Re: Riemann geometry, chicken or the egg?

On 26 Oct 2006 16:40:27 GMT, israel@xxxxxxxxxxx (Robert Israel) wrote:

In article <7tj1k2h3iemc5m7iqnq8gn4lch1uft1gjk@xxxxxxx>,
bootlace <anonymous@xxxxxxxxxx> wrote:
On Thu, 26 Oct 2006 03:30:00 GMT, Gerry Myerson
<gerry@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

I believe that doing geometry without an eye to physics goes back
to ancient Greece. Conic sections were studied pretty much for
their own sake.

The motion of planets and asteroids were available to the greeks and
it seems logical they might have wondered how you could describe an
ellipse.

Asteroids???

Asteroids and meteors streaking across the heavens were noted by the
Greeks and Chinese . An observation such as this might beg the
question why does this thing appear to be racing toward the sun? Of
course it would take a second sighting of an asteroid or meteor
streaking away from the sun before anyone could conceive of an
elliptical orbit.

The inspiration for experimenting with conical sections may have been
something as simple as slicing a carrot who knows?


The Greeks knew seven planets (Sun, Moon, Mercury, Venus, Mars,
Jupiter, Saturn), but not asteroids. Some Greeks did have a
heliocentric system, but the idea that the orbits were ellipses
seems not to have occurred to anybody before Kepler.

Robert Israel israel@xxxxxxxxxxx
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia Vancouver, BC, Canada

.

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