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> You have to separate low entropy volume from high entropy volume to do life That's what I believed too, but I have doubts now after reading another comment t

> You have to separate low entropy volume from high entropy volume to do life That's what I believed too, but I have doubts now after reading another comment that defines it as energy gradients. As far as I understand the concept, a crystal is low entropy as well. Or is it the same thing? Or the combination of the two (Use energy to keep entropy low)? > membranes are just the sane and obvious default The less sane one could be... Magnetic confinement fields I guess?

klodolph 3y ago
If you want to understand crystals thermodynamically, in terms of entropy, you should be using a more rigorous notion of entropy. When crystal formation is thermodynamically favorable, the process causes entropy to increase, not decrease. So if you have a crystal which exists in-situ, in the conditions which caused it to form, you don’t increase entropy by un-creating it.
jerf 3y ago
The main problem with crystals and solid-phase life in general is that, being solid, it tends to just sit there and be solid. It's why silicon life is nominally appealing if you just look at the periodic table, but when you look out into the real world and see what the characteristics of the compounds it actually forms look like, you see an awful lot of solids and it isn't really plausible as a basis for life. It helps to look at how biology actually works; we get these images of things like DNA copying where the next amino acid is just sitting there, all but busting in the door to be copied. It gives a very false image of how biology works. In reality it's an insane world down there with a whole bunch of the cell just jiggling around thermally all the time, and the mechanisms all work by waiting to be bashed into by the right thing. Everything is so fast and the rate of jiggling is such that it all ends up working out. But it's nothing like anything we'd design or even very easily wrap our head around. I've sometimes wondered if we were somehow otherwise the same, but not biological, how long it would take for us to ever invent biology. We are certainly nowhere near it now. Crystals and solid-phase in general doesn't have an obvious route to chemistry occurring anything like the way it does in biology, and indeed, it doesn't have an obvious route to chemistry occurring at all at any scale.
- macrolime 3y ago
  Maybe solid-phase life wouldn't mainly depend on what we normally think of as chemistry, but instead some other physical processes. Perhaps radiation making patterns in a crystal that somehow manage to utilize an energy gradient in the material to self-reproduce, with the radiation causing imperfections, or mutations, in the patterns. Or some completely different physical process we can't even conceive of because we haven't observed anything like it on earth.
  - jerf 3y ago
    I like to distinguish between "science fiction theories" and science we actually understand. In science fiction, anything goes. If you want to talk about physical processes we've never even heard of, hey, go nuts. I've got my own pet theories. If we want to stick to science, we can in fact use science to put some bounds on things. We don't have to know everything. Physical reproduction in the case you are talking about would have to be incredibly, incredible slow, plural orders of magnitude slower than Earth life. Reproduction of some energy signature might be possible, but without the ability to increase the physical substrate it can run on, that's all it would be. We actually have examples of that today; basically a laser fits the bill here, a crystal (in at least some cases) that can give a particular energy pattern the ability to reproduce. Clearly not life, though. It actually reminds me of theories about life arising on Pluto or something. While we can't necessarily prove it is impossible, I've seen theories about using superfluid Helium as a base liquid for life, we can say it would have to be by necessity excruciatingly slow by Earth standards by the obvious ways the temperature affects chemistry speed. I can't prove a solid is completely impossible to be alive, but it is so, so much slower that it has some serious problems with its sun burning out in the metabolic equivalent of just a few thousand years of Earth metabolism. I like both modes of thought. I do not like people mixing them willy-nilly. It wrecks them both and you very much get a worst of both worlds.
    - astrobe_ 3y ago
      I don't think the speed of the process is really relevant, outside of the pace (or risk) of change of the environment. In animal life as we know it, lifespan ranges from a few days to centuries.

klodolph 3y ago

If you want to understand crystals thermodynamically, in terms of entropy, you should be using a more rigorous notion of entropy. When crystal formation is thermodynamically favorable, the process causes entropy to increase, not decrease. So if you have a crystal which exists in-situ, in the conditions which caused it to form, you don’t increase entropy by un-creating it.

jerf 3y ago

The main problem with crystals and solid-phase life in general is that, being solid, it tends to just sit there and be solid. It's why silicon life is nominally appealing if you just look at the periodic table, but when you look out into the real world and see what the characteristics of the compounds it actually forms look like, you see an awful lot of solids and it isn't really plausible as a basis for life. It helps to look at how biology actually works; we get these images of things like DNA copying where the next amino acid is just sitting there, all but busting in the door to be copied. It gives a very false image of how biology works. In reality it's an insane world down there with a whole bunch of the cell just jiggling around thermally all the time, and the mechanisms all work by waiting to be bashed into by the right thing. Everything is so fast and the rate of jiggling is such that it all ends up working out. But it's nothing like anything we'd design or even very easily wrap our head around. I've sometimes wondered if we were somehow otherwise the same, but not biological, how long it would take for us to ever invent biology. We are certainly nowhere near it now. Crystals and solid-phase in general doesn't have an obvious route to chemistry occurring anything like the way it does in biology, and indeed, it doesn't have an obvious route to chemistry occurring at all at any scale.

macrolime 3y ago
Maybe solid-phase life wouldn't mainly depend on what we normally think of as chemistry, but instead some other physical processes. Perhaps radiation making patterns in a crystal that somehow manage to utilize an energy gradient in the material to self-reproduce, with the radiation causing imperfections, or mutations, in the patterns. Or some completely different physical process we can't even conceive of because we haven't observed anything like it on earth.
- jerf 3y ago
  I like to distinguish between "science fiction theories" and science we actually understand. In science fiction, anything goes. If you want to talk about physical processes we've never even heard of, hey, go nuts. I've got my own pet theories. If we want to stick to science, we can in fact use science to put some bounds on things. We don't have to know everything. Physical reproduction in the case you are talking about would have to be incredibly, incredible slow, plural orders of magnitude slower than Earth life. Reproduction of some energy signature might be possible, but without the ability to increase the physical substrate it can run on, that's all it would be. We actually have examples of that today; basically a laser fits the bill here, a crystal (in at least some cases) that can give a particular energy pattern the ability to reproduce. Clearly not life, though. It actually reminds me of theories about life arising on Pluto or something. While we can't necessarily prove it is impossible, I've seen theories about using superfluid Helium as a base liquid for life, we can say it would have to be by necessity excruciatingly slow by Earth standards by the obvious ways the temperature affects chemistry speed. I can't prove a solid is completely impossible to be alive, but it is so, so much slower that it has some serious problems with its sun burning out in the metabolic equivalent of just a few thousand years of Earth metabolism. I like both modes of thought. I do not like people mixing them willy-nilly. It wrecks them both and you very much get a worst of both worlds.
  - astrobe_ 3y ago
    I don't think the speed of the process is really relevant, outside of the pace (or risk) of change of the environment. In animal life as we know it, lifespan ranges from a few days to centuries.