Dark matter is and has been an elusive topic in Astronomy and Physics for the last seven decades. It has gravity but does not interact in any other usual way with the "normal" matter which composes the gases, stars and people.
Dark matter has always been evidenced indirectly, as many scientists and their calculations point to the fact that there is not enough normal matter in the galaxies to justify their gravity. It seems as if dark matter is composed of a specially elusive particle that interacts with normal matter only …