On 2/3/2018 2:43 PM, Lawrence Crowell wrote:
It is interesting in some ways. However, it involves speculations on things we have no knowledge of.

The idea involves these filters. The one "behind us" involves the barrier to intelligent life similar to us. There are few examples of brainy animals similar to us. Cetaceans have large brains and clearly their songs contain complex information important to them. It is not clear that this is equivalent to complex thought such as mathematics. The other filter involves post-ET development where such life is limited by either self-extermination or the limits of light speed and the unapproachable scale of putative interstellar flight.

I suspect planets with complex life above that of prokaryotic-like life are few in number per galaxy. It is hard to know how even prokaryotic-like life starts.

There's a very good semi-popular book on the subject, "The Vital Question" by Nick Lane.  There's also a very good Youtube of him addressing the Royal Society.  He takes a "metabolism first" approach, which he thinks is mandated by the ubiquity of the ADP/ATP cycle in bacteria, archea, and eukaryotes.

Brent

The ribosome is a complex of RNA with polypeptides, and this thing is fairly universal. As yet we are not sure how this came about. So it could be that the life bearing planets are already extremely rare. This would make planets with complex life most likely very rare, and then up the ladder the occurrence of intelligent life exceedingly rare.

The occurrence of life might be a case of what is called hard emergence. Soft emergence is something like the emergence of chemistry from the quantum mechanics of atoms. Strong emergence is the occurrence of entirely different principles, where this is not an established scientific concept. This is of course a completely unknown territory. How life emerged is one of the great scientific questions.

LC

On Saturday, February 3, 2018 at 11:21:00 AM UTC-6, John Clark wrote:

    https://www.youtube.com/watch?v=UjtOGPJ0URM
    <https://www.youtube.com/watch?v=UjtOGPJ0URM>


     John K Clark

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