Finding Dark Matter

Explanation: Where is dark matter ? Galaxies rotate and move in clusters as if a tremendous amount of unseen matter is present. But does dark matter exist in the greater universe too -- and if so, where? The answer can be found by comparing the distribution of galaxies observed with numerical simulations . This comparison became much more accurate recently when over 100,000 galaxy observations from the 2-Degree Field Galactic Redshift Survey were used. In the above frame from a computer simulation of our universe , a 300 million light-year slice shows dark matter in gray and galaxies as colored circles. The red box indicates the location of a rich cluster of galaxies , while the green box shows a more typical cross-section of our universe . Analyses indicate that the immense gravity of the pervasive dark matter pulls normal matter to it, so that light matter and dark matter actually cluster together.