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Re: fHuman vs. natural influences on the environment



In article <lkn2zuunvo.fsf@sandy.ast.cam.ac.uk> steinn@sandy.ast.cam.ac.uk (Steinn Sigurdsson) writes:

 In article <2bnLmKAOsMFyEweQ@wandana.demon.co.uk> Jim Barr <JimBarr@wandana.demon.co.uk> writes:
 
    Several years ago, at a symposium for astrophysicists held in London, an
    experiment was carried out.  All the delegates were asked to calculate
    how much energy it would take to bring one stationary electron from a
    point in deep space ( but near a KNOWN stellar object) and bring it to
    rest on the surface of the earth.
 
    They would allow for mass and movement of all *major* solar objects but
    not asteroids or deep space objects apart from the one mentioned above.
 
    They were all *capable* of  doing the sums and several of them did so.
    The unamazing fact was that the *answers* that these scientists came up
    with differed by as much as 13 orders of magnitude.
 
 I don't believe you. Please provide a citation.
 
I don't understand.  

It would seem to me that the energy required to move the electron
depends entirely on the electric potential difference between the
point in space and the surface of the earth.  I would expect that to
be entirely unknown.  I doubt that the potential differences are known
even within the solar system and may not even be constant over time.
It seems to me from what I have read that a lot is known about the
potential difference between the ionosphere and the earth's surface,
but I don't know if it is constant geographically or in time.
-- 
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.
http://www-formal.stanford.edu/jmc/progress/



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