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Eben Rose

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How can we surmise that chemical evolution may lead to Earth-referenced attributes of life as if it is a universal law?

Our experience with life and intelligence is wholly Earth-referenced, yet SETI and the discipline of astrobiology assert that life-as-we-know-it is unquestionably "out there". Why? Is it a reasonable assumption that chemical evolution inevitably leads to "us-like" properties wherever conditions are "just right'? How restrictive is the notion of "just right" conditions? Wouldn't such conditions need to be EXACTLY like Earth's historical conditions in order to arrive at Earthlike outcomes?

Taken at the level of molecular organization and building up from there, the probabilities of generating a bacterium, even given Earthlike initial conditions of, say, 4 billion years ago, are beyond astronomical. A probability distribution is associated with each stage of synthesis along the evolutionary path, and these are affected, too, by ever changing and largely unpredictable externalities, such as irradiation and impacts. The outcome of these probabilities then provide the prior conditions that affect the shape of the next probability distribution. All of these compounded probabilities have been integrated over geological timescales to arrive at Earth's version of life. How could recognizably similar outcomes be extrapolated to the integrated histories of chemical synthesis taking place on other worlds?

Indeed there are huge numbers of stars and galaxies in the vast universe, and we have all been lured by the numbers game that turns the even the minutest probability into an inevitability. But we should always temper our searches for ET to that vastly smaller part of the universe that is in any way accessible to us from our own spacetime well. At some scope of distance, the search for ET crosses the boundary into cosmology with contact across times and parallel universes that are not part of the ET search.

SETI and astrobiology proffer deterministic metaphysics of inevitable life within our accessible universe as if it is science. Is it science or just wishful thinking?


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  • Van Le

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    Jun 9 2012: well the fact is the universe has been around longer than planets like the earth. Given the universe is 10billion years older than the earth, i am sure it would have somewhere spawned planets like earth billions of years before this planet even existed. Given the low probability of protein forming, well, its happened once in 1 billion years (time it took for first simple cells to form) in earth conditions, so we know it must have occured at least a few more times in 10 billion years before the earth has even existed. Given the number of earth like planets out there each Billion years there is a chance of prokaryotes forming. If it did happen and then that civilization is billions of years more advanced than us, they probably have control over space and time, i doubt they would have any interest in a noob civilisation like ours. Instead they would probably be not wanting to wait a billion years for an evolutionary event to take place, instead they might just be dumping cells here and there and watching the result or having their machines do it. So if this is happenening theres alot more life out there :) rather than aliens just leaving it to chance. :)) So cmon, if you were the most advanced civilisation in the universe, what else would you be doing? Playing God of course :)
    • P C

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      Jun 10 2012: I think it's safe to say that all life forms in the universe evolved on aat least 2nd generation stars. This will naturally push forward the initial stages of life to a point far enough that a 1st generation star would have needed to go through all stages of stellar evolution.

      Life on Earth was nearly wiped out 2 or 3 times, which delayed our development but also diversified life.
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      Jun 10 2012: Our Earth history produced Julius Caesar, but we would not so easily accept that, given "Earthlike conditions", other worlds in the universe would, with any probability, produce Caesar. This is not how history works. History is not rule-governed in any way but in that which can predict the most general of outcomes.

      Prokaryotes are highly derived levels of organization that cannot be predicted from polypeptides or from properly folded proteins. Or can they? Somewhere between the easily dismissible expectation that Caesar would appear at least one other time in the vast population of "Earthlike" planets in the universe, and the expectation of prokaryotes emerging on another world from prebiotic precursors, just as it did on Earth, lies the intersection between deterministic processes that give SETI its modus operandi and stochastic processes that mark one-of-a-kind historical trajectories. Where is this boundary?

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