Using velocity-induced acoustic oscillations as a standard ruler at cosmic dawn
(PHYSorg.com Physics)

Our current understanding of physics suggests that there are two main types of matter in the universe known as dark and baryonic matter. Dark matter is made up of material that scientists cannot directly observe, as it does not emit light or energy. On the other hand, baryonic matter is made up of normal atomic matter, including protons, neutrons and electrons.