is more out there than meets the eye. But hard as they try, they are unable to grasp the nature of what lurks in the blackness enfolding the luminous stars and galaxies, that shadowy substance whose gravitational pull must be the organizing force for the evolution and overall structure of the universe.
The abundance of this invisible mass, whatever it is, could dictate the fate of the universe. Unless there is more mass than scientists so far have been able to measure or infer, that fate would appear to be bleak indeed.
Over the last two decades, evidence for this missing mass has become overwhelming and always perplexing. The stars and gas that are visible are quite inadequate to produce most of the gravity needed to account for the observed shapes and motions of galaxies. If it were not for huge quantities of some unseen matter, galaxies would not be clustering, as they tend to do, but would be flying off in all directions.
By most estimates, this missing matter constitutes more than 90 percent of the universe’s total mass. Scientists call it dark matter, descriptive not only of its invisibility but also of their own mystification.
“It’s a fairly embarrassing situation to admit that we can’t find 90 percent of the universe,” sighed Dr. Bruce H. Margon, an astrophysicist at the University of Washington at Seattle.
Identifying the nature and amount of dark matter is the central problem in cosmology today. It is an obsession of everyone concerned.
Astronomers, for all their sensitive new telescopes looking into the visible and invisible, are dismayed by their continuing failure to observe anything more than a tiny fraction of the total cosmic mass. They keep hoping that a significant portion of dark matter is made of giant planets, faint or failed stars or those powerful gravitational sinks known as black holes — all the stuff they deal in.
But two surveys by the repaired Hubble Space Telescope, announced two weeks ago, appeared to rule out a favorite explanation of astronomers for the dark matter. They had thought that dim small stars, red dwarfs, might be plentiful enough in galaxies to constitute much of the missing mass. And yet the orbiting telescope, able to detect faint stars 100 times dimmer than those seen from the ground, found that red dwarfs are actually quite sparse, a negligible component of cosmic mass.
This setback has shifted more of the burden of the search from observational astronomers to particle physicists, increasingly important players in cosmology. They seek to explain the universe in terms of concepts drawn from theory, studies of cosmic rays and atom-smashing experiments in gigantic accelerators. They strain to think of solutions to the dark-matter problem beyond the realm of ordinary matter.
Some of the cosmic mass, particle physicists suggest, could be in the form of fast-moving neutrinos, subatomic particles that pervade the universe. They are known byproducts of the Big Bang, the theorized explosive event of cosmic creation, but no one yet is sure if neutrinos have any mass. Much more of the missing mass, physicists think, could be something more exotic and sluggish, which they call cold dark matter. For various theoretical reasons, such weakly interacting massive particles, dubbed WIMP’s, could exist in great abundance. But they have never been detected.
This line of investigation could have profound philosophical implications. If most of the universe is discovered to be composed of exotic material never before seen and absolutely unlike the “ordinary” matter of stars, of Earth and of all life, cosmologists point out, the effect on human thinking could be more startling and diminishing than the Copernican revolution, which almost five centuries ago revealed that Earth was not the center of the universe or even the solar system.
For theorists, this is a time of high anxiety. As long as dark matter eludes astronomers and particle physicists, they cannot be comfortably sure of the validity of their most cherished theories. The dark matter question, said Dr. David H. Schramm, a University of Chicago astrophysicist, is “perhaps the greatest mystery remaining in the Big Bang picture of the universe.”
By learning the type and abundance of dark matter, theorists could finally solve the vexing problem of explaining how a universe that began as smooth and uniform in all directions, according to the Big Bang theory and some supporting observations, evolved into the large-scaled clumpiness of galaxies and clusters of galaxies. There has never seemed to be sufficient time or mass for such a radical transformation.
But recent maps of the heavens clearly show clusters of galaxies bigger than anyone imagined possible a few years ago. These galactic walls stretch across half a billion light-years. Compounding the problem, the Hubble telescope recently gave a measure of the expansion rate of the universe that implied its age could be as young as 8 billion years, in contrast to previous estimates that ran as high as 20 billion.
Theorists would also like to resolve the dark-matter problem because the ultimate fate of the universe will be determined by how much mass there is.
If there is sufficient mass spread over the universe, the force of gravity will eventually bring the post-Big Bang expansion to a halt and even reverse it, causing a cataclysmic collapse sometimes described as the “big crunch.” Or if there is too little mass, the weaker gravitational force would allow the universe to expand forever. Such an open universe would become vanishingly thin, populated only by gas, dust and dark cinders of dwarf stars and gripped by temperatures falling toward absolute zero — a future characterized as the “big chill.” (Not to worry; such dire fates are billions of years off.)
Between these two extremes, there is a more attractive possibility, a condition called critical density. In this case, the mass would be precisely what is necessary to keep the universe in balance between expanding forever and eventually collapsing. Such a critical density, an average throughout space of one hydrogen atom per 10 cubic meters, is usually expressed by cosmologists as omega equals one.
For theoretical and perhaps esthetic reasons, cosmologists have long been partisans of critical density. The bulk motions of galaxies on extremely large scales, associated with unseen masses known as the Great Attractor, and the measured rate at which the universe’s expansion appears to be slowing down, cosmologists argue, indicate the cosmic mass is near critical density. And the Big Bang theory seems to demand critical density.
Writing in the October issue of Sky and Telescope magazine, Dr. Schramm asserted: “In the most straightforward Big Bang model, even a microscopic deviation from omega equals one would have had disastrous results early on, at least without some special selective tuning. The newborn universe would have either recollapsed immediately into a Big Crunch or expanded and dissipated so fast that stars wouldn’t have had time to form.”
In the inflationary model, a 1981 modification of the standard Big Bang thesis in which a brief but dramatic expansion occurred in the beginning, the universe has to have precisely the critical density. Since the inflationary Big Bang is widely supported by scientists because it so neatly explains much else about cosmic history, cosmologists want to believe its predictions of critical density. Otherwise they would have lost even more than their struggle to understand dark matter.
But so far, all measurements of cosmic mass fall well short of critical density, presumably indicating an open universe on its way to the big chill. At best, said Dr. Jeremiah P. Ostriker, a Princeton University astrophysicist, combinations of visible and likely dark matter add up to no more than 20 percent or possibly 30 percent of critical density.
“A lot of people don’t think omega equals one,” said Dr. Craig J. Hogan, a University of Washington astrophysicist. “They are the empiricists, the observers. They have discovered that there really isn’t any evidence for high omega.”
Dr. John N. Bahcall, an astrophysicist at the Institute for Advanced Study in Princeton, N.J., whose research on red dwarfs seemed to limit dark-matter possibilities, put it more bluntly. “I have a feeling that we just need to admit to ourselves that the emperor has no clothes,” Dr. Bahcall said of the lack of observational evidence for critical density.
But like many specialists in the dark-matter hunt, Dr. Joel Primack, a theoretical physicist at the University of California at Santa Cruz, is not throwing in the towel. He and colleagues are developing new recipes combining neutrinos and cold dark matter like WIMP’s that they say overcome previous objections to such hybrid solutions. Recent Japanese experiments, Dr. Primack noted, provided “wonderful clues” suggesting that neutrinos could well have detectable mass and so could account for some of the missing mass required to add up to critical density.
In simulations by supercomputers, the models with neutrinos alone or cold dark matter alone failed to lead to the construction of a universe looking like it does today. Neutrinos are “hot,” in that they zip about rapidly, and could not have coalesced soon enough to have helped form galaxies. Cold dark matter, moving slowly and clumping easily, would have produced too much galactic clustering.
Even mixing the two, usually with about one-third neutrinos and two-thirds cold dark matter, has not passed computer-simulation tests; the hybrids still produce galaxies later in cosmic history than recent observations suggest. Some such mixed dark matter could finally pass the test, but many scientists are uncomfortable with such recipes, which smack of being cooked just for the purpose of crawling out of an observational and theoretical hole.
One of the most encouraging developments, astronomers say, is the growing conviction that neutrinos do have a finite mass. But will the mass be sufficient to account for a major fraction of dark matter?
Astronomers have not given up on finding more ordinary matter that could be part of the dark matter. They continue to search for low-mass stars, Jupiter-size planets and other faint objects, which they think may be littering the outer edges of galaxies. They are taking a closer look at the possibility that lower-mass black holes could play a more significant role in cosmic mass than had been thought.
“If nothing works and omega is not very close to one,” Dr. Hogan said, “then we’ve got to find some way out.”
That raises once again the issue of the cosmological constant, a concept invented by Albert Einstein in 1917 and later rejected by him as his “greatest blunder.” The idea assumes that energy in empty space might serve as a brake on cosmic expansion. If the value of the constant is reasonably low, scientists point out, it could make up the difference between the observed density of matter in the universe and the critical density so devoutly sought.
Physicists, in this their hour of need, have been re-examining the cosmological constant, finding no known principle that forbids it. Still, it makes them uneasy to be introducing such fudge factors. It reminds scientists too much of the practice of medieval astronomers to correct their Earth-centered view of the solar system by devising more and more complicated celestial mechanisms to explain the motions of planets and preserve conventional wisdom according to Ptolemy, the second-century astronomer.
The turmoil of clashing concepts and the continuing failure to find what most of the universe is made of might be cause for some to question science’s faith in the optimistic assumption, first espoused by the ancient Greeks, that the universe is comprehensible. The Greek word for universe became cosmos, meaning order.
But cosmologists insist there is no reason to despair. “It’s not frustrating,” Dr. Ostriker said of the seemingly intractable problem of dark matter. “It’s exciting.”
With the greater capacities of telescopes and other instruments, Dr. Bahcall said, “our theories are being asked to fit so much more data than 25 years ago.” It is a good sign, he added, “that our simplest models are being stretched and strained — it means we’re going to have new ideas.”
The Greeks said the universe was comprehensible; they did not say it was simple.
Diagrams: “Missing Mass Must Hold Galaxies Together” The dynamics of galaxies suggest they should fly apart unless vast quantities of hidden mass are holding them together. This and other evidence leads astronomers to think at least 90 percent of the universe must be unseen matter. “In Theory, Random Clumping” Seeing the structure of the universe, astronomers have tried to reconstruct how this structure evolved, based on the assumption that the missing mass exists. The computer model at left assumes the existence of unseen cold dark matter and random overdensities acting as seeds. “In Reality, Structure” This map of the nearby universe, based on actual observations, shows massive structures, like the great ribbon of galaxies called the Great Wall in the northern segment. Scientists still hope to explain this evolution in terms of dark matter. (Sources: “The Shadows of Creation: Dark Matter and the Structure of the Universe,” M. Riordan and D. N. Schramm (Freeman Press); M.J. Geller, J. P. Huchra, L. A. N. da Costa and E. E. Falco, Smithsonian Astrophysical Observatory) Chart: “What the Universe Is Made Of, More or Less” DARK MATTER ORDINARY Machos MASSIVE COMPACT HALO OBJECTS Very faint low-mass stars and planet-size objects (known as Jupiters) made of ordinary baryonic matter (protons and neutrons). Found in halos of matter surrounding galaxies, or in clusters of dust and gas coasting through intergalactic voids. Baryonic matter should be detectable by existing means. Limited sightings suggest this type of dark matter accounts for no more than 10 percent of the Universe’s “missing mass.” Black holes Collapsed remains of massive stars. Gravitational force so great that no light can escape. Optically invisible but detectable by gravitational influence on nearby matter. EXOTIC HOT: Fast-moving Neutrinos Electrically neutral subatomic particles produced prolifically in theBig Bang. Ultra-smallj in mass, perhaps as small as a trillionth oif a proton. Traveling at about the speed of light, they are found just about everywhere, inconcentrations of about 500 per cubic centimeter. COLD: Slow-moving Wimps WEAKLY INTERACTING MASSIVE PARTICLES Believed to exist, but never “seen”; they interact so weakly with matter that their mass has not been measured. Theoretically, they move at a slow pace and exist in very high concentrations – hundreds per cubic centimeter – and may account for a substantial chunk of the universe’s mass, if they are ever shown to have a mass of their own. Axions Wispy, superlight particles; slow-moving and highly concentrated (400 per cubic centimeter.) Very tiny mass, but measureable; plentiful enough to contribute significantly to the missing mass. (Sources: David N. Schramm; “The Shadows of Creation: Dark Matter and the Structure of the Universe,” by M. Riordan and D.N. Schramm (W.H. Freeman); Scientific American; The International Encyclopedia of Astronomy; The Associated Press) (pg. C13)December 14, 2015 at 6:50 pm #45433
I wouldn’t say this is a current summary!
It was published in 1994.
In terms of scientific knowledge, this is effectively the Stone Age.
Best not to go back more than five years to examine current cosmological thought.
However, your ultimate conclusion still holds up.
That is unchanged by modern discoveries. 🙂
SDecember 14, 2015 at 7:39 pm #45435
December 14, 2015 in Physics / General Physics
The Large Underground Xenon (LUX) dark matter experiment, which operates nearly a mile underground at the Sanford Underground Research Facility (SURF) in the Black Hills of South Dakota, has already proven itself to be the most sensitive detector in the hunt for dark matter, the unseen stuff believed to account for most of the matter in the universe. Now, a new set of calibration techniques employed by LUX scientists has again dramatically improved the detector’s sensitivity. Researchers with LUX are looking for WIMPs, or weakly interacting massive particles, which are among the leading candidates for dark matter. “We have improved the sensitivity of LUX by more than a factor of 20 for low-mass dark matter particles, significantly enhancing our ability to look for WIMPs,” said Rick Gaitskell, professor of physics at Brown University and co-spokesperson for the LUX experiment. “It is vital that we continue to push the capabilities of our detector in the search for the elusive dark matter particles,” Gaitskell said. LUX improvements, coupled to advanced computer simulations at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory’s (Berkeley Lab) National Energy Research Scientific Computing Center (NERSC) and Brown University’s Center for Computation and Visualization (CCV), have allowed scientists to test additional particle models of dark matter that now can be excluded from the search. NERSC also stores large volumes of LUX datameasured in trillions of bytes, or terabytesand Berkeley Lab has a growing role in the LUX collaboration. Scientists are confident that dark matter exists because the effects of its gravity can be seen in the rotation of galaxies and in the way light bends as it travels through the universe. Because WIMPs are thought to interact with other matter only on very rare occasions, they have yet to be detected directly. “We have looked for dark matter particles during the experiment’s first three-month run, but are exploiting new calibration techniques better pinning down how they would appear to our detector,” said Alastair Currie of Imperial College London, a LUX researcher. “These calibrations have deepened our understanding of the response of xenon to dark matter, and to backgrounds. This allows us to search, with improved confidence, for particles that we hadn’t previously known would be visible to LUX.” The new research is described in a paper submitted to Physical Review Letters. The work reexamines data collected during LUX’s first three-month run in 2013 and helps to rule out the possibility of dark matter detections at low-mass ranges where other experiments had previously reported potential detections. LUX consists of one-third ton of liquid xenon surrounded with sensitive light detectors. It is designed to identify the very rare occasions when a dark matter particle collides with a xenon atom inside the detector. When a collision happens, a xenon atom will recoil and emit a tiny flash of light, which is detected by LUX’s light sensors. The detector’s location at Sanford Lab beneath a mile of rock helps to shield it from cosmic rays and other radiation that would interfere with a dark matter signal. So far LUX hasn’t detected a dark matter signal, but its exquisite sensitivity has allowed scientists to all but rule out vast mass ranges where dark matter particles might exist. These new calibrations increase that sensitivity even further. One calibration technique used neutrons as stand-ins for dark matter particles. Bouncing neutrons off the xenon atoms allows scientists to quantify how the LUX detector responds to the recoiling process. “It is like a giant game of pool with a neutron as the cue ball and the xenon atoms as the stripes and solids,” Gaitskell said. “We can track the neutron to deduce the details of the xenon recoil, and calibrate the response of LUX better than anything previously possible.” The nature of the interaction between neutrons and xenon atoms is thought to be very similar to the interaction between dark matter and xenon. “It’s just that dark matter particles interact very much more weaklyabout a million-million-million-million times more weakly,” Gaitskell said. The neutron experiments help to calibrate the detector for interactions with the xenon nucleus. But LUX scientists have also calibrated the detector’s response to the deposition of small amounts of energy by struck atomic electrons. That’s done by injecting tritiated methanea radioactive gasinto the detector. “In a typical science run, most of what LUX sees are background electron recoil events,” said Carter Hall a University of Maryland professor. “Tritiated methane is a convenient source of similar events, and we’ve now studied hundreds of thousands of its decays in LUX. This gives us confidence that we won’t mistake these garden-variety events for dark matter.”
Another radioactive gas, krypton, was injected to help scientists distinguish between signals produced by ambient radioactivity and a potential dark matter signal. “The krypton mixes uniformly in the liquid xenon and emits radiation with a known, specific energy, but then quickly decays away to a stable, non-radioactive form,” said Dan McKinsey, a UC Berkeley physics professor and co-spokesperson for LUX who is also an affiliate with Berkeley Lab. By precisely measuring the light and charge produced by this interaction, researchers can effectively filter out background events from their search. “And so the search continues,” McKinsey said. “LUX is once again in dark matter detection mode at Sanford Lab. The latest run began in late 2014 and is expected to continue until June 2016. This run will represent an increase in exposure of more than four times compared to our previous 2013 run. We will be very excited to see if any dark matter particles have shown themselves in the new data.” McKinsey, formerly at Yale University, joined UC Berkeley and Berkeley Lab in July, accompanied by members of his research team. The Sanford Lab is a South Dakota-owned facility. Homestake Mining Co. donated its gold mine in Lead to the South Dakota Science and Technology Authority (SDSTA), which reopened the facility in 2007 with $40 million in funding from the South Dakota State Legislature and a $70 million donation from philanthropist T. Denny Sanford. The U.S. Department of Energy (DOE) supports Sanford Lab’s operations. Kevin Lesko, who oversees SURF operations and leads the Dark Matter Research Group at Berkeley Lab, said, “It’s good to see that the experiments installed in SURF continue to produce world-leading results.” The LUX scientific collaboration, which is supported by the DOE and National Science Foundation (NSF), includes 19 research universities and national laboratories in the United States, the United Kingdom and Portugal. “The global search for dark matter aims to answer one of the biggest questions about the makeup of our universe. We’re proud to support the LUX collaboration and congratulate them on achieving an even greater level of sensitivity,” said Mike Headley, Executive Director of the SDSTA. Planning for the next-generation dark matter experiment at Sanford Lab is already under way. In late 2016 LUX will be decommissioned to make way for a new, much larger xenon detector, known as the LUX-ZEPLIN (LZ) experiment. LZ would have a 10-ton liquid xenon target, which will fit inside the same 72,000-gallon tank of pure water used by LUX. Berkeley Lab scientists will have major leadership roles in the LZ collaboration.”The innovations of the LUX experiment form the foundation for the LZ experiment, which is planned to achieve over 100 times the sensitivity of LUX. The LZ experiment is so sensitive that it should begin to detect a type of neutrino originating in the Sun that even Ray Davis’ Nobel Prize-winning experiment at the Homestake mine was unable to detect,” according to Harry Nelson of UC Santa Barbara, spokesperson for LZ.December 14, 2015 at 8:00 pm #45437December 15, 2015 at 2:17 pm #45439
If you would like to read something real, rather than this new age speculation I would invite you to read some of Anadi’s articles.December 18, 2015 at 2:33 pm #45441
Bla bla bla bla ignorance bla bla bla bla dualism yadda yadda yadda yadda bla Panchkosha bla bla bla yadda yadda bla bla atman bla bla bla avidya yadda yadda bla jnana toblerone bla bla bla brahma bla parasite bla bla bla bla bla vedanta bla bla lineage yadda yadda yadda and a partridge in a pear tree.
-http://forum.healingdao.com/general/message/26076/December 18, 2015 at 2:36 pm #45443December 18, 2015 at 7:02 pm #45445
At the time the book was written, it had been noted that the conditions of the Universe are very fine tuned, allowing life. However, at the same time it is unknown why. The Anthropic principle was one solution, but was rejected by many physicists who preferred a more elegant solution. String theory was then created, but allowed too many solutions. Then, in the book, Susskind hypothesized that there are multiverses where there are occasional universes where life is indeed possible. He calls this multiverse the “landscape”.
Knocking on Heavens Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World is the second non-fiction book by Lisa Randall. It was initially published on September 20, 2011 by Ecco Press. The title is explained in the text: “Scientists knock on heaven’s door in an attempt to cross the threshold separating the known from the unknown.”
Randalls new book, … takes us 10 years past her initial conjectures and in some ways may be even more ambitious. As the subtitle indicates, she wishes to take up larger questions about the nature of scientific thinking, including its relation to religion and its reliance on probability. At the same time, she wishes to bring her audience up to date regarding the status of her theory within the larger ambit of particle physics and cosmology as the Large Hadron Collider (LHC) begins its work, a monumental collaboration involving the whole world. (Americans are the largest single nationality involved in its operation, although the United States is not an official member state of CERN, its operating consortium.)The resulting book is valuable and engaging; like its predecessor, it is a tour de force of popularization. The good part about its wider ambition emerges in Randalls clarification of the exact purport and scope of scientific work. But as she interweaves this with descriptions of theories and experiments, past and present, the reader may feel some tension between her somewhat divergent goals, which work together but also divide the readers attention and hence lead to organizational challenges.
For the last eighteen years particle theory has been dominated by a single approach to the unification of the Standard Model interactions and quantum gravity. This line of thought has hardened into a new orthodoxy that postulates an unknown fundamental supersymmetric theory involving strings and other degrees of freedom with characteristic scale around the Planck length. [ ] It is a striking fact that there is absolutely no evidence whatsoever for this complex and unattractive conjectural theory. There is not even a serious proposal for what the dynamics of the fundamental ‘M-theory’ is supposed to be or any reason at all to believe that its dynamics would produce a vacuum state with the desired properties. The sole argument generally given to justify this picture of the world is that perturbative string theories have a massless spin two mode and thus could provide an explanation of gravity, if one ever managed to find an underlying theory for which perturbative string theory is the perturbative expansion.
There is also a balance point between worldly desire and spiritual desire. As I said before, each of us has only a limited amount of time on this planet. Spend all of your time practicing, and you give up your experiences of the world. These are valuable and provide growth in their own right.
Sorry for my broken English.
…in terms of scientific knowledge, this is effectively the Stone Age…
Maybe one should ask if any kind of of technical, scientific and also mathematical endeavours are at all healthy.
Ps. If one wants very quick and easy introduction to physics for example these two are good enough. Susskind’s book has much better text but miserable pictures; Randall’s book has very nice pictures.January 11, 2016 at 2:07 pm #45447
It’s just wrong, as is much of relativity.
The “Universe” is eternal; it explodes in pockets.
Our local region has evidence which will show a local 400 billion year “Wall” formation. Inflation is a false mechanism to explain the expansion of the absurd “Big Bang”. Bangs yes,
one “Big Bang” is mythology.
It’s eternal through inverse cycling, with regions at 1000’s of billions of years+.
The speed of light limit of relativity is equally a mythology, which the entire theory is based around. It is convenient because it allows gravitational curvature equations.
The “medium” behaves like a liquid until it lightens in density and “clarifies” into the “vacuum”. Acceleration does NOT “warp” space-time; you are traveling against a medium.
It’s an episode in academic mythology which was useful to analyze data, now given as “fact”…
The star may be mis-dated, the walls are not…
The core boson physics reveal a regeneration mechanism which allows the cycling.
One of the solutions is PHI, which holds the white hole nucleus inside the “multiverse’s” infinite/eternal regeneration. That’s the Divine Spiral.January 17, 2016 at 3:06 am #45449
January 14, 2016
Standard cosmologythat is, the Big Bang Theory with its early period of exponential growth known as inflationis the prevailing scientific model for our universe, in which the entirety of space and time ballooned out from a very hot, very dense point into a homogeneous and ever-expanding vastness. This theory accounts for many of the physical phenomena we observe. But what if that’s not all there was to it?
A new theory from physicists at the U.S. Department of Energy’s Brookhaven National Laboratory, Fermi National Accelerator Laboratory, and Stony Brook University, which will publish online on January 18 in Physical Review Letters, suggests a shorter secondary inflationary period that could account for the amount of dark matter estimated to exist throughout the cosmos.
“In general, a fundamental theory of nature can explain certain phenomena, but it may not always end up giving you the right amount of dark matter,” said Hooman Davoudiasl, group leader in the High-Energy Theory Group at Brookhaven National Laboratory and an author on the paper. “If you come up with too little dark matter, you can suggest another source, but having too much is a problem.”
Measuring the amount of dark matter in the universe is no easy task. It is dark after all, so it doesn’t interact in any significant way with ordinary matter. Nonetheless, gravitational effects of dark matter give scientists a good idea of how much of it is out there. The best estimates indicate that it makes up about a quarter of the mass-energy budget of the universe, while ordinary matterwhich makes up the stars, our planet, and uscomprises just 5 percent. Dark matter is the dominant form of substance in the universe, which leads physicists to devise theories and experiments to explore its properties and understand how it originated.
Some theories that elegantly explain perplexing oddities in physicsfor example, the inordinate weakness of gravity compared to other fundamental interactions such as the electromagnetic, strong nuclear, and weak nuclear forcescannot be fully accepted because they predict more dark matter than empirical observations can support.
This new theory solves that problem. Davoudiasl and his colleagues add a step to the commonly accepted events at the inception of space and time.
In standard cosmology, the exponential expansion of the universe called cosmic inflation began perhaps as early as 10-35 seconds after the beginning of timethat’s a decimal point followed by 34 zeros before a 1. This explosive expansion of the entirety of space lasted mere fractions of a fraction of a second, eventually leading to a hot universe, followed by a cooling period that has continued until the present day. Then, when the universe was just seconds to minutes oldthat is, cool enoughthe formation of the lighter elements began. Between those milestones, there may have been other inflationary interludes, said Davoudiasl.
“They wouldn’t have been as grand or as violent as the initial one, but they could account for a dilution of dark matter,” he said.
In the beginning, when temperatures soared past billions of degrees in a relatively small volume of space, dark matter particles could run into each other and annihilate upon contact, transferring their energy into standard constituents of matter-particles like electrons and quarks. But as the universe continued to expand and cool, dark matter particles encountered one another far less often, and the annihilation rate couldn’t keep up with the expansion rate.
“At this point, the abundance of dark matter is now baked in the cake,” said Davoudiasl. “Remember, dark matter interacts very weakly. So, a significant annihilation rate cannot persist at lower temperatures. Self-annihilation of dark matter becomes inefficient quite early, and the amount of dark matter particles is frozen.”
However, the weaker the dark matter interactions, that is, the less efficient the annihilation, the higher the final abundance of dark matter particles would be. As experiments place ever more stringent constraints on the strength of dark matter interactions, there are some current theories that end up overestimating the quantity of dark matter in the universe. To bring theory into alignment with observations, Davoudiasl and his colleagues suggest that another inflationary period took place, powered by interactions in a “hidden sector” of physics. This second, milder, period of inflation, characterized by a rapid increase in volume, would dilute primordial particle abundances, potentially leaving the universe with the density of dark matter we observe today.
“It’s definitely not the standard cosmology, but you have to accept that the universe may not be governed by things in the standard way that we thought,” he said. “But we didn’t need to construct something complicated. We show how a simple model can achieve this short amount of inflation in the early universe and account for the amount of dark matter we believe is out there.”
Proving the theory is another thing entirely. Davoudiasl said there may be a way to look for at least the very feeblest of interactions between the hidden sector and ordinary matter.
“If this secondary inflationary period happened, it could be characterized by energies within the reach of experiments at accelerators such as the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider,” he said. Only time will tell if signs of a hidden sector show up in collisions within these colliders, or in other experimental facilities.February 11, 2016 at 2:57 pm #45451
By Adrian ChoFeb. 11, 2016 , 10:30 AM
Long ago, deep in space, two massive black holesthe ultrastrong gravitational fields left behind by gigantic stars that collapsed to infinitesimal pointsslowly drew together. The stellar ghosts spiraled ever closer, until, about 1.3 billion years ago, they whirled about each other at half the speed of light and finally merged. The collision sent a shudder through the universe: ripples in the fabric of space and time called gravitational waves. Five months ago, they washed past Earth. And, for the first time, physicists detected the waves, fulfilling a 4-decade quest and opening new eyes on the heavens.
The discovery marks a triumph for the 1000 physicists with the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of gigantic instruments in Hanford, Washington, and Livingston, Louisiana. Rumors of the detection had circulated for months. Today, at a press conference in Washington, D.C., the LIGO team made it official. We did it! says David Reitze, a physicist and LIGO executive director at the California Institute of Technology (Caltech) in Pasadena. All the rumors swirling around out there got most of it right.
Albert Einstein predicted the existence of gravitational waves 100 years ago, but directly detecting them required mind-boggling technological prowess and a history of hunting. (See a timeline below of the history of the search for gravitational waves.) LIGO researchers sensed a wave that stretched space by one part in 1021, making the entire Earth expand and contract by 1/100,000 of a nanometer, about the width of an atomic nucleus. The observation tests Einsteins theory of gravity, the general theory of relativity, with unprecedented rigor and provides proof positive that black holes exist. It will win a Nobel Prize, says Marc Kamionkowski, a theorist at Johns Hopkins University in Baltimore, Maryland.
LIGO watches for a minuscule stretching of space with what amounts to ultraprecise rulers: two L-shaped contraptions called interferometers with arms 4 kilometers long. Mirrors at the ends of each arm form a long resonant cavity, in which laser light of a precise wavelength bounces back and forth, resonating just as sound of a specific pitch rings in an organ pipe. Where the arms meet, the two beams can overlap. If they have traveled different distances along the arms, their waves will wind up out of step and interfere with each other. That will cause some of the light to warble out through an exit called a dark port in synchrony with undulations of the wave.
From the interference, researchers can compare the relative lengths of the two arms to within 1/10,000 the width of a protonenough sensitivity to see a passing gravitational wave as it stretches the arms by different amounts. To spot such tiny displacements, however, scientists must damp out vibrations such as the rumble of seismic waves, the thrum of traffic, and the crashing of waves on distant coastlines.
On 14 September 2015, at 9:50:45 universal time4:50 a.m. in Louisiana and 2:50 a.m. in WashingtonLIGOs automated systems detected just such a signal. The oscillation emerged at a frequency of 35 cycles per second, or Hertz, and sped up to 250 Hz before disappearing 0.25 seconds later. The increasing frequency, or chirp, jibes with two massive bodies spiraling into each other. The 0.007-second delay between the signals in Louisiana and Washington is the right timing for a light-speed wave zipping across both detectors.
The signal exceeds the five-sigma standard of statistical significance that physicists use to claim a discovery, LIGO researchers report in a paper scheduled to be published in Physical Review Letters to coincide with the press conference. Its so strong it can be seen in the raw data, says Gabriela González, a physicist at Louisiana State University, Baton Rouge, and spokesperson for the LIGO scientific collaboration. If you filter the data, the signal is obvious to the eye, she says.
Comparison with computer simulations reveals that the wave came from two objects 29 and 36 times as massive as the sun spiraling to within 210 kilometers of each other before merging. Only a black holewhich is made of pure gravitational energy and gets its mass through Einsteins famous equation E=mc2can pack so much mass into so little space, says Bruce Allen, a LIGO member at the Max Planck Institute for Gravitational Physics in Hanover, Germany. The observation provides the first evidence for black holes that does not depend on watching hot gas or stars swirl around them at far greater distances. Before, you could argue in principle whether or not black holes exist, Allen says. Now you cant.
The collision produced an astounding, invisible explosion. Modeling shows that the final black hole totals 62 solar masses3 solar masses less than the sum of the initial black holes. The missing mass vanished in gravitational radiationa conversion of mass to energy that makes an atomic bomb look like a spark. For a tenth of a second [the collision] shines brighter than all of the stars in all the galaxies, Allen says. But only in gravitational waves.
Other stellar explosions called gamma-ray bursts can also briefly outshine the stars, but the explosive black-hole merger sets a mind-bending record, says Kip Thorne, a gravitational theorist at Caltech who played a leading role in LIGOs development. It is by far the most powerful explosion humans have ever detected except for the big bang, he says.
For 5 months, LIGO physicists struggled to keep a lid on their pupating discovery. Ordinarily, most team members would not have known whether the signal was real. LIGO regularly salts its data readings with secret false signals called blind injections to test the equipment and keep researchers on their toes. But on 14 September 2015, that blind injection system was not running. Physicists had only recently completed a 5-year, $205 million upgrade of the machines, and several systemsincluding the injection systemwere still offline as the team wound up a preliminary engineering run. As a result, the whole collaboration knew that the observation was likely real. I was convinced that day, González says.
Still, LIGO physicists had to rule out every alternative, including the possibility that the reading was a malicious hoax. We spent about a month looking at the ways that somebody could spoof a signal, Reitze says, before deciding it was impossible. For González, making the checks was a heavy responsibility, she says. This was the first detection of gravitational waves, so there was no room for a mistake.
Proving that gravitational waves exist may not be LIGOs most important legacy, as there has been compelling indirect evidence for them. In 1974, U.S. astronomers Russell Hulse and Joseph Taylor discovered a pair of radio-emitting neutron stars called pulsars orbiting each other. By timing the pulsars, Taylor and colleague Joel Weisberg demonstrated that they are very slowly spiraling toward each otheras they should if theyre radiating gravitational waves.
It is the prospect of the science that might be done with gravitational waves that really excites physicists. For example, says Kamionkowski, the theorist at Johns Hopkins, the first LIGO result shows the power of such radiation to reveal unseen astrophysical objects like the two ill-fated black holes. This opens a new window on this vast population of stellar remnants that we know are out there but of which we have seen only a tiny fraction, he says.
The observation also paves the way for testing general relativity as never before, Kamionkowski says. Until now, physicists have studied gravity only in conditions where the force is relatively weak. By studying gravitational waves, they can now explore extreme conditions in which the energy in an objects gravitational field accounts for most or all of its massthe realm of strong gravity so far explored by theorists alone.
With the black hole merger, general relativity has passed the first such test, says Rainer Weiss, a physicist at the Massachusetts Institute of Technology (MIT) in Cambridge, who came up with the original idea for LIGO. The things you calculate from Einsteins theory look exactly like the signal, he says. To me, thats a miracle.
The detection of gravitational waves marks the culmination of a decades-long quest that began in 1972, when Weiss wrote a paper outlining the basic design of LIGO. In 1979, the National Science Foundation funded research and development work at both MIT and Caltech, and LIGO construction began in 1994. The $272 million instruments started taking data in 2001, although it was not until the upgrade that physicists expected a signal.
If LIGOs discovery merits a Nobel Prize, who should receive it? Scientists say Weiss
is a shoo-in, but he demurs. I dont like to think of it, he says. If it wins a Nobel Prize, it shouldnt be for the detection of gravitational waves. Hulse and Taylor did that. Many researchers say other worthy recipients would include Ronald Drever, the first director of the project at Caltech who made key contributions to LIGOs design, and Thorne, the Caltech theorist who championed the project. Thorne also objects. The people who really deserve the credit are the experimenters who pulled this off, starting with Rai and Ron, he says.
Meanwhile, other detections may come quickly. LIGO researchers are still analyzing data from their first observing run with their upgraded detectors, which ended 12 January, and they plan to start taking data again in July. A team in Italy hopes to turn on its rebuilt VIRGO detectoran interferometer with 3-kilometer armslater this year. Physicists eagerly await the next wave.
From prediction to reality: a history of the search for gravitational waves
1915 – Albert Einstein publishes general theory of relativity, explains gravity as the warping of spacetime by mass or energy
1916 – Einstein predicts massive objects whirling in certain ways will cause spacetime ripplesgravitational waves
1936 – Einstein has second thoughts and argues in a manuscript that the waves don’t existuntil reviewer points out a mistake
1962 – Russian physicists M. E. Gertsenshtein and V. I. Pustovoit publish paper sketch optical method for detecting gravitational
wavesto no notice
1969 – Physicist Joseph Weber claims gravitational wave detection using massive aluminum cylindersreplication efforts fail
1972 – Rainer Weiss of the Massachusetts Institute of Technology (MIT) in Cambridge independently proposes optical method for detecting waves
1974 – Astronomers discover pulsar orbiting a neutron star that appears to be slowing down due to gravitational radiationwork that later earns them a Nobel Prize
1979 – National Science Foundation (NSF) funds California Institute of Technology in Pasadena and MIT to develop design for LIGO
1990 – NSF agrees to fund $250 million LIGO experiment
1992 – Sites in Washington and Louisiana selected for LIGO facilities; construction starts 2 years later
1995 – Construction starts on GEO600 gravitational wave detector in Germany, which partners with LIGO and starts taking data in 2002
1996 – Construction starts on VIRGO gravitational wave detector in Italy, which starts taking data in 2007
20022010 – Runs of initial LIGOno detection of gravitational waves
2007 – LIGO and VIRGO teams agree to share data, forming a single global network of gravitational wave detectors
20102015 – $205 million upgrade of LIGO detectors
2015 – Advanced LIGO begins initial detection runs in September
2016 – On 11 February, NSF and LIGO team announce successful detection of gravitational wavesFebruary 20, 2016 at 12:04 am #45453February 21, 2016 at 2:51 am #45455
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