Re: Experiments on the validity of Relativity

Il 19/05/2024 22:49, Luigi Fortunati ha scritto:

[[Mod. note --
*Coordinate* acceleration is indeed "the variation of velocity".
 
But, *proper* acceleration is something different:  An observer's
*proper* acceleration is defined as the acceleration measured by an
(ideal) accelerometer she carries with her. 

 > ...

-- jt]]

Relativity is wrong to trust the accelerometer.

In my animation https://www.geogebra.org/m/r9zk9smz there are two
accelerometers that accelerate in the *same* way but the first one says
that the acceleration is present (the EK spring contracts and the LM
spring contracts lengthens) and the second says that it is not there
(the springs VR and SW keep their length unchanged at rest).

This shows that the accelerometer (despite its name) does not measure
acceleration at all but measures something else because only a *couple*
of non-concordant forces can compress or stretch the springs and not an
acceleration.

The difference between accelerometer 1 and 2 lies in the point of
application of the external force.

In accelerometer 1 the red external force F acts against a single
surface point (E) as happens in the push of a hand, while in
accelerometer 2 it is divided into an endless number of tiny equal
forces that act individually on each single particle (whether internal
or peripheral), as happens in the case of gravity and electromagnetism.

In both cases, the external force generates the *same* acceleration of
the accelerometer, however, in the first case the accelerometer 1
measures the acceleration, while in the second case the accelerometer 2
says that the acceleration is not present.

Why?

Luigi Fortunati


[[Mod. note --

Why would you expect accelerometer #2 to register any acceleration?

I referred to an "(ideal) accelerometer".  "Ideal" includes that
non-gravitational external forces are applied only to the outer case,
not the inner "proof mass".  Accelerometer #1 satisfies this condition,
but accelerometer #2 doesn't.

As you've described the situation, there are two possble cases for
what's going on with accelerometer $#2:
(a) The "external forces" are really a gravitational field.  In this
    case accelerometer #2 is in free-fall, and having it read
    "zero acceleration" is just what we expect -- by virtue of the
    equivalence principle, no local accelerometer can detect a
    uniform gravitational field, so an accelerometer in free-fall
    should indeed read "zero acceleration".
(b) There are no gravitational fields around, but there's an ambient
    magnetic field and the accelerometer's intern "proof mass" is
    magnetic (e.g., iron/steel) so that the magnetic field is applying
    a force to the proof mass.  In this case the accelerometer is being
    misused (and we shouldn't pay any attention to its readings): it's
    design is such that it doesn't properly measure accelerations when
    there's an ambient magnetic field, and we're trying to use it in
    an ambient magnetic magnetic field.
-- jt]]