Stack is correct. An accelerometer in free-fall proves that it is inert and that the earth is accelerating upwards.
No, they are entirely wrong, as has been explained repeatedly.
The point of the equivalence principle is not to say Earth is accelerating upwards, but that there is no way to tell the difference between a uniform gravitational field and uniform upwards acceleration.
The key part here is UNIFORM.
So no, an accelerometer in free fall, still can't tell the difference.
What can tell the difference is moving that accelerometer around, or getting a bunch of them, and placing them at different locations on Earth's surface.
If it really is Earth accelerating upwards, they shouold all read the same within uncertainty.
But in reality they will read different values depending on location.
However, if there was something invisible pulling every atom of the hair "down," it should not become weightless.
Wrong again.
If there was something invisible pulling every atom of the hair down at the same rate, it SHOULD become weightless, until something tries to stop that.
You are now basically saying that the equivalent principle is wrong, and that a uniform gravitational field should not act the same as uniform acceleration.
That they should produce different effects.
But I'm almost certain that you know you are now spouting pure BS, where you are yet again blatantly distorting the facts to try to prop up your fantasy with no concern for the truth.
While the cabin is falling there should still be "gavity" pulling every point of the rope "down" as in the left hand side of the below image. Parts of the rope should not be able to float and deform upwards weightlessly without resistance against gravity, as in the right hand side of the image.
In the absence of all other forces, including air currents.
But that applies regardless of if it is in a hypothetical area without gravity, or in free fall with gravity.
Without other forces, then in a hypothetical area with no gravity, the rope shouold just sit there being perfectly straight. Other forces can then perturb it to move part of the rope up and part of it down.
Without other forces, in free fall with gravity, the rope shouold all be being pulled down at the same rate, by which I mean each part of the rope experiences the same specific force. This also causes it to sit there being perfectly straight. Other forces can then perturb it to make parts of the rope accelerate more or less due to a greater or lesser net specific force.
Hence, we have a demonstration that reality acts as if freefalling bodies are inert and the earth is accelerating upwards.
Which is NOT the issue.
The issue is not if it "acts as if".
The issue is what is reality?
Appealing to situations where you cannot tell if it is gravity pulling down or Earth accelerating upwards does NOT show Earth is accelerating upwards.
It shows you can't tell.
You need to appeal to situations where it is different.
Such as the variations in g accross Earth you keep dodging.
You two are embarrassingly mistaken, and need to learn more about the Equivalence Principle and Einstein.
Follow your own advice, as you are outright contradicting them.
Einstein even uses the fact that you become weightless in freefall as part of his proof against Newtonian Gravity.
Not so much as a proof against it, as an alternative explanation for why mass for gravity is the same as mass for inertia, and to justify the explanation of curved space time.
earth is accelerating upwards through curved space.
Not space, spacetime. They are different.
The surface of Earth accelerating outwards through spacetime is fundamentally different to Earth's surface accelerating upwards through space.
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