We have come the call the matter that we can see, “normal matter.”  Physicists call this baryonic matter.

The other type of matter, dark matter, is called dark largely since we don’t know what it is (and are in the dark about it), but also because it does not react electromagnetically (it doesn’t give off or absorb light and it neither attracts nor repels normal matter.

We have no way to directly see dark matter, we cannot make it interact in experiments, and we cannot touch it (even with our most sophisticated detection devices), although we believe dark matter particles could be zipping through us all the time. The existence of dark matter is largely implicit, through the behavior of galaxies and gravitational lensing.  Yet, according to the math, there must be more dark matter than there is baryonic matter, by a factor of five.

Have a listen at HitRecord.org