If the Universe is full of dark matter, why can't we "see" it?

Answer 1

As others have said, it just doesn't want to come out and play. Believe about 4% of the mass/energy in the universe is normal matter, and about 23% is dark matter. Dark energy is the major player but is not related to dark matter. They have completely different effects.

Eri is probably referring to the recent "photo" of two colliding galaxies. I believe that analysis of gravitational lensing phenomena was incorporated in the image to illustrate the distribution of mass. The image indicated most of the mass in each galaxy had jumped ahead of the visible mass, which was a new way of seeing dark matter. However, lensing phenomena is still relying on gravity for detection.

Answer 2

Dark matter is just that - dark. It doesn't emit radiation in any wavelength and doesn't seem to interact with anything. We have 'observed' dark matter in galaxies by looking at the gravitational effects of the galaxy on it's stars and dust, and realizing that we're only seeing about 10% of the matter that should be there according to gravitational theory. In addition, there was recently an 'observation' made of dark matter which didn't rely on gravitational theory, which was an important confirmation.

Answer 3

Because it does not reflect or give off any light. And it tends to exist outside galaxies, so it is extremely distant. There is a lot of it, however - it is estimated at up to 96% of the universe is either dark matter or dark energy.

Answer 4

"Dark" matter is, literally, what can't be seen by current technology. When talking about the composition of the universe, stars, hydorgen clouds, planets, etc. comprise observable matter through optical and radio telescopes. "Dark" matter is presumed to be particles that interact weakly, if at all, with regular matter. Nonetheless, theory suggests that there is enough of it around to have a significant effect.