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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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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Where does gravity get its energy from?

I would like to know where gravity gets its energy to attract physical bodies? I know that the law of conservation states that total energy of an isolated system cannot change. So gravity has to be ...
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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 ...
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Is it possible to have a floating bullet in the air?

I've been asking myself a question for quite some time : say that a bullet gets out of a gun at 900 km/h (I'm european, hence the metric system). say a train could go in a straight line at 900 km/h ...
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Why can't a rope be pulled completely straight?

I have found several discussions on how to calculate the sag of rope that is tied off at two points (like a tightrope), and I understand it to a certain extent. What I can't wrap my head around is how ...
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Is there any anti-gravity material?

I want to know if there is any anti-gravity material. I am thinking of making flying vehicles which are made up of anti-gravity material so that they will not experience any gravity on them and can ...
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Electrical force vs gravitational force

Given that the electrical force is so much stronger than gravitational force at atomic levels, why is it that it's the gravitational force between you and the earth that keeps you on the ground rather ...
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The Sun as a gravitational lens

Since the Sun is a gravitational lens with as focal length of 550 AU for visible light, with an immense amplification factor, shouldn't it light up objects hanging out there? We should get solar ...
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What is the medium that allows magnetic fields *or any forcefield* to exist?

Magnetic fields are obvious distortions.. of.. something, but what exactly are they distortions of? Massive objects produce curvatures/gradients in space-time resulting in what we observe as ...
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Why do we weigh less when falling?

I don't want to go to science world to find out because it would be a long round-trip. I understand that acceleration/deceleration would effect the weight and I can also imagine that someone at ...
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Why do liquids separate in space?

I've seen videos of people in space (on ISS) who squeeze a bottle or something and liquid comes out, it then separates into smaller balls. Why is this surely it should stay pretty much together ...
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If gravity is a bend in Space-time then what is magnetism?

Einstein postulated that gravity bends the geometry of space-time then what does magnetism do in to the geometry of space-time, or is there even a correlation between space-time geometry and ...
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Do residents of the Hudson Bay area have more time?

Apparently there is a gravity anomaly in the Hudson Bay Area in Canada: gravity is "missing" or it is slightly less than it is in the rest of the world. Does that mean that things in the Hudson Bay ...
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Does the conversion of crude oil to greenhouse gases have any measurable effect on earth's gravitational pull?

Oil underground is much denser than greenhouse gas in the atmosphere. Does the conversion in anyway effect the gravitational force from earth.
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Practical limits on the size of orbiting objects: could two pebbles orbit each other

As I understand it, gravity is inherent to mass and therefore even a small rock has its own gravitational pull. It seems entirely plausible then that a rock 1" in diameter could orbit a bigger rock, ...
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What is the escape velocity of a Black Hole?

The escape velocity of Earth is $v=\sqrt{\frac {2GM}{R}}$, where $M$ is the mass of the Earth and $R$ it's radius (approximating it as a sphere), and is much less than light speed $c$. But I want to ...
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Why do helium filled balloons move away from the Earth?

From my understanding objects do not fall but are pulled to the earth from gravity. With this in mind, I can't understand why if helium filled balloons are not pulled by gravity then shouldn't they ...
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What is the largest sphere of liquid water that could exist in space held together under it's own gravity? [duplicate]

What is the largest theoretical sphere of liquid water that could exist in space held together under it's own gravity? I've always wondered if a planet the size of earth could exist as a single volume ...
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If the Moon had gravity as good as the Earth and a magnetic field could it have supported life?

If the Moon had gravity as good as Earth and a magnetic field could it have supported life? Because if the Moon had gravity, it could have retained water more than is present today on the surface. ...
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Calculating gravity when taking into account the change of gravitational force

This is a problem that has bothered me for a couple of weeks now, and I can't seem to wrap my head around it and understand it. Let's say we have a planet with a mass of m. We also have an object of ...
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How to debunk 'The Electric Universe'?

My father is a generally intelligent person, however he has latched onto a theory which I believe to be completely incorrect. He doesn't believe in gravity, but rather subscribes to an 'Electrical ...
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Escape Velocity of Asteriod 243 Ida

I was reading about this asteroid (apparently, it has a moon, isn't that awesome?) and I started thinking about if I was on this asteroid, and I jumped, would I fall off? It's been a while since I ...
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gravitational waves and inflation theory

I am not a technical guy and I have no scientific knowloedge in physics but I have been reading books, watching videos in order to understand our cosmology and ...
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Gravitation is not force?

Einstein said that gravity can be looked at as curvature in space- time and not as a force that is acting between bodies. (Actually what Einstein said was that gravity was curvature in space-time and ...
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How long will my fridge magnet stay attached to my fridge?

I have a 500 gram neodymium magnet. It is stuck to my fridge. With the constant pull of gravity trying to pull it off how long would it stay attached to fridge? For arguments sake lets say my fridge ...
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Why can't airplanes just keep going up? [duplicate]

Possible Duplicate: Why do space crafts take off with rockets instead of just ascending like an aircraft until they reach space? Ignoring that the engines only work in air, so say its a ...
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Can light affect gravity? [closed]

I have a mentor at work, who wrote a paper in the past regarding light and relativity. I am an aerospace engineer by training and a system administrator/programmer by trade, so I know a little bit ...
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Naive quantum gravity

My question involves an analogy I have to point out. Consider the Lagrangian density for the a complex scalar field: \begin{equation} ...
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Does gas spread out equally everywhere?

An excerpt from this page: Gases can fill a container of any size or shape. It doesn't even matter how big the container is. The molecules still spread out to fill the whole space equally. That is ...
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A Hollow Black Hole

I was just reading a question about the gravity inside a hollow neutron star. It was a trivial question, obviously there is no force felt. But then it got me thinking. Suppose you had a hollow sphere ...
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Could we prove that neutrinos have mass by measuring their gravitational signature?

It is now said that neutrinos have mass. If an object has mass then it also emits a gravitational field. I appreciate the neutrinos mass is predicted to be small, but as there are so many produced ...
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What does it mean for objects to follow the curvature of space?

In science documentaries that touch on general relativity, it is often said that gravitational pull isn't an actual a pull (as described by classical physics), but rather one body travelling in a ...
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Does heat from gravitational pressure dissipate eventually?

It's my understanding that Earth's core is hot and molten because of the high pressure from gravity compressing the planet's mass towards the center. How does this heat reconcile with thermodynamics, ...
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Alternate layman's metaphors for illustrating curved space-time

The metaphor of a surface (typically a pool table or a trampoline) distorted by a massive object is commonly used as a metaphor for illustrating gravitationally induced space-time curvature. But as ...
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What makes General Relativity conformal variant?

I have a question regarding the well known fact that General Relativity is not a conformal invariant theory or to put it in other words about the fact that it is conformal variant: What are the ...
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Does the mass of a star change as it collapses into a black hole?

I know (I think!) that when a really big star collapses on itself it creates a black hole. My question: When a star collapses, is the mass equal to the mass of the star when it's not a black hole? Or ...
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Has anyone tried to do Galileo's tower of Pisa experiment at a molecular or atomic scale

Galileo is reputed to have demonstrated that unequal masses fall at an equal rate by dropping them off the tower of Pisa and observing that they hit the ground simultaneously. Has anyone tried to push ...
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Calculating Orbital Vectors in the Future

For the 2D space simulator that I am writing (please note, it is not at all homework), I require formulas that will give me the location and velocity of a spaceship, relative to the parent celestial ...
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What causes matter to initially rotate/spin/orbit?

What causes matter to initially rotate/spin/orbit? All I can find is the statement that in space particles of dust/gas/matter contract into a spinning disk due to gravity (to form stars, solar ...
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Given finite speed of gravity, why didn't Earth fell into the Sun already?

When Sun and Earth are moving, at each moment $t$ they are attracted not to the current position of each other, but to the position of each other at $t-\Delta t$, where $\Delta t$ is the time required ...
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How general relativity gets to an inverse-square law

I understand that a general interpretation of the $1/r^2$ interactions is that virtual particles are exchanged, and to conserve their flux through spheres of different radii, one must assume the ...
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What is the fastest a spacecraft can get using gravity-assist?

Assuming normal spacecraft and space objects (no neutron stars, black holes, etc). To what speed can a spacecraft accelerate using gravity-assist? For example, if a spacecraft is moving at ...
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The analogy between temperature and imaginary time

There are many statements about the relation between time and temperature in statistical physics and quantum field theory, the basic idea is to interpret (inverse) temperature in statistics as "time" ...
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Incompatibility Between Relativity and Quantum Mechanics

Why does Gravity distort space and time while the electromagnetic, strong, and weak forces do not? Does this have to do with why Quantum Mechanics and Relativity are incompatible?
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Can Black Holes be the Dark Matter?

Seems to fit the definition: interacts with gravity, doesn’t radiate energy (except Hawking Radiation) and could create gravity lensing without absorbing very much of the light. Could 80% of the ...