On 9/13/2024 7:10 PM, Alan Grayson wrote:


On Friday, September 13, 2024 at 4:03:45 PM UTC-6 Brent Meeker wrote:




    On 9/13/2024 4:56 AM, Alan Grayson wrote:


    On Friday, September 13, 2024 at 4:06:49 AM UTC-6 Alan Grayson wrote:

        On Thursday, September 12, 2024 at 11:07:49 PM UTC-6 Alan
        Grayson wrote:

            On Thursday, September 12, 2024 at 11:00:21 PM UTC-6
            Brent Meeker wrote:




                On 9/12/2024 9:21 PM, Alan Grayson wrote:


                On Thursday, September 12, 2024 at 3:55:45 AM UTC-6
                Quentin Anciaux wrote:



                    Le jeu. 12 sept. 2024, 11:53, Alan Grayson
                    <[email protected]> a écrit :



                        On Thursday, September 12, 2024 at
                        2:40:56 AM UTC-6 Quentin Anciaux wrote:

                            I just gave you a full proof that as
                            long as the expansion is uniform and
                            expansion rate > 0, then it follows
                            objects will sooner or later recess from
                            each other at speed > c.


                        What was the justification for the geometric
                        progression? I made no such assumption in my
                        "proof".


                    As explained multiple times and in the quote you
                    made, expansion is uniform and happens at every
                    point in space.


                What bothers me about your method is that
                you*assume* a geometric increase in the separation
                distance, when, IMO, that's the variable that must
                be calculated (which I did). So no matter how many
                times you affirm your proof as valid, I can't agree. AG

                You didn't calculate the expansion parameter, which
                is the Hubble constant. It's an observed value.

                Brent


            Why must I do that, when I just want to show that
            eventually the recessional velocity exceeds c? Also, I
            don't see why theta is fixed, when the end of the arc
            defines the position of the receding galaxy. AG


        Now I am not sure I proved the recessional velocity is
        greater than c, after some time has passed. If the sphere is
        expanding, then the distance between any two fixed points on
        the sphere will increase as time passes. But that was obvious
        due to the expansion. What's wrong, if anything? AG


    Now I see the light. We've been struggling to prove that a
    receding galaxy will fall out of view if the universe is
    expanding, but all the so-called "proofs" fail, but for different
    reasons. What Quentin offers is not a proof. He's just repeating
    a result done by someone else,*using mathematics*, which he
    believes (and might be true). Brent is mistaken in his apparent
    belief that the proof of concept requires appeal to Hubble's law.
    This is also mistaken IMO since the result to be proven depends
    *exclusively* on the *geometry *of an expanding sphere. Finally,
    my proof also fails, since it's obvious that the arclength, s, 
    between two galaxies on an expanding  sphere, will obviously
    increase as the sphere expands. That is, ds/dt will obviously be
    positive since the arclength is increasing. IOW, a constantly
    increasing arclength s, assuming a uniformly expanding sphere,
    necessarily yields ds/dt > 0, but it does NOT demonstrate that
    the velocity of the receding galaxy eventually increases to be
    greater than c. When I have the energy, I will calculate the
    *second time derivative* of the arclength, s, hopefully to
    demonstrate, that for a uniformly expanding sphere, the *four*
    terms of the second derivative of s, imply a*positive
    acceleration*. This will establish that eventually the receding
    galaxy will pass out of view for the observer on the assumed
    stationary galaxy. Comments welcome. AG
    It's already proven that ds/dt=ks  => s=j*exp(kt) where k with
    dimensions of 1/time and j is an arbitrary constant of integration
    with the same dimensions as s.  Going to second derivatives won't
    gain any more.

    Brent


We have different objectives. Your equation represents Hubble's law, but what I want to show is that Hubble's law is the inherent result of the geometry of an expanding sphere. So I believe going to the second derivative will demonstrate this. BTW, what's your argument that theta is a constant? AG
Notice I didn't mention Hubble's law and avoided using H.  I deliberately used j and k for undetermined constants.

Theta's constant under the assumption that it's the angle between two points that at FIXED on the expanding surface.

Brent

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