Re: navigation riddle

[Bruce McKay <brumac@BIGPOND.NET.AU>]

As I live in the southern hemisphere, I will ignore the north pole
and say there are in fact many points in the southern hemisphere that
meet the requirements of Point A.

Bruce McKay
Sydney
Australia

> Since phys-l has been somewhat listless lately, here
> is a riddle:
>
> Dr. Livingstone starts out at a place which we call
> Point A.  He then undertakes a journey consisting
> of three legs:
>   -- he travels precisely southward for one mile;
>   -- then he turns and travels precisely eastward
>      for one mile;
>   -- then he turns and travels precisely northward
>      for one mile.
> He discovers that as a result of this journey, he
> has returned to Point A.
>
> Note: He travels by airship, at an appropriate constant
> altitude, so you don't need to worry about obstructions
> or other nonidealities.
>
> The questions are:
>
> 1) Where is Point A?
> 2) Are you sure?  How do you know?
>
> ===========
>
> Usual ground-rules:  The right answer depends on
> understanding the physics of the situation.  This may
> require some outside-the-box thinking.  Everything
> I've said is intended to be true and helpful.  I expect
> a strong consensus as to the correctness of the answer.