Re: Principle of Equivalence

['Brent Meeker' via Everything List]

On 7/11/2020 4:29 PM, Alan Grayson wrote:

On Saturday, July 11, 2020 at 5:05:02 PM UTC-6, Brent wrote:



    On 7/11/2020 12:54 AM, Alan Grayson wrote:

    On Tuesday, July 7, 2020 at 10:06:44 PM UTC-6, Alan Grayson wrote:



        On Tuesday, July 7, 2020 at 8:50:50 PM UTC-6, Alan Grayson
        wrote:



            On Tuesday, July 7, 2020 at 8:05:28 PM UTC-6, Bruce wrote:

                On Wed, Jul 1, 2020 at 4:18 PM Alan Grayson
                <agrays...@gmail.com> wrote:

                    How, exactly, is the Principle of Equivalence
                    used by Einstein to develop GR? TIA, AG



                This lecture by Sean Carroll should answer all your
                questions:

                URL: https://wp.me/p2WMeM-3vl

                Bruce


            I'll watch it tonight, but I think I've figured it out;
            specifically, the EP implies space-time is curved by the
            presence of mass/energy (and this is independent of the
            need to express the laws of physics in a coordinate
            independent way via tensors). AG


        Here's my reasoning regarding the EP; if an observer is in a
        box subject to uniform acceleration, a beam of light starting
        on the extreme left side (moving transverse or perpendicular
        to the acceleration vector), will hit a lower point on the
        right side, showing that uniform acceleration results in
        curved paths in space-time. But if this result is identical
        to gravity, locally, it means that curved paths in space-time
        are produced by, or are equivalent to gravity.

    That makes no sense.  You're saying that because curved paths can
    be produced two different ways then they must always be produced
    the second way.

        BUT gravity is only observed in the presence of mass/energy.
        ERGO, the EP implies mass/energy curves space-time. AG

    And that's not even true.  Gravitational waves can propagate thru
    the vacuum.  The Schwarzschild solution is for empty space.  De
    Sitter space is an empty cosmos.

Light can propagate through empty space, but it can't arise from nothing. Same presumably for gravitational waves. AG

Are you going to say the same thing about matter?  electric charge?

Brent

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