DARK MATTER
- Definition: Dark Matter is invisible matter that does not interact with electromagnetic radiation (no absorption, reflection, or emission of light).
- Key Property: Interacts only through gravity, influencing motion of galaxies and cosmic structures.
- Nature:
- Has mass
- Occupies space
- Cannot be directly observed
- Gravitational Effect:
- Causes gravitational lensing → bends light from distant galaxies
- Helps scientists detect and map its presence
- Role in Universe:
- Acts as “invisible glue” holding galaxies and galaxy clusters together
- Essential for structure formation of the universe
- Cosmic Composition:
- Dark Matter ≈ 27% of the universe
- Ordinary matter ≈ 5%
- Scientific Status:
- Remains unidentified despite ~100 years of research
- One of the biggest unsolved problems in physics