On Monday, May 23, 2022 at 7:22:47 AM UTC-5 johnk...@gmail.com wrote:
> On Sun, May 22, 2022 at 7:18 PM Lawrence Crowell <goldenfield...@gmail.com>
> wrote:
>
> >*I suspect there may only be a few thousand planets with complex life in
>> any galaxy. I would then say that given life has been here in complex form
>> for 600 million years and that Homo sapiens have been here 100,000 years
>> this means at any given time using this as a guide each planet with
>> complex life has a 1.7x10^{-4} probability of having intelligent life. This
>> is even smaller when one considers how long we have had advanced
>> technology, or about 3x10^{-7}. So this might mean that at any given time a
>> galaxy might have 1/1000 chance of having ETI. Maybe then on the Hubble
>> frame, or on our past light cone, there is on average an ETI on every 1000
>> galaxies.*
>
>
> *The trouble is it's extremely difficult to obtain useful statistics if
> you only have one example. On Earth life occurred almost as soon as liquid
> water could exist on its surface, but does that mean life is inherently
> easy to make? Maybe not because the only example we have is a planet in
> which not only life developed but intelligent life did, so life had to have
> started quickly here, perhaps freakishly quickly, because if it had taken
> much longer the sun would be turning into a red giant about the time
> intelligent creatures started building a civilization, and that would make
> any sort of life on the planet impossible. And even after life started all
> you had was simple Prokaryotic cells, it took another 2 billion years for
> far more complex Eukaryotic cells to evolve, and then another 1.5 billion
> years for multicellular life to evolve, and 500 million years after that to
> get a technological civilization which only happened a few thousand years
> ago. *
>
> *How typical is any of this? Nobody knows but we have hints; most major
> evolutionary developments, such as the invention of the eye and flight,
> evolved independently more than once, sometimes dozens of times but
> intelligence, defined as the ability to make a radio, occurred only
> once. But even when we look deep into space with enormous telescopes we
> don't see even the slightest hint of engineering. *
>
A galaxy dominated by von Neumann probes would like bare some signatures of
such. So far nothing is evident. Of course galaxies we observer are in the
past. We could just be one of the early IGUS or intelligent life forms on
the Hubble frame.
LC
>
>
>> *> Now consider there is probably some filter that selects out ETIs.
>> Either they annihilate themselves with nuclear explosive, or they collapse
>> the life support system of their planet or . , a range of things we may
>> do to ourselves that prevents them from ever developing a von Neumann
>> probe. *
>
>
> *The human race only needs to hang together for a few more decades before
> a von Neumann probe gets made, I don't think it's reasonable to expect that
> every single civilization without exception destroys itself just an instant
> before it has the ability to make such a thing, especially when you
> consider that if intelligence is as common as some claim then some of those
> civilizations must have started on planets where the element Uranium is
> much rarer in its surface crust than it is on the Earth. On Earth's surface
> Uranium is not particularly rare, it's far more common than Gold, but if it
> was as rare as Osmium, Rhodium or Iridium we'd have no nuclear weapons
> today and wouldn't have any in the future until asteroid mining became
> practical, and by then making a von Neumann probe would be practical too.*
>
> John K Clark See what's on my new list at Extropolis
> <https://groups.google.com/g/extropolis>
> swl
>
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to everything-list+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/8c336ffe-4f23-4c99-b16c-823e601da831n%40googlegroups.com.
