Dark matter is a hypothetical form of matter that does not interact with light or other electromagnetic radiation, making it invisible and "dark" in the sense that it does not emit, absorb, or reflect light. Its existence is inferred from its gravitational effects on visible matter and structures in the universe.
The nature of dark matter is still not fully understood, and its exact composition remains a subject of active scientific investigation. Various theories propose different types of particles that could make up dark matter, but none have been conclusively proven.
One popular hypothesis is that dark matter consists of weakly interacting massive particles (WIMPs). WIMPs are hypothetical particles that interact very weakly with ordinary matter and are relatively heavy compared to other particles. These particles would have been created in the early universe and could account for the observed gravitational effects of dark matter.
Despite its weak interactions with ordinary matter, dark matter's gravitational influence is significant. It affects the rotation curves of galaxies, the dynamics of galaxy clusters, and the large-scale structure of the universe. Dark matter is thought to make up a substantial portion of the total mass in the universe, significantly exceeding the amount of visible matter.
While dark matter does not interact electromagnetically, it can interact through gravity. It interacts gravitationally with ordinary matter and influences the formation and evolution of structures like galaxies and galaxy clusters. However, dark matter does not participate in the electromagnetic force, strong nuclear force, or weak nuclear force, which are responsible for the interactions of known particles.
To date, direct detection experiments have been conducted to search for interactions between dark matter and ordinary matter. These experiments aim to detect the rare instances in which a dark matter particle interacts with a regular particle, producing detectable signals. However, no conclusive direct detection of dark matter has been achieved so far.
In summary, dark matter is a hypothetical form of matter that does not interact with electromagnetic radiation and remains elusive. It primarily interacts through gravity and its presence is inferred from its gravitational effects on visible matter and structures in the universe. While its exact nature is still unknown, various theories propose that it could consist of weakly interacting massive particles (WIMPs) or other yet-to-be-discovered particles.