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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The original thorium reactor?

With lunar thorium being common, and heavier than iron or nickel, does earth's core have the the occasional nuclear reaction?
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Could a really tall tube suck garbage in to space?

When I was around 10 years old, I had this idea that was supposed to solve our waste problems; I imagined having tubes miles high that would stretch in to space. Every tube would have a door at the ...
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Visualizing gravity in 3D

We've all seen the depiction of gravity bending space downwards, and so attracting objects into the dent it creates, cf. e.g. this and this Phys.SE posts. That's intuitive and makes a lot of sense, ...
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259 views

What is gravity and what causes objects to act against it?

So I understand the concept of gravity, in that it's not actually a force, but more of a displacement in the spacetime grid. An object with a big enough mass will bend the spacetime, causing smaller ...
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Monopole Gravitational waves exist?

GR says that monopole gravitational radiation does not exist. I understand the reasons for this. However there is this effect (which seems to me to have the hallmarks of a wave). Paper at arXiv: ...
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57 views

Is gravity really well described? [on hold]

From what I know, gravity is a natural phenomenon by which all physical bodies attract each other. I'm wondering, however, about the nature of the gravity theory. As established in the definition, ...
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When objects fall along geodesic paths of curved space-time, why is there no force acting on them?

On cseligman.com, it is written that So, we see things falling with an acceleration which we call the acceleration of gravity,and thinking that we live in a straight line , uniformly moving or ...
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Is gravity a centripetal force?

In curved space-time, there are curved paths. Since curved paths in our experience require some centripetal force to create them, isn't then gravity a centripetal force?
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42 views

Gravitational… confinement?

This is a followup to Ergil's question "Weak isospin confinement?". According to the Wikipedia article on color confinement: The current theory is that confinement is due to the ...
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75 views

Why does the motion of the planet around a star cause a centrifugal force?

Please consider the differences in Newtonian physics and general relativity. Newtonian physics In Newtonian physics it makes sense that objects placed on a planets surface facing away from the ...
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Does uniform distribution of background matter affect the dynamics of a gravitational system?

Situation 1: A test particle of mass m moves around a big mass M in a Keplerian orbit. The orbital period is easily found, given certain initial conditions. Situation 2: The same system of two bodies ...
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Electromagnetic radiation bending on Earth

Most articles say that a radiowave is able to propagate itself beyond the horizon because it is reflected off by the ionosphere (and the Earth itself). But do radio waves also get bent according to ...
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Antimatter traveling back in time and gravity [duplicate]

I've been reading on the construct of considering antimatter as matter traveling backward in time, which seems like an useful tool. There seems to be some discussion around this concept, if ...
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How would gravitons couple to the Stress-Energy tensor?

How would gravitons couple to the Stress-Energy tensor $T^{\mu\nu}$? How did physicists arrive at this result? I've read that it follows from the analysis of irreducible representations of the ...
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Does light or waves have any kind of mass? [duplicate]

Just like the previous question, Even I have been studying Hawking's A Brief History Of Time and even I was thinking of Einstein's General Relativity. But I was unable to accept his view of GRAVITY. ...
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How can magic be explained with Physics? [closed]

Assuming that, hypothetically, and for this example only, "magic" means things like magical powers. In movies, games, etc. we witness magic; however, it's never explained how it works with regards ...
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Questioning Einstein's view on gravity [duplicate]

Oke, so my mind is blown by Einsteins view on gravity, at least as far as I understand the basics and principles he based his views on. One of the first things that struck me was that most of his ...
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In reverse time, do objects at rest fall upwards?

I want to develop a game where time runs backwards, based on the idea that physical laws are reversible in time. However, when I have objects at rest on the earth, having gravity run backwards would ...
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How do you find the tension in the real world? (Given a rope in a pulley system)

I'm well aware of the formula to calculate tension, however, given a real world situation where you have a closed pulley system. How do you measure the force (i.e., tension) required to pull on the ...
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Is gravitational Chern-Simons action “topological” or not?

Here are the 2+1D gravitational Chern-Simons action of the connection $\Gamma$ or spin-connection: $$ S=\int\Gamma\wedge\mathrm{d}\Gamma + \frac{2}{3}\Gamma\wedge\Gamma\wedge\Gamma \tag{a} $$ $$ ...
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91 views

If an airplane is flying sideways, is it in free fall?

If a plane turns 90 degrees such that it is flying sideways, is it accelerating towards the earth at the usual 9.8 m/s^2? My guess is that the plane must be in free fall because I don't see what ...
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How possible is it that the Large Hadron Collider (LHC) on its second try, could disrupt the gravity of Earth?

How possible is it that the Large Hadron Collider, on its second try, could disrupt the gravity of Earth?
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Why the gravitational force is 10^38 times smaller then the strong nuclear force?

and the weak interaction force is $$10^7$$ times smaller then the strong nuclear force? Why exists this comparison?
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What would happen if a negative mass crossed the event horizon of a black hole?

If negative mass really existed and somehow a very fast traveling negative mass object reached near the black hole's event horizon. What would happen when it crosses the event horizon? According to ...
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Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth? [duplicate]

Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth? According to a detailed analysis by Dave Typinski, Marvin the Martian’s Illudium Q-36 ...
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80 views

How can gravity truly be infinite?

From my knowledge, gravity is infinite and extends throughout all of space. It diminishes as distance increases but is still present everywhere. So given enough time, no matter where something is in ...
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Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth?

According to a detailed analysis by Dave Typinski, Marvin the Martian’s Illudium Q-36 Explosive Space Modulator will require $1.711 \cdot 10^{32}~\text{J}$ to shatter the Earth into a gravitationally ...
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Where did the energy released due to gravitational binding energy of the Earth go?

The gravitational binding energy of the Earth is $2×10^{32} J $, so the same amount of energy must have been released during the Earth's history. According to this and this, the current internal ...
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22 views

How would gravitons be detected? [duplicate]

How would gravitons be detected indirectly or directly, in space or on earth? And what experiments are going on to find gravitons?
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116 views

How much pressure does the earth's central atom experience?

If mass is distributed evenly about it: "central atom", then it should be weightless right? If reasonably so, does it still experience the pressure? I would like to calculate, but I'm not so ...
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59 views

Where does gravity originate?

Does it emanate strictly from energy dense regions of space? What does that mean? Is it possible to, say, arrange clumps of matter in such a way as to create a virtual gravity well in space where ...
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Can very large objects have a gravitational moment?

I was reading this answer about center of gravity vs. center of mass and it stated: Consider the Sears Tower. Its CG is about 1 millimeter below its CM. The reason why is because the base of the ...
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24 views

Does gravity affect water permeability?

Suppose I have an approximately rectangular prism composed entirely of folded paper. If I place 600lbs on top of these rectangular sheets of paper, the paper should compress. How does this affect ...
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79 views

Would a six-inch person face certain death when falling from a great height?

In Mary Norton's The Borrowers Aloft, the borrowers are like humans in every way except size - normal adult height is six inches. One family of three is captured by a human couple and housed in an ...
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Pendulum's motion

Consider a pendulum in it's balance point hanging from ceiling. It can swing in all the directions in the space. The pendulum can only swing in a sphere(the string can't bend). Now, is it possible to ...
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Initial Velocity For Orbital (Gravity) Slingshot At Hit Moving Target

In this problem we have three masses, Mass A is on the left side of the sun Mass B is the sun, and Mass C is on the right side of the sun. I want to calculate the initial velocity of Mass A to hit ...
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Calculate Initial Velocity For Orbital (Gravity) Slingshot

I am trying to find the initial velocity to slingshot a planet around the sun and through a gap. The green ball is the planet, and the yellow ball is the sun. In this trial I need to get the ...
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Does graviton loops affect the seperately covariant conservation of energy momentum of two noninteracting sectors of matter

Consider the action $$\int \sqrt{-g}\left[R[g]+\mathcal{L}_{m1}(g,\psi_1)+\mathcal{L}_{m2}(g,\psi_2)\right]$$ Classically we have $$\nabla^\mu T^1{}_{\mu\nu}=0,\,\,\,\,\nabla^\mu T^2{}_{\mu\nu}=0$$ ...
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What Is the Physics principle behind dropping a stone into a cup of water?

I have been doing an experiment about relationship between drop height of a stone and the loss of water in the cup it lands in. I found that after dropping the same stone into a cup with the same ...
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What is the difference between Saddle points and Lagrangian points between Earth and the Sun?

I am studying MOND bubble effects in the Solar System (Paper). In "mond habitats.." (last reference) first page, the author says MOND bubbles reside on the saddle points but I fail to understand the ...
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If a graviton is in the atom then why does matter with more atoms still fall at the same rate?

If a graviton is in the atom then why does matter with more atoms still fall at the same rate? Could it be possible that all atoms are expanding and thus creating an illusion of attraction? ...
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How Earth's Gravity is more powerful than its centrifugal force?

How Earth's Gravity more powerful than centrifugal force? The earth spins all the time but we are not holding onto something to avoid drifting off in space cause of the centrifugal force.
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Coulomb's Law in the presence of a strong gravitational field

I was under the impression that the $1/r^2$ falloff of various forces were because of the way the area of a expanding sphere scales. But that strict $1/r^2$ falloff would only be globally true in a ...
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Energy loss through gravity and the law of conservation of energy

Since every object exerts a force of gravity on all objects around it, how can it lose so much energy at all times without ever stopping? If an object always loses energy from gravity, how does it ...
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Why does gravitational singularity break the laws of physics?

I am assuming there are two constituents that obliterate our current model of physics; that it's infinitely dense that it's infinitely small Please correct me if I am wrong.
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How does gravity bend light [duplicate]

Assuming photons have no mass, as I believe they don't, how does gravity affect photons in order to bend them?
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42 views

What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...
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Is there a peak gravitational force between bodies?

Suppose Object A is exerting gravitational force on Object B. Object A increases in mass, and so increases in volume, increasing the gravitational force on Object B. But, since mass occupies space the ...
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How does momentum effect velocity? [duplicate]

I'm in AP physics and we haven't even covered this yet so sorry if my question seems strange... I know $p = m v$, However right now I am writing a 2D physics engine and I am having some trouble with ...
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Visualizing bending of Spacetime around a heavy object

The commonly used example of viewing bent SpaceTime around a heavy object such as the Sun is the Trampoline. However, this image is limited as it shows only the bending below the Sun. What about the ...