As the year 2020 draws near, those who emphatically professed conclusive evidence for extra-terrestrial life would be found by then, are getting a bit nervous. But there is good news - a rocky planet, Proxima-b, has been found in the "habitable zone" just a mere 4 light years away. All that remains now is the "contact," - or perhaps spectral evidence of oxygen, water and methane before uncorking champagne bottles. We are now months away from the declaration that life on Earth is not unique, albeit, by proxy evidence. The space agency, as usual, is ahead of schedule.
Boring statisticians have devised constructs such as prior and posterior probabilities of expectations - something ET enthusiasts appear to have little respect for. They have left Enceladus, Saturn’s beautiful moon, the most promising for life in the neighborhood, in the dust with the news that Proxima-b has been found, for conjecture is more powerful than facts and spectra, more beautiful than actual measurements. Before the space agency devises methods to test for life on Proxima-b, they have to ask two important questions.
1. What is the a priori probability of life on Proxima-b?
2. If they do not find life there, does the posterior change in any way?
If the answer to question 1 is zero or the answer to question 2 is no, then there is no logical reason to explore the rocky cousin. We already know there is no "advanced life," there because if there were, we would already have been at war with them.