# Questions tagged [equivalence-principle]

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### Motivation for curved spacetime on General Relativity

I'm trying to motivate the theory of general relativity. Concretely, using which arguments is it deduced that spacetime must have the structure of a curved Riemannian manifold? From the strong ...
719 views

### Why is gravity different from other forces?

Unlike other forces, the "amount of force" gravity applies to different bodies is different. for example, if your hand has the force of 10 N, it could have accelerated a body with the mass ...
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### Are there 4D spacetime not described by GR? [closed]

I heard the EFE is specifically for 4 spacetime dimensions. Does it mean whenever there are 4 spacetime dimensions, there is automatically GR? In other words, are there 4D worlds or spacetime that ...
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### Is the accelerating field removed when using the GR equivalence principle?

Suppose I have a charged hollow sphere that is hyperbolically accelerated by a constant electric field E. The Equivalence Principle tells me that this is physically equivalent to placing the charged ...
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### Can the equivalence principle be safely used in non-relativistic mechanics?

Imagine an ideal pendulum in a train. While the train is in uniform motion, Newton's laws apply within the train, and we can easily write down the equations of motion for the pendulum. Now assume the ...
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### Doubt in the Equivalence principle [duplicate]

In the equivalence principle, being in an accelerated reference frame is equal to being in a gravitational field. So,now I can consider earth as an accelerating reference frame. But, if that is true, ...
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### The gravity-acceleration equivalence principle doesn't seem like exact equivalence. Is there something I'm missing?

Suppose I'm trapped in a box, and the box is $3\ \mathrm{m} \times 3\ \mathrm{m} \times 3\ \mathrm{m}$. I designate one vertex to be $(x,y,z)=(0,0,0)$ and the opposite one as $(x,y,z)=(3,3,3)$. I'm ...
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### A problem regarding light bending

My professor in his lectures has stated that a consequence of Einstein Equivalence Principle (EEP) alone is that light bends in a gravitational field. The proof went as follow: Imagine to be a free ...
537 views

### General Relativity: Definition of Locally Inertial Frame

The Einstein Equivalence Principle states that in a sufficiently small frame of reference is impossible to know if we are into a gravitational field or not. Equivalently we cannot say if we are in an ...
1k views

### Difference between Free Fall and Constant Velocity

We know that astronauts in the ISS feel "weightless" because they are in a perpetual free fall. The earth's gravity is the only force acting upon them, and it is accelerating them towards ...