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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Antineutron repelled by gravity?

I was reading an old post, Can gravity be shielded, like electromagnetism?. One of the responses had this comment. There are some experiments trying to measure whether antiprotons ( antimatter) ...
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Why is earths gravitational pull only at its center?

Does acceleration due to gravity remain constant wherever I go in and on the earth?
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Can gravity be blocked or augmented?

If gravitons (or some other quantum particle) are indeed responsible for the effect of gravity, can gravity be blocked, defected or trapped somehow? Is there any evidence that a gravitational field ...
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Does Energy have a similar effect on time as Mass would when considering the gravitational field both exert?

I was thinking about light and the different frequencies. The higher the frequency the more energetic the photon. The higher frequency photon being more energetic seems counterintuitive when ...
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80 views

Why is gravity so weak? [duplicate]

How does physics explain the enormous disparity between the gravitational scale and the typical mass scale of the elementary particles? In other words, why is gravity so much weaker than the other ...
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4answers
105 views

Exceeding the speed of light using gravity? [duplicate]

From what I have learned, objects must accelerate as they approach a heavy mass. But I also know that they cannot travel faster than the speed of light. What if you had a proton travelling at ...
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Neutron star: free fall acceleration

The textbook from which I teach physics at the end of secondary school, has a question about a neutron star: $M_{star}=1.4\cdot M_{sun}$, radius 15km. "Calculate the free fall acceleration at the ...
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74 views

Ice when melted at zero gravity [on hold]

I wish to know the behavior of ice at zero gravity, how ice will behave when melted at g=0? Thanks
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106 views

Why do termite pellets fall in a perfect circle?

I was just wondering why termite pellets fall down from my bed in a perfect circle. You can see from the images that the follow down on the floor making a perfect geometric figure which is void in ...
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1answer
50 views

Does the Higgs Boson exert gravity?

The Higgs boson is considered to have mass. Would a field of Higgs bosons, W bosons, etc. give off a gravitational field for the duration of their existence?
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Rotating conical singularities in three dimensional gravity

A conical singularity in three dimensional flat space is usually desrcibed by the metric $ds^2=-dt^2+dr^2+r^2\gamma^2d\phi^2$ In three dimensional gravity with a negative cosmological constant, we ...
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Event Horizon of Black Hole

What actually does happen to an object after it crosses the Event Horizon of a BH? Does it- lose the properties of matter and become a new, undiscovered type of matter? does it become negative ...
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38 views

The structure of spacetime and entanglement [on hold]

how many ways to quantize gravity? Do they contradict each other? How to apply long-range entangment/Professor Wen Xiaogang's theory to virtual pairs http://arxiv.org/abs/1210.1281
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Speed of gravity within a mass

We all consider that gravity travels at the speed of light. Light travels at the speed of light except when it is in a medium ,say glass, where it travels slower. What happens when gravity passes ...
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4answers
75 views

How is gravity proportional to space-time curvature in the rubber-sheet analogy?

In General Relativity, Einstein established that gravity is due to the curvature produced by objects in space. We all know that gravity is proportional to mass. The picture Einstein painted looks ...
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1answer
32 views

How to calculate the normal force exerted by a fulcrum off-center?

So I know that $F_N$ exerted by a fulcrum right under the centre of mass for, say, a long horizontal rod, is equal to $mg$. But what if the fulcrum is off the centre of mass either to the right or the ...
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78 views

Is mass essentially an absence in space-time? [closed]

I'm trying to gain an understanding on conceptual physics. I know the following isn't exactly conventional but is any of it fundamentally wrong? Is mass essentially an absence in space-time? As ...
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0answers
31 views

What is the speed of gravity? [duplicate]

Hypothetically, let`s say that one day our Sun is suddenly removed from the galaxy. For us, on earth, would take up to 8.3 minutes to notice that the sun was removed, since the distance from the earth ...
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110 views

Equation derivation for skipping rocks

oWhy can rocks skip over water? For instance, if you conduct an experiment where you drop both rocks from the same height, but give one considerable acceleration in the x direction, one will fall in ...
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1answer
59 views

How can electromagnetic waves be affected by gravity if photons have no mass? [duplicate]

I have found answers that say that gravity interferes with the oscillating electric and magnetic fields of the waves and others that say that since gravity is a bend in space-time, in which case the ...
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0answers
13 views

Poincare patch of $AdS_2$

I know that a metric for global $AdS_{2}$ can be witten as $ds^2=\frac{1}{\cos^{2}\theta}\left(-dt^2+d\theta ^2\right)$, where $\theta \in [-\pi/2; \pi/2]$. So one can draw Penrose diagram for it as ...
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1answer
61 views

Do the arms of a spiral galaxy spin around like a candy bar in long spirals?

Because the arms of a spiral galaxy have a linear center, perhaps they rotate around their center same as a candy bar spiral or a spiral of smoke? Have similar movements within galaxies been measured? ...
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1answer
68 views

Can we disconnect an object from the pull of gravity using some material? [duplicate]

I have once come across a material/ substance/ compound, or something, that cuts off objects from Earth's gravitational pull. In other words, it would keep the object suspended in the air and will ...
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2answers
182 views

How do we age if we tunneled to Earth's core?

Scenario Suppose there exists an advanced technology that can hypothetically transport living humans to study the center of the Earth, as they goes deeper underground most of the Earth's mass would ...
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3answers
51 views

I were to travel to the other side of the world then is this logic possible? If no, why?

I go straight up and stay stationary at a particular point (at a point above action of gravity) in the sky. The earth will rotate and I decide to drop down when my destination has come exactly below ...
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3answers
94 views

Does dark energy work like gravity, but the opposite way?

If a body has more mass gravity will exert a greater force on it. Does that apply also to dark energy? In other words, if a body has more mass, will it be affected more by dark energy? (that is, will ...
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247 views

Is fuelless aviation possible?

I've read the article Gravity powered aircraft flies with no fuel. This is making me confusion, as I can not discern if it is credible. Is it an hoax?
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100 views

What are the photon/electron consequences of matter in a gravitational time dilation?

So I saw Interstellar, and it got me thinking. I won't even mention all the plot holes, but I wanted to ask about a planet orbiting a black hole. I always thought you had to travel near the speed of ...
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66 views

What will be the gravitational pull of the Sun if the Sun contracts to a black hole?

What will be the gravitational pull of the Sun if the Sun contracts to a black hole, and would the Sun be a Schwarzschild black hole or not?
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What is the relationship between $a$ and $m$

$a$ is defined in HERE What is the relationship between the length-scale $a$ and the mass $m$?
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2answers
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Does the gravitational force of one object interfere with that of another?

Assume we have two iron spheres, Sphere A and Sphere B, with identical masses floating in the vacuum of interstellar space separated by some distance from each other. The gravitational force of each ...
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0answers
21 views

circular orbits in general relativity [duplicate]

I am studying the derivation of the circular orbits of particles in general relativity (Derivation) Question 1: What is the meaning of the constants $a$ and $b$, it says they are " length-scales", ...
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1answer
49 views

How do I construct the Maxwell tensor $\bf{^*F}$ from Fadaray one $\bf{F}$ in a non-flat spacetime?

In the book Gravitation (Misner, Throne and Wheeler), it's said that to consider the line element of the flat space on the derivation of Maxwell tensor $\bf{^*F}$ from the Fadaray tensor $\bf{F}$ ...
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2answers
79 views

Can gyroscope work in zero gravity?

Most ships have two or more gyroscopes to balance on water, man made satellites uses gyroscope for orientation as they fall around earth. All these applications seems to be associated with gravity, ...
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1answer
60 views

Gravity vs. Electromagnetism Scenario

Imagine a two dimensional world where there are only two electrons. They are set right beside each other. Of course, immediately they will start to separate, being repelled. My question is, as they ...
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1answer
87 views

How can the Schwarzschild radius of the universe be 13.7 billion light years?

So i was reading about Schwarzschild radius on Wiki and I found a interesting thing written there link. It says that the S. radius of the universe is as big as the size of the universe? How is this ...
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61 views

Spacetime in Loop quantum gravity

In LQG, does spacetime consist of interconnected loops? Are those loops real? If spacetime does not consist of the aforementioned loops, what it consists of?
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1answer
51 views

How does a wormhole form? [duplicate]

I heard about wormholes. I know that they are paths that can be got by contracting spacetime. But, how does a wormhole form?
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28 views

Gravitational Wave Interference [duplicate]

Can gravitational waves interfere like water waves and light waves? If not, can someone explain what about these waves make them uninterferable?
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Why should we want to quantize Gravity? [duplicate]

I understand that it will be "nice" to have a quantum description of Gravity as well, just like the other 3 forces. I would like to find out what problems arise in existing theory (not counting String ...
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5answers
253 views

when an object is lifted (at a constant velocity) shouldn't the work done on the object be zero? [duplicate]

When I lift an object from the ground (at a constant velocity) I'm applying force on the object equal to its weight and the earth is also pulling it downwards with equal amounts of force. So if the ...
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4answers
113 views

If velocity is constant, how can $p = F\cdot v$ be non zero?

If an airplane of mass $m$ is flying at a constant speed $v$, the power of the airplane is $$P = m\cdot v\cdot g $$ where $g$ is the acceleration of gravity and therefore: $$ F = m\cdot g, $$ but, ...
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24 views

Does a lightning strike have a physical weight?

A lot seems to be unknown about lightning and it is possibly a source of dark energy at the instance of the strike. So if we were to place say a 10kg lightning rod (earthed) on a set of insulated ...
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1answer
37 views

Visibility of a super-massive star

I heard that mass and distance are the only deciding criteria for determining the gravitational pull. Keeping the distance constant, if mass would be the only deciding factor for gravitational pull, ...
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1answer
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System of point masses orbiting a center of mass

I'm working on a programming homework working with a system of point masses/particles. We are given the particles' initial positions (s_x, s_y, s_z), initial velocities (v_x, v_y, v_z) and masses. ...
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1answer
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Is there a way to calculate if a domed cylinder will balance on its dome or is top-heavy?

I noticed that some domed cylinders have a centre of gravity low enough to balance on their dome, and others just topple over. I'm sure you can predict this mathematically: My question is: Is ...
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1answer
92 views

We Don't NEED Quantum Gravity because Gravity isn't Even A Force! [duplicate]

Now, I understand the motivation for quantum gravity. I honestly want to work on a theory myself. However, gravity, according to General Relativity, is not a fundamental force of nature. To me, it's ...
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90 views

Hidden Weyl symmetry & fixed metric lead to simplified correlators

We consider AdS$_{d+1}$ in Poincaré coordinates: $$ ds^2=\frac{1}{z^2}\left(-dt^2+dz^2+dx_{d-1}^2\right), $$ where we set the AdS radius to unity. We study a scalar in this background with action $$ ...
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75 views

Why is gravity viewed as a curvature of spacetime and not the electromagnetic force? [duplicate]

There are four known forces in the universe. Two of these forces are the force of gravity and the force of electromagnetism. The first is the result of the mass of the object that has the gravity. The ...
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Could Quantum Entanglement be related with gravitational interactions? [closed]

Particles are entangled when they share the same state and their properties become correlated. Interaction with one of them, by say measurement, is experienced instantly by the other. If we measure ...