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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Though experiment in Quantum Gravity

Recent results show mean field games behaves as a quantum mechanical system. If we consider stellar systems like galaxies as a game with gravity between stars. nash equilibria will correspond to ...
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Variation with respect to the metric and other tensors

When varying an action with respect to tensors and the metric, I'm afraid I get confused as how to one organizes the Lagrangian and then performs the variation. Take for example, the following example ...
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What is space made of?

General Relativity posits that matter curves spacetime, such that geodesics point towards the object in question, hence, gravity. Now, how does matter do this? What is spacetime "made of", anyway, ...
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Universal Gravitation Vector Notation

I'm learning about astrodynamics on my own and I was wondering why the $r_{ij}$ is cubed in the vector notation for of Newton's Law of Universal Gravitation: $$F_g=(Gm_1m_2/(r_{ij})^3)r_{ij}$$ Here ...
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1answer
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Would a celestial body in a horseshoe orbit be tidally locked to the planet?

A smaller celestial body like a moon or an asteroid can be in a horseshoe orbit around a planet. Since it might go inside the tidal lock radius (but does not stay inside it all the time), during the ...
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2answers
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Why doesn't the gravitational force have a permittivity in its formula? [duplicate]

We know that the electrostatic force between two charges depends on the medium between the charges and its permittivity. Why, then, doesn't the gravitational force depend on the medium?
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1answer
145 views

Lenghthwise center of gravity of a boat based on flotation angle

I am trying to determine the center of gravity horizontally along the length of a pontoon boat so I can properly position the load on my lift. Approximate will do. It seems like an impossible question ...
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1answer
37 views

Charge without charge and non-traversable wormholes

My question concerns the theory proposed in this classic paper by Misner and Wheeler. In the paper, the authors propose the idea of "charge without charge"--namely, that positive and negative ...
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1answer
71 views

How much Gravity is required to stop time?

Clocks free of gravitational influence run faster than those experiencing gravity. Is it possible for gravitational influence to bring time to a stop? Additionally can acceleration affect clocks in ...
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Why do we say gravitational waves are analogous to sound?

In every popsci discussion of gravitational waves, the waves are said to be like "sound", and that gravitational waves allow us to "hear" the universe. Despite this, I have no idea how gravitational ...
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77 views

If we could perfectly control gravitational waves, could we play music with them? [closed]

Sound is just a kinetic wave propagating through a medium, right? In that case, if we had the ability to make gravitational waves exactly as we want them, could we play music to an observer some ...
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1answer
112 views

Unruh radiation and conservation of energy

Consider the Minkowski spacetime filled by some fields in their Minkowskian vaccum state. Now consider a Rindler observer carrying with him, say, one liter of water. According to Unruh formula, the ...
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3answers
258 views

Potential energy of springs and gravity, and work of a force

I am currently really stuck on this problem and I am not sure how to actually solve it, I think I can reason it out logically but I do not know how to show it. Here it is and under I will show what I ...
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How is the Earth moving in a elliptical orbit around the Sun? [duplicate]

If gravity is transmitted by a four-dimensional fabric of spacetime and the Sun creates a bend in it ,which causes planets to orbit it , shouldn't the planets move in a circular orbit around the Sun ...
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21 views

Is the self-interaction mass of a geon related to the mass gap? [on hold]

I wrote in the question about how type II and III solution have longitudinal components and are related to a geon. This mass has a similarity to the mass gap in gauge theories. In light of the ...
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30 views

Centrifugal force acting on Spacecraft

This Question may sound very naive. Still somebody can explain the basics in simple words. As I understand, when we equate the centrifugal force acting on spacecraft in circular orbit with ...
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345 views

What is the cause of gravitional force of attraction?

Ok,this is a silly question. But for quite long I have been thinking about this. What is gravitation all about?? My book directly writes since force of gravitation is directly proportional to the ...
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1answer
56 views

What type of instrument can I use to determine my current distance from the center point of Earth?

Immediately, I think of a scale, but is there better way? I can only imagine weighing an object of known mass with an extremely precise scale. I am asking because I would like to be able to address ...
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257 views

The ADM Energy of Gravitational Waves?

I have been looking for books about this question for several days. However, almost all books use Landau–Lifshitz pseudotensor to calculate the energy of Gravitational Waves.And they said the result ...
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Will this approach to gauge-gravity duality work? [closed]

This is a question on whether quantum gravity has an internal symmetry structure given by gauge fields. I set up the basics of the idea first. Let us consider the complex 3-dim space $E^3$ with the ...
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5answers
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Can a black hole collapse in itself?

As we know that the black hole is a lump of highly dense matter, and that's the reason for it's so strong gravitational force. Bat let us assume that it has sucked up a huge amount of mass and it's ...
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1answer
63 views

Are the Schwarzschild metric and the Geodesic Equation relevant in the context of the Earth? [closed]

The geodesic equation used in general relativity is the following: $$ {\mathrm d^2 x^\mu \over \mathrm ds^2} =- \Gamma^\mu {}_{\alpha \beta}{\mathrm d x^\alpha \over\mathrm ds}{\mathrm d x^\beta ...
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2answers
115 views

Gravitational waves in other dimensions

I know this question is purely speculative, as we don't know if more dimensions do exist and also we do not know if gravity is indeed stronger in other dimensions (if they were to exist). But, one of ...
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Do we have theories about why gravity exists/how it works?

For years I have been very fascinated by the "mystery" aspect of gravity. Functionally, we understand it for our applications, but in my (limited to my 3 quarters of undergrad general physics) ...
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4answers
592 views

Can the gravitational constant $G$ be calculated theoretically?

We know all that the gravitational constant is $$G=6.67428±0.00067\times 10^{-11}\mathrm{m^{3} \:kg^{-1} s^{-2}}.$$ But can we calculate it theoretically?
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2answers
107 views

Are electron densities and electrostatic forces possibly responsible for gravity? [closed]

The idea I had was that whilst electrons usually orbit within the Bohr radius of atoms there is a chance of them appearing significantly further away than that, meaning that if all the electrons in ...
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Can we “see” into a black hole using gravity?

I believe the "no hair" theorem means all black holes settle down into a state only determined by a few parameters, typically listed as mass, charge and angular momentum. But I don't think they can ...
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What is the direction of buoyancy in the bulk of liquid on earth?

I have a trouble when considering the direction of buoyancy in the bulk of liquid subjected to vertical temperature gradient. The liquid is heated from below or above that induces a natural convection ...
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How can we recover the Newtonian gravitational potential from the metric of general relativity?

The Newtonian description of gravity can be formulated in terms of a potential function $\phi$ whose partial derivatives give the acceleration: ...
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1answer
35 views

Can random human have influence on position of someone(far away), when jumping?

Let's say there is a way to get position of all particles of human with perfect accuracy. When random human jumps, can it alter position of someone who is on the other end of earth?
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1answer
58 views

Schwarzschild metric black hole

Schwarzschild metric solution presents two singularities. An apparent one at $r=2GM$ and a real one at $r=0$. It is known that everything freezes at the event horizon from an outside observer point of ...
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1answer
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Is it contradictory with any theory or experimental result to have a negative gravitational force mass?

I am aware that there are many similar questions here about this in this site, but most answers concentrate on negative inertial and gravitational energy. My question is more specific. QM together ...
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1answer
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Does an object creates gravitational waves when only accelerating in one direction?

I know from reading about the gravitational waves detected by Ligo, that when an object has angular acceleration, it produces gravitational waves. I'm wondering if an object creates gravitational ...
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Trying to understand Newtonian limit of GR

First ever post - please be kind. I'm trying to understand how General Relativity becomes equivalent to Newton's laws of motion, plus Newton's law of gravitational attraction in the limiting case of ...
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1answer
63 views

Do gravitational waves radiate isotropically?

Do gravitational waves radiate equally in all directions? If so, is this an inherent property of all gravitational waves or is it just due to how they are normally produced? In other words, in a ...
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15answers
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How does gravity escape a black hole?

My understanding is that light can not escape from within a black hole (within the event horizon). I've also heard that information cannot propagate faster than the speed of light. It would seem to ...
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Prospects for detection of gravitons?

With the announcement of the detection of gravitational waves, questions about the implications proliferate. Some relate to the possible existence of gravitons. The analogous relationship between ...
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LIGO Gravitational Wave Discovery and Gravitons [duplicate]

Now that gravitational waves have been detected, how hard will it be to detect a graviton? Will the equipment have to be more sensitive or are the difficulties more complicated than that?
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Stretching of spacetime

If spacetime is being stretched because of dark energy and dark matter, than, wont the sinks of gravity be filled up? For example, you have a square sheet of fabric(spacetime) and four people are ...
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2answers
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Why does gravity have such an insignificant effect on particles at an atomic scale?

E.g. why do we experience gravity all the time, but on an atomic scale, the gravitational forces are so small?
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1answer
39 views

Identify binary stars in nbody simulation

I'm doing a nbody simulation, and I'm interested in the formation of binary systems in the temporal evolution. I can identify them by eye, but I don't know an algoritmic criteria that can say me if ...
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Gravitation and gravity

Are gravity and gravitation the same thing? Actually I have 2 teachers at my school. One of the said that gravitation is the force of attraction between any two bodies in the universe due to their ...
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What is the speed of gravity [duplicate]

Is there a definite answer to what is the speed of gravity? I get conflicting answers when researching this question By what possible means could it be tested?
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1answer
42 views

What relative effects be for object with near light speed velocity in compactified dimensions?

What relative effects be for an object with near light speed velocity in compactified dimensions? Does gravity increase the same as for an object with near light speed velocity in usual spacial ...
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3answers
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Is there a center of gravity in black hole?

I've come across this particular gif "http://i.imgur.com/AOCqg5j.gifv" If you can see the above gif, you can see the two perfectly spherical black holes merge together forming a single larger ...
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At what rate do gravitational waves lose energy and amplitude?

Part 1: How do gravitational waves decay with distance? My Newtonian instincts tell me that gravitational waves would likely decay in the same way that Newtonian gravity decays, but at this point ...
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How is light affected by gravity?

Light is clearly affected by gravity, just think about a black hole, but light supposedly has no mass and gravity only affects objects with mass. On the other hand, if light does have mass then ...
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Why is it that light bends towards gravity when it has no mass at all? [duplicate]

Why is it that light bends towards gravity when it has no mass at all? Is it because of how gravity behaves as mentioned in general relativity? As far as I know, light cannot escape from black holes, ...
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4answers
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Theory that gets rid of dark matter/energy

Is there any physics theory that either groups together gravity and dark energy/dark matter or eliminates dark energy/dark matter by modifying standard understanding of gravity or any force? If so, ...
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Calculate the magnitude of the acceleration due to gravity including its uncertainty?

I made a free fall time experiment and now I'm trying to make a report. The experiment consists of releasing a steel ball from various heights hi and measuring corresponding free fall times τi . ...