I don’t believe we have enough information to make an answer to the thread’s question any better than a guess. Maybe a bit better than a wild guess, but still a guess.
There are between 150-250 billion stars in the galaxy. Even assuming they all only have 1 planet on average (which we aren’t finding), that would be more planets than you are giving. So far, just based on the few thousand we’ve seen out of hundreds of millions I don’t think it’s unreasonable to posit 40 billion possible planets in the life zone of their star…or in places otherwise conducive to life (such as some of the ice moons in our own solar system that may harbor life). Even if it’s just a billion planets, though, 1 in a billion is pretty long odds so something is off there.
Another thing to consider is…the Milky Way is actually only a medium sized galaxy. Even when we merge with Andromeda we will still not be really big by universe standards.
The OP is clearly asking for opinions.
As noted, the OP is asking for opinions (in the IMHO forum ;)). Sure, it’s a guess…but I think we can make a pretty good informed guess at this point. What will really clench it is if we can ever do some serious exploration in our own solar system to see if life ever existed on, say, Mars (which will pretty much clench the question once and for all if there was) and if other life exists on some of the promising ice moons (which will up the number of possible life bearing bodies in just this galaxy up a lot). At this stage, however, I’d say it’s a good bet that the universe IS teaming with life. Whether that translates to teaming with intelligent life forms is another matter, of course.
I have very little doubt there is intelligent life somewhere else in the universe, once the numbers get bigger than some rich guy’s bank account and into practically incomprehensible astronomical numbers it’s hard to believe there ISN’T intelligent life out there. I just don’t think it’s in this galaxy.
There is a difference between life and intelligent life. If we are just talking about possible places for life (which is what I thought you guys were talking about, and what the OP was asking) then I think there are going to be potentially a lot, assuming there is life on some of our own ice moons or maybe still on Mars. Even in just our own solar system there are a lot of possibilities for life, after all. Scale that up and it’s pretty staggering how much could be out there, even within just a 100 light years of our planet.
Intelligent life is probably going to be a lot more rare. Then you have intelligent life that is also technological. Then you have intelligent life that has advanced technology that could actually be detected or detectable by us. I’d say odds are that there ARE intelligent life forms in our galaxy, just not at a technological level we’d see (after all, 200 years ago we weren’t there either) or detect. There SHOULD be a few more in our own galaxy that are advanced technological so as to be detectable, but then we get into the final great filters, so maybe they all got filtered out. Or we are one of the first (the galaxy isn’t actually that old, and red dwarf stars can last hundreds of billions of years, if not trillions of them).
I agree, our intelligence may have simply been an adaptation due to our unique physical limitations.
It is highly likely that intelligence is just an anomalous trait to select for and obviously is way up in the chain of possible outcomes from a system that simply develops self replicating RNA or DNA.
IMHO there is no evidence that intelligence should be an expected outcome of life.
Yeah, that gets into total speculative territory. There are other intelligent life forms on our own planet (there have been several hominid species, then there are wolves, bears, other great apes and monkeys, dolphins, etc), which speaks to some levels of intelligence being a survival trait, but to what degree? Then you get into all of the unlikely or luck things that put us here and didn’t wipe us out repeatedly, including ourselves (we STILL haven’t really gotten past these yet either, so it could still happen before we start populating even our own solar system).
Intelligence has evolved multiple times on Earth, in multiple ways. Octopuses are highly intelligent. So are some birds, and of course primates and cetaceans.
And single celled life appeared on Earth almost immediately after it was capable of hosting it. That is evidence against it being extremely rare. Not conclusive evidence - it could have been a fluke. But it didn’t take billions of years for life to develop, which you would expect if it only develops once every few billion stars or something.
The jump from single celled to complex life forms DID take billions of years, so it’s possible that the ‘great filter’ is the jump from simple to complex life. But once complex life appeared, it exploded in variety and intelligence began to evolve almost immediately.
There are some interesting new theories coming out of complexity research that would suggest that the overall trend in the unverse has been towards increased complexity and organization, as that’s the fastest way to the heat death. For an example in the physical world, consider wake turbulence or wingtip vortices. Vortices are complex phenomena, and they shed energy more rapidly than smooth laminar flow. Life may be a form of organization that arises wherever possible simply because of information and entropy driving increases in complexity wherever it can.
It would seem to me that if you were an intelligent technologically adept species and you were really serious about finding other intelligent life and/or making your presence known, then self replicating probes would be the way to go. We’re not too far from that and doing that would probably manage a hit within our galaxy within 100k years or so. We haven’t run into that yet (or have we?) So I’m inclined to believe nobody out there in our galaxy is capable of that or bothered to.
It may be interesting to speculate on possible life chemistries different from the DNA-RNA-Protein-Water chemistry found on Earth. There is an interesting free-to-download 18-page paper titled “Is there a common chemical model for life in the Universe?” (I probably linked to it in a year-ago thread.) The paper goes into detail, explaining why the phosphates in nucleic acids are useful, why metabolic reactions are multi-step, and so on. Here are some excerpts:
The possibility of alternate chemistries may not affect our Drake’s guesstimate much. There’s so much uncertainty in the “Drake equation” that even if we multiply by 1000 to accommodate 1000 equally likely alternatives to DNA-RNA-Protein, that extra factor will have only minor effect!
Really? How soon can I buy a pocket-sized microchip manufacturing facility instead of needing a multi-billion-dollar lab that suckers like Intel and AMD have to use? I guess nobody told them that we are close to being able to build sophisticated robots that can build more sophisticated robots from cold rocks in a vacuum. Or–you know–told anybody else, either.
Yeah, and those dumb shits who think someday man will fly, let along go to the moon of all places are just whack, amiright?? 
Seriously, ‘not too far from’ could mean 500 or even a 1000 years, which would be an eye blink of time. Assuming we survive reasonably intact for another 1000 years at something close to the current level of technological development, self replicating robots aren’t going to be that far fetched (and they will probably roll their eyes at the mention of microchips :p). We are already fairly close to having pretty sophisticated robots and pushing things on AI, there are plans to start prospecting for materials and resources in NEOs and the like with development of automated craft to exploit it (and current craft to test and return samples as a sort of proof of concept).
Personally, I think it’s timing as to why we haven’t heard from other civilizations. You have to hit a pretty small window in order for us to be seeing a signal on Earth today. If a highly technological civilization came about a million years ago and only lasted 100k years before either their own singularity or destruction we wouldn’t see anything from them at all today if they were in our galaxy. If a civilization that’s 20k light years away from us today just emerged technologically and started broadcasting we won’t see that for 20k years. Odds seem to be stacked that even if civilizations emerge with advanced technology (and assuming they would use the same tech we do, which seems reasonable, physic being physics) relatively often it would be pretty lucky if we just happened to be looking at the exact time and place for their signals or emanations to reach us. If it happened even 200 years ago we would never have known. And if a really big rock hits us in before we spread out then it would only be a 100 year window for someone to be watching for us as well.
Or who knows? It’s called the Fermi Paradox for a reason, after all…we just don’t know. Maybe we are in a simulation zoo thingy and in that simulation the aliens don’t want us to see anyone else and to always think we are alone. The dirty bastards!
It would take an enormous amount of hubris to imagine that there’s only one sentient race of beings in the universe, and I happen to be in it. I mean, I never even won $2 on a gas station scratch-off.
OTOH, considering the bigness of time and space, it seems exceeding unlikely that any of them would happen to build a spaceship and happen to point it in the direction in a span of time that happens to coincide with my life. That’s also ridiculous hubris.
I salute all future aliens who may ever read this, but I don’t reckon we’ll ever meet.
It is a very lonely universe. It will remain that way for quite some time.
And remember that when we’re talking about a virtual infinity of time before us and after us, there’s no really good reason to assume intelligent life will reach us anywhere near now. It could be a trillion years in the past or the future.
OP here. The staggering part is what fills me with awe and a bit of giddiness. Yes, I was suggesting that, in this mind-blowingly vast universe, I bet there are literally billions upon billions of crevices with just the right amount of sun and water and whatever else is required to harbor life [the comment upthread about the lack of barnacles on asteroids was kind of a reality check bummer, admittedly].
And, when you get into the sheer size of the universe - and consider the incredibly varied and adaptive life that exists on this planet (part of this OP was inspired by a Fresh Air interview about bugs in the home, and how impossible it is to avoid the vast array of microbes and other simple things that exist in the world) - that still leaves a few million (or more?) species out there that have likely adapted to a state we would recognized as advanced and civilized.
What makes it tantalizing, to me, is the fact that the vastness of the Universe means that this hypothesis is possibly correct, and yet we will never have the ability to reach out and connect. We could be part of a much huger “colony of humans”, but our puny lifespans and slow moving mass means we are still effectively alone in the crowd.
I love this hypothesis and it makes sense to me. Still, if it’s an effective adaptation for us, then surely it would have been replicated amongst other warm blooded males with opposable thumbs that might be thousands of light years away.
Are you a Steady Statist or something? The Universe has been around for much less than 1 trillion years. 13.7 billion years, roughly. And for the first 6 or 8 billion years of that, it probably didn’t have enough metals (elements heavier than helium) to make decent-sized terrestrial planets. Furthermore, a trillion years from now, the only stars left burning will be the lowest mass red dwarfs.
And that’s the Universe at large. Since you talk about “reaching us”, the Earth has only been around for 4,5 billion years or so. It only has half to one billion years to go before the sun heats up enough to evaporate the oceans (assuming we don’t do anything about that, of course).
I use exactly the same phrase as the OP: “teeming with life.” And I have very little doubt that there are intelligent beings who are able to travel huge distances, in spite of our puny limitations.
How do you know? Educated guesses are the best we can offer. What’s wrong with the steady state model anyway? Or perhaps the universe is a series of big bangs and big condensings. Whether it’s a trillion, a billion, a million, a thousand or a hundred years, there’s no really good reason to assume other life and especially advanced intelligent life is existing at the same TIME as us. To assume this seriously underestimates the scale of the universe both size wise and time wise. Other civilizations could have burned out long ago or be a long time yet to come. It would sure be CONVENIENT for us if we could contact them now, but it is not a reasonable wish.