If life is normal... (Crossposted)

In message , Dennis
Taylor writes

"randyj" wrote in message
...

"Dennis Taylor" wrote in message
. ca...
--snip


Doesn't the moon also keep the earth's axis from wobbling around any more
than it does, such that if we didn't have the moon, there would be way
more
climate
variation than we now have?


I've heard that, although I've not seen a specific explanation of why that
should be so. I'm also a little suspicious, since Venus & Mars don't have a
large moon, and their axes aren't all that out of whack (same with Mercury,
as a matter of fact). It *is* possible that we just happen to be in a period
where all the inner planets have reasonable tilts, but I'd be more inclined
to question the reason for the theory in the first place, in the absence of
any observed evidence.

I think that Mars and Venus are part of the evidence for the theory
being correct! The axis of Mars is supposed to have varied between near
zero and fifty degrees, though I can't remember if this is just theory
or there is some evidence for it, and Venus can be thought of as "upside
down" - it's rotating very slowly "the wrong way" compared to the other
planets, so its inclination is usually expressed as 177 degrees, not 3.
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk

In message , Dennis
Taylor writes

"randyj" wrote in message
...

"Dennis Taylor" wrote in message
. ca...
--snip


Doesn't the moon also keep the earth's axis from wobbling around any more
than it does, such that if we didn't have the moon, there would be way
more
climate
variation than we now have?


I've heard that, although I've not seen a specific explanation of why that
should be so. I'm also a little suspicious, since Venus & Mars don't have a
large moon, and their axes aren't all that out of whack (same with Mercury,
as a matter of fact). It *is* possible that we just happen to be in a period
where all the inner planets have reasonable tilts, but I'd be more inclined
to question the reason for the theory in the first place, in the absence of
any observed evidence.

I think that Mars and Venus are part of the evidence for the theory
being correct! The axis of Mars is supposed to have varied between near
zero and fifty degrees, though I can't remember if this is just theory
or there is some evidence for it, and Venus can be thought of as "upside
down" - it's rotating very slowly "the wrong way" compared to the other
planets, so its inclination is usually expressed as 177 degrees, not 3.
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk

"Jonathan Silverlight" wrote in message
...
I think that Mars and Venus are part of the evidence for the theory
being correct! The axis of Mars is supposed to have varied between near
zero and fifty degrees, though I can't remember if this is just theory
or there is some evidence for it, and Venus can be thought of as "upside
down" - it's rotating very slowly "the wrong way" compared to the other
planets, so its inclination is usually expressed as 177 degrees, not 3.

If I remember right (and my astronomy days are way behind me), Venus' "day"
is very long, damn close to its year. In that case, it would be more likely
that Venus is becoming tidally locked, and is "rocking" back and forth prior
to settling in with one face permanently to the sun, and less likely that it
"flipped" by almost 180 degrees.

As to Mars, well, geologists have tracked Earth's historical magnetic pole
movements by examining volcanic rock. All I've ever seen stated about the
polar axis is a precession with a period of 23,600 years or thereabouts.
Seems unlikely that they'd know more about Martian axis movements that
Earth's. I'd kind of like to know how they back up their estimates of that
Martian variation-- as far as I know, we haven't planted a geologist on Mars
yet (would that be an Areologist?)

"Jonathan Silverlight" wrote in message
...
I think that Mars and Venus are part of the evidence for the theory
being correct! The axis of Mars is supposed to have varied between near
zero and fifty degrees, though I can't remember if this is just theory
or there is some evidence for it, and Venus can be thought of as "upside
down" - it's rotating very slowly "the wrong way" compared to the other
planets, so its inclination is usually expressed as 177 degrees, not 3.

If I remember right (and my astronomy days are way behind me), Venus' "day"
is very long, damn close to its year. In that case, it would be more likely
that Venus is becoming tidally locked, and is "rocking" back and forth prior
to settling in with one face permanently to the sun, and less likely that it
"flipped" by almost 180 degrees.

As to Mars, well, geologists have tracked Earth's historical magnetic pole
movements by examining volcanic rock. All I've ever seen stated about the
polar axis is a precession with a period of 23,600 years or thereabouts.
Seems unlikely that they'd know more about Martian axis movements that
Earth's. I'd kind of like to know how they back up their estimates of that
Martian variation-- as far as I know, we haven't planted a geologist on Mars
yet (would that be an Areologist?)

Your thesis pales in the face of real world Urban Renewal. When you are thrown
into the wilderness by Urban Renewal to start over
with whatever you have squirreled away that some politician,
developer, realtor, insurance agent, etal hasnt stolen then cast your gaze among
the stars to inquire about the meaning of life in general.

You must be among the .1% exempt class ! Thanks for telling
us the meaning of life.

-Jerry



Robert Casey wrote:

John Leonard wrote:

It occurred to me the other evening, that the universe is supposed to be
~14 billion years old. Life on Earth is supposed to be ~3.5 billion years
old. Human life is 1 million years.

At one time, people thought that they, and the Earth, were at the center
of the universe. However that perception changed to one in which the Sun is
the center of the Universe. And from there, the Sun became the center of the
Solar System, which became another part of the Milky Way, which became
another part of the known Universe. Instead of being at the center of
everything, we were in the middle of nowhere and were simply average.

A common conception of evolution put us at the head of the list of
species ('Created in the image of God'). As if the object of evolution is to
produce us and our kind. Now this is known to be false. We are just another
species competing for ground on this here green earth.

And as a species we are overwhelmingly successful at that. But we look
to be the first species
to give some thought about the environment and think about how to
properly manage this
planet. The first species to construct a technological based
civilization, including an internet.
Now, this planet is around 4.5 billion years old, and simple life
happened, what, about 3.8
billion years ago. Okay, but it took another 3.2 billion years before
multicellular life forms to
show up. and maybe in another 50 to 100 million years to evolve the
first 100 kilogram
animals. Animals big enough to support human sized brains. But it
still took half a
billion years to evolve humans (which have big brains AND hands with
thumbs).
Dolphins have fairly big brains, but they can't do much except swim and
eat fish.
(Besides IIRC dolphins' brains have a large portion dedicated to sonar
decoding,
which of course decreases the amount for "intelligence"). Humans have
pretty
much standard issue senses of the animal world; housecats have binocular
vision
and their brains are way smaller than ours. Same for hearing and smell and
taste and touch. These things thus can't take that much overhead to
operate, if smaller animals have them.
So we have a lot of brain left over for "intelligence". Without which
we'd be lion food in the fields of Africa. So far we haven't found any
fossil evidence
of any previous species that built any civilizations on this planet.
With all the
trash we have thrown out around here subsequent civilization species
should have
no trouble knowing we existed.... But my point is that with all the
millions of
species of larger animals that have evolved and went extinct, it still
took half a
billion years for us to happen. And we didn't "invent" hands,
Trontosaurs(sp) Rex
had what looks like hands on those little arms they had. Maybe if that
asteroid
didn't happen, maybe they would have evolved bigger brains and Godzilla
would
have created the first civilization :-).

Now if we find some real single celled life on Mars and or Europa, then
we'd know that
life is easy to start. But if it took Earth 3.2 billion years to
generate multicelluar life,
then that seems to imply that that step is difficult. And thus rare.
And compound on
top of that the seeming fact that it took a long time to generate
creatures with big
brains and hands and thus a civilization, we could be the only guys in
town....
There are likely "earths" out there in this galaxy with something like
animals and
plants but no big brain and handed ones, and will never evolve such.

So there are billions of type "G" stars (the Sun is a type "G2V") around
in the galaxy,
and we're finding large planets around a sizable fraction of them.
Many "solar"
systems have planets in elliptical orbits that preclude earths in
circular orbits. But a few
do have circular orbits far out enough to be like our Jupiter. And we
may have
needed Jupiter to act like a sink for most of the loose asteroids and
other junk that
would otherwise whack the Earth so often to destroy life here. Also it
might have
helped that Earth had a sizable mini-planet around (the Moon) to make
tides to
slosh the oceans around to get land life going. Getting a usable Earth
after having
a Mars sized planet hitting it is likely to be a longshot anyway. You'd
more
likely get rocks like Mercury, Venus or Mars or the Moon.....

So it may be that we have three events that are longshots here. First
one is
getting an Earth with a Moon, then the second is getting multicelluar
life, and the
third is evolving creatures with big brains and hands. Now if I
remember that
probability class in college right, and if the odds of these events
happening
are around 1 in 10 million each, then all three happening is A*B*C= 1 in
10^21
or so. Now that's the odds of a G type star ever having a civilization
happening
in its system in its lifetime (around 10 billion years). We're here
now, but who
knows how long we'll last.... If we assume that we could not have happened
in the sun's first 4 billion years of its life, that still leaves 6
billion years before
red giant stage. Our civilization's been around for about ten thousand
years.
That's not exactly a large fraction of 6 billion years. Call it 1 out
of a million.
Cascade that to the 1 out of 10^21 odds from above, and you'd get
1 out of 10^27 odds of picking out a G class star and finding a
civilization
there. That could explain why ET hasn't shown up and why the Klingons
aren't attacking..... We might have to go to another galaxy before
we find
someone.


It seems that one of the results of Scientific progress is to disabuse
us of an infantile concept of ourselves as being the center of everything
and replace it with another conception in which we are merely average.

If my ramblings above even vaguely resemble reality, then we are
actually far from
average......


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) averages that it could be much greater than
our own?



Well, the universe is a really big place, with billions of galaxies each
with hundreds of billions of
stars (and billions of G type stars), so it is quite likely that someone
is in fact out there. It might
be that the average distance between civilizations is around a million
light years, so we're not
likely to stumble across each other soon. If the average galaxy has a
billion G stars, and
the odds of a G star having a civilization is the above 1 out of 10^27,
you'd likely need
10^18 galaxies for even money on finding a civilization. That seems a
bit high.....

There's another angle to consider: We may actually develop Star trek
star travel, or even if that
can't be done, and it takes thousands of years to travel to close by
stars, we could spread out
like a virus thru the galaxy in a few million years. And the galaxy is,
what, 10 billion years old,
so someone else a few tens of millions of years ahead of us should have
shown up by now.
And populated the Earth thus taking it over, and we wouldn't be here
dominating the
planet.

What we Know: It took around 3 billion years to get multicelluar life
here, and another
half billion years for humans to show up. And a reasonable estimate of
how many
species of larger animals evolved in that half billion years. Well,
maybe ten million
is too high, maybe a hundred thousand is closer. And that stars with
Jupiters are
not hard to find around here. We don't know how hard it is to make an
Earth
with oceans, and if a Moon is really required to get life onto land. Or
the odds
of having an Earth with a Moon after a planetary collision. Computer
simulations
should give a rough idea here. You'd probably get a lot of Venuses and
Mercuries.
Still with my correction, we'd still need 10^16 galaxies. I got better
odds of
hitting the megaball lottery........

Your thesis pales in the face of real world Urban Renewal. When you are thrown
into the wilderness by Urban Renewal to start over
with whatever you have squirreled away that some politician,
developer, realtor, insurance agent, etal hasnt stolen then cast your gaze among
the stars to inquire about the meaning of life in general.

You must be among the .1% exempt class ! Thanks for telling
us the meaning of life.

-Jerry



Robert Casey wrote:

John Leonard wrote:

It occurred to me the other evening, that the universe is supposed to be
~14 billion years old. Life on Earth is supposed to be ~3.5 billion years
old. Human life is 1 million years.

At one time, people thought that they, and the Earth, were at the center
of the universe. However that perception changed to one in which the Sun is
the center of the Universe. And from there, the Sun became the center of the
Solar System, which became another part of the Milky Way, which became
another part of the known Universe. Instead of being at the center of
everything, we were in the middle of nowhere and were simply average.

A common conception of evolution put us at the head of the list of
species ('Created in the image of God'). As if the object of evolution is to
produce us and our kind. Now this is known to be false. We are just another
species competing for ground on this here green earth.

And as a species we are overwhelmingly successful at that. But we look
to be the first species
to give some thought about the environment and think about how to
properly manage this
planet. The first species to construct a technological based
civilization, including an internet.
Now, this planet is around 4.5 billion years old, and simple life
happened, what, about 3.8
billion years ago. Okay, but it took another 3.2 billion years before
multicellular life forms to
show up. and maybe in another 50 to 100 million years to evolve the
first 100 kilogram
animals. Animals big enough to support human sized brains. But it
still took half a
billion years to evolve humans (which have big brains AND hands with
thumbs).
Dolphins have fairly big brains, but they can't do much except swim and
eat fish.
(Besides IIRC dolphins' brains have a large portion dedicated to sonar
decoding,
which of course decreases the amount for "intelligence"). Humans have
pretty
much standard issue senses of the animal world; housecats have binocular
vision
and their brains are way smaller than ours. Same for hearing and smell and
taste and touch. These things thus can't take that much overhead to
operate, if smaller animals have them.
So we have a lot of brain left over for "intelligence". Without which
we'd be lion food in the fields of Africa. So far we haven't found any
fossil evidence
of any previous species that built any civilizations on this planet.
With all the
trash we have thrown out around here subsequent civilization species
should have
no trouble knowing we existed.... But my point is that with all the
millions of
species of larger animals that have evolved and went extinct, it still
took half a
billion years for us to happen. And we didn't "invent" hands,
Trontosaurs(sp) Rex
had what looks like hands on those little arms they had. Maybe if that
asteroid
didn't happen, maybe they would have evolved bigger brains and Godzilla
would
have created the first civilization :-).

Now if we find some real single celled life on Mars and or Europa, then
we'd know that
life is easy to start. But if it took Earth 3.2 billion years to
generate multicelluar life,
then that seems to imply that that step is difficult. And thus rare.
And compound on
top of that the seeming fact that it took a long time to generate
creatures with big
brains and hands and thus a civilization, we could be the only guys in
town....
There are likely "earths" out there in this galaxy with something like
animals and
plants but no big brain and handed ones, and will never evolve such.

So there are billions of type "G" stars (the Sun is a type "G2V") around
in the galaxy,
and we're finding large planets around a sizable fraction of them.
Many "solar"
systems have planets in elliptical orbits that preclude earths in
circular orbits. But a few
do have circular orbits far out enough to be like our Jupiter. And we
may have
needed Jupiter to act like a sink for most of the loose asteroids and
other junk that
would otherwise whack the Earth so often to destroy life here. Also it
might have
helped that Earth had a sizable mini-planet around (the Moon) to make
tides to
slosh the oceans around to get land life going. Getting a usable Earth
after having
a Mars sized planet hitting it is likely to be a longshot anyway. You'd
more
likely get rocks like Mercury, Venus or Mars or the Moon.....

So it may be that we have three events that are longshots here. First
one is
getting an Earth with a Moon, then the second is getting multicelluar
life, and the
third is evolving creatures with big brains and hands. Now if I
remember that
probability class in college right, and if the odds of these events
happening
are around 1 in 10 million each, then all three happening is A*B*C= 1 in
10^21
or so. Now that's the odds of a G type star ever having a civilization
happening
in its system in its lifetime (around 10 billion years). We're here
now, but who
knows how long we'll last.... If we assume that we could not have happened
in the sun's first 4 billion years of its life, that still leaves 6
billion years before
red giant stage. Our civilization's been around for about ten thousand
years.
That's not exactly a large fraction of 6 billion years. Call it 1 out
of a million.
Cascade that to the 1 out of 10^21 odds from above, and you'd get
1 out of 10^27 odds of picking out a G class star and finding a
civilization
there. That could explain why ET hasn't shown up and why the Klingons
aren't attacking..... We might have to go to another galaxy before
we find
someone.


It seems that one of the results of Scientific progress is to disabuse
us of an infantile concept of ourselves as being the center of everything
and replace it with another conception in which we are merely average.

If my ramblings above even vaguely resemble reality, then we are
actually far from
average......


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) averages that it could be much greater than
our own?



Well, the universe is a really big place, with billions of galaxies each
with hundreds of billions of
stars (and billions of G type stars), so it is quite likely that someone
is in fact out there. It might
be that the average distance between civilizations is around a million
light years, so we're not
likely to stumble across each other soon. If the average galaxy has a
billion G stars, and
the odds of a G star having a civilization is the above 1 out of 10^27,
you'd likely need
10^18 galaxies for even money on finding a civilization. That seems a
bit high.....

There's another angle to consider: We may actually develop Star trek
star travel, or even if that
can't be done, and it takes thousands of years to travel to close by
stars, we could spread out
like a virus thru the galaxy in a few million years. And the galaxy is,
what, 10 billion years old,
so someone else a few tens of millions of years ahead of us should have
shown up by now.
And populated the Earth thus taking it over, and we wouldn't be here
dominating the
planet.

What we Know: It took around 3 billion years to get multicelluar life
here, and another
half billion years for humans to show up. And a reasonable estimate of
how many
species of larger animals evolved in that half billion years. Well,
maybe ten million
is too high, maybe a hundred thousand is closer. And that stars with
Jupiters are
not hard to find around here. We don't know how hard it is to make an
Earth
with oceans, and if a Moon is really required to get life onto land. Or
the odds
of having an Earth with a Moon after a planetary collision. Computer
simulations
should give a rough idea here. You'd probably get a lot of Venuses and
Mercuries.
Still with my correction, we'd still need 10^16 galaxies. I got better
odds of
hitting the megaball lottery........

"r" == randyj writes:

r "Dennis Taylor" wrote in message
r . ca...
I'm just throwing this out for the sake of argument, but here goes:
[...]
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.

r Doesn't the moon also keep the earth's axis from wobbling around
r any more than it does, such that if we didn't have the moon, there
r would be way more climate variation than we now have?

I had to track this claim down recently for a proposal. As far as I
can tell, Laskar & Robutel (1993, "The Chaotic Obliquity of the
Planets," Nature, 361, 608) were among the first, if not the first, to
make this claim.

While it is true that the Moon stabilizes the Earth's rotational axis,
I'm not sure that we can draw any grand conclusions from this fact.
Would life have arisen anyway? If life arose at the bottom of the
ocean, near a ocean-floor vent, I have difficulty understanding why
the climate on the surface would have affected what was happening 5 km
below the ocean's surface.

Once it arose, would life have survived had the Moon not existed? I
think we know the answer to this question. There have been serious
suggestions of a "snowball Earth," in which much, if not all, of the
Earth's surface was frozen. Thus, the Moon's effect in stablizing the
climate could not have been that important, at least for single-celled
life.

Would multi-cellular or terrestrial life have arisen without the Moon?
Again, I don't think we can answer this question.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

"r" == randyj writes:

r "Dennis Taylor" wrote in message
r . ca...
I'm just throwing this out for the sake of argument, but here goes:
[...]
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.

r Doesn't the moon also keep the earth's axis from wobbling around
r any more than it does, such that if we didn't have the moon, there
r would be way more climate variation than we now have?

I had to track this claim down recently for a proposal. As far as I
can tell, Laskar & Robutel (1993, "The Chaotic Obliquity of the
Planets," Nature, 361, 608) were among the first, if not the first, to
make this claim.

While it is true that the Moon stabilizes the Earth's rotational axis,
I'm not sure that we can draw any grand conclusions from this fact.
Would life have arisen anyway? If life arose at the bottom of the
ocean, near a ocean-floor vent, I have difficulty understanding why
the climate on the surface would have affected what was happening 5 km
below the ocean's surface.

Once it arose, would life have survived had the Moon not existed? I
think we know the answer to this question. There have been serious
suggestions of a "snowball Earth," in which much, if not all, of the
Earth's surface was frozen. Thus, the Moon's effect in stablizing the
climate could not have been that important, at least for single-celled
life.

Would multi-cellular or terrestrial life have arisen without the Moon?
Again, I don't think we can answer this question.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

"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

"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