On 12/3/2025 4:10 PM, Alan Grayson wrote:


On Wednesday, December 3, 2025 at 2:37:35 PM UTC-7 Brent Meeker wrote:



    On 12/3/2025 3:00 AM, Alan Grayson wrote:


    On Tuesday, December 2, 2025 at 3:51:45 PM UTC-7 Brent Meeker wrote:



        On 12/2/2025 1:24 AM, Alan Grayson wrote:


        On Monday, December 1, 2025 at 10:37:16 PM UTC-7 Russell
        Standish wrote:

            On Mon, Dec 01, 2025 at 08:07:14PM -0800, Alan Grayson
            wrote:
            >
            >
            > On Monday, December 1, 2025 at 3:46:40 PM UTC-7
            Russell Standish wrote:
            >
            > On Sat, Nov 29, 2025 at 11:13:05PM -0800, Alan Grayson
            wrote:
            > >
            > >
            > > On Friday, November 28, 2025 at 3:26:03 PM UTC-7
            Russell Standish wrote:
            > >
            > > Sorry - I can't make sense of your question.
            > >
            > >
            > > The Axiom of Choice (AoC) asserts that given an
            uncountable set of sets,
            > each
            > > one being
            > > uncountable, there is a set composed of one element
            of each set of the
            > > uncountable set
            > > of sets. The AoC doesn't tell us how such a set is
            constructed, only that
            > we
            > > can assume it
            > > exists. So, in chosing an origin for the coordinate
            system for a plane
            > say, we
            > > have to apply
            > > the AoC for a single uncountable set, the plane. But
            there's no way to
            > > construct it. Does
            > > this make sense? AG
            > >
            >
            > I don't see the axiom of choice has much bearing here.
            To choose an
            > origin, we simply need to choose one point from a
            single uncountable
            > set of points. We label finite sets of points all the
            time - geometry
            > would be impossible otherwise - consider triangles
            with vertices
            > labelled A,B and C.
            >
            >
            > You write "we simply need to choose one point from a
            single uncountable set
            > points", but how exactly can we do that! That's the
            issue, the construction of
            > the coordinate system. In fact, there's no credible
            procedure for doing that,
            > so
            > we need the AoC to assert that it can be done. IMO,
            this is an esoteric issue.
            > For example, we can't just assert we can use the
            number ZERO to construct
            > the real line, since with ZERO we have, in effect, a
            coordinate system.AG
            >

            Rubbish - it is not controversial to pick a set of
            points from a
            finite set of uncountable sets. As I said, we've been
            doing that since
            building ziggurats on the Mesopotamian plain. AoC is only
            controversial when it comes to uncountable sets of
            uncountable sets.


        *It's subtle, maybe too subtle for you to see its relevance.
        You're imaginIng throwing*
        *a dart at a flat piece of paper, but that falls far short
        of a viable/construction /of a *
        *coordinate system on a plane. You can imagine it being done
        and that's the extent*
        *of your proof. AG *
        A coordinate system is anything that supplies a unique set of
        numbers to label every point such that the numbers are
        continuous.  I think you have and exaggerated idea of what
        needs to be constructed.

        Brent


    Presumably, you have a more rigorous approach, say for R^2, by
    imagining a plane, or using a piece of flat paper, and throwing a
    dart at it to define the origin.   AG
    You can choose any point and make it the origin, which just means
    you give it the label (0,0).  No physics can depend on the choice
    of origin or the coordinate system.


Of course, but how can one find any point on a thing which is ill-defined in the first place?
You don't /find /a point on a thing.  The coordinate system and the origin are in mathematics, not in reality.  That's why they can be arbitrary.  You just postulate a coordinate system and say I'll call the center of the Earth the origin and z-axis to be the line toward Polaris.  No one can say, "That's wrong." because it's arbitrary.

Brent
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