here's my variation of the fermi paradox If they existed, and they were here, would we be able to percieve them?
Here's an interesting article that is one theory on why the Fermi Paradox doesn't really exist. http://www.space.com/searchforlife/shostak_fermi3_011129.html
Fermi was figuring that if the aliens in question, were space faring, colonizing type creatures, then it shouldn't take long for them to populate the galaxy. Based on exponential growth, where each new colony within a few generations sends out it's own colonies, then a few thousands of years or less should see the colonization process complete. Depending upon the density of habital planets, then figuring out how far such a colony would be from us is just math. But Drake tried to figure out how many aliens would exist with such technological capability. Or maybe, more accurately, how many alien civilizations exist. Fermi thought that if aliens civilizations existed then there must be some reason why we don't know it yet. Such as the zoo theorem or hands off theorem. But what if none of these apply? What if life is so rare we are the only ones? What then?
The way i see it, if we are the only ones then we are truly blessed and we have nothing to worrie about. If on the other hand there is countless civilizations then we are just another grain of sand on the beach. If you take the evolution theory as gospel then their has to be other intelligent life forms, no ifs buts or maybe's. If we are the only intelligent life forms in the universe then we can logically assume that this universe was made for us, our play ground if you like. Thing is about this question we probably wont live long enough to be able to come to a well founded logical answer.
Back to the original question of would we be able to perceive them. I believe that Arthur C. Clark (spelling?) once said that any advanced technology would take on the appearence of magic. If you think about taking the technology we have right now to some point in the past, say only 100 years, that technology would appear as magic to the people of that time. Think about it. An X-ray, being able to see inside someone's body...a cell phone, being able to talk to someone distance through a device the size of your hand...landing on the moon... If you take our technology back 500 years, then we are gods. What about a technology that is thousands of years in advance of ours? Wouldn't it be just magic to us and wouldn't they be able to stay hidden if they wanted to?
According to the Fermi paradox, if life is out there then earth should have already been colonized by aliens. But it could be that we're the most advanced civilization right now. Or maybe earth has been colonized. Maybe the evolution of life on earth has been manipulated over the millenia for some unknown purpose. Also, there has to be a first. Maybe some time in the future we will meet aliens that may try to colonize earth if they're more advanced. There are many possible solutions to the Fermi "paradox."
Another thought I have had about the SETI search and its apparent lack of results. Why do we assume that we will be able to detect any signals that some other civilization would be transmitting? If you look at the way our own RF technologies have progressed over the last 10-20 years, they have gone to a digital format that is becoming increasingly noise-like and becoming more and more difficult to detect or decode as the transmissions become more complex. Just look at Wide Band Code Division Multiple Access (W-CDMA) and Digital Television. This is a technological progression that has increased the bandwidths of our RF transmissions in order to increase the quality of services or the capacities of the RF channels. If we continue this progression, and we will, in a few short years every RF signal that is transmitted will have a noise-like characteristic that will make it almost impossible to detect at a distance on the order of magnitude we are talking about. This progression is a natural outgrowth of our technologies and we could probably expect that an alien civilization would also progress in this manner and their RF transmissions, whatever they may be, would also become more noise-like as their technology progressed. With some of the new technologies we are currently developing, such as Ultra Wideband Impulse Radio technologies, we ourselves have difficulty detecting the transmission even 30 meters away, let alone millions of kilometers. With this in mind, is it any wonder that we haven't detected anything? If you look at this technological progression in a timeline, it has taken only about 100 years for our technology to develop from the first, somewhat readily detectable RF technology to our currently difficult to detect RF technologies. This gives a 100 year window in the development of a civilization during which we could readily detect them. After this window, their technology would become increasingly difficult to detect, just as ours is becoming now. If we are assuming that they are intentionally transmitting a signal in order to be detected by civilization outside their own, then I would wonder how many times in the past we ourselves have intentionally transmitted an RF signal soley for the intentions of being detected by some other civilization? I am aware of only one message that was sent out from Arecibo, is anyone aware of others? It seems to me that our inability of detecting someone else is an almost logical assumption and that the effort is almost nearly doomed to failure without proving anything.
One of the most "trashy" bands is the interstellar hydrogen band. Is it that we have been recieving these signals and have not been able to recognize them? What if the civizilation we are trying to detect is paranoid? What if they bury their signals within the noise for increasing the chances that no one would detect them? Then all of this SETI stuff would be meaningless. Don't get me wrong, I would love for us to contact a civilization. I really think that the distances involved would prevent us from "visiting" our stellar neighbors. But it would be nice to know that we are not alone in the universe. It would also be nice to share technologies in hopes of finding that which we don't already know. The possibilies are endless in this, but have you ever had a day when things just didn't go together? When someone comes up to you and says, "Try it this way"? And you think **Duh, how could I be so dumb and not have thought of that my self** What if the human civilization is having a Duh? What if we have a blind spot that we can not see through? Something that we missed that would open up the doors to knowledge that we don't even think is possible?
Wet1, You raise a lot of good points and questions. I am always reminding myself that lack of proof for a theory does not imply the lack of truth of a theory. What was it Einstein said? Something to the effect of "a thousand observations do not prove me right, because it only takes one to prove me wrong"
SeekerOfTruth, Another point you bring up that I would like to comment on. You mention a timeline of technology progression. This has long been speculated on by those trying to contact extrasolar civilizations. The idea that not only has the ability to detect those signals we send required but that the civilization in question (wherever they might be) must be within a certain span of progression to make sense of them, and that further there is a chance that a civilization may not even exist when the return signal arrived saying "We heard you!". If we send the signal and it arrives during the caveman era of their progression then it is a lost chance that went by unknowingly. If the signal arrives after using say laser transmissions then it is rare that they will even notice it. (After all the very first thing that happens with a new tech is that it is put to use. Then manufacturers use that tech to improve whatever product is made and no more of the old is made. When was the last time you used a radio with galilium crystal, razor blade, wire, and safety pin?) If it takes 100 years for the signal to travel one way and they have say a global wide nuclear war, capability to recieve the returning signal is gone by the time it arrives. So this narrows the chances of actually making contact by a large margin. No longer is the idea that they are just sitting there with their ears to the speaker waiting for us to say hello, but we also have a narrow band of time to fit within. The last estimate I heard was within a couple of hundred years or so of our own tech abilities.
