In 1867, physicist James Clerk Maxwell did something very bad. He proposed an apparent violation of the second law of thermodynamics so fiendishly clever that other physicists have been trying to solve it ever since. His thought experiment summoned a “demon”, a tiny, intelligent being stationed in a door between two gas-filled chambers, which only allows fast particles to enter one side and slow particles to enter the other, with the end result being heat in one chamber and cold in the other. The problem is that this decreases entropy, something that, according to the second law of thermodynamics, cannot happen in an isolated system without a compensatory increase elsewhere. However, Maxwell’s demon apparently accomplishes this without doing any work. It is the symbol of indolence. Now, a new team of physicists has exacerbated the problem. By exploiting the information hidden in a physical system’s memory, researchers have shown that the pretend imp can extract more energy than a memoryless system would ever deliver. frameborder=”0″ enable=”accelerometer; autoplay; writing on clipboard; encrypted media; gyroscope; picture in picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” enablefullscreen> To be clear, Maxwell’s original paradox has long been resolved. After all, the devil’s trick is not free: information is physical, and its processing carries thermodynamic costs that preserve the second law. But the resolution revealed something fascinating. Information about a physical system can be used to extract useful work from that system. And to demonstrate this idea, physicist Clemens Bechinger of The University of Konstanz in Germany and colleagues built a real-world version of Maxwell’s demon. Here’s how it worked: The researchers used a laser to trap a microscopic glass bead in a liquid. change the laser trap to take advantage of its movements, extracting a little energy in the process. This is the basic principle of an information engine: using knowledge about a system to turn a random movement into useful work. But there is a problem. of spaghetti-shaped molecules called micelles that form a microscopic network whose movements the researchers could not directly observe. Instead of simply measuring the position of the bead once, they measured it twice, with a carefully timed interval between observations. If the measurements were taken too close together, they revealed little about the hidden dynamics of the liquid. interval of about a second. This allowed them to time their adjustments to the laser trap more effectively, extracting energy that would otherwise have remained inaccessible. Under certain conditions, this strategy allowed the researchers to extract up to three times more work than the theoretical limit for an equivalent system without the hidden micellar memory. et al., Nat. Phys., 2026) If you need a mental image, imagine a meatball held in place in a vat of invisible spaghetti soup. The investigation is like watching the meatball move twice to figure out what the spaghetti is doing and then using that information to move your laser trap in a way that extracts additional energy from the hidden dynamics of the soup. tries to give Maxwell’s demon a new physics. Well, at least for now, it’s mainly the latter. The researchers have not built a small machine that can perform a useful task, but have demonstrated a new way of extracting energy from a microscopic system, and in the process have advanced our understanding of what information engines can achieve, suggesting they could be exploited as an additional source of useful energy. “Our results establish environmental memory as an experimentally accessible thermodynamic resource,” the researchers write. Physics. This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we’re proud of our process, we’re human. If you spot an error, please let us know.
