SETI & Sentient Aliens 

New 03 Sep 05: What MUST Sentient Aliens look like? (See bottom of page.)

How many times have your read the Drake equation-- a statistical analysis of the number of possible "intelligent communicating civilizations" there are in the universe. The equation multiplies the probable number of planets per star, stars per galaxy, number of galaxies, etc., etc. to come up with a very high probability that the universe is crawling with sentient life. Wow--wouldn't that be fun?

                 N = N* f_p n_b f_l f_i f_c f_L  

The Drake equation is hugely suspect because with all the things it throws into the mix, it manages to leave out the kitchen sink--the possibility of the existence of sentient extraterrestrial life. The blithe assumption by these astronomers in one factor (fl) is that "50% of those earth-sized planets (is) where life actually evolves." The cheery estimate covers up the unspoken assumption that ubiquitous bacteria will easily evolved into sentient life, an assumption blithe enough to make biologists weep.

Biologists, that is people who have some idea about living things, find the evolution of higher life forms on Earth to have been due to an incredibly--perhaps not repeatable--set of very unusual  circumstances. First, the Earth had an unusually large moon (not found in the Drake equation). This moon is large because it was probably a captured body (not found in the Drake equation). This huge moon caused enormous, mile-high tides that washed salt water -- not fresh water--hundreds of miles onshore (Not Found in the Drake Equation = NFDE). The mixing and filtration of the runback over chemicals of the Earth's crust then essentially assembled compounds that eventually became alive (NFDE). The atmosphere of the Earth just happened to be right for this anaerobic activity (NFDE). Were it to have been oxygen rich -- i.e., what we would today call "life-supporting"-- the low-level proto-organisms would have oxidized and could not have survived to assemble into living things (NFDE). So the timing of these huge tides had to coincide with the presence of a noxious to us, but benign to them, atmosphere (NFDE). There are many, many other such oddities in birth of higher life on Earth birth.

So far we are only talking about a few of the many precursor conditions for the creation of sentient life. We've not examined anything about what the actual likelihood that complex life spontaneously arises even under the above physically unusual and biologically ripe conditions. Of course the above is just a theory -- but at least it is a theory, which -- unlike the Drake equation--actually addresses the complex and contentious issue of the rise of life. Because of the concatenation of these highly unusual events in exactly the right sequence, a biologist has good reason to believe that at this moment, mankind may be the ONLY sentient creature in the universe.

The Drake equation may be a fine estimate about how many small rocky planets circle stable stars, but--as mere statistical supposition--it can say little about the likelihood of life occurring on them, and nothing whatever about evolving to produce sentient beings. It just assumes that, given some bacteria, somehow, sentient beings will follow. Prayer might be equally efficacious... This is why the expeditions to Mars are so important to the SETI folk. If there is no evidence that life forms beyond bacteria ever arose on Mars, which seemed briefly to have had liquid water, then the Drake equation is seriously damaged. And we may really be alone.

There is another practical difficulty--that of the life-span of civilizations and the distance between any putative alien neighbors.  If a sentient civilization lasts, say generously, 50,000 years, and needs 10,000 years to get radio transmission, it has a 40,000-year radio transmission life.  This means a single two-way communication can take place with a civilization no farther than 20,000 light-years away. So that bounds the absolute radius of communication.  But the idea of waiting 10,000 years for an answer sent to planets that seem to have oxygen and water around them, does not seem like a very fruitful endeavor.

There are about 5000 stars within a radius of 50 light-years.  From that I extrapolated that there would be 50,000 stars within a more realistic 500 light-year radius of Earth.  That would mean a single Q&A with sentient aliens would take 1000 years!  (If Columbus had sent out a query to the stars, they would be getting the call about now.) Using the Drake equation liberally, I came up with 2 possible sentient civilizations within reach in that volume of space.  So even if the rest of universe is teeming with sentient aliens, we are unlikely ever to make useful contact with any of them.  Boo-hoo.

Finally, given the difficulty of linguists to decipher human Egyptian hieroglyphics and the fellow human Mayan writings, I would like to see an example of two earthlings--say an Arab and a Finn--being able to understand each other's language enough via Morse code to be able communicate usefully.  (And please, no glossy appeal to "mathematics" as if that solves anything.)

For an excellent critique of a sentient alien population explosion, read the fascinating book Rare Earth: Why complex life in uncommon in the universe, by Peter Ward and Donald Brownlee.  See also: http://www.setileague.org/reviews/rarearth.htm

Here is an invited answer to the above essay critical of the SETI equation:

Quantifying our Ignorance

By H. Paul Shuch, Ph.D., Executive Director
The SETI League, Inc. www.setileague.org

A standard tool of the SETI trade is under constant attack.  And although I enjoy a good argument as much as the next man, it's clear to me that the detractors are clueless as to the very purpose of the tool they so eagerly denigrate.  A case in point is a recent critique on the Forbidden Knowledge website of Velocitypress describing the Drake Equation as "a statistical analysis of the number of possible 'intelligent communicating civilizations' there are in the universe."  This summary misses the whole point of a powerful scientific tool, which is not really an equation at all in the strictest sense, and was never intended for the solving.  A brief history of the Drake Equation should help to illuminate its true utility.

The modern search for life in space began just over forty years ago, when in 1960 Dr. Frank Drake, a young astronomer at the newly established National Radio Astronomy Observatory (NRAO) in Green Bank, WV, launched a microwave scan of two nearby, sun-like stars. His Project Ozma search came up dry, but demonstrated practical techniques for seeking out intelligently generated signals from space.

A year after Project Ozma's brief tenure, Drake convened at Green Bank the first scientific conference devoted to modern SETI. The handful of scientists who assembled there called themselves the Order of the Dolphin, choosing recent studies into human-dolphin communication as a worthy metaphor for the challenge of interspecies communications on a grander, cosmic scale.

Drake chalked on a blackboard seven topics for discussion, which would comprise the agenda for the week-long meeting. They included stellar formation, planetary formation, the existence of habitable zones, the emergence of life, the evolution of intelligence, communications technology, and the longevity of technological civilizations.

Then Drake did something almost whimsical, which assured his lasting fame: he strung these seven factors together into an equation.

The idea was to multiply seven unknowns together, and in so doing, to estimate N, the number of communicative civilizations in our Milky Way galaxy. The Drake Equation, as it is now called, appears in every modern astronomy textbook. It is a marvelous tool for quantifying our ignorance: never intended for quantification, but quite useful in narrowing the search parameters. We still use it, not to seek a solution, but rather to help us in designing our searches for life.

Drake's seven factors are cleverly ordered, from solid to speculative.

Today's astrobiology meetings are similarly sequenced. When first published, only the first factor (the rate of stellar formation) was known to any degree of certainty. In the intervening decades, the Equation has guided our research in an orderly manner, from left to right, so that today we have a pretty good handle on Drake Factors two and three (planetary formation, and habitable zones). The remaining four factors are still anybody's guess, and it may well take decades more before our research begins to quantify those areas of our ignorance. But the Drake Equation is most valuable in guiding our research, because it asks the important questions. It is still up to us to answer them.

Although the Drake Equation detractors miss the mark with regard to the intent of the tool, they do raise a valid point which is central to astrobiology: how can life, the chance result of a painfully long chain of highly improbably events, have possibly evolved elsewhere?  One testable hypothesis, which the SETI experiment contemplates, is that it didn't have to.

The odds of life evolving elsewhere may be pretty long indeed. The best chance for SETI success may depend on the idea that life did not evolve independently, but was seeded everywhere through the mechanism of panspermia. No bioastronomer has yet disputed the possibility that microbial life can successfully traverse the distance between the stars, and thrive in a new planetary environment. So life need not generate in disparate regions independently -- a universe teeming with life merely requires one genesis event, coupled with a transport mechanism. That mechanism has been tentatively demonstrated in research by Chandra Wickramasinghe and the late Sir Fred Hoyle.

To me, microbial panspermia is a far more compelling explanation than the alien-progenitors-in-spaceships scenario, because it does not require that we warp the laws of nature, or contemplate technologies not in evidence.  Perhaps we really are all brothers beneath the skin.

Were it not for Drake's Equation, astrobiologists today wouldn't even know which of these assumptions to attack. As it stands, Drake has given us a handle on where to start. Meanwhile, there remain those who quibble about quantifying seven factors which Drake intended us merely to contemplate. They help us to establish a low value for at least one Drake Equation factor: the fraction of lifeforms that manifest intelligence.

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There you have two slants on a fascinating subject. But is this science -- or something else? Here is the last word, taken from a book review by James Hamilton-Paterson in the London Review of Books, 6 March 2003, entitled: "Forget the Klingons."

"... I cannot see why the discovery of extraterrestrial life would any longer be such a prodigious deal. Fascinating, certainly, but not miraculous; and certainly not (in Goodwin and Gribbin's words) "arguably ... the most profound discovery in the entire history of human civilisation"'. What, more than that of mayonnaise? Many of us have long had no difficulty in assuming the likelihood of life existing elsewhere in the universe. I take their hyperbole to spring from an unconscious cultural inheritance rooted in the biblically implied uniqueness of the human race. In this same mood I can see that although SETI is mediated by glittering technology, it is essentially a religious activity. The plaintive human cry 'Is anybody out there? Please?' has echoed down the millennia and now, borne on inscribed tablets and radio waves, is heading out of our solar system. Like any religion, SETI's hope of receiving an answer requires belief and occupies thousands of waking hours, often whole lives. And why not?"

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Sentient Aliens: What MUST They Be Like?