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 do you travel in a circular orbit around a massive body?

I am trying to figure out how an object could achieve a perfectly circular orbit. Given a mass for the planet or other body the object is orbiting and a distance from the center of mass, how fast ...
3
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3answers
180 views

What would be the effect on gravity if space expanded at > $c$?

If space were to expand at > $c$ (as in inflation) would that mean gravity would no longer have any effect on the curvature of space, since gravity can only propagate at $c$?
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1answer
125 views

Is the gravity between objects other than celestials observable? [duplicate]

I've always read that all matter has gravity. But, can we observe it? I mean, The Earth pulls us but what about small daily objects? For example, if we release 2 small objects in space, do they get ...
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1answer
2k views

Is it possible to create artificial gravity by magnetizing iron in the blood stream?

I have been thinking is it possible that using a rather strong magnet on the human body's blood stream we could enact a small case of artificial gravity on the human body via the iron in the ...
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3answers
321 views

General relativity theory [duplicate]

As I understand general relativity theory (please correct me if I'm wrong), time becomes dilated and space becomes compressed around mass, and this is responsible for gravity. I'm struggling with ...
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3answers
4k views

What happens after a rocket is fired with velocity equal to or greater than escape velocity? [closed]

When a rocket is fired a speed greater than or equal to escape velocity, then it does not have any gravity effect of the earth. So, suppose if a rocket is having that much energy which will only last ...
14
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3answers
3k views

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 extended)...
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3answers
554 views

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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1answer
118 views

Has anyone measure the strength of the force of gravity in relation to the molecular bonding? [closed]

It's clear to me that gravity it a function of mass. It is also clear to me that gasses are less affected by gravity. So I'm thinking that there exists a measurable minimum binding distance $d$ ...
4
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3answers
298 views

Basic Question About General Relativity?

I'm a layman that loves Physics. I'm also horrible at math. Having said that I have many, many questions in regards to physics and General Relativity in-particular. I will try to keep my question(s) ...
2
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1answer
142 views

Is the Higgs field really disconnected from gravity?

I would like to understand better the role of Higgs mass in the gravitational interaction. I read here in some posts, that the Higgs mass has nothing to do with gravitation. Is it justified to say ...
2
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2answers
219 views

Barbells and gravity

A giant set of bar bells floating in space (like two identical sized planets connected by a long rod) would have a centre of mass midway between the two on the connecting rod. But surely it would ...
21
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2answers
1k views

How do spiral arms form?

Why aren't all spinning galaxies shaped as discs as my young mind would expect? I understand how the innermost parts of a galaxy spin faster than the outer parts, and that could explain why some ...
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1answer
158 views

Closed form for shape/tension of an elastic cable slung between two points

Given the 2D coordinates of two points, $a$ and $b$, between which an elastic cable of known length, $l$, mass per unit length, $m$, and the spring constant, $e$, is slung, I need to compute the shape ...
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0answers
37 views

what is the speed of gravitational interactions? [duplicate]

Example. Two bodies with masses m1 and m2 distance between them one year of light. What happens to the force of attraction between the two bodies when one body suddenly disappears? Is the force ...
6
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1answer
962 views

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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2answers
360 views

Gravity in the center of a hollow neutron star [duplicate]

Imagine a hollow 100 metre diameter (for example) sphere made of incredible dense material (ie neutron star dust etc) but is self supporting (ie the central cavity). Assuming that the sphere skin is ...
2
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2answers
1k views

Can the mass of an orbiting object and the object being orbited be determined by the distance and orbit velocity alone? [duplicate]

This question is the inverse of: "Could an object orbit while moving at twice the speed, but at the same distance, if it had half the mass?" I'm curious about the nature of orbits, but am not well ...
0
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3answers
179 views

Understanding black holes [closed]

Basically I don't know anything about Physics but I am really curious about all these things. I was trying to understand what is a black hole, but unfortunately I couldn't figure out from online ...
0
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1answer
463 views

How could vacuum energy cause the expansion of the universe? [duplicate]

Is it by gravity? How could gravity produce a repulsive force?
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2answers
705 views

In which direction do gravitons travel? Do they originate from mass or are they collected by masses?

This is a kind of silly question, that mostly goes unanswered: are gravitons detatched from the objects they act on, like photons in free space. Maybe gravity or gravitons are collected by mass (...
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2answers
10k views

Is there a way to fill Tank 2 from Tank 1 through Gravity alone?

I am a newbie in water system design but I am currently faced with the exact situation below on my land, and I need to know whether gravity alone is sufficient in order to fill Tank 2 from Tank 1, as ...
18
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2answers
1k views

Is Newton's universal gravitational constant the inverse of permittivity of mass in vacuum?

Is it possible to consider Newton's universal gravitational constant, $G$, as inverse of vacuum permittivity of mass? $$\epsilon_m=\frac {1}{4\pi G}$$ if so, then vacuum permeability of mass will be:...
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1answer
970 views

Negative Energy and Wormholes

Apparently to create wormholes you need negative energy/matter. Say you had negative matter/energy, how would it be applied towards making a wormhole?
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1answer
1k views

Gravitational Field from Irregular Object

How does one calculate the gravitational field of an irregularly shaped object? I was thinking specifically of the gravitational field due to a human, and tried to see if modeling a human as an ...
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0answers
879 views

Map of the gravitational strength of the solar system

I am looking for a map or plot of the gravitational strength in the solar system. In an ideal world there should be something like google earth to move around in the solar system, zoom in and out and ...
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0answers
102 views

Would a closed field of gravity neccesarily lead to paradoxes?

I've asked wether artificial gravity, as seen in some SF-Movies, would violate known laws of physics. To recap, my idea of an Artificial Gravity (AG) system was like this: A Device that creates an '...
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0answers
53 views

Gravity Interaction versus Gravity Well

This question may be misguided, but bear with me. Is there such a thing as gravitational 'invisibility', and if so, is it comparable to optical invisibility (photons/gravitons 'continue' in their ...
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1answer
116 views

Expressing a force in components [closed]

If there is an object on some ramp, how do I express its weight in terms of vectors orthogonal and parallel to the ramp surface? For example, if the object has a weight $\vec W=m\vec g$, then how do ...
6
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2answers
339 views

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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1answer
261 views

Mass - Gravitational pull - centrifugal force

In relation to mass/gravitational/centrifugal force. Is the increased gravitational force due to the increase in mass of a planet (i.e. earth) from meteorites, etc.. directly proportional to the ...
6
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1answer
385 views

Einstein action as a functional of the tetrad (first order formulation of gravity)

Let the Einstein-Hilbert action be rewritten as a functional of the tetrad $e$ (units shall be set to $1$) such that $S_{EH}(e)=\int \frac{1}{2}\epsilon_{IJKL}~e^I\wedge e^J\wedge F^{KL}(\omega(e))$, ...
30
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2answers
1k views

What forces are at work causing sand to migrate to the centre of a spinning bucket of water? [duplicate]

A bucket is filled with water and a handful of sand. The water is then spun. Why and what forces are in play which cause the sand particles to congregate in the centre of the bucket?
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0answers
32 views

Graviton through the horizon and force felt outside a black hole [duplicate]

Gravitational force is mediated by graviton exchange. If I am standing outside a black hole, I can of course feel the attracting force towards the black hole. This should correspond to gravitons ...
0
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1answer
204 views

the higher you go the slower is ageing [duplicate]

as per to einstein as we go far from the earth the TIME tends to slow down , so it means when I am one metre above the earth's surface , the time has slow down for me as per http://en.wikipedia.org/...
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1answer
368 views

Gravity is an intrinsic property of every atoms? [closed]

If gravity is the force of attraction between masses, does this force is an intrinsic property of every atoms? Is there any possibility of some other particles within atom which is yet to be ...
0
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2answers
3k views

Is there a relation between the magnetic field force of the earth and the gravitational force between the earth and other bodies? [closed]

According to Newton's Universal Law of gravitation, we can say that a huge body of mass will attract another body of mass within a short range, however, if both bodies are for instance magnetic, ...
11
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3answers
651 views

Can we disprove Artificial Gravity (like in the movies) with a thought experiment?

Suppose you have a Device that creates an 'artificial gravity' (AG) inside a Box, with these properties: the system does not use inertial forces (like centrifugal force) or a huge mass to create AG ...
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4answers
1k views

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 systems,...
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5answers
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What happens with the force of gravity when the distance between two objects is 0?

so I had my first approximation to the gravity equation \begin{equation} F=GmM/r^2 \end{equation} and some questions arose that my teacher couldnt respond: if r approximates to 0 with mM being ...
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1answer
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Can one black hole suck in another black hole?

In the recent news, scientists at NASA have found “unprecedented” black hole cluster near Andromeda’s central bulge. I wonder why doesn't all these black holes merge and such each other in until just ...
0
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1answer
318 views

is gravitational force dependent on objects radius?

I was told that objects with the same mass but different sizes (or densities) will have a different gravitational pull. Is this true? If so, why?
2
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2answers
284 views

How did the scientific community receive this measurement of speed of gravity

This link and this one concern a recent measurement, by Chinese scientists, of the speed of gravity using Earth tides. They find it is consistent with a speed equal with the speed of light, with an ...
6
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2answers
820 views

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 ...
2
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2answers
245 views

Properties of gravity

If all objects in the solar system suddenly went cold to the core, including the Sun, would it gravity play any different role? I guess what i am trying to ask, is there any relation between energy ...
2
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3answers
3k views

How does energy convert to matter? [duplicate]

To my understanding, matter and energy are one and the same. Shifting from $E$ to $M$ in Einstein's famous equation requires only a large negative acceleration. If $M$ really is $E/c^2$, does that ...
0
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2answers
68 views

Expected behavior of the gravity under some experiment [duplicate]

I would like to know the expected behavior of the Gravity under the following mentioned imaginary experiment: What if we dig a well or a boar or a straight hole (say, its diameter is 100 meter) ...
5
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1answer
751 views

Physics of donut magnets levitating vertically on a pencil?

When you put identical donut magnets on a pencil horizontally, the magnets all repel from each other in a way that creates equal spacing between each magnet. However, spacing is not equal when the ...
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1answer
347 views

Simple pendulum and planet mass [closed]

A simple pendulum, $20cm$ in length, has the period of $2.7s$ on a certain planet. Find the mass of the planet if its diameter is $18000km$. $G=6.67\times10^{-11}Nm^2/kg^2 $ I have no idea how to get ...
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1answer
357 views

Solving equation of motion of two massive particle exerting the gravitational force each other

I'm trying to analyze the motion of the particles which exert the gravitational force each other. Let $M_1$, $M_2$ be the masses of the particles, and the equation of motion of particle $M_1$ $$ F=G\...