"With this abundance, arguments stemming from our understanding of the origin of light elements in the Big Bang imply that this material cannot be made of normal matter, i.e. matter comprised of protons, neutrons and electrons, the building blocks of all atoms. If instead, it is made from a new type of elementary particle that doesn't interact with electromagnetically, dark matter would exist as a diffuse gas or particles permeating throughout galaxies, including our own. As a result, it is not just "out there," it is "in here," going through you and me, the whole earth, and the computer I type this on.
This possibility provides both a challenge and an opportunity. Without knowing the identity of dark matter, attempts to detect it directly on earth require making some educated guesses about what it might be. However, there is at least the possibility of detecting it directly! Such detection could reveal not only the nature of what makes up the dominant matter in the universe, but also could tell us something fundamental about elementary particles and forces."