Frank Drake Lives On In The Spirit Of SETI

  • The astronomer's equation helped the international scientific community to launch a coordinated human search for extraterrestrial intelligence.
  • Drake passed away aged 92 on 2 September 2022.
  • Aravindan NeelakandanThursday, September 8, 2022 11:41 am IST
    Astronomer Frank Drake speaking at Cornell University in Schwartz Auditorium, 19 October 2017 (Photo: Amalex5/Wikimedia Commons)
    Astronomer Frank Drake speaking at Cornell University in Schwartz Auditorium, 19 October 2017 (Photo: Amalex5/Wikimedia Commons)

    Looking up at the stars in the cloudless night sky is an experience that combines awe with a sense of cosmic loneliness.

    Humanity has yearned to establish contact with beings from beyond, perhaps since the very dawn of human self-awareness.

    With the arrival of telescopes and revelation of worlds beyond our own Earth, the imaginative quest that earlier gave shape to mythological beings in the sky began offering shape to extraterrestrial (ET), intelligent beings from other planets.

    Imagined sometimes as god-like and many more times as malign invaders, beings from outer space started populating the newly developed genre of science fiction, and soon enough, real science began its search too.

    From Martian canals, speculated as signs of engineering by Percival Lowell in 1894, to the ‘Wow’ signal discovered by the ‘Big Ear’ radio telescope of Ohio State University in 1976, many alarms have been raised — most of them false and a few still being explored.

    In the current century, astronomer Jason Wright of Pennsylvania State University proposed in 2015 that the dimming of light from a star spotted 1,480 light years away could have been a result of Dyson spheres-like super-structures built by an ET civilisation.

    But, within a year, this hypothesis made way for a more natural cause, such as that it originated "from a large number of comet- or planetesimal-mass bodies."

    More recently, Abraham "Avi" Loeb, a theoretical physicist at Harvard University, put forth a formidable hypothesis that Oumuamua, the interstellar object we discovered in 2017, could have been an artefact of an advanced civilisation.

    Behind all such lines of thought is an equation, sometimes considered obsolete, yet one that provided a mighty scientific push to the search for extraterrestrial intelligence — the Drake Equation.

    On 1 November 1961, in an informal conference on the theme "Search for Extraterrestrial Intelligence (SETI)," astronomer Francis Drake offered a formalist framework for facilitating the search of ET with respect to our galaxy.

    Today, this is famous as the "Drake Equation". It reads thus:

    Image: SETI Institute
    Image: SETI Institute

    Let us look at each of the terms:

    N represents the number of possible ET civilisations

    R is the rate of star formation in the Milky Way galaxy

    fp is the fraction of those stars with planetary systems

    ne is the number of planets in a particular zone around the star, a zone with conditions that favour the evolution of life, in the fraction of stars harbouring planets

    fl is the fraction of planets in which life actually evolves or has evolved

    fi is the fraction of planets among those in which intelligent life evolves

    fc is the fraction of planets even among those planets with intelligent life in which a technological civilisation has the capability to send and receive signals from other such planets or has evolved other ‘contact’ technologies

    L is the longevity of such a civilised intelligent life form

    This equation is more of a framework than a formal equation to be solved.

    R, or the rate of star formation, has been changed to N* ,where it represents the number of stars in the Milky Way galaxy.

    Astronomer and educator Carl Sagan wrote about the scope of this equation:

    One of the great virtues of this equation, due originally to Frank Drake of Cornell, is that it involves subjects ranging from stellar and planetary astronomy to organic chemistry, evolutionary biology, history, politics and abnormal psychology. Much of the Cosmos is in the span of the Drake equation.
    Carl Sagan, 'Cosmos'

    Based on the scientific data available then, Drake in 1961 estimated N to be 10.

    Five years later, Sagan made a calculation based on the basic Drake equation, with some modifications. He came to the conclusion that for the Milky Way galaxy, the number of possible ET civilisations is one million.

    Many numbers have since been suggested that lie between the estimates of an overoptimistic Sagan and Drake.

    The Drake Equation also has an existential lesson for us — a possibly relatively young technological civilisation in the galaxy.

    The term L points out that a technological civilisation can bring itself to extinction. There is longevity associated with life.

    For Earth during the time of Drake and Sagan, there was, for instance, the possibility of a nuclear holocaust as a result of the Cold War.

    At present, nuclear holocaust is still a possibility on account of a fanatical rogue regime using a nuclear weapon, but now we also have to contend with an ecological doomsday scenario.

    When we receive a signal from a civilisation thousands of light years away, there exists a distinct possibility that the civilisation might have become extinct by the time we received the signal.

    The Drake Equation has its critics as well.

    Professor Loeb, for example, in his latest book Extraterrestrial (2021), points out issues with the very basis of the equation's framework:

    … Drake’s equation focuses solely on the transmission of communication signals; he limited his aspirations to finding N and from it the number of interstellar communications that would establish the existence of extra-terrestrial intelligence. This exclusive interest in communication predicts the equation’s second limitation, epitomized by its variable L, which represents the length of time an intelligent species would be able to produce such signals.
    Avi Loeb, 'Extraterrestrial: The First Sign of Intelligent Life Beyond Earth'

    According to Loeb, the equation's constraint comes from its focus on the electromagnetic signal than on what he calls the ‘technosignatures’ of possible ET civilisations.

    All said, as Drake passed into eternity just days ago, on 2 September 2022, the equation he authored helped the international scientific community to launch a coordinated human search for extraterrestrial intelligence.

    The equation — whatever its critics may say, and even accounting for the possibility that it may have become irrelevant — makes us ponder deeply about our place in the cosmic canvas.

    It dissolves our artificial boundaries and offers the realisation both of our prime importance and utter insignificance. It is both a humbling and elevating experience, in the vein of all sublime spiritual experiences.

    Frank Drake lives in every attempt we make for contact. He will become quite an interplanetary hero if and when we do make that contact.

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