Several years ago as a graduate student, I spent enjoyable evenings discussing the assumptions surrounding the search for extraterrestrial intelligence with Charles Seeger, a noted pioneering radio astronomer at SETI who is now deceased. We argued over the infinitesimal probability of a contemporaneous technical civilization existing within a few hundred or thousand light years of our planet (more accurately, contemporaneous at the time an identifying signal is received).
We discussed SETI's notion that such a civilization would build a massive signal beacon to advertise itself; a goofy idea that SETI has largely abandoned. And, if an alien civilization existed and was able to sort out Earth-based signals from electromagnetic noise (a really tough task, it turns out), what would motivate it to contact humans? Some have suggested, as Shostak seems to think, "curiosity."
For example, in a Mercury News article last December, Shostak wrote that inhabitants of other worlds "... might notice our TV and radar signals and possibly attempt to get in touch." Yeah, right, especially after they glimpse the evening news. Others, like Stephen Hawking, have suggested, "lunch" or other less-than-benign motivations.
Shostak says that finding ET is only a matter of time and effort, and uses the Drake Equation to partly support the claim. The equation is a hypothetical, not factual, way of estimating the number of alien civilizations in our galaxy. Yet Shostak gives an optimistic range of 10,000 to 1 million such civilizations.
I invite readers to conduct a Web search of "Drake Equation issues." They will find a great deal of informed opinion around the problems of measuring most of the equation's variables, criticism about how measurement errors in such equations can yield biased and completely nonsensical estimates, along with suggested modifications and alternatives. Readers will also find much more pessimistic estimates of the incidence of alien civilizations in the galaxy than those cited by Shostak.
Which brings me to Shostak's chief assertion, "Young people... I think there's a really good chance you're going to see this (finding ET) happen."
It is unclear whether a "really good chance" is a probability of 0.5 percent or 25 percent, though it seems implied that it is over 50 percent. However vague, his estimate is merely an extension of the Drake Equation with a time component (25 years) coupled with search techniques and search intensity components of unknown effectiveness.
SETI's search for alien technical civilizations using radio telescopes is important for reasons of discovery and surveillance, and, certainly, there will be improvements in detection, search strategies, and analysis over the next several years. The odds of near-term success seem very long, though.
The slow slog of searching for any kind of alien life, like "extraterrestrial pond scum" as Shostak called it in his Mercury News article, has much better odds of succeeding. Why? Simple life forms have probably been around more or less continuously for millions to billions of years in lots of places. Technical civilizations have possibly been around for only hundreds or thousands of years in a few places (no one knows for sure, of course), and presumably have come and gone.
Searching for alien microbes, though, just does not seem to have the same impact on the imagination as searching for ET. I suggest, though, that we not get our expectations up about having an ET experience anytime soon, and some SETI scientists should tone down speculative assertions based on dubious premises that raise such expectations.
Michael Hulfactor lives on Hollingsworth Drive