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posted by janrinok on Sunday January 19 2020, @12:31PM   Printer-friendly

Galactic Settlement and the Fermi Paradox:

A spacefaring species could easily settle the entire Milky Way given billions of years. Yet the fact is that there is no obvious one in our solar system right now. The supposed inconsistency between these statements is the Fermi Paradox, named for the Nobel Prize-winning physicist who supposedly first formulated it. In a trenchant formulation of the Fermi Paradox, American astrophysicist Michael H. Hart called the lack of extraterrestrial beings or artifacts on Earth today "Fact A." He showed that most objections to his conclusion—that a spacefaring civilization could have crossed the galaxy by now—stem from either a lack of appreciation for the timescales involved (it takes a small extrapolation from present human technology to get interstellar ships, and even slow ships can star-hop across our galaxy in less time than the galaxy's age) or else the dubious assumption that all members of all extraterrestrial species will avoid colonizing behaviors forever (an example of what I've called the monocultural fallacy).

William Newman and Carl Sagan later wrote a major rebuttal to Hart's work, in which they argued that the timescales to populate the entire galaxy could be quite long. In particular, they noted that the colonization fronts Hart described through the Milky Way might move much more slowly than the speed of the colonization ships if their population growth rates were so low that they only needed to spread to nearby stars very rarely. They also argued that being a long-lived civilization is inconsistent with being a rapidly-expanding one, so any species bent on settling the galaxy would not last long enough to succeed. In other words, they reasoned that the galaxy could be filled with both short-lived rapidly expanding civilizations that don't get very far and long-lived slowly expanding civilizations that haven't gotten very far—either way, it's not surprising that we have not been visited.

Being a long-lived civilization is inconsistent with being a rapidly-expanding one.

In a 2014 paper on the topic, my colleagues and I rebutted many of these claims. In particular, we argued that one should not conflate the population growth in a single settlement with that of all settlements. There is no reason to suppose that population growth, resource depletion, or overcrowding drives the creation of new settlements, or that a small, sustainable settlement would never launch a new settlement ship. One can easily imagine a rapidly expanding network of small sustainable settlements (indeed, the first human migrations across the globe likely looked a lot like this).

Another factor affects Newman and Sagan's numbers on timescales and colonization-front speeds. Most of the prior work on this topic exploits percolation models, in which ships move about on a static two-dimensional substrate of stars. In these models, a star launching settlement ships can quickly settle all of the nearby stars, limiting the number of stars it can settle. But real stars move in three dimensions, meaning that they can carry their orbiting settlements throughout the galaxy, and that a settlement will always have fresh new stars to settle if it waits long enough.

Jonathan Carroll-Nellenback, at the University of Rochester with Adam Frank, not long ago finished work, with Caleb Scharf and me, on analytic and numerical models for how a realistic settlement front would behave in a real gas of stars, one characteristic of the galactic disk at our distance from the galactic center. The big advances here are a few:

Carroll-Nellenback validated an analytic formalism for settlement expansion fronts with numerical models for a realistic gas of stars. He accounted for finite settlement lifetimes, the idea that only a small fraction of stars will be settle-able, and explored the limits of very slow and infrequent settlement ships. He also explored a range of settlement behaviors to see how galactic settlement fronts depend on them.

The idea that not all stars are settle-able is important to keep in mind. Adam Frank calls this the Aurora effect, after the Kim Stanley Robinson novel in which a system is "habitable, but not settle-able."

A very interesting read.


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  • (Score: 1) by szopin on Sunday January 19 2020, @05:12PM (28 children)

    by szopin (5710) on Sunday January 19 2020, @05:12PM (#945380) Homepage Journal

    Like I said CMB is all intergalactic homo-sapiens saying hello, noone cares, we need 25B$ tool to disprove that or realise no matter how many billions we spend we're fucked like the rest

  • (Score: 1) by khallow on Sunday January 19 2020, @05:20PM (27 children)

    by khallow (3766) Subscriber Badge on Sunday January 19 2020, @05:20PM (#945384) Journal
    Sounds like you have an opinion. What's it based on?
    • (Score: 1) by szopin on Sunday January 19 2020, @05:24PM (26 children)

      by szopin (5710) on Sunday January 19 2020, @05:24PM (#945385) Homepage Journal

      On all you drake-equation fetishists, omg multicellular life, omg dinosaurs, omg intelligence, you're planet denylists of our time (like yeah seriously 30 years ago people said our sun was special and there were no planets outside of solar system, how weird haha. this is you)

      • (Score: 1) by khallow on Sunday January 19 2020, @05:38PM (11 children)

        by khallow (3766) Subscriber Badge on Sunday January 19 2020, @05:38PM (#945391) Journal
        So in other words, it's not based on evidence. Cool story, bro, but you're missing the mark. My take is that there is a huge potential to speaking to any intelligent life that has developed under different circumstances. Maybe they solved better the common problems we have and made discoveries that aren't a proper subset of our own. If they live under radically different environmental circumstances, then that can help us (or perhaps our gear) live under those same circumstances. And of course, it would be a data point for those drake-equation fetishists you deride.
        • (Score: 1) by szopin on Sunday January 19 2020, @05:46PM (10 children)

          by szopin (5710) on Sunday January 19 2020, @05:46PM (#945398) Homepage Journal

          >My take is that there is a huge potential to speaking to any intelligent life that has developed under different circumstances. Maybe they solved better the common problems we have and made discoveries that aren't a proper subset of our own. If they live under radically different environmental circumstances, then that can help us (or perhaps our gear) live under those same circumstances.
          Cool story bro, here's NASA take on it:
          pioneer plaque.png
          Two genders, 9 planets, oh and if you squint enough there is some info on how to fight diseases??? Is that what you're trying to sell lol

          • (Score: 1) by khallow on Sunday January 19 2020, @05:48PM (9 children)

            by khallow (3766) Subscriber Badge on Sunday January 19 2020, @05:48PM (#945400) Journal

            Is that what you're trying to sell lol

            Nope. If I were communicating, it'd be more than just an engraved disk worth of knowledge.

            • (Score: 1) by szopin on Sunday January 19 2020, @05:52PM (8 children)

              by szopin (5710) on Sunday January 19 2020, @05:52PM (#945402) Homepage Journal

              Yeah like what exactly? Can you give us an example what people of earth could send without getting raped for it 40 years later and thinking about cosmic scales? 2 genders and 9 planets ain't it my friend, think of something more inclusive, but you'll end up a bigot anyway, so have fun

              • (Score: 1) by khallow on Sunday January 19 2020, @06:12PM (7 children)

                by khallow (3766) Subscriber Badge on Sunday January 19 2020, @06:12PM (#945409) Journal
                Wikipedia, for example.
                • (Score: 1) by szopin on Sunday January 19 2020, @06:18PM (6 children)

                  by szopin (5710) on Sunday January 19 2020, @06:18PM (#945411) Homepage Journal

                  Is this a joke? Maybe a wikipedia history of any problematic article?

                  • (Score: 1) by khallow on Monday January 20 2020, @01:29AM (5 children)

                    by khallow (3766) Subscriber Badge on Monday January 20 2020, @01:29AM (#945593) Journal
                    If Wikipedia is a joke, they've been pulling the wool over our eyes for a generation.
                    • (Score: 1) by szopin on Monday January 20 2020, @02:41AM

                      by szopin (5710) on Monday January 20 2020, @02:41AM (#945616) Homepage Journal

                      And yet every professor tells you to treat wikipedia with a huge grain of salt, he surely got his wool pulled off

                    • (Score: 1) by szopin on Monday January 20 2020, @02:43AM (3 children)

                      by szopin (5710) on Monday January 20 2020, @02:43AM (#945619) Homepage Journal

                      OMG wait you want to send wikipedia to other civilizations>>????? lol sure go ahead pls send them articles with history like palestine and jesus, go fucking do it

                      • (Score: 1) by khallow on Monday January 20 2020, @04:51AM (2 children)

                        by khallow (3766) Subscriber Badge on Monday January 20 2020, @04:51AM (#945663) Journal
                        Sounds like you think there might be a problem in there somewhere. I also don't see the point in making human history look pretty to outsiders.
                        • (Score: 1) by szopin on Monday January 20 2020, @05:14AM (1 child)

                          by szopin (5710) on Monday January 20 2020, @05:14AM (#945672) Homepage Journal

                          Yeah like literally sending other civilizations 'khallow' would be a shitty idea, but some (khallow) will push for it, no dude you are not a good idea for first contact

                          • (Score: 1) by khallow on Monday January 20 2020, @03:16PM

                            by khallow (3766) Subscriber Badge on Monday January 20 2020, @03:16PM (#945845) Journal
                            I noticed a few posts in that you lost a lot of coherency. You're just not thinking - and certainly not telling us what little you are thinking.

                            Here, why make some special information package for aliens, when we've already spent almost twenty years (and far more man-years than you can imagine) making a package for us? What's the problem? Is it a matter of security? We could sanitize military data out of the mix, if that's a problem. Is it inaccuracy? We could filter out the latest level of trolling and otherwise stick in a warning that there are biases present and the nature of these will change as the content changes. Even that would be very informative to an alien species.
      • (Score: 2) by PartTimeZombie on Sunday January 19 2020, @09:27PM (13 children)

        by PartTimeZombie (4827) on Sunday January 19 2020, @09:27PM (#945468)

        (like yeah seriously 30 years ago people said our sun was special and there were no planets outside of solar system, how weird haha. this is you)

        This is wrong. As soon as we discovered that other stars are just like ours, we realised there could be planets orbiting them.

        • (Score: 1) by szopin on Sunday January 19 2020, @09:55PM (12 children)

          by szopin (5710) on Sunday January 19 2020, @09:55PM (#945489) Homepage Journal

          And yet as soon we realised life happened 1 bil year on earth, we are still debating life outside of earth

          • (Score: 2) by PartTimeZombie on Sunday January 19 2020, @10:10PM (11 children)

            by PartTimeZombie (4827) on Sunday January 19 2020, @10:10PM (#945498)

            No-one is debating whether life outside our solar system is possible, it quite obviously is.

            What we are doing is actively looking for it. We haven't found it yet, but it is early days, and we're not putting much effort in are we?

            • (Score: 1) by szopin on Sunday January 19 2020, @10:37PM (6 children)

              by szopin (5710) on Sunday January 19 2020, @10:37PM (#945508) Homepage Journal

              >What we are doing is actively looking for it
              lol, so untrue, you had an experiment in 70s that said yes, life on mars, what did NASA do? Send a follow up? Noooope, why even bother, jesus is great

              • (Score: 2) by PartTimeZombie on Sunday January 19 2020, @11:08PM

                by PartTimeZombie (4827) on Sunday January 19 2020, @11:08PM (#945529)

                you had an experiment in 70s that said yes, life on mars

                Citation Required.

                Have a wee look at this. [nasa.gov] It is a start, even if we're not putting much effort in, as I said.

              • (Score: 1) by khallow on Monday January 20 2020, @05:00AM (4 children)

                by khallow (3766) Subscriber Badge on Monday January 20 2020, @05:00AM (#945666) Journal

                lol, so untrue, you had an experiment in 70s that said yes, life on mars, what did NASA do?

                NASA has been pretty shitty in what it's done over the decades, but even they have done more than a dozen missions [wikipedia.org] in that 40 years span. And yes, that's Wikipedia.

                Too bad that so many missions don't mean a thing to you because they didn't stick a labeled-release experiment on them.

                • (Score: 1) by szopin on Monday January 20 2020, @05:12AM (3 children)

                  by szopin (5710) on Monday January 20 2020, @05:12AM (#945670) Homepage Journal

                  >Too bad that so many missions don't mean a thing to you because they didn't stick a labeled-release experiment on them.

                  You seem to be angry about ignoring nasa, but also want to praise nasa for their experiment? Can you make up your fucking mind please?

            • (Score: 1) by szopin on Sunday January 19 2020, @10:55PM (3 children)

              by szopin (5710) on Sunday January 19 2020, @10:55PM (#945517) Homepage Journal

              >What we are doing is actively looking for it.

              cope, NASA has still not followed up on labeled release, but we're actively looking, nope

              • (Score: 2) by PartTimeZombie on Sunday January 19 2020, @11:10PM (2 children)

                by PartTimeZombie (4827) on Sunday January 19 2020, @11:10PM (#945533)

                Is there any chance you could write in sentences, and use proper words? It will make your comments easier to understand.

                • (Score: 0) by Anonymous Coward on Monday January 20 2020, @01:03AM (1 child)

                  by Anonymous Coward on Monday January 20 2020, @01:03AM (#945582)

                  A few more replies to get the all time record on reply indentation

                  • (Score: 2) by gtomorrow on Monday January 20 2020, @07:16AM

                    by gtomorrow (2230) on Monday January 20 2020, @07:16AM (#945705)

                    I'M IN!!!

                    (Beats reading Abbott and Costello here bantering back and forth.)