Re: The Elevator in Free Fall

Tom Roberts il 24/12/2024 07:32:18 ha scritto:

On 12/20/24 12:51 AM, Luigi Fortunati wrote:

The cables break and the elevator goes into free fall.
Newton told us that the elevator accelerates and, therefore, there is a
force that makes it accelerate.
Then Einstein came along and told us that this is not true

>
This is one of your problems. Physics is not about "true or false"; we
make MODELS of the world we inhabit -- Newtonian mechanics and GR are
DIFFERENT MODELS. The problem is that you intermix nomenclature
willy-nilly between them.

Physics talks about models? Ok.

Newton's MODEL states that there is a *real* gravitational force
(F=GmM/d^2) that accelerates the mass <m> of the elevator towards the
mass <M> of the Earth (and vice versa), while Einstein's MODEL denies
that such *real* gravitational forces are present in the free-falling
elevator.

So, it is the presence or absence of *real* gravitational forces in the
"local" frame of the elevator that establishes which of the two models
is correct and which is not.

If in the free-falling elevator the *real* gravitational forces are NOT
there, Newton's model is wrong, if they are there, Einstein's model is
wrong.

Since the real gravitational tidal forces in the "local" space of the
elevator are there, Einstein's model is (conceptually) wrong.

Someone will ask: but then there are no elevators at rest on Earth,
effectively devoid of any real gravitational force?

I answer that such an elevator, where real *terrestrial* gravitational
forces are totally absent, exists but it is not the one in free fall.

In a thousand years they will have built an elevator that descends
downwards without limits.

I enter this elevator and press the down button.

The elevator descends downwards at a constant speed without falling.

At first, I do not notice anything but after a certain time I feel
lighter and then, as I descend more and more, my weight decreases until
it disappears completely when the elevator stops at the center of the
Earth.

That is the only point where the elevator has no trace of real
(terrestrial) gravitational forces inside it and, therefore, it is the
only inertial terrestrial reference system!

With respect to this truly inertial reference, all the other
terrestrial elevators in free fall are accelerated.

Luigi Fortunati