On Aug 13, 6:12 pm, "K_h" <KHol...@SX729.com> wrote:

Fermi's paradox suggests that there are little or no other intelligent
civilizations within the Milky Way galaxy.  On the other hand, intelligent
life should exist on a substantial fraction of planets with life because
natural selection broadly increases intelligence with time.  Here on the
Earth, for example, numerous mammals have a high degree of intelligence and
many of them could reach human intelligence with a few more million years of
evolution.

This contradiction can be resolved if the origin of life is far harder than
commonly believed.  That is, in the Drake equation, f_L should be far
smaller than most people think it is.  Even on planets that are life
friendly the formation of life should be extremely rare for the below
reasons.

For life to start, a molecule must arise that can make approximate copies of
itself.  Once that happens then natural selection can work its magic.  But a
molecule that can make approximate copies of itself must be a fairly
sophisticated nano-machine being comprised of dozens, if not hundreds, of
molecules and it must arise via inorganic and non-evolutionary processes.

From the study of DNA and genes, it is known that all life on the Earth has
a common origin (undoubtedly from a molecule of the aforementioned kind).
Since Earth is a life friendly planet, why hasn't another molecule (of the
aforementioned kind) arisen?  If it had, then life on the Earth would have
organisms with two different molecules for genetic codes: DNA and something
else.

Since all Earthly life is based on DNA, this suggests that, over the four
billion years of life on Earth, this has never happened again.  That is,
over the last four billion years, no other molecule has arisen by inorganic
and non-evolutionary processes that can make approximate copies of itself.
And Earth is a life-friendly planet so chances are optimal that such a
molecule should arise.

This suggests that the formation of such a molecule is a very rare event.
In other words, the reaction rate of inorganic chemistry per square meter
times the surface area of the Earth, times the average depth such reactions
take place, times four billion years is <<, much less, than the number of
such reactions needed before an approximately self reproducing molecule
arises by chance.

If that first molecule had not arisen here on the Earth then the Earth would
probably have been lifeless ever since.  This same reasoning applies if life
first started somewhere else in the solar system and then migrated to Earth
(for example from Mars).  If life rose independently on Mars once, over the
past four billion years, then that suggests that the reaction rate of
inorganic chemistry per square meter, times the surface area of a Mars sized
world, times the average depth such reactions take place, times four billion
years is about the number needed so that an approximately self reproducing
molecule arises by chance once, ~ 1.

It seems too much of a coincidence that the laws of chemistry work out in
such a way that life arises, on average, once per terrestrial world per
several billion years.  Rather, for such cases, it seems much more likely
that life arises multiple times or almost never.  The latter possibility
makes sense from a combinatorial perspective.  A self reproducing molecule
will be composed of dozens to hundreds of other molecules.  But the total
number of permutations for such a molecule's components will far exceed the
total number of inorganic chemical interactions that take place per
terrestrial world per several billion years.

A simple combinatorial thought experiment explains why.  The number of ways
of stacking a deck of playing cards is so huge that if 67.8 billion solar
masses were converted entirely into protons then each proton stands for a
different way of stacking the deck.  But there are 92 naturally occurring
chemical elements and a self reproducing molecule will probably be composed
of hundreds of atoms from the set of 92 different kinds (there only 52 cards
in a playing deck).

So, in the Drake equation, f_L could be something really small like 10^-90.
In this case the fact that life exists on the Earth simply shows that the
universe is super huge and its true size far exceeds the visible universe.

General relativity says that the universe sits on top of an infinite amount
of gravitational potential energy.  During both cosmic inflation and dark
energy inflation the universe falls down its own gravity well converting
huge quantities of its gravitational potential energy into vacuum energy and
expansion energy.  This probably explains why the universe is so huge.

So the universe could contain 10^150 planets, for example.  If f_L is 10^-90
then the total number of planets in the universe that have life is around
10^60.  So there are a lot of planets with life out there but none of them
are close by.  So this is one possible explanation for why there is only one
example of life in the solar system.  And this explanation is consistent
with Fermi's paradox.  It also suggests that any other life in our solar
system got there via migration.

In light of all this, it cannot be concluded that water, oxygen, and
methane, for example, are indicators of extraterrestrial life.  The presence
of these simple gases in the atmospheres of other planets can easily be
explained by inorganic processes.

If Earth is the only planet in 10^150 with life then that suggests that the
universe is fine tuned for Earthly life.  If a substantial fraction of the
10^150 planets have life then that suggests the whole universe is finely
tuned for life.  If the universe if not fine-tuned for life then that
suggests the number of planets with life should be around the logarithmic
middle of 10^150 or around 10^75.

In conclusion, it seems there are lots of planets with life out there but
none of them will ever communicate with humans.

Such arguments are based on using life on earth as a model, but
are also loaded with incorrect notions. First of all, there is no
"doctrine of progress" in evolution. Who says that intelligence is
sellected for? The most successful organisms on the earth are
the dumbest---bacteria---at least "dumbest by our standards".
Of all the human societies that have existed over the past 10,000
years, only one became oriented in the direction of intersteller
communication. We are new on the scene. There is no guarantee
that our culture will retain its high tech ways.

Take, for example, the Olduvai  Theory:
http://dieoff.org/page125.htm

which basically is Richard Dunkin's theory
stating  that over the long haul, our
high-population, high-resource demanding culture will
collapse leaving a low population, low resource demanding
stone age culture.

This notion follows other biological growth scenarios that are
governed by the logistic equation.  So, it may be that there
are some flash-in-the-pan high tech worlds out there, that last
a time measured in decades or centuries, and quickly drop
back to that more efficient totally renewable low tech stone age
culture that they sprang from. The Universe could be jam-packed
with human scale intelligent life forms, that are happly chipping
flint into arrowheads and burning wood fires.

Or, it could be worse. The universe could be filled with ecologically
spent "Easter Islands", where there are only ruins, and not even
wood to burn.

k

-John