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Questions tagged [gravity]

Gravity is an attractive force that affects and is effected by all mass and - in general relativity - energy, pressure and stress. Prefer newtonian-gravity or general-relativity if sensible.

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Dark Matter/Energy & Space-Time [closed]

After searching for quite a while for a minimalist approach to explaining Dark Matter as well as Dark Energy, unfortunately without much good, I decided I may as well help fill the explored paths, or ...
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Is the Poincaré gauge theory a real gauge theory in the mathematical sense?

When studying Poincaré gauge theory using Milutin Blagojevich's book on "Gravitation and gauge symmetries" we find an interesting line of thought. But to get that I need to set some ...
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If we compress a mass $M$ to create a black hole, how does it gravitational field change?

If we create a black hole by compressing a mass $M$ to a radius smaller than Schwarzschild Radius, would the gravitational force of the mass $M$ (now a black hole) be different before and after ...
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Deflection of a null geodesic in Schwarzschild geometry

Background In the Schwarzschild geometry the gravitational deflection of light can be described by the following equation: $\frac{d\phi}{du} = \left(\frac{1}{b^2} - u^2 + 2Mu^3\right)^{-1/2}$ , where $...
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Why does a particle move in space in a curved spacetime?

I understand that all the particles move in spacetime at $c$. A massive particle affects the spacetime, rendering it bent or curved. In the absence of a massive particle, the said particle (in unbent ...
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What happens if the Compton wavelength of a particle exceeds the inverse square root of the Ricci tensor (call it curvature)?

What happens if the Compton wavelength of a particle exceeds the inverse square root of the Ricci tensor (call it curvature) precisely? Can somebody please use some formal QFT in curved spacetime to ...
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Difference between potential and potential energy mathematically

I search google, quora, and reddit: What is the difference between potential and potential energy? Potential is the ability to do work. Potential Energy is the amount of energy it acquires. ...
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Questions about setup and analysis of the gravitational time dilation experiment of Chou, Hume, Rosenband, Wineland (2010)

Notable experiments relating to (kinematic and gravitational) time dilation have been reported 2010 in article "Optical Clocks and Relativity", by C. W. Chou, D. B. Hume, T. Rosenband, D. J. ...
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Is there any way to calculate the gravitational potential energy of an object without knowing it's mass?

I'm trying to solve for the mass of an object in a gravitational field, but with the equation PE=GMm/r I need to know the object's change in gravitational potential energy, which I need the object's ...
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If a star gravity can change the apparent location of another star on the sky, can it change the gravitational field vector of that star?

If a star gravity can change the apparent location of another star on the sky can it change the gravitational field vector of the second star? In simple words if a star gravity deflects the position ...
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Metric tensor's relation to gravitation potential

I am trying to figure out the role of gravitation potential and its generalisation to the metric tensor. I know how we can relate the gravitation potential and the metric by looking at the geodesic ...
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Schwarzschild metric: stars vs. black holes

Background The Schwarzschild metric can be used to describe the geometry of the vacuum spacetime outside a spherical massive object. For a star of radius $r$ (which is larger than the corresponding ...
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"Gravitational Charge" in Newtonian Gravity in Analogy to the Electric Field

I am currently reading Carroll's GR book p. 48. There he says that If you like, $m_g/m_i$ can be thought of as the "gravitational charge" of the body with the gravitational mass $m_g$ and ...
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How much work is done to maintain vertical position (hovering) of a drone? [closed]

Ignoring all losses in the efficiency of the means to lift the drone, this would reduce down to resolving the key elements of the equation involving a) the acceleration of gravity and 2) the time, and ...
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Does the frequency of light have any effect on gravitational lensing? [duplicate]

General relativity considers gravity as the curvature of space-time instead of a force. Therefore, what is bent around an astronomical object is the space-time itself. The light just follows the path ...
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Is there a possibility of frame dragging inside the event horizon?

Is there a possibility of frame dragging inside the event horizon? If frame dragging is related with gravity and space and as the black hole fills a space and produces a gravitational effect that ...
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Derivation of Lovelock gravity field equations from the more general f(Lovelock) theory

I'm trying to derive the Lovelock gravity equations of motion (EOM) from the more general f(Lovelock) theory (see https://doi.org/10.1007/JHEP04(2016)028). In Lovelock gravity $$\nabla^\alpha \frac{\...
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Can something be a black hole in one frame of reference but not in another? [duplicate]

So my understanding is because E=mc^2, and kinetic energy is included in E, something moving quickly relative to you gains mass in your reference frame, compared to that same object at rest. Black ...
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Does Earth's rotation affect the orbital velocity of its satellites?

We all know about the spin of black holes. That spin and of course it's gravity determines the minimum distance a star can orbit the black hole with a min orbital velocity. Do we see similar result? ...
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How does gravity affect time dilation? [duplicate]

I understand that the faster you move through space the slower you move through time, but how does gravity play a role in that?
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How can time be curved?

Time isn't a physical object, but according to Einstein's theory of gravity, mass bends spacetime towards things with mass and makes them fall. How does a physical object affect something intangible?
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Normal force shift for ball kept in cavity

Adapted from JEE advanced paper-1 of 2020 If you see the left side of the Planck which the ball touches, it seems so that as we vary $\theta$, the contribution of the force from that point of contact ...
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Does dark matter act gravitationaly to itself. If Yes, why does not form more compact objects? [duplicate]

Does dark matter act gravitationaly to itself.If Yes, why does not form more compact objects? Can this be explained as its components have enough kinetic energy to overcome the collapse?
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Time dilation in free fall vs standing [duplicate]

A small object standing on a massive object undergoes time dilation relative to an observer far away that depends only on the masses and distance of the objects. What happens in the case of free fall? ...
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What is a charge, apart from fundamental property? [duplicate]

What really a charge is apart from saying its a fundamental quantity. I mean IF in case of gravity, its curvature of spacetime due to mass so just like that can anyone explain how charge like ...
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Conflicting intuitions about free fall

So I just started studying physics recently, and I came up with a question that I'm not sure how to solve, and I think it may be because of some fundamental misunderstanding. I don't want anyone to ...
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Why is gravity considered a force of nature? [duplicate]

Wouldn’t gravity be considered an effect to the other forces? An object of a given mass warps space time. The larger the mass, the greater the warpage. There is no graviton exchanged between the ...
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Earth as inertial reference frame: finite radius effects

In a recent question I tried to clarify under what conditions the Earth can be considered as an inertial reference frame. The opinions, summarized in my own answer to the cited question, are that ...
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Loss of quantum coherence due to gravity [closed]

Consider a particle which moving inside a gravitational field.Will it lose its quantum coherence? According to GR , the particle will follow a geodesic but if it does then shouldn't its wavefunction ...
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Is there an approximate expression for the force between two black holes?

Just curious: is there an approximate expression for the gravitational attraction between two Schwarzschild black holes of masses $M$ and $m$, held without relative speed at some center to center ...
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Does an object rolling down a slope have more momentum than a object in free fall?

Physics newbie here. I am trying to figure out in which of the following scenarios would the object end up further from the starting point: Will a car that veers off a road that has a vertical cliff ...
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Does GR gravity obey a form of Gauss' law? [duplicate]

In Newtonian mechanics, Gauss' law is the assertion that, for any volume $V$ enclosed within a regular surface $\partial V$, the flux of the acceleration produced by gravity through $\partial V$ is ...
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Why can circular motion not be used to calculate kinetic energy of a person standing on Earth?

I did this question: In a sense we all have kinetic energy, even when we are standing still. The earth, with a radius of $6.37×10^6 \mathrm m$, rotates about its axis once a day. Ignoring the earth's ...
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Why and when can the Earth be considered an inertial reference frame?

The question has been asked (e.g., here and here), but I would like to get a more definitive and mathematically formal answer. The Earth rotates around its axis, around the Sun, and participates in ...
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How to interpret line of sight velocity distributions and dispersions of a galaxy?

What I did: I am analysing some simulation snapshots of the Milky Way and it is modelled as a DM halo – bulge – disc system. I produced some mean line of sight velocity (LOSV) and dispersion of mean ...
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Gravitationally-driven electrical potential differences in conductors

This question asks Free electrons in a metal are attracted by gravity towards Earth. So why don't they lay down to the bottom of the conduit, like sediment at the bottom of a river? The current ...
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If a black hole's mass is derived from its gravitational field, then why would mass be restricted inside the EH, while the field extends outside? [duplicate]

I have read this question: Let's consider the simplest kind of black hole, which is one with no rotation or electric charge. The quick answer to the question is "yes, the mass is entirely within ...
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If gravity isn’t a force how does it cause motion? [duplicate]

In general relativity, gravity is the effect of curving space-time caused by mass and is described as an acceleration. So what exactly is causing this pull towards the earth? Is a force not required ...
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Shouldn't black holes exert the same gravitational force as an object of similar mass but lower density?

If the earth got shrunk into the size of a peanut, it would turn into a black hole, which would have a higher density but same mass. Since the center of mass of both bodies would be the same, the ...
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If the exchange of virtual Gravitons isn't real why do bodies attract?

I have been told Earth is not really sending particles to me and keeping me on the ground. That it is just a convenient thing to do in calculations. However if the exchange of gravitons isn't real, ...
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If light and gravity travels in the same speed then why light cant escape the gravitational pull of black holes?

Speed of gravity is infinite? If fastest thing is light then how universe is spreading faster than the speed of light?
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When is gravity a force? [duplicate]

We all know that gravity is best explained by general relativity which says mass curves space-time. This means that gravity is not a force but an acceleration and we are “falling” towards massive ...
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Does Shape Dynamics use Space relationalism?

On Wikipedia it says Shape dynamics is an implementation of Space relationalism however I don't see how this can be true. In general relativity gravity exists thanks to Space substantivalism, the fact ...
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Yet Another Twin Paradox Question - Is orbit an inertial reference frame?

This question The "Satellite Paradox": Twin paradox in orbiting satellites asks something similar, but none of the answers quite get at the meat of what I'm trying to understand. On the ...
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Black holes and time dilation: how we could see interaction with other objects?

I have a question on the observable behavior of a Black Hole. So, I am not asking what is going on “now” at the Event Horizon or how can I “see” (get particles or waves). The question is how should it ...
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Is time dilation reduced when two opposing gravitational forces equally pull on an object? [duplicate]

(I apologize for my naivete in advance.) The Lagrange points around the earth and the moon provide a semi-stable space to put objects because the gravitational pull (combined with centripetal force) ...
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What is Shape dynamics?

From Wikipedia: In theoretical physics, shape dynamics is a theory of gravity that implements Mach's principle. In General relativity curvature of Spacetime causes gravity, in String theory it is ...
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If Graviton is considered as a particle, does Gravity have momentum?

Graviton is a hypothetical particle considered as a quanta of Gravity, if it is considered as a particle, does Gravity has momentum ?
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Why doesn't the curved spacetime curve the stick?

We know that gravity is not a force, but a curvature of the spacetime. This is a great visualization. But I don't understand something. If we live on Earth in a curved spacetime, and this curvature is ...
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What is the shape of an orbit with known period in the restricted three-body problem?

The three-body problem is the problem of taking the initial positions and velocities of three point masses and solving for their subsequent motion according to Newton's laws of motion and universal ...

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