I absolutely believe life exists out there. Even just from working with some "Artificial Life" programming projects, it becomes abundantly clear that life simply wants to happen. Given enough time and good conditions, life will appear and thrive. So to me the question is not whether it exists, but rather:
* How common is the development of intellegence, and technological advancement?
* How close is the nearest life-bearing planet?
* How close is the nearest technological species currently in existence?
* What is the average lifespan of a technological society? If they tend to destroy themselves or move beyond something we'd be capable of detecting, we may be hard-pressed to find evidence of them.
* How many such technological societies would be doing an ACTIVE effort to make contact with other species? We're a good example of a PASSIVE society. We're looking for life out there with radio receivers, but we're not transmitting in turn. On the other hand, our planet puts out more radio signals than the sun (by many times), so we'd be an obvious anomaly to anyone looking our way.
I think finding evidence of extraterrestrial intelligence is going to be an important step for us as a society; to realize we're not alone in the infinite darkness that is space. We won't be able to hold on to many of the conceits that we have now.
Unfortunately I think SETI@Home, like the SETI projects before it, is doomed to "fail" in that it will not detect an alien civilization. It will succeed however in increasing public awareness, and having made the attempt[/i]. I think it's unlikely we'll find anything terribly soon. What I think really needs to happen is to build radio and optical observatories on the far-side of the moon, where the electromagnetic pollution will be at a minimum. We may need to discover other methods of searching as well, since most of our SETI work is based around certain assumptions about how an alien species might make their presence known in an obvious way.
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