[ExI] Drake Equation Musings

[BillK]

On 18 May 2016 at 09:58, Anders Sandberg  wrote:
> I am not using a rare earth argument. Maybe I was oversimplifying my
> explanation of the Carter argument ( https://www.jstor.org/stable/37419 ):
> it allows for life being super-easy too. Extremophiles does not prove life
> is everywhere, since they merely show that once you have life, then it can
> spread into available niches.
>
> Think of it like this: what evidence would present itself to you in a
> universe where life was very easy, or one where it was very rare? In both
> cases you would see a planet with a biosphere compatible with you. You would
> find life adapted to a broad range of conditions. You would see life showing
> up early (either because it was simply likely, or because observers require
> a few rare steps). None of these observations give you any information
> allowing you to choose between the two universes.
>
> Now, if you had evidence that there wasn't lots of aliens around, that would
> favor the later conclusion - as well as the "life is easy, intelligence
> hard" and "intelligence doesn't last" conclusions (plus "weird" things like
> the zoo hypothesis). It weakens the "life is easy" conclusion a bit, but
> since the uncertainty of intelligence and future longevity parameters are
> big enough to soften the change in probabilities.
>

So you are agreeing with Carter's Weak Anthropic Principle that the
universe's apparent fine tuning is the result of selection bias: i.e.
only in a universe capable of eventually supporting life will there be
living beings capable of observing and reflecting upon fine tuning.
And this selection bias provides no information about the likelihood
of life elsewhere in the universe.
This view is compatible with the Rare Earth hypothesis which argues
that the combination of circumstances for life like us to evolve is
most unlikely and an extremely rare event.

This view is logically sound until we find actual evidence, firstly of
how widespread simple life is in the universe and secondly, how
frequently intelligent life has evolved from simple beginnings.

However, until such evidence appears, speculation continues on the
Strong Anthropic Principle that the fundamental physical parameters of
this universe are finely-tuned to allow (force?) life to evolve. This
is my preference. If life happened here, why not everywhere? To me,
the evidence that science is accumulating points in this direction.
Our universe appears to be the same as far out as our systems can
analyse. The universe is enormous and has been evolving for 13 billion
years.
"World enough and time".

BillK