🚀 go-pugleaf

In article <1cl20hINNec3@gap.caltech.edu> palmer@cco.caltech.edu (David M. Palmer) writes:

>One way to estimate P(life | suitable planet), while adjusting for the
>weak local anthropic principal ("how strange that we should be on
>a planet which has life---NOT!" :-)) is to look at how long it took life to
>evolve, and compare that to the length of the 'window of opportunity'
...
>It turns out that life occurred just about as soon as the Earth was
>tolerable, like within 100 million years (this number is approximate, I
...
>accreted.)  This is very near the start of the window, which is roughly
>5 billion years long as a rough number.


The last statement cannot be supported, since we don't know what
conditions are required for life to originate.  It could be that they
would exist only soon after the formation of a planet.  For example,
perhaps deposition of organic material from space is required.

Another thing one can do is to look at how long it took humans to
appear -- about 4.5 billion years.  The earth will not be habitable
much longer (due to the increasing brightness of the sun with time),
perhaps as little as a few hundred million years.  The late appearance
of humanity is weak evidence that the evolution of intelligence, or,
indeed, multicellular life, takes a long time, perhaps much longer
than the average lifespan of a biosphere.

	Paul