Dark Matter
Dark matter is a hypothetical form of matter that is thought to account for approximately 85% of the matter in the universe and about 27% of its total mass–energy density. Its presence is inferred from gravitational effects on visible matter, radiation, and the large-scale structure of the universe.
Key Properties
- Non-luminous: Does not emit, absorb, or reflect light, making it invisible to electromagnetic observations.
- Gravitational Influence: Interacts with normal matter primarily through gravity.
- Composition: Likely consists of weakly interacting massive particles (WIMPs) or axions, though the exact nature remains unknown.
Detection Methods
- Gravitational Lensing: Observing how dark matter bends light from distant objects, revealing its distribution.
- Milky Way Rotation Curves: Analyzing the rotational velocity of stars and gas to infer mass distribution. Recent data challenges standard models, suggesting a tension between observed rotation curves and predictions from both dark matter halos and Modified Newtonian Dynamics (MOND). See Milky Way Rotation Data Challenges Dark Matter and Modified Gravity for detailed analysis of this discrepancy.
References
- Hossenfelder, S. “Headache: New Milky Way Data Just Defies Explanation.” Milky Way Rotation Data Challenges Dark Matter and Modified Gravity.