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Keyword: darkforce

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  • Missing Light Crisis: 'Something is Amiss in the Universe'

    07/10/2014 6:57:55 AM PDT · by shove_it · 40 replies
    IBTimes ^ | 10 Jul 2014 | Hannah Osborne
    There is a "missing light crisis" taking place in the universe with a huge deficit on what there should be and what there actually is, astronomers have said. In a statement, experts from the Carnegie Institution for Science said "something is amiss in the universe" with 80% of the light missing. Lead author of the study Juna Kollmeier said: "It's as if you're in a big, brightly-lit room, but you look around and see only a few 40-watt lightbulbs. Where is all that light coming from? It's missing from our census." Published in Astrophysical Journal Letters, scientists found that the...
  • Astronomy Picture of the Day -- Gamma Rays from Galactic Center Dark Matter?

    03/10/2014 5:36:20 PM PDT · by SunkenCiv · 9 replies
    NASA ^ | March 10, 2014 | (see photo credit)
    Explanation: What is creating the gamma rays at the center of our Galaxy? Excitement is building that one answer is elusive dark matter. Over the past few years the orbiting Fermi Gamma-ray Space Telescope has been imaging our Galaxy's center in gamma-rays. Repeated detailed analyses indicate that the region surrounding the Galactic center seems too bright to be accounted by known gamma-ray sources. A raw image of the Galactic Center region in gamma-rays is shown above on the left, while the image on the right has all known sources subtracted -- leaving an unexpected excess. An exciting hypothetical model that...
  • Astronomy Picture of the Day -- Heavy Black Hole Jets in 4U1630-47

    11/20/2013 3:05:13 AM PST · by SunkenCiv · 8 replies
    NASA ^ | November 20, 2013 | (see photo credit)
    Explanation: What are black hole jets made of? Many black holes in stellar systems are surely surrounded by disks of gas and plasma gravitationally pulled from a close binary star companion. Some of this material, after approaching the black hole, ends up being expelled from the star system in powerful jets emanating from the poles of the spinning black hole. Recent evidence indicates that these jets are composed not only electrons and protons, but also the nuclei of heavy elements such as iron and nickel. The discovery was made in system 4U1630-47 using CSIRO’s Compact Array of radio telescopes in...
  • Scientists proud of dark matter study that turns up nothing

    11/12/2013 6:08:01 PM PST · by Tailgunner Joe · 28 replies
    upi.com ^ | October 31, 2013 | Caroline Lee
    Scientists at the Homestake Gold Mine in South Dakota running the biggest, most sensitive dark matter detector yet released its first round of results yesterday -- and they found nothing. The Large Underground Xenon dark matter experiment, or LUX, consists of a vat of 368 kilograms of liquid xenon to minus 110 degrees Celsius, surrounded by a tank of water. LUX sits 4,850 feet underground at the old mine, shielded from cosmic rays. An international team of researchers watched for three months to see if any WIMPS -- weakly interacting massive particles -- would pass through the rock and reveal...
  • 'We may be able to watch dark energy turn on': U-M involved in unprecedented sky survey

    09/03/2013 4:20:57 PM PDT · by LibWhacker · 5 replies
    U-Mich ^ | 9/3/13 | Nicole Casal Moore
    ANN ARBOR—Moonless nights outside the Cerro Tololo astronomical observatory in Chile are so dark that when you look down, you can't see your feet. "You can't see your hands," said David Gerdes, physics professor at the University of Michigan. "But you can hold them up to the sky and see a hand-shaped hole with no stars in it. It's really incredible." From this site in the Andes over the next five years, an international team will map one-eighth of the sky in unprecedented detail—aiming to make a time lapse of the past 8 billion years of a slice of the...
  • Physicists suggest possible existence of other kinds of dark matter

    05/26/2013 4:08:21 PM PDT · by neverdem · 51 replies
    Phys.org ^ | May 24, 2013 | Bob Yirka
    Credit: Phys. Rev. Lett. 110, 211302 (2013) (Phys.org) —A team of Harvard University physicists has proposed the possible existence of a type of dark matter not described by current physics models. In their paper published in the journal Physical Review Letters, the team suggests it's possible that not all dark matter is cold and collision-less. In the visible universe, galaxies form into a disk shape—the Milky Way is a good example. All of its members align roughly along a single plane, this due to the forces of gravity and spin. Objects form into masses which, over time, spread out...
  • Theorists weigh in on where to hunt dark matter

    05/26/2013 6:21:28 PM PDT · by neverdem · 22 replies
    Phys.org ^ | May 22, 2013 | Lori Ann White
    Enlarge Left panel: Air molecules whiz around at a variety of speeds, and some are very fast. When they collide with both heavy and light elements - for example, xenon (purple) and silicon (orange) - these fast moving particles have enough momentum to affect both nuclei. Right panel: Dark matter particles are moving more slowly and are less able to affect the heavy xenon nucleus. As a result, detectors made from lighter materials like silicon may prove to be more effective at picking up signals of dark matter. Credit: Greg Stewart/SLAC National Accelerator Laboratory (Phys.org) —Now that it looks...
  • Earth's mantle helps hunt for fifth force of nature

    02/24/2013 4:51:43 PM PST · by BenLurkin · 10 replies
    newscientist.com ^ | 19:00 21 February 2013 by | Jacob Aron
    Try using the entire Earth to hunt for a new fundamental force of nature. So say Larry Hunter of Amherst College in Massachusetts, and colleagues. They have created a map of the spins of electrons deep within the Earth's mantle, which could be used to reveal the as-yet-unseen force as well as the strange particles – known as "unparticles" – that might carry it. We currently know of four fundamental forces: gravity, electromagnetism and the strong and weak nuclear forces. The hypothetical fifth force can be thought of as a version of magnetism that does not weaken as quickly with...
  • Astroboffins map GIANT MASS of dark matter

    10/18/2012 9:31:59 AM PDT · by Ernest_at_the_Beach · 10 replies
    The Register ^ | 17th October 2012 15:15 GMT | Brid-Aine Parnell
    3D image shows ginormous filament of Big Bang batter Dark matter can't really be "seen" as such, it can only be detected by looking at the gravitational effects it has on the space around it. But by collating images from the Hubble Space telescope, the researchers now have a picture of dark matter (shown in blue above) extending 60 million light-years away from one of the most massive galaxy clusters astrophysicists know about – MACS J0717. Big Bang theories predict that when the universe was first created, dense matter condensed into a web of tangled dark matter filaments throughout the...
  • Universe has more hydrogen than we thought (Undark’ matter hidden in plain view)

    06/02/2012 11:45:49 AM PDT · by Ernest_at_the_Beach · 26 replies
    The Register ^ | 31st May 2012 23:59 GMT | Richard Chirgwin
    A re-analysis of radio telescope observations from three countries has yielded a surprising result: nearby galaxies harbour one-third more hydrogen than had previously been estimated. While nothing like enough matter to solve physics’ “dark matter” problem, the work by CSIRO astronomer Dr Robert Braun (chief scientist at the agency’s Astronomy and Space Science division in Sydney) also helps explain why the rate of star formation has slowed down. While there’s more hydrogen than astronomers had thought, its distribution makes star formation more difficult. Andromeda – the galaxy headed for a catastrophic collision with our own in about four billion years...
  • Results From South Pole Support Einstein’s Cosmological Constant

    04/04/2012 1:05:17 AM PDT · by lbryce · 5 replies
    R & D ^ | April 2,2012 | Staff
    Analysis of data from the National Science Foundation-(NSF) funded 10-m South Pole Telescope (SPT) in Antarctica provides new support for the most widely accepted explanation of dark energy, the source of the mysterious force that is responsible for the accelerating expansion of the universe. The results begin to hone in on the tiny mass of the neutrinos, the most abundant particles in the universe, which until recently were thought to be without mass. The SPT data strongly support Albert Einstein's cosmological constant—the leading model for dark energy—even though researchers base the analysis on only a fraction of the SPT data...
  • Survey gets a grip on dark energy (the BOSS project - Baryon Oscillation Spectroscopic Survey)

    03/31/2012 3:07:36 PM PDT · by NormsRevenge · 20 replies
    BBC News ^ | 3/30/12 | Jonathan Amos
    Astronomers have measured the precise distance to over a quarter of a million galaxies to gain new insights into a key period in cosmic history. The 3D map of the sky allows scientists to probe the time six billion years ago when dark energy became the dominant influence on the Universe's expansion. No-one knows the true nature of this repulsive force, but the exquisite data in the international BOSS survey will help test various theories. The analysis appears in six papers. These have all been posted on the arXiv preprint server. "This is an incredibly exciting time to be working...
  • Dwarf galaxies suggest dark matter theory may be wrong

    09/16/2011 3:33:06 PM PDT · by decimon · 56 replies
    BBC ^ | September 16, 2011 | Leila Battison
    Scientists' predictions about the mysterious dark matter purported to make up most of the mass of the Universe may have to be revised.Research on dwarf galaxies suggests they cannot form in the way they do if dark matter exists in the form that the most common model requires it to. That may mean that the Large Hadron Collider will not be able to spot it. Leading cosmologist Carlos Frenk spoke of the "disturbing" developments at the British Science Festival in Bradford. The current theory holds that around 4% of the Universe is made up of normal matter - the stuff...
  • New method 'confirms dark energy'

    05/19/2011 3:02:45 PM PDT · by decimon · 30 replies
    BBC ^ | May 19, 2011 | Paul Rincon
    First results from a major astronomical survey have confirmed the existence of mysterious dark energy using a cutting-edge technique. Dark energy makes up some 74% of the Universe and its existence explains why the Universe appears to be expanding at an accelerating rate. The finding was based on studies of more than 200,000 galaxies. Scientists used two separate kinds of observation to provide an independent check on previous dark energy results. Two papers by an international team of researchers have been accepted for publication in the Monthly Notices of the Royal Astronomical Society journal. One type of observation used by...
  • Is an Adjacent Universe Causing the Dark Flow of Hundred of Millions of Stars at the Edge of the...

    04/16/2011 5:50:42 PM PDT · by LibWhacker · 30 replies
    Daily Galaxy ^ | 4/15/11
    Is an Adjacent Universe Causing the Dark Flow of Hundred of Millions of Stars at the Edge of the Observable Universe? Or, Might It Be Something ElseBack in the Middle Ages, maps showed terrifying images of sea dragons at the boundaries of the known world. Today, scientists have observed strange new motion at the very limits of the known universe -- kind of where you'd expect to find new things, but they still didn't expect this. A huge swathe of galactic clusters seem to be heading to a cosmic hotspot and nobody knows why. The unexplained motion has hundreds of...
  • Dark energy and flat Universe exposed by simple method

    11/24/2010 12:52:49 PM PST · by NormsRevenge · 39 replies
    BBC News ^ | 11/24/10 | BBC
    Researchers have developed a simple technique that adds evidence to the theory that the Universe is flat. Moreover, the method - developed by revisiting a 30-year-old idea - confirms that "dark energy" makes up nearly three-quarters of the Universe. The research, published in Nature, uses existing data and relies on fewer assumptions than current approaches. Author Christian Marinoni says the idea turns estimating the Universe's shape into "primary school" geometry. While the idea of the Earth being flat preoccupied explorers centuries ago, the question of whether the Universe itself is flat remains a debatable topic. The degree to which the...
  • Physicists Discover "Violation of a Fundamental Symmetry of the Universe"

    11/04/2010 12:31:54 PM PDT · by lbryce · 110 replies · 1+ views
    i09.com ^ | November 3, 2010 | Staff
    Today physicists announced that they may have found the key to explaining dark matter in the universe. It all has to do with the potential discovery of a "sterile neutrino." According to a release about the new study: Neutrinos are neutral elementary particles born in the radioactive decay of other particles. The known "flavors" of neutrinos are the neutral counterparts of electrons and their heavier cousins, muons and taus. Regardless of a neutrino's original flavor, the particles constantly flip from one type to another in a phenomenon called "neutrino flavor oscillation." An electron neutrino might become a muon neutrino, and...
  • Dark energy may not exist in space, scientists claim

    06/22/2010 3:48:13 PM PDT · by SunkenCiv · 37 replies · 1+ views
    Telegraph ^ | Tuesday, June 15, 2010 | Heidi Blake
    British scientists have claimed that the method used to calculate the make-up of the universe may be wrong. The universe as we know it -- formed of recognisable components such as planets, stars, asteroids and gas -- accounts for just four per cent of the cosmos, according to the decades old Standard Model. The rest is thought to be made up of mysterious dark matter and dark energy. This permeates space and powers the expansion of the universe. But physicists at Durham University now claim the calculations on which the Standard Model is based could be fatally flawed. This raises...
  • Key to the universe found on the Iron Range? [WIMP scatters detected?]

    12/18/2009 6:56:27 PM PST · by SunkenCiv · 18 replies · 843+ views
    Star Tribune ^ | Friday, December 18, 2009 | Bob Von Sternberg
    Scientists announced Thursday that they believe they have detected evidence of dark matter in data collected at an underground physics lab in Soudan... According to the Department of Energy's Fermilab, which is conducting the search for dark matter at the Soudan lab, "judging by the way galaxies rotate, scientists have known for 70 years that the matter we can see does not provide enough gravitational pull to hold the galaxies together. There must exist some form of matter that does not emit or reflect light." In the announcement, the lab said the Cryogenic Dark Matter Search experiment has "detected...
  • Tweak Gravity: What If There Is No Dark Matter?

    11/08/2009 6:07:35 PM PST · by SunkenCiv · 30 replies · 946+ views
    Scientific American ^ | Thursday, November 5, 2009 | John Matson
    What if the discrepancy arises from a flaw in our theory of gravity rather than from some provider of mass that we cannot see? In the 1980s physicist Mordehai Milgrom of the Weizmann Institute of Science in Rehovot, Israel, proposed a modification to Newtonian dynamics that would explain many of the observational discrepancies without requiring significant mass to be hidden away in dark matter. But it fell short of describing all celestial objects, and to incorporate the full span of gravitational interactions, a modification to Albert Einstein's theory of general relativity is needed. A review article in the November 6...
  • The day the universe froze; New dark energy model includes cosmological phase transition

    05/08/2009 1:40:50 PM PDT · by Mike Fieschko · 19 replies · 478+ views
    euarekalert.org ^ | May 8, 2009 | David F. Salisbury [?]
    Imagine a time when the entire universe froze. According to a new model for dark energy, that is essentially what happened about 11.5 billion years ago, when the universe was a quarter of the size it is today. The model, published online May 6 in the journal Physical Review D, was developed by Research Associate Sourish Dutta and Professor of Physics Robert Scherrer at Vanderbilt University, working with Professor of Physics Stephen Hsu and graduate student David Reeb at the University of Oregon. A cosmological phase transition -- similar to freezing -- is one of the distinctive aspects of this...
  • Study plunges standard theory of cosmology into crisis

    05/05/2009 7:17:29 AM PDT · by decimon · 32 replies · 805+ views
    As modern cosmologists rely more and more on the ominous "dark matter" to explain otherwise inexplicable observations, much effort has gone into the detection of this mysterious substance in the last two decades, yet no direct proof could be found that it actually exists. Even if it does exist, dark matter would be unable to reconcile all the current discrepancies between actual measurements and predictions based on theoretical models. Hence the number of physicists questioning the existence of dark matter has been increasing for some time now. Competing theories of gravitation have already been developed which are independent of this...
  • Astronomers Aim to Grasp Mysterious Dark Matter (In search of WIMPs)

    12/29/2008 2:46:01 PM PST · by NormsRevenge · 6 replies · 484+ views
    Space.com on Yahoo ^ | 12/29/08 | Clara Moskowitz
    For the past quarter century, dark matter has been a mystery we've just had to live with. But the time may be getting close when science can finally unveil what this befuddling stuff is that makes up most of the matter in the universe. Dark matter can't be seen. Nobody even knows what it is. But it must be there, because without it galaxies would fly apart. Upcoming experiments on Earth such as the Large Hadron Collider (LHC) particle accelerator in Switzerland, and a new spacecraft called Gaia set to launch in 2011, could be the key to closing the...
  • Mysterious force's long presence

    11/16/2006 7:22:01 PM PST · by Jedi Master Pikachu · 26 replies · 482+ views
    BBC ^ | November 16, 2006
    Dark energy - the mysterious force that is speeding up the expansion of the Universe - has been a part of space for at least nine billion years. That is the conclusion of astronomers who presented results from a three-year study using the Hubble Space Telescope. The finding may rule out some competing theories that predict the strength of dark energy changes over time. Dark energy makes up about 70% of the Universe; the rest is dark matter (25%) and normal matter (5%). "It appears this dark energy was already boosting the expansion of the Universe as much as...
  • Mysterious New 'Dark Flow' Discovered in Space

    09/23/2008 4:46:02 PM PDT · by NormsRevenge · 37 replies · 252+ views
    Space.com on Yahoo ^ | 9/23/08 | Clara Moskowitz
    As if the mysteries of dark matter and dark energy weren't vexing enough, another baffling cosmic puzzle has been discovered. Patches of matter in the universe seem to be moving at very high speeds and in a uniform direction that can't be explained by any of the known gravitational forces in the observable universe. Astronomers are calling the phenomenon "dark flow." The stuff that's pulling this matter must be outside the observable universe, researchers conclude. When scientists talk about the observable universe, they don't just mean as far out as the eye, or even the most powerful telescope, can see....
  • Tsunami invisibility cloak, dark energy v. the void, sorting nanotubes with light, and more

    09/26/2008 4:30:39 AM PDT · by decimon · 12 replies · 490+ views
    American Physical Society ^ | Sep 26, 2008 | Unknown
    Tsunami invisibility cloak, dark energy v. the void, sorting nanotubes with light, and moreNews from the American Physical SocietyTsunami Invisibility Cloak M. Farhat, S. Enoch, S. Guenneau and A.B. Movchan Physical Review Letters (forthcoming) Rather than building stronger ocean-based structures to withstand tsunamis, it might be easier to simply make the structures disappear. A collaboration of physicists from the Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Universite in France and the University of Liverpool in England have conducted laboratory experiments showing that it's possible to make type of dike that acts as an invisibility cloak that hides off-shore...
  • Do We Live in a Giant Cosmic Bubble?

    09/30/2008 3:23:48 PM PDT · by decimon · 35 replies · 739+ views
    SPACE.com ^ | Sep 30, 2008 | Clara Moskowitz
    If the notion of dark energy sounds improbable, get ready for an even more outlandish suggestion. Earth may be trapped in an abnormal bubble of space-time that is particularly void of matter. Scientists say this condition could account for the apparent acceleration of the universe's expansion, for which dark energy currently is the leading explanation.
  • Mysterious Dark Matter Might Actually Glow

    11/07/2008 3:21:52 PM PST · by SunkenCiv · 9 replies · 594+ views
    SPACE.com ^ | Thursday, November 6, 2008 | Staff
    Nobody knows what dark matter is, but scientists may now have a clue where to look for it. The strange stuff makes up about 85 percent of the heft of the universe. It's invisible, but researchers know it's there because there is not enough regular matter -- stars and planets and gas and dust -- to hold galaxies and galaxy clusters together. Some other unseen material, dubbed dark matter, must be gluing things together... A new computer simulation of the evolution of a galaxy like our Milky Way suggests it might be possible to observe high-energy gamma-rays given off by...
  • Galaxy Surprise Sheds Light on Dark Matter

    11/07/2008 4:48:38 PM PST · by SunkenCiv · 16 replies · 666+ views
    Space.com ^ | August 27, 2008 | Clara Moskowitz
    A study of small galaxies circling around the Milky Way found that while they range dramatically in brightness, they all surprisingly pack about the same mass. The work suggests there is a minimum size for galaxies, and it could shed light on mysterious dark matter. Spinning around the Milky Way are at least 23 pint-sized galaxies, each shining with the light of anywhere from a thousand to a billion suns. Though each of these galaxies is very dim compared to large galaxies like our own, they span a large range in brightness. Astronomers led by Louis Strigari of the University...
  • Unknown "Structures" Tugging at Universe, Study Says [ Dark Flow ]

    11/07/2008 3:29:16 PM PST · by SunkenCiv · 73 replies · 1,866+ views
    National Geographic News ^ | November 5, 2008 | John Roach
    Everything in the known universe is said to be racing toward the massive clumps of matter at more than 2 million miles (3.2 million kilometers) an hour -- a movement the researchers have dubbed dark flow. The presence of the extra-universal matter suggests that our universe is part of something bigger -- a multiverse -- and that whatever is out there is very different from the universe we know, according to study leader Alexander Kashlinsky, an astrophysicist at NASA's Goddard Space Flight Center in Maryland... Dark flow was named in a nod to dark energy and dark matter -- two...
  • Mysterious New 'Dark Flow' Discovered in Space

    09/25/2008 8:58:58 AM PDT · by nobama08 · 18 replies · 755+ views
    foxnews.com ^ | Thursday, September 25, 2008 | Clara Moskowitz
    As if the mysteries of dark matter and dark energy weren't vexing enough, another baffling cosmic puzzle has been discovered. Patches of matter in the universe seem to be moving at very high speeds and in a uniform direction that can't be explained by any of the known gravitational forces in the observable universe. Astronomers are calling the phenomenon "dark flow." The stuff that's pulling this matter must be outside the observable universe, researchers conclude.
  • Monster galactic cluster seen in deep Universe: European agency

    08/25/2008 3:56:31 PM PDT · by NormsRevenge · 15 replies · 307+ views
    AFP on Yahoo ^ | 8/25/08 | AFP
    PARIS (AFP) – An orbiting observatory has spotted a massive cluster of galaxies in deep space that can only be explained by the exotic phenomenon known as dark energy, the European Space Agency (ESA) said on Monday. Spotted in a scan by ESA's orbiting X-ray telescope XMM-Newton, the cluster's mass is about 1,000 times that of our own galaxy, the Milky Way, it said. The huge cluster, known by its catalogue number of 2XMM J083026+524133, lies 7.7 billion light years from Earth and helps confirm the existence of dark energy, the agency said. Under this hypothesis, most of the Universe...
  • Physicists Renew Claim, in New Experiment, of Detecting Dark Matter Particles

    04/17/2008 11:38:51 PM PDT · by neverdem · 9 replies · 118+ views
    NY Times ^ | April 17, 2008 | DENNIS OVERBYE
    A team of Italian and Chinese physicists on Wednesday renewed a controversial claim that they had detected the mysterious dark matter particles that astronomers say swaddle the galaxies in halos and direct the evolution of the universe. The team, called Dama, from “DArk MAtter,” and led by Rita Bernabei of the University of Rome, has maintained since 2000 that a yearly modulation in the rate of flashes in a detector nearly a mile underneath the Gran Sasso mountain in Italy is the result of the Earth’s passage through a “wind” of dark matter particles as it goes around the Sun....
  • "Dark Energy" Dominates The Universe

    01/03/2003 6:35:40 AM PST · by forsnax5 · 46 replies · 364+ views
    Dartmouth College ^ | January 2, 2003 | Brian Chaboyer, Lawrence Krauss
    DARK ENERGY DOMINATES THE UNIVERSE HANOVER, NH - A Dartmouth researcher is building a case for a "dark energy"-dominated universe. Dark energy, the mysterious energy with unusual anti-gravitational properties, has been the subject of great debate among cosmologists. Brian Chaboyer, Assistant Professor of Physics and Astronomy at Dartmouth, with his collaborator Lawrence Krauss, Professor of Physics and Astronomy at Case Western Reserve University, have reported their finding in the January 3, 2003, issue of Science. Combining their calculations of the ages of the oldest stars with measurements of the expansion rate and geometry of the universe lead them to conclude...
  • 'Shot in the Dark' Star Explosion Stuns Astronomers

    12/18/2007 10:07:29 AM PST · by crazyshrink · 39 replies · 123+ views
    EurekAlert ^ | 12/18/07 | Astronomers
    When a shot is fired, one expects to see a person with a gun. In the same way, whenever a giant star explodes, astronomers expect to see a galaxy of stars surrounding the site of the blast. This comes right out of basic astronomy, since almost all stars in our universe belong to galaxies. Image right: The robotic Palomar 60-inch telescope imaged the afterglow of GRB 070125 on January 26, 2007. Right: An image taken of the same field on February 16 with the 10-meter Keck I telescope reveals no trace of an afterglow, or a host galaxy. The white...
  • Dark matter behaves in an unexpected way

    08/28/2007 11:51:06 AM PDT · by SunkenCiv · 36 replies · 363+ views
    arstechnica ^ | August 17, 2007 | Chris Lee
    Radiation was used to pinpoint the normal matter, while the observation of gravitational lensing was used locate dark matter. Gravitational lensing allows matter to be oberved, even when it does not emit or absorb light, by examining the movement of galaxies as our line of sight passes through the area of interest. Massive objects will distort the image and cause it to move in unexpected directions. Because the normal matter could interact through electromagnetic radiation, it was found to have slowed violently during the collision while the dark matter sailed on through... In the meantime, other astronomers began using gravitational...
  • Is dark energy lurking in hidden spatial dimensions?

    07/16/2007 12:26:58 PM PDT · by SunkenCiv · 16 replies · 565+ views
    New Scientist ^ | Monday, July 16, 2007 | Stephen Battersby
    The mysterious cosmic presence called dark energy, which is accelerating the expansion of the universe, might be lurking in hidden dimensions of space. The idea would explain how these dimensions remain stable - a big problem for the unified scheme of physics called string theory... quantum vibrations in the vacuum of space (called vacuum energy or the cosmological constant) that could produce repulsive gravity... should either possess a ridiculously high energy density - 122 orders of magnitude larger than are observed - or cancel out to exactly zero. To make them almost-but-not-quite cancel, in agreement with astronomical observations, means fudging...
  • First Dark Matter, Then Dark Energy, Now a Dark Force?

    01/09/2007 12:12:54 AM PST · by SunkenCiv · 7 replies · 376+ views
    Scientific American 'blogs ^ | January 8, 2007 | George Musser
    The poster child for dark matter, which got a lot of attention last summer, is the Bullet Cluster of galaxies... What's less well known is that the smaller of the two colliding clusters is a cluster in a hurry, zipping along at 4700 kilometers per second... Farrar... and her graduate student Rachael Rosen estimated a few months ago that gravity should have accelerated the cluster to maybe 3000 km/s. Even if the cluster had an improbable combination of elongated shape, high initial velocity, and special viewing geometry, it should move no faster than 3400 km/s. Farrar concluded that some new...