[henearkr]

You only considered chemistry-based life. Cannot hold it against you of course. But some hard SF writers like Baxter also imagined life based on electromagnetic interactions, nuclear reactions (life in the mantle of a neutron star), fluid vortices and turbulences (life in liquid or gaseous planets), etc. Basically he included a lot of substrates that could be used to implement complexity.

Also, a big drawback of searching only chemistry-based life is that it limits a lot the range of viable temperatures. Would be too slow and simplistic at low temperatures, and a complete uncontrollable chaos at high temperatures.

In particular, finding a brine on an ice dwarf like Ceres is not very exciting, as the temperature is too low, and no interesting chemistry can happen.

Whereas other substrates could be totally fine at different temperature ranges.

[Balgair]

That neutron star story is wild. Hard recommendation to read.

One point I have with Baxter is that his premises are just bananas, but the people acting in them are pretty recognizable. To be fair, if the characters were also nutter-butter, no one would read it, as it wouldn't be a story anymore, just a strangely formatted research paper.

https://en.wikipedia.org/wiki/Flux_(novel)

[gizmo686]

For another life on neutron star: Dragons Egg, Robert L. Forward

[henearkr]

I don't know if you read the other books from the Xeelee series, but the neutron star is probably not even the strangest life form Baxter considered :) I don't want to spoil too much though.

[Balgair]

The Xeelee Sequence is totally crazy.

Not many authors can go the distance from the beginning of the universe, to the end, and then back around again.

They Hyperion Cantos is also good reading. It starts with a re-write of the Canterbury Tales in the far future, and has the pilgrims making their way, not to Canterbury, but to face off with a six-limbed red-eyed spike-covered murder beast that exists outside of time. It ends with hyper-evolved humans and the second-coming facing off against god-like AIs.

Trust, me, it actually works really well.

[thom]

I can never forget reading Titan for the first time. Extremely bleak in many ways but worryingly plausible.

[simonh]

Where I think most of the proposed alternate forms of life in SF fail is they focus on complexity but disregard the need to maintain order. Vortices are a good example, theres plenty of complexity there, but also a huge amount of entropy and no real way to maintain ordered, purposeful changes in structure, or isolation of function. Complexity just isn't enough, so until some of those ideas get a lot more clearly developed, and solve some fundamental issues I just don't find them compelling. Great for fiction and speculation, but not really relevant in real world investigations.

Yes, I know that makes me sound like the boring, hide bound characters in such novels that are incapable of understanding this new amazing form of life, but frankly in the real world those guys would be absolutely right. The protagonists who contact the amazing new life forms just make far too many fundamental errors and intellectual shortcuts to really be credible.

[henearkr]

I agree those are mere plausible ideas with no real foundations, but the aim is to open our imagination to the realm of the plausible. Even those phenomena that are improbable and barely plausible, there are some of them we will encounter, and thanks to the work of sf writers we will not be too much caught off guard.

Specifically for your point on entropy and stability of vortices, I don't disagree totally though I'd like to call your attention on what is known with magnetic skyrmions. They are stable because to change spin the particles would need to overcome huge energy barriers. Then, the only difference with fluid vortices is that in a fluid there is friction that can bring the fluid elements to gradually shed their angular momentum at the contact of other elements with a different momentum. But in superfluid states that you could encounter at very low temperatures (like on some distant planet etc), it is plausible that there would exist analogous energy barriers preventing the fluid elements to directly shed their momentum! And even though, you can of course imagine fluidic circuits and rotational computations, which would have some stability thanks to the superfluid state.

Of course all of that is baseless speculation, but the point of SF is precisely to appreciate the vastness of the world of plausible phenomena...

[Razengan]

"Life" could also be AI machines.

If we seeded a planet with sufficiently advanced robots, that can mine and build and learn and make copies of themselves on their own, and a few centuries later they have a civilization, does it matter what they're made of?

For all intents and purposes, it would be life.

Perhaps at some point we should/will have to stop saying "life" at some point and use terms like "agent" instead, to include disembodied intelligences shaping the universe through their decisions and stuff like that. :)

[fsloth]

I don't think you should confuse life and agency. I fail to see how a bacteria would have any agency.

[bryanrasmussen]

Well then if you found a place with bacteria but nothing advanced you would put in your captain's log that "the fundamental requirements for agency to arise were found, but as yet agency had not been achieved" or some such phrasing.

[ajuc]

> I fail to see how a bacteria would have any agency.

It does stuff on its own. That's agency.

[Razengan]

> I fail to see how a bacteria would have any agency.

Why would it not?

[at_a_remove]

Oh, I remember the convection cell Qax from Baxter, read Dragon's Egg when it came out, or Brin's Sundiver for solar dwellers, or go even further back for the Piers Anthony's OX, even the frozen lattices of light from 2001. I could try speculating on some pretty strange forms of life, and have, but ultimately life -- and as fuzzy as that term is -- might well be construed as interlocking sets of cycles, self-perpetuating at the expense of various resources, always with the second law coming up from behind, waiting to knock it all out of balance, pluck teeth from the gears.

I could talk about how the various conditions at the surface of a neutron star probably cannot support the kind of interactions that would lead to a nuclear pseudo-chemistry (the elements aren't as important so much as the kind of bonds, and therefore structure supported, are, with the other physical properties being less important), but I would like to take a different tack and think about life arising. How would all of those little cycles, circadian down to Krebs, get started?

My intuition? guess? is that just as we are big bags of internalized seawater, life would have hijacked, replicated, and then encapsulated already existing cycles, multiple cycles. Just once cycle wouldn't cut it, probably not even two. I think for us it was all about warm little tidepools, water comes in, then the day-night cycle keeps changing the concentrations. Another tide comes, more water and something, perhaps waste, is washed out. Enough times, enough luck, maybe something sticks, holds something back in case the next splash isn't as big. The next big trick is a membrane, something to isolate the cycles. Separates the outside from the inside. Now there's something to separate.

Overall, though? You're still going to need matter that supports both structure (at least for a membrane, a boundary between in and out) and fluidity (for those cycles). I've thought a lot about what the bare minimum would be, but the Earth chemistry is just a shorthand for "what bonds, and therefore structure, can be maintained?" and "how will it flow?" I am pretty confident in saying it would have to obey Fermi statistics, instead of Bose, because bosons love to play follow the leader, but fermions need to stand out (and apart) enough that they can at least stand. The convection cell entities were interesting to think about but would require an almost unparalleled level of stability and uniformity across large expanses of matter, sort of a large-scale "lab conditions" environment, free of fluctuation and interference, somewhere relatively calm. I have considered something not too far away from that, life existing in an environment where the average energy levels were constant, but the entropy wasn't: life optimized to hunt not for calories but for pockets of order to bolster its own.

Non-chemical life is fun to speculate about but ... I keep coming back to structure and fluidity. It's difficult to find phases of matter that support both that aren't in the chemical domain.

[henearkr]

Nice to see that I speak with a peer SF lover! ^^

I agree, I would be surprised if we discover first alien life in a non-chemical form. Somehow though I would love to be surprised!

There are so many possible environments and substrates, and we cannot think of all of them. The multiplicity of the places where things could happen, and the scale and age of the universe, also increase the possibilities that there are places with the right conditions or stability. The conditions on Earth were kind of lab-grade perfect too! Any nearby supernova, ill-directed solar flare, etc. could have nipped life in the bud. Only the huge number of Earth-like environment in the universe, and the large interval of time allotted, can justify that we have had the chance to arise in these conditions.

PS: also, to be fair, a lot of life forms in Baxter are actually engineered. But our First Contact (or First Observation) could be as well with a "natural" form as with an artifact! And that would not matter that much.

[imhoguy]

Reminds me Solaris written by Lem. https://en.m.wikipedia.org/wiki/Solaris_(novel)