Dark matter is a hypothetical form of matter that does not interact with light or other electromagnetic radiation, making it invisible and difficult to detect directly. It is called "dark" because it does not emit, absorb, or reflect light, making it invisible to conventional telescopes and other astronomical instruments.
Despite its invisibility, the existence of dark matter is inferred from its gravitational effects on visible matter and the large-scale structure of the universe. Various astronomical observations and measurements, including the rotation curves of galaxies, the motions of galaxies within galaxy clusters, and the gravitational lensing of light, suggest the presence of additional mass that cannot be accounted for by visible matter, such as stars, gas, and dust.
Dark matter is estimated to constitute about 85% of the total matter content of the universe, making it significantly more abundant than visible matter. However, its exact nature and composition remain unknown. Several theoretical models have been proposed to explain dark matter, including the idea that it consists of as-yet-undiscovered subatomic particles. These particles, collectively referred to as Weakly Interacting Massive Particles (WIMPs), are hypothesized to interact only weakly with ordinary matter and possess mass.
Efforts to directly detect dark matter particles are underway using a variety of experimental techniques, such as underground detectors and particle accelerators. Additionally, scientists are studying the cosmic microwave background radiation, galaxy formation and evolution, and other astrophysical phenomena to gain further insights into the properties and behavior of dark matter.
Understanding the nature of dark matter is a crucial puzzle in modern astrophysics and cosmology because it plays a fundamental role in the structure and evolution of the universe. Its gravitational effects influence the formation of galaxies, galaxy clusters, and the large-scale distribution of matter. Resolving the mystery of dark matter is a subject of ongoing scientific research and exploration.