This blog extends part 1 of a blog with the same title, and is followed by part 3.
Albeit imperfect, the radio search for extraterrestrial intelligence (SETI) tests a scientific question (hypothesis), “Did intelligent life get started anywhere else in the universe?” This a scientific question (not a matter of opinion), because it has a definitive answer (yes or no) that can be tested by observing nature (i.e. with our telescope). “Is there a God?” also has a definitive answer, but it is not scientific because we have no hope that observations of nature can answer this question. The God question falls into the realm of “opinion” (sound of jingling spoons) because it can be answered only by methods outside the scientific framework. (Crickets…, OK, that’s better!)
Malformed opinions about SETI topics can be broken down into 3 types : (1) science-free, (2) conflicting with science, and (3) strongly convicted statements of the “self evident” which aren’t, really.
Ignorance is bliss (science-free) Opinions
A very readable book (meaning that I could read it all the way through), “The Elusive Wow: Searching for Extraterrestrial Intelligence,” by Robert H. Gray discusses the “WoW!” signal, observed at Ohio State University in 1977. I am critical of “WoW!” because the signal did not even pass the candidate tests in the original experiment, so why should we believe it based on arguments made after the fact? A review on Amazon  speaks differently. It discredits Gray’s book with the argument that, signals from far away are very weak. Wow! That’s convincing. Especially compared with actual science showing that an Arecibo-like transmissions from nearby stars can be detected, right now, by us, if we look hard enough.
Anti-scientific Opinions (conflicting with science)
A certain blog  states that there are even (50-50) chances of finding intelligent life around the recently-discovered exoplanet Kepler 186-f. Remember, Kepler 186-f is a “goldilocks” planet orbiting a star 500 light-years from ours. 186-f is almost the same size as Earth, presumably a rocky planet and in a “hot” (that is, not hot) orbit around its star to keep the temperature just right (that is, possibly close to a temperature) where (microbial) life (as we know it) can flourish (that is, be not immediately destroyed). And then the life must be intelligent like us and be actively transmitting in our direction. 50-50 chance, huh?
In round numbers, all targeted SETI searches until now show that fewer than 1/1000 “likely” stars harbor planets that are intentionally beaming signals toward us.* We think 1/1000 is still a pretty big number compared to something like 100000000000 planets just in our galaxy. Even better, exoplanets discovered by the Kepler telescope and other probes show that most stars have planets, and somewhere around 1/5 of stars host “habitable” planets that are favorable for the evolution of life. Promising indeed. Even so, these probabilities don’t add up to a 50-50 chance of finding intelligence.
*Are you surprised that 50 years of SETI research can say no more than that? This actually shows how little effort (money) has been expended over the years to do SETI. Not for lack of scientific interest, but simply because scientists have to eat. Write your congressional representatives and urge them to support funding for SETI research.
If anyone wants to place a bet, we have insider information on Kepler 186-f, thanks to first author Elisa Quintana, a scientist at the SETI Institute. In the few weeks between submission of the paper and announcement of the discovery of 186-f, the SETI Institute pointed its telescope ATA at Kepler 186-f as much as possible (>8 hours / day) looking for technology-generated signals between 1-9 GHz. Sadly, our observations did not discover any evidence for artificial signals from that direction. So far.
This blog is continued in part 3.