Effective Age of Universe: A New Concept Resolving Cosmological Tensions

We introduce the Effective Age of the Universe (EAoU), a relativistically consistent reformulation of cosmic time that reinterprets the expansion history from the perspective of a present-day observer. Unlike the conventional comoving-frame age of the universe (AoU), EAoU replaces the (1+z)−1 scaling in the cosmic age integral with the accumulated proper time along the observer’s worldline, yielding extended temporal frameworks of up to ~45 Gyr depending on the cosmological parameters. Building on this temporal redefinition, we generalize the FLRW metric by introducing a redshift-dependent temporal component, g00=−f(z)2, and derive an observer-centric effective Hubble parameter, Heff(z)=H(z)/(1+z), which links cosmic chronology, expansion dynamics, and metric geometry in a unified relativistic framework. This combined approach not only extends the effective time available for early structure formation—alleviating high-redshift anomalies such as the unexpectedly rapid emergence of massive galaxies, chemically enriched systems, and ∼109 M⊙ SMBHs—but also moderates early-universe contraction relative to standard ΛCDM, offering a natural pathway toward resolving the Hubble tension without invoking new physics.