Free Republic

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...

I came across a news item in the USA Today website, dated August 18, that got my attention. It concerns "Dark Energy", the mysterious force that seems to be speeding up the expansion of the universe, that no one can find or explain. Two scientists say is doesn't exist now because of a "mathematical solution they have produced, that suggests it is a natural result of the Big Bang. Part of the article is reproduced here. "What's the answer? It doesn't exist, suggest mathematicians Blake Temple and Joel Smoller, in a study released Monday by the Proceedings of the National...

Gamma-ray spike in Fermi telescope data hikes anticipation.The jury is still out on whether Fermi has spied dark matter.NASA/DOE/International LAT Team The murky hunt for dark matter has just got a little bit brighter. New gamma-ray results from the FERMI telescope fit with previous tantalizing hints of a detection of the mysterious stuff.Last year, a series of independent experiments caused a stir because they seemed to have detected signals of dark matter, which is believed to make up 85% of the universe's matter."There's been tremendous excitement about cosmic ray signals that have dark matter as one possible explanation," says Neal...

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...

New data from two experiments -- one in space, one on a balloon floating above Antarctica -- hint at a tantalizing detection of dark matter, the mysterious stuff comprising 85% of the universe's matter. The evidence is a reported excess of high-energy electrons and their antimatter counterparts, positrons, which could be created as dark matter particles annihilate or decay. The signal from Fermi, the orbiting gamma-ray telescope, is subtle, whereas that claimed by the balloon-borne Advanced Thin Ionization Calorimeter (ATIC) is much more pronounced. The differences are puzzling, but the findings -- according to some -- could herald the birth...

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...

Enlarge ImageKilljoy. NASA's orbiting Fermi Gamma-ray Space Telescope has not reproduced a previously claimed signature of dark matter. Credit: NASA and General Dynamics Last November, data from a balloon-borne particle detector circling the South Pole revealed a dramatic excess of high-energy particles from space--a possible sign of dark matter, the mysterious substance whose gravity seems to hold our galaxy together. But satellite data reported today stick a pin in that claim. Researchers working with NASA's orbiting Fermi Gamma-ray Space Telescope say they do not see the purported excess. The observations don't disprove the existence of dark matter, but they...

A 10-year study of 100,000 galaxies close to our own offers compelling proof that long-hypothesized "dark matter" does exist and is in fact a guiding force behind the structure of the universe, a team of Australian, British, and American astronomers revealed this week. Saying that "the universe we see is really quite structured," one of the lead researchers explained that the 10-year "census" of galaxies near our own Milky Way offers powerful evidence that this invisible dark matter "seems to hold the galaxies together." The dark matter's influence on galaxies "stops their constituent stars from flying off and it seems...

PARIS (AFP) – European astronomers said on Wednesday that an anomalous energy signal detected by an orbiting satellite could be a telltale of the enigmatic substance known as dark matter. The researchers, in a study appearing in the British journal Nature, say the hunch is that they picked up a signature of this strange phenomenon, but more work is needed. Some years ago, astrophysicists calculating the amount of matter in the Universe arrived at the startling discovery that ordinary material -- atoms -- comprises perhaps as little as five percent of the stuff in the cosmos. The rest, they believe,...

Does Dark Energy Really Exist? Or does Earth occupy a very unusual place in the universe? Scientific American, March 2009 By Timothy Clifton and Pedro G. Ferreira ... Most of us are very familiar with the idea that our planet is nothing more than a tiny speck orbiting a typical star, somewhere near the edge of an otherwise unnoteworthy galaxy. In the midst of a universe populated by billions of galaxies that stretch out to our cosmic horizon, we are led to believe that there is nothing special or unique about our location. But what is the evidence for this...

Nov. 19, 2008: An international team of researchers has discovered a puzzling surplus of high-energy electrons bombarding Earth from space. The source of these cosmic rays is unknown, but it must be close to the solar system and it could be made of dark matter. Their results are being reported in the Nov. 20th issue of the journal Nature. "This is a big discovery," says co-author John Wefel of Louisiana State University. "It's the first time we've seen a discrete source of accelerated cosmic rays standing out from the general galactic background." Galactic cosmic rays are subatomic particles accelerated...

The first stars to light the early universe may have been powered by dark matter, according to a new study. Researchers from the University of Michagan, Ann Arbor call these very first stars "Dark Stars," and propose that dark matter heating provided the energy for these stars instead of fusion. The researchers propose that with a high concentration of dark matter in the early Universe, the theoretical particles called Weakly Interacting Massive Particles(WIMPs), collected inside the first stars and annihilated themselves to produce a heat source to power the stars. "We studied the behavior of WIMPs in the first stars,"...

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...

Proton discovery may cast doubt on dark-matter theories. The Milagro detector has seen cosmic-ray hot-spots.Milagro / U. Maryland / LANL Hot on the heels of speculation that cosmic rays may have revealed the signature of elusive dark matter in space, new observations could challenge that idea and reinforce an alternative explanation.A seven-year-long experiment at the Milagro cosmic-ray detector near Los Alamos, New Mexico, has revealed 'bright patches' of high-energy cosmic rays in the sky1 – something incompatible with a dark-matter source.Cosmic rays are charged particles, mostly protons and electrons, that are produced in space and generally have a characteristic energy...

The multi-million dollar 1000 Genomes project is set to be finished in a year. The same but different. The 1000 Genomes project aims to catalogue human genetic variation.Punchstock An almost complete catalogue of human genetic variation could be available by the end of 2009, thanks to a massive genome sequencing project that includes academic and industrial partners around the world.Announcing completion of the pilot phase of the 1000 Genomes project, the project's co-chair David Altshuler said last week that it has already successfully catalogued 3.8 trillion bases of sequence — approximately a thousand times the number found in a single...

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...

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...

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...

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.

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...

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...

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...

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.

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....

GENEVA - It has been called an Alice in Wonderland investigation into the makeup of the universe — or dangerous tampering with nature that could spell doomsday. Whatever the case, the most powerful atom-smasher ever built comes online Wednesday, eagerly anticipated by scientists worldwide who have awaited this moment for two decades.

HERE IS THE STORY. A black activist commissioner in Dallas County was upset in a meeting by the use of the term "black hole." I called the Commissioners Court and asked for Commissioner Price. They connected me with his secretary, Melanie. We had a nice friendly conversation. It is not racist, and I am not afraid to say it, but her voice indicated that she was a black lady. MELANIE: Commissioner Wiley. DFU: Yes, ma'am, I'm Doug and I'm calling from California about the story of the black hole and Commissioner Wiley. M: Yes, sir. (sort of a little...

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....

A detailed analysis of eight dwarf galaxies that orbit the Milky Way indicates that their orbital behaviour can be explained more accurately with Modified Newtonian Dynamics (MOND) than by the rival, but more widely accepted, theory of dark matter. The results were presented by Garry Angus, of the University of St Andrews, at the RAS National Astronomy Meeting in Belfast on Wednesday 2nd April. 'MOND was first suggested to account for things that we see in the distant universe. This is the first detailed study in which we've been able to test out the theory on something close to home....

PARIS (AFP) - An international team of astronomers peering into the deep Universe said on Thursday they had mapped the biggest-ever structure of the enigmatic substance known as dark matter. They detected a web of matter spanning 270 million light years, or more than 2,000 times the size of our own galaxy, the Milky Way, they said. Around a fifth of the Universe is believed to consist of dark matter, spreading out in mysterious filaments, sheets and clusters. But, with present technology, it cannot be seen directly. Its existence is perceived indirectly, through the gravitational pull it exerts on light....

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...

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...

Einstein's self-proclaimed "biggest blunder" -- his postulation of a cosmological constant (a force that opposes gravity and keeps the universe from collapsing) -- may not be such a blunder after all, according to the research of an international team of scientists that includes two Texas A&M University researchers. The team is working on a project called ESSENCE that studies supernovae (exploding stars) to figure out if dark energy – the accelerating force of the universe – is consistent with Einstein’s cosmological constant. Texas A&M researchers Nicholas Suntzeff and Kevin Krisciunas are part of the project, which began in October of...

HAVE we hastened the demise of the universe by looking at it? That’s the startling question posed by a pair of physicists, who suggest that we may have accidentally nudged the universe closer to its death by observing dark energy, which is thought to be speeding up cosmic expansion. Lawrence Krauss of Case Western Reserve University in Cleveland, Ohio, and colleague James Dent suggest that by making this observation in 1998 we may have caused the universe to revert to a state similar to early in its history, when it was more likely to end. “Incredible as it seems, our...

Stays away from topic of financial market turmoil In a speech in Berlin on Tuesday, Bernanke did not address the current financial market turmoil or credit crunch. His comments stuck to the troubling issue of the large U.S. current account gap and corresponding surpluses in China and oil-exporting countries. Many economists and the International Monetary Fund have worried for years that there might be a sudden, sharp decline in foreign appetite for U.S. dollars, requiring higher U.S. interest rates to attract the necessary foreign capital to fund American's spendthrift ways. "What are the prospects for a gradual and orderly rebalancing...

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...

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...

An international team of astronomers have conclusive new evidence that a recently discovered "dark galaxy" is, in fact, an object the size of a galaxy, made entirely of dark matter. Although the object, named VIRGOHI21, has been observed since 2000, astronomers have been slowly ruling out every alternative explanation. In a new research paper, entitled 21-cm synthesis observations of VIRGOHI 21 – a possible dark galaxy in the Virgo Cluster, researchers provide updated evidence about this mysterious galaxy. They have now performed a high resolution observations of VIRGOHI21 using the Westerbork Synthesis Radio Telescope (WSRT), to better pin down the...

Astronomers have discovered an enormous, ghostly ring of dark matter 5 billion light years away — the most blatant evidence to date for the existence of a mysterious substance hidden throughout the universe. Dark matter makes up a vast majority of gravity-exerting mass in the universe, while only about 10 percent is matter we can see and touch. If dark matter didn't exist, scientists say, galaxies like the Milky Way would have already flown apart from a severe lack of gravitational "glue." Researchers pointed the aging but powerful Hubble Space Telescope toward a cluster of galaxies known as cluster...

...More than 100 scientists from across the globe are descending on McMaster University today... just 5 per cent of the universe is made up of matter we've long known about -- atoms, light, etc. The rest is mysterious dark matter (25 per cent) and the more recently discovered dark energy (70 per cent)... "For the first time in the history of man, it's possible to figure out the total energy in the universe, and the big news is that atoms are at most 5 per cent of what's out there," says Cliff Burgess, Mac professor of physics and astronomy, and...

Take one part unidentified goop. Add three parts mysterious energy. Throw in a dash of ordinary atoms. Mix. Compress. Explode. Let expand for 13.7 billion years. It's an absurd recipe, but it's one that makes cosmologists drool. Ten years ago, no one could agree on what the universe is made of, how it is shaped, or what its ultimate fate will be. But less than five years later, long-awaited measurements and one stunning discovery forever transformed our picture of the universe. The resulting model, often called the concordance model, holds that 22 percent of the universe is composed of dark...

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...

Close window Published online: 7 January 2007; | doi:10.1038/news070101-7 Dark matter mappedFirst three-dimensional picture of elusive matter throws up mystery.Katharine Sanderson Concentrations of dark matter (mapped in contours above) usually - but not always - match up with normal matter (coloured). Hot on the heels of evidence last year that dark matter really does exist (see 'Dark matter spied in galactic collision'), the same technique has been used to map this uncharacterized mass across half a million distant galaxies. The map shows that, as predicted, the mysterious dark matter that makes up a quarter of the Universe forms a...

In the standard theory of gravity—general relativity—dark matter plays a vital role, explaining many observations that the standard theory cannot explain by itself. But for 70 years, cosmologists have never observed dark matter, and the lack of direct observation has created skepticism about what is really out there.Lately, some scientists have turned the question around, from “is dark matter correct?” to “is our standard theory of gravity correct?” Most recently, Fermilab scientists Scott Dodelson and former Brinson Fellow Michele Liguori demonstrated one of the first pieces of theoretical evidence that an alternative theory of gravity can explain the large scale...

After decades of intensive effort by both experimental and theoretical physicists worldwide, a tiny particle with no charge, a very low mass and a lifetime much shorter than a nanosecond, dubbed the "axion," has now been detected by the University at Buffalo physicist who first suggested its existence in a little-read paper as early as 1974. The finding caps nearly three decades of research both by Piyare Jain, Ph.D., UB professor emeritus in the Department of Physics and lead investigator on the research, who works independently -- an anomaly in the field -- and by large groups of well-funded physicists...

MOON DAILYBig Bang Afterglow Fails An Intergalactic Shadow Test Because it is seen coming from every direction in nearly uniform power and frequency, cosmologists theorized that the microwave background is afterglow radiation left over by the Big Bang that created the universe. by Staff Writers Huntsville AL (SPX) Sep 03, 2006 The apparent absence of shadows where shadows were expected to be is raising new questions about the faint glow of microwave radiation once hailed as proof that the universe was created by a "Big Bang." In a finding sure to cause controversy, scientists at The University of Alabama in...

When Douglas Clowe of the University of Arizona in Tucson announced on 21 August that his team had "direct proof of dark matter's existence", it seemed the issue had been settled. Now proponents of the so-called modified theories of gravity, who explain the motion of stars and galaxies without resorting to dark matter, have hit back and are suggesting that Clowe's team has jumped the gun. "One should not draw premature conclusions about the existence of dark matter without a careful analysis of alternative gravity theories," writes John Moffat, of the University of Waterloo in Ontario, Canada, who pioneered an...

A football player tackled hard enough may lose his helmet. Now, astronomers have found two clusters of galaxies that collided so hard one of them has lost its halo of dark matter, the mysterious invisible stuff that swaddles ordinary matter, according to measurements of the motions of stars and galaxies. In this picture, a composite based on observations with the Hubble Space Telescope, the Chandra X-Ray Observatory and other telescopes, the pink, bullet-shaped cloud of hot gas in a cluster speeding from left to right has been slowed and left behind by its dark matter, the blue blob to the...

BOSTON (Reuters) - A team of U.S. scientists has found the first direct evidence of the existence of "dark matter," a little-understood substance with a huge influence on gravity, the team's leader said on Tuesday. Scientists still do not know what exactly dark matter is, but have theorized it must exist to account for the amount of gravity needed to hold the universe together. They estimate that the substance accounts for 80 to 90 percent of the matter in the universe. The more familiar kind of matter, which can be seen and felt, makes up the rest. Now researchers led...

Everyone is scientific circles is abuzz with the big news: there's proof that dark matter exists! The paper from the scientists who made the discovered is here; and a Sean Carroll (no relation) has a very good explanation on his blog, Cosmic Variance. This discovery happens to work as a great example of just why good science needs good math. As I always say, one of the ways to recognize a crackpot theory in physics is by the lack of math. For an example, you can look at the electric universe folks. They have a theory, and they make predictions:...

Dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies. The discovery, using NASA's Chandra X-ray Observatory and other telescopes, gives direct evidence for the existence of dark matter. "This is the most energetic cosmic event, besides the Big Bang, which we know about," said team member Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. These observations provide the strongest evidence yet that most of the matter in the universe is dark. Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it...