From Structure Formation to Accelerating Expansion: The Impact of Dark Matter and Dark Energy on the Universe’s Ultimate End

Modern cosmology's central challenge lies in elucidating the nature of dark matter (27%) and dark energy (68%), which collectively constitute 95% of the universe's mass-energy content. Dark matter's gravitational scaffolding for cosmic structure formation is supported by four empirical pillars: anomalous galactic rotation curves, gravitational lensing mass discrepancies (e.g., Bullet Cluster), CMB angular power spectrum measurements (Planck data), and large-scale structure simulations validated by SDSS observations of the cosmic web. Dark energy, driving accelerated expansion as a repulsive gravitational source, is inferred from Type Ia supernova luminosity-distance anomalies (z≈1.7), CMB flatness constraints requiring dark energy dominance, and baryon acoustic oscillation scale compressions (BOSS: 0.8% anisotropy). The ΛCDM model, integrating these findings, faces three unresolved paradoxes: a 120-order-of-magnitude mismatch between quantum vacuum energy predictions and observations; ambiguous dark matter particle properties (no direct detection in XENONnT); and debates over dark energy equation-of-state evolution (Quintessence models challenged by DES). Future probes via LSST (Vera C. Rubin Observatory), Euclid satellite, and deep underground detectors aim to identify non-gravitational dark sector couplings, potentially overturning the ΛCDM paradigm and advancing new physics to resolve cosmic origins, evolution, and ultimate fate.