LJK said:

Up to this point we have been primarily guessing and making mainly sporadic efforts to look for alien life beyond Earth. Forty years in a galaxy that is 10 billion years old is virtually nothing. Even places like the SETI Institute won't be searching for signals full time untiil later in this decade.

Adam:

[Maybe so. A recent discussion points out that SETI has looked at a tiny, tiny bandwidth compared to far more useful frequencies. Also Frank Drake has rightly pointed out that within 50-100 years Earth won't have any interstellar spanning radio leakage. ETIs have to deliberately target us if they're out there and can be heard]

Carl Sagan, who once gave an optimistic estimate from the Drake Equation of 1,000,000 technical civilizations in the galaxy (Drake was far more pessimistic, only 10,000 ETI in th Milky Way), said this averaged out to about one ETI every 200 light years. So assuming our nearest alien neighbors are about that far from Earth, they have a century to go before detecting even our earliest radio signals, and then of course only if they happened to be looking in the first place.

LJK said:

Plus it is the height of hubris to think that ETI, especially really advanced ones, are just so eager to communicate with the talking monkeys with car keys on Sol 3.

Adam said:

[I think that might be true, but it is also a bit of an old line that ETIs will have hang-ups about evolutionary origins - what's wrong with coming from monkeys? Or starfish? Sponges? Vurkuls?]

I wasn't assuming a bias against species, but a bias against levels of advancement. What would a Kardashev Type II or III civilization have to say to us? I know, what do I know what such an ETI would do? Maybe they like talking to their pets. I talk to my dog and cats and at best they probably only understand a few words of English.

LJK said:

The Milky Way galaxy alone is vast, with 400 billion stars spread across 100,000 light years.

Adam said:

[The actual estimate is just ~ 100 billion stars, but it has been exaggerated so ~ 400 billion is something of a truism]

I just finished counting them last week, so I know my number is right.
:^)

LJK said:

Half the estimated Earth-like planets in our star island are several billion years older than our planet (this comes from Geoff Marcy).

Adam said:

[Charles Lineweaver is his source - his metallicity model neglects things like supernova and higher GRB frequency in the past, so while most terrestrials are older they were also too soon for ETIs to survive. Earth probably got whacked a few times prior to our current quiet patch of cosmic time.]

At least this shows that one example of life can survive cosmic nastiness, so maybe others can too, what with the odds being so high.

LJK said:

So what makes us so special, other than we have spent our whole history isolated on one planet,

Adam said:

[didn't everyone, prior to Galactic Empire? So where are They?]

Probably true for all biological evolving creatures. I was making the comment more to say Wake Up to the Wider Reality, Humanity, before you destroy yourselves and waste all that potential!

LJK said:

we're just waking up on a wider cosmic scale, and we still think the whole place was made just for us.

Adam said:

[which is true if we are alone - rather it will be ours, if we're alone...]

I do have a bit of trouble of six billion talking monkeys "owning" the Universe, or even one galaxy, no matter if we have neighbors or not.
It's just way too big. And if there are more universes, forget it.

Adam said:

--- I'm not writing off SETI just yet. But I don't think there will be many ETIs, or if there are we will all be roughly at the same point of development, plus or minus a few billennia. But of course a million years is all it takes to conquer the Galaxy at sub-light, so where are They? Greg Matloff has proposed that They are living quiet lives in mobile habitats 'hidden' in the Kuiper Belt... perhaps he's right? Alternatively they have quietly permeated the Galaxy but missed our little corner. But why no Dyson spheres?

There may be some basic similarities with all carbon-based life forms, but I think we tend to think too much that ETI will develop and think and act just like us. They are *alien* after all. A species of intelligent dolphin on a water world might be really smart, but they probably won't bother building starships and conquering the galaxy. I still think the galaxy is so big that we could have been missed over the billenia, or maybe they did visit way long ago and all the evidence for them is long gone.

But if we do not look and listen, we probably will not find them. And since we don't have any starships heading out into the Cosmos just yet, the present searches are a good start. I think if we are not contacted directly, we may find them by sheer chance, if we are alert.

And while the vast distances and numbers are why I think we have not found any alien life yet, it is these same numbers that also make me think there is plenty of life out there - it's just not all trying to get our attention at the moment. I'm sure they've got their own issues and plans to deal with.