Information theory solves entropy problem (Introduction)

by David Turell @, Friday, April 23, 2021, 20:27 (177 days ago) @ David Turell

It all started with Maxwell's demon:

https://www.quantamagazine.org/how-maxwells-demon-continues-to-startle-scientists-20210...

"...the inexorable rise in entropy, or disorder, as quantified by the second law of thermodynamics, takes on an almost mathematical certainty. So of course physicists are constantly trying to break it.

"One almost did. A thought experiment devised by the Scottish physicist James Clerk Maxwell in 1867 stumped scientists for 115 years. And even after a solution was found, physicists have continued to use “Maxwell’s demon” to push the laws of the universe to their limits.

***

"What if, suggested Maxwell, a tiny imaginary creature — a demon, as it was later called — sat at the door. Every time it saw a fast-moving particle approaching from the left-hand side, it opened the door and let it into the right-hand compartment. And every time a slow-moving particle approached from the right, the demon let it into the left-hand compartment.

"After a while, the left-hand compartment would be full of slow, cold particles, and the right-hand compartment would grow hot. This isolated system would seem to grow more orderly, not less, because two distinguishable compartments have more order than two identical compartments. Maxwell had created a system that appeared to defy the rise of entropy, and thus the laws of the universe.

***

"In 1982, the American physicist Charles Bennett put the pieces of the puzzle together. He realized that Maxwell’s demon was at core an information-processing machine: It needed to record and store information about individual particles in order to decide when to open and close the door. Periodically it would need to erase this information. According to Landauer’s erasure principle, the rise in entropy from the erasure would more than compensate for the decrease in entropy caused by the sorting of the particles. “You need to pay,” said Gonzalo Manzano, a physicist at the Institute for Quantum Optics and Quantum Information in Vienna. The demon’s need to make room for more information inexorably led to a net increase in disorder.

"Then in the 21st century, with the thought experiment solved, the real experiments began. “The most important development is we can now realize Maxwell’s demon in laboratories,” said Sagawa.

***

"Others wondered if there might be less demanding ways to use information to extract useful work from a similar system. And research published in February in Physical Review Letters seems to have found a way to do so. The work makes the demon into a gambler.

"The team, led by Manzano, wondered if there was a way to implement something like Maxwell’s demon but without the information requirements. They imagined a two-compartment system with a door, as before. But in this case, the door would open and close on its own. Sometimes particles would randomly separate themselves into hotter and colder compartments. The demon could only watch this process and decide when to turn the system off. In theory this process could create a small temperature imbalance, and therefore a useful heat engine, if the demon was smart about when to end the experiment and lock any temperature imbalance in place, much as a smart gambler on a hot streak knows when to leave the table. “You can either play all night on the roulette table, or you can stop if you win $100,” said Édgar Roldán, a physicist at the International Center for Theoretical Physics in Italy who was a co-author on the study. “We’re saying we don’t need such a complicated device as Maxwell’s demon to extract work in the second law. We can be more relaxed.” The researchers then implemented such a gambling demon in a nanoelectronic device, to show it was possible."

Comment: Just to show information is everywhere. In our reality information is required, and can be descriptive or instructive. An originating mind is required.


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