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Active and passive stability - ice vs skin

Consider the self repair of an ice sheet crushed by a stick and the self repair that happens when skin repairs a cut. These are very different processes; skin is capable of dynamic self-repair, but ice is passively self-repaired.

Life has a tendency to exist in states that require constant energy input just to remain alive; repair happens continuously in response to ongoing wear and tear. In the event of a cut, the same regular maintenance occurs but perhaps at an accelerated rate.

A frozen pond, in contrast, requires no continuous energy to remain frozen. The crystal structure of the ice is sufficiently stable that it can just continue to exist as long as the temperature doesn't increase. If the structure is disrupted, water under the ice will naturally return to the surface and spontaneously freeze because of the temperature of the surroundings, self-repairing spontaneously.

The downside of the frozen pond strategy is that ice's crystal structure is highly vulnerable to changes in the environment. When it gets warm, the crystal will reliably melt and turn into water. This is static stability.

A biological system, in contrast, typically has a broader operating range, and is more resilient to environmental variation. Life is complex and constantly requires external energy to survive, but it is far more resilient.

Related: Active stability is related to non-equilibrium systems

Last edited on Feb 2024