From: schinder@leprss.gsfc.nasa.gov (Paul J. Schinder)
Subject: Re: Followup to Schinder Re: Creative speculation
Reply-To: schinder@leprss.gsfc.nasa.gov
Organization: Goddard Space Flight Center
Date: Tue, 25 Aug 1992 20:29:44 GMT

In <9208250301.AA06973@neptune.gsfc.nasa.gov> jgacker@neptune.gsfc.nasa.gov (James G. Acker) writes:


>	Once again I apologize for the difficulty of replying directly.
>I'm trying to fix it.

>	But, regarding points raised:


>	2:  ...favoring stargazing.   Not that primitive peoples 
>wouldn't look at the sky, but they put a lot of effort into sophisticated
>"observatories" which acted as eclipse predictors as well as solstice
>indicators.  Seasons were obviously harvest- or hurricane-relevant, but
>the eclipses (and presumably planetary motions) forced a more strategic 
>analysis.
>	Now I remember that the Mayan observatories were capable eclipse
>predictors, but this could be a faulty memory.  How far back do 
>eclipse prediction or eclipse records go?

Yeah, I think Mayans were capable of predicting eclipses, as were (I
believe) Greeks and maybe Babylonians and Egyptians.  But I don't see
what this has to do with life on earth and/or evolution.  I can't
offhand (maybe the biologists know different) think of any reason why
life wouldn't be possible without a large moon.  And remember that the
current apparent size of the moon is fortuitous; it's moving out due
to tidal interactions with the earth, and if I remember correctly is
roughly a third of the way farther out than it was several billion
years ago.  Annular eclipses are a fairly recent phenomenon.

>	3:  I said "...abiogenesis...an event which is so common that it can 
>only be shown to have possibly occurred on 1 celestial body... (out of 
>billions)."
>	Since we're working from a limited data set, I was ironically
>mocking our lack of knowledge or ability to know how common or uncommon
>such an event is.  The odds, given first-hand evidence, are laughably 
>small (as others have noted).  With a greater sample size, the odds might 
>obviously improve.

WHOA.  That's a tremendous leap to take.  Since we don't know enough
about the process, and our first hand evidence is extremely sparse,
I'd take any computation of the "odds" as mere hand waving in the
dark.  For all we know, the universe is lousy with life, and it may
just be deficient in the kind of life we can detect at interstellar
distances (or we just may not know what to look for).

>Finding life anywhere else effectively doubles the
>occurrence rate and cuts the odds in half (finding life anywhere else would
>actually make it likely that it's EVERYWHERE in the Universe -- and it
>would be enormous fun if we found even a microbe in Jupiter's fertile
>atmosphere.

Oh, yeah, it would be.  I wonder if we know what to look for?  (For
example, the presence of free oxygen in an atmosphere is quite
unusual, and is usually said to be a dead giveaway that life exists on
the earth, but given that clever grad students can usually come up
with an explanation for anything, I wonder if we could come up with
some "natural" explanation for it?)

>	5:  Re: Collision frequency:  Sure they happen, fortunately for us
>or we might be sophisticated trilobites.  The key is, they are _random_
>events.  Size of impacting body, site (limestone vaporization may have
>aided the K-T event), and resulting climatic effects are all variable.
>Why didn't the Earth get hit so hard it split up?  It appears fortuitous
>for the eventual emergence of humanity that they did happen.

Ahh, that I suppose depends on solar system formation theory.  I know
very little about it, but my vague memory is they can show that within
a hundred million years or so everything is in a few isolated big
things with the leftovers too small to cause any great damage (of the
planet splitting kind) to the big guys.

>	4:  Relevance of moon formation and apparent radius = apparent
>solar radius:  _Any other size_ would not have allowed the spectacular 
>nature of the solar eclipse.  Why didn't Venus get the perfect-sized 
>Moon?  Or Mars?  No, the lucky planet which came equipped with 
>observers to appreciate it was this one.  The serendipitous improbability
>of life + eclipse has to be noted.  We were lucky!

But eclipses are not necessary for life, just a pretty tourist
attractions.  Why weren't we lucky enough to get something really
spectacular like planetary rings :-)

>	Pluto and Charon are another "double planet".  But if the size
>ratio was the same between Earth and Moon, we'd get an eclipse every 
>orbit.  I just like the high odds against it.

No, because the plane of the moon's orbit isn't in the ecliptic.
That's why we *don't* see an eclipse every lunar orbit.  I presume that
Charon's orbit around Pluto is not in the ecliptic either, because it
has just recently been occulting Pluto as seen from the earth.

>	6:  The bold lipid globule -- I am sorry, you're right.
>What I should have said:  This all happened to (or nearby) the one
>planet in the entire Universe where it is possible to surmise that a 
>bold lipid globule... (started making copies).  We can't be certain 
>that the proper environment conducive to emboldening other lipid 
>globules exists anywhere else -- though we can speculate that it does,
>and I'd like to think it does.  Maybe they need help?  (2010)

Maybe, but we don't know that the "helper" hasn't helped often, and in
many places.

>	7:  What are the odds?

>	Regarding dice rolls and the weak anthropic principle:  If the 
>odds against a sequence resulting in US are small, then _RANDOM CHANCE_
>had a lot of influence on the evolutionary sequence progressing to US.
>Though evolution is NOT, repeat, NOT random chance, it would seem that
>the sequence of events leading to the emergence of mankind (and the
>development of the current species mix as well) was somewhat random
>chance, i.e. if the big rocks had hit during the Carboniferous and not 
>the Permian, the mix might have been completely different.

Sure.  Gould emphasises this many times.  Start the earth from the
first primitive life over and over again, and each time you'd wind up
with a unique mix of completely different species.

>	Hmmm... neat idea:  a sci-fi "discussion" with another intelligence
>where their planetary history didn't include all this catastrophism.

If such a planet exists :-)

>	Jim Acker
>	jgacker@neptune.gsfc.nasa.gov
--
--------
Paul J. Schinder
NASA Goddard Space Flight Center
schinder@leprss.gsfc.nasa.gov