From: u108502@beta.lanl.gov (Andrew Poutiatine)
Subject: Re: averting doom
Organization: Los Alamos National Laboratory
Distribution: na
Date: Wed, 6 Jan 1993 19:56:17 GMT

In article <1993Jan6.122355.1@stsci.edu> gawne@stsci.edu writes:
>In article <1993Jan6.155212.25052@newshost.lanl.gov>, 
>u108502@beta.lanl.gov (Andrew Poutiatine) writes:
>
>> In article <1992Dec30.161445.12236@unocal.com> stgprao@st.unocal.COM 
>> (Richard Ottolini) writes:
>>>In article <JMC.92Dec29211051@SAIL.Stanford.EDU> jmc@cs.Stanford.EDU writes:
>>>>from a U.P. story
>>>>
>>>>	     WASHINGTON (UPI) -- Life on Earth as we know it will
>>>>     come to an end in 1,500 million years and the planet will
>>>>     look more like its dusty, volcanic sister Venus in 2,500
>>>>     million years, scientists said Wednesday.
>>>
>>>If we can't model the weather more than 5 days in advance nor agree on
>>>climate prediction in 50 years, who would have any confidence in this
>>>speculation?
>> 
>> I believe the above prediction is based not on earth climate and weather
>> considerations (for which I must agree predictions of more than a few days
>> are not very dependable), but rather on the evolution of the sun.
>> 
>> I am not an astronomer, but as I recall, theory predicts that stars of our
>> sun's size go through a stage in their evolution at the end of their lives
>> when they become hotter and expand.  It is this, I believe, that would
>> parch the earth, killing life "as we know it."
>
>Our understanding of the Sun is that it won't be at "the end of its life" for
>another 4.5 or so *billion* years.  The news article  refers to predictions of
>things to come in 1.5 to 2.5 billion years, when the Sun should still be a main
>sequence star.
>
>Any star will change slowly during its main sequence lifetime, and in the case
>of the Sun and sunlike stars this means becoming slightly hotter and more 
>luminous.  The prediction quoted above seems to be saying that this part
>of the Sun's main sequence evolution will be sufficient to raise Earth's 
>temperature to the point Earth becomes unable to support life.  While I've
>no wish to dispute this claim (for now), it has nothing to do with the Sun's
>predicted evolution into a red giant star after it leaves the main sequence
>"at the end of its life".
>
>-Bill Gawne,  Space Telescope Science Institute
  
Bill, I'm glad to see you have simply agreed with me.  I did not say that
the sun would become a red giant by this point, only that it would become
hotter and grow, and the point I made was only that earth's drying up would
be due to our sun's evolution, not to long range terrestrial climate change,
although the former obviously causes the latter. 

I said nothing about "the sun's predicted evolution into a red giant," that
was you.  As I understand it, the earth is about 5 billion years old or
so, and if we assume the sun was born about the same time as the earth, then
I am calling "the end of it's (the sun's) life " to be 79% of its life
span. If you wish to define "the end of it's life" differently, go right
ahead, just don't argue semantics under the guise of astronomy.

Please take a moment to reread my post, it is above.  I think upon more
careful examination you will see that you have simply (and in more detail
no less) restated my point.

-AIP,  LANL

From: tonya@hpldsla.sid.hp.com (Tony Arnerich)
Date: Fri, 8 Jan 1993 21:18:32 GMT
Subject: Re: are fixed focus binoc's any good for astronomy??
Organization: HP Scientific Instruments Division - Palo Alto, CA