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Dark matter and dark energy may be different aspects of a single unknown force
Posted on Saturday, July 03, 2004 @ 15:43:45 UTC by vlad
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In the last few decades, scientists have discovered that there is a lot more to the universe than meets the eye: the cosmos appears to be filled with not just one, but two invisible constituents -dark matter and dark energy - whose existence has been proposed based solely on their gravitational effects on ordinary matter and energy.
Now, theoretical physicist Robert J. Scherrer has come up with a model that could cut the mystery in half by explaining dark matter and dark energy as two aspects of a single unknown force. His model is described in a paper titled "Purely Kinetic k Essence as Unified Dark Matter" published online by Physical Review Letters on June 30 and available online at http://arxiv.org/abs/astro-ph/0402316.
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Read the public release from: www.eurekalert.org/
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"Dark matter and dark energy may be different aspects of a single unknown force" | Login/Create an Account | 2 comments | Search Discussion |
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Can dark energy be measured in the lab? (Score: 1) by vlad on Saturday, July 03, 2004 @ 22:29:31 UTC (User Info | Send a Message) http://www.zpenergy.com | On the same topic, from the KeelyNet list, Jerry Decker wrote:
Subject: can dark energy be measured in the lab?
Date: Wed, 30 Jun 2004 22:42:48 -0700
Hola Folks!
What a fascinating idea and approach;
http://physicsweb.org/article/news/8/6/17
29 June 2004
It might be possible to measure the properties of "dark energy" in the laboratory according to physicists in the UK and Canada. A relatively simple experiment based on superconducting devices known as Josephson junctions could show if some or all of the dark energy in the universe is due to quantum fluctuations of the vacuum (C Beck and M Mackey 2004 arXiv.org/abs/astro-ph/0406504).
Quantum fluctuations mean that the vacuum is not empty as is assumed in classical physics. These fluctuations, also known as zero-point fluctuations, are a consequence of the uncertainty principle, and they give the vacuum a structure that manifests itself in a variety of different ways such as the Casimir effect. Physicists have already measured the effects of this "vacuum energy" in circuits containing Josephson junctions.
A series of astrophysical observations have suggested that as much as 73% of the universe is made of dark energy -- a gravitationally repulsive material that is causing the expansion of the universe to accelerate. However, no one knows what dark energy is made of. Vacuum energy is one candidate for dark energy, although the amount of energy in the vacuum predicted by theory is some 120 orders of magnitude more than the amount indicated by observations.
In 1982, Roger Koch and colleagues, then at the University of California at Berkeley and the Lawrence Berkeley Laboratory, performed an experiment in which they measured the frequency spectrum of current fluctuations in Josephson junctions.
Their system was cooled to millikelvin temperatures so that thermal vibrations were reduced to a minimum, leaving only zero-point quantum fluctuations. Now, Christian Beck at Queen Mary University of London and Michael Mackey at McGill University in Montreal have re-analysed these results in the light of recent astrophysical estimates of the density of dark energy in the universe.
Beck and Mackey argue that the zero-point fluctuations measured by Koch's team imply a non-zero density for the vacuum energy, and say that this value cannot exceed the value for the density of dark energy in the universe. Using this premise, they predict that there should be a cut-off in the spectrum of the fluctuations at a frequency of around
1.69 x 1012 Hertz.
Beck and Mackey believe that future experiments with a new generation of Josephson junctions that work at higher frequencies could help to clarify whether or not this cut-off exists. Such experiments would also show if dark energy is indeed related to vacuum energy.
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I was just talking with a guy about a correlation to this...the claim that electrical arcs in a vacuum seem to get additional energy on the output that is stronger than that used for the input. Such was a claim made by Zielinsky in conversations with Patrick Flanagan and in his presentation and workshop at an INE conference in Denver several years ago. And it correlates with the deceased Russian scientist Chernetsky as at;
http://www.keelynet.com/energy/chernet1.txt
...Classical physics cannot explain what happens when a plasma discharger placed in the Chernetski circuit is started: for no apparent reason the ammeter pointer shows triple strength-of-current increase [sic] and energy output is several times above input. The plant's efficiency is much more than 1.
...When the discharge currents reached criticality, superstrong current was "born" in the generator and went back into the network, playing havoc with the safety devices calculated for short-circuit.
...The researchers relied on the present-day quantum physics idea of "zero-point oscillations" in physical vacuum. Such oscillations signifying the birth and annihilation of virtual pairs -- the particle and anti-particle, distinguished from the normal elementary particles by a negligibly short life, a mere 8.10/-21[sic] sec.
...Emerging below the zero energy level from "nothing" and returning to "nothing", virtual particles appear to defy the law of conservation of energy.
..."The self-generating discharge emerges when the discharge current reach a definite critical density, when the magnetic fields they create ensure magnetisation of plasma electrons and they begin to perform mostly cycloid movements.
...The interaction of currents with their magnetic fields forces the electrons to deviate to the cylinder-shaped discharge axis and the electrical field emerges. It has proved to 'switch on' the physical vacuum: in this field the vacuum is polarised and consequently the virtual pairs begin to move in a definite direction, instead of chaotically. the virtual positrons accelerate plasma electrons, giving them part of their energy.
...The current in the circuit builds up and additional energy is discharged on the resistor switched into the discharge circuit. Clearly, only part of the tremendous vacuum energy is extracted.
..."We've developed several circuit versions which can find application. In the later experiment with an input power of 700 watts, that extracted by the generator loads resistance was three kilowatts, or nearly five times more.
...This is by far not the limit and with more powerful plants and the corresponding calculations megawatts of free electricity can be produced from a minimal power source."
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http://www.keelynet.com/energy/pearson.htm
...Anyway, this guy says two unlike polarities (positive against negative) can be thrown against each other and instead of annihilating, the primaries will increase in number, by as much as 18% more than the original energies....from EACH collision of opposites. To clarify with a direct quote;
...with the vacuum underpinned by a compound medium of opposites we can call the 'ether', a whole new vista appears. Now energy CAN be created or destroyed - provided negative and positive energies change TOGETHER in EXACTLY balanced amounts! (can you say scalar???)
...At first this seemed to present a difficulty. Would not the two halves of ether MUTUALLY ANNIHILATE as primaries of opposite energy collided at high speed?
...it turned out that the need to conserve momentum prevented MUTUAL annihilation of energies from occurring during collisions. Indeed the two conservation laws of energy AND momentum, which had to be applied SIMULTANEOUSLY, led to a totally different result.
...Instead of annihilating, primaries INCREASED in number! In fact, 18% MORE of BOTH kinds appeared, on average, from EACH collision of opposites.
...When primaries collide by approaching one another from any other direction, so that their trajectories intersect at some ARBITRARY ANGLE, the analysis is only made slightly more complicated. Note it is necessary to consider RELATIVE velocities of approach. From such vantage points some collisions will also APPEAR to be HEAD-ON, so yielding THE SAME RESULT as the one previously described.
...However, for collisions NOT HEAD-ON, a sideway SCATTERING MOTION is imparted. And this applies equally to the general case just mentioned. Each primary GAINS extra momentum in this transverse direction, the positive one gaining positive momentum and the negative one gaining the negative variety. It follows that corresponding evaluation then yields the average gain ratio just quoted (18%).
...However, the positive and negative gains of both momentum and energy could CANCEL under conditions of MULTIPLE COLLISIONS (noise). It therefore follows that everything that exists must ultimately have derived from the zero energy state of nothingness.
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Speed of light may have changed recently (Score: 1) by vlad on Sunday, July 04, 2004 @ 00:17:31 UTC (User Info | Send a Message) http://www.zpenergy.com | And another interesting one, on a related topic:
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Speed of light may have changed recently
19:00 30 June 04
Exclusive from New Scientist Print Edition.
The speed of light, one of the most sacrosanct of the universal physical constants, may have been lower as recently as two billion years ago - and not in some far corner of the universe, but right here on Earth.
The controversial finding is turning up the heat on an already simmering debate, especially since it is based on re-analysis of old data that has long been used to argue for exactly the opposite: the constancy of the speed of light and other constants.
A varying speed of light contradicts Einstein's theory of relativity, and would undermine much of traditional physics. But some physicists believe it would elegantly explain puzzling cosmological phenomena such as the nearly uniform temperature of the universe. It might also support string theories that predict extra spatial dimensions.
The fine structure constant
The threat to the idea of an invariable speed of light comes from measurements of another parameter called the fine structure constant, or alpha, which dictates the strength of the electromagnetic force. The speed of light is inversely proportional to alpha, and though alpha also depends on two other constants (see graphic), many physicists tend to interpret a change in alpha as a change in the speed of light. It is a valid simplification, says Victor Flambaum of the University of New South Wales in Sydney.
It was Flambaum, along with John Webb and colleagues, who first seriously challenged alpha's status as a constant in 1998. Then, after exhaustively analysing how the light from distant quasars was absorbed by intervening gas clouds, they claimed in 2001 that alpha had increased by a few parts in 105 in the past 12 billion years.
Natural nuclear reactor
But then German researchers studying photons emitted by caesium and hydrogen atoms reported earlier in June that they had seen no change in alpha to within a few parts in 1015 over the period from 1999 to 2003 (New Scientist, 26 June) though the result does not rule out that alpha was changing billions of years ago.
Throughout the debate, physicists who argued against any change in alpha have had one set of data to fall back on. It comes from the world's only known natural nuclear reactor, found at Oklo in Gabon, West Africa.
The Oklo reactor started up nearly two billion years ago when groundwater filtered through crevices in the rocks and mixed with uranium ore to trigger a fission reaction that was sustained for hundreds of thousands of years. Several studies that have analysed the relative concentrations of radioactive isotopes left behind at Oklo have concluded that nuclear reactions then were much the same as they are today, which implies alpha was the same too.
That is because alpha directly influences the ratio of these isotopes. In a nuclear chain reaction like the one that occurred at Oklo, the fission of each uranium-235 nucleus produces neutrons, and nearby nuclei can capture these neutrons.
For example, samarium-149 captures a neutron to become samarium-150, and since the rate of neutron capture depends on the value of alpha, the ratio of the two samarium isotopes in samples collected from Oklo can be used to calculate alpha.
A number of studies done since Oklo was discovered have found no change in alpha over time. "People started quoting the reactor [data] as firm evidence that the constants hadn't changed," says Steve Lamoreaux of Los Alamos National Lab (LANL) in Albuquerque, New Mexico.
Energy spectrum
Now, Lamoreaux, along with LANL colleague Justin Torgerson, has re-analysed the Oklo data using what he says are more realistic figures for the energy spectrum of the neutrons present in the reactor. The results have surprised him. Alpha, it seems, has decreased by more than 4.5 parts in
108 since Oklo was live (Physical Review D, vol 69, p121701).
That translates into a very small increase in the speed of light (assuming no change in the other constants that alpha depends on), but Lamoreaux's new analysis is so precise that he can rule out the possibility of zero change in the speed of light. "It's pretty exciting," he says.
So far the re-examination of the Oklo data has not drawn any fire. "The analysis is fine," says Thibault Damour of the Institute of Advanced Scientific Studies (IHES) in Bures-sur-Yvette in France, who co-authored a 1996 Oklo study that found no change in alpha. Peter Moller of LANL, who, along with Japanese researchers, published a paper in 2000 about the Oklo reactor that also found no change in alpha, says that Lamoreaux's assumptions are reasonable.
The analysis might be sound, and the assumptions reasonable, but some physicists are reluctant to accept the conclusions. "I can't see a particular mistake," says Flambaum. "However, the claim is so revolutionary there should be many independent confirmations."
While Flambaum's own team found that alpha was different 12 billion years ago, the new Oklo result claims that alpha was changing as late as two billion years ago. If other methods confirm the Oklo finding, it will leave physicists scrambling for new theories. "It's like opening a gateway," says Dmitry Budker, a colleague of Lamoreaux's at the University of California at Berkeley.
Horizon problem
Some physicists would happily accept a variable alpha. For example, if it had been lower in the past, meaning a higher speed of light, it would solve the "horizon problem".
Cosmologists have struggled to explain why far-flung regions of the universe are at roughly the same temperature. It implies that these regions were once close enough to exchange energy and even out the temperature, yet current models of the early universe prevent this from happening, unless they assume an ultra-fast expansion right after the big bang.
However, a higher speed of light early in the history of the universe would allow energy to pass between these areas in the form of light.
Variable "constants" would also open the door to theories that used to be off limits, such as those which break the laws of conservation of energy. And it would be a boost to versions of string theory in which extra dimensions change the constants of nature at some places in space-time.
But "there is no accepted varying-alpha theory", warns Flambaum. Instead, there are competing theories, from those that predict a linear rate of change in alpha, to those that predict rapid oscillations. John Barrow, who has pioneered varying-alpha theories at the University of Cambridge, says that the latest Oklo result does not favour any of the current theories. "You would expect alpha to stop [changing] five to six billion years ago," he says.
Reaction rate
Before Lamoreaux's Oklo study can count in favour of any varying alpha theory, there are some issues to be addressed. For one, the exact conditions at Oklo are not known. Nuclear reactions run at different rates depending on the temperature of the reactor, which Lamoreaux assumed was between 227 and 527°C.
Damour says the temperature could vary far more than this. "You need to reconstruct the temperature two billion years ago deep down in the ground," he says.
Damour also argues that the relative concentrations of samarium isotopes may not be as well determined as Lamoreaux has assumed, which would make it impossible to rule out an unchanging alpha. But Lamoreaux points out that both assumptions about the temperature of the Oklo reactor and the ratio of samarium isotopes were accepted in previous Oklo studies.
Another unknown is whether other physical constants might have varied along with, or instead of, alpha. Samarium-149's ability to capture a neutron also depends on another constant, alpha(s), which governs the strength of the strong nuclear attraction between the nucleus and the neutron.
And in March, Flambaum claimed that the ratio of different elements left over from just after the big bang suggests that alpha(s) must have been different then compared with its value today
(Physical Review D, vol 69, p 063506).
While Lamoreaux has not addressed any possible change in alpha(s) in his Oklo study, he argues that it is important to focus on possible changes in alpha because the Oklo data has become such a benchmark in the debate over whether alpha can vary. "I've spent my career going back and checking things that are 'known' and it always leads to new ideas," he says.
Eugenie Samuel Reich
http://www.newscientist.com/news/news.jsp?id=ns99996092 |
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