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There's an entire genre of these kinds of books that extrapolate generalities (life throughout the Universe) from a single data point (life on Earth), but the t

There's an entire genre of these kinds of books that extrapolate generalities (life throughout the Universe) from a single data point (life on Earth), but the truth is, that's not even an educated guess. We do not know if our evolutionary pressures are universal. We do not know if the evolutionary solutions developed here are appropriate even on other Earth-like planets, much less everywhere. Sensitive dependence on initial conditions could lead to radically different planetary environments, necessitating radically different mechanical solutions to survival, some (many, most?) of which we will never have even imagined. What creatures would form under an intense magnetic field? In methane? In close orbit around a dim star? In a hot cloud nebula? Could we even recognize them as alive, much less intelligent? Definitely not if we're looking for bats and monkeys and octopuses No, I think the whole genre of "life is much the same everywhere" suffers from a profound lack of imagination

theyellowkid 5y ago
>There's an entire genre of these kinds of books that extrapolate generalities (life throughout the Universe) from a single data point (life on Earth), but the truth is, that's not even an educated guess. Hey, whatever sells a pop science book pounded out over a long weekend. It's funny how sure everyone was about slowing expansion of the universe and the idea of close rocky planets/distant Jupiters, but only lucky guessers are remembered. It could simply be that patterns for lifeforms on Earth were set so long ago that everything sort of rhymes. Veer that path at the beginning and you end up with a significantly different answer.
- rendall 5y ago
  That's so in alignment with my thinking I'd like to buy you a beer
  - Koshkin 5y ago
    > drink it and forget it all! https://www.goodreads.com/quotes/78268-a-poet-once-said-the-whole-universe-is-in-a https://www.goodreads.com/quotes/78268-a-poet-once-said-the-...
    - rendall 5y ago
      Koshkin, theyellowkid, I, and whoever else thinks aliens are probably profoundly weird: drinking and coming up with increasingly outlandish ideas for aliens. Now that sounds like a party.
      - theyellowkid 5y ago
        When considering deeper questions, I always think of this short story. https://www.gutenberg.org/files/33854/33854-h/33854-h.htm https://www.gutenberg.org/files/33854/33854-h/33854-h.htm
- JoeAltmaier 5y ago
  Nah. Think of fish - and the assertion "There's no such thing as a fish." That refers to the similar evolution of many branches of life that ended up "looking like a fish" but are otherwise unrelated. They had a common ancestor of a coral-like sea squirt (If I remember right). That looked nothing like a fish.
aaronblohowiak 5y ago
Weir’s latest book goes into this. (Ex: Audible hearing is based on the distribution of frequencies generated when solid bodies collide or rub.) On the other hand, If life is that which can use an energy differential to create more order within it (an entropy pump) then sure there are likely forms of “life” out there that we’d have a harder time imagining (that perhaps operate at physical scales and timescales beyond us — thinking nebulae)
- rendall 5y ago
  > Audible hearing is based on the distribution of frequencies generated when solid bodies collide or rub. ... in Earth-like conditions, and useful in Earth-like conditions. Vibration of denser or rarified gasses could require other solutions to exploit, if it's possible at all > If life is that which can use an energy differential to create more order within it (an entropy pump) Now that's the ticket! Under this definition, I suspect most life in the Universe is not carbon based, but far more exotic (to us)
autokad 5y ago
I completely disagree. I think the 'life can look like anything' (lets call them LCLLAs) train of thought suffers from a lack of understanding of constraint satisfaction. Think about how some LCLLAS talked about how silicon life is probably a thing. First off, it it were, given Earth's crust is mostly silicon and its the most habitual place ever discovered, it would have evolved here. but it didnt. It turns out silicon is just too ridged, and to get life going you need all sorts of chemical properties that just aren't congruent to life. We are carbon / oxygen organisms for a chemical reason. despite the availability of other resources, other forms of lifeforms didn't develop for a reason. maybe other forms of life does exist in some methane ocean on Saturn like planets, but its not going to be very complex, and definitely not intelligent life building space ships.
- gambiting 5y ago
  I'm just always surprised how can we be so certain? Even here on Earth, for millions of years, life was literally nothing more than single cell organisms - also definitely "not intelligent life building space ships". And it would be very hard to see how could it possibly evolve into such, seeing as the atmosphere was full of incredibly toxic oxygen. The thing is, life has almost infinite time to evolve out of these various elements. The fact that it didn't evolve here on Earth means absolutely nothing, seeing as Earth alone has billions of years left where such life could arise, and there are literally countless planets everywhere in the universe where the random dice of evolution roll every second.
  - Retric 5y ago
    It’s a question of physics not just chemistry. Deuterium for example is similar to hydrogen chemically so while those differences are slightly toxic to us it’s easy to assume a planet similar to earth with an abundance of deuterium and a lack of hydrogen would evolve life forms with the opposite preferences. Except the ratio of hydrogen to deuterium is a function of astronomy and more specifically fusion. No naturally formed planet is going to end up with that imbalance. Which means no natural deuterium based life forms. So while some alien civilization create deuterium life, it’s not going to be part of natural ecosystems. And so it goes for most possible interesting edge cases. Dependency on rare elements like Neptunium means any competitors without that dependency have huge advantages.
DrBazza 5y ago
This is a theorised list of biochemistry that might support life https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...
- rendall 5y ago
  Thanks. That's great
- Koshkin 5y ago
  Nitpick: "bio" = "life"
NotSwift 5y ago
Physics and chemistry impose some serious constraints on all life forms. On earth we have convergent evolution, independent groups of species independently develop similar solutions for a specific problem. Life on other planets will have similar problems, e.g. reproduction, locomotion and perception of its environment, and its solutions will probably be similar to the ones we have on earth.
- kenjackson 5y ago
  But changes in the environment and initial starting point can result in very different approaches. For example land mammals, reptiles and fish are quite different from each other. Because they've "always been here" we don't appreciate how different they are. Imagine if we had no fish and then found a planet with water that had fish in it -- that would seem absolutely shocking to see animals that could breathe underwater.
  - godelski 5y ago
    Honestly this would be pretty hard to imagine. Even if we had no concept of fish (which I find extremely unlikely given other evolutionary pressures, physics, and mechanics of life, but let's not go there) we would think "birds, but in a denser fluid." I don't think this would be "absolutely shocking" to biologists of that planet. Similarly like how biologists here have predicted methane based lifeforms. Now if we were talking about a fluid like sulfuric acid then yeah, that would be absolutely shocking, but not for the reasons of breathing (it's about electrons).
    - state_less 5y ago
      And all these animal/alien minds swim through time like a fish swims through water. Reminds me of that David Foster Wallace joke. > There are these two young fish swimming along, and they happen to meet an older fish swimming the other way, who nods at them and says, “Morning, boys. How’s the water?” And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes, “What the hell is water?” https://www.newyorker.com/books/page-turner/this-is-water https://www.newyorker.com/books/page-turner/this-is-water
yourenotsmart 5y ago
The example of convergence between fish and dolphins, birds and insects, the infamous "why does everything evolve into crabs" study and so on should tell us that while we should be open for radically different forms of life, the most likely outcomes will look like something we've seen here on Earth. I'm personally expecting something like 80% humanoids and 20% exotic forms. Maybe I'm primed incorrectly by cheesy soap operas and sci-fi TV shows, but I think they're not far off (even if for unrelated reasons like SFX/VFX budget and character empathy).
- rendall 5y ago
  ... on planets. That have a precise similarity to Earth. Sure, I can provisionally accept that.
- dogorman 5y ago
  > convergence between fish and dolphins The convergence between dolphins and ichthyosaurs is even more remarkable. Ichthyosaurs were marine reptiles; air breathing tetrapods that, like dolphins, had ancestors that walked on land but eventually returned to the sea to kick fish ass. https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthyosaur_vs_dolphin.svg https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthy...
  - ncmncm 5y ago
    Bony fish evolved in rivers, and eventually returned to the sea to kick... what? Analogies fail. Those fish are overwhelmingly more closely related to horses than to sharks.
- mike_hock 5y ago
  Sure, organisms that already share a massive amount of commonalities can diverge and then converge again. What about the branches that happened early on? We essentially have only two lineages of macroscopic organisms that are actually fundamentally different: Plants and animals. I would expect any kind of macroscopic extraterrestrial life to be at least as distinct from Terran plant and animal life as they are from each other.
causi 5y ago
Agreed. At a bare minimum, human thought patterns have to be rare. At some point we're either going to murder ourselves or create a Von Neumann machine capable of interstellar flight. After that humans or human-derived machines will fill the universe. Since that obviously hasn't happened with alien machines, the aliens are either not alive or totally unlike us.
- cryptoz 5y ago
  I don't agree that human thought patterns have to be rare, or your other assumptions. The only safe bet in this discussion I think, is, we don't know anything for sure. > At some point we're either going to murder ourselves or create a Von Neumann machine capable of interstellar flight. There are many, many possibilities for human futures that are between those two and not do extreme. It is absolutely possible we survive millions of years without interstellar travel or self destruction. > Since that obviously hasn't happened with alien machines I also think it is not so obvious that this hasn't happened or isn't happening with alien machines. It certainly could be and we would not know either way. A la 2001: A Space Odyssey, perhaps in fact we are a product of alien machines themselves.
- idiotsecant 5y ago
  There is a book Accelerando by Charles Stross that talks about why neither case might be true - he shows a scenario where life ultimately transforms its host system into a matrioshka brain. At that point distance from the cloud is reduction in bandwidth to the parts of yourself that exist in that cloud- if the matrioshka brain can simulate billions of planets and leaving it makes you incredibly stupid by your normal standards why do it?
  - causi 5y ago
    Accelerando is a great book even if his writing style is a little dry. The mass of one planet being able to simulate billions of planets is only possible if the simulation is rather poor. You can't create a perfect simulation like that any more than you can perfectly simulate seven atoms using three atoms. Computation is never going to be more efficient than physics. why do it? Everyone doesn't have to do it. Just one person out of billions does. Think of the strange and perverse collection of behaviors we observe in a population of a few hundred million people online and speaking English. Expand that to billions of hyperintelligent minds and somebody is going to want to colonize the universe.
alkonaut 5y ago
Of course the environment will determine life forms. What the article says is that if there is a gaseous atmosphere, for example, then selection will reward animals that are able to move through it. That means for organisms that are heavier than the surrounding atmosphere - most likely - wings. For liquid environments, there probably aren’t that many locomotion techniques that are both effective and missing on earth, meaning when we see something swimming in water on a different planet it’ll look like a jellyfish, octopus, fish, worm, clam, bacteria, shrimp, horse… or one of the other hundreds of ways of swimming
- rendall 5y ago
  Once we move outside Earth-like conditions, we should be decreasingly confident about our speculations, not more confident. What are the chemical and physical conditions of a hydrocarbon lake at 5g, -180C, 1 kilotesla and 100 atmospheres? Can we really be confident that "whale" is the best mechanical solution for moving around there? Can we really be confident that "moving around" would even be the best survival strategy? I think not.
  - alkonaut 5y ago
    Indeed earth evolutionary processes require earth like conditions. But here I mentioned swim in water which is a pretty strict constraint on temp vs pressure. That said even in any other fluid I doubt we’ll ever look at an organism and say “it swims like …<blank>“ because there wasn’t an earth organism that swims anything like it. Of course that means comparing to every method of swimming locomotion on earth which is a staggering diversity from the microscopic up to whales. Unless other forces are involved (e.g electromagnetism isn’t used for locomotion on earth to my knowledge) and the fluid is incompressible like water, then I’m (armchair) guessing “to swim” doesn’t have that many evolvable solutions, regardless of pressure/temperature and the specific chemistry.
Koshkin 5y ago
> What creatures would form On the one hand, the conditions under which some lifeforms are thriving here on Earth are already pretty extreme. On the other hand, indeed, we may not yet be in a position to be able to imagine, realistically, all that we would (eventually) agree to call a lifeform. (Life built from phonon "particles" in a planet-size crystal, anyone?) Sure, there may be constraints, such as life, in a meaningful sense, may only be realizable based on polymers, in which case the conditions must be such that they allow polymerization of simple substances to take place.
- titzer 5y ago
  > On the one hand, the conditions under which some lifeforms are thriving here on Earth are already pretty extreme. Not really. They are all within +/-5km of the planet surface, live under 1g of gravity, as a rule, are not exposed to X-rays, gamma rays, cosmic rays, strong magnetic fields or nuclear radiation, or extreme temperatures. There's nowhere on Earth that receives more than about average solar radiation or gets much above 100C where life survives. Life generally has access to ample oxygen, though a few anaerobic organisms exist. They're all DNA-based, have access to ample amino acids, aren't bathed in thousands of completely toxic chemicals, have liquid water (and not, e.g. liquid methane). The list goes on and on. Yeah, there are a few extremophiles, but they are by far the minority, and are clearly adapted incrementally from other organisms that evolved in non-extremophile environments. In essence, there's a large reservoir of easy-pickins living that generates biodiversity to cross over into extremophile environments. Now imagine 5x the gravity, 100-1000x the solar irradiance, the lack of magnetic field (and thus direct exposure to solar winds), no atmosphere, or atmosphere entirely composed of a toxic gas, extreme exposure to X-rays, etc. The universe is full of many places where Earth life, even extremophiles, would have no chance of survival. And such places don't have reservoirs of biodiversity from which to adapt to these conditions. They're just dead.
  - rendall 5y ago
    > They're just dead. We have exactly one example of an environment that nurtures life. It does not logically follow hence that it is the only environment where life can thrive (unless we choose to define life as that which thrives in an Earth-like environment) I do agree that probably most of the Universe is hostile, not only to Earth-like life, but to life of any definition. But we cannot be certain. We have never visited nor sent a probe to a 5g planet "100-1000x the solar irradiance, the lack of magnetic field (and thus direct exposure to solar winds), no atmosphere, or atmosphere entirely composed of a toxic gas, extreme exposure to X-rays".
guyomes 5y ago
> Could we even recognize them as alive, much less intelligent? If we focus on recognizable features, we may look for organisms with self-replication skills (a feature of living organisms) and prediction skills (a feature of intelligent organisms). On the intelligence aspect, the skill to predict the future in general, and imminent threats in particular is useful for structured organisms less resistant than rocks to survive. On that matter I wonder, do unicellular organisms on earth have prediction skills? What also helped those fragile structures to continue existing along rocks after a long time might be their ability to replicate themselves before being destroyed. Reproductive skills might actually be the first interesting feature to look for in extraterrestrial organized structures.
- rendall 5y ago
  > we may look for organisms with self-replication skills... and prediction skills... Sure, but I imagine this is easier said than done. We 21 c. humans would be most likely to recognize as intelligent life something obviously not a natural feature of the landscape, that operates on a time scale under a year and above a split second or so, that predicts that which we can predict, and most importantly has a form corresponding to Earth creatures. Without ticking all those boxes, especially in a truly strange chemical environment, we will have people asserting that they are a complicated chemical processes, but in no sense alive the way we are alive, if we can even recognize them at all.
acituan 5y ago
> What creatures would form under an intense magnetic field? In methane? In close orbit around a dim star? In a hot cloud nebula? Before the question of what you have the question of if. Then you have the question of continuous constraints. Sensitive dependence on initial conditions still has to operate in a constraint space, and maybe constraints for complex adaptive living systems are much tighter to begin with. Tornados are also sensitive to initial conditions, they are even self organizing, but they are not living beings for example. Imagination is fine when you’re not burdened by starting a working system from first principles. Conceivable sounds probable when you know less about the constraints.
- rendall 5y ago
  > Before the question of what you have the question of if. Meh. I mean, sure, when all is said and done, everything is constrained by physics and chemistry and imagination has no bearing on this reality. On that we agree, to the point that stating it outright is almost a non-sequitur: a true statement that has no relevance to the discussion at hand. Human culture, in the 400 years of since the first glimmering of the scientific method, has made gigantic leaps in understanding objective truths about our Universe and what lies within it. At every step, highly educated people confidently assert that we know all that is worth knowing and everything henceforth will just be filling in the details. At every step, these assertions have been a failure of imagination. I can confidently state with only historical evidence to go by that our current understanding of the Universe is deeply flawed and will be completely overturned someday. Or if not, it would be because we're just not intelligent enough as a species to do it, and not because we know it all* It is this sense that I mean, when I say that asserting all life throughout the Universe will have forms like those found here, is a failure of the imagination. * Everything that we ever will discover is constrained by the form of our bodies, our evolutionary history, our psychology, and to a lesser degree by our cultural outlook and worldview. There are truths about the universe that are literally forever beyond our discovering because we are incapable of discovering them.** Were we to encounter alien entities that made use of such hypothetically inaccessible principles, especially if their physical forms were based on them in some way, we would literally not understand what we're looking at. ** As an aside, that is my favorite explanation for the Fermi Paradox, that the interstellar cosmos is thrumming with the signs of life and civilization, but we only partly and minimally understand what we're looking at, and so miss these signs.
deleted 5y ago
[deleted]

theyellowkid 5y ago

>There's an entire genre of these kinds of books that extrapolate generalities (life throughout the Universe) from a single data point (life on Earth), but the truth is, that's not even an educated guess. Hey, whatever sells a pop science book pounded out over a long weekend. It's funny how sure everyone was about slowing expansion of the universe and the idea of close rocky planets/distant Jupiters, but only lucky guessers are remembered. It could simply be that patterns for lifeforms on Earth were set so long ago that everything sort of rhymes. Veer that path at the beginning and you end up with a significantly different answer.

rendall 5y ago
That's so in alignment with my thinking I'd like to buy you a beer
- Koshkin 5y ago
  > drink it and forget it all! https://www.goodreads.com/quotes/78268-a-poet-once-said-the-whole-universe-is-in-a https://www.goodreads.com/quotes/78268-a-poet-once-said-the-...
  - rendall 5y ago
    Koshkin, theyellowkid, I, and whoever else thinks aliens are probably profoundly weird: drinking and coming up with increasingly outlandish ideas for aliens. Now that sounds like a party.
    - theyellowkid 5y ago
      When considering deeper questions, I always think of this short story. https://www.gutenberg.org/files/33854/33854-h/33854-h.htm https://www.gutenberg.org/files/33854/33854-h/33854-h.htm
JoeAltmaier 5y ago
Nah. Think of fish - and the assertion "There's no such thing as a fish." That refers to the similar evolution of many branches of life that ended up "looking like a fish" but are otherwise unrelated. They had a common ancestor of a coral-like sea squirt (If I remember right). That looked nothing like a fish.

aaronblohowiak 5y ago

Weir’s latest book goes into this. (Ex: Audible hearing is based on the distribution of frequencies generated when solid bodies collide or rub.) On the other hand, If life is that which can use an energy differential to create more order within it (an entropy pump) then sure there are likely forms of “life” out there that we’d have a harder time imagining (that perhaps operate at physical scales and timescales beyond us — thinking nebulae)

rendall 5y ago
> Audible hearing is based on the distribution of frequencies generated when solid bodies collide or rub. ... in Earth-like conditions, and useful in Earth-like conditions. Vibration of denser or rarified gasses could require other solutions to exploit, if it's possible at all > If life is that which can use an energy differential to create more order within it (an entropy pump) Now that's the ticket! Under this definition, I suspect most life in the Universe is not carbon based, but far more exotic (to us)

autokad 5y ago

I completely disagree. I think the 'life can look like anything' (lets call them LCLLAs) train of thought suffers from a lack of understanding of constraint satisfaction. Think about how some LCLLAS talked about how silicon life is probably a thing. First off, it it were, given Earth's crust is mostly silicon and its the most habitual place ever discovered, it would have evolved here. but it didnt. It turns out silicon is just too ridged, and to get life going you need all sorts of chemical properties that just aren't congruent to life. We are carbon / oxygen organisms for a chemical reason. despite the availability of other resources, other forms of lifeforms didn't develop for a reason. maybe other forms of life does exist in some methane ocean on Saturn like planets, but its not going to be very complex, and definitely not intelligent life building space ships.

gambiting 5y ago
I'm just always surprised how can we be so certain? Even here on Earth, for millions of years, life was literally nothing more than single cell organisms - also definitely "not intelligent life building space ships". And it would be very hard to see how could it possibly evolve into such, seeing as the atmosphere was full of incredibly toxic oxygen. The thing is, life has almost infinite time to evolve out of these various elements. The fact that it didn't evolve here on Earth means absolutely nothing, seeing as Earth alone has billions of years left where such life could arise, and there are literally countless planets everywhere in the universe where the random dice of evolution roll every second.
- Retric 5y ago
  It’s a question of physics not just chemistry. Deuterium for example is similar to hydrogen chemically so while those differences are slightly toxic to us it’s easy to assume a planet similar to earth with an abundance of deuterium and a lack of hydrogen would evolve life forms with the opposite preferences. Except the ratio of hydrogen to deuterium is a function of astronomy and more specifically fusion. No naturally formed planet is going to end up with that imbalance. Which means no natural deuterium based life forms. So while some alien civilization create deuterium life, it’s not going to be part of natural ecosystems. And so it goes for most possible interesting edge cases. Dependency on rare elements like Neptunium means any competitors without that dependency have huge advantages.

DrBazza 5y ago

This is a theorised list of biochemistry that might support life https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...

rendall 5y ago
Thanks. That's great
Koshkin 5y ago
Nitpick: "bio" = "life"

NotSwift 5y ago

Physics and chemistry impose some serious constraints on all life forms. On earth we have convergent evolution, independent groups of species independently develop similar solutions for a specific problem. Life on other planets will have similar problems, e.g. reproduction, locomotion and perception of its environment, and its solutions will probably be similar to the ones we have on earth.

kenjackson 5y ago
But changes in the environment and initial starting point can result in very different approaches. For example land mammals, reptiles and fish are quite different from each other. Because they've "always been here" we don't appreciate how different they are. Imagine if we had no fish and then found a planet with water that had fish in it -- that would seem absolutely shocking to see animals that could breathe underwater.
- godelski 5y ago
  Honestly this would be pretty hard to imagine. Even if we had no concept of fish (which I find extremely unlikely given other evolutionary pressures, physics, and mechanics of life, but let's not go there) we would think "birds, but in a denser fluid." I don't think this would be "absolutely shocking" to biologists of that planet. Similarly like how biologists here have predicted methane based lifeforms. Now if we were talking about a fluid like sulfuric acid then yeah, that would be absolutely shocking, but not for the reasons of breathing (it's about electrons).
  - state_less 5y ago
    And all these animal/alien minds swim through time like a fish swims through water. Reminds me of that David Foster Wallace joke. > There are these two young fish swimming along, and they happen to meet an older fish swimming the other way, who nods at them and says, “Morning, boys. How’s the water?” And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes, “What the hell is water?” https://www.newyorker.com/books/page-turner/this-is-water https://www.newyorker.com/books/page-turner/this-is-water

yourenotsmart 5y ago

The example of convergence between fish and dolphins, birds and insects, the infamous "why does everything evolve into crabs" study and so on should tell us that while we should be open for radically different forms of life, the most likely outcomes will look like something we've seen here on Earth. I'm personally expecting something like 80% humanoids and 20% exotic forms. Maybe I'm primed incorrectly by cheesy soap operas and sci-fi TV shows, but I think they're not far off (even if for unrelated reasons like SFX/VFX budget and character empathy).

rendall 5y ago
... on planets. That have a precise similarity to Earth. Sure, I can provisionally accept that.
dogorman 5y ago
> convergence between fish and dolphins The convergence between dolphins and ichthyosaurs is even more remarkable. Ichthyosaurs were marine reptiles; air breathing tetrapods that, like dolphins, had ancestors that walked on land but eventually returned to the sea to kick fish ass. https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthyosaur_vs_dolphin.svg https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthy...
- ncmncm 5y ago
  Bony fish evolved in rivers, and eventually returned to the sea to kick... what? Analogies fail. Those fish are overwhelmingly more closely related to horses than to sharks.
mike_hock 5y ago
Sure, organisms that already share a massive amount of commonalities can diverge and then converge again. What about the branches that happened early on? We essentially have only two lineages of macroscopic organisms that are actually fundamentally different: Plants and animals. I would expect any kind of macroscopic extraterrestrial life to be at least as distinct from Terran plant and animal life as they are from each other.

causi 5y ago

Agreed. At a bare minimum, human thought patterns have to be rare. At some point we're either going to murder ourselves or create a Von Neumann machine capable of interstellar flight. After that humans or human-derived machines will fill the universe. Since that obviously hasn't happened with alien machines, the aliens are either not alive or totally unlike us.

cryptoz 5y ago
I don't agree that human thought patterns have to be rare, or your other assumptions. The only safe bet in this discussion I think, is, we don't know anything for sure. > At some point we're either going to murder ourselves or create a Von Neumann machine capable of interstellar flight. There are many, many possibilities for human futures that are between those two and not do extreme. It is absolutely possible we survive millions of years without interstellar travel or self destruction. > Since that obviously hasn't happened with alien machines I also think it is not so obvious that this hasn't happened or isn't happening with alien machines. It certainly could be and we would not know either way. A la 2001: A Space Odyssey, perhaps in fact we are a product of alien machines themselves.
idiotsecant 5y ago
There is a book Accelerando by Charles Stross that talks about why neither case might be true - he shows a scenario where life ultimately transforms its host system into a matrioshka brain. At that point distance from the cloud is reduction in bandwidth to the parts of yourself that exist in that cloud- if the matrioshka brain can simulate billions of planets and leaving it makes you incredibly stupid by your normal standards why do it?
- causi 5y ago
  Accelerando is a great book even if his writing style is a little dry. The mass of one planet being able to simulate billions of planets is only possible if the simulation is rather poor. You can't create a perfect simulation like that any more than you can perfectly simulate seven atoms using three atoms. Computation is never going to be more efficient than physics. why do it? Everyone doesn't have to do it. Just one person out of billions does. Think of the strange and perverse collection of behaviors we observe in a population of a few hundred million people online and speaking English. Expand that to billions of hyperintelligent minds and somebody is going to want to colonize the universe.

alkonaut 5y ago

Of course the environment will determine life forms. What the article says is that if there is a gaseous atmosphere, for example, then selection will reward animals that are able to move through it. That means for organisms that are heavier than the surrounding atmosphere - most likely - wings. For liquid environments, there probably aren’t that many locomotion techniques that are both effective and missing on earth, meaning when we see something swimming in water on a different planet it’ll look like a jellyfish, octopus, fish, worm, clam, bacteria, shrimp, horse… or one of the other hundreds of ways of swimming

rendall 5y ago
Once we move outside Earth-like conditions, we should be decreasingly confident about our speculations, not more confident. What are the chemical and physical conditions of a hydrocarbon lake at 5g, -180C, 1 kilotesla and 100 atmospheres? Can we really be confident that "whale" is the best mechanical solution for moving around there? Can we really be confident that "moving around" would even be the best survival strategy? I think not.
- alkonaut 5y ago
  Indeed earth evolutionary processes require earth like conditions. But here I mentioned swim in water which is a pretty strict constraint on temp vs pressure. That said even in any other fluid I doubt we’ll ever look at an organism and say “it swims like …<blank>“ because there wasn’t an earth organism that swims anything like it. Of course that means comparing to every method of swimming locomotion on earth which is a staggering diversity from the microscopic up to whales. Unless other forces are involved (e.g electromagnetism isn’t used for locomotion on earth to my knowledge) and the fluid is incompressible like water, then I’m (armchair) guessing “to swim” doesn’t have that many evolvable solutions, regardless of pressure/temperature and the specific chemistry.

Koshkin 5y ago

> What creatures would form On the one hand, the conditions under which some lifeforms are thriving here on Earth are already pretty extreme. On the other hand, indeed, we may not yet be in a position to be able to imagine, realistically, all that we would (eventually) agree to call a lifeform. (Life built from phonon "particles" in a planet-size crystal, anyone?) Sure, there may be constraints, such as life, in a meaningful sense, may only be realizable based on polymers, in which case the conditions must be such that they allow polymerization of simple substances to take place.

titzer 5y ago
> On the one hand, the conditions under which some lifeforms are thriving here on Earth are already pretty extreme. Not really. They are all within +/-5km of the planet surface, live under 1g of gravity, as a rule, are not exposed to X-rays, gamma rays, cosmic rays, strong magnetic fields or nuclear radiation, or extreme temperatures. There's nowhere on Earth that receives more than about average solar radiation or gets much above 100C where life survives. Life generally has access to ample oxygen, though a few anaerobic organisms exist. They're all DNA-based, have access to ample amino acids, aren't bathed in thousands of completely toxic chemicals, have liquid water (and not, e.g. liquid methane). The list goes on and on. Yeah, there are a few extremophiles, but they are by far the minority, and are clearly adapted incrementally from other organisms that evolved in non-extremophile environments. In essence, there's a large reservoir of easy-pickins living that generates biodiversity to cross over into extremophile environments. Now imagine 5x the gravity, 100-1000x the solar irradiance, the lack of magnetic field (and thus direct exposure to solar winds), no atmosphere, or atmosphere entirely composed of a toxic gas, extreme exposure to X-rays, etc. The universe is full of many places where Earth life, even extremophiles, would have no chance of survival. And such places don't have reservoirs of biodiversity from which to adapt to these conditions. They're just dead.
- rendall 5y ago
  > They're just dead. We have exactly one example of an environment that nurtures life. It does not logically follow hence that it is the only environment where life can thrive (unless we choose to define life as that which thrives in an Earth-like environment) I do agree that probably most of the Universe is hostile, not only to Earth-like life, but to life of any definition. But we cannot be certain. We have never visited nor sent a probe to a 5g planet "100-1000x the solar irradiance, the lack of magnetic field (and thus direct exposure to solar winds), no atmosphere, or atmosphere entirely composed of a toxic gas, extreme exposure to X-rays".

guyomes 5y ago

> Could we even recognize them as alive, much less intelligent? If we focus on recognizable features, we may look for organisms with self-replication skills (a feature of living organisms) and prediction skills (a feature of intelligent organisms). On the intelligence aspect, the skill to predict the future in general, and imminent threats in particular is useful for structured organisms less resistant than rocks to survive. On that matter I wonder, do unicellular organisms on earth have prediction skills? What also helped those fragile structures to continue existing along rocks after a long time might be their ability to replicate themselves before being destroyed. Reproductive skills might actually be the first interesting feature to look for in extraterrestrial organized structures.

rendall 5y ago
> we may look for organisms with self-replication skills... and prediction skills... Sure, but I imagine this is easier said than done. We 21 c. humans would be most likely to recognize as intelligent life something obviously not a natural feature of the landscape, that operates on a time scale under a year and above a split second or so, that predicts that which we can predict, and most importantly has a form corresponding to Earth creatures. Without ticking all those boxes, especially in a truly strange chemical environment, we will have people asserting that they are a complicated chemical processes, but in no sense alive the way we are alive, if we can even recognize them at all.

acituan 5y ago

> What creatures would form under an intense magnetic field? In methane? In close orbit around a dim star? In a hot cloud nebula? Before the question of what you have the question of if. Then you have the question of continuous constraints. Sensitive dependence on initial conditions still has to operate in a constraint space, and maybe constraints for complex adaptive living systems are much tighter to begin with. Tornados are also sensitive to initial conditions, they are even self organizing, but they are not living beings for example. Imagination is fine when you’re not burdened by starting a working system from first principles. Conceivable sounds probable when you know less about the constraints.

rendall 5y ago
> Before the question of what you have the question of if. Meh. I mean, sure, when all is said and done, everything is constrained by physics and chemistry and imagination has no bearing on this reality. On that we agree, to the point that stating it outright is almost a non-sequitur: a true statement that has no relevance to the discussion at hand. Human culture, in the 400 years of since the first glimmering of the scientific method, has made gigantic leaps in understanding objective truths about our Universe and what lies within it. At every step, highly educated people confidently assert that we know all that is worth knowing and everything henceforth will just be filling in the details. At every step, these assertions have been a failure of imagination. I can confidently state with only historical evidence to go by that our current understanding of the Universe is deeply flawed and will be completely overturned someday. Or if not, it would be because we're just not intelligent enough as a species to do it, and not because we know it all* It is this sense that I mean, when I say that asserting all life throughout the Universe will have forms like those found here, is a failure of the imagination. * Everything that we ever will discover is constrained by the form of our bodies, our evolutionary history, our psychology, and to a lesser degree by our cultural outlook and worldview. There are truths about the universe that are literally forever beyond our discovering because we are incapable of discovering them.** Were we to encounter alien entities that made use of such hypothetically inaccessible principles, especially if their physical forms were based on them in some way, we would literally not understand what we're looking at. ** As an aside, that is my favorite explanation for the Fermi Paradox, that the interstellar cosmos is thrumming with the signs of life and civilization, but we only partly and minimally understand what we're looking at, and so miss these signs.

deleted 5y ago

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