RE: Somewhat OT Interesting Question in a survey

From: Paul Grace (paulgrace@lookoutranch.com)
Date: Sun Dec 21 2008 - 03:36:23 UTC

  • Next message: Brad Young: "BY Obs Dec 21"

    I can imagine a well hole from pole to pole.  The gravitational force on a
    ball at the center of the earth is null.  Assuming the well hole is
    structurally impervious, and evacuated, the ball dropped at the north pole
    would fall, accelerating ever more slowly, until it reached zero
    acceleration at the Earth's center, and as it continued to fall toward the
    south pole it would slow, until it reached zero speed at the earth's surface
    at the south pole, whereupon it would fall back into the hole, and continue
    oscillating.  It the hole were not evacuated, friction would cause the ball
    to stop at the earth's center.  If the well were not impervious, it would
    collapse, and the ball would rest at the bottom of the well.
    
    A "deeper" hole could be imagined, if there were a black hole at the center
    of the earth.  The ball would check in, and wouldn't check out.  Until the
    black hole evaporated.
    
    -----Original Message-----
    From: Rodney Austin [mailto:rodcomet@gmail.com] 
    Sent: Saturday, December 20, 2008 19:14
    To: seesat-l@satobs.org
    Subject: Somewhat OT Interesting Question in a survey
    
    Hi All,
             I have just been answering a survey designed to study the
    understanding of astronomical concepts among school children. The
    author of the survey has asked several local 'experts' including
    myself (Ha!) to also do the survey to study the differences etc.
    
    One question was sufficiently curly to cause quite discussion at the
    New Plymouth Astronomical Society last night. Logic and intuition seem
    to break down when studying the ramifications of the question. At
    first glance it is very straight forward.
    
    Question. Imagine that you dropped a ball into a very deep well hole
    (as deep as you can imagine). There is no water in the well.
    What would happen to the ball and why?
    
    I would be most interested to hear your opinions on this one.
    Merry Christmas and Happy New Year to you all.
    Cheers
    Rod Austin
    
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