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Possible answer: First nearly every civilization that mastered, say, radio, did it millions of years ago. Second, nearly every such civilization long ago foun

Possible answer: First nearly every civilization that mastered, say, radio, did it millions of years ago. Second, nearly every such civilization long ago found much better means of communications than we know about. Third, they realize that trying to communicate via radio is silly and use much better means we don't know about. Net, they are out there and communicating, but we don't hear them and they don't hear us or bother with us. To hear us, they would have to be within 100 light years, and that's not far enough to cover many candidate planets.

firefoxman1 15y ago
But if they're so advanced, they probably still have radio receivers somewhere though. They should be able to receive our signals and reply with some sort of super advanced method that appears as radio waves so that we can receive them, but that travel much faster so it doesn't take a thousand years to reach us.
- freshhawk 15y ago
  I like the idea that these advanced civilizations are actually all around us and just don't interact with us at all because we are too stupid/too boring/not ready/etc.
  - firefoxman1 15y ago
    Yeah kind of like how bacteria don't know they're under a microscope.
    - freshhawk 15y ago
      Consider your analogy stolen for future use! They're all down there thinking "why aren't there any alien bacteria sending us some chemical messages already? It's clearly the best way to communicate"
      - deleted 15y ago
        [deleted]
      - rbanffy 15y ago
        H. G. Wells' analogy actually.
        firefoxman1 15y ago
        I love Wells. In what book might I find such analogy?
        rbanffy 15y ago
        War of the worlds. Right on the first page.
  - gizmo 15y ago
    Then we presume that all these advanced civilizations are somehow living peacefully together AND that they all agree not to mess with earth. That's extraordinarily unlikely. Evolution isn't good at producing life forms that peacefully co-exist.
- jbrennan 15y ago
  Maybe their governments cut the funding.
- rbanffy 15y ago
  > they probably still have radio receivers somewhere though Do you still have a working analog TV set? A shortwave radio?
incandenza 15y ago
That is my preferred explanation as well. A caveman would not notice a WiFi signal even if it was blasting right through the cave; he would probably be looking for smoke signals or something. Also, a huge intelligence gap makes communication uninteresting. e.g. we know a little bit about how ants communicate via pheromones, but we're not trying to send "messages" to them; what would it possibly be useful to say?
- rationalbeaver 15y ago
  "Stay the hell out of my kitchen" comes to mind. :)
deleted 15y ago
[deleted]
gizmo 15y ago
> First nearly every civilization that mastered, say, radio, did it millions of years ago So then we'd expect to receive signals from civilizations that are a few million light years away. Yet we don't see those signals. We're too young a civilization to be spotted by other life forms (as you said, they'd have to be within a 100 light years or so). But when we look at space in any direction it looks dead. Just background radiation.
- HilbertSpace 15y ago
  A point in my guess is that an old civilization won't be trying to use radio to communicate with us and will be using something better than radio we don't know about. Next, for communications over 1000 light years with just radio, there can be some issues of signal to noise ratio! Sure, we can see a star 1000 light years away, a galaxy 1 billion light years away, and a quasar 10 billion light years away, but a signal from a planet over 1000 light years away? Besides, 1000 light years may not be far enough to cover many planets transmitting. Our galaxy is, what, 100,000 light years across? So, just for our galaxy, might want to think about distances of 50,000 light years or so. The nearest ordinary galaxy is the one in Andromeda, and that's about 1.5 million light years away. Those are long distances for a radio signal from a planet.
  - jerf 15y ago
    "A point in my guess is that an old civilization won't be trying to use radio to communicate with us and will be using something better than radio we don't know about." While a popular conjecture in this recurring debate, over the decades we've built up an awful lot of evidence that there really is no better mechanism for distance communication than electromagnetic radiation. We're running out of places for such putatively better mechanisms to hide. I dislike this line of argument in the modern time, because it conflates two discussions, "what we scientifically know about the universe", and "could conceivable be true even though we have no evidence for our conjectures". While the second may be superficially more fun, it's ultimately a waste of time for any sort of serious discussion because you can hypothesize anything you want. It's content-free, despite the haze of words you can throw up. The first is much more interesting, and while 50 years ago one could still hypothesize better communication mechanisms, I think the argument when used in a serious discussion is out of date. We can name some non-EM communication mechanisms (neutrino beams, for instance), but they all suck horribly by comparison.
bsaunder 15y ago
I wish this had been a root level comment (so it would be more visible). I think this is by far the most plausible explanation especially if you think about human history and technology differences. Imagine our current spy agencies with bleeding edge technology spying on the Romans. Its only a two thousand year difference, but there's absolutely no way they could detect our signals and/or equipment (unless we made a serious mistake). It seems entirely reasonable that another civilization may be tens of thousands of years ahead of us in technological advancement. If you consider the increasing growth rate of technological advancement, its easy to see your explanation.
doktrin 15y ago
While that's certainly 'possible' it doesn't seem particularly logical. Why would "nearly every" intelligent civilization have evolved millions of years before ours?
- HilbertSpace 15y ago
  Let's see: We've been okay with radio for less than 200 years so far. The earth was formed ballpark 4.5 billion years ago. The big bang was about 13.7 billion years ago. Assume that to get a civilization need a planet and, thus, elements heavier than hydrogen and helium. Those heavier elements are created in big stars that supernova, that is, have their cores collapse under gravity and blow off their outer layers where during the explosion all the heavier elements in the periodic table are created by fusing together lighter elements. So to get a planet, have to have a star form, burn out, and supernova. So, assume that are getting candidate planets 3.7 billion years after the big bang. Then have been forming candidate planets for 10 billion years. Now take the planets that have achieved mastry of radio (i.e., working with photons from 60 Hz up to gamma rays). Take the date when they first made this progress with radio. Take the distribution of those dates over the planets. That distribution is 'concentrated' on the last 10 billion years. Now in that distribution spread out over 10 billion years, what is the probability mass of the last million years? It's TINY. Maybe it's 0.01%. Then 99.99% of the civilizations that mastered radio did it over one million years ago and, thus, are a million years or more ahead of us. Done. Okay?
maaku 15y ago
The issue is not radio waves--it's Dyson spheres (look it up). It does not take very long at all for a space-faring civilization to advance to such a point that it's artifacts would be (spectrographically) visible from our telescopes today. It doesn't have to be Dyson spheres either. A large object moving near the speed of light through the interstellar medium would give off one of a few very specific and very strong spectral lines. Now there hasn't been a concerted effort to look for interstellar travelers, but nevertheless in all our years of searching such oddities haven't shown up.
- HilbertSpace 15y ago
  > "visible from our telescopes today." Our nearest other star is 4 light years away. 1000 light years away may still not cover many planets good for ET to colonize. But for us now to see evidence of a colony on a planet 1000 light years away or more would be TOUGH. Note: The planet hunters mostly don't actually see the planets but just shadows or evidence in star wobbles, etc. But we are putting up some new telescopes with some astounding resolution, etc.

firefoxman1 15y ago

But if they're so advanced, they probably still have radio receivers somewhere though. They should be able to receive our signals and reply with some sort of super advanced method that appears as radio waves so that we can receive them, but that travel much faster so it doesn't take a thousand years to reach us.

freshhawk 15y ago
I like the idea that these advanced civilizations are actually all around us and just don't interact with us at all because we are too stupid/too boring/not ready/etc.
- firefoxman1 15y ago
  Yeah kind of like how bacteria don't know they're under a microscope.
  - freshhawk 15y ago
    Consider your analogy stolen for future use! They're all down there thinking "why aren't there any alien bacteria sending us some chemical messages already? It's clearly the best way to communicate"
    - deleted 15y ago
      [deleted]
    - rbanffy 15y ago
      H. G. Wells' analogy actually.
      - firefoxman1 15y ago
        I love Wells. In what book might I find such analogy?
        rbanffy 15y ago
        War of the worlds. Right on the first page.
- gizmo 15y ago
  Then we presume that all these advanced civilizations are somehow living peacefully together AND that they all agree not to mess with earth. That's extraordinarily unlikely. Evolution isn't good at producing life forms that peacefully co-exist.
jbrennan 15y ago
Maybe their governments cut the funding.
rbanffy 15y ago
> they probably still have radio receivers somewhere though Do you still have a working analog TV set? A shortwave radio?

incandenza 15y ago

That is my preferred explanation as well. A caveman would not notice a WiFi signal even if it was blasting right through the cave; he would probably be looking for smoke signals or something. Also, a huge intelligence gap makes communication uninteresting. e.g. we know a little bit about how ants communicate via pheromones, but we're not trying to send "messages" to them; what would it possibly be useful to say?

rationalbeaver 15y ago
"Stay the hell out of my kitchen" comes to mind. :)

deleted 15y ago

[deleted]

gizmo 15y ago

> First nearly every civilization that mastered, say, radio, did it millions of years ago So then we'd expect to receive signals from civilizations that are a few million light years away. Yet we don't see those signals. We're too young a civilization to be spotted by other life forms (as you said, they'd have to be within a 100 light years or so). But when we look at space in any direction it looks dead. Just background radiation.

HilbertSpace 15y ago
A point in my guess is that an old civilization won't be trying to use radio to communicate with us and will be using something better than radio we don't know about. Next, for communications over 1000 light years with just radio, there can be some issues of signal to noise ratio! Sure, we can see a star 1000 light years away, a galaxy 1 billion light years away, and a quasar 10 billion light years away, but a signal from a planet over 1000 light years away? Besides, 1000 light years may not be far enough to cover many planets transmitting. Our galaxy is, what, 100,000 light years across? So, just for our galaxy, might want to think about distances of 50,000 light years or so. The nearest ordinary galaxy is the one in Andromeda, and that's about 1.5 million light years away. Those are long distances for a radio signal from a planet.
- jerf 15y ago
  "A point in my guess is that an old civilization won't be trying to use radio to communicate with us and will be using something better than radio we don't know about." While a popular conjecture in this recurring debate, over the decades we've built up an awful lot of evidence that there really is no better mechanism for distance communication than electromagnetic radiation. We're running out of places for such putatively better mechanisms to hide. I dislike this line of argument in the modern time, because it conflates two discussions, "what we scientifically know about the universe", and "could conceivable be true even though we have no evidence for our conjectures". While the second may be superficially more fun, it's ultimately a waste of time for any sort of serious discussion because you can hypothesize anything you want. It's content-free, despite the haze of words you can throw up. The first is much more interesting, and while 50 years ago one could still hypothesize better communication mechanisms, I think the argument when used in a serious discussion is out of date. We can name some non-EM communication mechanisms (neutrino beams, for instance), but they all suck horribly by comparison.

bsaunder 15y ago

I wish this had been a root level comment (so it would be more visible). I think this is by far the most plausible explanation especially if you think about human history and technology differences. Imagine our current spy agencies with bleeding edge technology spying on the Romans. Its only a two thousand year difference, but there's absolutely no way they could detect our signals and/or equipment (unless we made a serious mistake). It seems entirely reasonable that another civilization may be tens of thousands of years ahead of us in technological advancement. If you consider the increasing growth rate of technological advancement, its easy to see your explanation.

doktrin 15y ago

While that's certainly 'possible' it doesn't seem particularly logical. Why would "nearly every" intelligent civilization have evolved millions of years before ours?

HilbertSpace 15y ago
Let's see: We've been okay with radio for less than 200 years so far. The earth was formed ballpark 4.5 billion years ago. The big bang was about 13.7 billion years ago. Assume that to get a civilization need a planet and, thus, elements heavier than hydrogen and helium. Those heavier elements are created in big stars that supernova, that is, have their cores collapse under gravity and blow off their outer layers where during the explosion all the heavier elements in the periodic table are created by fusing together lighter elements. So to get a planet, have to have a star form, burn out, and supernova. So, assume that are getting candidate planets 3.7 billion years after the big bang. Then have been forming candidate planets for 10 billion years. Now take the planets that have achieved mastry of radio (i.e., working with photons from 60 Hz up to gamma rays). Take the date when they first made this progress with radio. Take the distribution of those dates over the planets. That distribution is 'concentrated' on the last 10 billion years. Now in that distribution spread out over 10 billion years, what is the probability mass of the last million years? It's TINY. Maybe it's 0.01%. Then 99.99% of the civilizations that mastered radio did it over one million years ago and, thus, are a million years or more ahead of us. Done. Okay?

maaku 15y ago

The issue is not radio waves--it's Dyson spheres (look it up). It does not take very long at all for a space-faring civilization to advance to such a point that it's artifacts would be (spectrographically) visible from our telescopes today. It doesn't have to be Dyson spheres either. A large object moving near the speed of light through the interstellar medium would give off one of a few very specific and very strong spectral lines. Now there hasn't been a concerted effort to look for interstellar travelers, but nevertheless in all our years of searching such oddities haven't shown up.

HilbertSpace 15y ago
> "visible from our telescopes today." Our nearest other star is 4 light years away. 1000 light years away may still not cover many planets good for ET to colonize. But for us now to see evidence of a colony on a planet 1000 light years away or more would be TOUGH. Note: The planet hunters mostly don't actually see the planets but just shadows or evidence in star wobbles, etc. But we are putting up some new telescopes with some astounding resolution, etc.