On Saturday, February 3, 2018 at 6:03:33 PM UTC-7, John Clark wrote:
> On Sat, Feb 3, 2018 at 5:43 PM, Lawrence Crowell <goldenfield...@gmail.com 
> <javascript:>> wrote:
>> ​>​
>> 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.
> The fact that it took 2 billion years for Prokaryotes to evolve 
> into Eukaryotas gives some support that your suspicion may be correct. And 
> even after complex animals have evolved on a planet that doesn't mean it 
> has a civilization. Richard Dawkins notes that flight evolved 
> independently 4 times and the eye at least 40 times and perhaps as many as 
> 60, but intelligence, defined as the ability to make something as complex 
> as a radio telescope, evolved only once, and in the nearly 4 billion year 
> history of life that ability has only existed on this planet for about a 
> century. And yet when we use our telescopes to listen for sounds of 
> intelligence in the cosmos we hear only an eerie silence. Why? 

*Because any distinguishable intelligible signal is attenuated to noise 
when it traverses a few light years in distance. IIRC, LC once posted a 
limit of 10 light years is sufficient for dissipation.  If so, SETI is a 
waste of time and energy. AG*

> As Enrico Fermi famously asked, where is everybody?   ​
> ​
> Maybe we're the first, after all somebody has to be, or maybe some 
> catastrophe always happens to a civilization whenever it gets much beyond 
> the point we're at now. 
>   ​John K Clark​

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