I read a long time ago an essay by Asimov that described what elements could support life as a building block and why most elements cannot. I didn’t fully understand that at the time but it was interesting to see why carbon based makes sense and some other random element does not work.
Similarly, I wonder if under different planetary conditions, smart alien life (so not single cell life) can be very tiny or very large, or if there are biological constraints that would restrict that size range regardless of basic setup.
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I’m too lazy to do the math properly but the theoretical minimum size is potentially roughly whatever the [Bekenstein bound](https://en.wikipedia.org/wiki/Bekenstein_bound) for the roughly 2.5 petabytes of data in the human brain would be – that’s just the memory, not the processing, so the real size will be way greater, but should probably be somewhere around the same order of magnitude. Apparently it’s about [10^69 bits per square meter](https://www.pbs.org/wgbh/nova/article/is-information-fundamental/) so for 2.5 petabytes it would be about 10^-27 meters.
That’s really small – it is small enough that if you were the size of an atom, it would still be the size of an atom to you, except you repeat that one more time. It’s so small that we don’t know anything about what’s possible at those sizes and there might be something unknown that makes it completely impossible for computation to take place there for some reason or way weirder things we don’t know about.
You would probably not be looking at life that has evolved out of atoms but something way, way, way smaller, and as we don’t know anything about whatever particles might exist at that scale. It’s impossible to say if it would support life (presumably all you need for life is a particle system of some kind, ours just happens to be one that does support life), but if it can, there’s no fundamental reason it wouldn’t be capable of evolving to the same cognitive level as us.
It’s a weird intuition that many people seem to have that planets and stars might be analogous to atoms, while galaxies may be like small cells in some larger organism, and as such that atoms might be like small solar systems – or some variation on that same theme – it’s probably a misinterpretation of the Bohr model of atoms, but who knows, there might be something to it. There is no proof for any of this, but the atom got its name from being unsplittable, so it’s not like there are limits to our ignorance.
Something very big looking at our solar system by launching planets at it might not notice how one of the “electrons” has a moon or people on it. They just notice how, on average, stuff going in tends to come out. When 5 billion years is less than the blink of an eye and the size of the universe is microscopic, the deaths of stars might look more like chemical reactions. Somewhere in that infinitely huge world somebody might be doubting whether we could exist even in theory.
Some of it depends on local gravity. Gravity lower than Earth’s would support larger creatures more easily. Living in water also helps offset gravity. Higher gravity would mean smaller animals, because larger/heavier would have a hard time moving around. “Square-Cube” law applies.
It really depends on how many neurons the thing needs to operate it’s body, and how “sloppy” the activation thresholds for neurons in the system are.
A system with little “indeterminate” activity at the thresholds and boundary conditions can get away with having significantly fewer neurons since there’s less noise impinging on the Information of the system, and so fewer votes are necessary on precise things.
A system with more complicated motion requirements, a bigger body, terrestrial motion, more complicated balance system, etc. is also going to need more neurons before “linguistic translation, encoding, and embedding on a high-dimensional latent space” is possible in the system.
Humans have a LOT of neurons devoted to processing data about all sorts of shit that not every organism is going to need to care about.
Depending on the context, I suspect that 7-8 billion neurons could do the job of producing a fully capable human level of intelligence on a large variety of tasks, though this excludes most physical tasks.
Intelligence, the way I see it, is relative behavioral adaptive advantage. Put in a cockpit as a chess player, the faster you can figure out how to land the plane safely the smarter you are. Unless people know you were forced into that situation, in that moment you will be dumber to most people than a pilot in your stead until you prove to others you fit within the environmental niche by successfully landing the plane.
Now, efficiency, that has to do with energy and entropy, right? You need to efficiently perform the correct observations and actions in sequence before you’re awarded the title of intelligent. That means information has to travel at a resonant efficiency to each time window.
An entity that has a really large brain would necessarily have to have information travel a longer distance before actions can be performed, but there would be a variety of space to store actions at least. There are whales known for picking up right where they left off on songs they sang together a year prior. An entity with a really small brain would necessarily have information traveling very short distances prior to performing actions out of a very limited pool. Somewhere in the middle fits most of the niches we’re into.
Scotty: What kind of intelligent creatures could exist in a thing that small?
Spock: Intelligence does not necessarily require bulk, Mr Scott.
It is not just size but also organization of the brain (or its equivalent)….for example, birds have a better organized brain structure enabling them to do a lot more with a much smaller brain ([https://www.science.org/content/article/why-bird-brains-are-more-brilliant-anyone-suspected](https://www.science.org/content/article/why-bird-brains-are-more-brilliant-anyone-suspected))…It is also possible that there may be small organisms that can communicate (e.g. using light/other EM radiation) for a “swarm intelligence” that is decentralized and self-organized. And that’s just life as we know it….it’s possible that there is life as we don’t know it that is entirely different in every aspect (e.g. in patterns of electricity or plasma around a black hole) that does not live on planets and which we may not even recognize as life (and which may not recognize us) as our time scales are too different.
We simply, do not know. We can theorize all we want. But, as far as we understand, we only have as source organic DNA/RNA lifeforms.
Once we find life that is not “earthbound” we may start theorizing other permutations.
I heard a wonderful sci-fi story many years ago. We made contact with aliens and agreed a site and time for them to land. So the reception was set up for them to land on an airfield. We spoke to them as they were coming in. They said they were coming into land at the specified coordinates but could not see us. We could see that they were indeed coming down in the centre of the airfield, but we couldn’t see them. Then they said they hit water and we’re sinking fast and we’re drowning. Confused a member of the reception committee ran out to the centre of the airfield where they were supposed to be but all he could see were puddles.
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