Dark matter has not been directly observed or detected by astronomers or scientists so far. Its existence is inferred through its gravitational effects on visible matter and structures in the universe.
The evidence for the existence of dark matter primarily comes from observations of the rotational velocities of galaxies and galaxy clusters. According to the laws of gravity, the visible matter in these systems is not sufficient to explain the observed velocities. There must be additional mass present that does not emit or interact with light, hence the term "dark matter." The gravitational effects of this unseen matter are necessary to explain the observed motions and stability of galaxies and galaxy clusters.
The first indications of dark matter were observed by Swiss astronomer Fritz Zwicky in the 1930s. He studied the motion of galaxies within the Coma Cluster and found that their velocities were much higher than expected based on the visible mass in the cluster. Zwicky proposed the existence of "dunkle Materie," or dark matter, to account for the discrepancy.
Since Zwicky's observations, numerous other studies have provided further evidence for dark matter. These include measurements of the cosmic microwave background radiation, large-scale structure formation in the universe, gravitational lensing, and the distribution of matter in galaxy clusters, among others. These observations collectively suggest that dark matter makes up a significant portion of the total matter in the universe, outweighing visible matter by about five times.
Despite its prevalence in the universe, the exact nature of dark matter remains unknown, and efforts are ongoing to directly detect and identify its constituents. Various experiments, such as those conducted in underground laboratories, particle colliders, and space-based telescopes, are actively searching for evidence of dark matter particles or interactions. However, to date, no direct detection of dark matter has been confirmed.