Panspermia?

[David V. Loewe, Jr]

<http://www.technologyreview.com/blog/arxiv/27720/?p1=blogs>

Headline & Summary paragraph -

"The Amazing Trajectories of Life-Bearing Meteorites from Earth

The asteroid that killed the dinosaurs must have ejected billions of
tons of life-bearing rock into space. Now physicists have calculated
what must have happened to it."

And the mind-blowing part -

"But perhaps most surprising is the amount that makes its way across
interstellar space. Last year, we looked at calculations suggesting that
more Earth ejecta must end up in interstellar space than all the other
planets combined.

Hara and co go further and estimate how much ought to have made its way
to Gliese 581, a red dwarf some 20 light years from here that is thought
to have a super-Earth orbiting at the edge of the habitable zone.

They say about a thousand Earth-rocks from this event would have made
the trip, taking about a million years to reach their destination."
--
"It's raining soup and we haven't built any soup bowls."
Dr. Jerry Pournelle

[Martha Adams]

On 4/11/2012 7:46 PM, David V. Loewe, Jr wrote:
> <http://www.technologyreview.com/blog/arxiv/27720/?p1=blogs>
>
> Headline& Summary paragraph -

>
> "The Amazing Trajectories of Life-Bearing Meteorites from Earth
>
> The asteroid that killed the dinosaurs must have ejected billions of
> tons of life-bearing rock into space. Now physicists have calculated
> what must have happened to it."
>
> And the mind-blowing part -
>
> "But perhaps most surprising is the amount that makes its way across
> interstellar space. Last year, we looked at calculations suggesting that
> more Earth ejecta must end up in interstellar space than all the other
> planets combined.
>
> Hara and co go further and estimate how much ought to have made its way
> to Gliese 581, a red dwarf some 20 light years from here that is thought
> to have a super-Earth orbiting at the edge of the habitable zone.
>
> They say about a thousand Earth-rocks from this event would have made
> the trip, taking about a million years to reach their destination."

======================================
This is a really interesting idea and possibility. It could be so; but
if it is, I think it's a mistake to imagine we /our remote ancestors,
were there first. Our universe seems about 13.7 billion years old, and
I'm seeing cosmologists thinking about when might the first life-making
environments have appeared in our then young universe. And that was a
*long* time back from now. For which reason, if we think about our
Terra having seeded life out to other worlds, we seem to be actually
talking about a universe with life seeds all over the place; and if we
look at our own Terra, where were *we* seeded from? Mars? Or
elsewhere very much more remote in space and time?

Titeotwawki -- Martha Adams -- [Wed 2012 Apr 11]

===============================================
** Space Frontier Now! **
http://www.mhada.info
===============================================

[David Loewe, Jr.]

The article addresses that possibility.

"That raises another interesting question: how quickly could
life-bearing ejecta from Earth (or anywhere else) seed the entire
galaxy?

Hara and co calculate that it would take some 10^12 years for ejecta to
spread through a volume of space the size of the Milky Way. But since
our galaxy is only 10^10 years old, a single ejection event could not
have done the trick.

However, they say that if life evolved at 25 different sites in the
galaxy 10^10 years ago, then the combined ejecta from these places would
now fill the Milky Way.

There's an interesting corollary to this. If this scenario has indeed
taken place, Hara and co say: "then the probability is almost one that
our solar system is visited by the microorganisms that originated in
extra solar system."

Entertaining stuff!"
--
"The only universal message in science fiction: There exist minds that
think as well as you do, but differently."
- Laurence VanCott Niven

[Keith F. Lynch]

Martha Adams <mh...@verizon.net> wrote:
> David V. Loewe, Jr wrote:
>> Hara and co go further and estimate how much ought to have made its
>> way to Gliese 581, a red dwarf some 20 light years from here that
>> is thought to have a super-Earth orbiting at the edge of the
>> habitable zone.

That star's radial motion relative to us, according to Wikipedia,
is about 9.5 kilometers per second. That means that during the KT
impact it was about 2000 light years away, not 20.

Of course there were likely other solar systems within 20 light year
of us then, so I'll substitute one of them.

>> They say about a thousand Earth-rocks from this event would
>> have made the trip, taking about a million years to reach their
>> destination."

And passed through an average-sized solar system at that distance?
Plausible. And hit a planet in that solar system? Not plausible.
It's late, so I'll leave the math for another night. Or I'll leave
it as an exercise for the reader: If each Earth-sized area 20 light
years away intercepted a thousand rocks, how many rocks must there
have been in total? I know without calculating it that it would be
an absurdly large number.

Another problem is that unless the rock was immense and the life was
near its center, the life would have been fried by cosmic rays during
the million-year trip.

Panspermia within a single solar system might be possible, but between
solar systems it seems very, very unlikely.
--
Keith F. Lynch - http://keithlynch.net/
Please see http://keithlynch.net/email.html before emailing me.

[Martha Adams]

=====================================

> Entertaining stuff!"

Indeed. Concerning which, it raises a question. If as seems plausible,
our local galaxy is more or less filled with life-bearing planets; and,
if life-bearing planets eventually see evolution of intelligent life
forms and some of those develop technological and even space-going
beings, then, one would reasonably believe,

1)We'd find evidence in places like Luna and even here on Terra, that
*somebody was here and had a look around*; and

2) SETI would hear several to many other worlds radiating radio and
etc signals;

and maybe other other events relating to other lives and people out
there in this universe.

Yet, our best observation today finds nothing yet of that. Seems
to me, what we know of our (deadly) universe today, makes it in fact
as dead and sterile as our faith-based extremists would make it.

Titeotwawki -- Martha Adams [Thr 2012 Apr 12]

[Martha Adams]

======================================

My perception of Keith's thinking is, "Yes, but no." Because, both
are true. We are looking at very small but non zero probabilities
here. My thinking is that, "...but always, we will find surprises."
To answer this topic needs *more data*, and I think that next after
getting human settlements and cultures Out There, we need to set
ourselves to getting that data.

Think about how large a synthetic optical telescope you could orbit
in the quiet space of a Saturn trojan.

Titeotwawki -- Martha Adams [Thr 2012 Apr 12]

[David V. Loewe, Jr]

Have we actually found an Earth-like planet (no Super-Earths need apply)
in a Goldilocks orbit yet? Also, there seem to be a lot of Hot Jupiters
which I suppose would preclude stable terrestrial orbits in the
Goldilocks Zone.

<http://en.wikipedia.org/wiki/Super-Earth>

<http://en.wikipedia.org/wiki/Habitable_zone>

<http://en.wikipedia.org/wiki/Hot_Jupiter>
--
"A generation that ignores history has no past - and no
future."
-Lazarus Long

[Cryptoengineer]

Very much so. Keith's point re radiation not withstanding, such a
scenario could also lead to the galaxy being partitiioned into
'empires' of more-or-less biochemically compatible zones, each
descended from one place where life originated unseeded.

It seems plausible that once one life-system gets established, it will
prevent others from getting a foothold on the same planet, so each
planet will have one consistent system more-or-less shared with other
nearby systems.

So, maybe the BEMs from Sirius really will come here with a 'To Serve
Man' book. :-)

pt

[David Dyer-Bennet]

Martha Adams <mh...@verizon.net> writes:

> Indeed. Concerning which, it raises a question. If as seems plausible,
> our local galaxy is more or less filled with life-bearing planets; and,
> if life-bearing planets eventually see evolution of intelligent life
> forms and some of those develop technological and even space-going
> beings, then, one would reasonably believe,
>
> 1)We'd find evidence in places like Luna and even here on Terra, that
> *somebody was here and had a look around*; and

The odds of their visiting in person are low unless FTL travel is
possible. Perhaps we'd see their Von Neuman machines running amok at
sub-light speeds -- but I suspect that making mechanisms that last that
long in that environment is VERY hard, AND that making mechanisms smart
enough to find an exploit resources to self-reproduce in an unfamiliar
solar system is ALSO VERY hard.

> 2) SETI would hear several to many other worlds radiating radio and
> etc signals;

We radiate less and less. Most civilizations probably have only a brief
high radiation period, then go to re-using frequencies in cells for more
bandwidth. And we couldn't detect ourselves at peak very far away. So
we probably need people deliberately transmitting to other stars to have
a good chance of picking it up from far away.
--
David Dyer-Bennet, dd...@dd-b.net; http://dd-b.net/
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info

[David Friedman]

In article <KLSdnbh8m_lMQxvS...@giganews.com>,

Martha Adams <mh...@verizon.net> wrote:

> Seems
> to me, what we know of our (deadly) universe today, makes it in fact
> as dead and sterile as our faith-based extremists would make it.

C.S. Lewis, say?

Or in other words, why do you have to introduce an entirely irrelevant
slap at imagined bad guys into your post?

--
http://www.daviddfriedman.com/
http://daviddfriedman.blogspot.com/
_Salamander_: http://tinyurl.com/6957y7e
_How to Milk an Almond,..._ http://tinyurl.com/63xg8gx

[David Loewe, Jr.]

On Thu, 12 Apr 2012, David Dyer-Bennet <dd...@dd-b.net> wrote:

>Martha Adams <mh...@verizon.net> writes:
>
>> Indeed. Concerning which, it raises a question. If as seems plausible,
>> our local galaxy is more or less filled with life-bearing planets; and,
>> if life-bearing planets eventually see evolution of intelligent life
>> forms and some of those develop technological and even space-going
>> beings, then, one would reasonably believe,
>>
>> 1)We'd find evidence in places like Luna and even here on Terra, that
>> *somebody was here and had a look around*; and
>
>The odds of their visiting in person are low unless FTL travel is
>possible. Perhaps we'd see their Von Neuman machines running amok at
>sub-light speeds -- but I suspect that making mechanisms that last that
>long in that environment is VERY hard, AND that making mechanisms smart
>enough to find an exploit resources to self-reproduce in an unfamiliar
>solar system is ALSO VERY hard.

I can't believe that intelligent *technological* life is all that
common. Life on earth seems to be about 3.5 billion years old, yet, in
all of that time, there seems to have only been one species with enough
intelligence *and* technological capability to even be detectable as
intelligent creatures across interstellar distances - and then only
really since the advent of radio.
--
"If we follow the advice of these people, we might as well go back
into the cave."
- Hans Bethe

[Paul Ciszek]

In article <ddfr-8E83FB.0...@news.giganews.com>,

David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
>In article <KLSdnbh8m_lMQxvS...@giganews.com>,
> Martha Adams <mh...@verizon.net> wrote:
>
>> Seems
>> to me, what we know of our (deadly) universe today, makes it in fact
>> as dead and sterile as our faith-based extremists would make it.
>
>C.S. Lewis, say?
>
>Or in other words, why do you have to introduce an entirely irrelevant
>slap at imagined bad guys into your post?

Not imagined. That extraterrestrial life does not exist seems to be a
point of doctrite with many fundamentalists. A religious organization
once brought a group of guest lecturers to the Colorado School of Mines
to make the case for Creationism. One of them, a chemist, made an
argument along these lines: If you believe that abiogenesis could
happen on Earth, then there is no reason it could not occur on any
planet with similar conditions. Given the large number of stars similar
to the sun, an Earth-like planet is bound to exist somewhere. So,
believing in abiogenesis is the same thing as believing that life
exists on other planets. He seemed to think he had proven something,
reducto absurdum style, but the missing piece was his unstated
assumption that there is no life on other planets.


--
Please reply to: | "We establish no religion in this country, we
pciszek at panix dot com | command no worship, we mandate no belief, nor
Autoreply is disabled | will we ever. Church and state are, and must
| remain, separate." --Ronald Reagan, 10/26/1984

[Dorothy J Heydt]

In article <jm7e6u$abc$2...@reader1.panix.com>,

Paul Ciszek <nos...@nospam.com> wrote:
>
>In article <ddfr-8E83FB.0...@news.giganews.com>,
>David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
>>In article <KLSdnbh8m_lMQxvS...@giganews.com>,
>> Martha Adams <mh...@verizon.net> wrote:
>>
>>> Seems
>>> to me, what we know of our (deadly) universe today, makes it in fact
>>> as dead and sterile as our faith-based extremists would make it.
>>
>>C.S. Lewis, say?

Lewis had a lot more respect for science than you seem to think.
What he objected to was the deification of science, and the
assumption that Evolution (personified) is inevitably leading us
toward higher states of being.

--
Dorothy J. Heydt
Vallejo, California
djheydt at gmail dot com
Should you wish to email me, you'd better use the gmail edress.
Kithrup's all spammy and hotmail's been hacked.

[David Friedman]

In article <jm7e6u$abc$2...@reader1.panix.com>,

nos...@nospam.com (Paul Ciszek) wrote:

> In article <ddfr-8E83FB.0...@news.giganews.com>,
> David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
> >In article <KLSdnbh8m_lMQxvS...@giganews.com>,
> > Martha Adams <mh...@verizon.net> wrote:
> >
> >> Seems
> >> to me, what we know of our (deadly) universe today, makes it in fact
> >> as dead and sterile as our faith-based extremists would make it.
> >
> >C.S. Lewis, say?
> >
> >Or in other words, why do you have to introduce an entirely irrelevant
> >slap at imagined bad guys into your post?
>
> Not imagined. That extraterrestrial life does not exist seems to be a
> point of doctrite with many fundamentalists. A religious organization
> once brought a group of guest lecturers to the Colorado School of Mines
> to make the case for Creationism. One of them, a chemist, made an
> argument along these lines: If you believe that abiogenesis could
> happen on Earth, then there is no reason it could not occur on any
> planet with similar conditions. Given the large number of stars similar
> to the sun, an Earth-like planet is bound to exist somewhere. So,
> believing in abiogenesis is the same thing as believing that life
> exists on other planets. He seemed to think he had proven something,
> reducto absurdum style, but the missing piece was his unstated
> assumption that there is no life on other planets.

Perhaps he assumed the next step was obvious. If life is quite likely to
happen, then in some places it should have happened long before it did
here, so there ought to be an alien civilization all over the galaxy by
now, and there doesn't seem to be. Ergo abiogenesis must be, if not
impossible, at least very unlikely.

[David Friedman]

In article <M2Dzn...@kithrup.com>,

djh...@kithrup.com (Dorothy J Heydt) wrote:

> In article <jm7e6u$abc$2...@reader1.panix.com>,
> Paul Ciszek <nos...@nospam.com> wrote:
> >
> >In article <ddfr-8E83FB.0...@news.giganews.com>,
> >David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
> >>In article <KLSdnbh8m_lMQxvS...@giganews.com>,
> >> Martha Adams <mh...@verizon.net> wrote:
> >>
> >>> Seems
> >>> to me, what we know of our (deadly) universe today, makes it in fact
> >>> as dead and sterile as our faith-based extremists would make it.
> >>
> >>C.S. Lewis, say?
>
> Lewis had a lot more respect for science than you seem to think.
> What he objected to was the deification of science, and the
> assumption that Evolution (personified) is inevitably leading us
> toward higher states of being.

My point wasn't that he didn't have respect for science but that he did,
at least in his fiction, take for granted life on other planets.

--

[Martha Adams]

===============================================

I'm afraid this line of reasoning, or something very like it, takes
us somewhere. Of all the species here on Terra, only us homo sapiens
came to technology; and even among us, you see from National Geographic
and from reading your local news, very few did. Which says technology
has to be scarce, that is, very very scarce and we can expect to very
nearly never see it anywhere else. And *that* could be why Seti hears
silence. But there's another possibility.

Which is, technological cultures destroy themselves. How we could do
that here is plain to see: we have this thing going of conservatives
vs well, call them liberals. Conservatives don't do science, liberals
don't do belief by rote or thru an idea the ancients had it right.
Now comes computer science, the conservatives can use it to create a
control wholly fascist in character and ultimately deadly; the result
is a failed and crashed technological culture. A Baxter culture:
lives are nasty, brutish, and short; and the natural resources for the
culture to re-rise, are all used up. (And the oceans poisoned and
etc etc.) It could be a trap technological cultures fall into and
never escape from; it's a reason why we hear none of them.

[Martha Adams]

=========================================================

When 'To Serve Man' first appeared (in ASF, I believe), I thought that
was an interesting turn of words and passed on to the next. In my
later years now I recall recent history (American military vs native
Americans); more distant history (I've read about 90% of native
Americans died of European diseases when the Europeans came in); and
I feel Hawking's point that us meeting aliens is unlikely to turn
out well for us. In that context, I think 'To Serve Man' is usefully
and wonderfully ambiguous. *And relevant today.*

[David V. Loewe, Jr]

Funny...

I'm sure that you'd consider me to be conservative [1], yet I believe in
science and I only pay lip service to religion.

>Now comes computer science, the conservatives can use it to create a
>control wholly fascist in character and ultimately deadly; the result
>is a failed and crashed technological culture. A Baxter culture:
>lives are nasty, brutish, and short; and the natural resources for the
>culture to re-rise, are all used up. (And the oceans poisoned and
>etc etc.) It could be a trap technological cultures fall into and
>never escape from; it's a reason why we hear none of them.

[1] I consider myself to be libertarian with a strong side of
conservative.

[David Friedman]

In article <VZKdnSP5P6lJHBrS...@giganews.com>,

Martha Adams <mh...@verizon.net> wrote:

> Conservatives don't do science, liberals
> don't do belief by rote or thru an idea the ancients had it right.
> Now comes computer science, the conservatives can use it to create a
> control wholly fascist in character and ultimately deadly; the result
> is a failed and crashed technological culture. A Baxter culture:
> lives are nasty, brutish, and short; and the natural resources for the
> culture to re-rise, are all used up. (And the oceans poisoned and
> etc etc.) It could be a trap technological cultures fall into and
> never escape from; it's a reason why we hear none of them.

Alternatively, technological cultures get rich enough to establish a
population of people who are living as parasites on the productive,
either poor parasites on welfare or rich parasites with government jobs.
Once there are enough of them to keep voting themselves more goodies,
the society is on a fatal downward spiral. It could be a trap

technological cultures fall into and never escape from; it's a reason
why we hear none of them.

Makes at least as much sense as your version, with the political bias
reversed.

In my experience, whatever ideology is locally dominant does belief
mostly by rote. I've spent most of my life in American academia, where
liberalism is dominant, so tend to expect liberals to be strikingly
ignorant of the views they confidently reject.

But there are surely parts of American society where I could have spent
my life that would have left me with your reversed version of that view.

You might consider, by the way, that fascism, as a real economic
ideology rather than a mere epithet, has a good deal more in common with
liberal economics than with conservative economics--as demonstrated by
Roosevelt's first New Deal. Private ownership combined with government
control.

[Philip Chee]

On Thu, 12 Apr 2012 09:55:57 -0400, Martha Adams wrote:

> Indeed. Concerning which, it raises a question. If as seems plausible,
> our local galaxy is more or less filled with life-bearing planets; and,
> if life-bearing planets eventually see evolution of intelligent life
> forms and some of those develop technological and even space-going
> beings, then, one would reasonably believe,

I think those sneaky Arisians were behind all this.

Phil

--
Philip Chee <phi...@aleytys.pc.my>, <phili...@gmail.com>
http://flashblock.mozdev.org/ http://xsidebar.mozdev.org
Guard us from the she-wolf and the wolf, and guard us from the thief,
oh Night, and so be good for us to pass.

[David Goldfarb]

In article <dk3fo7d8has06tfrt...@4ax.com>,

David V. Loewe, Jr <dave...@charter.net> wrote:
>I'm sure that you'd consider me to be conservative

You certainly repeat Republican party lines often enough.

--
David Goldfarb | "When the cat calls at midnight, your shorts
goldf...@gmail.com | will ignite."
gold...@ocf.berkeley.edu | -- J. Michael Straczynski

[Paul Dormer]

In article <3oaeo75ea1fhbtc6m...@4ax.com>,

dlo...@mindspring.com (David Loewe, Jr.) wrote:

>
> I can't believe that intelligent *technological* life is all that
> common. Life on earth seems to be about 3.5 billion years old, yet, in
> all of that time, there seems to have only been one species with enough
> intelligence *and* technological capability to even be detectable as
> intelligent creatures across interstellar distances - and then only
> really since the advent of radio.

What's more, for about 3 billion years of that it seems there were only
single-celled organisms. Something happened to start the splurge in
multi-cellular organisms, and that could be a rare event.

I remember a panel item at a con and later a TV programme about the Drake
equation. On the TV programme, I think it was Drake himself who assumed
the factor that if life developed on a planet, there was a 100%
probability that intelligence will develop. (I can't remember over what
time scale that figure was, probably the age of the universe to date, I
guess.) This gave something like 50,000 technological civilisations
around at the moment in our galaxy. Now, if that factor is actually one
in a million...

At the con, the presenter asked for suggestions from the audience for
this factor and I said one in a million, he said that would mean we're
alone and then chose a much more favourable figure to allow him to talk
about a galaxy teeming with intelligent life.

[Jay E. Morris]

Oh bullshit.

> don't do belief by rote or thru an idea the ancients had it right.

Oh double bullshit.

> Now comes computer science, the conservatives can use it to create a
> control wholly fascist in character and ultimately deadly; the result
> is a failed and crashed technological culture. A Baxter culture:
> lives are nasty, brutish, and short; and the natural resources for the
> culture to re-rise, are all used up. (And the oceans poisoned and
> etc etc.) It could be a trap technological cultures fall into and
> never escape from; it's a reason why we hear none of them.
>
> Titeotwawki -- Martha Adams [Thr 2012 Apr 12]
>
> ===============================================
> ** Space Frontier Now! **
> http://www.mhada.info
> ===============================================
>
>
>

I'd expand upon that but I've discovered it just not worth the time and
effort. Nothing will dissuade Martha from her myopic vision of the world.

[David Loewe, Jr.]

On Fri, 13 Apr 2012, gold...@ocf.berkeley.edu (David Goldfarb) wrote:

>David V. Loewe, Jr <dave...@charter.net> wrote:

>>I'm sure that you'd consider me to be conservative
>
>You certainly repeat Republican party lines often enough.

A) What do you mean by Republican "Party lines"? I don't get marching
orders.

B) Do you think that maybe self-awareness of how I come across might
have something to do with me believing that Martha would think I'm a
conservative?
--
"I don't mind you *thinking* I'm stupid, but don't *talk* to me
like I'm stupid."
- Harlan Ellison

[James Nicoll]

In article <VZKdnSP5P6lJHBrS...@giganews.com>,
Martha Adams <mh...@verizon.net> wrote:
>

>I'm afraid this line of reasoning, or something very like it, takes
>us somewhere. Of all the species here on Terra, only us homo sapiens
>came to technology; and even among us, you see from National Geographic
>and from reading your local news, very few did.

I'm curious which human groups you think don't use technology. Could
you expand on this?

--
http://www.livejournal.com/users/james_nicoll
http://www.cafepress.com/jdnicoll (For all your "The problem with
defending the English language [...]" T-shirt, cup and tote-bag needs)

[David Dyer-Bennet]

djh...@kithrup.com (Dorothy J Heydt) writes:

> In article <jm7e6u$abc$2...@reader1.panix.com>,
> Paul Ciszek <nos...@nospam.com> wrote:
>>
>>In article <ddfr-8E83FB.0...@news.giganews.com>,
>>David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
>>>In article <KLSdnbh8m_lMQxvS...@giganews.com>,
>>> Martha Adams <mh...@verizon.net> wrote:
>>>
>>>> Seems
>>>> to me, what we know of our (deadly) universe today, makes it in fact
>>>> as dead and sterile as our faith-based extremists would make it.
>>>
>>>C.S. Lewis, say?
>
> Lewis had a lot more respect for science than you seem to think.
> What he objected to was the deification of science, and the
> assumption that Evolution (personified) is inevitably leading us
> toward higher states of being.

Which is something Darwin himself always had right (though many of his
contemporaries did not). Evolution is NOT directed (kind of the point,
actually). (Doc Smith used "highly evolved" far too often, his
universes clearly had that mistake embedded in them.)

[David Dyer-Bennet]

p...@pauldormer.cix.co.uk (Paul Dormer) writes:

> In article <3oaeo75ea1fhbtc6m...@4ax.com>,
> dlo...@mindspring.com (David Loewe, Jr.) wrote:
>
>>
>> I can't believe that intelligent *technological* life is all that
>> common. Life on earth seems to be about 3.5 billion years old, yet, in
>> all of that time, there seems to have only been one species with enough
>> intelligence *and* technological capability to even be detectable as
>> intelligent creatures across interstellar distances - and then only
>> really since the advent of radio.
>
> What's more, for about 3 billion years of that it seems there were only
> single-celled organisms. Something happened to start the splurge in
> multi-cellular organisms, and that could be a rare event.
>
> I remember a panel item at a con and later a TV programme about the Drake
> equation. On the TV programme, I think it was Drake himself who assumed
> the factor that if life developed on a planet, there was a 100%
> probability that intelligence will develop. (I can't remember over what
> time scale that figure was, probably the age of the universe to date, I
> guess.) This gave something like 50,000 technological civilisations
> around at the moment in our galaxy. Now, if that factor is actually one
> in a million...

We may have just gotten the first evidence against that 100% figure (the
only example we have of a planet that developed life did develop
intelligence, so 100% is in some sense the most-supportable guess for
that figure).

Well, we may have just noticed the evidence; we got it back in the 70s.

But it's kind of equivocal really, if you read the report instead of the
headlines.

I kind of suspect that all planets of suitable composition in a suitable
temp range develop life (because of how many weird niches in Earth have
life with weird metabolic pathways and such; every conceivable niche and
a bunch of inconceivable ones are occupied).

I kind of suspect that every planet with life, and with enough
stability, develops intelligence. (I'm expecting intelligent species to
require high investments in children, and that needs a more stable
environment; low investment and many children works better with a wildly
random environment.)

But "kind of suspect" is very very different from "hold as dogma", and
also from "have decent evidence to support".

[David Loewe, Jr.]

On Fri, 13 Apr 2012 14:53:47 +0000 (UTC), jdni...@panix.com (James
Nicoll) wrote:

>Martha Adams <mh...@verizon.net> wrote:
>>
>>I'm afraid this line of reasoning, or something very like it, takes
>>us somewhere. Of all the species here on Terra, only us homo sapiens
>>came to technology; and even among us, you see from National Geographic
>>and from reading your local news, very few did.
>
>I'm curious which human groups you think don't use technology. Could
>you expand on this?

She responded to a point (of mine) that talked about a technological
level of achievement that is detectable across interstellar distances.
Is it a stretch to assume that she continued on that same line of
thought, James?
--
"Oh now feel it comin' back again
Like a rollin' thunder chasing the wind
Forces pullin' from the center of the earth again
I can feel it."
- Ed Kowalczyk,Chad Taylor,Patrick Dahlheimer
& Chad Gracey

[David V. Loewe, Jr]

On Fri, 13 Apr 2012 10:08:26 -0500, David Dyer-Bennet <dd...@dd-b.net>
wrote:

I believe that there is more than one intelligent species on the planet,
but most of the others (cetaceans) are not configured to build
technologically advanced constructs.
--
"Just think of it as evolution in action."
Tony Rand in Larry Niven and Jerry Pournelle's
'Oath of Fealty'

[Helen Schinske]

On Apr 12, 9:44 am, David Friedman <d...@daviddfriedman.nopsam.com>
wrote:
> In article <KLSdnbh8m_lMQxvSnZ2dnUVZ_v6dn...@giganews.com>,

>  Martha Adams <mh...@verizon.net> wrote:
>
> > Seems
> > to me, what we know of our (deadly) universe today, makes it in fact
> > as dead and sterile as our faith-based extremists would make it.
>
> C.S. Lewis, say?
>
> Or in other words, why do you have to introduce an entirely irrelevant
> slap at imagined bad guys into your post?

Lewis wasn't an extremist, as much as the extremists would like to co-
opt his work.

Helen Schinske

[David Friedman]

In article <jm948l$dlk$1...@dont-email.me>,

"Jay E. Morris" <mor...@epsilon3.com> wrote:

> I'd expand upon that but I've discovered it just not worth the time and
> effort. Nothing will dissuade Martha from her myopic vision of the world.

On the other hand, she is considerably more open about it than many
others who, I suspect, share the vision.

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> p...@pauldormer.cix.co.uk (Paul Dormer) writes:

>> dlo...@mindspring.com (David Loewe, Jr.) wrote:
>>> I can't believe that intelligent *technological* life is all that
>>> common. Life on earth seems to be about 3.5 billion years old,
>>> yet, in all of that time, there seems to have only been one
>>> species with enough intelligence *and* technological capability to
>>> even be detectable as intelligent creatures across interstellar
>>> distances - and then only really since the advent of radio.

It is noteworthy that it took so long.

>> What's more, for about 3 billion years of that it seems there were
>> only single-celled organisms. Something happened to start the
>> splurge in multi-cellular organisms, and that could be a rare event.

That too is noteworthy. Every necessary step that led to a
technological civilization may have been extraordinarily unlikely:
Life, multi-cellular life, intelligence, and technology. (And I'm
probably forgetting a few.)

Curiously, S.M. Stirling suggests that the last step -- the transition
from intelligent life to intelligent life with science and technology
-- is the least likely. I consider it the *most* likely. It certainly
happened the fastest, even if it was very slow on a human timescale.
I wrote an article on this. See
http://wsfa.org/journal/j05/9/index.htm#s

> We may have just gotten the first evidence against that 100% figure
> (the only example we have of a planet that developed life did
> develop intelligence, so 100% is in some sense the most-supportable
> guess for that figure).

There's very strong selection bias there. Whether there's one
intelligent race in the universe or a trillion of them, everyone who
uses that reasoning is going to look at themselves and conclude 100%.
All that we can really conclude from our own existence is that
intelligent life isn't absolutely impossible.

> I kind of suspect that all planets of suitable composition in a
> suitable temp range develop life (because of how many weird niches
> in Earth have life with weird metabolic pathways and such; every
> conceivable niche and a bunch of inconceivable ones are occupied).

That reasoning is not valid. Life almost certainly originated only
once on our planet. It then gradually evolved to fill all those
niches. So the full niches today imply nothing about how likely life
was to have started in the first place.

It seems unlikely that DNA and RNA are the only way to store genetic
information, or that proteins are the only way to build biological
structures. But even if that is the case, the genetic code that maps
DNA into proteins is certainly completely arbitrary. And yet it's
almost exactly the same for everything from bacteria to oak trees to
people, showing that all life on our planet had a common ancestry.
(Not to mention the surprising number of genes that very different
organisms have in common.) So it's not as if life began separately
in each niche.

> I kind of suspect that every planet with life, and with enough
> stability, develops intelligence.

That seems more plausible. But the fact that intelligence took
billions of years to develop on our planet is strong evidence
against it.

> (I'm expecting intelligent species to require high investments in
> children, and that needs a more stable environment; low investment
> and many children works better with a wildly random environment.)

True. Also, it's plausible that catastrophes that wipe out *all* life
on a planet are quite common. Maybe life started on billions of
planets in our galaxy, and ours, by chance, is the only one in which
there hasn't yet been a single catastrophe big enough to end all life.

> But "kind of suspect" is very very different from "hold as dogma",
> and also from "have decent evidence to support".

Indeed. We know almost nothing about extraterrestrial life, except
that it's neither impossible nor ubiquitous. The Drake equation
consists almost entirely of unknowns.
--
Keith F. Lynch - http://keithlynch.net/
Please see http://keithlynch.net/email.html before emailing me.

[Keith F. Lynch]

James Nicoll <jdni...@panix.com> wrote:
> Martha Adams <mh...@verizon.net> wrote:
>> I'm afraid this line of reasoning, or something very like it,
>> takes us somewhere. Of all the species here on Terra, only us
>> homo sapiens came to technology; and even among us, you see from
>> National Geographic and from reading your local news, very few did.

> I'm curious which human groups you think don't use technology. Could
> you expand on this?

I think she means most groups of early humans went extinct, as shown
by our lack of genetic diversity.

[Keith F. Lynch]

Martha Adams <mh...@verizon.net> wrote:
> But there's another possibility.

> Which is, technological cultures destroy themselves. How we
> could do that here is plain to see: we have this thing going
> of conservatives vs well, call them liberals.

Oh, give it a rest.

> Conservatives don't do science,

You're old enough to remember the Goldwater campaign. Were people
afraid he would destroy the world? Some were. But the fear was that
he would do so with nuclear weapons. Not exactly anti-science.

> liberals don't do belief by rote ...

Rubbish. They're extremely doctrinaire, even more so than
conservatives.

> Now comes computer science, the conservatives can use it to create a
> control wholly fascist in character and ultimately deadly;

I thought you said conservatives were anti-science.

Do you think liberals are any less in favor of a mass surveillance
"papers please" society, with cameras, metal detectors, and ID
checkpoints everywhere? Why?

> the result is a failed and crashed technological culture. A Baxter
> culture: lives are nasty, brutish, and short;

Which Baxter novel are you thinking of here?

[Keith F. Lynch]

Dorothy J Heydt <djh...@kithrup.com> wrote:
> Lewis had a lot more respect for science than you seem to think.
> What he objected to was the deification of science, and the
> assumption that Evolution (personified) is inevitably leading us
> toward higher states of being.

Is there anyone who deifies science? Who? Is there anyone who
assumes that evolution is leading us toward higher states of being?
Who? Darwin didn't. Stephen Jay Gould didn't.

[Keith F. Lynch]

Paul Ciszek <nos...@nospam.com> wrote:
> That extraterrestrial life does not exist seems to be a point of
> doctrite with many fundamentalists.

Who? None that I've ever heard of.

> A religious organization once brought a group of guest lecturers
> to the Colorado School of Mines to make the case for Creationism.
> One of them, a chemist, made an argument along these lines: If you
> believe that abiogenesis could happen on Earth, then there is no
> reason it could not occur on any planet with similar conditions.

True.

> Given the large number of stars similar to the sun, an Earth-like
> planet is bound to exist somewhere. So, believing in abiogenesis
> is the same thing as believing that life exists on other planets.

No. Abiogenesis could be so extraordinarily unlikely that it's only
ever happened once. We just don't know.

> He seemed to think he had proven something, reducto absurdum style,
> but the missing piece was his unstated assumption that there is no
> life on other planets.

That too we just don't know.

[Keith F. Lynch]

David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
> Martha Adams <mh...@verizon.net> wrote:

>> Seems to me, what we know of our (deadly) universe today, makes it
>> in fact as dead and sterile as our faith-based extremists would
>> make it.

> C.S. Lewis, say?

> Or in other words, why do you have to introduce an entirely
> irrelevant slap at imagined bad guys into your post?

At least she didn't mention Republicans. Give her credit for that.
She could have said life always goes extinct because every planet
elects George W. Bush.

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> The odds of their visiting in person are low unless FTL travel
> is possible.

Not necessarily. Our galaxy is about 13 billion years old.
Starting at the edge, traveling at just one thousandth of the
speed of light, they could colonize the whole galaxy in less
than one percent of that time.

> Perhaps we'd see their Von Neuman machines running amok at sub-light
> speeds -- but I suspect that making mechanisms that last that long
> in that environment is VERY hard, AND that making mechanisms smart
> enough to find an exploit resources to self-reproduce in an
> unfamiliar solar system is ALSO VERY hard.

I'm sure it is very hard. It would probably take more than a century
of design and testing. :-)

[Keith F. Lynch]

Martha Adams <mh...@verizon.net> wrote:
> Keith F. Lynch wrote:
>> And passed through an average-sized solar system at that distance?
>> Plausible. And hit a planet in that solar system? Not plausible.
>> It's late, so I'll leave the math for another night. Or I'll leave
>> it as an exercise for the reader: If each Earth-sized area 20
>> light years away intercepted a thousand rocks, how many rocks must
>> there have been in total? I know without calculating it that it
>> would be an absurdly large number.

A sphere 20 light years in radius has a surface area of about 4E+35
square meters. An Earth-sized planet has a cross-sectional area of
about 1.3E14 square meters. So if a thousand rocks from Earth hit it,
there must have been about 3E+24 rocks from Earth.

For a rock to be able to shield life at its center from a million
years of cosmic radiation, it would have to have a volume of at least
a cubic meter. So 3E+24 cubic meters of rocks must have been blasted
out of Earth. But that's 3000 times the total volume of our planet!

In other words, if our whole planet were to be reduced to one-cubic
meter rocks, and every one of them somehow achieved escape velocity
from our solar system, an Earth-sized planet 20 light years away would
have about a one in three chance of intercepting just one of them.
That one would probably be from Earth's lifeless deep interior. And
unless its entry angle was very shallow, like a reentering space
capsule, it would certainly burn up in the atmosphere.

Even if the rock originated in Earth's biosphere, how would life have
gotten into its center unless the rock was porous? And if it was
porous, why wouldn't it break into fragments during the impact, rather
than being ejected in one piece? Try calculating just how many Gs of
acceleration a rock would have to be subjected to to be kicked to
escape velocity. I'm not sure any one-cubic-meter solid object could
survive that at all, even if it was made out of steel or titanium.

> My perception of Keith's thinking is, "Yes, but no." Because, both
> are true. We are looking at very small but non zero probabilities
> here.

True. But the probabilities are very, very, very, very close to zero.
I'd like to know how the authors got their figure of a thousand rocks.
The fact that they named a particular destination star, not realizing
it was far away at the relevant time, implies that they can't be
trusted to know what they're talking about.

> My thinking is that, "...but always, we will find surprises."

I'm sure we will. There is much that we don't know. But there is
also much that we *do* know. And I'm willing and able to do the math
on the latter. Are you?

> Think about how large a synthetic optical telescope you could orbit
> in the quiet space of a Saturn trojan.

That would be a nice gadget to have. Good luck finding someone
willing and able to pay for it.

[David V. Loewe, Jr]

On Sat, 14 Apr 2012 22:35:04 +0000 (UTC), "Keith F. Lynch"
<k...@KeithLynch.net> wrote:

>Martha Adams <mh...@verizon.net> wrote:
>> Keith F. Lynch wrote:

>>> And passed through an average-sized solar system at that distance?
>>> Plausible. And hit a planet in that solar system? Not plausible.
>>> It's late, so I'll leave the math for another night. Or I'll leave
>>> it as an exercise for the reader: If each Earth-sized area 20
>>> light years away intercepted a thousand rocks, how many rocks must
>>> there have been in total? I know without calculating it that it
>>> would be an absurdly large number.
>
>A sphere 20 light years in radius has a surface area of about 4E+35
>square meters. An Earth-sized planet has a cross-sectional area of
>about 1.3E14 square meters. So if a thousand rocks from Earth hit it,
>there must have been about 3E+24 rocks from Earth.

Are you taking into account gravitational attraction?
--
"It's raining soup and we haven't built any soup bowls."
Dr. Jerry Pournelle

[garabik-ne...@kassiopeia.juls.savba.sk]

Keith F. Lynch <k...@keithlynch.net> wrote:
> Paul Ciszek <nos...@nospam.com> wrote:
>> That extraterrestrial life does not exist seems to be a point of
>> doctrite with many fundamentalists.
>
> Who? None that I've ever heard of.

My colleague. She is not exactly a fundamentalist, but she does not talk
with me anymore since some time - my (at the time I thought) idle talk
during lunch about extraterrestrials probably contributed to it.
I did, according to her own words, "rip straight into the heart of her
belief" and "she almost burst into tears" because "I intentionally tried
to hurt her with my satanist speech".

--
-----------------------------------------------------------
| Radovan Garabík http://kassiopeia.juls.savba.sk/~garabik/ |
| __..--^^^--..__ garabik @ kassiopeia.juls.savba.sk |
-----------------------------------------------------------
Antivirus alert: file .signature infected by signature virus.
Hi! I'm a signature virus! Copy me into your signature file to help me spread!

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> djh...@kithrup.com (Dorothy J Heydt) writes:
>> Lewis had a lot more respect for science than you seem to think.
>> What he objected to was the deification of science, and the
>> assumption that Evolution (personified) is inevitably leading
>> us toward higher states of being.

> Which is something Darwin himself always had right (though many of
> his contemporaries did not). Evolution is NOT directed (kind of the
> point, actually). (Doc Smith used "highly evolved" far too often,
> his universes clearly had that mistake embedded in them.)

Whose ideas was Lewis objecting to? Who ever deified science? Who,
besides a few misguided 19th century philosophers and a few confused
20th century hack writers ever believed evolution was directed, or
that it inevitably led mankind to become more intelligent, more moral,
or better in any other non-tautological sense?

Since there's no selective pressure for intelligence or morality,
those are not being selected for and are not increasing in the
population. The strongest selective pressure on our species today
is probably for contraceptives to stop working.

[Keith F. Lynch]

Martha Adams <mh...@verizon.net> wrote:
> Yet, our best observation today finds nothing yet of that. Seems to

> me, what we know of our (deadly) universe today, makes it in fact as
> dead and sterile as our faith-based extremists would make it.

It's certainly possible that we're alone in the universe. I've
never heard a persuasive argument that we are definitely not alone.
But it's far too soon to know. If every star had a planet with
a civilization comparable to ours, we would have detected nothing.
(Arecibo and the Deep Space Network might have been barely able to
detect stray leakage from an Earth-like civilization around Proxima
Centauri, but only if a determined effort had been made.)

We do know that life isn't ubiquitous. There's almost certainly no
life on the Moon or Venus, and probably no life on Mars. And of
course aliens or their probes never converted all the mass of our
solar system into shopping malls, condominiums, or other artifacts for
their own purposes.

As we continue to expand into the universe, we'll either find life or
set new upper limits on how common it could be. But if we are alone,
we'll probably never know that for sure. Not unless we thoroughly
inspect the surfaces and interiors of every planet, moon, asteroid,
comet, and everything else large enough to hold the smallest possible
intelligent being, not just in our galaxy but in the entire universe.
That would be quite a project. And even then, there could be
something we overlooked, such as life formed of standing-wave patterns
inside neutron stars, or made of supersymmetric matter that barely
interacts with matter as we know it.

As for "faith-based extremists," I'm not aware of any correlation in
either direction between belief in God and belief in alien life. Some
sects (e.g. Mormons) believe alien life definitely exists. I can't
think of any that believe it definitely does not exist.

[David Friedman]

In article <jmffal$ab9$1...@reader1.panix.com>,

"Keith F. Lynch" <k...@KeithLynch.net> wrote:

> And of
> course aliens or their probes never converted all the mass of our
> solar system into shopping malls, condominiums, or other artifacts for
> their own purposes.

That assumes you could recognize mass being used for their purposes. For
all you know, the solar system as it now exists is a work of art done by
an alien artist--perhaps the alien equivalent of a five year old playing
with clay.

[Keith F. Lynch]

David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
> "Keith F. Lynch" <k...@KeithLynch.net> wrote:
>> And of course aliens or their probes never converted all the mass
>> of our solar system into shopping malls, condominiums, or other
>> artifacts for their own purposes.

> That assumes you could recognize mass being used for their purposes.
> For all you know, the solar system as it now exists is a work of art
> done by an alien artist--perhaps the alien equivalent of a five year
> old playing with clay.

Or Earth could be a supercomputer built by mice.

Whenever possible I prefer to explain things without invoking aliens.
If someone finds a crashed flying saucer made of some unknown alloy,
filled with machinery we can't understand, labeled in an unknown
language, that's evidence that aliens made it. (Or human pranksters
with way too much time and money.) But if someone points to an
ordinary rock and says it was made by aliens, I'd want to see
persuasive evidence.

[David Friedman]

In article <jmfhrt$e23$1...@reader1.panix.com>,

"Keith F. Lynch" <k...@KeithLynch.net> wrote:

> David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
> > "Keith F. Lynch" <k...@KeithLynch.net> wrote:
> >> And of course aliens or their probes never converted all the mass
> >> of our solar system into shopping malls, condominiums, or other
> >> artifacts for their own purposes.
>
> > That assumes you could recognize mass being used for their purposes.
> > For all you know, the solar system as it now exists is a work of art
> > done by an alien artist--perhaps the alien equivalent of a five year
> > old playing with clay.
>
> Or Earth could be a supercomputer built by mice.
>
> Whenever possible I prefer to explain things without invoking aliens.
> If someone finds a crashed flying saucer made of some unknown alloy,
> filled with machinery we can't understand, labeled in an unknown
> language, that's evidence that aliens made it. (Or human pranksters
> with way too much time and money.) But if someone points to an
> ordinary rock and says it was made by aliens, I'd want to see
> persuasive evidence.

A reasonable standard for rejecting a positive claim--but, of course, I
wasn't claiming that the solar system was such a work. I was merely
rejecting your claim that we knew it wasn't.

[David Goldfarb]

In article <jmfe33$p1s$3...@reader1.panix.com>,

Keith F. Lynch <k...@KeithLynch.net> wrote:

>The strongest selective pressure on our species today
>is probably for contraceptives to stop working.

Or for people to stop wanting to use them. I've speculated before that
in a thousand years parenthood will be a central concern of much art,
in the same way that love and sex is a central concern of much art today.

--
David Goldfarb |"Atheists view their theist friends with
goldf...@gmail.com | much the same feeling as nonsmokers do
gold...@ocf.berkeley.edu | their smoking friends."
| -- David R. Henry, on rec.arts.comics.xbooks

[David Loewe, Jr.]

On Thu, 12 Apr 2012 02:57:22 +0000 (UTC), "Keith F. Lynch"
<k...@KeithLynch.net> wrote:

>> David V. Loewe, Jr wrote:

>>> Hara and co go further and estimate how much ought to have made its
>>> way to Gliese 581, a red dwarf some 20 light years from here that
>>> is thought to have a super-Earth orbiting at the edge of the
>>> habitable zone.
>
>That star's radial motion relative to us, according to Wikipedia,
>is about 9.5 kilometers per second. That means that during the KT
>impact it was about 2000 light years away, not 20.
>
>Of course there were likely other solar systems within 20 light year
>of us then, so I'll substitute one of them.

Keith's words remind me of a discussion over in rasftv (or was it ratv?)
when Terra Nova was airing.

Is there any chance of being able to project what the night sky would
have looked like during the Santonian stage of the Cretaceous? I said
No as many of the stars we see now would not have been born yet [1],
some of the stars we see now are giants which would have been invisible
when on the Main Sequence, many of the stars that one would have been
able to see would have blown up (or turned into white dwarfs) and most
of the stars would have been carried by their galactic orbits into or
from places were they would not be visible with the unaided eye [2].

[1] Frex, as far as I know and can tell from researching online, every
major star in Orion was born in the Neogene (Betelgeuse, Bellatrix,
Saiph, Alnilam, Alnitak & Mintaka) or Quaternary (Rigel).

[2] Frex, Alpha Centauri will move considerably, brighten and, then,
fade into invisibility within the next 100,000 years.

<http://en.wikipedia.org/wiki/Alpha_Centauri#High_proper_motion_star>

<http://en.wikipedia.org/wiki/Historical_brightest_stars>
--
"Take me to the magic of the moment
On a glory night
Where the children of tomorrow share their dreams
With you and me"
- Klaus Meine

[Cryptoengineer]

On Apr 15, 5:21 am, garabik-news-2005...@kassiopeia.juls.savba.sk
wrote:

> Keith F. Lynch <k...@keithlynch.net> wrote:
>
> > Paul Ciszek <nos...@nospam.com> wrote:
> >> That extraterrestrial life does not exist seems to be a point of
> >> doctrite with many fundamentalists.
>
> > Who?  None that I've ever heard of.
>
> My colleague. She is not exactly a fundamentalist, but she does not talk
> with me anymore since some time - my (at the time I thought) idle talk
> during lunch about extraterrestrials probably contributed to it.
> I did, according to her own words, "rip straight into the heart of her
> belief" and "she almost burst into tears" because "I intentionally tried
> to hurt her with my satanist speech".

Wow. I thought such know-nothings were restricted to my country.

pt

[David Dyer-Bennet]

"Keith F. Lynch" <k...@KeithLynch.net> writes:

> Dorothy J Heydt <djh...@kithrup.com> wrote:
>> Lewis had a lot more respect for science than you seem to think.
>> What he objected to was the deification of science, and the
>> assumption that Evolution (personified) is inevitably leading us
>> toward higher states of being.
>
> Is there anyone who deifies science? Who? Is there anyone who
> assumes that evolution is leading us toward higher states of being?
> Who? Darwin didn't. Stephen Jay Gould didn't.

For evolution, Doc Smith uses the "directed evolution" metaphor
unfortunately often. References to "highly evolved" individuals and
such .

I do think it was extremely widespread among Darwin's contemporaries (he
clearly understood it better than they did; but then, he would).

[David Dyer-Bennet]

"Keith F. Lynch" <k...@KeithLynch.net> writes:

> Martha Adams <mh...@verizon.net> wrote:
>> Keith F. Lynch wrote:
>>> And passed through an average-sized solar system at that distance?
>>> Plausible. And hit a planet in that solar system? Not plausible.
>>> It's late, so I'll leave the math for another night. Or I'll leave
>>> it as an exercise for the reader: If each Earth-sized area 20
>>> light years away intercepted a thousand rocks, how many rocks must
>>> there have been in total? I know without calculating it that it
>>> would be an absurdly large number.
>
> A sphere 20 light years in radius has a surface area of about 4E+35
> square meters. An Earth-sized planet has a cross-sectional area of
> about 1.3E14 square meters. So if a thousand rocks from Earth hit it,
> there must have been about 3E+24 rocks from Earth.

Neglecting gravity. But in fact the rocks don't travel through space
purely at random.

> For a rock to be able to shield life at its center from a million
> years of cosmic radiation, it would have to have a volume of at least
> a cubic meter. So 3E+24 cubic meters of rocks must have been blasted
> out of Earth. But that's 3000 times the total volume of our planet!

Hmmm; that may be the problem. You're thinking of actual interstellar
cosmic radiation, not just the local bits, right? Since distance from
the sun is apparently irrelevant?

Lesser amounts of shielding don't instantly render it impossible,
though, they just render survival less likely.

> In other words, if our whole planet were to be reduced to one-cubic
> meter rocks, and every one of them somehow achieved escape velocity
> from our solar system, an Earth-sized planet 20 light years away would
> have about a one in three chance of intercepting just one of them.
> That one would probably be from Earth's lifeless deep interior. And
> unless its entry angle was very shallow, like a reentering space
> capsule, it would certainly burn up in the atmosphere.
>
> Even if the rock originated in Earth's biosphere, how would life have
> gotten into its center unless the rock was porous? And if it was
> porous, why wouldn't it break into fragments during the impact, rather
> than being ejected in one piece? Try calculating just how many Gs of
> acceleration a rock would have to be subjected to to be kicked to
> escape velocity. I'm not sure any one-cubic-meter solid object could
> survive that at all, even if it was made out of steel or titanium.

Well, much of the mantle is permeated with life currently. Since it's
mostly bacterial, that's probably been true for a long long time.

[David Dyer-Bennet]

"Keith F. Lynch" <k...@KeithLynch.net> writes:

> David Dyer-Bennet <dd...@dd-b.net> wrote:
>> djh...@kithrup.com (Dorothy J Heydt) writes:
>>> Lewis had a lot more respect for science than you seem to think.
>>> What he objected to was the deification of science, and the
>>> assumption that Evolution (personified) is inevitably leading
>>> us toward higher states of being.
>
>> Which is something Darwin himself always had right (though many of
>> his contemporaries did not). Evolution is NOT directed (kind of the
>> point, actually). (Doc Smith used "highly evolved" far too often,
>> his universes clearly had that mistake embedded in them.)
>
> Whose ideas was Lewis objecting to? Who ever deified science? Who,
> besides a few misguided 19th century philosophers and a few confused
> 20th century hack writers ever believed evolution was directed, or
> that it inevitably led mankind to become more intelligent, more moral,
> or better in any other non-tautological sense?

A lot of people wrote in terms of deifying science -- I think because
it's what they were used to, and they were ripe to get out from under
religion, but their habits of speech and thought remained. Sometimes it
was put in terms of science for the glory of god, too -- both sides
wanted to claim it, since it was the hot new thing. (Not that new, but
having really visible economic consequences).

Lots of writing from Victorian up through, er, today, has this basic
misunderstanding of evolution in it, it's not at all rare. I believe
Gould wrote much of a book about it at one point, in fact. Dawkins in
fact was writing things like "tendency for lineages to improve
cumulatively their adaptive fit to their particular way of life, by
increasing the numbers of features which combine together in adaptive
complexes. ... By this definition, adaptive evolution is not just
incidentally progressive, it is deeply, dyed-in-the wool, indispensably
progressive." So it's not dead yet.

> Since there's no selective pressure for intelligence or morality,
> those are not being selected for and are not increasing in the
> population. The strongest selective pressure on our species today
> is probably for contraceptives to stop working.

The theory that there's no selective pressure for either of those is far
from proven; and there's *some* need to explain the development of
intelligence, given that we spend a big chunk of our bodily resources on
the brain.

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> Lots of writing from Victorian up through, er, today, has this basic
> misunderstanding of evolution in it, it's not at all rare.

Darwin's main insight was precisely the rejection of this old idea.

> I believe Gould wrote much of a book about it at one point, in fact.

Yes, and it wasn't clear to me that there was anyone there for him to
argue against.

> Dawkins in fact was writing things like "tendency for lineages to
> improve cumulatively their adaptive fit to their particular way of
> life, by increasing the numbers of features which combine together
> in adaptive complexes. ... By this definition, adaptive evolution
> is not just incidentally progressive, it is deeply, dyed-in-the wool,
> indispensably progressive." So it's not dead yet.

That's a different meaning of "progressive," one I hope Dawkins makes
explicit elsewhere in that work. Is it "progressive" for a cave fish
to lose its eyesight? For a parasitic worm to lose its digestive
system and rely on its host's? For a man to rape many women rather
than marrying one, if the former leads to more progeny?

> "Keith F. Lynch" <k...@KeithLynch.net> wrote:

>> Since there's no selective pressure for intelligence or morality,
>> those are not being selected for and are not increasing in the
>> population. The strongest selective pressure on our species today
>> is probably for contraceptives to stop working.

> The theory that there's no selective pressure for either of those is
> far from proven; and there's *some* need to explain the development
> of intelligence, given that we spend a big chunk of our bodily
> resources on the brain.

Certainly there was selective pressure for intelligence in the past.
I don't think there is any today, at least not in American culture.
A moron is apt to have at least as many children as a genius.
(ObSF: _The Marching Morons_, _Idiocracy_.)

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> "Keith F. Lynch" <k...@KeithLynch.net> writes:
>> A sphere 20 light years in radius has a surface area of about 4E+35
>> square meters. An Earth-sized planet has a cross-sectional area of
>> about 1.3E14 square meters. So if a thousand rocks from Earth hit
>> it, there must have been about 3E+24 rocks from Earth.

> Neglecting gravity.

The rock would be approaching at solar-system escape velocity.
At such a speed, the destination planet's gravity would increase
its "capture cross-section" by at most only a few percent. The
destination star would have a similar, small, effect. When I get
a round tuit, I'll do the math. Unless someone beats me to it.

> But in fact the rocks don't travel through space purely at random.

They pretty much do. Any rock blasted off the Earth will be in an
Earth-crossing solar orbit. Many of them will eventually hit the
Earth or the Moon. Those that make close passes to the Earth will
have their eccentricity and orbital plane randomized. Some will make
close passes to other planets, or crash into them. Ones that pass
close to Jupiter may be boosted to solar system escape. (Or may lose
instead of gain velocity, and fall into the sun.) The ones that
escape are just as likely to have done so by passing over Jupiter's
pole as its equator, or somewhere in between. So there will be no
tendency for escaping rocks to travel in the ecliptic plane, or with
any other particular bias.

And even if there was a directional bias, since nearby stars are
scattered in random directions, it doesn't matter. (Very distant
stars are biased toward being in the galactic plane. But that's
tilted by about 60 degrees relative to the ecliptic plane anyway.)

>> For a rock to be able to shield life at its center from a million
>> years of cosmic radiation, it would have to have a volume of at
>> least a cubic meter. So 3E+24 cubic meters of rocks must have been
>> blasted out of Earth. But that's 3000 times the total volume of
>> our planet!

> Hmmm; that may be the problem. You're thinking of actual
> interstellar cosmic radiation, not just the local bits, right?

Both. Of course in the best case the rock would spend nearly all
its time in interstellar space rather than waiting millions of years
before passing close to Jupiter and being ejected from the solar
system. Not only does hanging out in the solar system increase the
total travel time, it subjects the rock to ionizing radiation from the
sun, and it subjects the rock to *heat*. Spores may last a million
years in cryogenic cold, but they certainly don't last that long at
anything close to room temperature. And something in an Earth-crossing
orbit is not going to be cryogenically cold.

> Lesser amounts of shielding don't instantly render it impossible,
> though, they just render survival less likely.

It gradually slides from very, very unlikely to absurdly unliekly.
It's about like walking a mile in a heavy thunderstorm and remaining
dry because all the raindrops just happen to miss you. That *could*
happen, but it's almost certainly never happened to anyone ever, and
it almost certainly never will.

Another problem with small rocks is the initial heating. The K-T
impact certainly produced a tremendous amount of heat, and it's hard
to see how anything nearby could escape being vaporized. If it could,
it would certainly at least get white-hot on the outside. So it had
better be thick and made of something that's a good thermal insulator
unless you want to deliver charcoal to the destination planet rather
than life.

>> And unless its entry angle was very shallow, like a reentering
>> space capsule, it would certainly burn up in the atmosphere.

As an aside, burning up in the atmosphere is not a problem on leaving
Earth. That's because of the weird dynamics of a K-T-sized impact.
The asteroid is traveling at escape velocity or faster, and would
lose almost no velocity in the atmosphere, which means that unless it
struck at a very shallow angle it would pass through most of Earth's
atmosphere in less than a second. And it's wide enough that when it
hits there wouldn't yet have been time for air to rush back into the
hole it left. So there would briefly be a tunnel of hard vacuum
extending right down to the surface of the Earth!

A direct rock-to-rock impact, like a baseball bat hitting a baseball,
would push the struck rocks *away* from this tunnel. But that's not
a useful process anyway, as it's hypersonic. When objects collide at
a speed greater than the speed of sound in the objects, the impulse
doesn't have time to propagate. So the objects would be destroyed,
not pushed. If a rock is successfully launched, it would be by
"surfing" a pressure wave, like a bullet in a gun barrel. And that's
likely to happen in all directions (except down), including right
into the tunnel of vacuum.

Indeed, the K-T catastrophe more than a thousand miles from the impact
probably consisted mostly of re-entering secondary meteors, the ones
that didn't reach Earth escape velocity. All those meteors burning
up at once would have heated the sky to incandescence everywhere,
and incinerated everything that wasn't deep underground or deep
underwater. The patterns of extinctions match this.

> Well, much of the mantle is permeated with life currently.

No. The mantle is red hot near the top, and even hotter lower down.
Any carbon compounds would be converted to charcoal. Or to graphite.
Or to diamond.

[David Dyer-Bennet]

"Keith F. Lynch" <k...@KeithLynch.net> writes:

> David Dyer-Bennet <dd...@dd-b.net> wrote:
>> "Keith F. Lynch" <k...@KeithLynch.net> writes:
>>> A sphere 20 light years in radius has a surface area of about 4E+35
>>> square meters. An Earth-sized planet has a cross-sectional area of
>>> about 1.3E14 square meters. So if a thousand rocks from Earth hit
>>> it, there must have been about 3E+24 rocks from Earth.
>
>> Neglecting gravity.
>
> The rock would be approaching at solar-system escape velocity.
> At such a speed, the destination planet's gravity would increase
> its "capture cross-section" by at most only a few percent. The
> destination star would have a similar, small, effect. When I get
> a round tuit, I'll do the math. Unless someone beats me to it.

Ain't gonna be me, I was a *pure* mathematician, and it was 40 years
ago.

Yes, makes less difference for interstellar transmission, wihch does
seem to be getting unlikely.

>> But in fact the rocks don't travel through space purely at random.
>
> They pretty much do. Any rock blasted off the Earth will be in an
> Earth-crossing solar orbit. Many of them will eventually hit the
> Earth or the Moon. Those that make close passes to the Earth will
> have their eccentricity and orbital plane randomized. Some will make
> close passes to other planets, or crash into them. Ones that pass
> close to Jupiter may be boosted to solar system escape. (Or may lose
> instead of gain velocity, and fall into the sun.) The ones that
> escape are just as likely to have done so by passing over Jupiter's
> pole as its equator, or somewhere in between. So there will be no
> tendency for escaping rocks to travel in the ecliptic plane, or with
> any other particular bias.
>
> And even if there was a directional bias, since nearby stars are
> scattered in random directions, it doesn't matter. (Very distant
> stars are biased toward being in the galactic plane. But that's
> tilted by about 60 degrees relative to the ecliptic plane anyway.)

All true; but I was referring to gravitational attraction, not to
initial departure direction.

>>> For a rock to be able to shield life at its center from a million
>>> years of cosmic radiation, it would have to have a volume of at
>>> least a cubic meter. So 3E+24 cubic meters of rocks must have been
>>> blasted out of Earth. But that's 3000 times the total volume of
>>> our planet!
>
>> Hmmm; that may be the problem. You're thinking of actual
>> interstellar cosmic radiation, not just the local bits, right?
>
> Both. Of course in the best case the rock would spend nearly all
> its time in interstellar space rather than waiting millions of years
> before passing close to Jupiter and being ejected from the solar
> system. Not only does hanging out in the solar system increase the
> total travel time, it subjects the rock to ionizing radiation from the
> sun, and it subjects the rock to *heat*. Spores may last a million
> years in cryogenic cold, but they certainly don't last that long at
> anything close to room temperature. And something in an Earth-crossing
> orbit is not going to be cryogenically cold.
>
>> Lesser amounts of shielding don't instantly render it impossible,
>> though, they just render survival less likely.
>
> It gradually slides from very, very unlikely to absurdly unliekly.
> It's about like walking a mile in a heavy thunderstorm and remaining
> dry because all the raindrops just happen to miss you. That *could*
> happen, but it's almost certainly never happened to anyone ever, and
> it almost certainly never will.

Or it did, but then the air all went up to the corner of the room and
they died before they could report the previous unlikely event :-) .

> Another problem with small rocks is the initial heating. The K-T
> impact certainly produced a tremendous amount of heat, and it's hard
> to see how anything nearby could escape being vaporized. If it could,
> it would certainly at least get white-hot on the outside. So it had
> better be thick and made of something that's a good thermal insulator
> unless you want to deliver charcoal to the destination planet rather
> than life.

Sure, lots of heat running around right where the energy comes from.

>>> And unless its entry angle was very shallow, like a reentering
>>> space capsule, it would certainly burn up in the atmosphere.
>
> As an aside, burning up in the atmosphere is not a problem on leaving
> Earth. That's because of the weird dynamics of a K-T-sized impact.
> The asteroid is traveling at escape velocity or faster, and would
> lose almost no velocity in the atmosphere, which means that unless it
> struck at a very shallow angle it would pass through most of Earth's
> atmosphere in less than a second. And it's wide enough that when it
> hits there wouldn't yet have been time for air to rush back into the
> hole it left. So there would briefly be a tunnel of hard vacuum
> extending right down to the surface of the Earth!

Yes, that's a strange one (though I've encountered it before).

> A direct rock-to-rock impact, like a baseball bat hitting a baseball,
> would push the struck rocks *away* from this tunnel. But that's not
> a useful process anyway, as it's hypersonic. When objects collide at
> a speed greater than the speed of sound in the objects, the impulse
> doesn't have time to propagate. So the objects would be destroyed,
> not pushed. If a rock is successfully launched, it would be by
> "surfing" a pressure wave, like a bullet in a gun barrel. And that's
> likely to happen in all directions (except down), including right
> into the tunnel of vacuum.
>
> Indeed, the K-T catastrophe more than a thousand miles from the impact
> probably consisted mostly of re-entering secondary meteors, the ones
> that didn't reach Earth escape velocity. All those meteors burning
> up at once would have heated the sky to incandescence everywhere,
> and incinerated everything that wasn't deep underground or deep
> underwater. The patterns of extinctions match this.
>
>> Well, much of the mantle is permeated with life currently.
>
> No. The mantle is red hot near the top, and even hotter lower down.
> Any carbon compounds would be converted to charcoal. Or to graphite.
> Or to diamond.

Oops, yeah, wrong term got to the fingers. Layer up from there.
Crust. There we go.

[David Friedman]

In article <ylfkhawi...@dd-b.net>,

David Dyer-Bennet <dd...@dd-b.net> wrote:

> >> Well, much of the mantle is permeated with life currently.
> >
> > No. The mantle is red hot near the top, and even hotter lower down.
> > Any carbon compounds would be converted to charcoal. Or to graphite.
> > Or to diamond.
>
> Oops, yeah, wrong term got to the fingers. Layer up from there.
> Crust. There we go.
> --

More important than the terminology, the layer you are describing, while
of some importance to us, makes up a negligible fraction of the earth's
mass.

[David Dyer-Bennet]

David Friedman <dd...@daviddfriedman.nopsam.com> writes:

> In article <ylfkhawi...@dd-b.net>,
> David Dyer-Bennet <dd...@dd-b.net> wrote:
>
>> >> Well, much of the mantle is permeated with life currently.
>> >
>> > No. The mantle is red hot near the top, and even hotter lower down.
>> > Any carbon compounds would be converted to charcoal. Or to graphite.
>> > Or to diamond.
>>
>> Oops, yeah, wrong term got to the fingers. Layer up from there.
>> Crust. There we go.
>

> More important than the terminology, the layer you are describing, while
> of some importance to us, makes up a negligible fraction of the earth's
> mass.

But we're not proposing breaking up the entire earth, either. Won't
bits blown off by impact events come almost entirely from the crust?

[David Friedman]

In article <ylfkipgy...@dd-b.net>,

David Dyer-Bennet <dd...@dd-b.net> wrote:

> David Friedman <dd...@daviddfriedman.nopsam.com> writes:
>
> > In article <ylfkhawi...@dd-b.net>,
> > David Dyer-Bennet <dd...@dd-b.net> wrote:
> >
> >> >> Well, much of the mantle is permeated with life currently.
> >> >
> >> > No. The mantle is red hot near the top, and even hotter lower down.
> >> > Any carbon compounds would be converted to charcoal. Or to graphite.
> >> > Or to diamond.
> >>
> >> Oops, yeah, wrong term got to the fingers. Layer up from there.
> >> Crust. There we go.
> >
> > More important than the terminology, the layer you are describing, while
> > of some importance to us, makes up a negligible fraction of the earth's
> > mass.
>
> But we're not proposing breaking up the entire earth, either. Won't
> bits blown off by impact events come almost entirely from the crust?

Presumably so.

But I thought Keith's argument was that it would require enormously more
mass than was available to justify the claim he was questioning. The
smaller the fraction of the earth's mass available, the stronger that
argument is.

[David Dyer-Bennet]

David Friedman <dd...@daviddfriedman.nopsam.com> writes:

> In article <ylfkipgy...@dd-b.net>,
> David Dyer-Bennet <dd...@dd-b.net> wrote:
>
>> David Friedman <dd...@daviddfriedman.nopsam.com> writes:
>>
>> > In article <ylfkhawi...@dd-b.net>,
>> > David Dyer-Bennet <dd...@dd-b.net> wrote:
>> >
>> >> >> Well, much of the mantle is permeated with life currently.
>> >> >
>> >> > No. The mantle is red hot near the top, and even hotter lower down.
>> >> > Any carbon compounds would be converted to charcoal. Or to graphite.
>> >> > Or to diamond.
>> >>
>> >> Oops, yeah, wrong term got to the fingers. Layer up from there.
>> >> Crust. There we go.
>> >
>> > More important than the terminology, the layer you are describing, while
>> > of some importance to us, makes up a negligible fraction of the earth's
>> > mass.
>>
>> But we're not proposing breaking up the entire earth, either. Won't
>> bits blown off by impact events come almost entirely from the crust?
>
> Presumably so.
>
> But I thought Keith's argument was that it would require enormously more
> mass than was available to justify the claim he was questioning. The
> smaller the fraction of the earth's mass available, the stronger that
> argument is.

Well, since we know the event *didn't* disiipate a large proportion of
the Earth's mass, we can rule out all those theories. But the parts
ejected, *would* very likely have contained bacteria. Possibly already
roasted, however.

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> But we're not proposing breaking up the entire earth, either. Won't
> bits blown off by impact events come almost entirely from the crust?

Yes. I was underscoring the absurdity of the "thousand rocks"
estimate. Not only would it take the *entire* Earth to get just one
third of just one rock (on average) to the destination, but if you did
destroy the entire Earth, the vast majority of the rocks would of
course be from the lifeless deep interior.

ObSF: _After Worlds Collide_ by Wylie Balmer, in which lots of
artifacts are found on the new planet in the debris from the destroyed
Earth. Even when I read it as a child, I knew that was unreasonable,
since there's so much more inside than near-surface on Earth.

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> All true; but I was referring to gravitational attraction, not to
> initial departure direction.

Gravitational attraction by what? The destination planet? Utterly
negligible unless and until the rock gets very close to it.

> "Keith F. Lynch" <k...@KeithLynch.net> wrote:

>> It gradually slides from very, very unlikely to absurdly unlikely.

>> It's about like walking a mile in a heavy thunderstorm and
>> remaining dry because all the raindrops just happen to miss you.
>> That *could* happen, but it's almost certainly never happened to
>> anyone ever, and it almost certainly never will.

> Or it did, but then the air all went up to the corner of the room and
> they died before they could report the previous unlikely event :-) .

That too can in principle happen, but it's trillions of trillions of
orders of magnitude -- no exaggeration -- more unlikely yet.

Getting back to rocks in space, it's generally recognized as possible
that life spread from Mars to Earth or vice versa in an impact. The
former -- assuming there was life on Mars -- is possible but unlikely.
The latter is almost but not quite completely impossible. And that's
in the old days when Mars was wet, the sun was cooler, and large
impacts were common. Replacing Mars with a destination a million
times further away and much further "uphill" -- well, let's just say
it doesn't improve the odds.

[David Loewe, Jr.]

On Wed, 18 Apr 2012 01:14:40 +0000 (UTC), "Keith F. Lynch"
<k...@KeithLynch.net> wrote:

>David Dyer-Bennet <dd...@dd-b.net> wrote:

>> But we're not proposing breaking up the entire earth, either. Won't
>> bits blown off by impact events come almost entirely from the crust?
>
>Yes. I was underscoring the absurdity of the "thousand rocks"
>estimate. Not only would it take the *entire* Earth to get just one
>third of just one rock (on average) to the destination, but if you did
>destroy the entire Earth, the vast majority of the rocks would of
>course be from the lifeless deep interior.
>
>ObSF: _After Worlds Collide_ by Wylie Balmer,

Philip Wylie and Edwin Balmer.

>in which lots of
>artifacts are found on the new planet in the debris from the destroyed
>Earth. Even when I read it as a child, I knew that was unreasonable,
>since there's so much more inside than near-surface on Earth.

I don't remember this at all. However, I can't find my copy to
corroborate my memory. As far as I can remember, everything they used
was either brought with them or was from the civilization that had
existed on Bronson Beta before that planet was thrown out of its system,
so if there were Earth artifacts, they were not important to the plot of
this classic SF novel.
--
"I'm warning you: I'm very dangerous when I don't know what I'm doing..."
- The Fourth Doctor

[David Dyer-Bennet]

"Keith F. Lynch" <k...@KeithLynch.net> writes:

> David Dyer-Bennet <dd...@dd-b.net> wrote:
>> All true; but I was referring to gravitational attraction, not to
>> initial departure direction.
>
> Gravitational attraction by what? The destination planet? Utterly
> negligible unless and until the rock gets very close to it.

Yes, the destination planet. And a small influence over time can have
big effects.

>> "Keith F. Lynch" <k...@KeithLynch.net> wrote:
>>> It gradually slides from very, very unlikely to absurdly unlikely.
>>> It's about like walking a mile in a heavy thunderstorm and
>>> remaining dry because all the raindrops just happen to miss you.
>>> That *could* happen, but it's almost certainly never happened to
>>> anyone ever, and it almost certainly never will.
>
>> Or it did, but then the air all went up to the corner of the room and
>> they died before they could report the previous unlikely event :-) .
>
> That too can in principle happen, but it's trillions of trillions of
> orders of magnitude -- no exaggeration -- more unlikely yet.

Yes, yes, I know.

> Getting back to rocks in space, it's generally recognized as possible
> that life spread from Mars to Earth or vice versa in an impact. The
> former -- assuming there was life on Mars -- is possible but unlikely.
> The latter is almost but not quite completely impossible. And that's
> in the old days when Mars was wet, the sun was cooler, and large
> impacts were common. Replacing Mars with a destination a million
> times further away and much further "uphill" -- well, let's just say
> it doesn't improve the odds.

Sure, it's unlikely. And there can't have been that many events of the
magnitude being considered, either. Steps in the local evolution of
life are unlikely, but they could happen any year in any tidepool over
billion-year timespans, so they get more opportunities.

[Keith F. Lynch]

David Dyer-Bennet <dd...@dd-b.net> wrote:
> "Keith F. Lynch" <k...@KeithLynch.net> writes:
>> Gravitational attraction by what? The destination planet? Utterly
>> negligible unless and until the rock gets very close to it.

> Yes, the destination planet. And a small influence over time can
> have big effects.

Note that gravity falls off with the square of the distance. Also, to
turn a miss into a hit, it's the *sideways* vector that counts, which
until you're very close is enormously weaker than the forwards vector.

If you're 10 light years from Earth, the midpoint of the proposed 20
light year journey, that's 16 *billion* Earth radii away, so gravity
is down to about 4E-21 Gs, or 4E-20 meters per second per second.
Suppose your trajectory was such that in the absence of gravity you'd
miss Earth by one Earth radius, about 6.4E6 meters. Draw the vector
diagram. Good luck getting it to scale. That's a *very* acute right
triangle. Of the acceleration of 4E-20, one part in sqrt((1.6E10+1)^2
- 1.6E10^2) of it will be sideways. That's about sqrt(3.2E10) or
about 1.8E+5. So about 2.2E-25 meters per second per second sideways.
Over one million years (3E+13 seconds), you'd move just about 100
meters sideways (AT^2/2), out of the 6.4 *million* meters you'd
need to turn a miss into a hit. Of course as you get closer the
acceleration becomes greater, but that shows that any effect light
years away can be neglected.

There is a closed form solution. This weekend I'll try to find the
time to work it out, or at least look it up.

> Sure, it's unlikely. And there can't have been that many events
> of the magnitude being considered, either. Steps in the local
> evolution of life are unlikely, but they could happen any year
> in any tidepool over billion-year timespans, so they get more
> opportunities.

There's a big difference between forwards and backwards likelihoods.
(There's probably a better term for the distinction.) What are your
odds of hitting a tiny bullseye if you throw a dart while blindholded?
Quite good if you paint the bullseye around the dart after it hits!
If you shuffle a deck of cards, what are the chances of it ending up
in perfect order? It's very unlikely, but whatever order it *did* end
up in was a priori equally unlikely.

How likely is it for life to start, per second, per cubic meter of
primeval tidepool? Are there enough seconds in Earth's history and
enough cubic meters in Earth's waters to make it reasonably likely?
Nobody knows. But suppose it's eventually somehow determined that
it's so extraordinarily unlikely that you'd expect it to happen only
once in all the waters on all the planets in the whole universe. Is
it then useful to postulate a mechanism that would get life here if it
started elsewhere? No! Since life is only known here, if it started
only once in the universe, then it started here. There's nothing odd
about our finding ourselves on such a planet, given that we are life
and we'd inevitably -- barring interplanetary travel -- find ourselves
on a planet that life began on. The dart finds itself in the bullseye
that was painted around it after it hit.

In other words, since there's no evidence for extraterrestrial life,
much less extraterrestrial life that shares its genetic code with
Earth life, there's no need for panspermia as an explanation. You
don't need to explain how your fingerprints were found on the gun if
your fingerprints weren't found on the gun.

[Paul Ciszek]

In article <jmfe33$p1s$3...@reader1.panix.com>,

Keith F. Lynch <k...@KeithLynch.net> wrote:
>

>Since there's no selective pressure for intelligence or morality,
>those are not being selected for and are not increasing in the
>population. The strongest selective pressure on our species today
>is probably for contraceptives to stop working.

The simplest form of genetic "resistance" to contraceptives would be
a genetic tendency to be too stupid to use them correctly.

Sure, an actual desire to have children would work better, but that
would be a more complicated feature, more difficult to produce via a
combination of random mutations. It is far more likely to appear as
a social meme.

--
Please reply to: | "We establish no religion in this country, we
pciszek at panix dot com | command no worship, we mandate no belief, nor
Autoreply is disabled | will we ever. Church and state are, and must
| remain, separate." --Ronald Reagan, 10/26/1984

[Paul Ciszek]

In article <jmikht$mbb$2...@reader1.panix.com>,

Keith F. Lynch <k...@KeithLynch.net> wrote:
>
>That's a different meaning of "progressive," one I hope Dawkins makes
>explicit elsewhere in that work. Is it "progressive" for a cave fish
>to lose its eyesight? For a parasitic worm to lose its digestive
>system and rely on its host's? For a man to rape many women rather
>than marrying one, if the former leads to more progeny?

The two are not mutually exclusive. Once the harvest is in, you could
get in a longboat with your pals and raid the folks down south with
later harvest seasons, providing more for your family at home *and*
producing lots of bastards for someone else to raise.

[David Friedman]

In article <jn2s8q$51j$1...@reader1.panix.com>,

nos...@nospam.com (Paul Ciszek) wrote:

> In article <jmfe33$p1s$3...@reader1.panix.com>,
> Keith F. Lynch <k...@KeithLynch.net> wrote:
> >
> >Since there's no selective pressure for intelligence or morality,
> >those are not being selected for and are not increasing in the
> >population. The strongest selective pressure on our species today
> >is probably for contraceptives to stop working.
>
> The simplest form of genetic "resistance" to contraceptives would be
> a genetic tendency to be too stupid to use them correctly.
>
> Sure, an actual desire to have children would work better, but that
> would be a more complicated feature, more difficult to produce via a
> combination of random mutations. It is far more likely to appear as
> a social meme.

On the other hand, if there is a particular form of contraception that's
widely used, such as the pill, there would be evolutionary pressure for
changes that would make it stop working, or work less effectively.

[Paul Ciszek]

In article <jmcqm6$ji2$2...@reader1.panix.com>,

Keith F. Lynch <k...@KeithLynch.net> wrote:

>Paul Ciszek <nos...@nospam.com> wrote:
>> That extraterrestrial life does not exist seems to be a point of
>> doctrite with many fundamentalists.
>
>Who? None that I've ever heard of.

I had the misfortune to fall in love with a Baptist back in college.
As a result I was exposed to far more biblical literalists and
creationists than I care to remember. Their cosmology was functionally,
if not literally, geocentric. The belief in the lack of life elsewhere
was pretty common, including the aforementioned Baptist.

There is a reason that most of the Moon Landing Deniers are religious
fundamentalists of one stripe or another.

[Paul Ciszek]

In article <ddfr-E4D479.2...@news.giganews.com>,

David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
>In article <jn2s8q$51j$1...@reader1.panix.com>,
> nos...@nospam.com (Paul Ciszek) wrote:
>
>> In article <jmfe33$p1s$3...@reader1.panix.com>,
>> Keith F. Lynch <k...@KeithLynch.net> wrote:
>> >
>> >Since there's no selective pressure for intelligence or morality,
>> >those are not being selected for and are not increasing in the
>> >population. The strongest selective pressure on our species today
>> >is probably for contraceptives to stop working.
>>
>> The simplest form of genetic "resistance" to contraceptives would be
>> a genetic tendency to be too stupid to use them correctly.
>>
>> Sure, an actual desire to have children would work better, but that
>> would be a more complicated feature, more difficult to produce via a
>> combination of random mutations. It is far more likely to appear as
>> a social meme.
>
>On the other hand, if there is a particular form of contraception that's
>widely used, such as the pill, there would be evolutionary pressure for
>changes that would make it stop working, or work less effectively.

Stupidity, forgetfulness, and irresponsibility being changes that can
make the pill stop working or work less effectively. And since those
traits clearly already exist, they would in your scenario be favored.

--
Please reply to: | "Evolution is a theory that accounts
pciszek at panix dot com | for variety, not superiority."
Autoreply has been disabled | -- Joan Pontius

[Steve Coltrin]

begin fnord

nos...@nospam.com (Paul Ciszek) writes:

> Sure, an actual desire to have children would work better, but that
> would be a more complicated feature, more difficult to produce via a
> combination of random mutations. It is far more likely to appear as
> a social meme.

I realized a while ago that this seems to have happened in Known Space,
given a) the societal obsession with breeding and b) Niven's penchant for
bullshit evolutionary psychology.

--
Steve Coltrin spco...@omcl.org Google Groups killfiled here
"A group known as the League of Human Dignity helped arrange for Deuel
to be driven to a local livestock scale, where he could be weighed."
- Associated Press

[David Friedman]

In article <jn2tck$51j$5...@reader1.panix.com>,

nos...@nospam.com (Paul Ciszek) wrote:

> In article <ddfr-E4D479.2...@news.giganews.com>,
> David Friedman <dd...@daviddfriedman.nopsam.com> wrote:
> >In article <jn2s8q$51j$1...@reader1.panix.com>,
> > nos...@nospam.com (Paul Ciszek) wrote:
> >
> >> In article <jmfe33$p1s$3...@reader1.panix.com>,
> >> Keith F. Lynch <k...@KeithLynch.net> wrote:
> >> >
> >> >Since there's no selective pressure for intelligence or morality,
> >> >those are not being selected for and are not increasing in the
> >> >population. The strongest selective pressure on our species today
> >> >is probably for contraceptives to stop working.
> >>
> >> The simplest form of genetic "resistance" to contraceptives would be
> >> a genetic tendency to be too stupid to use them correctly.
> >>
> >> Sure, an actual desire to have children would work better, but that
> >> would be a more complicated feature, more difficult to produce via a
> >> combination of random mutations. It is far more likely to appear as
> >> a social meme.
> >
> >On the other hand, if there is a particular form of contraception that's
> >widely used, such as the pill, there would be evolutionary pressure for
> >changes that would make it stop working, or work less effectively.
>
> Stupidity, forgetfulness, and irresponsibility being changes that can
> make the pill stop working or work less effectively. And since those
> traits clearly already exist, they would in your scenario be favored.

Those also have effects working in the other direction, by reducing the
probability that the children produced would survive to adulthood. A
biological "immunity" to the pill wouldn't have that problem.

[James Nicoll]

In article <m2397vh...@kelutral.omcl.org>,

Steve Coltrin <spco...@omcl.org> wrote:
>begin fnord
>nos...@nospam.com (Paul Ciszek) writes:
>
>> Sure, an actual desire to have children would work better, but that
>> would be a more complicated feature, more difficult to produce via a
>> combination of random mutations. It is far more likely to appear as
>> a social meme.
>
>I realized a while ago that this seems to have happened in Known Space,
>given a) the societal obsession with breeding and b) Niven's penchant for
>bullshit evolutionary psychology.
>

Actually, while the early stories have ARM hunting down unlicensed
mothers (the dads seem to get a pass), it's clear from other details
the UN is deliberately maintaining the population at about 18 billion
rather than working to keep it no more than about 18 billion. Left to
themselves the population would decline slightly from year to year
because not all birth rights get used by their original owners.


--
http://www.livejournal.com/users/james_nicoll
http://www.cafepress.com/jdnicoll (For all your "The problem with
defending the English language [...]" T-shirt, cup and tote-bag needs)

[Jette Goldie]

On 23/04/2012 07:38, Paul Ciszek wrote:
> In article<ddfr-E4D479.2...@news.giganews.com>,
> David Friedman<dd...@daviddfriedman.nopsam.com> wrote:
>> In article<jn2s8q$51j$1...@reader1.panix.com>,
>> nos...@nospam.com (Paul Ciszek) wrote:
>>
>>> In article<jmfe33$p1s$3...@reader1.panix.com>,
>>> Keith F. Lynch<k...@KeithLynch.net> wrote:
>>>>
>>>> Since there's no selective pressure for intelligence or morality,
>>>> those are not being selected for and are not increasing in the
>>>> population. The strongest selective pressure on our species today
>>>> is probably for contraceptives to stop working.
>>>
>>> The simplest form of genetic "resistance" to contraceptives would be
>>> a genetic tendency to be too stupid to use them correctly.
>>>
>>> Sure, an actual desire to have children would work better, but that
>>> would be a more complicated feature, more difficult to produce via a
>>> combination of random mutations. It is far more likely to appear as
>>> a social meme.
>>
>> On the other hand, if there is a particular form of contraception that's
>> widely used, such as the pill, there would be evolutionary pressure for
>> changes that would make it stop working, or work less effectively.
>
> Stupidity, forgetfulness, and irresponsibility being changes that can
> make the pill stop working or work less effectively. And since those
> traits clearly already exist, they would in your scenario be favored.
>

Antibiotics and other (prescribed, medical) drugs can also interfere
with the Pill. A bad tummy bug will interefere with the Pill.


--
Jette Goldie
jgold...@btinternet.com

Living in the Future!