Published on July 9, 2025 2:55 PM GMT
Introduction
I recently made a post named Planet X, Lord Kelvin, and the use of Structure as Fuel. I got some very insightful engagement from AnthonyC. This follow up post also contains a thought experiment. One that does not break the second law of thermodynamics, but where it may hard, and potentially useful, to find out why it does not (at least it was hard for me).
1. The Asteroid Thought Experiment
One way to summarize the Second Law of Thermodynamics is: “You can never build a perpetual motion machine.” Or more precisely: “No process can extract usable work without, on average, increasing total entropy.” Now, consider the following:
The setup:
- An asteroid with helium atmosphere, surrounded by a somewhat distant shellCosmic microwave background at 5KInitially everything is at thermal equilibrium (5K)
The process:
- Fast helium atoms naturally escape the asteroid's gravity well (evaporative cooling)The escaped atoms drift to the outer shell with nearly zero kinetic energy (escaping gravity costs speed, exchanging kinetic for potential energy)Graphene sheets capture these slow-moving atoms near the shellThe captured gas is lowered back to the asteroid, extracting work from gravitational potential energyThe helium is released and the cycle repeats
Key observations:
- The atmosphere cools below 5K due to evaporative coolingThe CMB continuously supplies heat to the cooled atmosphereEnergy is conserved (extracted energy eventually returns as waste heat to the CMB)The system appears to generate work from a single-temperature reservoirPotential for power extraction appears to scale with setup volume and ambient temperature.If the second law is to be saved, entropy must ALSO increase proportional to volume and temperature, in a way that makes perpetual energy extraction impossible.
But how could entropy do that? It can’t be generators breaking. It can’t be losses from gas collection. Nothing fitted the required scaling demands… Nothing obvious fits.
“Does this break the second law?”
At first my mind raced. It seemed as if it did. Days passed. I plagued those around me with urgent requests for feedback. Yet, there was so many unknowns. And the growing, knowing, feeling. But what about system degradation? And then it just clicked. The second law doesn’t break, but it could be conceptually strengthened and clarified.
You will not be able to extract energy forever.
Not because nature forbids it outright. But because every clever act of energy extraction, every reconfiguration of parts, carries a hidden cost: structural degradation. Material fatigue. Rearranged molecules. Broken bonds. Material decay into outer space. You don’t just lose energy. You lose the very ability to harvest it.
That’s the real law (in a way): You may be clever, but never for free. In the end, you will lose.
As I alluded to in the beginning of this post, what I’m talking about may already be obvious to those with a deep enough insight into the mathematics behind entropy. It is not, however, to the rest of us. The rest of us may need an explanation going beyond just stating that the amount of disorder is always increasing. Something that might help us in looking for new ways to be clever.
What I propose is one conceptual formulation to rule them all. One explanation, perhaps needed to explain time itself:
"Any extraction of utility within a closed system will over time degrade the systems structural capacity to support such extraction. This degradation will, on average, cost more utility to reverse than the amount that was extracted."
By utility I mean: things like usable energy, information, or function in general. And yes, I know this is hand-wavy. Better minds than mine will need to sharpen this.
By structure I mean: “any state of order that is necessary for any particular extraction of utility”. In essence: “Total entropy will always increase”.
2. Entropy, the Arrow of Time and Cosmologic Degradation
In physics, the natural laws are time independent. They work equally well for going backwards in time as for going forwards in time. Yet, we all know, when we are watching a film in reverse. We just know.
Why?
It turns out that one, and only one, meaningful quantity always changes in a way that invariably tells us the direction of time: entropy.
This realization goes back over two hundred years. It has led thinkers, physicists and cosmologists, like Sean Carroll, to say things like:
“The fact that entropy increases defines the arrow of time.”
And:
“The fact that I remember the past and not the future can be traced to the fact that the past has lower entropy. I think I can make choices that affect the future, but that I can’t make choices that affect the past is also because of entropy.”
Can we prove this? Perhaps not. Is it a conviction many of us share? Almost certainly. A deep insight, right at the crossroads of physics, cosmology, metaphysics and philosophy.
Cosmological degradation
In my Asteroid thought example, it seemed reasonable, something scaling with volume would be needed. Temperature too. Radiation temperature, where power scales at T4 seemed plausible (since energy came flowing in through the Cosmic Microwave Background Radiation). But what kind of degradation would scale like that?
I couldn’t imagine. I thus postulated: “Any conversion of energy will degrade your capacity for energy conversion, saving the arrow of time”. In that way, perhaps it didn’t matter where the energy came from (no V or T4 necessarily needed).
I have run scores of AI Deep Research sessions on the idea by now. Hundreds or thousands of papers have been skimmed for insight by three tireless AI-systems. Finally, when asking for a search for a universal entropy sink (something linked to the experiment with a known degradation of structure on cosmological scales), the AI gave me this:
Cosmological degradation through vacuum decay and phase transitions demonstrates volume-dependent entropy production: dS/dt ∝ V·T³.
Oh, the beauty! The scaling! V·T³. That was PRECICELY the scaling I had been looking for. Entropy is counted as J/K, so if entropy degradation rate deteriorated proportional to V·T³ the power needed to “fix” it would be in the order of V·T4. Exactly the entropy sink one would naively be looking for!
The very capacity for keeping a uniform temperature degrades over time. Not as a “that could happen”, but as necessity. Dictated by the very laws of nature. Perhaps the entropy sink, most responsible for the arrow of time, if it turns out that THIS is the degradation standing between my asteroid example and perpetual motion. Standing between my asteroid and a reversal of entropy.
The eternal, imperceptible, cosmic degradation, ensuring that time will keep in its lane. No cheating allowed.
All of the above is just speculation as of now, though the matching dimensional analyses is compelling. It might be worth looking into.
3. Not Just Energy. Not Just Heat. But Structure
This insight reframes the Second Law conceptually. It’s not primarily about temperature gradients or thermal flow. Those are symptoms, not causes. The fundamental truth is deeper:
No system can repeatedly extract usable work from randomness without amplifying degradation faster than return.
Even the cleverest extraction fails in the long run. Piezoelectrics from random pressure fluctuations? Molecular traps waiting for a fast particle? Spring-loaded nano-captures? If possible, each success adds wear. Each harvest frays the machinery of future harvests. And to be clear: by machinery I mean “anything that is necessary for the extraction of energy”. Not necessarily the “engine” itself. Regardless:
This is entropy not just as disorder in temperature, but as loss of structure and functionality as well: the irreversible cost of function. Unbeknownst to me M. D. Bryant had already formulated the mathematics of such a framework, back in 2008 (the DEG-theorem mentioned in my post on Planet X).
4. Beautiful Paradoxes
Reframing the Second Law doesn’t render it obsolete. It renders it inevitable. It doesn’t say "heat engines from uniform temperature are forbidden." It says: They are allowed, but they will burn themselves away.
What was once seen as impossible now becomes possible—but only briefly. Only once. Only at a price.
Every act of turning random fluke into useful function costs you something precise, intricate, and unrepeatable.
Even if you win 9 times out of 10, if the 10th costs you more than all your gains, you will still lose.
Even if you win a googol times out of a googol and one, if the googol and first time costs you more than all your gains, you will still lose.
Entropy, in this view, is not a tax on order. It is the price of participation in a structured universe. Not a forbidding wall, but a silent tally.
And it never forgets.
Sources
Sean Carroll. The second link goes to a blog, not the actual article. The article is behind a paywall though:
https://www.preposterousuniverse.com/blog/2004/10/27/the-arrow-of-time/
https://whyevolutionistrue.com/2010/04/20/the-nyt-interviews-physicist-sean-carroll/
Sources regarding Vacuum Decay (found through AI research, the origin of dS/dt ∝ V·T³.):
Brout, R., & Spindel, Ph. (1993). Entropy Production from Vacuum Decay. arXiv:gr-qc/9310023
Lima, J. A. S., & Trodden, M. (1996). Thermodynamics of Decaying Vacuum Cosmologies. arXiv:gr-qc/9605055
Discuss
