Is your entropy constant or does it change with age? - Part I

Your entropy is not constant—it steadily increases over your lifetime.

Entropy

Pablo González-Trejo, Untitled, Oil on canvas, 150 x 209 cm, 2022

In physics, entropy measures molecular disorder and unavailable energy; in biology and information theory, it measures noise, decay, and the gradual corruption of vital biological code. While living organisms survive by actively fighting entropy, aging marks the point where entropy gradually wins.

The Living Paradox: How You Defy Physics Every Day

The Second Law of Thermodynamics dictates that the universe drifts toward disorder. Left alone, structures break down, heat dissipates, and chaos spreads.

Yet an embryo transforms into a human composed of roughly 37 trillion cooperating cells. Why don't living things immediately dissolve into thermal soup?

In 1944, physicist Erwin Schrödinger answered this in What is Life?—organisms are open thermodynamic systems. You do not violate the laws of physics; you cheat them locally by consuming negative entropy ("negentropy"). You take in low-entropy inputs (food, clean water, structured nutrients, oxygen), extract chemical energy to repair and maintain your tissues, and export high-entropy waste (metabolic heat, carbon dioxide, urea) into the environment.

As long as your cellular repair engines run faster than environmental wear and tear, you maintain low internal entropy.

Why Entropy Rises as You Age: The Four Cellular Leaks

Aging occurs because life’s repair mechanisms are neither 100% efficient nor thermodynamically free. Every reaction creates microscopic thermodynamic friction, accumulating molecular noise across four key biological layers:

1. Thermodynamic Entropy: The Engine Degrades

Mitochondria generate ATP, the chemical currency powering your cells. However, electron transport is inherently leaky. A small percentage of oxygen escapes as Reactive Oxygen Species (ROS)—chemically aggressive free radicals. Over decades, these radicals oxidise surrounding lipids, enzymes, and mitochondrial membranes. As mitochondria suffer structural damage, their energy output drops while their waste heat and leakiness rise, elevating physical entropy inside the cell.

2. Informational Entropy: DNA and Epigenetic Drift

Entropy also applies to information (Shannon entropy). Every day, cellular DNA suffers tens of thousands of molecular lesions from UV light, metabolic stress, and replication errors.

Even more susceptible is your epigenome—the chemical software of methyl groups and histone marks that tells a neuron to act like a brain cell and a hepatocyte like a liver cell. As cells age, repair enzymes get diverted to fix broken DNA strands, losing their place when they return. Epigenetic markers steadily scramble. This "epigenetic noise" blurs cell identities—a brain cell subtly forgets its exact instructions, increasing informational entropy.

3. Proteostatic Entropy: The Molecular Junkyard

Proteins must fold into exact 3D shapes to function. Chaperone proteins and the proteasome act as quality-control units, refolding or recycling tangled peptides. With age, the energy required to sustain this proteostasis declines. Misfolded proteins aggregate into insoluble clumps (such as amyloid-beta and tau in the brain), transforming an ordered cellular interior into a disordered junkyard.

4. Cellular Senescence: The Spillover

Eventually, severely disordered cells enter senescence—they permanently stop dividing but refuse to die. Instead, they secrete a toxic, pro-inflammatory chemical mix (the SASP) that damages surrounding healthy tissue. Local entropy spills into systemic entropy.

Can We Halt the Clock?

You cannot freeze biological entropy, but its accumulation rate is malleable. Caloric modulation, exercise, and deep sleep stimulate autophagy (cellular house-cleaning) and clean out damaged organelles, keeping thermodynamic chaos in check. Meanwhile, emerging longevity science focuses on partial cellular reprogramming to reboot scrambled epigenetic software back to a low-entropy state.

Until then, every heartbeat, breath, and meal remains a direct thermodynamic exchange: burning energy to keep order alive against an encroaching tide of cosmic disorder.