Here's why:
* Undetectable by light: Dark matter doesn't interact with light in any way we can observe. This means it doesn't emit, absorb, or reflect light, making it invisible to telescopes.
* Gravitational effects: We know dark matter exists due to its gravitational influence on visible matter. Astronomers observe galaxies rotating faster than they should based on the visible matter alone, and gravitational lensing suggests the presence of unseen mass.
* Composition unknown: The exact nature of dark matter is still a mystery. There are various theoretical candidates, such as weakly interacting massive particles (WIMPs) or axions, but none have been definitively detected.
The existence of dark matter is a major area of research in cosmology and astrophysics. Its discovery would revolutionize our understanding of the universe.
