9 ms·

The "we are the first" argument seemed less convincing than it could have been. A better argument from that perspective is the observation that Type III civiliz

by maaku 12y ago

The "we are the first" argument seemed less convincing than it could have been. A better argument from that perspective is the observation that Type III civilizations expand at an alarming rate. Whatever the motivation for expansion[1], basic simulations and back of the envelope calculations show that even with technology we could imagine building in the not so distant future, humans could expand into the cosmos at >0.9c. We must assume the same of ET. Now information only reaches us at the speed of light; we are only capable of looking for ET in our own past light cone. That means that any Type I or Type II civilization like us should expect to see an empty sky for most of their existence, until all of a sudden the most distant stars go dim (Dyson sphere, or whatever energy capturing device). And the darkness spreads in a wavefront travelling at almost the speed of light, until it hits and ... the unpredictable happens. We see an empty sky because if the sky wasn't empty, the planet we call Earth and our Sun would already be consumed by some extraterrestrial Type III civilization and Fermi would never have existed. [1] An inflationary universe provides incentive for a hypothetical Type III civilization to spread throughout the cosmos as quickly as possible, as idle time means regions of the universe becoming permanently inaccessible. Or maybe just resource competition and a desire for some elements of a population to remain on the frontier.

aswanson 12y ago
Sounds like a hell of a book/movie plot.
sampo 12y ago
> until all of a sudden the most distant stars go dim Why the most distant?
- jacquesm 12y ago
  Because if the events move at 0.9c the light still moves at 'c', so the furthest stars (of which there are more than nearby ones) will be the first to show you that something is up. The light from the older events will reach us before the events or the light from later events will reach us. Unless of course the whole thing originates in one of the stars nearby but the chances of that are smaller than that it will happen in a system further away.
  - furyofantares 12y ago
    Wouldn't the most likely place for it to start be around halfway between us and the most distant observable stars in whatever direction it starts, then? And then we'd see the sphere of dimming stars increasing in size, while still seeing things behind, in front, or to the sides of the sphere?
    - jacquesm 12y ago
      The part that we can see is so much smaller than what is out there that you'd have to resort to very leaky analogies to try to get the point across. The upper limit to how much larger the universe is compared to the observable (and not the currently observed) universe is somewhere around the 10^20 to 10^25 times larger. Those are hard numbers to grasp but large enough that the chances of an event 'x' taking place outside of the observed universe are larger than inside it.
      - furyofantares 12y ago
        Ah, right, the ones that will disappear are furthest-observed, not furthest-observable... you have to already have been observed to disappear from observance! So, it would be an already-large and rapdily growing sphere intersecting with the sphere of observed stars. edit: Wait, actually, I thought you were saying we CAN (theoretically) observe 10^20+ times as far as we HAVE observed. But re-reading your comment, this sounds wrong: > The upper limit to how much larger the universe is compared to the observable Did you mean to say "the upper limit for how much larger the observable universe is compared to the observed universe"? Or are you actually talking about what might be outside of the observable universe? I figured starting points outside the observable universe were not a consideration for this problem, since they are causally unlinked from us and could not expand into the observable universe faster than it becomes causally unlinked from us as well.
  - sampo 12y ago
    Because of 3d geometry, there are a lot more distant stars/galaxies than there are nearby ones. That much I agree. But the most distant galaxies we see, we see them 13 billion years in the past. So this type III civilization turning off starts at the edge of our observable universe would have developed in just 700 million years after the Big Bang. (If we take 13.7 billion years as the age of the universe.) That I find quite improbable. There is a smaller amount of nearer objects than far away objects, but the far away objects are (or we see them as) younger, and the nearby objects are older. There must be some balance between the respective volumes in near and far, and the available time it probably takes for the type III civilization to have developed?
joe_the_user 12y ago
I feel there's a language used here to conceal some questionable reasoning; "Why don't we see a civilizations spanning a galaxy? How would that work? No idea but why don't we see it?" We could ask why we don't see Lovecraftian gods or giant life forms that each stars. We don't know how that works either.
- maaku 12y ago
  We have plenty of ideas for how that would work. Are you familiar with a Dyson sphere? A Type III civilization is just a Dyson sphere around every star in the galaxy.
  - GuiA 12y ago
    Yes, never mind that Dyson spheres are hypothetical structures that are likely to be as relevant to energy harvesting as Icarus' wings are to flying humans around.
keithnoizu 12y ago
There is actually a pretty good explanation for it in my opinion, that it takes about this long since the big bang for life forms of our complexity to exist. (meaning our planet was seeded at some point with some primitive life forms that than continued on their evolutionary tracks towards this point in time). So you have many planets starting to get to the point where space exploration on a wide scale is feasible. Maybe a few are a hundred thousand and some change years ahead or behind us but the likelihood is low that many are significantly well established, or established long enough and close enough for us to detect.
- DavidSJ 12y ago
  There is actually a pretty good explanation for it in my opinion, that it takes about this long since the big bang for life forms of our complexity to exist. (meaning our planet was seeded at some point with some primitive life forms that than continued on their evolutionary tracks towards this point in time). Interstellar seeding is not required to believe that complex life becomes possible at approximately the same time throughout the universe. Other possible reasons: - Concentration of heavy elements has increased with successive star generations. - Galactic cosmic ray bursts (which can sterilize all complex life within thousands of light years) become less common as a galaxy ages.
  - rjsw 12y ago
    Frequency of big meteorite impacts probably becomes less over time too.
    - marcosdumay 12y ago
      That's an intra solar-system variable, it does not apply to a galaxy.
DavidSJ 12y ago
I had this idea recently myself and to the best of my knowledge you're the only other person who's mentioned it. The closest I've found is the "galactic preemption" hypothesis published in the 80's, but that's more an explanation for why only one civilization would exist in a single galaxy, rather than for why a newborn civilization such as our own would look at the sky and see no signs of civilization in the whole universe. Have you seen this idea published anywhere?
- sgt101 12y ago
  I've read a novel that featured this, I am wracking my brains to remember the title/author. It featured a generation ship that switched to a .com mode as it approached the star to be colonized and a race of bat people who were the putative colonization targets. I am not making this up, but I may have dreamt it!
  - handojin 12y ago
    Nope. Ken MacLeod's 'learning the world'. The alien space bats were a nice touch. Charles Stross' book accelerando has an interesting take on the Fermi paradox too.
    - sgt101 12y ago
      Yup, that was the one. Thanks!
- mickdarling 12y ago
  Two Scifi examples that come to mind are a book, GreenFlies (http://www.amazon.com/Greenflies-Andrew-Darling-ebook/dp/B00MX3QPJM/ http://www.amazon.com/Greenflies-Andrew-Darling-ebook/dp/B00...) that has a fun example of a super-predator type-3-ish civilization, and the motivations that would create the galaxy we see today. David Brin also has a great book, Existence (http://www.amazon.com/Existence-David-Brin-ebook/dp/B0079XPMQS/ http://www.amazon.com/Existence-David-Brin-ebook/dp/B0079XPM... ), that is an example of a super-predator meme that may also be a natural great filter for any intelligent civilizations that pop up. Full disclosure, my brother is the author of the first book.
bdamm 12y ago
This model assumes that interstellar travel is profitable. There is no evidence that this is the case, even if we had Star Trek technology. If it isn't profitable, then it turns into a drain on the home planet. That isn't sustainable.
- dmix 12y ago
  Curious: What would make interstellar travel not possible? Do you mean for humans or machines as well?
  - atom-morgan 12y ago
    Profitable. Not possible.
  - jacquesm 12y ago
    At scale it would not only have to be technologically possible but also economically feasible. If you can't afford it you can't do it even if you have the tech.
  - unoti 12y ago
    An interesting analysis on this topic of the feasibility of human space travel was written by Charlie Stross here: http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.html http://www.antipope.org/charlie/blog-static/2007/06/the_high...
- gusgordon 12y ago
  It is certainly profitable for a type 1 civilization to move to a type 2 civilization as long as energy consumption and population continue to naturally grow as has happened so far here. Same thing for type 2 to 3. Also, I think that decisions about space travel are not purely for economic reasons and probably in almost any advanced species there is a large amount of the population willing to pay something to explore.
- darkmighty 12y ago
  I think it's a good assumption. If there are systems out there marginally different from our own, and the cost to send a "new civilization builder" doesn't completely exhaust Earth, how can it not be profitable?
darkmighty 12y ago
But the Milky Way is only 50,000 light years in radius (~ average distance between stars?). That's not much at all on a evolutionary scale. So your argument explains why we're not currently observing an alien civilization (i.e. they would expand so close to light speed we would likely either be conquered or observing nothing -- so observing nothing is a consistent scenario). But it does not explain why no Type III civilizations (continuing with the assumption that civilizations all quickly go on to become Type III) has risen at all in the past hundreds of millions of years. You can close that gap that via an anthropic principle by saying that if some civilization were colonizing our solar system, life on Earth would be extinguished/not possible.
- coldtea 12y ago
  >But it does not explain why no Type III civilizations (continuing with the assumption that civilizations all quickly go on to become Type III) has risen at all in the past hundreds of millions of years. I find the assumption about Type III at best. It's like expecting Moore's law to go on forever.
  - sounds 12y ago
    Did you omit a word? ("Type III __ at best") I agree that a Type III Civilization is just an assumption of what direction a civilization would advance. The article does mention an alternative (they no longer care about meat space, or something similar). If we do resolve the Fermi Paradox I suspect we'll be able to express the answer simply enough to not need to bring in Type III Civilizations, the anthropic principle, etc. Note that I find nothing wrong with them as useful tools for discussion, just that the answer likely isn't one we can construct by means of logic, it must be discovered -- as in, observational astronomy. Which is what I intend to do: go out with a telescope and look at the stars. :)
    - coldtea 12y ago
      >Did you omit a word? ("Type III __ at best") Yeah, "tenuous"! Thanks.
- 12y ago
danieltillett 12y ago
I actually posted about this very topic a few days ago here. Once you have von Neumann machines spreading they will take over each new star system pretty much as soon as they reach it. Assuming the von Neumann machines are small and are being powered by an energy source (i.e lasers) from their origin star system they will spread through the galaxy at close to the speed of light. This spread method creates an interesting effect in that we would not see the stars go out until the von Neumann machines had almost reached us if the origin star was within our galaxy - basically the von Neumann machines would be traveling only a little behind the light front from the origin star system (this would make a good science fiction story). If the origin star system was far enough a way, then the slightly slower speed that the von Neumann machines would travel at should allow us to see them progressing though a distance galaxy. Such a galaxy would look to us like part of the galaxy had a chunk taken out of it. It would be worth looking through the galaxy classification data set [1, 2] to see if there are any galaxies like that out there that look like this. My feeling is we won't find any as I think intellegent life is near unique within the visible universe, but it is at least a testable hypothesis. 1. http://www.galaxyzoo.org http://www.galaxyzoo.org 2. http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies
- yzzxy 12y ago
  Stephen Baxter's Manifold novels deal with this problem quite extensively. I would recommend them from anyone interested in the implications of the Fermi paradox expressed in science/speculative fiction.
- maaku 12y ago
  Another testable variation of this is the gravitational effect of voids. Voids[1]are regions of the universe devoid of visible matter (stars), as far as we can tell. These are predicted by the inflationary model as regions of low energy distribution in the early universe. But if we find a void that appears to have gravitational effects on its neighbors, what an astronomer might call "a concentration of dark matter", that could be a Type III civilization. I'd look around the edges and see if we can find any half-eaten galaxies... [1] https://en.wikipedia.org/wiki/Void_%28astronomy%29 https://en.wikipedia.org/wiki/Void_%28astronomy%29
JoeAltmaier 12y ago
Speed of light is fast enough, considering how long the universe has been around. Our galaxy is 100 thousand light-years - a blink in geological time. We can see everything that ever happened in our galaxy right now, excepting the last few moments. I'd instead be looking for evidence civilizations are expanding by ways we don't yet suspect. Soliton waves through gas clouds? Wormholes? Multidimensional folds? What would those things look like? Maybe they look like dark matter or something.

by maaku 12y ago

aswanson 12y ago

Sounds like a hell of a book/movie plot.

sampo 12y ago

> until all of a sudden the most distant stars go dim Why the most distant?

jacquesm 12y ago
Because if the events move at 0.9c the light still moves at 'c', so the furthest stars (of which there are more than nearby ones) will be the first to show you that something is up. The light from the older events will reach us before the events or the light from later events will reach us. Unless of course the whole thing originates in one of the stars nearby but the chances of that are smaller than that it will happen in a system further away.
- furyofantares 12y ago
  Wouldn't the most likely place for it to start be around halfway between us and the most distant observable stars in whatever direction it starts, then? And then we'd see the sphere of dimming stars increasing in size, while still seeing things behind, in front, or to the sides of the sphere?
  - jacquesm 12y ago
    The part that we can see is so much smaller than what is out there that you'd have to resort to very leaky analogies to try to get the point across. The upper limit to how much larger the universe is compared to the observable (and not the currently observed) universe is somewhere around the 10^20 to 10^25 times larger. Those are hard numbers to grasp but large enough that the chances of an event 'x' taking place outside of the observed universe are larger than inside it.
    - furyofantares 12y ago
      Ah, right, the ones that will disappear are furthest-observed, not furthest-observable... you have to already have been observed to disappear from observance! So, it would be an already-large and rapdily growing sphere intersecting with the sphere of observed stars. edit: Wait, actually, I thought you were saying we CAN (theoretically) observe 10^20+ times as far as we HAVE observed. But re-reading your comment, this sounds wrong: > The upper limit to how much larger the universe is compared to the observable Did you mean to say "the upper limit for how much larger the observable universe is compared to the observed universe"? Or are you actually talking about what might be outside of the observable universe? I figured starting points outside the observable universe were not a consideration for this problem, since they are causally unlinked from us and could not expand into the observable universe faster than it becomes causally unlinked from us as well.
- sampo 12y ago
  Because of 3d geometry, there are a lot more distant stars/galaxies than there are nearby ones. That much I agree. But the most distant galaxies we see, we see them 13 billion years in the past. So this type III civilization turning off starts at the edge of our observable universe would have developed in just 700 million years after the Big Bang. (If we take 13.7 billion years as the age of the universe.) That I find quite improbable. There is a smaller amount of nearer objects than far away objects, but the far away objects are (or we see them as) younger, and the nearby objects are older. There must be some balance between the respective volumes in near and far, and the available time it probably takes for the type III civilization to have developed?

joe_the_user 12y ago

I feel there's a language used here to conceal some questionable reasoning; "Why don't we see a civilizations spanning a galaxy? How would that work? No idea but why don't we see it?" We could ask why we don't see Lovecraftian gods or giant life forms that each stars. We don't know how that works either.

maaku 12y ago
We have plenty of ideas for how that would work. Are you familiar with a Dyson sphere? A Type III civilization is just a Dyson sphere around every star in the galaxy.
- GuiA 12y ago
  Yes, never mind that Dyson spheres are hypothetical structures that are likely to be as relevant to energy harvesting as Icarus' wings are to flying humans around.

keithnoizu 12y ago

There is actually a pretty good explanation for it in my opinion, that it takes about this long since the big bang for life forms of our complexity to exist. (meaning our planet was seeded at some point with some primitive life forms that than continued on their evolutionary tracks towards this point in time). So you have many planets starting to get to the point where space exploration on a wide scale is feasible. Maybe a few are a hundred thousand and some change years ahead or behind us but the likelihood is low that many are significantly well established, or established long enough and close enough for us to detect.

DavidSJ 12y ago
There is actually a pretty good explanation for it in my opinion, that it takes about this long since the big bang for life forms of our complexity to exist. (meaning our planet was seeded at some point with some primitive life forms that than continued on their evolutionary tracks towards this point in time). Interstellar seeding is not required to believe that complex life becomes possible at approximately the same time throughout the universe. Other possible reasons: - Concentration of heavy elements has increased with successive star generations. - Galactic cosmic ray bursts (which can sterilize all complex life within thousands of light years) become less common as a galaxy ages.
- rjsw 12y ago
  Frequency of big meteorite impacts probably becomes less over time too.
  - marcosdumay 12y ago
    That's an intra solar-system variable, it does not apply to a galaxy.

DavidSJ 12y ago

I had this idea recently myself and to the best of my knowledge you're the only other person who's mentioned it. The closest I've found is the "galactic preemption" hypothesis published in the 80's, but that's more an explanation for why only one civilization would exist in a single galaxy, rather than for why a newborn civilization such as our own would look at the sky and see no signs of civilization in the whole universe. Have you seen this idea published anywhere?

sgt101 12y ago
I've read a novel that featured this, I am wracking my brains to remember the title/author. It featured a generation ship that switched to a .com mode as it approached the star to be colonized and a race of bat people who were the putative colonization targets. I am not making this up, but I may have dreamt it!
- handojin 12y ago
  Nope. Ken MacLeod's 'learning the world'. The alien space bats were a nice touch. Charles Stross' book accelerando has an interesting take on the Fermi paradox too.
  - sgt101 12y ago
    Yup, that was the one. Thanks!
mickdarling 12y ago
Two Scifi examples that come to mind are a book, GreenFlies (http://www.amazon.com/Greenflies-Andrew-Darling-ebook/dp/B00MX3QPJM/ http://www.amazon.com/Greenflies-Andrew-Darling-ebook/dp/B00...) that has a fun example of a super-predator type-3-ish civilization, and the motivations that would create the galaxy we see today. David Brin also has a great book, Existence (http://www.amazon.com/Existence-David-Brin-ebook/dp/B0079XPMQS/ http://www.amazon.com/Existence-David-Brin-ebook/dp/B0079XPM... ), that is an example of a super-predator meme that may also be a natural great filter for any intelligent civilizations that pop up. Full disclosure, my brother is the author of the first book.

bdamm 12y ago

This model assumes that interstellar travel is profitable. There is no evidence that this is the case, even if we had Star Trek technology. If it isn't profitable, then it turns into a drain on the home planet. That isn't sustainable.

dmix 12y ago
Curious: What would make interstellar travel not possible? Do you mean for humans or machines as well?
- atom-morgan 12y ago
  Profitable. Not possible.
- jacquesm 12y ago
  At scale it would not only have to be technologically possible but also economically feasible. If you can't afford it you can't do it even if you have the tech.
- unoti 12y ago
  An interesting analysis on this topic of the feasibility of human space travel was written by Charlie Stross here: http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.html http://www.antipope.org/charlie/blog-static/2007/06/the_high...
gusgordon 12y ago
It is certainly profitable for a type 1 civilization to move to a type 2 civilization as long as energy consumption and population continue to naturally grow as has happened so far here. Same thing for type 2 to 3. Also, I think that decisions about space travel are not purely for economic reasons and probably in almost any advanced species there is a large amount of the population willing to pay something to explore.
darkmighty 12y ago
I think it's a good assumption. If there are systems out there marginally different from our own, and the cost to send a "new civilization builder" doesn't completely exhaust Earth, how can it not be profitable?

darkmighty 12y ago

But the Milky Way is only 50,000 light years in radius (~ average distance between stars?). That's not much at all on a evolutionary scale. So your argument explains why we're not currently observing an alien civilization (i.e. they would expand so close to light speed we would likely either be conquered or observing nothing -- so observing nothing is a consistent scenario). But it does not explain why no Type III civilizations (continuing with the assumption that civilizations all quickly go on to become Type III) has risen at all in the past hundreds of millions of years. You can close that gap that via an anthropic principle by saying that if some civilization were colonizing our solar system, life on Earth would be extinguished/not possible.

coldtea 12y ago
>But it does not explain why no Type III civilizations (continuing with the assumption that civilizations all quickly go on to become Type III) has risen at all in the past hundreds of millions of years. I find the assumption about Type III at best. It's like expecting Moore's law to go on forever.
- sounds 12y ago
  Did you omit a word? ("Type III __ at best") I agree that a Type III Civilization is just an assumption of what direction a civilization would advance. The article does mention an alternative (they no longer care about meat space, or something similar). If we do resolve the Fermi Paradox I suspect we'll be able to express the answer simply enough to not need to bring in Type III Civilizations, the anthropic principle, etc. Note that I find nothing wrong with them as useful tools for discussion, just that the answer likely isn't one we can construct by means of logic, it must be discovered -- as in, observational astronomy. Which is what I intend to do: go out with a telescope and look at the stars. :)
  - coldtea 12y ago
    >Did you omit a word? ("Type III __ at best") Yeah, "tenuous"! Thanks.
12y ago

danieltillett 12y ago

I actually posted about this very topic a few days ago here. Once you have von Neumann machines spreading they will take over each new star system pretty much as soon as they reach it. Assuming the von Neumann machines are small and are being powered by an energy source (i.e lasers) from their origin star system they will spread through the galaxy at close to the speed of light. This spread method creates an interesting effect in that we would not see the stars go out until the von Neumann machines had almost reached us if the origin star was within our galaxy - basically the von Neumann machines would be traveling only a little behind the light front from the origin star system (this would make a good science fiction story). If the origin star system was far enough a way, then the slightly slower speed that the von Neumann machines would travel at should allow us to see them progressing though a distance galaxy. Such a galaxy would look to us like part of the galaxy had a chunk taken out of it. It would be worth looking through the galaxy classification data set [1, 2] to see if there are any galaxies like that out there that look like this. My feeling is we won't find any as I think intellegent life is near unique within the visible universe, but it is at least a testable hypothesis. 1. http://www.galaxyzoo.org http://www.galaxyzoo.org 2. http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies

yzzxy 12y ago
Stephen Baxter's Manifold novels deal with this problem quite extensively. I would recommend them from anyone interested in the implications of the Fermi paradox expressed in science/speculative fiction.
maaku 12y ago
Another testable variation of this is the gravitational effect of voids. Voids[1]are regions of the universe devoid of visible matter (stars), as far as we can tell. These are predicted by the inflationary model as regions of low energy distribution in the early universe. But if we find a void that appears to have gravitational effects on its neighbors, what an astronomer might call "a concentration of dark matter", that could be a Type III civilization. I'd look around the edges and see if we can find any half-eaten galaxies... [1] https://en.wikipedia.org/wiki/Void_%28astronomy%29 https://en.wikipedia.org/wiki/Void_%28astronomy%29

JoeAltmaier 12y ago

Speed of light is fast enough, considering how long the universe has been around. Our galaxy is 100 thousand light-years - a blink in geological time. We can see everything that ever happened in our galaxy right now, excepting the last few moments. I'd instead be looking for evidence civilizations are expanding by ways we don't yet suspect. Soliton waves through gas clouds? Wormholes? Multidimensional folds? What would those things look like? Maybe they look like dark matter or something.