In this fourth part of “Thermodynamics of Life”, Prof. Marc Henry, Emeritus Professor of Chemistry at the University of Strasbourg, joins Dr. Klaus Schustereder for a brilliant and often humorous deep dive into one of science’s most misused words—energy—and into the concept that quietly governs the universe: entropy.

With clarity and wit, Henry unpacks the centuries-long confusion around “energy.” Politicians, engineers, and scientists talk about it constantly, yet almost no one can define it without using examples. From Aristotle’s energeia to Poincaré’s paradox, he shows how we inherited a term that can only be illustrated—mechanical, electrical, thermal, nuclear—without ever touching its essence.

Henry argues that entropy, not energy, should be the true foundation of our understanding of life and matter. Energy is vague and context-dependent, but entropy can be precisely defined: it measures how many configurations in space and motion are available to matter at a given temperature. The more possibilities a system has, the higher its entropy. From solids to liquids to gases, this single concept explains every state of matter in a way that “energy” never could.

⚙️ Key Insights

• Entropy is measurable and universal – It represents accessible configurations in space and time.

• “Energy consumption” is a myth – The first law of thermodynamics tells us energy can’t be destroyed, only transformed.

• We pay for entropy production, not energy loss – Electricity bills should really say “entropy production,” because what changes is organization, not the total amount of energy.

• Thermodynamic potentials are forms of entropy – Free energy, internal energy, and enthalpy are just ways of expressing entropy under fixed conditions (pressure, volume, or temperature).

• Historical bias against entropy – Because entropy was introduced as “energy loss,” it got a bad reputation, even though it is actually the measure of evolution, transformation, and life.

🧠 From Mechanics to Thermodynamics

Henry walks us through the evolution of science: Galileo’s telescope and Newton’s laws gave us a mechanical universe ruled by conservation of energy. Then Sadi Carnot’s steam engines, and later Rudolf Clausius and Ludwig Boltzmann, opened the door to thermodynamics and entropy. Mechanics could describe reversible motion; thermodynamics revealed that every real process produces entropy.

The industrial revolution, driven by the work of James Prescott Joule, translated everything into joules. Joule’s clever calibration between mechanical work and heat was practical—but it also blurred the difference between heat and energy, locking us into a language that still misleads physics, engineering, and medicine.

🌌 From Energy to Entropy to Life

Henry and Schustereder then broaden the lens. Why cling to an undefined concept like energy when entropy alone explains every change, from boiling water to biological evolution? Henry suggests that if science had discovered entropy first, our entire worldview—especially in biology and medicine—would be more coherent. Entropy describes how systems evolve, self-organize, and maintain order far from equilibrium.

He links entropy to cosmology, proposing that the expansion of the universe is driven by the relentless creation of entropy. Because entropy cannot be destroyed, the universe must keep expanding to “host” it. In this picture, the second law of thermodynamics is not just a technical rule—it is the law of evolution, explaining motion, time, and life’s tendency toward greater complexity. The so-called “first law” becomes a special case.

🔄 Spin, Constants, and the Status of Energy

Finally, Henry turns to fundamental constants: gravity, the speed of light, electric charge, Avogadro’s number, Boltzmann’s constant (entropy), and Planck’s constant (spin). These define the structure of reality.

Conspicuously absent is any constant for energy, which, Henry argues, shows that energy is not truly fundamental. The real pillars of the universe are entropy and spin—the measures of possible configurations and intrinsic rotation.

His closing provocation sums up the entire talk:

“If you speak of energy, you are a technician.
If you speak of entropy, you are a scientist.”