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

  1. #1321
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    Quote Originally Posted by 7cscb View Post
    And, regardless, we will likely expel much mass in our interstellar travels, which is not Closed.
    Mass expelled from an interstellar vessel will be propellant, not from the life supporting biosphere. A separate system entirely. We don't use the breathing oxygen inside an airplane cabin to run the jets.

    Now, any sealed chamber is imperfect. There will be some material losses from inside the starship biosphere, that's inevitable, and replacement volatiles will have to be carried. But the more closure the builders can achieve, the better for life supporting purposes. So they'll aim high.

    For an orbital habitat replenishment is easier, because there's asteroids and comets to mine, but high degrees of closure of the internal material cycles is still a significant goal, especially as the habitats are being established.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  2. #1322
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    Even with VERY conservative assumptions the galaxy fills within one eon:
    https://www.centauri-dreams.org/2021...ic-settlement/
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  3. #1323
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    Quote Originally Posted by Tom Mazanec View Post
    Even with VERY conservative assumptions the galaxy fills within one eon:
    https://www.centauri-dreams.org/2021...ic-settlement/
    Zero is a conservative estimate

    I have already discussed here why I don't believe the colonize-a-whole-galaxy scenario is plausible, let alone a default assumption. A number of posters have come back with "but it only takes one!". My response is, it only takes none to explain what we see. We know we have not detected any technosignatures; Occam's old saw says "there's no technosignatures to find" would be the most likely reason for that.

    IF there's another species with minds, and IF they do get out of their home star system, there's still no particular reason to settle every single star in any galaxy. Yes, "life spreads"... in nature. But by definition a civilization that achieves star travel is an artificial construct that does things on purpose, they need not stick to blind imperatives.

    Also, life growing in a glacier or desert sand does not need to expend massive amounts of energy to adapt; but the physics of relativity and motion necessitate that all forms of interstellar travel will require the commitment of vast power and resources. Especially in-person travel with the intent to colonize. That's always going to be expensive, probably even to a star-system-wide economy.

    A generation ship or "slowboat" would be cheaper in energy but basically require a portable civilization. That also seems like a nontrivial commitment of resources. Either way, fast or slow, it's not ever going to be something a society does casually or without good cause at any tech level. And it almost certainly won't be a priority for a colony system still bootstrapping its industries.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  4. #1324
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    Quote Originally Posted by Noclevername View Post
    Zero is a conservative estimate

    I have already discussed here why I don't believe the colonize-a-whole-galaxy scenario is plausible, let alone a default assumption. A number of posters have come back with "but it only takes one!". My response is, it only takes none to explain what we see. We know we have not detected any technosignatures; Occam's old saw says "there's no technosignatures to find" would be the most likely reason for that.
    Agreed.
    Stepping even further into the evidence-based speculative realm, (for unclear reasons), one can argue that 'aliens' actively attempting to attain the goal of visiting/reaching/making contact with Earth, firstly requires their detecting the existence of the Earth from their light-year distance viewpoints.

    There are seven star systems that can detect Earth transiting the Sun, (ie: the 'Earth Transit Zone'), which are themselves, known to host one or more exoplanets.
    Given the possibility that there may be more systems having exoplanets which we haven't yet detected, there are 1,715 star-systems known, which could have possibly 'spotted' Earth's so-called 'bio-/techno-signatures', since human civilization took off (about 5,000 years ago).

    Over the past 10,000-year period, 117 objects are known to have been within about 100 light-years of the Sun and 75 of these objects have been in the 'Earth Transit Zone' since commercial radio stations on Earth began broadcasting into space, about a century ago.

    This post is more a reality check on the current state of closer-to-fact based knowledge and, along with the fact of the lack of detected technosignatures to date, could be used for useful statistical estimation type discussions.
    It will be interesting to monitor the development of this closer-to-fact based knowledge set, as I think it is unlikely to dramatically change over our not too distant future (JWST observations notwithstanding .. maybe).

    Reference:
    Past, present and future stars that can see Earth as a transiting exoplanet

    Video here.

  5. #1325
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    Quote Originally Posted by Selfsim View Post
    Agreed.
    Stepping even further into the evidence-based speculative realm, (for unclear reasons), one can argue that 'aliens' actively attempting to attain the goal of visiting/reaching/making contact with Earth, firstly requires their detecting the existence of the Earth from their light-year distance viewpoints.
    Unless they had sent out probes and/or colonists that had reached nearer or more angled stars, giving a broader view.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  6. #1326
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    Quote Originally Posted by Noclevername View Post
    Unless they had sent out probes and/or colonists that had reached nearer or more angled stars, giving a broader view.
    .. adds more untested hypotheticals .. relies solely on theory and lacks demonstrations of practical feasibility.

  7. #1327
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    Quote Originally Posted by Selfsim View Post
    .. adds more untested hypotheticals .. relies solely on theory and lacks demonstrations of practical feasibility.
    Space probes lack demonstration of practical feasibility? Yeah, sure. Interstellar space probes are obvious technological extrapolation over current human demonstrated capability, no new physics needed. Whether there are ETs to send them is the question.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." Abraham Lincoln

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  8. #1328
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    Quote Originally Posted by Van Rijn View Post
    ... Interstellar space probes are obvious technological extrapolation over current human demonstrated capability, ..
    Obvious or not, 'technological extrapolations' ​are untested predictions projected from hypotheses.

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