Dark matter is one of the most elusive and mysterious components of the universe. Though it cannot be directly observed through traditional means such as light, it is believed to make up about 27% of the universe's total mass and energy content. This strange substance does not emit, absorb, or reflect light, making it invisible to our telescopes and detectors. Its existence is inferred primarily through its gravitational effects on visible matter, such as galaxies and galaxy clusters. Without dark matter, the movement of galaxies would not make sense based on the gravitational pull of visible matter alone.
The concept of dark matter was first proposed in the early 20th century. In 1933, Swiss astronomer Fritz Zwicky observed that the galaxies within the Coma galaxy cluster were moving faster than expected based on the visible matter alone. He suggested that there must be some unseen mass, which he called "dark matter," providing the additional gravitational pull needed to keep the galaxies from flying apart. Since then, astronomers have found similar evidence in other galaxy clusters, and the hypothesis of dark matter has become a cornerstone of modern cosmology.
Despite the compelling evidence for dark matter, its exact nature remains unknown. Various theories have been proposed, with the most widely accepted one suggesting that dark matter consists of weakly interacting massive particles, or WIMPs. These hypothetical particles would interact through gravity and possibly the weak nuclear force, but not through electromagnetic forces, which would explain why they do not emit light. However, despite decades of searching, no direct detection of WIMPs has been made. This has led to the consideration of alternative explanations, such as axions, sterile neutrinos, and other exotic particles.
