So, when are we going to discover if we are alone?

Mods, this may be better suited for IMHO, so if you see fit please move. There may have been a thread on this but my quick search didn’t turn one up…
How much longer is it going to take before we pick up some faint alien transmissions of their version of “I love Lucy” or something like that? I read in a book somewhere (please don’t ask which, I don’t recall) and the other “somehow” figured out that we will more than likely recieve alien transmissions in the present generations lifetime… so I guess sometime within the next 50 years. Can anyone think of a real basis for that number?

Would an Arecibo size dish be capable of picking up transmissions the strength of our 50’s TV signals from, say, 200 lightyears away? Would we even know what they were?

I am just curious as to what some of our fellow dopers minds think of this.

I personally believe there must be other life somewhere not too far away (relatively speaking) just by the sheer number of stars and presumebly planets. Why haven’t we heard them yet? Is it possibly we, the human race, is the most advanced society/species in the neighborhood?

If there is life on another star, does that necessarily mean that they transmit signals that could be detected with a radio telescope?

The odds are in favor of ET life, but heavily against discovering it.

The problem is not so much doubting the existance of ET life. The hard part is finding an inteligence that has evolved to a technological age but hasn’t yet destroyed themselves.

What period of a race’s lifetime is graced with technology that is capable of listening to the stars? We have only ourselves as a reference. on the cosmic calendar, 50-some years of technological ability is nothing. If the aleged ET race began their evolutionary process just a few hundred years before we did, then they might already have snuffed themselves out. If they began evolving just a few hundred years after we did, then they haven’t reach a sufficient level of technology to be able to communicate yet.

The error is compounded by the assumption that two different planetary races might not necessarily evolve at the same rate.

Your question actually touches on one of the chief criticisms some people have of the SETI effort - it’s not falsifiable. There is no point at which we can simply pack up the radio telescope and go home, having decided that nobody’s going to answer. These leads some people to label it as “bad science”.

Personally, I view it as a very, very long shot with a huge potential payoff. It might be a badly designed experiment in the strictest sense, but I haven’t seen any of the critics designing a good one to address the question. The critics who have a point are those who simply suggest that the resources may be better utilized elsewhere.

As for how far our own signals are intelligible, I’ve heard a lot of conflicting statements on that. The pessimists have stated that nobody beyond the orbit of Saturn would be able to recognize anything. I’ve also heard other people point out that the Earth radiates the radio flux of a small star, and any reasonably curious aliens close enough to us would certainly notice the very atypical RF radiation emanating from our neighborhood, even if they didn’t notice any artificial patterns in it at first.

Arnold’s question is also relevent - we’ve been using broadcast radio signals commercially for the better part of a century now. 100 light years out is still essentially just the local neighborhood. How do we know that 100 years from now some technology we currently don’t use won’t supplant it (for the most part - old technologies rarely go completely out of use). We could be looking at a very narrow band, even for alien beings who develop in the same way we do.

It’s also relevent in the sense that an alien culture may simply have no use for radio transmission, rather than having evolved beyond it. Maybe they’re a connected “group mind” of some sort for whom “communication” in the sense we think of it is unneccesary. Maybe they have a very static culture which remains content with slower communication and transportation while developing in other areas.

If we put an exact duplicate of our civilization around Alpha Centauri, then neither one of us would be able to pick up the other’s transmitted signals. There’s a chance we might pick up military radar, if it were pointed in the right direction, and if we were deliberately transmitting for the other to hear, we could, but we haven’t sent very many deliberate messages to the stars. Anyone who’s talking about aliens watching “I Love Lucy” is presuming that the aliens have receiver technology orders of magnitude better than ours, and that they’re deliberately looking for us. Saying that we produce the radio output of a small star is misleading at best, since most stars produce very little radiation in the radio range.

On the other hand, if you’re just interested in life, and you’re not concerned with intelligence, then we have a fair chance of finding it in about twenty years or so (I think that’s the time range NASA is looking at now). There’s a planned mission called TPF (Terrestrial Planet Finder) which would use a space-based optical interferometer to look for planets around other stars. It would have sufficient resolution to spot planets directly, and to get some spectral information on any atmosphere the planet might have. If we see molecular oxygen or ozone, that’s paydirt: There’s no abiotic process which can produce significant amounts of either in a planet’s atmosphere, and most life as we know it would be inevitably associated with free oxygen.