The Speculations of the Contact Optimists

Now, contact optimists, like theologians, can speculate. And speculate they do. Today’s star searchers can rely on a dramatic form of speculation known as the Drake equation. The Drake Equation, first formulated by Frank Drake in 1961 (National Radio Astronomy Observatory in Green Bank, West Virginia), looks like this:

N = N* f_p n_e f_l f_i f_c f_L where

N* = the number of stars in the Milky Way Galaxy
f_p = the fraction of stars with planets around them
n_e = the number of planets per star
f_l = the fraction of planets in ne where life evolves
f_i = the fraction of f_l where intelligent life evolves
f_c = the fraction of f_i that communicate
f_L = the fraction of the planet’s life during which communication happens
N = the number of communicating civilizations in the galaxy. (Drake 1961)

The value of the Drake equation is not in knowing the numerical equivalent of N. Rather, the value is that here we have a template for structuring research and filtering incoming data. As research advances, new numbers can be plugged in. The calculations will change as new information is gathered. As of the present moment, NASA estimates that 10²¹ planets exist in the universe, of which 10¹⁰ might be earthlike (NASA, 2003, p.18). George Coyne, S.J., former director of the Vatican Observatory, estimates that there are 10¹⁷ earthlike planets in the universe (Coyne, 2000, p. 180). The mere appeal to such big numbers persuades many astrobiologists that contact optimism is justified.

The sense that discovery of ETIL is imminent has grown conspicuously since 1995, when the first planet was found around a star similar to our sun, 51 Pegasi. As technology increased to measure gravitational effects of suspected planets on their respective stars, so has the number of identified planets. These planets cannot be seen directly, but their gravitational pull can be detected by the wobble they cause on their star. Evidence of perhaps two hundred extra-solar planets is now in. As one might expect, larger planets will likely be discovered first; and those already logged seem to be Jupiter sized objects orbiting quite close to their equivalent to our sun.

Although it is not clear exactly what a planet needs to have in order to generate life or to sustain life that comes first as a visitor, astrobiogists are looking for a planet that is earth size, metal rich, and sufficiently distant from its respective sun in order to provide liquid water. It might need to provide molecular oxygen and ozone, according to NASA’s roadmap. To fit within the biophilic range, such a planet should be like the porridge Goldilocks preferred to eat, not too hot and not too cold. A Goldilocks planet would find itself in a Circumstellar Habitable Zone (CHZ). And such a planet would need to remain stable and safe for a long period of time, perhaps earth years numbered in the billions. To date, no empirical evidence that a Goldilocks planet exists is in; even though speculative considerations make many astrobiologists optimistic.

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