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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Is there time dilation at the gravitational cancellation point between two masses?

I read that at the point of gravitational cancellation between two masses there was still time dilation, because this dilation depends on the gravitational potential and not on the gravitational force ...
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How does gravity emerge from mass? [closed]

Per GTR, spacetime is curved by the presence of mass giving rise to the perception that a force (gravity) is at work. (1) How does gravity emerge from mass and (2) why does mass perturb (i.e. curve or ...
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What is the Correction Function in Poisson's Equation for MOND?

I am looking to do a celestial simulation using MOND for the final project of my intermediate mechanics course. From the Wikipedia page, it seems that preserving Newton's Third Law requires deriving a ...
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How does friction effect an object that is being pulled up an inclined plane [closed]

I have a block on slope of 36.9 degrees. The objects weight due to gravity is 25N. The frictional force between the block and the slope is 7N. There is a rope attached to the block going up the hill, ...
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Question on gravity

Please excuse if my question seems very basic (I'm a lay person fascinated by physics and trying to learn more.) I'm trying to better understand gravity. I have read that "gravity is a natural ...
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Why the megaastrophysical objects do not collapse due to their gravitational selfattraction?

At the largest scale in the universe exist formations called filaments which form something like a spider web along the whole universe. But they seem to be quite static. So my question is about the ...
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Nonlocal Gravitational energy: How to localize nontrivial topology in GR?

Ok, This question has been beaten to death. I just wanted to look at it from a slightly different angle: Einstein, Rosen, and later Wheeler considered the possibility of particles as spacetime ...
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Why must gravity have a quantum mechanical description? [duplicate]

I know that to understand the Bigbang singularity or the blackholes, it is necessary to have a quantum description of gravity or quantum gravity. However, barring those kinds of explanations, is there ...
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On the implementation of the spherical collapse model in cosmology

Lecture notes on the spherical collapse model found online (https://www.uio.no/studier/emner/matnat/astro/AST4320/h12/undervisningsmateriale/spherecollapse.pdf is one of them) consider a spherical top ...
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Trying to estimate the path of a projectile with equations on graphic calculator. Need help

When a projectile is released with a very high velocity, it will not follow basic projectile motion because the Earth’s curvature will hinder those equations. In a crude sense, the Earth will curve ...
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Entanglement, and Spacetime [closed]

I’ve been reading how spacetime is emergent from entanglement. If true, then couldn’t someone do an experiment to destroy the entanglement and thus spacetime. Is it that the experiment is behind that ...
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What would the planet earth look like if we turned off all the forces other than gravity? What about the universe? [closed]

I can't imagine this scenario at all, but it seems like it should be trivial. It seems that everything would become a lifeless lump and then maybe the universe would collapse because there's no more ...
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What is the collective nature of gravity? [closed]

My understanding is that gravity is the interaction between all objects with mass. This applies to every single particle that has mass, regardless of size. We know that bodies with very large masses ...
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Can superconducting mercury around an object create a different gravitational field compared to another object? [closed]

I have a question. Could mercury itself or mercury with a certain additive of ferromagnetic substances around the object in a certain closed form, where the source for the electromagnetic field would ...
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Which unification theories would require WEP violation?

I was just reading this article about how the weak equivalence principle was recently confirmed up to one part in $10^{15}$, for two metal alloys orbiting Earth. Are there theories that expect the WEP ...
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Why does gravity decelerate fast particles?

Karl Popper writes: [General relativity] entails the astonishing result that any physical particle (photons included) which approaches the centre of a gravitational field with a velocity exceeding ...
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How much energy from gravitatational waves does the sun absorb?

I was wondering how much energy from gravitational waves the sun could absorb since it is so big and also has a massive gravitational pull. Is it possible for the sun to trap gravitational waves ...
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Gravitational decompression of the hot interior of the Earth, and subsequent recompression

If the Earth had a very hot, uniformly distributed, interior (i.e. no core, etc.) and it was suddenly decompressed, by a temporary reduction of gravitational force, would the heat energy of the very ...
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Is the generating function the phase factor when transforming from inertial to non-inertial coordinates?

Question When going from the Hamiltonian of an inertial frame $H$ to that of a non-inertial frame $H'$ they are related by the canonical transformation: $$ H = H' + \frac{\partial F}{\partial t}$$ I ...
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What portion of a neutron star's mass is in the form of gravitational energy? [closed]

The reason this question is being asked is that in the case of black holes around 100% of their mass is stored in their gravitational field and I am wondering if neutron stars come close. It is known ...
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Defining acceleration in gravity-free space

Without information from outside a closed spaceship, an astronaut cannot distinguish A from B. A) In gravity-free space, the floor accelerates upwards at $a=g$ and hits a dropped watch. B) On earth's ...
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Effect on vertical launch of ball from a rotating body

If a ball is launched vertically from the surface of the earth at the equator, assuming a vacuum, will the ball land in exactly the same place on the surface of the earth? Or does the fact that the ...
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How does a screw roll down an inclined plane? [closed]

I was thinking about how various objects would slide down on an inclined plane, and I just couldn't figure this problem out. So let's say I have this screw or cone on its side, on an inclined plane. ...
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Can we find out if we are uniformly accelerating through flat spacetime by looking at non-accelerating clocks? [closed]

The equivalence principle states that locally you can't tell if you are accelerating through flat spacetime or are at rest in a uniform gravitational field. Does this mean you can only tell the ...
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Does electromagnetic waves (light) bend spacetime like mass? [duplicate]

we know that mass bends space time does electomagnetic waves bend space time? because EM waves dosent have mass. we also know that higgs field and higgs boson is responsible for mass of photon is zero ...
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Does the intrinsic energy of an object vary, if measured at different heights in a gravity field?

The gravitational redshift has different interpretations. Several quantities vary with height (or seem to), by the same equation - time, energy, mass. I wondered if measurements can shed some light on ...
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Question on asymptotic flatness

What is the theoretical argument for the asymptotical flatness of the four-potential? Can one assume asymptotical flatness for the scalar dilaton field as well?
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Question about dilaton monopole interaction derivation

I am trying to understand how one derives the dilaton monopole interaction. In "Black holes and membranes in higher-dimensional theories with dilaton fields", Gibbons and Maeda mentioned ...
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Mass curves spacetime. Is there any theorized "anti-mass" that counteracts this effect? [duplicate]

Things like faster-than-light travel have very good reasons for being believed theoretically impossible (e.g. they allow traveling backwards in time). Things like magnetic monopoles are seemingly ...
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Angle of projection for the minimum time of flight for a given range

If a projectile has to cover a fixed range under gravity, then what should be the angle of projection for the total time of flight to be minimum? The initial and final point of the projectile are both ...
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Angular velocity of a coordinate system in General Relativity

In the textbook, The Classical Theory of Fields (Landau & Lifshitz), the authors express the line interval of the 3-dimensional absolute-space in the form $$dl^2=\gamma_{\alpha\beta}dx^\alpha dx^\...
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Using position of a free particle to measure time

Hartle, gravity An observer in an inertial frame can discover a parameter t with respect to which the positions of all free particles are changing at constant rates. This is time Then goes on to say ...
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Do extended bodies in a gravity field fall slower or faster than point-like structures?

The weak equivalence principle states that all point-like particles fall along the same in a gravity field. If a body is extended it experiences a tidal force which causes the bodie to elongate. If ...
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How massive objects affect distance measurements, or "But how far away is a black hole singularity, really?"

My question basically boils down to: Is the singularity of a black hole infinitely far away? I think questions like mine have been asked before, but they encounter responses like "no meaningful ...
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Linear Independence of dimensions

Are the dimensions of spacetime curved by gravity, linearly independent?
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Have we ever observed electron in gravitational interaction?

So, as the title suggests have we ever observed electron in gravitational interaction? If we did have we ever observed a positron (or any other antiparticle) in gravitational interaction? Is there any ...
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Einsteins gravity theory, but for static objects [duplicate]

https://www.youtube.com/watch?v=XRr1kaXKBsU this is a good video to explain Einsteins gravity. The video claims that objects always move in a straight line, with an absence of a force of gravity, ...
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Question about the Ricci scalar

The Ricci scalar in a linearized metric $g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu}$ reads $$R=\partial^\mu\partial_\alpha h^\alpha_\mu-\partial^\mu \partial_\mu h$$ Then we have $$\eta_{\mu\nu}R=\eta_{\mu\...
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Equivalence of Inertia and Gravity [duplicate]

I'm now wondering...does - energy=mass=inertia=gravity? Are they all, intrinsically, the same, "thing"; that is, the same, "entity".
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Gravitational vs Inertial forces

In D'inverno's relativity book, it says that if we describe flat space using a general coordinate system, the equation of motion of a free particle would have terms involving the connection. Those ...
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Schwarzchild Basis Vectors

In Schwarzschild metric, are the basis vectors $e_r$ and $e_t$ always orthogonal? If not, we would get non diagonal $g_{tr}$ terms, which we don't. But if we differentiate $e_r$ with respect to time ...
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How Big/Low would an artificial satellite have be to change the pull of the tides?

I learned that passing airplanes pull the tides in a similar style to the moon, but are too small to make a drastic change. How big would an artificial satellite have to be to make a measureable ...
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Would General Relativity work if gravity were not an inverse square law? [duplicate]

I understand that General Relativity explains gravity by framing it as a consequence of the curvature of spacetime rather than as a force. Does this theoretically guarantee that gravity must be an ...
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Is gravity of matter similar to temperature?

Apart of general relativity and the quantum theory postulate o gravitons I am looking for an alternative quantum physical interpretation of gravity of matter? Watching this short video-cut from Dyson'...
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Einstein-Hilbert Lagrangian in linearized gravity

The Einstein-Hilbert Lagrangian is: $$\mathcal{L}_{EH}=\sqrt{-g} R$$ where $g={\rm Det}[g_{\mu\nu}]$ and $R$ is the Ricci scalar. In linearized gravity $g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu}$ and $$\...
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How is the time dilation changed on a rotation fluid ellipsoid?

Are the polar and equatorial radiuses of a rotation fluid ellipsoid approximately depended of the rotation velocity by this equation $$\frac{{GM}}{{{r_{{\text{pole}}}}}} - \frac{{GM}}{{{r_{{\text{...
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How does the collapse of a spherical cloud of point-masses look in the Newtonian framework?

Imagine a spherically symmetric cloud of point masses, without angular momentum, interacting by gravity only. If we examine this process within a Newtonian framework, the particles accelerate towards ...
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Aerostatic force experienced by object due to air

This is an undergrad physics problem, which puzzled me because of the little background provided; see also the comment below by @RC_23. Problem. Compute the force exercised by the air to an object ...
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Gravitoelectromagnetism: How far does the analogy go?

In weak gravitaional fields, we can write equations analogous to the Maxwell equations: Gravitoelectromagnetism. Do the gravitoelectric field and the gravitomagnetic field transform like components ...
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Does Mach's principle imply that the gravitational field has a non-zero curl?

I would normally visualize the gravitational field as "radial", i.e., one whose curl is zero. However, while thinking about Mach's principle, particularly the notion of frame-dragging (as ...
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