SETI: The Search Goes On

7 Replies to “SETI: The Search Goes On”

1. I so totally agree! Yet I remain very concerned about the reaction from religious fundamentalists or zealots around the globe. An advanced extraterrestrial civilization would no doubt realize this too, having probably been there before? Perhaps this ‘complication’ makes ‘them’ very circumspect, even hesitant to come forward? That would go a long way into explaining why we haven’t heard from them yet…

   I say – “Come on down! We’ve been practicing (ET, Star Trek, My Favorite Martian and etc.) for your arrival!”

   1. They won’t come here, you know.

      Inhabiting existing biosheres is both hard work and risky. You have to fend off the invading species that won’t play nice with your own introduced biosphere. Even more so if you try it on a world with intelligent, and especially warfare technology competent, species.

      And without an economical reason (no colonization, better science if you barter it), there is no reason.

      1. Our bio-technologies, not unlike all of our other sciences, can hardly be considered advanced. I will assume that any interstellar civilization’s sciences would be far and away much more advanced than our best minds can even imagine? And yet… a scenario. ‘They’ are here already! It’s us….

2. I am of two minds about SETI. On one hand I think this is a form of snark hunting. I think the density of intelligent life is very low. While there may be tens or hundreds of thousands of planets with life I hold to my estimate there are only around 1000 complex bio-planets comparable to Earth. The probabilities any star in the galaxy has ETI coincident with us, or should I say on our past light cone, is about 10^{-3} This leads to my second opinion. Null results within this galaxy will put some upper bounds on the occurrence of intelligent life in the universe. The experiment is the worth doing from that perspective.

   I think the search for life is far more likely to be fruitful. We may have basic life or ecosystems in our own backyard on Mars or inside the icy Jovian and Saturnian moons. The search for life on Mars is worth pursuing, a fly through of the geyser jet from Enceladus would be interesting and other local searches are scientifically valuable. More distantly we may look for chemical signatures of life on extra-solar planets.

   If we find life on other planets the implications for ETI are of course fairly strong. The problem is that the nearest ETI bearing planet may be 100 million light years away.

   LC

   1. Cogent thinking. Personally I think that life must be very common. Intelligent life is a whole ‘nother can of worms. It may be very difficult to get started and it may be, shortly thereafter, self extinguishing.

3. Of course we should do SETI as much as we do other forms of observations or constraints.

   However I can’t agree with Drake that SETI in and of itself will pay off. It is in general very iffy to predict what research will pay off, at least on initial constraints. (As a counter example, it isn’t very hard to predict that genomics will pay off in the current run to provide everyone with their genome data.)

   But we know that science as a whole has a high ROI, especially when it is unconstrained. So we should do this.

   Now I have to diverge from lcrowell’s models. I find the area complex:

   A. What SETI won’t provide is very firm constraints if it returns a negative observation. We know this from Fermi’s question, because it has a lot of unobservable pathways.

   Constraints on negative outcomes:

   1. As an example: The null hypothesis on colonization is likely a slowly spreading Oort cloud one, which will be radio silent for economical and cultural reasons of quickly divergent biospheres.

   But there are unobservable pathways like it. Too short civilization time et cetera.

   2. The biologists can be correct. Language competent species are as rare as trunks on Elephantidae, i.e. both very handy [sic!] but in practice a trait that occurs once in a blue moon.

   B. However, SETI can very well return a positive observation.

   Constraints on positive outcomes:

   1. The other feasible interstellar space economy besides colonization is information barter by some form of light speed signaling.

   2. Habitable planets should be inhabited at a high rate after a few billion years, predicted by the observation of rapid occurrence.

   Modeling ETI rate from inhabited occurrence is again a loose practice, see A and especially 2. However the natural null hypotheses may be to look for land “worlds” between mass extinctions, since diversity before and after is very much independent.*

   Having seen 3-4 such “worlds” here, with one having an ETI equivalent, means again that ETI’s is fairly common. Especially as we expect similar mass extinction episodes in other biospheres.

   The frequency of water worlds in the habitable zone of stars should be low. It seems inner planets are naturally dry from recent planetary system formation models.

   In sum, while we can’t put firm constraints on ETI rate, it can be very high at best. It is premature to predict what SETI can, or will, yield. And I think this is the official position of the SETI workers.
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   * There is claimed to be an increase in niche availability over time though. I don’t know how it squares with diversity measured as number of species or other consequences for ETI rate. (Say, would increased niche diversity imply increased trait diversity?)

4. I say let the search go forward (although I personally wouldn’t contribute a dime to it) if people want to fund it. My own suspicion is that the answer to the Drake Equation is one (i.e., us), at least for this galaxy.

   But it’s far more important, scientifically, technologically, and culturally, to continue the search for life here in our own solar system. Let’s get a manned mission to Mars, probes to the interiors of Europa and Enceladus, an orbiter around Triton, and maybe drop an aircraft or balloon into the Titanian atmosphere.

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