The Second Law of Thermodynamics is a beast. As a PhD student I was given from time to time letters from people who claimed that they invented perpetual motion machine (University was obliged to provide answers for letters and obviously all the effort was thrown on poor PhD candidates).<p>Some of those invention were breaking energy conservation principle - those were easy. But there were some really ingenious ideas how to construct perpetual motion machine that was breaking II Law of Thermodynamics in a rather tricky way. Proving incorrectness was a nightmare sometimes.<p>Funny times!
There's an awesome introductory book on information theory which in one chapter resolves Maxwell's demon. The argument is that the energy needed to reliably send a single bit of information (which is needed for making the detector talk to the trap door) depends on the temperature of the fluid (because you have to overcome background noise), and it turns out the minimum energy needed for this communication is exactly equal to the amount that can be recovered from separating out a molecule.<p>If my understanding is correct (admittedly a big if), it seems the same problem applies to gambling. The energy it takes to communicate whether a gamble has paid off is at least as big as what can be recovered from the gamble.<p>The book is "An Introduction to Information Theory" by John R Pierce, and it's the most I've ever learned from a $10 paperback.
It's amazing that we're at a point where the next step after "I figured out an interesting variation of Maxwell's Demon" is to actually build the demon and try it out.
I've wondered for ages if it might be possible to transfer energy as information.<p>Consider a hypothetical setup in which two identical (possibly entangled) systems are run. On the sending side the system is observed and additional energy is spent in computation to compute interventions that would have (but did not) result in free energy. These interventions are then sent to the receiving side where the energy spent in computation on the sending side is partially recovered by actually performing those interventions and recovering free energy.<p>If something like this or at least loosely analogous to it were possible then it would be possible to do something like put up a Dyson swarm in a close solar orbit around the sun and transmit back the energy not as dangerous and difficult to receive microwave beams but as data feeds containing an endless stream of "cheat codes" to obtain apparent (but not really) free energy at the receiving end.<p>Energy is conserved because a given cheat code can only be used once to intervene where the sender determined an intervention <i>would</i> have worked. More energy must be spent at the sending side than is obtained at the receiving side.<p>Given that there are environments like close solar orbit where energy is stupidly abundant, it could work very well even if the efficiency of transfer were terrible. Even if you only got say 1% of sent energy, a small-ish Dyson swarm in an orbit between the sun and Mercury could easily power the Earth, a Mars settlement, and a few hundred spacecraft with ion thrusters.
The resolution of the original "Paradox" of Maxwell's demon is that the demon is unable to perform the measurements required. The fallacy was that the measurements could be "free".<p>Isn't this the same thing? If you measure your succcess and choose to stop, you expend energy in order to measure whether you have succeeded. If you measure after each particle, you must do lots of measurements for very little gain. If you measure rarely, you can gain a lot of energy but your expected gain is low because the particles will average out?
Isn’t this the difference between N=1 and N=1000? If you run an experiment once, you could get lucky and by constraining the timeframe, you prevent the law of averages from catching up to you.<p>However, try sufficient number of times or for sufficiently long, and you will face gambler’s ruin.
This seems like a good intersection between information & physics. What is the fundamental limit of efficiency in measuring/mutating the state of the system, assuming nearly-ideal transducers and computation?
I'm not sure this adds much to the original thought experiment. Correct me if I'm wrong, but the idea behind Maxwell's Demon was to illustrate the notion of adding information to the system to prevent/slow entropy (information being the decision to swing the trap door one way or the other). This article just seems to describe a physical device that sort of approaches that.
If I'm understanding this right, this version of Maxwell's Demon has the demon wait for random fluctuations between the chambers, and then close the gate when there's a gradient.<p>So dumb question then, doesn't this have the same problem with the original, that you have to spend negentropy to measure one side and know if it's higher potential than the other?
‘ In general, the demon sets some threshold of performance (wins or losses) over a given time period that will tell it whether or not to stop. There’s no unique best gambling strategy, but some are better than others. ’<p>Can someone explain this in a simple way?
What Is the Field of Thermodynamics?
----------<p>Nature has no internal mind. Entropy and relativity and space time are as mystical as a bag of potatoes falling on the floor at the grocery store. Thermodynamics, why we study it and why it's important, is as best of a model one can get which strips out the internal mind from nature. No momentum. No charge. Just internal probability and the external environmental constraints needed to maintain it.<p>What Are Particles?
----------<p>Not what most people think. Can heat be transferred to or from the object in question? That's one part. Is there a capacity for heat, or a latency between heat transfer and external environment effects? Then you have a particle. So it's not little grains of sand or little specks of dust. Anything that absorbs energy without moving the thermometer or multimeter.<p>What Is the Second Law?
----------<p>If there is no conductive surface or convective medium, such as the Sun warming the Earth, what is the medium of heat transfer? Relativity, speeding up and slowing down internal clocks, works just the same for heat transfer. So does uncertainty, nature's built in tolerance of measurement. Their amount is much more than any cloud of dust in the air or specks of pollen in a slide. They have a long time to go before reaching equilibrium. The insight is the Second Law is not some mystical holistic property. It's a bath of internal states working themselves out.<p>Why Is Explaining This Important?
----------<p>Entropy, uncertainty, cosmic scales, tend to cower people's ambition. It should send us the other way. Go for coherent control and pair production. Think of applications where the Earth is enveloped in a matter wave, and the medical treatments we could have down to the quantum biological level of mitosis.<p>Or if we had control of fusion of the Sun. That core is orbiting a black hole. We make it easier for particles to pop in and out of existence on the surface of the black hole, than it is for them to complete an entire orbit. That's a microwave, ready to melt any incoming asteroid, and will likely be humanity's first gravity application, giving a little black hole-ness to our Sun itself!<p>Part of me thinks humans, at the very high levels of power and state secrets, have been doing this for decades, if not for over a century.<p>Horrifying!!!