So life exists on Earth. Earth is not functionally unique in composition or circumstance. And the universe is achingly huge and has an absolutely stupid amount of matter and energy doing every possible thing it can do all the time. That’s my unassailable case for the existence of extraterrestrial life and not sure what to say to anyone who needs more convincing that it’s out there.
Just knowing that is fun because I can get lost in dreams of ocean worlds with single celled organisms as large and ancient as redwoods, swarms of silicone fleas that move like willful sand dunes, or miles long snail colonies that spend their entire life traveling in a train in the same position they were born in. And no matter what crazy combinations of Earth inspired flavors of life I come up with, I know something reasonably similar is out there, and no matter what I come up with I know it’s not even close to as weird as it gets.
So life is out there, it just is. But where is it? Earth like planets are widely considered the most likely planets to find Earth like life. Seems pretty logical. Though that’s just Earth like life and I personally prefer more cosmic weirdness in my extraterrestrial life than some knock-off Earth can probably put together. So a more general rule for looking for life on other planets is- look for planets.
It’s also fun to ponder more exotic mechanisms for ‘life’ within a star or nebula, anywhere there’s an energy gradient and some matter and some fun symmetry breaking physical interactions. But the most rational ground for speculations about life that we might actually recognize as life, seems like it would be in places with a lot of ground.
Asteroids and other small objects have ‘ground’ but I think an object has to be large enough to retain some atmosphere to support much life. Some regular interface between solid and fluid layers would seem to be key. I’m not sure a fully liquid or gas world with no definite solid interfaces really incentivizes complicated internal modeling of the physical world. Life in a vast, relatively homogenous expanse might never experience any pressure to develop the kinds of intelligence needed to host very complex minds. But who knows, obviously there are interesting fish in the deep ocean, but the web of life on Earth is interconnected from the first cell so I’m not sure they’d ever have gotten interesting without all those influences from other environments.
In any case- planets are almost certainly the most prolific nurseries for life in the universe.
Gravity, especially the kind that includes a ground interface, is kind of a universal catalyst. It makes things more likely to interact than they otherwise would be. Obviously there’s nothing catalytic about gravity’s role in these interactions but I like the word there. At the largest scales accretion literally makes the ground, and at the smallest scales it just keeps things concentrated in piles and puddles that otherwise might just drift off on their own without bothering with other matter. It’s just overwhelmingly beneficial for making the matter-energy soups that life can sometimes emerge from.
Then, if and when life does bubble up in the soup, gravity gives it all kinds of advantages in orientation, locomotion, and just keeping life’s preferred environment wrapped around it. Gravity is a stern disciplinarian, but it is supremely fair and even handed. Gravity is a nurturing parent for life’s infancy, and it does a decent job of imparting some useful gifts to its progeny without spoiling them. But gravity is also a little clingy and possessive, and it can even become a little tyrannical once any species starts trying to leave the nest.
So by the same reasoning that I assume life exists beyond Earth, I assume intelligent life exists beyond Earth as well. What ‘intelligent’ means there is a whole other conversation, but for this ramble let’s just say it’s a species that rises above its natural place in the food chain through use of large scale organization and technology, and where interspecies cultural forces become the dominant selection pressure instead of environmental fitness.
It’s probably as proportionately rarer than simpler life as it is on Earth, but I think it’s just as inevitable.
I don’t have much basis for this- but I think intelligent life on Earth came with a few advantages that not all intelligent life will have. The most important is a clear view of the stars through the atmosphere, and the sensory organs to detect starlight with the naked eye. The movement of the stars presents a universally accessible intellectual challenge that I think was crucial to developing and exercising the parts of the mind that helped human civilization advance to our current state. I think it may be a universal advantage, and perhaps necessity for civilizations as advanced as ours.
I do like to wonder how far a civilization might get in discovering universal scientific principles without a view of the stars. Maybe it’s only a limit to astronomy and some creatures that evolved deep in a greenhouse gas locked world could develop understandings of fluid dynamics and quantum mechanics exceeding our own but only Newtonian gravity.
Also the fact that our atmosphere supports fairly simple methods of controlled but substantial thermal manipulation through combustion of plants probably counts as a rare get. Also metals occasionally laying on the ground. But I am careful not to be too anthropic about what counts as an advantage to an ‘technological civilization’ because the tendency is to define everything in terms of its value to the specific human march of technological progress. But I’m not saying any of these things are requirements. I can imagine a civilization of squids using complex woven structures for undersea construction and defense, and vivisected manta rays and whales as motive power in some horrific analogy of steam power. I don’t see any hard limits to such a civilization reaching something at least as advanced as the Roman or even British Empire all without fire or metallurgy. And once you get to a species to Roman status I think it’s fair to say you just can’t predict what they could or couldn’t do from there.
But whatever the general trends for intelligent life, there’s a clear distinction once a civilization starts learning about places beyond its home planet, sending objects there, and maybe going there themselves.
I’d like to say by the same reasoning that life exists, and that intelligent life exists- that intelligent spacefaring life exists. And I did actually just say that, so I’ll just stick with it. I’m reluctant because I don’t want to suggest it’s an inevitability for intelligent or even highly advanced life to go to space, not exactly. I think there’s a chance that actually going to space is extremely rare even among species that know a lot about the universe. Maybe the combination of intelligence, demands of breaking gravity, and the body construction needed to survive those demands, are just very, very unlikely to work for many species. Maybe a lot of the intelligent life in the universe is more like an elephant or a whale, just unreasonably huge. No matter what, there would never have been an elephant Yuri Gragarin or Neil Armstrong. The rocket equation is hard enough on apes and nature made us light enough to pull ourselves off the ground. Gravity is unfair. But I think robotic probes, or maybe even some attempts to ‘seed’ other worlds with spores or something, might be common alternatives.
So I guess it’s more accurate to say I think it’s pretty inevitable that intelligent life that has natural senses that allow it to be aware of space beyond their planet, will inevitably endeavor to interact with space in some way. Interestingly this clarification is completely contrary to the titular claim of this essay. But I haven’t actually made that point yet, so I’m just going to pretend none of this happened.
Okay- so it did happen, so I’ll address it. I think there’s good reason to focus on spacefaring life that can actually take themselves to space. Besides a colonial, spore expansion theory, which is kind of silly, a planet locked species is inherently limited in range, so it’s just statistically less likely we’ll ever encounter any. Also I think it’s less likely we’d have any means of understanding one another than another space capable species. There’s just a lot of inherent common ground and means to communicate ideas between two species that build spaceships they actually climb into. Even if distance prevents us from ever communicating in real time, or even completing an exchange within a human lifetime, the universal challenges of spaceflight might at least give us some means to understand how another species addressed those same challenges and a beginning to understanding how they live.
So for the purposes of this essay I’m just going to use intelligent, spacefaring life to mean exclusively species that go to space themselves. Not trying to diminish species that don’t go themselves, it’s just a simpler classification and it works with the title.
So it’s been a long road to saying I think intelligent, spacefaring alien life inevitably exists. Okay. So where do we look for intelligent, spacefaring aliens? Planets again? Makes sense, I made a lot of words saying that’s probably where they came from. But then again, we’re looking for space faring aliens, and planets have a lot of gravity, and being in a lot of gravity makes space flight really, really hard.
Yeah, but they’re advanced, they’ll have awesome rockets, or space elevators even? Right? Sure, at some point any species that moves towards sustainable existence beyond their planet will master gravitational escape far beyond humans best efforts to date. They may sustain that mastery for a while, maybe indefinitely on their home planet.
But the further a species ventures out into space, the more individuals who live in space will change. Even if moving between a planet’s gravity and space becomes trivial, individuals who live in space will need to maintain their ability to exist in their home gravity in order to return there. Maintaining that ability will demand resources, and becomes less relevant as they move further from their planet, or just decide not to return. The further out they go, the less sense it makes to bother with ever returning to living in gravity.
After a very few generations, maybe only one, spaceborne individuals will become reproductively incompatible with their planetary counterparts. Not just due to gravity. I’m working with the general assumption that any species isolated from the pressures of its origin environment will diverge from its original form because of whatever process that led to the environmental pressures evolving the species in the first place. May work in some radically different way to DNA, but it’s iterative, and it’s driven by environmental pressures. Seems like enough to make isolation in a radically different environment have the same effect on all life.
There may be some genetic exchange with the homeworld, but it will be almost exclusively one-way (planet to space) and it will be limited. A kind of speciation seems fairly inevitable. Even if they could maintain relatively close contact with a home world, I just can’t see a spacefaring civilization not developing at least two distinct and increasingly incompatible subspecies.
I’m getting further out on a thin limb here, but I’m going to speculate that’s an unsustainable status quo. Eventually, the civilization will diverge and the spacefaring, intelligent aliens will become entirely that. Maybe it’s a cycle, and different ‘waves’ of spacefaring intelligent life or cultures, can develop from the same original planet and species. Maybe there’s a lot of planet hopping involved and they colonize new homeworlds too, but I think the same barriers between planetary and space existence would lead to the same outcome. Any species that can exist indefinitely in space, will probably find a lot of incentives to do so.
So if we’re looking for intelligent, space faring civilizations, I think we actually shouldn’t be looking at planets, but in space. That narrows it down…
Well yeah that’s stupid. Where in space? Well they’ll still need resources to support the technologies they use to survive, move about, and build in space. That means matter and energy, and in this universe the place to get those is a solar system. That actually does narrow it down, but that’s where planets are so we’re already doing that. Except I made a big deal about how I think they won’t be hanging out on planets.
So solar systems, but not planets. Pretty much leaves the sun and ‘other’. Stars tend to hurt up close, so I’m going to say it’s ‘other’, that’s where we should be looking. ‘Other’ is asteroids, comets maybe, smallish moons, maybe planetary ring systems. Anywhere you can collect a useful amount of matter without getting pulled into a significant gravity well.
I expect they’ll find ways to set up permanent settlements and industrial capacity, A great deal of resources are available in an area like Sol’s asteroid belt. It has enough surface area and raw resources to support a massive population indefinitely provided they have the technology to convert the available raw materials in a fully closed technology supply chain. This is a long, long way off from anything modern human technology can achieve, but a lot of that is economic and general lack of will, effort, and ingenuity. But if the whole human species somehow put permanent Apollo program level commitment towards colonizing the asteroid belt, it’s not at all inconceivable that we could, even within the presently accepted limits of relevant technologies. It is challenging to imagine reproducing some of human’s heavy industrial capacity in zero gravity, but there are no intrinsic limitations. It may turn out to be advantageous since the effects of gravity can be effectively reproduced in free space but the properties of free space cannot be reproduced in gravity. So fabrication in zero gravity would eventually offer more options than would be available on Earth.
And once a species is set up with the technology to exist like that, they can probably do it pretty much anywhere. The requirements of living on any given planet can vary wildly. The atmospheric composition, weather, techtonics, maybe indiginous life, it’s a constellation of issues that require custom technological solutions. Whether terraforming or creating habits, planet hopping aliens would have to have a catalog of technologies that seems unimaginably complex.
Living in microgravity gravity environments with little atmosphere is pretty much the same everywhere you go. Once you get your atmosphere, food production, radiation protection, thermal management, etc, all wrapped nicely for life in the void you can plant it anywhere there’s void without too much modification. You can set up shop anywhere you can find the resources necessary to maintain your technology.
Also solves some of the issues of interstellar travel. Just assemble the materials and thrust you need for the journey and some prospecting on arrival. The journey is basically the same as living in an asteroid belt, just less interesting views and living off your stash. And of course once they get there they just need to find another field of useful matter and they’re home.
So- that’s it. That’s why I say intelligent life hates gravity. I think there’s good reason to think space faring aliens will trend towards living exclusively in space, and if they do that they’ll probably hang out in places with readily available matter, but little concentrated gravity, like an asteroid belt.
Unfortunately this is entirely useless. We’re just starting to reliably detect planets around other stars and that’s just to say they exist, a general size, and more-or-less where they are in the stars orbit, not even close to directly imaging them or anything. So it’s not like we can just start combing the areas between planets and expect to find some neat-o pod cities full of fraggles or something. As with most of my little points it’s unprovable, doesn’t change anything, and was ultimately just an excuse for me to babble about what I think about space stuff for a while, but I did that- so mission accomplished.