THE MISSING MASS PROBLEM: A REVIEW OF DARK MATTER EVIDENCE AND MODELS

Abstract

Dark matter remains one of the most compelling and unresolved problems in modern physics and cosmology. Although it does not emit, absorb, or reflect electromagnetic radiation, its presence is inferred through a wide range of astrophysical observations. This review examines the historical development, observational evidence, and current experimental efforts aimed at understanding the nature of dark matter. The earliest indication of missing mass was reported by Fritz Zwicky in studies of galaxy clusters, where the visible matter could not account for the observed gravitational effects. Later, precise measurements of galactic rotation curves by Vera Rubin provided strong evidence that galaxies contain significantly more mass than what is visible. Additional confirmation arises from gravitational lensing phenomena and detailed measurements of the cosmic microwave background radiation by missions such as the Planck Collaboration, which indicate that dark matter constitutes approximately 27% of the total energy density of the universe. This paper reviews leading dark matter candidates, including Weakly Interacting Massive Particles (WIMPs), axions, and Massive Compact Halo Objects (MACHOs), discussing their theoretical motivations and physical properties. It further surveys major detection strategies, such as direct detection experiments using ultra-sensitive underground detectors, indirect searches for annihilation products, and high-energy collider investigations at facilities like CERN. Despite decades of intensive research, no conclusive detection has yet been achieved, prompting ongoing refinement of experimental techniques and theoretical models. By synthesizing current evidence and research approaches, this review highlights both the robustness of the dark matter hypothesis and the significant challenges that remain in identifying its fundamental nature. Dark matter continues to represent a critical frontier in understanding the composition and evolution of the universe.