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To me the most likely back of the napkin answer to the Fermi paradox is that aliens are elsewhere in time. The Milky Way galaxy is about 100,000 light years acr

To me the most likely back of the napkin answer to the Fermi paradox is that aliens are elsewhere in time. The Milky Way galaxy is about 100,000 light years across but about 13.5 billion years old. So it’s like 135,000x deeper in the time direction than the distance direction. We’re in the light cones of all the stars we can see, and as far as we know, we can’t get out of them. If a civilization ended even 100 years earlier than our equivalent “now” in their light cone, we wouldn’t have seen them. And if they became visible even 1 year later than our equivalent “now,” we would not have seen them yet. We’re proceeding through time at 1 sec per sec and basically if we’re going to see an alien civilization at this point, I think the only way would be if one happens to achieve the necessary technology to be detected while we’re looking at it. If there were existing civilizations that were easy to see, we would have seen them already. I think it’s far more likely we will confirm alien life first by indirect means, for example spectroscopically detecting free atmospheric oxygen on an exoplanet, or finding tiny fossils on Mars.

kadoban 5y ago
If true, that ends up meaning that alien civilizations are short-lived, right? That doesn't bode well for us.
- hashkb 5y ago
  We're on a steady path to extinction, no doubt.
  - throw1234651234 5y ago
    Generalization. Would be interesting discussion with details. Pop is growing. What's your concern - global warming, fertility rates, pollution, nuclear arsenal, running out of resources? Doesn't seem like we are doing that badly and that pop can't drop if get below renewable resource level or adjust to new ways of making energy/food, etc. Does seem likely that on an extremely long time scale, we need to get multi-planetary, which is "realistic" if we give a reasonable time frame of, say, 10,000 years. As far as the sun dying, that's beyond even parent point's timeline. This is very things start to get questionable if we never get to even .1 of c (e.g. Project Orion "realistic" estimates). Alpha Centauri is relative close at 4.something ly, but other "potentially habitable/useful" star systems are way out there.
    - sha256kira 5y ago
      Agreed. The great filter and collapse theory in general are fascinating in theory and can motivate some great positive action but they can't undermine the fact that humans beings are doing better than they've ever done in our history by almost every imaginable metric.
      - amanaplanacanal 5y ago
        Plus humans are extremely adaptable. Even before we invented agriculture, people had colonized the whole planet, except for Antarctica. It would be hard to kill us all off.
        not_jd_salinger 5y ago
        > humans are extremely adaptable This is a strange claim I see repeated over and over, but it has very little evidence to justify it. The only piece of evidence people present is: > people had colonized the whole planet, except for Antarctica This is true of a fairly large number of organisms on Earth. On top of this humans have only been around for ~200,000 years, that's not long at all. Humans have not survived a single mass extinction event. So far we've seen humans travel around a planet that has been relatively stable for that period of time. There have been plenty of species that have traveled around with us that didn't even need to rely on extra tools, clothing or the use of energy to survive. Humans share several vulnerabilities with other megafauna that have all gone extinct. A major one is a fairly long gestation, plus small number of offspring per generation. Human young likewise need tremendous amounts of care and energy to raise to mature adulthood. Additionally human have fairly high energy requirements to support their complex brains. We've seen exponential rise in human population only because humans have had access to excessive amount of non-renewable, high-energy density sources of energy. It just happens that humans have lived on a planet that has mostly been within survivable temperature changes, with historic climate changes happening on time scales that lead to easy migration. As you pointed out, the one continent that does not have an environment that supports human life remains empty. Humans can't survive a wet bulb temperature of 35C. Until just recently we never saw that temperature on this planet. As we see more and more places reach that temperature more often, I suspect we'll see how frail human adaptability is.
  - beervirus 5y ago
    On a long enough time line, the survival rate for everyone drops to zero.
    - arthurcolle 5y ago
      I am Jack's existential dread
  - delecti 5y ago
    Sure eventually, but there's no clear indication if that's 10 years away, 10 billion years away, or a mere technicality as our descendants evolve into something that counts as a separate species.
    - not_jd_salinger 5y ago
      We're currently undergoing the largest mass extinction event that will easily rank in the top 6 of life on this planet and could possibly compete with the end-permian. What makes you think we could possibly survive? Because we're the cause? Plenty of species in the past that have caused extinction events also perished. It seems far more questionable to assume we won't risk extinction in the geological near term. The parent is downvoted more out of existential fear rather than an honest assessment of the situation.
      - delecti 5y ago
        I think the parent comment was downvoted because it's not really contributing anything besides pessimism. As for us, I don't doubt the likelihood of a serious mass extinction, including possibly a severe drop in human population, but I can't see it being so severe as to cause an existential threat to us. No other species on this planet has had the ability to change the environment to suit it, or the ease of mobility to move where they can survive. Short of earth being entirely incompatible with complex life on the surface, I don't see humanity disappearing because of climate change.
        hashkb 5y ago
        We need the pessimism. Irrational exuberance clearly doesn't work.
        delecti 5y ago
        I have never seen anything remotely resembling exuberance around climate change. Everything I've seen is either pessimism or denial.
- chadwittman 5y ago
  Read more about the Great Filter, it's probable it's ahead of us.
  - riffraff 5y ago
    is it _probable_? AFA we know we've been insanely lucky up to this point (as earthling life we went past multiple mass extinctions, we got multi-cellular life, multiple brains iterations, a society which still didn't wipe itself out etc) What makes it more likely for the filter to be ahead of us rather than behind us?
    - caeril 5y ago
      Modern civilization is extremely dependent on fossil fuels. We've already passed peak conventional oil production, and we're now surviving on EXTRAORDINARY technical means of enhanced oil recovery. If we can't make the complete transition to renewables in the next thirty years, it's game over for a VERY long time. Future civilizations won't enjoy the benefit of Spindletop. Cheap energy sources won't be available near the surface of the crust for another > 50 million years. We won't go extinct, but it will be the 18th century for a very long time and nobody will leave this rock during that time. The Great Filter is right here, in front of us, in our lifetimes.
      - pdonis 5y ago
        > Cheap energy sources won't be available near the surface of the crust for another > 50 million years. Wrong. We already have one: nuclear energy.
        caeril 5y ago
        That's a good point. It's pretty easy to construct and maintain fission reactors without fossil fuels. I bet enriching uranium was a snap in the 18th century, too. It will be even easier even getting to the enrichment phase in the future, with accessible ores about 30% as rich as they were when the nuclear age began. Looking forward to the fleet of electric concrete trucks carrying electrically-manufactured concrete loaded with batteries that were produced with lithium carbonate dug out of the ground by electric excavation rigs. All of this construction work will also not be disrupted by any social unrest resulting from 3 billion people starving to death because the Haber process no longer has enough cheap feedstock to sustain modern agricultural processes. Thanks for educating me.
- Moodles 5y ago
  Carl Sagan thought this, though he lived during the cold war so it's not surprising he did.
  - hnbad 5y ago
    Considering where climate change is heading, it's surprising anyone doesn't think this.
    - Taylor_OD 5y ago
      I agree in our case but this wouldnt be universal. Life may thrive in very hot planets if their evolutionary track was different.
    - scarmig 5y ago
      Climate change is very real and worth addressing, but it's extremely unlikely to wipe out human civilization. It's just going to be costly and kill millions, not billions.
      - ses1984 5y ago
        Climate change by itself could be extremely unlikely to wipe out human civilization but it could be the catalyst that sets other events in motion like nuclear war.
      - darthrupert 5y ago
        Climate change doesn't have to directly kill us all. It could be the trigger to something else that does.
      - miltondts 5y ago
        Extremely unlikely to wipe out all humans. I agree. Current civilization, I'm not so sure. For the reasoning: https://www.youtube.com/watch?v=IESYMFtLIis https://www.youtube.com/watch?v=IESYMFtLIis
      - hnbad 5y ago
        Can you clarify what you mean by "millions"? The Syrian civil war is estimated to have killed just short of half a million people. The pandemic easily has a global death toll of roughly 4 million people so far. The Chalisa famine of 1783/1784 is estimated to have killed 11 million people. The Spanish flu killed at least 17 million people, though some of the more dramatizing estimates place it closer to 100 million. According to some researchers, climate change is already killing 100,000 a year[1]. So I assume you're not thinking of just seven or eight digits unless you're exceedingly optimistic. Climate change will make parts of the world inhabitable that are currently populated by humans. It will also result in crop failures, which will cause famines. In some cases formerly native crops will no longer be supported by the changing local climate or farmland may become completely unusable. Potable water will become harder to source. Water contamination is a source of many deadly diseases. Even if we assume most of the deaths will be concentrated in places like Africa or the Indian subcontinent, the global economy relies on these places for resources and cheap labor. People in ongoing climate catastrophes also don't tend to stay put and die in an orderly fashion, they become refugees or riot against their governments. Things can get politically messy even in the nations next door as humans tend to be uncomfortable with political chaos and mass deaths. But unlike the Spanish flu, or the potato famine, or COVID, climate change is not a temporary blip that happens and then goes away. If all the carriers of the plague have died, nobody dies from the plague unless they get infected handling the dead. Famines can starve millions to death but once there's another harvest the survivors have food again. Climate change isn't like that. If climate change creates a drought, that's not just a drought, that's now dry season and it will be dry season every year from now. There are currently 7.8 billion humans. There's absolutely no reason to believe climate change can't kill billions, especially once it's managed to kill the first hundreds of millions. Keep in mind that it's not about "addressing" climate change. It's not a moldy bathroom tile that you need to clean up or replace before the mold spreads everywhere. It's a fire our entire way of life is fueling every single day. We know what needs to be done to slow it down to survivable levels (or at least levels that are lethal for less than 1% of us) but we can't just pass legislation or appeal to personal responsibility to do that because it involves changes that would be economical suicide for anyone doing it alone. The world economy is playing a game of chicken with each other and nobody is bluffing. [1]: https://grist.org/climate/how-many-people-has-climate-change-killed-already/ https://grist.org/climate/how-many-people-has-climate-change...
- bob33212 5y ago
  Civilizations are only detectable for a short period of time. Once they understand physics, they no longer need radio waves or Dyson spheres or to travel through what we call spacetime.
  - yreg 5y ago
    Why wouldn't they need megastructures and travel once they understood enough physics?
    - bob33212 5y ago
      Space and time may be emergent, we don't know, all we do know is that our current model of physics is missing something. Quantum Gravity for example and We don't know what happens inside a black hole either.
      - yreg 5y ago
        That’s a non-answer though. Do you mean they are guaranteed to discover another “realm” and move to it? Why? It might not be possible, no matter how much physics one knows. Or do you take the Fermi paradox itself as a proof of the solution?
        bob33212 5y ago
        Yes, it seems that the Fermi paradox implies that other civs progress beyond what we consider signs of intelligent life. The great filter seems less likely as we get close to colonizing other planets, and then other solar systems.
        AnimalMuppet 5y ago
        I question your use of "implies" there. It implies no such thing. What you suggest is one possible answer, nothing more.
        5y ago
- aetherson 5y ago
  Short lived on those timescales, yes. But not necessarily short lived in terms of our perspective. If we imagine that in the last 5 billion years, there have been a good solid 10,000 post-industrial civilizations, and each of those civilizations has lasted 10,000 years (in the post-industrial stage where they're detectable), then that implies that of the last 5,000,000,000 years, 100,000,000 of them have been host to a post-industrial civilization: a given year has on average 0.02 currently present civilizations in it. Now, this hypothesis does probably imply that significantly interstellar civilizations are impossible, since it seems like if you've colonized say 20 stars, what disaster could possibly end your civilization? (I think the most likely scenario is that we're the only civilization ever to have developed in the Milky Way. Everything else seems like it assumes a lot of additional stuff.)
  - miltondts 5y ago
    > if you've colonized say 20 stars, what disaster could possibly end your civilization? Unfortunately, war with another civilization.
    - aetherson 5y ago
      I mean, maybe. Honestly hard for me to imagine war actually going on between two interstellar civilizations. But even if it did, it seems like in 99% of all cases, that would leave at least one of the two civilizations still around. We're looking for explanations, in this hypothesis, that leave 98% of all time with no civilizations.
      - kadoban 5y ago
        Maybe war between two spacefaring civilizations is too "easy". eg something like: throwing asteroids at ~the speed of light is necessarily a cheap thing to do once you're at that level, and everyone just dies. Like if on Earth nukes were something everyone could cook up in their backyard in an afternoon, we'd all be gone pretty quick. Not sure that really makes any sense though.
        5y ago
pharke 5y ago
This is the L constant of the Drake equation. Probably the hardest to find a value for until we've actually discovered other intelligent life or remains of such. The confounding part of it is that we can only guess at things that may end a civilization so completely that it will never recover. Things like the so called Great Filters, natural extinctions like impact events or gamma ray bursts, or other more speculative things that prevent expansion. The tricky part is that our existence seems to fly in the face of such events so far, is that mere luck or do all forms of intelligent life have enough sense to navigate around these problems? The last and most paradox defining part of the problem is that even if the tiniest fraction of civilizations can evade these filters then they should eventually be everywhere in the galaxy. Assuming the Copernican principle that we are not at a special place in the universe or time then there should have already been ample opportunity for such civilizations to develop and hence Fermi's question "Where is everybody?".
- kryogen1c 5y ago
  > Great Filters, natural extinctions like impact events or gamma ray bursts you know what really alarms me? these things are only chances on a very, very short-time scale. they are inevitable, yet no one seems alarmed when meteors come between us and the moon and we dont see it coming until hours beforehand. sun bursts blowing out the electric grid, nuclear war, antiobotic resistance, crop and animal monoculture, climate change, natural resource depletion... taleb is right. we need an agent of chaos to make anti-fragility valuable. otherwise we learn the lesson the hard way. by dying.
  - TrainedMonkey 5y ago
    > you know what really alarms me? these things are only chances on a very, very short-time scale. they are inevitable, yet no one seems alarmed when meteors come between us and the moon and we dont see it coming until hours beforehand. That is why Elon is so hell bent on making humanity multi planetary.
    - tsimionescu 5y ago
      Elon Musk has the same chance of making humanity multi-planetary as the Pharaohs did. We are still far away from any semblance of a chance to do so. Besides, anything at all that we can imagine hitting the earth (except a gamma ray burst or collision with another planet) would still leave the earth in a better shape than Mars is. It's entirely doubtful that humanity could be self-sustaining on Mars even in principle, it is certainly not possible with known technologies.
ryandvm 5y ago
That and the fact that civilizations probably only broadcast EM radiation out into the void for a short period of time before they start getting into energy efficiency and switch over to more efficient communication technologies.
- cogman10 5y ago
  This is my theory. You look at human civilization and that's exactly what's happened. We started off by broadcasting everything as loud as we could (which isn't very loud) and we've slowly transitioned to signals that are both quieter and don't really survive escaping the atmosphere. I can't imagine an advanced species wouldn't follow a similar communications path. The only way we detect them is if they specifically target our spot in the sky with focused EM for a very long time, generations! After all, they have no clue when we would be in our evolutionary path. And for that to happen, the species would have to first find us. Not just find us, find us while we are still listening. And this is all with the assumption that FTL communication/observation is even a possibility (It likely isn't). IMO, the simplest answer is that FTL communication and travel is impossible. Advanced civilizations across the galaxy have all come to the same conclusion. We might be able to explore our own neighboring stars throughout generations but it's unlikely we'll be able to ever send a message to another civilization that will get there while they are listening (without spending huge amounts of power).
  - xwolfi 5y ago
    But if you pursue an evolution over millions of years, at some point we'll have to miniaturise. Imagine we can make fully conscious silicon - let's say in 200 000 years (6500 human generations). At this point, we'd be tempted little by little to raise them as our intellectual children and find less and less need to make them with sperm and vagina. After a long while, there might be this great replacement, totally peaceful, that would lead these conscious organisms with a vastly superior intellectual efficiency to probably become very small and self centered and not behave like the territorial monkeys we are. What do you think a massively singular electronic intelligence will think when it notices a planet like ours ? "nuke them all and rape their women" ? This is monkey behavior that we still haven't fully shaken up.
magneticnorth 5y ago
And to add the evidence we do have; in the billions of years of life on earth, there has only been <200 years where any species had the will and the way to send deliberate communications into space. Observational evidence suggests that the time span of civilizations existing is vanishingly tiny compared to the vastness of time overall
anyonecancode 5y ago
This makes sense to me. I feel we're in a small room peeking through a tiny hole in the wall and asking why the outside world is so empty.
0-_-0 5y ago
It's much easier to traverse 1 year in time then 1 light year in space though
- toufka 5y ago
  Is it? I can move all sorts of distances, in different directions, at all sorts of rates. It's surely harder to go certain speeds than others, and in certain directions than others. But to move 1 year in time - I only have one speed and one direction to move.
ManBlanket 5y ago
There's the other end of a technology curve, when a civilization ceases use of an outdated piece of technology. In our case humanity is looking for radar because we're currently broadcasting it. Why would anyone continue using radar to communicate within a few years of quantum entangled data processing, capable instantly transmitting data instantaneously across vast distances? There might be a few living that rock star lifestyle of HAM radio operation and messenger pidgeons, but at that moment our civ would go narly completely dark to our sister civ's SETI program. All humanity's existence so far has been nothing but spark swallowed up by the darkness of time. Our use of radio a fart in the wind. This theory is incredibly type-zero-civ-pocentric. A species capable of interstellar travel will have mastered technologies we can't even comprehend. By the time humanity is able to meaningfully reach across the stars, we'll have spread life across our entire solar system and everything we'd ever need. Unlimited energy from our sun, a lush and verdant Venus and Mars, mining colonies across the solar system producing vast quantities of any desirable element, not to mention an Earth whose biosphere is a shining jewel - perpetually locked-in at peak biodiversity. Begs the question of what we would ever need from another civ, and furthermore what a similar civilization would ever want from a bunch of squatting troglodytes such as ourselves.
- tyfighter 5y ago
  That's not possible. (https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem)
  - rtsil 5y ago
    This assumes that QM (and/or our current understanding of it) is the ultimate explanation of how the Universe works.
- rtsil 5y ago
  > Begs the question of what we would ever need from another civ, and furthermore what a similar civilization would ever want from a bunch of squatting troglodytes such as ourselves. The need to fight loneliness and to find a kindred spirit?

kadoban 5y ago

If true, that ends up meaning that alien civilizations are short-lived, right? That doesn't bode well for us.

hashkb 5y ago
We're on a steady path to extinction, no doubt.
- throw1234651234 5y ago
  Generalization. Would be interesting discussion with details. Pop is growing. What's your concern - global warming, fertility rates, pollution, nuclear arsenal, running out of resources? Doesn't seem like we are doing that badly and that pop can't drop if get below renewable resource level or adjust to new ways of making energy/food, etc. Does seem likely that on an extremely long time scale, we need to get multi-planetary, which is "realistic" if we give a reasonable time frame of, say, 10,000 years. As far as the sun dying, that's beyond even parent point's timeline. This is very things start to get questionable if we never get to even .1 of c (e.g. Project Orion "realistic" estimates). Alpha Centauri is relative close at 4.something ly, but other "potentially habitable/useful" star systems are way out there.
  - sha256kira 5y ago
    Agreed. The great filter and collapse theory in general are fascinating in theory and can motivate some great positive action but they can't undermine the fact that humans beings are doing better than they've ever done in our history by almost every imaginable metric.
    - amanaplanacanal 5y ago
      Plus humans are extremely adaptable. Even before we invented agriculture, people had colonized the whole planet, except for Antarctica. It would be hard to kill us all off.
      - not_jd_salinger 5y ago
        > humans are extremely adaptable This is a strange claim I see repeated over and over, but it has very little evidence to justify it. The only piece of evidence people present is: > people had colonized the whole planet, except for Antarctica This is true of a fairly large number of organisms on Earth. On top of this humans have only been around for ~200,000 years, that's not long at all. Humans have not survived a single mass extinction event. So far we've seen humans travel around a planet that has been relatively stable for that period of time. There have been plenty of species that have traveled around with us that didn't even need to rely on extra tools, clothing or the use of energy to survive. Humans share several vulnerabilities with other megafauna that have all gone extinct. A major one is a fairly long gestation, plus small number of offspring per generation. Human young likewise need tremendous amounts of care and energy to raise to mature adulthood. Additionally human have fairly high energy requirements to support their complex brains. We've seen exponential rise in human population only because humans have had access to excessive amount of non-renewable, high-energy density sources of energy. It just happens that humans have lived on a planet that has mostly been within survivable temperature changes, with historic climate changes happening on time scales that lead to easy migration. As you pointed out, the one continent that does not have an environment that supports human life remains empty. Humans can't survive a wet bulb temperature of 35C. Until just recently we never saw that temperature on this planet. As we see more and more places reach that temperature more often, I suspect we'll see how frail human adaptability is.
- beervirus 5y ago
  On a long enough time line, the survival rate for everyone drops to zero.
  - arthurcolle 5y ago
    I am Jack's existential dread
- delecti 5y ago
  Sure eventually, but there's no clear indication if that's 10 years away, 10 billion years away, or a mere technicality as our descendants evolve into something that counts as a separate species.
  - not_jd_salinger 5y ago
    We're currently undergoing the largest mass extinction event that will easily rank in the top 6 of life on this planet and could possibly compete with the end-permian. What makes you think we could possibly survive? Because we're the cause? Plenty of species in the past that have caused extinction events also perished. It seems far more questionable to assume we won't risk extinction in the geological near term. The parent is downvoted more out of existential fear rather than an honest assessment of the situation.
    - delecti 5y ago
      I think the parent comment was downvoted because it's not really contributing anything besides pessimism. As for us, I don't doubt the likelihood of a serious mass extinction, including possibly a severe drop in human population, but I can't see it being so severe as to cause an existential threat to us. No other species on this planet has had the ability to change the environment to suit it, or the ease of mobility to move where they can survive. Short of earth being entirely incompatible with complex life on the surface, I don't see humanity disappearing because of climate change.
      - hashkb 5y ago
        We need the pessimism. Irrational exuberance clearly doesn't work.
        delecti 5y ago
        I have never seen anything remotely resembling exuberance around climate change. Everything I've seen is either pessimism or denial.
chadwittman 5y ago
Read more about the Great Filter, it's probable it's ahead of us.
- riffraff 5y ago
  is it _probable_? AFA we know we've been insanely lucky up to this point (as earthling life we went past multiple mass extinctions, we got multi-cellular life, multiple brains iterations, a society which still didn't wipe itself out etc) What makes it more likely for the filter to be ahead of us rather than behind us?
  - caeril 5y ago
    Modern civilization is extremely dependent on fossil fuels. We've already passed peak conventional oil production, and we're now surviving on EXTRAORDINARY technical means of enhanced oil recovery. If we can't make the complete transition to renewables in the next thirty years, it's game over for a VERY long time. Future civilizations won't enjoy the benefit of Spindletop. Cheap energy sources won't be available near the surface of the crust for another > 50 million years. We won't go extinct, but it will be the 18th century for a very long time and nobody will leave this rock during that time. The Great Filter is right here, in front of us, in our lifetimes.
    - pdonis 5y ago
      > Cheap energy sources won't be available near the surface of the crust for another > 50 million years. Wrong. We already have one: nuclear energy.
      - caeril 5y ago
        That's a good point. It's pretty easy to construct and maintain fission reactors without fossil fuels. I bet enriching uranium was a snap in the 18th century, too. It will be even easier even getting to the enrichment phase in the future, with accessible ores about 30% as rich as they were when the nuclear age began. Looking forward to the fleet of electric concrete trucks carrying electrically-manufactured concrete loaded with batteries that were produced with lithium carbonate dug out of the ground by electric excavation rigs. All of this construction work will also not be disrupted by any social unrest resulting from 3 billion people starving to death because the Haber process no longer has enough cheap feedstock to sustain modern agricultural processes. Thanks for educating me.
Moodles 5y ago
Carl Sagan thought this, though he lived during the cold war so it's not surprising he did.
- hnbad 5y ago
  Considering where climate change is heading, it's surprising anyone doesn't think this.
  - Taylor_OD 5y ago
    I agree in our case but this wouldnt be universal. Life may thrive in very hot planets if their evolutionary track was different.
  - scarmig 5y ago
    Climate change is very real and worth addressing, but it's extremely unlikely to wipe out human civilization. It's just going to be costly and kill millions, not billions.
    - ses1984 5y ago
      Climate change by itself could be extremely unlikely to wipe out human civilization but it could be the catalyst that sets other events in motion like nuclear war.
    - darthrupert 5y ago
      Climate change doesn't have to directly kill us all. It could be the trigger to something else that does.
    - miltondts 5y ago
      Extremely unlikely to wipe out all humans. I agree. Current civilization, I'm not so sure. For the reasoning: https://www.youtube.com/watch?v=IESYMFtLIis https://www.youtube.com/watch?v=IESYMFtLIis
    - hnbad 5y ago
      Can you clarify what you mean by "millions"? The Syrian civil war is estimated to have killed just short of half a million people. The pandemic easily has a global death toll of roughly 4 million people so far. The Chalisa famine of 1783/1784 is estimated to have killed 11 million people. The Spanish flu killed at least 17 million people, though some of the more dramatizing estimates place it closer to 100 million. According to some researchers, climate change is already killing 100,000 a year[1]. So I assume you're not thinking of just seven or eight digits unless you're exceedingly optimistic. Climate change will make parts of the world inhabitable that are currently populated by humans. It will also result in crop failures, which will cause famines. In some cases formerly native crops will no longer be supported by the changing local climate or farmland may become completely unusable. Potable water will become harder to source. Water contamination is a source of many deadly diseases. Even if we assume most of the deaths will be concentrated in places like Africa or the Indian subcontinent, the global economy relies on these places for resources and cheap labor. People in ongoing climate catastrophes also don't tend to stay put and die in an orderly fashion, they become refugees or riot against their governments. Things can get politically messy even in the nations next door as humans tend to be uncomfortable with political chaos and mass deaths. But unlike the Spanish flu, or the potato famine, or COVID, climate change is not a temporary blip that happens and then goes away. If all the carriers of the plague have died, nobody dies from the plague unless they get infected handling the dead. Famines can starve millions to death but once there's another harvest the survivors have food again. Climate change isn't like that. If climate change creates a drought, that's not just a drought, that's now dry season and it will be dry season every year from now. There are currently 7.8 billion humans. There's absolutely no reason to believe climate change can't kill billions, especially once it's managed to kill the first hundreds of millions. Keep in mind that it's not about "addressing" climate change. It's not a moldy bathroom tile that you need to clean up or replace before the mold spreads everywhere. It's a fire our entire way of life is fueling every single day. We know what needs to be done to slow it down to survivable levels (or at least levels that are lethal for less than 1% of us) but we can't just pass legislation or appeal to personal responsibility to do that because it involves changes that would be economical suicide for anyone doing it alone. The world economy is playing a game of chicken with each other and nobody is bluffing. [1]: https://grist.org/climate/how-many-people-has-climate-change-killed-already/ https://grist.org/climate/how-many-people-has-climate-change...
bob33212 5y ago
Civilizations are only detectable for a short period of time. Once they understand physics, they no longer need radio waves or Dyson spheres or to travel through what we call spacetime.
- yreg 5y ago
  Why wouldn't they need megastructures and travel once they understood enough physics?
  - bob33212 5y ago
    Space and time may be emergent, we don't know, all we do know is that our current model of physics is missing something. Quantum Gravity for example and We don't know what happens inside a black hole either.
    - yreg 5y ago
      That’s a non-answer though. Do you mean they are guaranteed to discover another “realm” and move to it? Why? It might not be possible, no matter how much physics one knows. Or do you take the Fermi paradox itself as a proof of the solution?
      - bob33212 5y ago
        Yes, it seems that the Fermi paradox implies that other civs progress beyond what we consider signs of intelligent life. The great filter seems less likely as we get close to colonizing other planets, and then other solar systems.
        AnimalMuppet 5y ago
        I question your use of "implies" there. It implies no such thing. What you suggest is one possible answer, nothing more.
        5y ago
aetherson 5y ago
Short lived on those timescales, yes. But not necessarily short lived in terms of our perspective. If we imagine that in the last 5 billion years, there have been a good solid 10,000 post-industrial civilizations, and each of those civilizations has lasted 10,000 years (in the post-industrial stage where they're detectable), then that implies that of the last 5,000,000,000 years, 100,000,000 of them have been host to a post-industrial civilization: a given year has on average 0.02 currently present civilizations in it. Now, this hypothesis does probably imply that significantly interstellar civilizations are impossible, since it seems like if you've colonized say 20 stars, what disaster could possibly end your civilization? (I think the most likely scenario is that we're the only civilization ever to have developed in the Milky Way. Everything else seems like it assumes a lot of additional stuff.)
- miltondts 5y ago
  > if you've colonized say 20 stars, what disaster could possibly end your civilization? Unfortunately, war with another civilization.
  - aetherson 5y ago
    I mean, maybe. Honestly hard for me to imagine war actually going on between two interstellar civilizations. But even if it did, it seems like in 99% of all cases, that would leave at least one of the two civilizations still around. We're looking for explanations, in this hypothesis, that leave 98% of all time with no civilizations.
    - kadoban 5y ago
      Maybe war between two spacefaring civilizations is too "easy". eg something like: throwing asteroids at ~the speed of light is necessarily a cheap thing to do once you're at that level, and everyone just dies. Like if on Earth nukes were something everyone could cook up in their backyard in an afternoon, we'd all be gone pretty quick. Not sure that really makes any sense though.
      - 5y ago

pharke 5y ago

This is the L constant of the Drake equation. Probably the hardest to find a value for until we've actually discovered other intelligent life or remains of such. The confounding part of it is that we can only guess at things that may end a civilization so completely that it will never recover. Things like the so called Great Filters, natural extinctions like impact events or gamma ray bursts, or other more speculative things that prevent expansion. The tricky part is that our existence seems to fly in the face of such events so far, is that mere luck or do all forms of intelligent life have enough sense to navigate around these problems? The last and most paradox defining part of the problem is that even if the tiniest fraction of civilizations can evade these filters then they should eventually be everywhere in the galaxy. Assuming the Copernican principle that we are not at a special place in the universe or time then there should have already been ample opportunity for such civilizations to develop and hence Fermi's question "Where is everybody?".

kryogen1c 5y ago
> Great Filters, natural extinctions like impact events or gamma ray bursts you know what really alarms me? these things are only chances on a very, very short-time scale. they are inevitable, yet no one seems alarmed when meteors come between us and the moon and we dont see it coming until hours beforehand. sun bursts blowing out the electric grid, nuclear war, antiobotic resistance, crop and animal monoculture, climate change, natural resource depletion... taleb is right. we need an agent of chaos to make anti-fragility valuable. otherwise we learn the lesson the hard way. by dying.
- TrainedMonkey 5y ago
  > you know what really alarms me? these things are only chances on a very, very short-time scale. they are inevitable, yet no one seems alarmed when meteors come between us and the moon and we dont see it coming until hours beforehand. That is why Elon is so hell bent on making humanity multi planetary.
  - tsimionescu 5y ago
    Elon Musk has the same chance of making humanity multi-planetary as the Pharaohs did. We are still far away from any semblance of a chance to do so. Besides, anything at all that we can imagine hitting the earth (except a gamma ray burst or collision with another planet) would still leave the earth in a better shape than Mars is. It's entirely doubtful that humanity could be self-sustaining on Mars even in principle, it is certainly not possible with known technologies.

ryandvm 5y ago

That and the fact that civilizations probably only broadcast EM radiation out into the void for a short period of time before they start getting into energy efficiency and switch over to more efficient communication technologies.

cogman10 5y ago
This is my theory. You look at human civilization and that's exactly what's happened. We started off by broadcasting everything as loud as we could (which isn't very loud) and we've slowly transitioned to signals that are both quieter and don't really survive escaping the atmosphere. I can't imagine an advanced species wouldn't follow a similar communications path. The only way we detect them is if they specifically target our spot in the sky with focused EM for a very long time, generations! After all, they have no clue when we would be in our evolutionary path. And for that to happen, the species would have to first find us. Not just find us, find us while we are still listening. And this is all with the assumption that FTL communication/observation is even a possibility (It likely isn't). IMO, the simplest answer is that FTL communication and travel is impossible. Advanced civilizations across the galaxy have all come to the same conclusion. We might be able to explore our own neighboring stars throughout generations but it's unlikely we'll be able to ever send a message to another civilization that will get there while they are listening (without spending huge amounts of power).
- xwolfi 5y ago
  But if you pursue an evolution over millions of years, at some point we'll have to miniaturise. Imagine we can make fully conscious silicon - let's say in 200 000 years (6500 human generations). At this point, we'd be tempted little by little to raise them as our intellectual children and find less and less need to make them with sperm and vagina. After a long while, there might be this great replacement, totally peaceful, that would lead these conscious organisms with a vastly superior intellectual efficiency to probably become very small and self centered and not behave like the territorial monkeys we are. What do you think a massively singular electronic intelligence will think when it notices a planet like ours ? "nuke them all and rape their women" ? This is monkey behavior that we still haven't fully shaken up.

magneticnorth 5y ago

And to add the evidence we do have; in the billions of years of life on earth, there has only been <200 years where any species had the will and the way to send deliberate communications into space. Observational evidence suggests that the time span of civilizations existing is vanishingly tiny compared to the vastness of time overall

anyonecancode 5y ago

This makes sense to me. I feel we're in a small room peeking through a tiny hole in the wall and asking why the outside world is so empty.

0-_-0 5y ago

It's much easier to traverse 1 year in time then 1 light year in space though

toufka 5y ago
Is it? I can move all sorts of distances, in different directions, at all sorts of rates. It's surely harder to go certain speeds than others, and in certain directions than others. But to move 1 year in time - I only have one speed and one direction to move.

ManBlanket 5y ago

There's the other end of a technology curve, when a civilization ceases use of an outdated piece of technology. In our case humanity is looking for radar because we're currently broadcasting it. Why would anyone continue using radar to communicate within a few years of quantum entangled data processing, capable instantly transmitting data instantaneously across vast distances? There might be a few living that rock star lifestyle of HAM radio operation and messenger pidgeons, but at that moment our civ would go narly completely dark to our sister civ's SETI program. All humanity's existence so far has been nothing but spark swallowed up by the darkness of time. Our use of radio a fart in the wind. This theory is incredibly type-zero-civ-pocentric. A species capable of interstellar travel will have mastered technologies we can't even comprehend. By the time humanity is able to meaningfully reach across the stars, we'll have spread life across our entire solar system and everything we'd ever need. Unlimited energy from our sun, a lush and verdant Venus and Mars, mining colonies across the solar system producing vast quantities of any desirable element, not to mention an Earth whose biosphere is a shining jewel - perpetually locked-in at peak biodiversity. Begs the question of what we would ever need from another civ, and furthermore what a similar civilization would ever want from a bunch of squatting troglodytes such as ourselves.

tyfighter 5y ago
That's not possible. (https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem)
- rtsil 5y ago
  This assumes that QM (and/or our current understanding of it) is the ultimate explanation of how the Universe works.
rtsil 5y ago
> Begs the question of what we would ever need from another civ, and furthermore what a similar civilization would ever want from a bunch of squatting troglodytes such as ourselves. The need to fight loneliness and to find a kindred spirit?