Dark matter is a hypothetical form of matter that is thought to make up approximately 85% of the matter in the universe, but it does not emit, absorb, or reflect light, making it invisible and undetectable by traditional means.

Here are some key points about dark matter:

Invisibility: Dark matter does not interact with electromagnetic radiation, such as light, and therefore cannot be seen directly with telescopes.

Gravitational Effects: Dark matter is inferred to exist by its gravitational effects on visible matter, radiation, and the large-scale structure of the universe. It does not emit light, but it exerts a gravitational pull on visible matter, affecting the motion of galaxies and galaxy clusters.

Theoretical Particles: Various theoretical particles have been proposed as potential candidates for dark matter, such as Weakly Interacting Massive Particles (WIMPs) and Axions. However, as of my last update in September 2021, none of these particles have been detected experimentally.

Cosmological Significance: Dark matter plays a crucial role in the formation and structure of the universe. It is believed to have been instrumental in the formation of galaxies and galaxy clusters by providing the gravitational scaffolding for ordinary matter to accumulate.

Research and Detection: Scientists are actively researching dark matter using a variety of methods, including direct and indirect detection experiments, particle accelerators, and astronomical observations.

The nature of dark matter remains one of the most significant unsolved mysteries in astrophysics and cosmology. Its presence is inferred from its gravitational effects, but its exact composition and properties are still subjects of intense scientific investigation and debate.