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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Repulsive gravity [duplicate]

IANAP, so feel free to berate me for thinking apocryphal thoughts! Just as magnetism has two charges, in which particles of like-charge repulse and particles of dissimilar charge attract, might ...
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Does gravity affect radiation incident on the planet?

Just curious ... Known facts: When outside the atmosphere levels of radiation are higher Typically such radiation is CBR, Solar Radiation Question: If the matter of the atmosphere and ...
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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 ...
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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 ...
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What truly is mass, and is there a direct way to measure it?

We know a mass of an object of one kilogram as an object that weighs W = mg = 9.8 N and we reference it to that, (when it should as a fundamental parameter describe weight not the opposite). But if we ...
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Does gravity affects temperature reading of a mercury thermometer?

I remember when I was in primary school, the science teacher put me in charge of a mercury thermometer. I do not quite understand the mechanics behind except that mercury expands when it is hot and ...
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Constructing an orbital trajectory that quickly returns to its origin

I'm working on a science fiction story that involves two spaceships engaged in combat while in orbit around a planetoid. My original idea called for spaceship A to trick spaceship B into firing a ...
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220 views

Will photon's energy be exactly same after million years?

If photon will travel for million years without collisions, what subtle effects can be accumulated ? Gravity fields affect trajectory, but is energy completely intact after fly by ? Photon has its ...
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$\pi$ and the Curvature of Space

If one draws a circle on a sphere and measures the ratio of the diameter to the circumference, that value varies depending on the diameter of the circle compared to the diameter of the sphere it is ...
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Why do some satellites fall to Earth?

In another question How does Newtonian mechanics explain why orbiting objects do not fall to the object they are orbiting?, one can read an affirmative answer. They how do you explain satellites ...
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Making a “heavier-than-air” craft float

How big would a hollow rigid object need to be to float, (not in water but in air) if all of the air was vacuumed out and the container sealed?
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Dig a hole to the other side of the Earth [duplicate]

Possible Duplicate: If it was possible to dig a hole that went from one side of the earth to the other… This question may not be suitable here and it could be closed in seconds but I ...
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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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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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Power to suspend a mass in air

How much power is needed to suspend a mass in the air? The four parts below deal with the same problem. I post them all here, should there be some subtle things I didn't see. The textbook problem A ...
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Modeling a potential well

I attempted to simulate the interaction of a moving particle and a potential well in Mathematica. The particle should experience a force of -$1/r^2$, if the equation for the potential well is -$1/r$. ...
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Is there a delay in the effect of gravitational force?

Let's suppose there is a very massive object and a small object that are 1 lightyear apart. The massive object is large enough that the gravitational force pulling the small object is easily ...
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Gravitational field has no curl? What about gas discs around stars, black holes, etc.?

So everybody says the gravitational field has no curl, and is not comparable to a liquid swirling around a drain. Observationally, of course, there are many examples of vector fields (which I think ...
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Gravitational Effect Versus the Speed of Light [duplicate]

If, for some reason, the sun were to suddenly disappear altogether, I would like to know the following: would we "feel" it first (i.e. being thrown into outer space due to no longer having anything ...
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Vertical and horizontal components of forces and vectors

I'm getting a bit confused when finding components of vectors and forces. In problems for vectors, I've always known that if you want to get the components of a vector, you would use the following: ...
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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 ...
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What does the graviton-matter Feynman scattering diagram look like?

The question is in the title really. I know gravity + QFT is on shaky ground but I'm not looking for Feynman rules, just a schematic, if that is possible. Edit 1: added possible diagram for ...
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The physics behind The Great Flood [closed]

The book of Genesis floats (pardon the pun) some interesting numbers when discussing the Great Flood. For example, it rained for 40 days and 40 nights, and at the end of that time, the entire planet ...
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Why does the force of gravity get weaker as it travels through the dimensions?

Some theories predict that the graviton exists in a dimension that we of course can't see, and that is why the force of gravity is so weak. Because by the time gravity has got from the dimension in ...
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Are neutrinos affected by gravity?

Layman here, but EE and BS physics. I know that light is affected by gravity. But are neutrinos? During the collapse of a star into a neutron star, as the electrons join protons to form neutrons ...
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464 views

Potential energy in a gravitational field

I've seen the following formula for the potential energy of a body in a gravitational field ($\rho$ is the density, $g$ is the gravitational acceleration): $$ \rho g \int_E z dV $$ Can you please ...
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Can the effects of gravity be broken by jumping?

I was having a debate the other day with a work colleague where I explained that gravity is a weak force because it is easily broken. Then I remembered a lecture by someone, I forget who, that ...
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Do all atoms in the universe gravitate each other?

I understand that matter will gravitate toward matter. (ex: Earth gravitates a satellite toward it, and the satellite toward Earth.) Does this always apply, regardless of distance?  Take two atoms, ...
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Can I calculate the height of a cliff from weight of falling object and time taken?

I'm sure a simple question. I have a video of me jumping off a cliff into a river. I want to calculate how high it is. I know my weight, acceleration due to gravity of course, and I can get the ...
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Does the gravity affect voltage in a circuit?

The electric current is a flow of electrons, which have mass (small, but it is still a mass). So, considering a planar circuit, do the properties of the electric current (voltage, intensity) change ...
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Does geodesics from solving full field equations are same as path from energy-momentum tensor?

As we know, if we had an energy-momentum tensor in all space-time we could obtain the metric tensor by solving field equations. Also i think if we had an energy-momentum tensor then we have ...
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Lagrangian point or dark matter?

We know that spiral galaxies spin in a way such that we have to assume that dark matter is responsible for the extra mass required to do so. My question is, can Lagrangian points (L1 and L2) be used ...
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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 perfectly for our all applications, but in my (limited to undergrad General Physics 3 quarters) ...
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Could we use the coriolis effect to travel

Given a platform that is floating independent of Earth's gravity, would it be possible to put a platform over the equator and over the day, would the Earth rotate from under it allowing you to travel ...
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Why don't black holes within a galaxy pull in the stars of the galaxy

visit http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-a-black-hole-k4.html If black holes can pull even light, why cant they pull the stars in the galaxy?
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Did force of gravity cause evolution of large scale structures?

Did big bang create gravity? What role gravity is assumed to have played in the formation (starting from the big bang) of large structures of our universe and what other important physical mechanisms ...
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CERN projects on gravity

Recently I was reading about CERN's upgrade to work on gravitational theories. But if most of the work has been done by General Theory of Relativity than with other theories are there that need to be ...
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Does a magnetic field have gravity?

Re-reading http://physics.stackexchange.com/a/33156/5265; I find myself thinking if light, being EM in the humanly visible spectrum, may possess gravity - does a magnetic field also possess gravity?
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Do all planets rotate around the sun with the same acceleration?

I have this question in mind. suppose if by any chance, all planet around sun stopped rotating. then as per formula F= M * A. all planet should fall with same acceleration towards sun and ultimately ...
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Three-Dimensional Gravity

Does anyone have any references that discuss gravity in three-dimensions? I'm trying to make my way through some papers by Witten relating $SL(2,\mathbb{C})$ Chern-Simons theory and gravity in three ...
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491 views

What is the mathematical nature of space time quantization in string theory/super string theory?

I don't know much about string theory, apart from it being a theory of everything which brings QM, QED and nuclear forces and gravity under one single roof. I am curious to know from a mathematical ...
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What is the effect of temperature on electrostatic-gravitational balance?

We have two identical massive metal spheres at the same temperature at rest in free space. Both have an identical charge and the Coulomb force [plus the black-body radiation pressure if the ...
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A Question on Singularity

I am not aware of GR, but due to curiosity i have a question in my mind. Please let me know if it is inappropriate to ask here. My question is about singularity. I am under the assumption that ...
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Velocity of satellites greater than required velocity

We often find velocity required to keep a satellite in orbit by the formula $v=\sqrt{\frac{GM}{r}}$ where $v$ is perpendicular to the gravitational force. It is very intuitive that the object will go ...
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Could the Earth be ejected when the sun burns out?

My younger brother came home from school today and told us at the dinner table that when the sun burns out the Earth could be ejected from its orbit. Skeptical, I asked his source. He quoted his ...
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Where does the idea gravity=curvature of spacetime really come from?

I have been searching for quite a while but mostly found the answer: Einstein's genius. Quite unsatisfactory. I know and understand that the idea gravity=curvature of spacetime works. Furthermore I ...
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Is the Hilbert-Felber model of repulsive gravity correct?

This theory states that at relative velocities exceeding 3^-0.5 c, gravitational repulsion ensues. The relevant papers are on arXiv by Franklin Felber. Here's one of them ...
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Gravity and objects at 0K

Let's say I put 2 objects at rest relative to each other with 0 Kelvin. Will they move towards each other because of gravity? Where they will get energy to move? I don't have education in this field, ...
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Do photons feel gravity of approaching objects only?

I have read that photons while travelling near massive objects such as the sun experience gravitational pull which is why we see some stars at different positions than they are when seen towards the ...
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Gravitational Stark Effect

Could gravity induce line splittings in the optical spectrum of a molecule similar to the Stark or Zeeman Effects? Naively, a gravitational potential would be a simple addition to the Hamiltonian ...