The cosmological constant Λ, introduced by Einstein and later reinterpreted as the energy density of the quantum vacuum, is conventionally treated as a fixed parameter with observed value Λ ≈ 1. 089×10⁻⁵² m⁻², corresponding to an energy density of ρΛ ≈ 5. 68×10⁻²⁸ kg·m⁻³. We propose that Λ is not static but a monotonically increasing dynamical field Λ (t), anchored at its current measured value at t = t₀ (the present epoch) and evolving toward an inverse critical value Λc = 1/Λ₀. As Λ (t) → Λc, the accelerating expansion of the universe transitions to a reversal, culminating in a Big Crunch. We further argue that this terminal collapse is accompanied by time-reversal symmetry, offering a cyclic cosmological framework. We present a covariant scalar-field formulation of Λ (t), derive the modified Friedmann equations, identify observational signatures, and discuss consistency with current Type Ia supernova and CMB data.
kritagya Joshi (Mon,) studied this question.