A SETI Day Q and A

As I've mentioned as recently as yesterday, I'm involved in SETI, the Search for Extraterrestrial Intelligence.  Since our organization has a website, I haven't felt it necessary to do any major SETI babbling on my blog.  Normally our communication with members and others is conducted by our executive director H. Paul Shuch, who is also the webmaster.  However, once in a while a question is directed to me, and you know my theory on "conservation of text."  I seem to have been given an "essay question," and rather than simply reply to the sender, I thought I'd expatiate here, since it's a general question rather than some administrative matter.  My thoughts are interspersed with John's inquiries, much like the galaxies in the vastness of the universe, although on a somewhat less grand scale.

From John, 14 September 2006

I have recently read several books on cosmology and astrophysics. Our universe and its mysteries are fascinating subjects especially when considering the possibility of life elsewhere in our universe. A few questions come to mind.

Books on cosmology and astrophysics are my favorites, too.  (See yesterday's blog for one of the more imaginative ones!)

1). What are your thoughts concerning the Drake Equation? Do you feel it comprises an accurate method of determining the probability of extra-terrestrial life? Are there any other equations supporting or opposing the Drake Equation conclusion?

The Drake Equation itself is an entirely satisfactory way of determining the probability of ET life.  However, I don't believe there is a "Drake Equation conclusion" since the numbers that it requires range from the fairly definite to the purely fanciful.  You can make it come out however you like by varying your assumptions.

2). Regarding the magnitude of galaxies within our universe is it correct to conclude that based on their sheer number this fact is sufficient from which to infer the existence of Earth like planets elsewhere when considering:

(Not to ruin the suspense for A, B, C, and D, but "yes.")

A). The enormously large numbers of variables in: Types and chemical composition of galaxies, stars and solar systems along with propitious planets regarding core and overall mass composition, chemistry of atmosphere, orbital distance and circularity from a suitable star, asteroid belts, sufficiently massive moons and nearby further out large planet or planets (to intercept sufficient numbers of asteroidal and cometary impacts on suitable Earth like planets thus diminishing non-propitious impacts themselves causing excessive numbers of extinctions (as happened 65 Million years ago on Earth regarding the Dinosaurs from which the emergence of human beings became possible... 62 Million years later).

It sounds like John is arguing that all the above conditions are necessary, including, perhaps, even a dinosaur phase, before humans can emerge.  At least one obvious counter is that if the dinosaurs had not been rendered extinct, perhaps they would have developed intelligence.  But beyond that, nobody really knows how many of these special conditions are necessary or even desirable for life to develop.

B). The existence within spiral galaxies of a very narrow metallicity enriched habitable zone in which chemistry is 'right' regarding element abundances for life in any form to emerge. As I understand it this narrow zone exists due to over the ages an appropriate number of super-nova explosions occurring thus allowing for the seeding nearby of space with proper element composition and abundances. It is claimed that outside of this narrow zone elements compositions and abundances would not favor the formation of suitable Earth like planets.

A "narrow zone" in a galaxy is a pretty big place nonetheless.  For example, all the refrigerators and freezers (including walk-in!) built on earth since the beginning of human life wouldn't be large enough to encompass even the tiniest fraction of a galactic "habitable zone."  And, of course, we're not all that sure that a habitable zone is, or a (hypothesized) uninhabitable zone isn't.

C). The exceeding rare combinations of circumstances on suitable planets for life to evolve to intelligence beyond ordinary animals such as cats and dogs.

I'm not sure I understand this one, and I certainly don't agree with it.  For one thing, we—all of us, scientists included—really don't have a comprehensive grasp what combination of circumstances is necessary for human-like intelligence to evolve.  For another, I'm sure cats are smarter than we are.  In order to put ham slices in the refrigerator,  humans have to go through an enormous number of steps and processes.  However my housemate's cat has trained me to throw her (the cat) a piece of ham when I come home, simply by standing near the refrigerator and thinking "gimme" thoughts.  I might add that cats almost certainly discovered gravitation before Newton. 

D). The age of our universe being only 13.7 Billions of years. Would not the Drake Equation be more suitable if the age of our universe were several hundred billion years of age greater? With the Milky Way being only 10 Billion years of age and our solar system and Earth less than 5 Billions years of age has sufficient time yet passed within our universe for there to be many propitious regions?

It takes a certain mind set, one I don't possess, to put the word "only" before "billion," at least when referring to time as measured in years.  In hundreds of billions of years, in fact, the universe will be a much duller and more boring place, with lots of cinders instead of stars to keep the current variant of "us" company, or so our astronomical understanding predicts.  Put another way, it has taken us only a few hundred years to go from not knowing what or where the stars are to seriously contemplate visiting them.  Given that stars and their planets have been forming and continue to form throughout those billions of years, the most likely scenario is that very few civilizations are close to our level of development, and the vast majority are either way behind or enormously ahead of us.

In light of the above considerations and perhaps many others yet to be discovered is it not possible that in fact we are alone within our universe... regardless of predictions otherwise as espoused within the Drake Equation? I very much look forward to your response. Thanks....

Not withstanding my gentle flippancy and pooh-poohing of some of the arguments above, it's at least possible that John is correct.  The best argument for being alone in my opinion is the simplest:  If we're not, where is everybody?  This is known as the Fermi Paradox, and books have been written on the subject.  Even I weighed in with my discussion of Nirbs.  We simply don't know enough to answer the question conclusively, or even tentatively.

As a matter of personal belief, which, along with 50 cents plus shipping will get you a fine UPS on eBay, I think it's unlikely in the extreme that we're it.  Yet it doesn't matter what I believe or what John appears to believe.  In the general scheme of things, the SETI program—ours and those of other organizations and scientists—costs society much less than the unpaid taxes of people who spend their time writing blogs instead of toiling productively.  (Which subject will be covered shortly; it's not easy to escape my ruminations.)  So, space aliens or none, the question of whether we should be searching for them is trivially easy to answer:  It costs almost nothing, and the reward for success is potentially spectacular.  If entrepreneurship were possible in astronomy you couldn't ask for a better business plan.