Dark Matter and Dark Energy?

Question

I think I understand dark energy (the universe was found to be expanding even though gravity should keep it together, so there must be some unaccounted for energy, hence dark energy?), but what is dark matter?

Answer 1

Some theories postulate that dark matter is composed of weakly-interacting massive particles or (WIMPs). These particles are extremely massive but are electrically neutral, and even if if they were able to congregate together and form atoms or clouds of dark matter large enough to be macroscopic, we wouldn't be able to see them directly because the matter neither reflects nor absorbs light of any EM frequency. Dark matter is effectively "transparent" to all known means of detection except one, gravity.

Indirect proof of dark matter is seen in the nearly uniform speed at which the Milky Way Galaxy rotates as a whole. If every star, atom and speck of dust was accounted for, it still would be far less than the observed mass of the galaxy. Unknown forms of mass and energy permeating the galaxy would explain away the problem.

The verdict is still out: what is dark matter? How is it created?

Answer 2

http://en.wikipedia.org/wiki/Dark_matter

follow this link as it is a bit to difficult & lengthy to put.

But really interesting stuff.