Modified Newtonian Dynamics (MOND)
Modified Newtonian Dynamics (MOND) is an alternative theoretical framework proposed in 1983 by physicist Mordehai Milgrom to explain gravitational phenomena at galactic and larger scales. Rather than invoking dark matter to account for observed discrepancies between predicted and actual gravitational effects in galaxies and galaxy clusters, MOND suggests that Newton’s laws of gravitation require modification in regimes of very low acceleration, particularly those found in the outer regions of galaxies.
Core Hypothesis
MOND proposes that when accelerations fall below a critical threshold (approximately 10^-10 m/s²), gravitational forces do not follow the inverse-square law predicted by Newtonian mechanics. Instead, the theory introduces a function that modifies how gravity behaves at these extremely small accelerations. This adjustment is intended to reproduce observed rotation curves of galaxies—the pattern of orbital velocities at different distances from galactic centers—without requiring the existence of unseen dark matter.
Empirical Status
MOND has successfully explained certain galactic phenomena and has gained a persistent following within a subset of the physics community. However, it has not achieved mainstream acceptance, primarily because it faces challenges in explaining observations at cosmological scales, including the cosmic microwave background radiation and the large-scale structure of the universe. Most of the scientific community continues to favor dark matter as the explanation for gravitational anomalies, though MOND remains an active area of research and theoretical refinement.