5 ms·

The Great Filter theory has a very big assumption attached to it, and it's troubling that it's seemingly become accepted as fact by the constant references to "

by gfodor 6y ago

The Great Filter theory has a very big assumption attached to it, and it's troubling that it's seemingly become accepted as fact by the constant references to "The Great Filter" as a real thing. The assumption is that in a universe with other civilizations we'd certainly be aware of them. I can't say what prior we should have on that, but it's definitely not 100%. Certainly if we find bacteria on Venus all of the claims of "The Great Filter was the creation of cells" will be wrong, and in retrospect it will be shocking to think we could be so ignorant as to be unaware of bacteria on our nearest neighbor for so long. In other words, if it took us this long to find bacteria on Venus, why should we assume anything about our ability to determine life beyond our Solar System?

yreg 6y ago
I'm not at all suggesting that the Great Filter is a real thing. I consider the other main solutions of the Fermi Paradox (Alien life being too alien, Simulation Hypothesis, Dark Forest, Zoo and other) just as intriguing! Great Filter is neat because it bundles many different solutions together into one class. Any solution saying that civilizations in the Milky Way are incredibly rare is basically a variation on Great Filter. >why should we assume anything about our ability to determine life beyond our Solar System? It isn't farfetched to assume that sufficiently expansionist/numerous Kardashev type 2+ civilizations should be easier to detect from Earth than bacteria on Venus.
- Jweb_Guru 6y ago
  > Kardashev type 2+ civilizations I think you are in fact laundering the very large assumption you're making.
  - yreg 6y ago
    If they are contained in their home systems for hundreds upon hundreds of millions of years then the Great Filter is interstellar travel, is it not?
    - Jweb_Guru 6y ago
      Well, that depends on how you define "the Great Filter" I suppose. For many it's attempting to explain why intelligent civilizations are rare, rather than why Kardashev type 2+ civilizations are rare. Of course, if you strictly define it as "the thing that makes it look like intelligent civilizations are rare" I guess that would also work... I just rarely get the impression that this is what people are referring to.
      - yreg 6y ago
        I see. Well, we cannot say whether life or intelligent life is rare. There could be millions of worlds with civilizations like ours and it wouldn't be that strange we missed it. However, it does seem that the Milky Way is not collonised (not even the other galaxies as far as we can tell), and if that's truly the case, then it would suggest that there is some kind of filter barring all civilizations from ever doing it. I consider interstellar travel not ever being viable a legitimate filter. Of course there is a plethora of other solutions as well.
a_crc 6y ago
I completely agree that the great filter theory is a bit circular in its logic on that premise: Imagine the evidence the average HN reader would need to accept that an extraterrestrial civilization existed. Now contrast that with the portion of human history when we've had the ability to produce evidence like that. It seems a bit reckless to assume that ANY AND EVERY high-tech alien civilization would produce conclusive evidence on a scale such that any civilization like modern humanity around any given star would be able to detect it. I also wanted to point out that life on Venus would not even necessarily move the great filter. It is possible, though not experimentally proven, that lifeforms could survive a cataclysmic ejection from one planet after an asteroid impact and float to another planet in the same system. In other words, the life on Venus may have come from Earth or vice-versa. https://en.wikipedia.org/wiki/Panspermia#Lithopanspermia https://en.wikipedia.org/wiki/Panspermia#Lithopanspermia
- MiroF 6y ago
  > It seems a bit reckless to assume that ANY AND EVERY high-tech alien civilization would produce conclusive evidence on a scale such that any civilization like modern humanity around any given star would be able to detect it. "ANY AND EVERY" is not remotely a part of any plausible premise of either the Great Filter or the Fermi paradox. Please be charitable in stating assumptions of theories you disagree with.
joshuahedlund 6y ago
The assumption is not just about being able to identify civilizations out there. It also assumes that someone should have come to us by now. (Any theory that thousands of other civilizations out there just wouldn't be interested in exploring / expanding / communicating / etc requires every single civilization out there to be that way.)
- krapp 6y ago
  >(Any theory that thousands of other civilizations out there just wouldn't be interested in exploring / expanding / communicating / etc requires every single civilization out there to be that way.) Space is difficult, interstellar space exponentially more so. It isn't necessary to make any claims about any or all civilizations if the nature of physics alone makes it extremely unlikely for any species, however curious, to ever make it out of their local gravity well, much less sustain the technological infrastructure, knowledge base, energy consumption, unified political will (despite vast cultural and biological evolution) and control over every other variable across millions of years as a species to be able to stumble across our planet even once among the billions upon billions of galaxies' worth of stars in the observable universe. One might say "it only has to happen once." I submit that it could have happened a thousand times and we could still never know.
  - gfodor 6y ago
    In this sense, there's a variant of the Great Filter where the Filter isn't the existence of other civilizations, but over the probability mass they'll cross paths with another and each can mutually grok the other exists. Arguably this is a much more grounded way to view the Filter theory, since it's less assumption-laden. It also surfaces the assumptions of the usual Filter theory more starkly. We only recently even became intelligent enough for the concept of us recognizing another civilization to even make sense.
    - krapp 6y ago
      I think people intuitively perceive the universe as being roughly analogous to Earth's oceans. Obviously we know it isn't objectively true, but subjectively we're just not capable of comprehending the true scale and emptiness of space, of reconciling the Hubble Deep Field image[0] with the fact that less than 5% of the entire universe is physical matter. Even the distance between the Earth and Moon is mind-boggling on human scales, and humans have traveled it. So it seems reasonable that if any interstellar civilization were out there, one would have found us by now, or their presence would be obvious to us. After all, Rome knew of China, even if they never directly interacted, and Spain eventually stumbled across the New World. Von Neumann probes make sense because it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero. We look up at the night sky and we can see so many of them, and they seem so close together, obviously you'd run into one no matter which way you went, sooner or later. Right? It's more comforting to make up rationales as to why we might be alone than deal with the ramifications of being surrounded by life we may never see in a universe in which the entirety of physical reality amounts to a rounding error in a zero. [0]https://en.wikipedia.org/wiki/Hubble_Deep_Field https://en.wikipedia.org/wiki/Hubble_Deep_Field [1]https://www.theatlantic.com/technology/archive/2014/12/the-chance-of-a-collision-in-outer-space-is-practically-zilch/383810/ https://www.theatlantic.com/technology/archive/2014/12/the-c...
bluGill 6y ago
It is safe to say that the universe is teaming with life even though we are not aware of it off of earth. Here is a simple thought experiment: assume that there was a civilization that stagnated on our exact level of technology and interest in other life - when would they have detected us at various distances? As we can see by this announcement they wouldn't have detected the first primal soup that formed life (we don't have any probes), but given enough time they would have sent a probe to our planet and detected single celled life, and they would have seen evidence of life. At 5 light years (the closest start is just less than that) they wouldn't have had a chance before about 1900, and they might needed until 1960 (I give a range because there is room for debate on exactly what would be proof, they might have not been sure) to detect out radio transmissions. We would probably have made contact with them in the 1970s. At up to 100 light years the above applies with more of a timeshift. After 200 we don't have the ability to detect ourselves (the technology of 1820 didn't give any emissions to go on.) I'm not sure if they would know there is a planet with water where we are (There has been great progress in detecting small planets but I don't know what their abilities are). The farther out you go the harder it gets. Eventually they are still seeing the big bang form our galaxy and so have no idea life will eventually happen here (or where we will be as the universe is moving all along in directions that they cannot predict)
- outworlder 6y ago
  If you go just be what's detectable by radio emissions, there seems to be another problem. Back when we started broadcasting radio, we needed very powerful transmitters since the receivers were pretty primitive - you could make receivers with no power source at all (Galena radios). Then we started using them for other purposes. Powerful radars appeared. TV was invented. Later on we added digital signals and most traffic shifted to binary for computer to computer communication. Now we have things like WIFI and 5g. The problem is that the technology has advanced so much that cellular antennas can talk to puny transmitters from miles away, while the transmitters are only outputting milliwatts. We can also electronically 'steer' transmissions so they will 'point' at the other party (beamforming). Long range communication is shifting to satellites and fiber optic cables. Those are pretty directional and not very strong signals, by comparison (and fiber optic of course has none). We have been slowly shutting down TV stations in favor of internet streams. Civilian radars still exist but they are relatively weak. They are also slowly being phased out in favor of technologies like ADS-B, which broadcast a fraction of the power. GPS signals are very weak. Military radars are also more sensitive than before - and increasingly look like background noise. Given the high emphasis on stealth, they are also more directional and lower power than before. And may not even be on all the time. Given this, it is possible that, if you are taking a SETI approach, there's only a very small window before a civilization switches to more efficient and less noisy RF comms. > At up to 100 light year At 100 light years you'll have very faint, possibly undetectable signals, as the strength decreases with distance squared. Unless they are pointing at us.
GuB-42 6y ago
What it considered is not the current state of the human race. The real question is more like "why isn't the entire galaxy colonized by a super advanced civilization?". A galactic civilization is expected to leave traces. The most advanced civilizations are expected to use a huge amount of energy (information is energy too). Even if we don't find spaceships, we could see otherwise unexplained high/low entropy regions. In fact, there is a theory that says that life is the most powerful entropy generator, and that Earth has a distinct IR glow because of it. Currently, it doesn't seem there is anything preventing us from colonizing interstellar space in the far future. Lots of unanswered questions but the laws of physics don't exclude it. The Great Filter theory is that because we don't see any sign of a galactic civilization, there is something in the way. It can be behind us (ex: the appearance of life) or ahead of us (ex: civilizations tend to get wiped off before they can colonize other star systems). And even if the great filter is simply that even the most advanced civilizations can stay undetected (so no real filter), finding evidence that the great filter is less likely to be behind us make it more likely to be ahead of us (or inexistant).

by gfodor 6y ago

yreg 6y ago

I'm not at all suggesting that the Great Filter is a real thing. I consider the other main solutions of the Fermi Paradox (Alien life being too alien, Simulation Hypothesis, Dark Forest, Zoo and other) just as intriguing! Great Filter is neat because it bundles many different solutions together into one class. Any solution saying that civilizations in the Milky Way are incredibly rare is basically a variation on Great Filter. >why should we assume anything about our ability to determine life beyond our Solar System? It isn't farfetched to assume that sufficiently expansionist/numerous Kardashev type 2+ civilizations should be easier to detect from Earth than bacteria on Venus.

Jweb_Guru 6y ago
> Kardashev type 2+ civilizations I think you are in fact laundering the very large assumption you're making.
- yreg 6y ago
  If they are contained in their home systems for hundreds upon hundreds of millions of years then the Great Filter is interstellar travel, is it not?
  - Jweb_Guru 6y ago
    Well, that depends on how you define "the Great Filter" I suppose. For many it's attempting to explain why intelligent civilizations are rare, rather than why Kardashev type 2+ civilizations are rare. Of course, if you strictly define it as "the thing that makes it look like intelligent civilizations are rare" I guess that would also work... I just rarely get the impression that this is what people are referring to.
    - yreg 6y ago
      I see. Well, we cannot say whether life or intelligent life is rare. There could be millions of worlds with civilizations like ours and it wouldn't be that strange we missed it. However, it does seem that the Milky Way is not collonised (not even the other galaxies as far as we can tell), and if that's truly the case, then it would suggest that there is some kind of filter barring all civilizations from ever doing it. I consider interstellar travel not ever being viable a legitimate filter. Of course there is a plethora of other solutions as well.

a_crc 6y ago

I completely agree that the great filter theory is a bit circular in its logic on that premise: Imagine the evidence the average HN reader would need to accept that an extraterrestrial civilization existed. Now contrast that with the portion of human history when we've had the ability to produce evidence like that. It seems a bit reckless to assume that ANY AND EVERY high-tech alien civilization would produce conclusive evidence on a scale such that any civilization like modern humanity around any given star would be able to detect it. I also wanted to point out that life on Venus would not even necessarily move the great filter. It is possible, though not experimentally proven, that lifeforms could survive a cataclysmic ejection from one planet after an asteroid impact and float to another planet in the same system. In other words, the life on Venus may have come from Earth or vice-versa. https://en.wikipedia.org/wiki/Panspermia#Lithopanspermia https://en.wikipedia.org/wiki/Panspermia#Lithopanspermia

MiroF 6y ago
> It seems a bit reckless to assume that ANY AND EVERY high-tech alien civilization would produce conclusive evidence on a scale such that any civilization like modern humanity around any given star would be able to detect it. "ANY AND EVERY" is not remotely a part of any plausible premise of either the Great Filter or the Fermi paradox. Please be charitable in stating assumptions of theories you disagree with.

joshuahedlund 6y ago

The assumption is not just about being able to identify civilizations out there. It also assumes that someone should have come to us by now. (Any theory that thousands of other civilizations out there just wouldn't be interested in exploring / expanding / communicating / etc requires every single civilization out there to be that way.)

krapp 6y ago
>(Any theory that thousands of other civilizations out there just wouldn't be interested in exploring / expanding / communicating / etc requires every single civilization out there to be that way.) Space is difficult, interstellar space exponentially more so. It isn't necessary to make any claims about any or all civilizations if the nature of physics alone makes it extremely unlikely for any species, however curious, to ever make it out of their local gravity well, much less sustain the technological infrastructure, knowledge base, energy consumption, unified political will (despite vast cultural and biological evolution) and control over every other variable across millions of years as a species to be able to stumble across our planet even once among the billions upon billions of galaxies' worth of stars in the observable universe. One might say "it only has to happen once." I submit that it could have happened a thousand times and we could still never know.
- gfodor 6y ago
  In this sense, there's a variant of the Great Filter where the Filter isn't the existence of other civilizations, but over the probability mass they'll cross paths with another and each can mutually grok the other exists. Arguably this is a much more grounded way to view the Filter theory, since it's less assumption-laden. It also surfaces the assumptions of the usual Filter theory more starkly. We only recently even became intelligent enough for the concept of us recognizing another civilization to even make sense.
  - krapp 6y ago
    I think people intuitively perceive the universe as being roughly analogous to Earth's oceans. Obviously we know it isn't objectively true, but subjectively we're just not capable of comprehending the true scale and emptiness of space, of reconciling the Hubble Deep Field image[0] with the fact that less than 5% of the entire universe is physical matter. Even the distance between the Earth and Moon is mind-boggling on human scales, and humans have traveled it. So it seems reasonable that if any interstellar civilization were out there, one would have found us by now, or their presence would be obvious to us. After all, Rome knew of China, even if they never directly interacted, and Spain eventually stumbled across the New World. Von Neumann probes make sense because it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero. We look up at the night sky and we can see so many of them, and they seem so close together, obviously you'd run into one no matter which way you went, sooner or later. Right? It's more comforting to make up rationales as to why we might be alone than deal with the ramifications of being surrounded by life we may never see in a universe in which the entirety of physical reality amounts to a rounding error in a zero. [0]https://en.wikipedia.org/wiki/Hubble_Deep_Field https://en.wikipedia.org/wiki/Hubble_Deep_Field [1]https://www.theatlantic.com/technology/archive/2014/12/the-chance-of-a-collision-in-outer-space-is-practically-zilch/383810/ https://www.theatlantic.com/technology/archive/2014/12/the-c...

bluGill 6y ago

It is safe to say that the universe is teaming with life even though we are not aware of it off of earth. Here is a simple thought experiment: assume that there was a civilization that stagnated on our exact level of technology and interest in other life - when would they have detected us at various distances? As we can see by this announcement they wouldn't have detected the first primal soup that formed life (we don't have any probes), but given enough time they would have sent a probe to our planet and detected single celled life, and they would have seen evidence of life. At 5 light years (the closest start is just less than that) they wouldn't have had a chance before about 1900, and they might needed until 1960 (I give a range because there is room for debate on exactly what would be proof, they might have not been sure) to detect out radio transmissions. We would probably have made contact with them in the 1970s. At up to 100 light years the above applies with more of a timeshift. After 200 we don't have the ability to detect ourselves (the technology of 1820 didn't give any emissions to go on.) I'm not sure if they would know there is a planet with water where we are (There has been great progress in detecting small planets but I don't know what their abilities are). The farther out you go the harder it gets. Eventually they are still seeing the big bang form our galaxy and so have no idea life will eventually happen here (or where we will be as the universe is moving all along in directions that they cannot predict)

outworlder 6y ago
If you go just be what's detectable by radio emissions, there seems to be another problem. Back when we started broadcasting radio, we needed very powerful transmitters since the receivers were pretty primitive - you could make receivers with no power source at all (Galena radios). Then we started using them for other purposes. Powerful radars appeared. TV was invented. Later on we added digital signals and most traffic shifted to binary for computer to computer communication. Now we have things like WIFI and 5g. The problem is that the technology has advanced so much that cellular antennas can talk to puny transmitters from miles away, while the transmitters are only outputting milliwatts. We can also electronically 'steer' transmissions so they will 'point' at the other party (beamforming). Long range communication is shifting to satellites and fiber optic cables. Those are pretty directional and not very strong signals, by comparison (and fiber optic of course has none). We have been slowly shutting down TV stations in favor of internet streams. Civilian radars still exist but they are relatively weak. They are also slowly being phased out in favor of technologies like ADS-B, which broadcast a fraction of the power. GPS signals are very weak. Military radars are also more sensitive than before - and increasingly look like background noise. Given the high emphasis on stealth, they are also more directional and lower power than before. And may not even be on all the time. Given this, it is possible that, if you are taking a SETI approach, there's only a very small window before a civilization switches to more efficient and less noisy RF comms. > At up to 100 light year At 100 light years you'll have very faint, possibly undetectable signals, as the strength decreases with distance squared. Unless they are pointing at us.

GuB-42 6y ago

What it considered is not the current state of the human race. The real question is more like "why isn't the entire galaxy colonized by a super advanced civilization?". A galactic civilization is expected to leave traces. The most advanced civilizations are expected to use a huge amount of energy (information is energy too). Even if we don't find spaceships, we could see otherwise unexplained high/low entropy regions. In fact, there is a theory that says that life is the most powerful entropy generator, and that Earth has a distinct IR glow because of it. Currently, it doesn't seem there is anything preventing us from colonizing interstellar space in the far future. Lots of unanswered questions but the laws of physics don't exclude it. The Great Filter theory is that because we don't see any sign of a galactic civilization, there is something in the way. It can be behind us (ex: the appearance of life) or ahead of us (ex: civilizations tend to get wiped off before they can colonize other star systems). And even if the great filter is simply that even the most advanced civilizations can stay undetected (so no real filter), finding evidence that the great filter is less likely to be behind us make it more likely to be ahead of us (or inexistant).