Dark matter is a mysterious form of matter that doesn't emit, absorb, or reflect light, making it invisible to telescopes yet detectable through its gravitational influence on visible matter. Comprising approximately 85% of all matter in the Universe, dark matter outweighs ordinary matter by a factor of 5:1, fundamentally shaping cosmic structure.</p><p>The concept emerged in the 1930s when astronomer Fritz Zwicky observed that galaxy clusters moved too quickly to be held together by visible matter alone. Vera Rubin's groundbreaking work in the 1970s provided compelling evidence by measuring galaxy rotation curves—stars at galactic edges orbit much faster than predicted, requiring additional invisible mass to prevent galaxies from flying apart.</p><p>Dark matter's presence is revealed through multiple phenomena: gravitational lensing bends light around massive dark matter concentrations, creating distorted images of distant galaxies; computer simulations show that without dark matter, the cosmic web of galaxy clusters couldn't have formed; and detailed measurements of cosmic microwave background radiation confirm dark matter's critical role in early Universe structure formation.</p><p>Despite decades of research, dark matter's particle nature remains unknown. Leading candidates include weakly interacting massive particles (WIMPs) and axions, though detection efforts continue. Understanding dark matter is crucial for comprehending cosmic evolution, galaxy formation, and the Universe's ultimate fate.
Examples
**Example:** Dark matter makes up about 27% of the universe's mass-energy content. The rotation curves of spiral galaxies provide strong evidence for dark matter—outer stars orbit faster than they should based on visible matter alone.