3 ms·

> There isn't a problem. I agree. > The initially apparent problem is […] Why would that be a problem? If it’s because the second law of thermodynamics says

by kgwgk 4y ago

> There isn't a problem. I agree. > The initially apparent problem is […] Why would that be a problem? If it’s because the second law of thermodynamics says that it cannot happen spontaneously in a thermodynamical system in equilibrium why would that be applicable when we’re not considering just a system in thermodynamical equilibrium? As Maxwell wrote: “This is only one of the instances in which conclusions which we have drawn from our experience of bodies consisting of an immense number of molecules may be found not to be applicable to the more delicate observations and experiments which we may suppose made by one who can perceive and handle the individual molecules which we deal with only in large masses.”

bee_rider 4y ago
I'm not sure -- if the gate is closed, the chambers are perfectly insulated, and we aren't erasing bits from the memory of the demon, the system should be at equilibrium, right? So, I think it is not really a situation like he describes in the quote. The demon could hypothetically have whatever large amount of information storage is required, to meet his threshold for "large masses." This quote seems more compelling in cases where the statistics are known, but and we just need to have enough samples, such that the expected values, etc, show themselves.
- kgwgk 4y ago
  Opening a tiny gate to let one particular particle go through is definitely the kind of thing that Maxwell meant by "more delicate observations and experiments which we may suppose made by one who can perceive and handle the individual molecules which we deal with only in large masses". It's the very example that he was discussing, which he had described just before: "Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the swifter molecules to pass from A to B, and only the slower ones to pass from B to A." Another interesting quote of his: "Available energy is energy which we can direct into any desired channel. Dissipated energy is energy we cannot lay hold of and direct at pleasure, such as the energy of the confused agitation of molecules which we call heat. Now, confusion, like the correlative term order, is not a property of material things in themselves, but only in relation to the mind which perceives them. A memorandum-book does not, provided it is neatly written, appear confused to an illiterate person, or to the owner who understands thoroughly, but to any other person able to read it appears to be inextricably confused. Similarly the notion of dissipated energy could not occur to a being who could not turn any of the energies of nature to his own account, or to one who could trace the motion of every molecule and seize it at the right moment. It is only to a being in the intermediate stage, who can lay hold of some forms of energy while others elude his grasp, that energy appears to be passing inevitably from the available to the dissipated state."

by kgwgk 4y ago

bee_rider 4y ago

I'm not sure -- if the gate is closed, the chambers are perfectly insulated, and we aren't erasing bits from the memory of the demon, the system should be at equilibrium, right? So, I think it is not really a situation like he describes in the quote. The demon could hypothetically have whatever large amount of information storage is required, to meet his threshold for "large masses." This quote seems more compelling in cases where the statistics are known, but and we just need to have enough samples, such that the expected values, etc, show themselves.

kgwgk 4y ago
Opening a tiny gate to let one particular particle go through is definitely the kind of thing that Maxwell meant by "more delicate observations and experiments which we may suppose made by one who can perceive and handle the individual molecules which we deal with only in large masses". It's the very example that he was discussing, which he had described just before: "Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the swifter molecules to pass from A to B, and only the slower ones to pass from B to A." Another interesting quote of his: "Available energy is energy which we can direct into any desired channel. Dissipated energy is energy we cannot lay hold of and direct at pleasure, such as the energy of the confused agitation of molecules which we call heat. Now, confusion, like the correlative term order, is not a property of material things in themselves, but only in relation to the mind which perceives them. A memorandum-book does not, provided it is neatly written, appear confused to an illiterate person, or to the owner who understands thoroughly, but to any other person able to read it appears to be inextricably confused. Similarly the notion of dissipated energy could not occur to a being who could not turn any of the energies of nature to his own account, or to one who could trace the motion of every molecule and seize it at the right moment. It is only to a being in the intermediate stage, who can lay hold of some forms of energy while others elude his grasp, that energy appears to be passing inevitably from the available to the dissipated state."