Two meanings of “reversible” here: ‘can be run in reverse’ vs ‘from looking at the current state we can determine all prior states’. I believe merkle was using the second meaning and you’re arguing against the first.
The 2nd law doesn’t argue against the first meaning, that microscopic events look the same in both time directions. That’s true. The reason that doesn’t generalize to macroscopic events (i.e. the 2nd law arguing against the second meaning) is illustrated by diffusion. Suppose you have a sufficiently hot interface between two pure metal slabs- there’s lots of vacancies and the atoms are dancing around in the crystal structure. At the interface, you might have a vacancy surrounded by three atoms of metal A and two atoms of metal B. Each atom is roughly equally likely to hop to that vacancy, but it’s 60-40 that an atom of metal A will move there instead of an atom of metal B. The result is that a sharp interface becomes a diffuse interface until eventually you have one slab of both A and B, with local distributions of A and B in thermal equilibrium with each other. Once this has happened, you won’t be able to tell which side of the slab was originally A and which side was B.
What makes cryonics work is that it’s very cold, which means that diffusion happens on massive timescales. The main question I have about information-theoretic death is how long someone’s brain has to be dead at room temperature for information to be permanently lost. The long-term damage of even a few minutes of anoxic deprivation before standard revival is massive. What information you need from a frozen dead cell to make a functional live cell isn’t well known- if it’s just the knowledge that neuron A is connected to neuron B, we’re in good shape. If it’s what the local ion distributions were in the cellular soup and you let them diffuse for thirty minutes, it might be impossible.
Well, there’s also acoustic fracture events, which Alcor cops to in their FAQ but sort of downplays the significance of. Even though vitrification prevents ice crystal formation, fractures occur at just a few degrees below the glass transition. Feeling lucky about the odds of checking and correcting the damage to 10^15 unmapped connections?
Well, it’s not like the Second Law of Thermodynamics is a law of physics. It’d be in the title or something.
Two meanings of “reversible” here: ‘can be run in reverse’ vs ‘from looking at the current state we can determine all prior states’. I believe merkle was using the second meaning and you’re arguing against the first.
Though I don’t know very much about this.
The 2nd law doesn’t argue against the first meaning, that microscopic events look the same in both time directions. That’s true. The reason that doesn’t generalize to macroscopic events (i.e. the 2nd law arguing against the second meaning) is illustrated by diffusion. Suppose you have a sufficiently hot interface between two pure metal slabs- there’s lots of vacancies and the atoms are dancing around in the crystal structure. At the interface, you might have a vacancy surrounded by three atoms of metal A and two atoms of metal B. Each atom is roughly equally likely to hop to that vacancy, but it’s 60-40 that an atom of metal A will move there instead of an atom of metal B. The result is that a sharp interface becomes a diffuse interface until eventually you have one slab of both A and B, with local distributions of A and B in thermal equilibrium with each other. Once this has happened, you won’t be able to tell which side of the slab was originally A and which side was B.
What makes cryonics work is that it’s very cold, which means that diffusion happens on massive timescales. The main question I have about information-theoretic death is how long someone’s brain has to be dead at room temperature for information to be permanently lost. The long-term damage of even a few minutes of anoxic deprivation before standard revival is massive. What information you need from a frozen dead cell to make a functional live cell isn’t well known- if it’s just the knowledge that neuron A is connected to neuron B, we’re in good shape. If it’s what the local ion distributions were in the cellular soup and you let them diffuse for thirty minutes, it might be impossible.
Well, there’s also acoustic fracture events, which Alcor cops to in their FAQ but sort of downplays the significance of. Even though vitrification prevents ice crystal formation, fractures occur at just a few degrees below the glass transition. Feeling lucky about the odds of checking and correcting the damage to 10^15 unmapped connections?