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> I think the odds of a planet developing life by random chance in the first place is astronomical, and then the odds of that developing into intelligent life -

> I think the odds of a planet developing life by random chance in the first place is astronomical, and then the odds of that developing into intelligent life - that happens to have the necessary appendages to build things and lives in an environment amenable to creating tech - almost certainly an astronomically small portion of life bearing planets. I take your point, but even if it is true that life is astronomically rare, we are literally talking about astronomy. Life doesn't have to be common for there to be countless worlds with life in our galaxy. In terms of intelligent life, not only must we reckon with the billions upon billions of planets in this galaxy that could host it, but there are also the vast timescales in which it could unfold. Based on the current trajectory of human civilization, I think the Great Filter [1] theory is increasingly convincing, although that's unfortunate (to put it lightly). If we do manage to avoid destroying ourselves in a sudden cataclysm (such as via nuclear war), we will have to deal with a planet with a destabilized atmosphere, a massively damaged ecosystem, poisoned water and a host of other problems so serious that the word "problem" doesn't seem sufficient. The timescales required for other advanced technological civilizations to overlap with our own requires that civilizations that go through these periods are able to stop actively destroying their home planet, and then survive the aftermath for a long time afterwards. Whether we are able to do this is very much an open question. We are just a couple of centuries down this road and on balance, I don't think it's going that well. 1: https://en.wikipedia.org/wiki/Great_Filter https://en.wikipedia.org/wiki/Great_Filter

ethbr0 4y ago
Based on our own experience, we know of at least three Filters and can strongly guess as to another. (1) That life develops on a world whose mass allows achieving orbital spaceflight using relatively low-technology means (i.e. at least partially chemical) (2) That advanced life develops on a world with massive energy reserves easily accessible with low technology (e.g. coal, oil) (3) That no environmental cataclysm occurs during the advanced life/industrialization gestation time period (e.g. climate change, asteroid) To this, we can pretty strongly add another: (X) That, during the brief window between energy surplus (and advanced technology) and environmental collapse (from energy exploitation), interplanetary colonization is launched, supported, and made self-sufficient There's no law that says the window for something remains open forever, when you're talking about planet-scale economic requirements.
- jablongo 4y ago
  Another major filter supposedly comes much earlier: the development of complex single celled eukaryotic life. Some people think this occurred due to a single subsumption event on earth between a bacteria and an archaea.
  - overspeed 4y ago
    > single subsumption event on earth between a bacteria and an archaea. Do you mean symbiogenesis? https://en.m.wikipedia.org/wiki/Symbiogenesis https://en.m.wikipedia.org/wiki/Symbiogenesis
    - jablongo 4y ago
      Yes that’s the word
- awb 4y ago
  There’s probably also a distance / lifespan filter: (4) That interplanetary colonization is possible (using relatively low-tech means) given the lifespan of the species and the distance to nearby habitable planets. For example, life could develop in a solar system with only 1 habitable planet and the next habitable solar system could be dozens or hundreds of light years away. Now you need to invent a fully self-sustaining long haul space craft, plus have the technology to pause death (or have the will to confine hundreds or thousands of generations to life on a space craft, plus have the ability to effectively pass down enough survival skill information from generation to generation that won’t use it, but will simply practice it in order to relay it).
  - dylan604 4y ago
    >For example, life could develop in a solar system with only 1 habitable planet and the next habitable solar system could be dozens or hundreds of light years away. Did you just describe our solar system?
  - midoridensha 4y ago
mathlover2 4y ago
Basing hypotheses on a single data point, let alone one whose outcome is not yet determined, almost invariably leads to wildly inaccurate conclusions in practice. As such, until we have more data, any questions about the Great Filter and the causes thereof will remain unanswerable. Personally my bet is on either us being early as intelligent life goes, or extremely massive stellar expansionism on the levels that would allow for us to have encountered intelligent life with basically zero search effort not being something most civilizations would feel compelled to do. Also assuming that any advanced civilization that exists would have to follow our development path is laughably anthropocentric and reflects a failure of imagination on the part of the people making said claims.
- adriand 4y ago
  > Also assuming that any advanced civilization that exists would have to follow our development path is laughably anthropocentric and reflects a failure of imagination on the part of the people making said claims. That's a great point, and it's not just anthropomorphic. It also ignores the paths that other cultures were on, that were subsumed or annihilated by Western-style industrial capitalism. What would human civilization look like (and what state would the planet be in) if, for instance, Western nations had first, respected indigenous sovereignty in the Americas, and second, sought to learn from First Nations instead of seeking to destroy them? In other words, we don't have to imagine alien civilizations to explore other developmental paths. There are plenty of examples right here at home.
  - midoridensha 4y ago
    I'm guessing that if Europeans had decided to adopt the Native American lifestyles and cultures, we would still be pre-industrial and living as a bunch of separate tribes that sometimes have wars between them. The way the European settlers treated the natives was indeed rather shabby, but the existing culture was not one that could ever develop into modern nation-states and a global industrial civilization without conflict. And without industrial capitalism, we wouldn't have computers and be exchanging messages across continents here on HN. So it's entirely possible there's alien civilizations out there that are happy to remain in a primitive, tribal, pre-industrial state, but we're not going to ever detect or meet those civilizations until we have starships capable of transporting us there.
BiteCode_dev 4y ago
Agreed, but remember we likely see the universe with massive blind spots. Maybe given enough time, an aquatic specie would find a way to make tech, manipulate energy and develop society in ways that require a physic we know nothing about. Or maybe using something we know, but could not think of using that way because of our biases. We are a very young civilization after all, the quantity of things we don't know is massive.

ethbr0 4y ago

Based on our own experience, we know of at least three Filters and can strongly guess as to another. (1) That life develops on a world whose mass allows achieving orbital spaceflight using relatively low-technology means (i.e. at least partially chemical) (2) That advanced life develops on a world with massive energy reserves easily accessible with low technology (e.g. coal, oil) (3) That no environmental cataclysm occurs during the advanced life/industrialization gestation time period (e.g. climate change, asteroid) To this, we can pretty strongly add another: (X) That, during the brief window between energy surplus (and advanced technology) and environmental collapse (from energy exploitation), interplanetary colonization is launched, supported, and made self-sufficient There's no law that says the window for something remains open forever, when you're talking about planet-scale economic requirements.

jablongo 4y ago
Another major filter supposedly comes much earlier: the development of complex single celled eukaryotic life. Some people think this occurred due to a single subsumption event on earth between a bacteria and an archaea.
- overspeed 4y ago
  > single subsumption event on earth between a bacteria and an archaea. Do you mean symbiogenesis? https://en.m.wikipedia.org/wiki/Symbiogenesis https://en.m.wikipedia.org/wiki/Symbiogenesis
  - jablongo 4y ago
    Yes that’s the word
awb 4y ago
There’s probably also a distance / lifespan filter: (4) That interplanetary colonization is possible (using relatively low-tech means) given the lifespan of the species and the distance to nearby habitable planets. For example, life could develop in a solar system with only 1 habitable planet and the next habitable solar system could be dozens or hundreds of light years away. Now you need to invent a fully self-sustaining long haul space craft, plus have the technology to pause death (or have the will to confine hundreds or thousands of generations to life on a space craft, plus have the ability to effectively pass down enough survival skill information from generation to generation that won’t use it, but will simply practice it in order to relay it).
- dylan604 4y ago
  >For example, life could develop in a solar system with only 1 habitable planet and the next habitable solar system could be dozens or hundreds of light years away. Did you just describe our solar system?
- midoridensha 4y ago

mathlover2 4y ago

Basing hypotheses on a single data point, let alone one whose outcome is not yet determined, almost invariably leads to wildly inaccurate conclusions in practice. As such, until we have more data, any questions about the Great Filter and the causes thereof will remain unanswerable. Personally my bet is on either us being early as intelligent life goes, or extremely massive stellar expansionism on the levels that would allow for us to have encountered intelligent life with basically zero search effort not being something most civilizations would feel compelled to do. Also assuming that any advanced civilization that exists would have to follow our development path is laughably anthropocentric and reflects a failure of imagination on the part of the people making said claims.

adriand 4y ago
> Also assuming that any advanced civilization that exists would have to follow our development path is laughably anthropocentric and reflects a failure of imagination on the part of the people making said claims. That's a great point, and it's not just anthropomorphic. It also ignores the paths that other cultures were on, that were subsumed or annihilated by Western-style industrial capitalism. What would human civilization look like (and what state would the planet be in) if, for instance, Western nations had first, respected indigenous sovereignty in the Americas, and second, sought to learn from First Nations instead of seeking to destroy them? In other words, we don't have to imagine alien civilizations to explore other developmental paths. There are plenty of examples right here at home.
- midoridensha 4y ago
  I'm guessing that if Europeans had decided to adopt the Native American lifestyles and cultures, we would still be pre-industrial and living as a bunch of separate tribes that sometimes have wars between them. The way the European settlers treated the natives was indeed rather shabby, but the existing culture was not one that could ever develop into modern nation-states and a global industrial civilization without conflict. And without industrial capitalism, we wouldn't have computers and be exchanging messages across continents here on HN. So it's entirely possible there's alien civilizations out there that are happy to remain in a primitive, tribal, pre-industrial state, but we're not going to ever detect or meet those civilizations until we have starships capable of transporting us there.

BiteCode_dev 4y ago

Agreed, but remember we likely see the universe with massive blind spots. Maybe given enough time, an aquatic specie would find a way to make tech, manipulate energy and develop society in ways that require a physic we know nothing about. Or maybe using something we know, but could not think of using that way because of our biases. We are a very young civilization after all, the quantity of things we don't know is massive.