[sailingparrot]

> It's entirely possible that there have been other technological civilizations over the past 13.7 or so billion years. That's a long time. As such, any civilization that stopped broadcasting in our direction, if they ever did so in the first place, any more than 100,000 or so years ago, would be completely undetectable to us -- ever.

But this is assuming radio signals are the only way we could detect a civilization, what about probes (von neuman or regular), dyson spheres etc. ?

> I guess the most accurate thing we can say would be that we haven't detected another technological civilization within 60 light years or so in the few places we've looked

The signals we received in the last 60 years come from the entire observable universe (it's how we define the observable universe), not just from a 60 ly radius. But the furthest the signal comes from the hardest it is to detect (or the strongest it would have to be to be detectable).

> It's interesting to speculate, but without enough data, speculation is all it is.

I certainly hope that everyone is aware that is pure speculation ;)

[nobody9999]

>The signals we received in the last 60 years come from the entire observable universe (it's how we define the observable universe), not just from a 60 ly radius. But the furthest the signal comes from the hardest it is to detect (or the strongest it would have to be to be detectable).

A fair point. I should have been more specific and limited my statement: "we haven't detected another technological civilization, currently broadcasting electromagnetic signals in our direction, within 60 light years or so in the few places we've looked."

However, that doesn't mean such civilizations don't exist, nor does the fact that we haven't detected any such signals at any distance, or any other indications of such civilizations, extant or not.

[sailingparrot]

> I should have been more specific and limited my statement: "we haven't detected another technological civilization, currently broadcasting electromagnetic signals in our direction, within 60 light years or so in the few places we've looked."

Why restrict yourself to those 60 light years? We haven't heard about any other civilizations in the entire observable even if their transmission happened a long time ago and they may be extinct by now.

It's only true in the other direction: only a civilization less that 60 ly away could possibly have detected our radio signals so far.

[fiblye]

> But this is assuming radio signals are the only way we could detect a civilization, what about probes (von neuman or regular), dyson spheres etc. ?

That’s trying to find a needle in a universe sized haystack, and we’ve only just started digging. Concluding that there’s probably not a needle when we’ve only just started digging our hands in is premature.

[sailingparrot]

> That’s trying to find a needle in a universe sized haystack

But that is the whole point of the fermi paradox. Given the staggering numbers of planets in our galaxy/universe, and given the staggering age of the universe (when compared to our history), it should not be like trying to find a needle in a haystack.

If it is, then that means life is extremly rare, which already answers part of the question.

[fiblye]

That comes with the big assumption that in basically any given corner of the universe, civilizations in galaxies billions of light years away are pumping out radio signals strong enough to be detected from earth.

How likely is it that by the time humanity would be a space faring society that we’d be pumping turbo charged radio signals that are easily distinguished from noise when doing a quick sweep? How likely is it that societies are using radio signals or something similar for a long period of time, and not simply using some better method that humans have yet to discover?

[sailingparrot]

No, the assumption is because our solar system and earth are not particularly old, if life is commonplace, then there are civilizations that should be billions of years older than us. Imagine where we would be (assuming we don't simply destroy ourselves in the next 50 years) with a billion more year of technological progress? We should be all over the galaxy, colonizing left and right, sending probes everywhere, creating dyson sphere like structures that would be easily detectable from afar etc. And that is just one civilization on an single planet out of 100 billions planets in our galaxy.

Of course everything is just speculation, for every hypothesis on one side of the argument you can find 2 hypothesis from the other side that counter it. But the point is, to go back to the original question, that the right answer is definitely not obvious and if someone's opinion is that we are alone, or at least that life is very rare, it's not completly crazy.

[halfdan]

Even if it's as rare as one in a billion we'd still have to map billions of suns, their planets and actually look for it. Other than SETI I don't know any really serious, concerted efforts to looks for other signals of life.

Even the discovery here was somewhat random and required someone to start digging through recorded data.