"Dennis Taylor" wrote in message
. ca...
I'm just throwing this out for the sake of argument, but here goes: 1)
It's
generally accepted that Venus and Mars have no plate tectonics, while
Earth

Actually Venus shows evidence of plate tetonics because of the volcanic
activity observed ...

does. You can maybe excuse Mars because of its size, but not Venus. 2) Any
number of books have made reference to the importance of plate tectonics
in
the creation and maintenance of the Earth's biosphere, because of
outgassing, recycling of deposited carbon materials, etc. 3) The biggest
difference betwen Earth and the other two is the presence of the moon,
which
also is probably a major reason for the continued existance of an active
and
molten core, due to heating from tidal action.

So, given this, what if one of the primary requirements for life, for a
long
enough period to allow evolution of intelligence, is the presence of a
satellite big enough or close enough to maintain a molten core and ongoing
tectonics? That would certainly reduce the probability of life in the
universe, without requiring a mystical explanation.

Your're not correct about the Moon being responsible for Earths molten core
(Joseph Lazio commented on this too)--- it does cause tides but Earth's
molten core is due to radioactivity. Venus also has a molten core by the
way, volcanic activity, and plenty of outgasing too ...

Now think of Jupiters satellites, Io, Europa, Callisto, & Ganymede ... Io is
the most volcanic place in the Solar System (due to tidal flexing from
Jupiter and the other satellites (primarily)) --- lots of mixing and
outgassing going on there --- Europa too, a frozen surface, but perhaps with
a warm liquid water interior ... same for Callisto and Ganymede ...

I don't think you're arguments can be generalized as making a case for a
requirement for life ... too many factors at play ... on Earth though the
right factors came together ... how rare is that? ... no one really knows
for sure now ... but I "estimate" we'll find plenty of Earth like planets
in the future ... with life too no doubt ...
Al


This argument is covered in "Where Is Everybody" by Stephen Webb, and I
find
it particularly convincing. It's certainly something that would get around
the principle of Mediocrity.


"Steve" wrote in message
...
John Leonard allegedly said:

If this interpretation is correct then given the age of the
Universe
and
the variation about an average (say, our Earth's age) that would be
expected (this is essentially a guess), what possibilities might exist
regarding life in our Universe? In other words if we were to assume
that
we are not unique what might be the actual age of life? Is it
reasonable
to guess, merely on the basis of our (supposed) averageness that it
could
be much greater than our own?

John Leonard

There could be races out there several billion years ahead of us.

They probably exist as pure energy and pass right through us at the
speed
of
light on their way to wherever......and we don't even know it...and we
appear to them as dull, stupid beasts barely out of the slime.

Read your newspaper.

It's obvious there is no intelligent life on Earth.

We flatter ourselves - vain monkies that we are.

--
Steve