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Stars in the Milky Way galaxy

Colonizing the Galaxy by Hitching a Ride with Stars

“Where is everybody?” That is the famous question about alien life posed by physicist Enrico Fermi (see: the Fermi Paradox): why have we not found evidence of extraterrestrial civilizations, given the likelihood of their existence, based on the fact that there are billions of stars in our own galaxy?

Over the years, a number of scientific papers have tried to partially answer that question, by calculating the actual time period required for civilizations to populate the galaxy (thus estimating whether E.T. simply might not have had time to reach us yet). However, most of those were fairly simplistic in nature: they used a 2D model of the galaxy in which the stars are all fixed relative to each other, and simply calculated the distances that spaceships would need to travel to traverse all of the stars.

However, the ‘Cool Worlds‘ channel on YouTube recently posted a video about galactic colonization that addresses this issue, and it’s well worth a watch. In the video, Jason Wright – Professor of Astronomy and Astrophysics at Penn State – discusses a new paper he has co-authored that attempts to model galactic colonization (“The Fermi Paradox and the Aurora Effect: Exo-civilization Settlement, Expansion, and Steady States”).

But this time, the paper is based on simulations using a 3D set of stars that were actually moving relative to each others, as they do in reality.

Here’s the entire video – I discuss some of the more fascinating topics of discussion below.

The most interesting thing that Wright and his co-authors found was that, rather than having to traverse the galaxy by traveling long distances to stars, the more likely strategy would be to let the stars come to you (as much as possible), and then ‘hitch a ride’.

As Wright notes:

The truth is, moving near the speed of light just seems really really hard even for fairly advanced technologies…. It seems likely that if there are interstellar ships they move pretty slowly, and they take ten thousand or a hundred thousand years to get to their target.

What that means is: once you set up a settlement your ships aren’t much faster than the stars around you; and that settlement will move through the galaxy and constantly encounter fresh stars that haven’t been settled, and that this helps settle the galaxy.

“You don’t need to do it with the ships because the stars are moving,” Wright explains. “The stars are your ships.”

Additionally, stars closer to the centre of the galaxy move faster, and those further out slower. There are also a lot of stars in the galactic halo that don’t move in a disk – they don’t swirl like the rest of the stars: they go in towards the centre, they go out, they go every which way, they counter-rotate in the disk. What this means is that settlements can spread to different areas quicker than you might imagine.

As Wright says, “it’s sort of like you know stirring the jam in the porridge – you’ll just see the settlements eventually cover the whole thing, even if the individual ships aren’t very fast.” That is, the churning of the stars themselves within the galaxy would help civilizations spread far and wide faster than you might think.

“It’s not like they’re crossing the whole galaxy themselves – they’re just getting carried around by the stars,” Wright explains.

So the motions of the stars make settling the galaxy much, much easier, and that – as they say – sharpens the Fermi Paradox. It means it’s much easier to populate the whole galaxy than some of the more naive earlier models.

That’s not to say that the researchers assumed that every star system in the galaxy offered a potential place to settle. For a start, obviously, there are a number of systems that would not offer any planets that were compatible with human life.

But the authors also thought outside the box, suggesting that another reason galactic colonisers might avoid some star systems is because they are already inhabited. Wright and his co-authors called this the ‘Aurora effect’, naming it after the novel by Kim Stanley Robinson.

I really like this idea because it runs contrary to a lot of science fiction narratives that argue that [aliens] would want to come to the Earth exactly because there’s life here, and we have resources that they would want. But that assumes it’s a very natural tendency to see something someone else has and take it from them. And who knows maybe that’s completely contrary to the way that any any spacefaring civilization would behave.

The fraction of stars in the galaxy that are worth settling was just one of the many variables the researchers used to create the colonization modeling. “What that means, if that’s very low then you have to wait a long time before one comes into range that you can settle,” Wright points out, “and that slows down the propagation of the settlement front considerably”. Other variables included how long civilizations might survive, how quickly they might reach the spacefaring stage of development, and how far their ships might be able to travel, among others.

But they didn’t just make their own decision as to what the likely values were for each of the variables. Instead they “tried lots of different assumptions and then we mapped out the results of those assumptions”.

What this showed was that the results varied widely depending on what the original values plugged into the model were.

“What this research did for me,” Wright says, “is it helped highlight the assumptions that underlie people’s beliefs, [whether] they think there’s nothing out there, or that there’s a lot of things out there.”

So now when people talk about the Fermi paradox and say everyone should be out there, we can say ‘okay everyone should be out there, all the stars should have settlements if you believe settlements would last this long’ – and you can tell them exactly what it is that they’re assuming. I think that helps quantify the assumptions behind SETI and help inform what maybe we should believe.

  1. There are quite a few underlying assumptions here, including the ideas that “physical reality” is all there is, that we are each entirely separate physical (made entirely of “matter”) creatures who arose thanks to random combinations of chemicals and mutations, delineated by our skin and limited to the usual five senses, our minds a side effect (“epiphenomene”) of our brains, and so on.

    Questions concerning the nature of time, space, and reality all enter into this, while few astronomers I’m aware of say much of anything about consciousness.

    “Most of my readers are familiar with the term, ‘muscle bound.’ As a species you have grown ‘ego bound’ instead, held in a spiritual rigidity, with the intuitive portions of the self either denied or distorted beyond any recognition.” (Seth, in his introduction to Seth Speaks.)

    This ‘ego bound’ condition includes a general lack of conscious awareness of probable selves and realities, but that is easily remedied simply by doing Seth’s Practice Element 1. in his The “Unknown” Reality Volume One.

    I would expect members of any long existing galactic civilization to be highly evolved in ways that lie well outside our present “official” or “institutional” knowledge or understanding. They would need no physical vessels were they to choose to visit or interact with us and would not be restricted by great distances or lengths of time, as we presently understand space and time, although there might well be hybrid “technologies” that include a type of vessel that could appear to us as physical in nature.

  2. This is a long post, feel free to skip it.

    RealityTest said: They would need no physical vessels were they to choose to visit or interact with us and would not be restricted by great distances or lengths of time,

    That’s why I love the movie K-PAX, where K-PAX is basically using soul travel rather than traveling physically.

    It’s such a fun concept that I use it as a running theme in many of the stories I do.

    I also have people walk from world to world. The old “origin” stories always mention that their people walked from one place to this new place. That’s a classic theme in many of the novels over the past 200 hundred years.

    – The novel Perdido Street Station by China Mieville mentions that all the different people “walked” to that world.

    So I use the process of soul travel(K-PAX) and walking the “Geometric”. Incredibly useful for story purpose.

    BTW, I look at “UFOs” as being atmospheric craft, not a machine that travels through the void of space. That they follow the “Geometric” moving from world to world to get here.

    When you talk about “reality” it makes me think of my quest over the past decades. I’ve posted about my latest search for “reality” on a different blog, so I won’t repeat it here. I’ll put a link[1] down at the bottom for the book, The Case Against Reality, but I digress.

    I like the way you are looking at the problem. I’ll have to dig deeper.



    For story purposes, I like the video and the paper showing me how consensus science thinks. This is great stuff to show how the “villain” would look at the world. I always have trouble coming up with great villains and “villain speak” so this is very helpful.


    That brings me to the video and the guy’s assumptions of what he thinks is most likely and least likely.

    In the video, they mention Occam’s Razor. The thing is:

    – Occam’s Razor makes butchers of us all.

    So whenever people use Occam’s Razor I look to see what they cut away to get to their “simple is best” solution.

    His first assumption at 3:15 in the video is that we “evolved” here, and that there is no evidence of Earth being settled from outside. Oh, really, and how does he know that.

    Then at 21:15 he’s dismissing the central part of the graph as being “very finely tuned”, because he doesn’t like the implications.

    The problem with the paper they mention, and the simulation they created, is that the Galaxy does not spin the way they mention. At 11:35 in the video, they show the inner stars moving faster than the outer stars. That’s not how it works. That’s how Sagan showed it in the classic Cosmos, but no one uses that outdated model anymore.

    – In the 1980s they discovered that galaxies spin like a solid disk.

    If anyone remembers vinyl records spinning on the turntable they can see that a dot near the center and a dot near the edge are moving together. That “moving as a disk” is why they came up with the nonsense of “Dark Matter”.

    The people in the Electric Universe/Plasma Cosmology group talk of the Galaxy as a “homopolar motor” like the disk in your electric meter at home. Electricity holds the galaxy together, not the much weaker force of gravity. The’ve been able to show that fact pretty convincingly, there is no need for “Dark Matter”, but I digress.

    BTW, I’ve found that George Hansen’s, The Trickster and the Paranormal, is dead on. I’ve had trouble posting much of the information I have found along the way. I’ve discovered that the only safe way to talk about this stuff is in Story[2], narrative, so I’m in the process of writing novels rather than non-fiction, but this set of links will get you started.

    Have fun.

    [1] Here is the link to Donald Hoffman, his videos and book:

    The Case Against Reality

    [2] April Fools is my High Holy day — if anyone missed the point — but that doesn’t change the facts of what I’m saying.

  3. It’s frustrating that the models don’t include the very real (very real = viral) possibility that genetic material can plausibly survive on comets and meteors. SARS-2 from space. Genetic upgrade.

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