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Thread: What do you think is the most likely explanation for the Fermi paradox?

  1. #1381
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    Quote Originally Posted by Noclevername View Post
    ADDED: Yes, a whole star system is pretty unlikely to fill up in less than geological time. But all the accessible low hanging fruit can be monopolized, leaving outsiders only regions where resources are scattered.
    I wouldn’t assume that. It depends on how difficult it is to build habitats and if there is exponential growth. Compare the US of today with the land a few centuries ago. With a modest growth rate it would only take a few centuries for the solar system to have a population in the hundreds of trillions.

    This is why I’ve said exponential growth simply can’t continue for long compared to the age of the galaxy, regardless of psychology or other factors, but just assuming finite resources. A species must be able to learn to control its population in a relatively short period or will face collapse.
    Last edited by Van Rijn; 2021-Jul-05 at 08:07 AM. Reason: Typo

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    Quote Originally Posted by Jens View Post
    On the other hand, the issue for me is that when you talk about a seed falling into a new field, it is basically in an area where the seed can naturally grow (for example, if you drop it at the south pole, it is unlikely to proliferate). But if we're talking about the expansion of ET civilizations into space, it seems unlikely (maybe you wouldn't agree) that they would be naturally adapted to the various places they go, and would not require building an infrastructure to allow them to survive.
    I wouldn’t agree. As hunter-gatherers, with minimal technology and no attempt to modify the environment to suit us, humans could have a world population of about 50 million at maximum (that’s from material I remember from an old university course). We can only have such populations and live in so many places today because we alter conditions to suit us. Tomorrow, we will build habitats on Mars and elsewhere to live. Today that would be difficult, but as technology advances it will become easier.

    I would expect technological ETs to do similar things, building habitats they can live in where it would otherwise be unsuitable.

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  3. #1383
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    Quote Originally Posted by Jens View Post
    Yeah, it's true that this thread seems to be in a kind of long derail where we're talking about the growth of human civilizations (like the Romans), and it's a bit irrelevant to the question of the paradox.

    On the other hand, the issue for me is that when you talk about a seed falling into a new field, it is basically in an area where the seed can naturally grow (for example, if you drop it at the south pole, it is unlikely to proliferate). But if we're talking about the expansion of ET civilizations into space, it seems unlikely (maybe you wouldn't agree) that they would be naturally adapted to the various places they go, and would not require building an infrastructure to allow them to survive.
    Of course it would require them to build an infrastructure, that's a base assumption. Perhaps the problem is, we may have different ways to visualize what an interstellar colonization is.

    My view is that interstellar travel is not really plausible for a civilization that has a mainly one-world industrial infrastructure. It would take a great deal of skill in building long term life support and the resources of a developed space construction industry to build a viable starship, in addition to the propulsion technology. So any group capable of colonizing another star already would have significant field experience in building their own life supporting habitats, or why go at all? Certainly the odds of finding, let alone surviving on, a natural planet suited to your kind of life are slim to none.

    I believe any society than can survive a trip to another star can also live without planets. They'd thrive in the materials and energy of a new star system. And if they can build themselves one habitat they'll eventually build many and spread to other parts of the system, just as they did in the original one. Perhaps even terraform a suitable terrestrial planet or moon, but that's not a necessity.
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    Quote Originally Posted by Van Rijn View Post
    I wouldn’t assume that. It depends on how difficult it is to build habitats and if there is exponential growth.
    You're right, of course. I did not mean to imply an exponential population growth, just a more than break-even.

    Resources are not evenly distributed in any star system. Some space bodies are "better" than others; have more volatiles or strategic elements, be in orbits more conducive to travel/transport, need less delta-V to lift off, etc. These would most likely become the major hubs outside the species' home planet. The holders of those prime locations would have advantages in population growth rates than those at the less suitable rocks and moons.

    So that's what I meant by the low hanging fruit. It would not take trillions of beings to reach that point; only for groups in competition for the easy-access objects. Even a more cooperative society than ours would have trouble distributing resources equitably simply due to the conditions in space. Getting stuff anywhere uses up energy and materials (even to make solar sails, etc) so some places would have more or less no matter the level of technology.
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    A recent discovery of smaller rogue planets by microlensing. https://academic.oup.com/mnras/artic...4/5584/6315707

    If interstellar space is littered with such masses, then it may be more "crowded" on smaller scales than we first figured. That might make interstellar travel even more hazardous and difficult than we currently envision, not only in terms of relativistic collision with matter, but in navigational complexity from undetected gravity sources. Another possible braking mechanism on exponential Galactic expansion.
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    Interstellar dust shows planets with composition like Earth may form rarely: https://phys.org/news/2021-07-astron...ins-milky.html

    "Our solar system was formed in the outer regions of the galaxy and is the result of a complex sequence of events, including nearby supernova explosions. It remains an open question what is the right environment to form planetary systems and which of these events are vital to form a planet where life can flourish."
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    Quote Originally Posted by profloater View Post
    It is possible that intelligent life operates on a shorter timescale toward self extinction than non intelligent life that is forced to fit in with many other species. Intelligent life overcomes negative feedback mechanisms and thus does more damage ensuring a final collapse. The history of Easter Island is a miniature example. When clever people navigated there it was covered in palm trees with millions of birds. The clever people cut down the trees, made clever giant statues, killed all the birds, and trapped themselves, unable to make the kind of boats their ancestors arrived in. They expanded, used up all resources and died off. In other words, the very attributes that confer success are likely to lead to total exploitation. Not a new argument, I admit. Malthus.
    So it seems the consensus is that Easter Island's fate was not entirely the fault of Rapa Nui society:

    https://phys.org/news/2021-07-resili...land-myth.html

    In short, there is no evidence that the islanders used the now-vanished palm trees for food, a key point of many collapse myths. Current research shows that deforestation was prolonged and didn't result in catastrophic erosion; the trees were ultimately replaced by gardens mulched with stone that increased agricultural productivity. During times of drought, the people may have relied on freshwater coastal seeps.

    Construction of the moai statues, considered by some to be a contributing factor of collapse, actually continued even after European arrival.

    In short, the island never had more than a few thousand people prior to European contact, and their numbers were increasing rather than dwindling, their research shows.
    The original paper:

    https://www.nature.com/articles/s41467-021-24252-z
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  8. #1388
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    There is no paradox.
    We have no idea how likely life is, no matter what presumptions you decide on.
    It is maybe more pertinent to consider how blind we are.
    Last edited by alromario; 2021-Sep-18 at 12:46 AM.

  9. #1389
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    Quote Originally Posted by alromario View Post
    There is no paradox.
    We have no idea how likely life is, no matter what presumptions you decide on.
    It is maybe more pertinent to consider how blind we are.
    I'm gonna guess that the Fermi Paradox not being a paradox has been brought up previously.

    Here's an explanation from SciAm:
    https://blogs.scientificamerican.com...not-a-paradox/

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    One of my favourite explanations of the Fermi paradox is written by Cixin Liu in his book "The Dark Forest". He says: “The universe is a dark place indeed. Luo Ji moved his hand, feeling the darkness like velvet. - The universe is a dark forest. Each civilization is a hunter armed to the teeth, sliding between trees as a ghost, unnoticeably taking branches aside and trying to step silently. He even breathes every other time. The hunter has something to fear: the forest is full of other invisible hunters, just like himself. If he meets life - another hunter, an angel or a devil, a newborn baby or an old ruin, a fairy or a demigod - he has only one way out: to open fire and destroy. In this forest, other people are hell. Any life is a mortal threat to everyone else and will be destroyed at the earliest opportunity. This is what a space civilization looks like. And this explains the Fermi paradox."

  11. #1391
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    Quote Originally Posted by ChrisDecrow View Post
    One of my favourite explanations of the Fermi paradox is written by Cixin Liu in his book "The Dark Forest". He says: “The universe is a dark place indeed. Luo Ji moved his hand, feeling the darkness like velvet. - The universe is a dark forest. Each civilization is a hunter armed to the teeth, sliding between trees as a ghost, unnoticeably taking branches aside and trying to step silently. He even breathes every other time. The hunter has something to fear: the forest is full of other invisible hunters, just like himself. If he meets life - another hunter, an angel or a devil, a newborn baby or an old ruin, a fairy or a demigod - he has only one way out: to open fire and destroy. In this forest, other people are hell. Any life is a mortal threat to everyone else and will be destroyed at the earliest opportunity. This is what a space civilization looks like. And this explains the Fermi paradox."
    If it's literally true that "any life is a mortal threat to everyone else and will be destroyed at the earliest opportunity", then why wasn't life on Earth destroyed long ago by extraterrestrials?

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    Quote Originally Posted by Colin Robinson View Post
    If it's literally true that "any life is a mortal threat to everyone else and will be destroyed at the earliest opportunity", then why wasn't life on Earth destroyed long ago by extraterrestrials?
    Yep, I think of it as the paranoid aliens hypothesis. It is often brought up as an argument against active SETI (deliberate transmissions intended to be readable at interstellar distances). The issue is that there are ways to detect habitable worlds, something we are just beginning ourselves, without relying on detection of radio or other signs of technology. Paranoid aliens should be expected to wipe out any such as they could eventually develop into a threat. Since we are still here, it argues against any nearby interstellar capable paranoid aliens.

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  13. #1393
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    Quote Originally Posted by Van Rijn View Post
    Yep, I think of it as the paranoid aliens hypothesis. It is often brought up as an argument against active SETI (deliberate transmissions intended to be readable at interstellar distances). The issue is that there are ways to detect habitable worlds, something we are just beginning ourselves, without relying on detection of radio or other signs of technology. Paranoid aliens should be expected to wipe out any such as they could eventually develop into a threat. Since we are still here, it argues against any nearby interstellar capable paranoid aliens.
    It argues against aliens so paranoid and so powerful that they will destroy any life they detect.

    However, isn't it still conceivable that they have a more nuanced paranoia — that they only destroy life that annoys them with interstellar radio spam?
    Last edited by Colin Robinson; 2021-Sep-28 at 04:49 AM.

  14. #1394
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    Quote Originally Posted by Colin Robinson View Post
    It argues against aliens so paranoid and so powerful that they will destroy any life they detect.

    However, isn't it still conceivable that they have a more nuanced paranoia — that they only destroy life that annoys them with interstellar radio spam?
    If they are paranoid, by waiting until they detect a radio signal, and given the time it would take to detect and especially to mount a response, they would have to consider that the species they find could easily be technologically too advanced to destroy and spread out from its original planet by the time they get there. Even if the target species wasn’t interested in an interstellar war originally, if they are attacked and survive they now have a good reason to retaliate. By waiting for a radio signal to attack, the paranoid species significantly increases its risk.

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    Quote Originally Posted by Van Rijn View Post
    If they are paranoid, by waiting until they detect a radio signal, and given the time it would take to detect and especially to mount a response, they would have to consider that the species they find could easily be technologically too advanced to destroy and spread out from its original planet by the time they get there. Even if the target species wasn’t interested in an interstellar war originally, if they are attacked and survive they now have a good reason to retaliate. By waiting for a radio signal to attack, the paranoid species significantly increases its risk.
    Yes, they would increase their risk by waiting for a radio signal.

    And the increased risk might seem very significant to them. But that would depend on factors like

    * how long it would take them to detect radio signals from the target species,
    * how long it would take them to mount their response,
    * how long they think it would take for the target species to get from ability to use radio, to ability to wage an interstellar war.

    On the other hand, if they didn't wait for a radio signal, if they attacked every planet where they detected any form of life, mightn't they increase their costs significantly, even prohibitively?

    Especially if

    * there are many life-bearing planets which never develop the sort of technology that could potentially harm beings lightyears away.
    * and they've studied life in the galaxy thoroughly enough to be aware of that.
    Last edited by Colin Robinson; 2021-Oct-02 at 10:49 AM.

  16. #1396
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    And killing every life bearing planet they find would increase their own exposure, make them more likely to be detected by other species that make a point of killing species that run around killing every life bearing planet they find.

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    I don't know or didn't look but an old proverb when I was taking computer classes "garbage in garbage out".

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    Quote Originally Posted by Darrell View Post
    And killing every life bearing planet they find would increase their own exposure, make them more likely to be detected by other species that make a point of killing species that run around killing every life bearing planet they find.
    Yes, that's another problem with the "dark forest" idea, another problem with the theory that technically advanced civilisations are likely to kill any interstellar neighbours they discover.
    Last edited by Colin Robinson; 2021-Oct-06 at 06:11 AM.

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    The dark forest metaphor ignores the unintended harm that might precede intention. Bacteria funguses and viruses seem likely to precede intelligent space craft into space. The universal large distance problem still dominates, but some of these tiny life packets might survive far longer than multicellular animals. The long evolutionary battle between complex and simple life forms can not be pushed aside in making any hypothesis about alien life. This is a different dark forest where contact with single cells or with DNA can have positive or negative effects. In this dark forest we cannot even know , on Earth, whether contact has already been made!
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    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
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  20. #1400
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    Of course Earth is special to us Earthlings, and we Earthlings are special to ourselves...

    Maybe the nearest extraterrestrials think otherwise.

    Maybe, to them, neither Earth nor its inhabitants are special enough to be worth either contacting or attacking...

  21. #1401
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    Quote Originally Posted by ChrisDecrow View Post
    One of my favourite explanations of the Fermi paradox is written by Cixin Liu in his book "The Dark Forest". He says: “The universe is a dark place indeed. Luo Ji moved his hand, feeling the darkness like velvet. - The universe is a dark forest. Each civilization is a hunter armed to the teeth, sliding between trees as a ghost, unnoticeably taking branches aside and trying to step silently. He even breathes every other time. The hunter has something to fear: the forest is full of other invisible hunters, just like himself. If he meets life - another hunter, an angel or a devil, a newborn baby or an old ruin, a fairy or a demigod - he has only one way out: to open fire and destroy. In this forest, other people are hell. Any life is a mortal threat to everyone else and will be destroyed at the earliest opportunity. This is what a space civilization looks like. And this explains the Fermi paradox."
    Hello ChrisDecrow and belated welcome,

    I don't buy that explanation for two reasons.

    First, as an example, take humanity. While many incorrectly dread our radio broadcasts as giveaways to our existence, life on Earth has been glaringly obvious for any advanced technological civilization to detect for 100s of millions of years, if not billions. As our telescopes continue improving this is how we will first discover life, if it is there to be found. Our discernment of exoplanets will continue to grow. There is no reason to believe Earth would not stick out like a sore thumb, this only mitigated by life existing everywhere but that does not seem to be the case.

    Second, technological civilizations use power. There is no way to hide the resultant excess of heat. In a sparsely inhabited universe, one could imagine a race hiding specifically from us by diverting power usage heat in other directions. Meh.

    Cheers,

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