• Re: Experiments on the validity of Relativity

    From Tom Roberts@21:1/5 to Luigi Fortunati on Thu May 16 07:24:08 2024
    On 5/13/24 1:58 AM, Luigi Fortunati wrote:
    When there is an experiment that proves Einstein right, the whole
    world is ready to praise him and his theories (and rightly so).
    However, it is not right that, when an experiment proves Einstein
    wrong, no one admits it and no one talks about it.

    This last is just plain wrong. Any REAL experiment that refuted either
    SR or GR would be GREAT NEWS and the experimenters would win praise and accolades. But they must be real experiments within the domain of
    applicability of the theory, and statistically inconsistent with its predictions. To date no such experiments have ever been published --
    your allegations here are just drivel: they are not real experiments,
    and they indicate that YOU do not understand General Relativity, because
    your claims are based upon a PUN on the word "acceleration".

    Einstein says that bodies in free fall are at rest and that the man
    inside the falling elevator experiences no forces or accelerations.

    No. This is A LOT more subtle. So much so that this claim is just plain
    wrong. You MUST learn about the actual theory before you can have any
    hope of refuting it. All you have done here is shown that your personal misconceptions are inconsistent with each other -- useless.

    [...] two massive bodies (which fall gravitationally and freely
    towards each other) *accelerate* both in the reference of one and
    both in that of the other.

    Sure. This does not refute GR, because of your confusion between
    coordinate acceleration and proper acceleration. These two bodies have
    zero proper acceleration, and nonzero coordinate acceleration. The
    equations (and predictions) of GR are necessarily coordinate
    independent, and basically say nothing at all about coordinate
    acceleration, because one can choose any coordinate system. In the
    absence of forces on an object, GR predicts it has zero proper
    acceleration (while its coordinate acceleration can be anything,
    depending on the coordinates used). In GR, gravitation is an aspect of
    the geometry of spacetime, not a force.

    [Note to experts: there are missing caveats and conditions
    here, but they are irrelevant to Fortunati's basic problem.]

    [... other claims showing further ignorance of GR]

    As I have repeatedly told you, you MUST get a good textbook and STUDY
    physics. Start with classical mechanics, and be sure you have mastered
    it before attempting GR. Better would be taking physics courses at a
    local college or university. Posting dubious claims in a newsgroup is a TERRIBLE approach and will never teach you much physics. There are no shortcuts.

    If body A falls towards body B, body B also falls towards body A. If
    body A accelerates towards body B, body B also accelerates towards
    body A. And these two mutual accelerations never disappear, whatever
    the reference from which we measure them! They are real accelerations generated by real forces.

    Not in GR. GO STUDY and stop wasting your time on nonsense. You do NOT
    have enough knowledge to just "think this through" on your own.

    Tom Roberts

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  • From Jonathan Thornburg [remove -color t@21:1/5 to Luigi Fortunati on Wed Jun 5 07:10:25 2024
    Luigi Fortunati <fortunati.luigi@gmail.com> wrote:
    This is what happens to accelerometer 1 in my animation https://www.geogebra.org/classic/vtvnm8uv where you don't notice the contraction and stretching of the springs just because the variations
    are too small to be visible.

    But just increase the force of gravity to realize that it doesn't show
    zero acceleration at all.

    Look what happens to accelerometer 2 which is also in free fall in a gravitational field: does it seem to show zero acceleration?

    Your animation shows the accelerometers placed in an ambient gravitational which varies significantly across the dimensions of the accelerometer.
    We don't expect an accelerometer to work properly in such a situation.

    The definition of an "ideal" accelerometer includes (among other
    conditions) measuring acceleration-relative-to-free-fall at a *point*,
    i.e., it assumes that tidal fields are negligable, i.e., it assumes that
    the accelerometer is small compared to the scale of variation of any
    ambient gravitatonal fields. Your accelerometer #2 violates this
    assumption.

    --
    -- "Jonathan Thornburg [remove -color to reply]" <dr.j.thornburg@gmail-pink.com>
    currently on the west coast of Canada
    "The 'S' in 'IoT' stands for 'Security'."
    -- commenter on /Ars Technica/, 2024-05-16

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