On 11/7/2019 4:06 PM, Alan Grayson wrote:


On Thursday, November 7, 2019 at 11:41:11 AM UTC-7, Brent wrote:


    On 11/6/2019 10:31 PM, Alan Grayson wrote:
    On Wednesday, November 6, 2019 at 11:20:23 PM UTC-7, Brent wrote:


        On 11/6/2019 9:00 PM, Alan Grayson wrote:

        On Wednesday, November 6, 2019 at 7:17:21 PM UTC-7, Brent
        wrote:



            On 11/6/2019 4:44 PM, Alan Grayson wrote:


            On Wednesday, November 6, 2019 at 3:46:54 PM UTC-7,
            Brent wrote:



                On 11/6/2019 12:05 AM, Alan Grayson wrote:


                On Tuesday, November 5, 2019 at 10:23:58 PM UTC-7,
                Brent wrote:



                    On 11/5/2019 9:09 PM, Alan Grayson wrote:

                        Crossing the horizon is a nonevent for
                        the most part. If you try to accelerate
                        so you hover just above it the time
                        dilation and that you are in an extreme
                        Rindler wedge will mean you are subjected
                        to a torrent of radiation. In principle a
                        probe could accelerate to 10^{53}m/s^2
                        and hover a Planck unit distance above
                        the horizon. You would be at the
                        stretched horizon. This would be almost a
                        sort of singular event. On the other hand
                        if you fall on an inertial frame inwards
                        there is nothing unusual at the horizon.

                        LC


                    Do you mean that clock rates continue to slow
                    as an observer approaches the event horizon;
                    then the clock stops when crossing, or on the
                    event horizon; and after crossing the clock
                    resumes its forward rate? AG

                    He means the infalling clock doesn't slow down
                    at all. Whenever you see the word "clock" in a
                    discussion of relativity it refers to an
                    /*ideal clock*/.  It runs perfectly and never
                    speeds up or slows down.  It's called
                    /*relativity*/ theory because observers
                    /*moving relative*/ to the clock /*measure
                    it*/ to run slower or faster than their
                    (ideal) clock.

                    Brent


                I see. So if for the infalling observer, his clock
                seems to be running "normally", but for some
                stationary observer, say above the event horizon,
                the infalling clock appears to running
                progressively slower as it falls below the EH,
                even if it can't be observed or measured.
                According to GR, is there any depth below the
                event horizon where the infalling clock
                theoretically stops?

                I just explained that */clocks never slow/* in
                relativity examples.  So now you ask if there's a
                place they stop??

                Brent


            I know, but that's not what I asked. Again, the
            infalling clock is measured as running slower than a
            stationary clock above the EH. As the infalling clock
            goes deeper into the BH, won't its theoretical rate
            continue to decrease as compared to the reference clock
            above the EH? How slow can it get? AG

            It /*appears*/ (if the observer at infinity could see
            the extreme red shift) to /*asymptotically approach
            stopped */as it approaches the event horizon.  This is
            because the photons take longer and longer to climb out
            because they have to traverse more and more spacetime.

            Brent


        I'm referring to two clocks; one at finite distance above
        the EH, and other infalling. Doesn't the infalling clock
        seem to run progressively slower from the POV of the other
        clock, as it falls lower and lower? AG

        I appears to run slower as seen by the distant observer.

        Brent


    As it goes deeper and deeper into the BH, does the clock ever
    appear to STOP? AG

    It doesn't appear at all when it passes the event horizon. It
    appears to stop as it approaches the event horizon.

    Brent


I know it can't be observed as it falls through the EH. That's why I referred to clock "readings" after falling through as "theoretical".

Well it doesn't make much sense to call observations theoretical when it's the theory that says they can't be observed.

On the other hand, LC says falling through the EH is a non-event, as if the infalling clock behaves as we expect based on a clock entering a region of strong gravitational field. But let's say the clock appears to stop as it approaches the EH, which is what I thought. How do you reconcile this prediction, which is certainly weird? AG

Reconcile it with what?  It's a consequence of the metric which is derived from Einstein's equations.  It's not as if it's some unexplained observation.  It's not an observation at all.  It's a theoretical prediction.

Brent

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