>>> context weblog
sampling new cultural context
| home | site map | about context | donate | lang >>> español - català |
friday :: september 1, 2006
direct proof of dark matter

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 is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of this collision.

"A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking," said Doug Clowe of the University of Arizona at Tucson, and leader of the study. "These results are direct proof that dark matter exists."

In galaxy clusters, the normal matter, like the atoms that make up the stars, planets, and everything on Earth, is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. This normal matter is bound in the cluster by the gravity of an even greater mass of dark matter. Without dark matter, which is invisible and can only be detected through its gravity, the fast-moving galaxies and the hot gas would quickly fly apart.

The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas was the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not have been seen. Instead, dark matter is required.

This result also gives scientists more confidence that the Newtonian gravity familiar on Earth and in the solar system also works on the huge scales of galaxy clusters.

"We've closed this loophole about gravity, and we've come closer than ever to seeing this invisible matter," Clowe said. >from *NASA finds direct proof of dark matter* . August 21, 2006

related context
astronomers report first direct evidence for dark matter. 'there really is dark matter out there, now we just need to figure out what it is.' august 21, 2006
> dark matter observed. most direct measurement of dark matter allows study of its nature. august 21, 2006
> pioneer anomaly, pointing towards new physics. the spacecraft trajectories could be influenced by the presence of dark matter in the solar system. august 16, 2006
> are black holes at the center of galaxies?. 'bubbles of dark matter could be masquerading as supermassive black holes at the centres of galaxies. if so, they could explain the puzzling pattern of x-ray emissions from the heart of the milky way.' august 16, 2006
> 'dark matter' exhibition. a 'last painting', a zero point beyond which painting could not go, suggesting painting as an object instead of as a window onto another space. and yet it was also experienced as a kind of negative icon, representing a sacred transfiguration of the material into the immaterial. july 7 - september 9, 2006
> galaxies are born inside dark matter clumps. april 17, 2006
> only 4 percent of the universe is ordinary familiar atoms. another 22 percent is an as-yet unidentified dark matter, and 74 percent is a mysterious dark energy. march 16, 2006
> dark energy stars. 'dark energy and dark matter, two of the greatest mysteries confronting physicists, may be two sides of the same coin. a new and as yet
undiscovered kind of star could explain both phenomena and, in turn, remove black holes from the lexicon of cosmology.' march 9, 2006
> milky way vibrations and the galactic warp. 'most prominent of the milky way's satellite galaxies - a pair of galaxies called the magellanic clouds - appears to be interacting with the milky way's ghostly dark matter to create a mysterious warp in the galactic disk.' january 20, 2006
> dark matter candidate. 'mirror matter is an entirely new form of matter predicted to exist if mirror symmetry is a fundamental symmetry of nature.' november 18, 2002
> first 'map' of dark matter. 'while dark matter makes up at least 90% of the mass of the universe, both its composition and its distribution are unknown' march 7, 2000

matter vs. dark matter comprehensive cosmic event

| permaLink

> context weblog archive
december 2006
november 2006
october 2006
september 2006
august 2006
july 2006
june 2006
may 2006
april 2006
march 2006
february 2006
january 2006
december 2005
november 2005
october 2005
september 2005
august 2005
july 2005
june 2005
may 2005
april 2005
march 2005
february 2005
january 2005
december 2004
november 2004
october 2004
september 2004
august 2004
july 2004
june 2004
may 2004
april 2004
march 2004
february 2004
january 2004
december 2003
november 2003
october 2003
june 2003
may 2003
april 2003
march 2003
february 2003
january 2003
december 2002
november 2002
october 2002
july 2002
june 2002
may 2002
april 2002
march 2002
february 2002
january 2002
countdown 2002
december 2001
november 2001
october 2001
september 2001
august 2001

more news in
> sitemap


context archives all www
   "active, informed citizen participation is the key to shaping the network society. a new 'public sphere' is required." seattle statement
| home | site map | about context | donate | lang >>> español - català |
03 http://straddle3.net/context/03/en/2006_09_01.html