Published online by Cambridge University Press: 29 November 2010
The flow of time can be conceptualized either as a cycle or an arrow. We offer a combined view: a helix. Chronological age (geophysical time reference) is not necessarily identical to biological age (internal time reference), and aging does not necessarily imply senescence. A new scheme of senescence, based on homeodynamics (nonlinear mechanics and nonequilibrium thermodynamics), is introduced as a plausible physical basis for understanding senescence. We propose that energy throughput, initially constructive of forms and functions, becomes destructive once most of the available degrees of freedom have been “frozen out” by the construction. Senescence becomes manifested at that point.
Le cours du temps peut être conceptualisé selon un modèle cyclique ou linéaire. Nous présentons une perspective combinant ces deux idées, soit un modèle spiral. L'âge chronologique (référence de temps géophysique) n'est pas nécessairement identique à l'âge biologique (référence de temps interne), et le vieillissement ne suggère pas nécessairement la sénescence. Un nouveau schéma de sénescence, fondé sur l'homéodynamique (mécanique non linéaire et thermodynamique de non équilibre), est présenté comme un fondement physique plausible servant à comprendre la sénescence. Nous proposons que la production d'énergie, matériaux initial pour la construction des formes et des fonctions, devient défavorable lorsque la majorité des degrés de liberté ont été «immobilisés» par la construction. C'est à ce moment que la sénescence se manifeste.
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