3 ms·

A motor that doesn't require energy violates the second law by definition; a selectively-enforced barrier that lets hot particles through but not cold particles

A motor that doesn't require energy violates the second law by definition; a selectively-enforced barrier that lets hot particles through but not cold particles didn't obviously provably cost energy. If that sounds like a cop out, remember that the Demon is a metaphor that's supposed to represent an as-yet-undiscovered technology. Like, instead of a literal massless door that opens and closes, something like, "What if we discovered a clever way of designing a little gap between two chambers and ionizing the particles such that only hot ones go through."

thaumasiotes 5y ago
> a selectively-enforced barrier that lets hot particles through but not cold particles didn't obviously provably cost energy. I think you're leaving something out of your description. We have passive selective barriers that will admit low-energy particles while reflecting high-energy particles. (Cotton, say, will reflect visible light while being transparent to infrared light.) So what do you get by hanging a sheet between two rooms? Nothing. I think Maxwell's Demon will only let hot particles pass through in one direction, but that's nothing new either; we have one-way mirrors.
- Dylan16807 5y ago
  > I think Maxwell's Demon will only let hot particles pass through in one direction, but that's nothing new either; we have one-way mirrors. We don't, actually. We have semi-transparent mirrors that allow a small fraction of the light through, and they appear "one-way" only when one side is vastly brighter than the other.
- jayd16 5y ago
  If one way mirrors worked like that we wouldn't need heat pumps. We do because they don't work like that.
zackees 5y ago
Replace “hot particles” with “moving electrons” on a sheet of graphemes and replace “door” with “diode” and the experiment has already been proven in reality to generate charge and extract work out of the environment.

thaumasiotes 5y ago

> a selectively-enforced barrier that lets hot particles through but not cold particles didn't obviously provably cost energy. I think you're leaving something out of your description. We have passive selective barriers that will admit low-energy particles while reflecting high-energy particles. (Cotton, say, will reflect visible light while being transparent to infrared light.) So what do you get by hanging a sheet between two rooms? Nothing. I think Maxwell's Demon will only let hot particles pass through in one direction, but that's nothing new either; we have one-way mirrors.

Dylan16807 5y ago
> I think Maxwell's Demon will only let hot particles pass through in one direction, but that's nothing new either; we have one-way mirrors. We don't, actually. We have semi-transparent mirrors that allow a small fraction of the light through, and they appear "one-way" only when one side is vastly brighter than the other.
jayd16 5y ago
If one way mirrors worked like that we wouldn't need heat pumps. We do because they don't work like that.

zackees 5y ago

Replace “hot particles” with “moving electrons” on a sheet of graphemes and replace “door” with “diode” and the experiment has already been proven in reality to generate charge and extract work out of the environment.