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The bonanza of evidence suggests that dark matter might be far more complicated than we had ever imagined. For starters, the theoretician's favourite dark-matter candidate is falling out of favour, with the latest experiments making the case for new, exotic varieties of dark matter. If they are right, we could be living next to a "hidden sector", an unseen aspect of the cosmos that exists all around us and includes a new force of nature.
Originally posted by letthereaderunderstand
reply to post by sunny_2008ny
If gravity was a force, then it would change dramatically with density of an object as if you could add more invisible force in proportion to the density that the "graviton" is packed in then it would stand, but science is not needed to know this, only bowling balls....lol
If gravity was a force
What does gravity have to do with any of this?
dark matter is simply manifestation of surface tension energy of every density gradient of vacuum, which is forming gravity field of massive bodies. This surface tension behaves like weak repulsive force of mercury droplets, which decreases a gravity action of increased energy density here. Surface tension phenomena are most pronounced near surface of neutron stars and black holes, where they lead into quantum wave behavior of their surface, but they manifest itself by weak repulsive force even inside of our solar system (compare the Pioneer spacecraft anomaly, Allais effect and some other phenomena).
Originally posted by sunny_2008ny
reply to post by letthereaderunderstand
If gravity was a force
Isnt gravity real time. Look at light, it takes 8 minutes to travel to earth, but gravity is "real time" and instantaneous, there is no time lag. How do you explain that? Gravity exerts it's force on us and hence we have weights. But the "force" exerted by the Sun on the planets, earth on moon etc results in the orbits of these bodies. Isnt gravity a force then?
Originally posted by johnsky
Yes yes, gravity is fascinating, truly fascinating... but lets get back to dark matter itself yes?
Given that my field of study has little to nothing to do with astrophysics, my question is, how would this be tested? As far as I know so far, we haven't got a way to actually measure dark matter yet.
I may be outdated on the progress, but I was under the assumption that all of this was still very much theoretical.
However, the article does point to the suggestion that we've got an abundance of evidence... what evidence would this be?
I am incredibly out of date on my information, clearly.
Originally posted by googolplex
It is also my thought that once the massive gravity wells, Black Holes rule, the universe will again close, Gravity will rest till next Bang. My thoughts on this time period is 23 trillion years, till Big Crunch.
In astronomy and cosmology, dark matter is hypothetical matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter . Dark matter is postulated to explain the flat rotation curves of spiral galaxies and other evidence of "missing mass" in the universe. According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter and dark energy account for the vast majority of the mass in the observable universe.
Although dark matter was detected by its gravitational lensing in August 2006, many aspects of dark matter remain speculative. The DAMA/NaI experiment and its successor DAMA/LIBRA have claimed to directly detect dark matter passing through the Earth, though most scientists remain skeptical since negative results of other experiments are (almost) incompatible with the DAMA results if dark matter consists of neutralinos.
Data from a number of lines of evidence, including galaxy rotation curves, gravitational lensing, structure formation, and the fraction of baryons in clusters and the cluster abundance combined with independent evidence for the baryon density, indicate that 85-90% of the mass in the universe does not interact with the electromagnetic force . This "nonbaryonic dark matter" is evident through its gravitational effect. Historically, three categories of nonbaryonic dark matter have been postulated:
Hot dark matter - nonbaryonic particles that move ultrarelativistically
Warm dark matter - nonbaryonic particles that move relativistically
Cold dark matter - nonbaryonic particles that move non-relativistically
The Virgo along with the Hydra and other superclusters are streaming at a speed of 6x107 cm/sec toward the "Great Attractor", which is a gigantic unseen mass located near the A3627 (Norma) cluster in the Centaurus Wall near the galactic plane. In comparison, the speed of cosmic expansion is about 7x108 cm/sec at a distance of 100 megapc.
There is a problem with the formation of superclusters. Theory associates a characteristic time for the gravitational settling near the center of a clump. For a density fluctuation of 1.7%, it is of the order of 1 billion years; it would be 13 billion years for 0.3% fluctuation, etc. However, CMBR measurements imply a fluctuation of only 0.001%, which requires a settling time 1000 times longer than the age of the universe. The inconsistency can be resolved only if there is "dark matter" to enhance the fluctuation.
Since dark matter interacts with normal matter only through gravity, the pressure that kept the normal gas from collapsing coundn't act on it. Particles of dark matter enjoyed an unimpeded assembly into large structures (in the form of primordial fluctuation) long before the normal gas could begin to get organized. By the time normal matter decoupled from the photons, the dark matter had already grown into a primitive web-like network. As soon as the normal matter lost its support from the photon pressure, the gravity from the pre-existing dark matter structures quickly pulled normal gas into the web. In this way, normal matter was given a gravitational "head start" by dark matter.
Recently in early 2004, several new measurements of galaxies and clusters in the early universe indicate that the structures involving galaxies and clusters are larger than expected with the new standard "dark-energy" cosmology. The controversy centers on the inability of a dark-energy dominated universe to create such large structures within such a short time (1/5 of the present age). More researches are required to validate such observations. The next step is to map an area of sky ten times larger, to get a better idea of the large-scale structure. Several such surveys are currently under way.
In 2008, using the cluster catalog and WMAP's data, bulk cluster motions of nearly 108 cm/sec has been identified toward patch of sky near A3627 in the direction between the constellations of Centaurus and Vela. The clusters show a small but measurable velocity that is independent of the universe's expansion and does not change as distances increase. It is suggested that such motion (now called darkflow) is caused by the gravitational attraction of matter that lies beyond the observable universe.