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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How can Voyager 1 escape gravity of moons and planets?

I think this one is pretty simple so excuse me for my ignorance. But since most planets in our solar system are very well tied to their orbit around the sun or orbit around their planet (for moons), I ...
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Gravity as a gauge theory

Currently, (classical) gravity (General Relativity) is NOT a gauge theory (at least in the sense of a Yang-Mills theory). Why should "classical" gravity be some (non-trivial or "special" or ...
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The energy of a Graviton

Maybe another stupid question, but what's the energy of a graviton? Is it $\hbar \omega$? Does it emit gravitons when an apple falls onto the ground, like photons be emitted when an electron transits ...
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Calculating Atmospheric Pressure on an Imaginary Planet

I am planning a series of science fiction novels that take place on an imaginary binary planet system. Both planets have a lower surface gravity than the Earth and one has slightly more mass than the ...
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Effects of space mining on Earth's orbit

I was reading a post about space mining, specially lunar mining. I was thinking about what would change in Earth's orbit if we start bringing tons of rocks to it? I mean, in a huge scale. So, would ...
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Why water in the sink follow a curved path?

When you fill the sink with water and then allow the water to be drained, the water forms a vortex.. And then it starts to follow a curved path downwards by effects of gravity.. Why this phenomena ...
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Can a black hole form due to Lorentz contraction? [duplicate]

Possible Duplicate: If a 1kg mass was accelerated close to the speed of light would it turn into a black hole? Imagine, a rod of length L is moving with velocity approaching the speed of ...
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What exactly is the microgravity field in orbit?

The ISS and other objects in orbit still experience small acceleration outside from the perfect line of orbit (of the system CM). For instance, two objects in the ISS that are let to be at rest will ...
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Mass Needed to Clear an Orbital Neighborhood

In 2006 the IAU deemed that Pluto was no longer a planet because it fails to "clear" the neighborhood around its Kuiper Belt orbit. Presumably, this is because Pluto (1.305E22 kg) has insufficient ...
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Is $4 \pi G$ the true most fundamental gravitational constant? [closed]

Newton's law of gravitation is: $$F = G m_1 m_2 \frac{1}{r^2}$$ It looks simple and natural. But that's only in 3 dimensions. Let's look what happens in $n$ dimensions: $$n=2 : F = 2 G m_1 m_2 ...
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Why does dark matter form walls and filaments

Related: How are galaxy filaments formed? And do they have any analogues in stellar formation? But I want to come at this from a different angle. Like the user asking that other question, I was a bit ...
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Would dark matter absorb gravitational waves?

Would the vast and seemingly diffuse clouds of dark matter floating around our galaxy (and most others) absorb gravitational waves? Is this perhaps why we haven't detected any yet?
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Are there models/simulations of antigravitational antimatter-galaxies?

In the comments to another question's answer, I started wondering: Assuming antimatter possessed negative gravitational mass§ (which is not proven impossible to date, though deemed unlikely), ...
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Does potential energy in gravitationall field increase mass?

I was just taught (comments) that any type of energy contributes to mass of the object. This must indeed include potential energy in gravitational field. But here, things cease to make sense, have a ...
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Why does angular momentum shorten the Schwarzschild Radius of a black hole?

Angular momentum causes the event horizon of a black hole to recede. At maximum angular momentum, $J=GM^2/c$, the Schwarzschild radius is half of what it would be if the black hole wasn't spinning. ...
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Materials with different gravitomagnetic permeability?

If you start with general relativity, and assume small perturbations around a nearly flat metric, it is possible to obtain linearized equations of gravity that look a lot like Maxwell's equations, ...
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String theory and trace anomaly in semiclassical gravity?

what does string theory have to say about the trace anomaly in the expectation value of the stress energy tensor of massless quantum fields on a curved background and its interpretation as the ...
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Where's earths death bulge, destroying everything in it's path?

I was watching a BBC documentary on space last night. It was talking about gravity, and it said that the reason we only ever see one side of the moon, is because the earths gravity is strong enough ...
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What keeps a gas giant from falling in on itself?

There is not enough gravity at the center to start nuclear fusion, but it seems that there would be plenty enough to collapse the planet.
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Gravitation law paradox for very close objects?

We all know that gravitation force between two small (not heavenly) bodies is negligible. We give a reason that their mass is VERY small. But according to inverse square law, as $r\to 0$, then $F\to ...
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Can one assign an equivalence principle of some kind to the EM field?

Introduction: Consider the EM field. There was a time when the field was defined in a similar manner to that of the gravitational field. This changed when the view on gravitation evolved to this ...
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How come gas molecules don't settle down?

If the earth's gravity exerts a net downward gravitational force on all air molecules, how come the molecules don't eventually lose their momentum and all settle down? How is the atmosphere is still ...
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Grain of sand attracting the sun?

My friend keeps telling me that according to physics... "The sun attracts a grain of sand on the earth with the same force that the grain of sand attracts the sun" or "A grain of sand on the earth ...
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Why can you remove the gravitational constant from a computer game simulation?

I've seen in a few gravity simulation games (ie. bouncing balls) the equation: force = G * m1 * m2 / distance^2 shortened to this by removing the gravitational ...
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Black holes in a head-on collision

Assume two uncharged non-rotating black holes traveling straight at each other with no outside forces acting on the system. What is thought to happen to the kinetic energy of these two masses when ...
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If you could ride an elevator through the earth [duplicate]

What if it was possible to ride an elevator straight through earth. If we take all the heat and pressure problems away, and assume it would be possible: What would happen with gravity? Would gravity ...
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Speed of gravity in cosmological codes and ephemeris generation

There are few questions in Phys.SE concerning the speed of gravity, and the answers are traditionally that the speed of gravity equals to the speed of light. But in that case I have three more ...
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Please clarify how entropy increases when matter gravitationally coalesces

On John Baez's website, http://math.ucr.edu/home/baez/entropy.html, he discusses the problem of how entropy increases when a cloud of ideal gas collapses gravitationally (no black holes - keeping it ...
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What is the likelihood of ever discovering the graviton?

How would one look for and confirm existence of a graviton? Someone was speaking to me about perhaps one day discovering the graviton, but to me it seems unlikely, although I'm young and essentially ...
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Charging a black hole?

What would happen if we have a black hole and we start shooting at it a single electron at a time, and go on doing it forever? Would the electrons start to bounce off eventually?
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Does rotational energy have effect on gravity/metric?

Intuitively, if energy can be stored in rotational motion, it has to obey $E=mc^2$. Does rotation of typical stellar-sized objects - BHs, pulsars, binaries - have measurable effect on their overall ...
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Possibility of “graviballs”?

Looking at the relevant wikipedia page, one can read that the graviton should be massless. Is it 100 % certain that it is massless or is there room in any "nonstandard" models for a tiny non-zero mass ...
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Event Horizon violability?

Is the "event horizon" of a black hole potentially violable? Black holes are commonly described as being unidirectional (matter / energy goes in, but doesn't come out), but is the event horizon of a ...
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Tidal force on far side

I have a question about tidal forces on the far side of a body experiencing gravitational attraction from another body. Let's assume we have two spherical bodies $A$ and $B$ whose centers are $D$ ...
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Without gravity, is there still up and down?

I'll try to be clear: example: If you send the ISS far enough for it not to undergo the Earth's gravity anymore, then you turn it and the—sleeping—astronauts in it upside down, when they wake up, will ...
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Why does gravitational collapse occur suddenly in a supernova progenitor?

I was reading the Wikipedia article on Supernovae, and it says that one of the reasons why a supernova occurs is due to sudden gravitational collapse when the core of the star has little fusable ...
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Do objects with mass “suck in” spacetime?

I don't really understand the general theory of relativity (GTR) really deeply, but according to my understanding, the GTR say that gravitation is caused by the curvature of spacetime by objects with ...
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Why doesn't my particle simulation end in a flat disc?

I've made a 3d particle simulator where particles are attracted to each other by the inverse of the square radius. The purpose of my experiment is to see if this alone would create a flat disk (like ...
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Quantum mechanical gravitational bound states

The quantum mechanics of Coloumb-force bound states of atomic nuclei and electrons lead to the extremely rich theory of molecules. In particular, I think the richness of the theory is related to the ...
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Physics and math behind flight through solar system: Where to start?

I wrote a first program that simulates a solar system. I was able to calculate the locations for every planet on its elliptical route for any given time. In a second program i managed to simulate ...
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Orbital mechanics and rocketry: Is it ever a good idea to intentionally lower periapsis?

tl;dr: Hohmann Transfer appears to be the optimal way to achieve a circular-to-circular orbit, but is it possible to lower the periapsis in order to achieve a more elliptical orbit with apoapsis at ...
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Why doesn't gravity ruin satellites?

Recently I watched a documentary about Io, a moon around Jupiter. Io has volcanic activity even though it is small and can't retain heat well because gravity from Jupiter and a nearby moon cause it to ...
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Why is $R^2$ gravity not unitary?

I have often heard that $R^2$ gravity (as studied by Stelle) is renormalisable but not unitary. My question is: what is it that causes the theory to suffer from problems with unitarity? My naive ...
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Gravity duals to Navier Stokes and interpretation of non linear contributions

I have been reading the paper The Incompressible Non-Relativistic Navier-Stokes Equation from Gravity. In it they state, "An instability, if it occurs, must necessarily break a symmetry ... ...
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Does conformal gravity explain the Bullet cluster lensing effects?

Conformal gravity is an "alternative" theory of gravity, where instead of using the Einstein-Hilbert action composed of the Ricci scalar, the square of the conformal Weyl tensor is used. It was ...
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What would gravity be like on a hemispherical planet?

On a hemispherical world half the size of Earth (ignoring that the planet should break apart and become a smaller sphere) what would the gravity be like? How would it change as you traveled from pole ...
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Alcubierre warp bubble effect on gravity and space

I read the question Faster-than-light communication using Alcubierre warp drive metric around a single qubit?, and these questions came to mind: What kind of impact would an Alcubierre warp bubble ...
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Why do 3d spheres and gravity tend to rotating discs on one plane?

Whether is it our solar system or a whole galaxy, there is usually a massive object (star or black hole) at the centre with gas and objects rotating around it. The gravitational effect of the ...
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Why is Higgs Boson given the name “The God Particle”?

Higgs Boson (messenger particle of Higgs field) accounts for inertial mass, not gravitational mass. So, how could it account for formation of universe as we know it today? I think, gravity accounts ...
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Noticing that Newtonian gravity and electrostatics are equivalent, is there also a relationship between the general relativity and electrodynamics?

In classical mechanics, we had Newton's law of gravity $F \propto \frac{Mm}{r^2}$. Because of this, all laws of classical electrostatics applied to classical gravity if we assumed that all charges ...