The Stack Overflow podcast is back! Listen to an interview with our new CEO.

Questions tagged [equivalence-principle]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
2
votes
1answer
95 views

How much of general relativity does the equivalence principle actually imply, why is it different?

From EP we have that gravity is not a force but a pseudo force, i.e an inertial force due to a gravitational field an accelerating a body independantly of its mass, in other words, the trajectory of ...
0
votes
1answer
63 views

Time dilation, mass-energy equivalence, and implications for the passage of time [closed]

I'm an amateur physics enthusiast, and there is a question that's been in the back of my mind for some time that I haven't been able to answer on my own. First, I want to define a couple of terms and ...
1
vote
2answers
122 views

Equivalence Principle holding in Special Relativity? (let alone QFT)

Motivation I am pretty confused of why people are hopeful to find a version of the equivalence principle ("the complete physical equivalence of a gravitational field and a corresponding acceleration ...
2
votes
1answer
106 views

Equivalence principle doubt

There is something about Einstein Equivalence Principle that I don't quite get. This is my reasoning: Equivalence principle $\rightarrow$ locally, acceleration is equivalent to a gravitational field ...
4
votes
4answers
128 views

How does Newtonian Gravity explain the difference between the experience of 1G and zero gravity? Or can it?

Humans can feel the difference between being on earth's ground, and being in space (zero gravity) This can be explained by general relativity, where in (1), force is applied by the ground upwards, ...
1
vote
2answers
64 views

Do hot gasses actually weigh more than cold gasses in SR?

I was reading: https://plato.stanford.edu/entries/equivME/#PhysMassEnerEqui Where they begin to discuss a weighing a relativistic gas against a cold gas. The idea is that the relativistic gas ...
2
votes
2answers
120 views

Does the equivalence principle imply that light must move slower when moving away from a massive object?

Thought experiment: Elevator going up at an extreme acceleration, pulse of light bouncing up, and down between mirrors on the floor, and the ceiling. Won't it take light longer to travel from the ...
1
vote
1answer
56 views

Why does things travel in a straight line in inertial frames?

Why does physical entities travel in straight paths in a flat space-time and in geodesic in curved spacetime? Is it due to Inertia? If it is, then why does waves also follow the same pattern?
1
vote
0answers
75 views

Entanglement of Black Holes with the outside universe

Black holes are thermal objects which means the density matrix of the black hole is in a thermal state. This means that the black hole has to be maximally entangled with the rest of the universe to ...
0
votes
0answers
37 views

Can we apply the equivalence principle in electromagnetics to multiple regions simultaneously?

Note: I posted the same question on the electrical engineering stack exchange with no luck so far, possibly because it's quite theoretical, so I'm posting it here again. I'm not sure if it's ...
1
vote
2answers
110 views

Acceleration in general relativity

Let's say that, from my point of view, another observer is accelerating. Now, from his point of view, he is standing still: all he feels is an overall fictitious force of gravity, which is just a ...
2
votes
7answers
199 views

Can we feel gravity while free falling?

I watched some video saying that there is still gravity in space station and almost same strong as it on Earth, the reason they feel no gravity is because the centrifugal force of the orbit is same as ...
1
vote
2answers
80 views

On local inertial frame and acceleration in general relativity

[Q1] In the general relativity, a local inertial frame is mentioned. The local inertial frame is a notion, which is related to (or represents) the equivalent principle. Here, I understand that, in ...
8
votes
2answers
427 views

Silly doubt about tidal effects and Einstein Field Equations

Suppose I give you the following line element: $$ ds^{2} = -(1+2\phi)dt^{2}+(1-2\phi)(dx^{2}+dy^{2}+dz^{2}) \tag{1}$$ Without saying anything you might think that this is just another line element ...
1
vote
3answers
90 views

Equivalence Principle: Why is sitting in space the same as failling in a uniform gravitational field [duplicate]

The equivalence principle states that no experiment can determine whether one is being accelerated or if there is gravity present. This is insightful and intuitive. However, I was sort of surprised. ...
0
votes
4answers
157 views

Why gravitational mass and inertial mass being same was a problem before Einstein solved it?

Why is it so that Einstein is credited with telling us the reason for the equivalence of inertial and gravitational mass of an object? Did Newton ever make a distinction between the two masses? What ...
1
vote
2answers
178 views

Does semi-classical gravity obey the equivalence principle?

Question I was recently wondering about semi-classical gravity : $$ G_{\mu \nu} = \frac{8 \pi G}{c^4} \langle \hat T_{\mu \nu} \rangle_\psi$$ Does this obey the equivalence principle? My ...
33
votes
5answers
8k views

Is floating in space similar to falling under gravity?

In the case there is no air and your eye are closed, then does falling from the sky under gravity have the same feeling as floating in space? Can our body feel that we are accelerating without the ...
0
votes
1answer
27 views

Falling bodies in an accelerated elevator

If a sealed elevator were subjected to a massive acceleration in interstellar space and two weights were dropped from ceiling to floor, as far apart as possible on opposite sides of the elevator, ...
0
votes
1answer
47 views

Is a body in passing gravitational wave still in free fall?

I have a simple apparatus: a box and inside it a test particle (small bullet). If the device is in inertial motion or affected only but (static) gravitational field of another massive body (in free ...
0
votes
0answers
40 views

Invariance of forces

In Newtonian mechanics, the inertial forces depend on the reference frame and the other forces are invariant. Are they still invariant when special or general relativistic effect are involved?
0
votes
1answer
37 views

What is proper name for non-inertial forces in GR?

General relativity works in all reference frames, so inertial forces are real in it. And due to the equivalence principle, gravity should be also considered inertial. So what is a good term for the ...
0
votes
1answer
62 views

How do we know who is moving? [duplicate]

If I am in a free float environment and there is another object at rest relative to me, and then I start to accelerate towards this object, do I know I am the one who is moving, since I am the one who ...
0
votes
3answers
160 views

Does general relativity reduce to special relativity for free falling objects?

The following was stated in a general relativity lecture series: "Full space is needed in GR. Minkowski space is sufficient for SR. However, Minkowski space is sufficient to compute properties of free ...
1
vote
2answers
116 views

Different prediction about the motion of a charge as observed by two different observers?

Suppose a charge is at rest in the laboratory frame. Also, say two observers in two vehicles A and B are approaching towards it. Let A be accelerating towards it and B be moving uniformly towards it. ...
0
votes
2answers
70 views

Is there “artificial gravity” created by a reference frame on a spinning object? [closed]

Believing the answer is yes, how then is spacetime curved? Will the spacetime uncurve when rotation stops? According to special relativity you can only see things from one's own reference frame. I do ...
0
votes
6answers
144 views

Acceleration in free fall [duplicate]

A body in free fall "feels" no gravitational force (equivalence). Why does it continue to accelerate. Why is your program refusing my question?
0
votes
1answer
69 views

Will tidal effect make physics laws different?

I was reading Wheeler & Taylor's Spacetime Physics. The authors mentioned about tidal effect, as well as all physics laws are same in free-float frame. I am left wondering if tidal effect will ...
1
vote
6answers
590 views

If an object with more mass experiences a greater gravitational force, why don't more massive objects fall faster? [duplicate]

According to Sir Isaac Newton, the gravity equation runs like this: $$ F = \frac{Gm_1m_2}{r^2} $$ where $F$ is the gravitational force, $G$ the gravitational constant, $m_1$ and $m_2$ are the ...
1
vote
1answer
54 views

Do “light” and “heavy” objects still accelerate at the same rate at near light speeds?

My (very poor) layman's understanding of physics is that as something approaches c, it has a relativistic mass that is a combination of its actual mass and velocity. Do this affect its acceleration ...
0
votes
1answer
77 views

Is it true that when you accelerate due to a non-gravitational interaction gravity is pulling you in the direction opposite to the acceleration?

We don't feel acceleration when we are only in a gravitational field due to equivalence principle as I understand it says gravity is simply inertia in spacetime. Is there any other type of force ...
1
vote
2answers
67 views

Now when we can measure gravitational field, how does the principle of equivalence hold true?

LIGO measured gravitational field waves. The whole thought experiment of Einstein, leading to ‘principle of equivalence’, assumes that there is no way to know inside the rocket that whether its ...
1
vote
1answer
71 views

Does general relativity (GR) solve mass-equivalence problem or just renames it?

It is usually said that GR solved problem of equivalence of gravitational and inertial mass. Yet, my objection is: OK, there is no gravitational mass in GR, but Einstein had to introduce mass as "...
0
votes
1answer
90 views

How does the Equivalence Principle imply that derivatives of the metric vanish in a freely falling frame?

Why do the first derivatives of $g_{\mu\nu}$ vanish in a freely falling coordinate system? I would like to start from the Equivalence Principle that for any point in spacetime there exists a locally ...
1
vote
1answer
107 views

Equivalence Principle and bending of light

Basically, the equivalence principle (EP) states that if someone is in a rocket in empty space with acceleration $g$ equal to that at the surface of the earth, any experiment he does cannot ...
2
votes
2answers
69 views

How come planets with different masses can orbit at the same velocity at the same altitudes?

Angular momentum is equal to r × p and angular momentum is also what gives planets with lower orbits a higher speed (because angular momentum is conserved). So as r decreases either m or v (p=mv) has ...
1
vote
1answer
51 views

Why acceleration due to gravity is not reliably defined?

In Sean Carroll's Spacetime Geometry, there is the following line on Page No.50 in 2014th edition: "The acceleration of a charged particle in an electromagnetic field is uniquely defined with respect ...
6
votes
1answer
94 views

Does a charge in a gravitational field make a magnetic field?

I know that general relativity unifies the electric charge with the magnetic field via relative motion. So if I accelerate a charge then anyone in another inertial frame will see a magnetic field. ...
3
votes
1answer
47 views

Detecting external 'forces' in an inertial frame

Disclaimer: Science noob here, I may not use all terms correctly. I've read somewhere of the following situation: An observer is inside a room (elevator) with no ...
1
vote
5answers
137 views

Einstein's Elevator - Constant acceleration eventually reaches $c$. Can't that be used to detect gravity vs acceleration?

Objects with mass that continuously accelerate will eventually approach $c$, but cannot exceed it. So if I find myself in an elevator, unable to determine if I'm in a uniform gravitational field or ...
1
vote
2answers
152 views

Christoffel symbol

In flat space, it is possible to find a coordinate system in which the Christoffel symbols are equal to zero at every point on the flat manifold. However, I was wondering if it is possible to find a ...
4
votes
4answers
505 views

Falling electric dipole contradicts equivalence principle?

Consider an electric dipole, with total mass $M$, consisting of charges $q$ and $-q$, separated by a distance $d$. The total mass $M$ includes the mass defect due to the negative electrostatic energy ...
0
votes
1answer
43 views

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 ...
1
vote
1answer
97 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 ...
1
vote
1answer
58 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 ...
1
vote
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? ...
0
votes
0answers
23 views

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 ...
1
vote
4answers
135 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....
0
votes
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 (...
1
vote
1answer
111 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 ...