Stories
Slash Boxes
Comments

SoylentNews is people

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.


Original Submission

 
This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (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.