Rare Earth: once again, how rare? (Introduction)

by David Turell , Friday, September 02, 2016, 01:00 (3005 days ago) @ David Turell

Another article takes a stab at considering our rarity:-http://www.evolutionnews.org/2016/08/is_earth_the_mo103093.html-"Not all terrestrial-like planets are habitable or can even permit liquid water at the surface. Furthermore, X-rays, extreme UV radiation, and flares make it unlikely that planets around M-dwarf stars are habitable; this removes 98 percent of the terrestrial planet candidates. If super-earths with high gravitational fields are removed, Zackrisson et al. estimate that about 2 x 10^18 habitable planets remain in the observable universe. In addition, they note other factors that would further reduce the number of habitable planets, such as cosmic rays, Oort cloud comet perturbations, interactions with interstellar clouds, the effects of dark matter, and radiation threats to life. They also point out that the vast majority of habitable planets would be far too young to have evolved advanced life, leaving only a tiny fraction of candidates.-"That introduces another problem to overcome. Even if one has a habitable planet, there is no guarantee that life will be found there. Zackrisson et al. state:-"If the probability for the emergence of intelligent life is sufficiently small, we could well be the only advanced civilization in the Milky Way.-***-"Eugene Koonin has shown that the probability of merely attaining RNA replication and translation (a necessary requirement for even the simplest life) is less than 10^-1018. He concludes that it is highly unlikely to occur anywhere in the universe....My own work in bioinformatics supports Koonin's probabilistic conclusions that no life should be expected in this universe if it is a one-shot deal. For example, the probability of obtaining, in a single search, any one of 10^92 functional sequences for the Ribosomal S7 structural domain (necessary for translation from RNA to proteins) is roughly 10^-100.-"Seigel points out that in order to develop a technologically advanced civilization, three major steps must occur. First is the commencement of a simple life form, which requires evolving not just one, but a few hundred mutually specified proteins capable of combining together to form a living cell. For this to take place, the right proteins must fortuitously occur on the same planet, and at the same time and location on that planet. Then, life must survive long enough to evolve intelligence. The third step is to become technologically advanced. The likelihood of these three steps prompts Seigel to write, "the huge uncertainties make it a very real possibility that humans are the only spacefaring aliens our Universe has ever known."-***-"The first option is to grant Koonin's theory that we won a lottery against mind-staggering odds, requiring a near infinite number of unseen, untestable universes. The second option arises out of our observation that the universe and this particular planet seem to be incredibly fine-tuned to support life. It may be more rational, therefore, to conclude that there is, in fact, just one Creator who is greatly interested in Earth and its inhabitants. So the choice is between an infinite number of universes to explain our monstrous stroke of luck, or a Creator of the cosmos who has a purpose in mind for humanity. I suggest we go with Ockham's Razor and opt for the latter."-Comment: Since the multiverse is unprovable and a cop-out, I'll stick with Ockham and God. I've offered Koonin's odds before.