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It's certainly a possibility. But only one of many.
How long have we seriously been looking for extraterrestrial life? 60 years? Given the vastness of the cosmos, a little bit of patience might be in order.
How long have we had the proper tools to find extraterrestrial life? On this, there's absolutely no way to answer.
Also actually being able to recognize alien life must be difficult. Do they even exist in a state that we could detect?
We made our first radio waves a little over 100 years ago. Even if aliens were there to listen, the signals wouldn't be all that far by now.
And who's to say they would even communicate via radio waves? Radio waves are already becoming obsolete for us. Imagine what a civilization 10,000 years ahead of us might be like.
Also actually being able to recognize alien life must be difficult. Do they even exist in a state that we could detect?
What we'd look for to identify life is: structural complexity; some sort of metabolism; active response to what's happening around the organism; growth; reproduction; a mechanism for passing that complexity to the next generation while allowing for natural selection (without natural selection, there will be no speciation and in effect, no biology).
Since the first views of Titan close up, biologists have been thinking about the sort of biochemistry you'd have in an environment that's several hundred degrees below zero F and has oceans of liquid hydrocarbon. Water can't be a solvent, because at those temperatures it's as hard as granite.
So yes, people are considering what life would look like in an utterly alien environment. And the possibilities are limited because the periodic table will be the same no matter what the star system or galaxy; you can only roll the dice so many ways, and the best basis for any kind of self-replicating life is carbon.
If you're asking would the actions of intelligent life be completely unintelligible to us, I believe it's unlikely for a number of reasons. All organisms including humans strive for self-preservation and preservation of their genetic material. We are motivated by a number of other things, including curiosity about the world around us. We've discovered things about the world around us using the scientific method and mathematics, and those will be universals no matter where you're looking in the universe.
So what would motivate an intelligent species to attempt contact with other worlds, or go off-planet?
Attempting contact - curiosity, some ethical or religious reason, a desire to find others like themselves, or some weirdness in their view of the universe or themselves that makes sense within the context of their biology and environment but not in ours. Because of the expense involved, a major effort would need to be worth it to them. Economics will be economics, no matter where you find it. We're not going to engage in a multi-trillion dollar centuries (or millennia) long effort to find other intelligent life; what we're likely to do is a more realistic passive program of looking for the signatures of life and intelligence in other star systems. For the reason of basic economics, any aliens like us will do a cost-benefit analysis before committing their species to an effort of this magnitude -- and it's hard to imagine that making contact would be worth it, unless they're motivated by some weird religious belief system. Or unless they reach a level of sophistication where cheap FTL travel is possible.
Going off planet - I think that one's actually easier: long term survival. We're starting to understand how truly fragile our continued existence here is. Aliens would realize the same thing, and after colonizing their star system and exploiting its resources, be motivated to move outward for survival. Why? Because survival will be programmed into the genes of any species that survives and thrives. If it weren't, they wouldn't survive and thrive, no matter how "alien" they may seem.
Who is to say they aren't all around us but just aren't interested? The last time I went for a stroll in the woods, I didn't take the time to stop and converse with the ants. If there are advanced civilizations out there, they may just be completely disinterested in us. ...
See my later post -- I think if a really advanced civilization is out there, there's little reason from an economic perspective for them to find us. I can't recall a lot of discussion of the economics of contact among SETI types; fact is, a species isn't likely to invest a lot of resources in finding primitives (other than passively by remote observation), and barring some breakthrough in cheap FTL travel, won't be particularly motivated to spend enormous amounts of resources over centuries to reach the stars for "research" (species survival is another matter).
so many empty spaces and planets, it's hard to believe it's really empty considering only robots and machines have been there, not humans. I would think the so called "parallel universe" I keep hearing about yet I know nothing about it makes me think that other planets have different things going on than Earth that we can't see "Aliens", and they can't see Earthlings either. Just because we need water, doesn't mean other inhabitant of other planets do.
One possibility is that the universe is full of intelligent life but Earth life is the oldest. If all the others are at the technological stage we were in during the 1700's, or farther back than that, none of them would have communicated with us yet. It may seem improbable, but someone has to be the oldest. So why not us?
What if there were no humans? How long would it take for whales and chimpanzees to develop interstellar communication and space flight?
Maybe all we have to do, to be surrounded by intelligent life of all kinds from our whole galaxy, is to simply wait patiently for a few million years till they develop the technology and arrive here.
In these discussions a lot of people leave out the time factor in space-time. The light from the stars we're seeing took hundreds or thousands of years to get here. Earth may have had a number of callers but we weren't there to answer the phone -- in the scope of Sagan's universal year we've only been awake for a few seconds. We've only been looking for less than 60 years and quite frankly we're not looking very hard. We've only been able to detect and categorize exo-planets for about 25 years. That's a few dozen years out of billions that aliens may have reached out or visited. If they came 1 million years ago (a few days before we woke up), they would have seen animals and plants. No humans or anything like humans. If they came 1 BILLION (4 months before we woke up) years ago they would have seen some microbes on a generally hostile environment planet. If they came 14,000 years ago (5-6 minutes before we woke up), some ancient humans would have been in awe, but we have no records other than a few relics and cave paintings of ANYthing humans did, saw, or knew in the year 12,000 BCE. So there's no way to know.
If there's anything we've learned from exo-planet research is that we did not know what we did not know. There are star systems out there that are vastly different from ours and vastly different than what we thought possible, ie: planets the size of Jupiter as close to their star as Mercury. We didn't think those could exist before we detected one. Now we know there are many "hot Jupiters" out there. We're still not very good at seeing planets that are smaller than "super-Earths," planets substantially larger than Earth but smaller than Neptune, around 10-20 times Earth's size. Seeing Earth or Mars-sized planets in the habitable zones (where the distance from its star makes it likely that water is in a liquid state).
Kepler just detected the first earth sized planet in a habitable zone in 2014. Kepler 186f is 500 light years from Earth. If there are people there at our level of tech that started using radios when we did, we will not hear their broadcasts for several more centuries.
Also, we should keep in mind our own limitations. Presumably, aliens went through a process of evolution like we did. We humans evolved from ape-like ancestors. We think like apes, act like apes, have motivations like apes, and emotions like apes. Imagine how differently a sentient creature evolved from octopuses would think. Nothing like us. They may not care to broadcast radio signals or to even build things the way we do.
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Would you mind giving a clarification of what that means? What kind of dimension?
