Cyclic Variability as a Habitability Metric: Ranking Exoplanets by Environmental Oscillation Density

Current habitability metrics for exoplanets focus primarily on equilibrium conditions:surface temperature compatible with liquid water, stellar flux within habitable zoneboundaries, and planetary radius suggestive of rocky composition. We propose acomplementary metric based on cyclic variability — the number and magnitude ofperiodic environmental oscillations a planet experiences. We argue that life requiresnot static equilibrium but dynamic oscillation between states, as demonstrated byEarth’s nested hierarchy of cycles (diurnal, tidal, seasonal, orbital). We compute aCyclic Variability Score (CVS) for 1,179 confirmed exoplanets using NASA ExoplanetArchive data, incorporating orbital eccentricity, period, equilibrium temperature, andplanetary radius. We rank candidates and compare with existing habitability indices.Water’s anomalous physical properties are reinterpreted as maximal phase-transitiondensity within the biologically relevant temperature range, providing a physical basisfor the water requirement in astrobiology. Our top candidates include Kepler-69 c(CVS=0.71), HD 191939 g (0.68), and the nearby Teegarden’s Star b (0.54, 3.8 pc).