The existence of dark matter is indeed a prominent topic in astrophysics and cosmology. Dark matter is a hypothetical form of matter that does not interact with light or other electromagnetic radiation, which is why it remains invisible or "dark" to our current detection methods. Its presence is inferred through its gravitational effects on visible matter and the large-scale structure of the universe.
The reason scientists propose the existence of dark matter is to account for the gravitational effects observed in galaxies and galaxy clusters that cannot be explained by the visible matter alone. The gravitational pull from visible matter is not sufficient to explain the observed motion of stars and galaxies. Dark matter is thought to make up a significant portion of the total mass in the universe and is considered responsible for the formation and evolution of large-scale cosmic structures.
While neutrinos are subatomic particles with extremely low mass, they are not considered a significant component of dark matter. Neutrinos have been observed and studied, and although they have some intriguing properties, their overall contribution to the total mass of the universe is relatively small.
The exact nature of dark matter remains unknown, and its identification and direct detection are ongoing areas of scientific research. Various candidate particles, such as weakly interacting massive particles (WIMPs) and axions, have been proposed, but definitive experimental evidence for the existence of dark matter is still lacking. Scientists continue to investigate and explore this fascinating aspect of our universe in the hope of gaining a deeper understanding of its composition and properties.