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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Why are there Gravitons among the modes of oscillation in String Theory?

Why are gravitons present among the modes of oscillation of the 'strings' in String Theory?
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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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What is the exact definition of center of gravity?

I've come across many definitions. Is it 1) The point from which the weight of the body acts, i.e., the point at which if the entire mass of the body is assumed to be concentrated, the gravitational ...
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2k views

How gravitation affects tides

I know that tide is caused by the gravitational pull of moon but what I don't know is how it affects water. I have actually these doubts. Why does gravity of the moon creates tides only in water? ...
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139 views

Is it sure that gravitons are massless bosons? [duplicate]

Possible Duplicate: “Speed” of Gravity and Speed of Light I'm wondering if gravitational waves have the same speed of light? They must if gravity is mediated by a graviton spin ...
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231 views

Clarification on Wald's book

I have a question concerning the Wald's book: General Relativity. In the appendix E, he derived the Einstein equation by considering the surface term (GHY). I do not understand what he said after the ...
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What results from particle collision would ensure the existence of the graviton?

I understand that particles are smashed together to try to enable us to detect some sort of graviton presence but we can't actually detect a graviton due to the fact that it 'exists' in some extra ...
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0answers
679 views

Why does a coin falls faster when it's flipping as well?

From my experiments with measuring how fast a coin falls, I have consistently measured a faster falling rate for a coin that flips as it falls. As an example, a coin dropping on its edge from height ...
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201 views

Simulating a black hole binary system

As part of a project for my degree I am writing code to simulate N-body gravitational interactions, however I have to then use this code to investigate something. Struggling to think of ideas I ...
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What makes the stars that are farther from the nucleus of the galaxy go faster than those in the middle?

It has no sense that stars that have a bigger radius and apparently less angular speed($\omega$) goes faster than the ones near the center.
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What does velocity dispersion (sigma) reveal about a galaxy?

I'm getting hung up on this term. In studying SMBHs, I see that velocity dispersion strongly correlates with mass. Just what is the velocity dispersion? How can the velocity dispersion of the galaxy ...
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Does a photon exert a gravitational pull?

I know a photon has zero rest mass, but it does have plenty of energy. Since energy and mass are equivalent does this mean that a photon (or more practically, a light beam) exerts a gravitational pull ...
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All matter has a mass but does all matter have a gravitational pull?

I know that all planets and stars have a gravitational pull but does a simple much smaller object have a gravitational pull for example a pebble?
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Gravitating sigma models

I am looking for a review or book on sigma models in (super)gravity theories, which arise from dimensional reduction.
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How will the super massive black hole affect our galaxy?

I've recently learned that the general consensus is that several (if not, most) galaxies have super massive black holes in their center, in particular the Milky Way. This, at least to me, makes ...
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1answer
62 views

Who has succeeded in demonstrating the Lense-Thirring effect?

Who has succeeded in demonstrating the Lense-Thirring effect? This effect is one that describes the rotational motion of the Earth from a space-time structure. This effect is the "drag" of the ...
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5k views

Jumping in an elevator?

I've always been under the impression that jumping in an elevator wouldn't help at all, especially after reading a snippet of physics where Einstein said that free fall was identical to zero gravity. ...
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945 views

About binary stars and calculating velocity, period and radius of their orbit

I saw somewhere about being able to measure the velocity, period and radius of a binary star orbit by looking at red shift and blue shift. I understand it but can someone give me an example of ...
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Lowest gravity on Earth's surface?

I am trying to determine which on Earth's surface has the lowest gravity. Googling is not finding anything concrete. My natural inclination would be to think of Mount Chimborazo in Ecuador, being on ...
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Why is Jupiter so sharply defined?

In photographs of Jupiter, the limb seems extremely definite. Being a gas giant, my naive self thinks that the atmosphere should have a more gradual cut off, creating a hazy effect similar to that on ...
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337 views

What really is the future about the Standard Model

The fact that the bosons of the weak force have mass is something that I think technically poses many problems. To avoid this and other problems with the masses of the particles devised a mechanism ...
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How can you calculate the exact position of the Earth taking into account the gravitational attraction of Mars and the Sun?

I think there must be a formula to calculate the exact position of the Earth taking into account the gravitational attraction of Mars and the Sun. Is it possible with vectors?
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Increasing mass' effect on the balance between centripetal force and centrifugal force

Okay, this is nothing more than a thought experiment which popped into my head while driving home from work today. Take the case of a single body orbiting another, larger body, as in a planet and a ...
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The square in the Newton's law of universal gravitation is really a square?

When I was in the university (in the late 90s, circa 1995) I was told there had been research investigating the $2$ (the square of distance) in the Newton's law of universal gravitation. ...
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Still trying to understand gravitational potential and Poisson's equation?

A week or so back I asked a question about the gravitational potential field $$\phi=\frac{-Gm}{r}, \qquad r\neq 0, $$ and how to show the Laplacian of $\phi$ equals zero for $r\neq 0$? Eventually, ...
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Does the Moon's orbital inclination follow the wobble in the Earth's rotation?

As the Earth wobbles during rotation, does the higher gravity at the equator tend to pull the moon toward an equatorial orbit even as the earth does that thousands of years wobble cycle? It would ...
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What is the proof that the universal constants ($G$, $\hbar$, $\ldots$) are really constant in time and space?

Cavendish measured the gravitation constant $G$, but actually he measured that constant on the Earth. What’s the proof that the value of the gravitation constant if measured on Neptune would remain ...
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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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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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Raising a toolbox with a rope

Suppose you use a rope to hoist a box of tools vertically at constant speed v. The rope exerts a constant upward force of magnitude F_up on the box, and gravity exerts a constant downward force (the ...
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2answers
361 views

Potential energy conservation in traversable wormholes

Let's say I have a tube, of large radius (about 5 - 7 meters in diameter), with traversable wormholes at the ends. The wormholes are arranged as such that if something falls inside one hole from ...
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3answers
323 views

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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533 views

Why no basis vector in Newtonian gravitational vector field?

In my textbook, the gravitational field is given by$$\mathbf{g}\left(\mathbf{r}\right)=-G\frac{M}{\left|\mathbf{r}\right|^{2}}e_{r}$$ which is a vector field. On the same page, it is also given as a ...
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How can anything ever fall into a black hole as seen from an outside observer?

The event horizon of a black hole is where gravity is such that not even light can escape. This is also the point I understand that according to Einstein time dilation will be infinite for a ...
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Trying to understand Laplace's equation

I'm struggling here so please excuse if I'm writing nonsense. I understand that the gravitational potential field, a scalar field, is given by $$\phi=\frac{-Gm}{r}$$ where $\phi$ is the ...
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Wavelength of photon changes as it rises from a planet's surface(acc. to this equation)?

The setup assumes a large mass(Earth?) an a photon launched from its surface initially. The wavelength of the photon on launch is known. Then the new energy of the photon is compared with energy it ...
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Calculating the force of a mass bearing down on an object

I need to calculate the force of a weight bearing down on a smaller object, constraining it from expansion. The weight bearing down has a much bigger surface area than the smaller object. I know the ...
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2answers
259 views

Is there zero energy cost to generate a gravity field?

It seems that all objects with defineable mass emit a gravity field, which interacts with other objects within said field. My understanding on this may be very limited, but how is the field ...
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618 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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Are objects in a gravitational well shortened?

Bob is in a gravitational potential well, he moves a long vertical stick up and down a distance of 1 meters. Alice observes the upper end of the stick, at upper location. There is the phenomenon of ...
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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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Surface tension of N non-mixing fluids

I am a mathematician, not a physicist, so please be gentle with me if I write something wrong. Consider a bounded, regular container $\Omega$, which is filled with the fluids $F_1,...,F_N$ which do ...
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What would be the optimal weight of a ball if I want to throw it as far as possibile?

Assume the force behind my throw to be X. Assume the point of release is 2 meters above ground. Asume the ball is made of shiny steel. I'm not sure if the material matters, I'm just thinking that ...
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271 views

What is the mass of individual components in a gravitationally bound system?

When material of rest mass M falls from infinity onto a black hole accretion disk, it gets heated and then emits so much light that the energy radiated away can measure up to about 30% or so of M c^2. ...
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155 views

Trinary System Arrangment?

I'm writing a science fiction story and wondered if someone could help me with the setup of a trinary star system I have in mind. Basically I just wanted to know if: a) a system with a central, ...
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How Does Dark Matter Form Lumps?

As far as we know, the particles of dark matter can interact with each other only by gravitation. No electromagnetics, no weak force, no strong force. So, let's suppose a local slight concentration ...
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Simulating Gravity in 3D Game?

Alright, I am writing a space simulator for a 3D game and I would like to implement gravity of objects into it. Is there a nice way to find a velocity vector which can be added to my engine output ...
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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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Is the curvature of space around mass independent of gravity?

Is the curvature of space caused by the local density of the energy in that area?Could gravity be a separate phenomenon only arising from the curvature of space? For instance if the density of energy ...
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Can gravity be shielded, like electromagnetism?

If I remember well, they said that it can't, but I do not know why. Yes, I meant if gravity can be shielded using something like a Faraday cage (or something else?). Thank you.