So, what's this 'Dark Matter'? What's the significance of it?

Question

Galactic Clash Sheds Light On Dark Matter

WASHINGTON (AFP) - Space telescopes have captured images of a mammoth collision between two galaxy clusters that have shed some light into the universe's mysterious dark matter, NASA said.

The images taken by the Hubble Space Telescope and Chandra X-ray Observatory show a clear separation between dark and ordinary matter during the clash 5.7 billion light years from Earth, the US space agency said Wednesday.

The astronomers were able to differentiate between the two substances with a technique known as gravitational lensing in which dark matter appears in blue in the image while ordinary matter, which is mostly in the form of hot gas, looks pink.

As the two clusters merged at speeds of millions of miles per hour, the hot gas in each cluster collided and slowed down, the astronomers said. The dark matter, however, did not.

The separation between the pink and blue material provides direct evidence for dark matter and supports its particles interact with each other only very weakly or not all, apart from the pull of gravity, the astronomers said.

"It is in our view an important step forward to understanding the properties of the mysterious dark matter," said Marusa Bradac, a University of California, Santa Barbara researchers who leads the team that captured the collision.

"Dark matter makes up five times more matter in the universe than ordinary matter. This study confirms that we are dealing with a very different kind of matter, unlike anything that we are made of," he said.

"And were able to study it in a very powerful collision of two clusters of galaxies."

The discovery independently confirms the findings in 2006 of another collision known as the Bullet Cluster, which also showed a clear separation between dark and ordinary matter.

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.

http://news.yahoo.com/s/afp/usspaceastronomy;_ylt=AmXBx_xOdv84NRs.p6d8RQcDW7oF

Answer 1

Dark Matter pretty much is an unknown for scientists.  It's a very loose term right now.  Meaning nobody can tell you exactly what dark matter is.  We just know, that it's not like any matter that we know of here on earth.  

Matter being mostly in liquid, solid or gas form, is anything that takes up space.  So anything you visually see consists of matter.  All these things are affected by things such as gravity.  Well we've now discovered something that we've termed "dark matter" that does not follow the same rules that normal matter does.  Such as it doesn't get affected by gravity.  We realized this by seeing things like the Bullet Collission where normal matter and something else (dark matter) ran into each other and didn't react the same.  

So what's the significance of it?  Well it takes up about 1/5th of the universe, so we'd like to know what the heck it is.

Sorry I didn't want to be like DJ above and just copy & paste the description out of WIKI

Answer 2

I would look at that information about dark matter with a jaundiced eye. For one hundred years science has told us that dark matter made up 97% of the mass of the universe, and its gravity would slow down the expansion of the universe. This never happened, and the best attempts of the scientific community failed at identifying and locating this dark matter. Now they propose that there must be a form of energy that they have called, dark energy, is responsible for this continuing expansion. There will always be some ambitious astronomer looking to make a name for himself with some new discovery. This is speculation at the best.  

Answer 3

Well, think of it this way.... everything - you, your house, the tree in your yard - consist of a lot of stuff you can't experience....  

Answer 4

In physics and cosmology, dark matter is matter that does not interact with the electromagnetic force, but whose presence can be inferred from gravitational effects on visible matter. According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter accounts for the vast majority of mass in the observable universe. The observed phenomena which imply the presence of dark matter include the rotational speeds of galaxies, orbital velocities of galaxies in clusters, gravitational lensing of background objects by galaxy clusters such as the Bullet cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies. Dark matter also plays a central role in structure formation and galaxy evolution, and has measurable effects on the anisotropy of the cosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than that which interacts with electromagnetic radiation: the remainder is called the "dark matter component."