Re: [ATM] Dumb Question: how to measure a...

[Dan Newman <dan.newman+atm@mtbaldy.us>]

On 30 May 2006 , at 3:14 PM, Dale Eason wrote:

>
> The definition of a circle is all points equal radius
> from a point.  Thus any diameter should be the same
> within a tolerance you pick and can measure.
>
> I know of no other geometry that has that attribute.
> Can you give me one?

While the author may have had something else in mind, he may have
been referring to curves of constant width.  If I take my
mic or calipers to something and measure it with my eyes
closed I might conclude after three measurements that it is
circular -- each measurement between opposite, parallel tangent
lines yielded the same perpendicular distance between those
parallel tangent lines -- when indeed it's a Reuleaux triangle (aka,
a Wankle rotor from a Mazda).  But then I don't do these measurements
blind folded....

See, for example,  http://en.wikipedia.org/wiki/ 
Curve_of_constant_width .

Regards,
Dan
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