Big questions: Dark matter
Carl Sagan's statement that there are "billions and billions" of stars in the cosmos gives an idea of just how much "stuff" there is in the universe. However scientists now believe that in addition to the type of matter with which we are familiar, there is another kind of matter out there. This new kind of matter is called "dark matter" and there seems to be five times as much as ordinary matter. Dark matter interacts only with gravity, therefore light simply zips right by it. Fermilab's Don Lincoln tells us why we think this seemingly-crazy idea might not be so crazy after all.
Provided by Fermilab