On 9/9/2025 10:36 PM, Alan Grayson wrote:


On Tuesday, September 9, 2025 at 11:25:37 PM UTC-6 Brent Meeker wrote:



    On 9/9/2025 9:57 PM, Alan Grayson wrote:


    On Tuesday, September 9, 2025 at 5:18:14 PM UTC-6 Brent Meeker wrote:



        On 9/8/2025 8:45 PM, Alan Grayson wrote:


        On Monday, September 8, 2025 at 9:35:09 PM UTC-6 Brent
        Meeker wrote:



            On 9/8/2025 11:19 AM, Alan Grayson wrote:


            On Monday, September 8, 2025 at 5:06:36 AM UTC-6 John
            Clark wrote:

                On Mon, Sep 8, 2025 at 7:00 AM Alan Grayson
                <[email protected]> wrote:

                    /> I'm not sure the impossibility of absolute
                    simultaneity solves the problem,/

                *
                *
                *Watch the video!If you follow what he does
                step-by-step you will see that he is right. It's
                not difficult. *


            *I'll definitely watch it, very soon, but a-priori the
            impossibility of absolute simultaneity can't solve the
            paradox because it's not its cause. Can you succinctly
            state the cause of the paradox? It's the application of
            time dilation in SR, under the mistaken assumption that
            the twins take symmetric paths; that their situations
            are symmetric. This results in the situation that when
            they meet and compare clock readings, each concludes
            the other is younger. *
            No that's wrong.  The stay at home twin has a clock that
            indicates a longer interval than the traveling twins
            clock.   They agree that the traveling twin is younger.

            Brent


        *Can't you understand English? I was stating the paradox and
        its cause. With an accurate analysis, the traveling twin is
        younger. Also, FWIW, for the traveling twin to return for
        the clock comparison, some acceleration is necessary,
        although it can be minimized if the comparison is done by
        fly-by. a AG *
        But notice that the acceleration is entirely incidental, as
        illustrated by the case in which Red and Blue each
        accelerates the same amount.  IT'S JUST GEOMETRY.  ONE PATH
        IS LONGER THAN THE OTHER.


    *In the original statement of the "paradox', the traveling twin
    must accelerate to return so the clocks can be compared. Please
    explain how this can happen without acceleration. *
    I've shown two different ways without acceleration and I've also
    shown the paradox with equal accelerations by both twins.  Why
    can't you just accept that it's geometry; that one path is longer
    than the other.

*
*
*If both twins are accelerating, then you've redefined the TP. *
No.  But Blue does not accelerate while Red travels out and back.*

*
*If you have two paths in spacetime, starting at the same point and ending at the same point, or at a  different point, how can you tell which is longer? AG *
These are paths in /spacetime/.  They start and end at the same /event/, a point in 4-space.  The obvious way to tell which is longer in proper time is to carry an ideal clock along the two paths and compare the measured intervals.  You could also measure the space distance X along the paths and and compute proper time S=\sqrt{T^2 - X^2}  where T is the coordinate time difference (in the same reference frame you measured distance).

Brent

    *You seem to defying basic physics if this is your claim. I don't
    deny that the original problem can be restated in a way which
    avoids acceleration, and IMO this is what you've done. *
    But I've done more than that.  I've done it while maintaining
    exactly the same paradox.

    Brent

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