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Questions tagged [equivalence-principle]

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Equivalence Principle: from falling bodies to all physical processes [duplicate]

Einstein's elevator thought experiment considered that in the Minkowski space-time of special relativity, all bodies fall identically. What grounds did Einstein have to generalise this falling bodies ...
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105 views

Einstein Elevator thought experiment

Were there any background theories for Einstein's elevator thought experiment which developed the equivalence principle. Can Newton's equivalence principle (the equality of inertial and gravitational ...
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1answer
61 views

How did Einstein generalise the Einstein elevator thought experiment to conclude with the equivalence principle?

Suppose a reference frame S1 is accelerated in the x direction with a constant acceleration g. A second frame S2 is at rest in a homogeneous gravitational field which imparts to all objects an ...
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1answer
69 views

Special and general relativity

Is the light postulate in special relativity (that the speed of light is constant in all frames of reference) correct if the equivalence principle shows that light slows down in gravitational field? ...
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Why do bodies fall identically in uniform acceleration and uniform gravitational field? [duplicate]

In his reformulation of Einstein’s Elevator thought experiment, James Robert Brown (1993) says that an observer in a uniformly accelerating spaceship in space (free of gravitational effects) will see ...
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4answers
138 views

Gravity, falling bodies, and the equivalence principle

Why is that bodies in a box accelerating uniformally in space that is sufficiently removed from gravitational fields fall identically to bodies in a box located in a homogeneous gravitational field (e....
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1answer
41 views

How did Einstein use the conclusions of special relativity to reach the equivalence principle (using the Elevator thought experiment)?

Could someone please explain how Einstein used the Elevator thought experiment and the principles of special relativity to conclude that uniform accelerates creates uniform gravitational field (...
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1answer
114 views

Einstein's Elevator thought experiment and relativity

Einstein's elevator thought experiment contains the following premise: An observer in a box will see free bodies moving identically between when the box is uniformly accelerating in gravitational ...
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7answers
4k views

If gravity is a pseudoforce in general relativity, then why is a graviton necessary?

As far as I’m aware, gravity in general relativity arises from the curvature of spacetime and is equivalent to an accelerated reference frame. Objects accelerating in a gravitational field are in fact ...
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395 views

Is quantizing acceleration equivalent to quantizing gravity?

It's been said that gravity is locally equivalent to acceleration. It is also been said, that we need to quantize gravity. But doesn't that imply that this would have to be equivalent to quantizing ...
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1answer
122 views

Is the gravitational field an illusion, a by-product of geometry? [duplicate]

The principle of general covariance from the Equivalence Principle (EEP) tells us that there is no way in principle to locally distinguish between an inertial acceleration and the effects of a ...
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0answers
32 views

Experimental evidences satisfying charged particle emits radiation in gravitational field

Is there any experimental evidence exist that a charged particle at rest in gravitational field emit radiation and charged particle in free fall don't emit radiation ( According to equivalence ...
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3answers
86 views

Do centrifugal force and gravity differ in their effects on objects?

If the type of object matters, consider the human body. If the situation matters, consider standing on the inside wall of an O'Neill cylinder compared to standing on the surface of Earth. "Differ in ...
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2answers
105 views

Reason of no reaction force on a person in a lift falling freely under gravity

a person in a lift falling freely under gravity feels weightlessness because the force of reaction between the person and the plane with which he is in contact vanishes. why force of reaction vanishes?...
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2answers
435 views

Rindler Coordinates and homogeneous Gravity Field

I understood from the equivalence principle that an accelerated observer in free space is equivalent to a stationary observer in a gravitational field. As far as I understood further, this means to ...
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1answer
99 views

How does Rovelli's idea of time and gravity relate to inertia?

In "The Order of Time" (pg 12-13) Rovelli says "If things fall, it is due to this slowing down of time. (near a mass) Where time passes uniformly, in interplanetary space, things do not fall. ...
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2answers
146 views

Equivalence principle and local inertial reference frames

Local inertial reference frames are defined as follows: Pick a set coordinates for the manifold (assuming the manifold can be described by global coordinates) $\{x^i\}$ such that $g(p) = \eta$ is the ...
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Relativity of Jerk

Popular expositions of general relativity start with a thought experiment showing that it is impossible to distinguish a constantly accelerating frame of reference in a free fall from a free floating ...
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1answer
88 views

Near-relativistic car speeding over a bridge

I have read this problem / exercise (I don't remember the exact numbers, so I put my own) in William Burke's "Applied Differential Geometry" and it has always puzzled me regarding the relation between ...
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125 views

Are mass or inertia the same thing, the same properties?

I think so. But I wold like to know another opinions to confirm.
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107 views

Can the origin of mass or inertia depend only of the gravitational field of matter? [closed]

The gravitacional field is directly proportional to mass or inertia. It doesn't have another property or field like this, with this power. I think that when we apply a force to an object, the ...
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1answer
124 views

Can an Observer Distinguish between Unruh Effect and Hawking Radiation by Measuring Temperature?

In Unruh effect, the temperature of background appears to be proportional to acceleration. On the other hand, the temperature of a black hole is inversely proportional to its mass. If the two ...
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1answer
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Does Bell's Theorem suggest both Nonlocality and “Temporal Nonlocality”? [closed]

Bell's Theorem pretty much rules out any local hidden variable theories, and any hidden variable theory that's nonlocal is just regular quantum mechanics with an extra variable thrown in. But, since ...
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2answers
248 views

Why must the worldline for a freely-falling body be straight?

If spacetime were on an xy graph, the x-axis being time and the y-axis being space, an object that is in interstellar space with no noticeable gravitational influences on it will have a worldline that ...
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2answers
172 views

How to infer from Einstein Equivalence Principle that a test particle should follow geodesic?

Einstein Equivalence Principle (EEP) states that A frame linearly accelerated relative to an inertial frame in special relativity is LOCALLY identical to a frame at rest in a gravitational ...
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1answer
108 views

Gravitational acceleration in GR

What is the meaning of gravitational acceleration $g$ in the General Theory of Relativity, given that objects in free fall experience weightlessness? Can gravitational acceleration be thought as a ...
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1answer
98 views

Equivalence principle and bending of a light ray

In some explanations of a phenomena of curved spacetime we have an example of a light ray emitted in a freely falling space ship perpendicular to the direction of a free fall. In this case, for an ...
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0answers
48 views

Equivalence Principle and Exapansion and Shear Tensor

I read in my class notes that the professor said using equivalence principle, it is always possible to choose around any point $p$, a 2-dimensional space-like neighborhood such that the expansion and ...
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85 views

Electron and gravity- equivalence principle

According to equivalence principle, we cannot distinguish gravity with inertial force. Let's assume that there is space shuttle which contain observer and electron. There is some force that is gravity ...
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2answers
235 views

Equivalence principle, is gravity a fictitious force that we feel everyday?

I am currently self studying general relativity. I have a question regarding the equivalence principle. If an observer is in the elevator in deep space (or Minkowski space) where there is no ...
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2answers
391 views

Equivalence principle and the meaning of the coordinate speed of light

Short version: Does the equivalence principle give us a means to tell if variations in the coordinate speed of light have absolute or only relative significance? Background In general relativity ...
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3answers
766 views

Confusion with the equivalence principle and inertial frames

This is an explanation of the equivalence principle. A. says accelerating frames can simulate gravity. Then, I am confused. Are the frames presented in A. inertial frames? Compared to B. I have the ...
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0answers
150 views

Is Thomas rotation compatible with equivalence principle?

I have designed a thought experiment for which I cannot find a clear solution: An infinitesimal laser gun and a point target both move with a velocity $v$ towards a deep rhomboidal hole dug in the ...
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2answers
189 views

Why can't Newton's 1st law be expressed as an autoparallel transportation in space?

I'm following this series of lectures on differential geometry and general relativity. In the linked lecture (Lecture 9), at around 24:24, professor Frederic Schuller made the conclusion that one can ...
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3answers
17k views

If I drop a ball in an accelerating rocket, will it bounce? If so, how?

Einstein's equivalence principle says that you cannot distinguish between an accelerating frame or a gravitational field. However, in an gravitational field, if I drop a tennis ball, it will bounce, ...
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2answers
129 views

Why model spacetime as a semi-Riemannian manifold?

I'd like to collect arguments for the use of a semi-Riemannian manifold as a mathematical model for spacetime. I think this is closely linked to the equivalence principle, but I can't shape this into ...
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3answers
111 views

Equivalence Principle [closed]

Let’s imagine that the Equivalence Principle did not exist. Let’s assume that gravity works like any other force. That greater masses fell at a faster rate than smaller masses. Under this new ...
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4answers
927 views

Why do gravitational mass and inertial mass appear to be indistinguishable? [duplicate]

I have learnt that heavier the object is (the more gravitational mass it has), the more resistance to the change of motion it is (the more inertial mass it has). I can accept this fact but I can't ...
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1answer
217 views

Problem with different Equivalence Principle Statements

I'm having trouble understanding the differences between the different forms of the Equivalence Principle. I've search in other questions and I think that this was not previously asked, at least in ...
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1answer
113 views

Trying to understand the equivalence principle in GRT

Suppose that two observers are on a sphere of radius $r$ with angle $\phi>0$ and distance $d>0$ from each other and they are accelerated from inside to outside perpendicular to the sphere. Then ...
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3answers
109 views

How can one determine if they are not experiencing Earth gravity? [closed]

Suppose you are kidnapped and you don't know who did it. You have no memory of the trip that brought you to the building where you are now being held. You have reason, however, to suspect that you are ...
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1answer
423 views

Electromagnetism and equivalence principle?

The Maxwell equations for the electromagnetic Potential $A_\mu$ are (using Lorenz gauge). $$\nabla_\mu \nabla^\mu A^\nu - R^{\nu \mu} A_\mu = j^\nu$$ However the equivalence principle states: No local ...
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1answer
49 views

Equivalence principle and quantum gravity

Do new concepts of gravity negate the validity of the equivalence principal? or do all theories (waves, string, etc) and mathematics apply equally to gravitation and accelerating frames?
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Can we think of the proof of local flatness theorem as the proof the the Einstein's Equivalence principle? [duplicate]

Sean Carroll states the Einstein's Equivalence Principle (EEP) as "In small enough regions of spacetime, the laws of physics reduce to those of special relativity; it is impossible to detect the ...
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1answer
44 views

Equivalence Principle - mass on table example [duplicate]

I hope this question won't be ill received. I have a rather simple question in physics. I never got a satisfying answer to the following question: If a man holds a massive body in the air such that it ...
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2answers
782 views

General covariance from the equivalence principle

Einstein's equivalence principle (EEP) tells us that there is no way in principle to locally distinguish between inertial acceleration and the effects of a gravitational field by carrying out any non-...
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3answers
179 views

Will a stationary charge in a uniform gravitational field radiate?

Imagine a charged particle Q standing still in a uniform gravitational field g (i.e. on a table on the surface of a planet). Assume observers K1 and K2 when K1 is in free-fall and K2 is co-stationary ...
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137 views

Violation of the strong equivalence principle in scalar-tensor theories

As I understand it the strong equivalence principle is the statement that within a infinitesimal neighbourhood of any spacetime point all physical interactions (gravitational and non-gravitational) ...
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2answers
111 views

How does Newtonian gravity violate law of inertia?

I came across a line on http://physics.ucr.edu/~wudka/Physics7/Notes_www/node49.html " If the experiment is tried in vacuum any two objects when released from a given height, will reach the ground ...
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1answer
179 views

Why do people use equivalence principle differently in Hawking radiation?

In discussions of Black hole information paradox, people usually argue that the falling observer shall not see radiation at the horizon or near the horizon due to the equivalence principle. That is, ...