Proof: Earth is Round

Date: 8/7/96 at 16:7:35
From: Anonymous
Subject: Proof: Earth is Round

I was wondering if you could settle a bet.  My friend, who is a 
philosophy major, says the earth is flat.  I say it's round.  He's 
telling me the premises for determining that the earth is round are 
false.  How can I explain, using math (he will agree with Pi = 3.14, 
simple trig and geometry, and standard definitions of distance) that:

    1) The earth has a definite curvature (sp)
    2) One can determine a general position on earth fixing with 
		stellar points
    3) The circumference of the earth ( In km )
    4) And prove that the earth is round

I remember from high-school trig that it is possible (using a 
sextant) but if you could provide some general theories, I would 
appreciate it.

Also within those parameters I can't use items like pictures because 
they can be forged.

Yes, he is a candidate for the flat earth society.
Thanks.

Nathan Glondys

Date: 8/9/96 at 11:59:55
From: Doctor Ceeks
Subject: Re: Proof: Earth is Round

Hi,

You cannot prove that the Earth is round or flat using mathematics.

Mathematics does not answer questions about the way the world is.
Your question is a physics question.

While it is true that much physics uses mathematics, and it is quite
wonderful that this is so, nevertheless, mathematics is not really
concerned with the physical world.  This has the happy corollary that
mathematics is not bound by physical laws.

In any case, to address your question, we can ask what is meant when
one asserts that the "Earth is flat," or the "Earth is round."  Both
statements are a model of reality.  Demanding to know which of the two
is really true does begin to border on the philosophical, but in terms 
of practicality, one of the two models may serve to promote 
understanding of numerous facts... such as that Columbus never fell 
off an edge of the world.

If you can provide a simple principle which explains many things,
you make it easier for people to do things.  For example, no one will 
ever really know if there really is a gravitational inverse square 
law, but it has proven a wonderful model which enabled people to get
Neil Armstrong to the moon.

Besides, on closer inspection, both models of the Earth are likely 
false, as anyone who's tried to hike up a mountain can testify.

-Doctor Ceeks,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/