Dark Energy Found Stifling Growth in Universe
December 16th, 2008
On the left is a composite image of Abell 85 made from X-rays from NASA's Chandra X-ray Observatory and optical light from the Sloan Digital Sky Survey. This galaxy cluster is one of 86 observed with Chandra to trace how dark energy has stifled the growth of these massive structures over the last 7 billion years. Galaxy clusters are the largest collapsed objects in the Universe and are ideal for studying the properties of dark energy across the Universe. The illustration on the right shows snapshots from a simulation representing the growth of cosmic structures when the Universe was 0.9 billion, 3.2 billion, and 13.7 billion years old. Credit: X-ray (NASA/CXC/SAO/A.Vikhlinin et al.); Optical (SDSS); Illustration (MPE/V.Springel)
(PhysOrg.com) -- For the first time, astronomers have clearly seen the effects of "dark energy" on the most massive collapsed objects in the universe using NASA's Chandra X-ray Observatory. By tracking how dark energy has stifled the growth of galaxy clusters and combining this with previous studies, scientists have obtained the best clues yet about what dark energy is and what the destiny of the universe could be.
This work, which took years to complete, is separate from other methods of dark energy research such as supernovas. These new X-ray results provide a crucial independent test of dark energy, long sought by scientists, which depends on how gravity competes with accelerated expansion in the growth of cosmic structures. Techniques based on distance measurements, such as supernova work, do not have this special sensitivity.
This pair of illustrations shows the change in scale of the Universe over cosmic time, followed by the change in the weight of a typical galaxy cluster over the same time frame. The orange line shows the evolution of the observed Universe, with dark energy and cosmic acceleration, and the yellow and blue lines show high and low density models that do not contain dark energy. The observed change in weight of galaxy clusters over the last 7 billion years agrees very well with predictions for a Universe dominated by dark energy. (Illustration: NASA/CXC/M.Weiss)
Scientists think dark energy is a form of repulsive gravity that now dominates the universe, although they have no clear picture of what it actually is. Understanding the nature of dark energy is one of the biggest problems in science. Possibilities include the cosmological constant, which is equivalent to the energy of empty space. Other possibilities include a modification in general relativity on the largest scales, or a more general physical field.To help decide between these options, a new way of looking at dark energy is required. It is accomplished by observing how cosmic acceleration affects the growth of galaxy clusters over time.
"This result could be described as 'arrested development of the universe'," said Alexey Vikhlinin of the Smithsonian Astrophysical Observatory in Cambridge, Mass., who led the research. "Whatever is forcing the expansion of the universe to speed up is also forcing its development to slow down."
Vikhlinin and his colleagues used Chandra to observe the hot gas in dozens of galaxy clusters, which are the largest collapsed objects in the universe. Some of these clusters are relatively close and others are more than halfway across the universe.
The results show the increase in mass of the galaxy clusters over time aligns with a universe dominated by dark energy. It is more difficult for objects like galaxy clusters to grow when space is stretched, as caused by dark energy. Vikhlinin and his team see this effect clearly in their data. The results are remarkably consistent with those from the distance measurements, revealing general relativity applies, as expected, on large scales.
"For years, scientists have wanted to start testing how gravity works on large scales and now, we finally have," said William Forman, a co-author of the study from the Smithsonian Astrophysical Observatory. "This is a test that general relativity could have failed."
When combined with other clues -- supernovas, the study of the cosmic microwave background, and the distribution of galaxies -- this new X-ray result gives scientists the best insight to date on the properties of dark energy.
The study strengthens the evidence that dark energy is the cosmological constant. Although it is the leading candidate to explain dark energy, theoretical work suggests it should be about 10 raised to the power of 120 times larger than observed. Therefore, alternatives to general relativity, such as theories involving hidden dimensions, are being explored.
"Putting all of this data together gives us the strongest evidence yet that dark energy is the cosmological constant, or in other words, that 'nothing weighs something'," said Vikhlinin. "A lot more testing is needed, but so far Einstein's theory is looking as good as ever."
These results have consequences for predicting the ultimate fate of the universe. If dark energy is explained by the cosmological constant, the expansion of the universe will continue to accelerate, and the Milky Way and its neighbor galaxy, Andromeda, never will merge with the Virgo cluster. In that case, about a hundred billion years from now, all other galaxies ultimately would disappear from the Milky Way's view and, eventually, the local superclusters of galaxies also would disintegrate.
The work by Vikhlinin and his colleagues will be published in two separate papers in the Feb. 10 issue of The Astrophysical Journal.
Provided by Chandra X-ray Center
Jun 09, 2009 |
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No, 99.86% would be correctly rounded to 100%.
No, if that is supposed to be the mass of the sun, try this:
1.9891 ×10^30 kg
which is 332,946 Earths
http://www.presto...ndex.htm
hmm dark energy is turning out just like gravity, its there, we see it, we can sense it, we have some form of calculations for it, BUT WTF IS IT????? We have no idea but we'll brush over that.
we still have no clear idea what gravity is, but we have some idea what its effects are. How in the universe then can they even begin to think they can glean any understanding of this dark energy?
WOW. Just WOW. This is exactly the kind of statement that can end a career. I wouldn't be throwing around stuff like this so early and easily if I was him.
I have a difficult time beleiving that antimatter and matter repulse eacother, seeing as they are basically the same thing with opposite charges. Wouldn't that mean they attract eachother?
In brief, if the curvature of space has some energy by GR, we shouldn't neglect the mass corresponding this energy in more general reference frame. This mass density should exhibit and additional gravitational field, which balances the action of the gravity and mass, which has caused it, originally.
In AWT this effect corresponds a "surface tension" of gravity field gradient (a blob of dense vacuum around massive objecys, responsible the gravity field and gravity lensing effects).
The same result can be derived from light spreading from massive object under omnidirectional Universe expansion: light freezes in the expanding space gradually, which can be interpreted as a cloud of more dense vacuum (dark matter), surrounding such object.
Blind adherence to mainstream opinion was exactly, which ended the carrier of Galileo - we can see, the fear of violation the intersubjectivelly accepted truth can have a quite opposite effect in its remote/large scale consequences.
By AWT such result exactly corresponds the supersymmetric action of gravity at short/long distance and/or low/high energy scales. This is because the information spreading acellerates energy spreading in civilisation, so it undegoes the same laws, like energy spreading in Universe. By AWT every phenomena or law "violates itself" in more general scale, so if you understand repulsive stance toward remote ideas in science (pathological skepticism), you can understand the nature of repulsive action for gravity at larger distances - and vice-versa.
This is not gravity. Conceptualy, the equation is very similar to Newton's equation for gravity and the forces act in much the same way. But mathamaticaly, the numbers are different for Coulombs electric force and for gravity. Also, the dielectric constant in Coulomb's equation changes changes the force depending on the medium between the two charges, whereas the gravitational force between two particles will be the same no matter what the medium is(so long as the radius does not change and you are only looking at the force between the two particles independent of the gravitational forces of the rest of the universe).
And I still don't understand why matter and antimatter would repel eachother.
When considering matter and antimatter atoms, the nucleus of the matter atom is blocked from the nucleus of the antiatom by orbiting particles, this is the blocking of an attractive force. The remaining net forces between the atom and antiatom are repulsive.
Hi theophys, the eclipses are easier to understand if you sketch an atom and an antiatom. The most basic is hydrogen and antihydrogen. The electron blocks the proton and antiproton. The positron also blocks the proton and antiproton. These eclipses block the attractive force between the atom and antiatom. The balance of the other force between the atom and antiatom are repulsive, the net force is therefore repulsive. The eclipses are similar to a lunar eclipse except that the electrical fields are blocked as per Gauss's law. The atom eclipses are for very short periods of time.
As for gravity
I don't have the two being the same. I come up with gravity being much weaker at this scale.
I look forward to reading that, but for now I'm just bafled. My summed forces are different.
of "from the bottom"? A spiral system that moves through objects and then "re-groups" on the other side of said object, dark energy moves slowly like
a spiral galaxy. It's function is to "move or pull atoms apart"