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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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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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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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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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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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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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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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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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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Simplifying effect of a hidden Weyl symmetry in a QFT on curved spacetime

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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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 ...
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How do these factors affect the free fall of objects?

Take an example of two balls of different masses being dropped from about 250 meters from the ground. How do the following factors affect free fall: Air resistance. Absence of air resistance. ...
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Principle behind Atom Interferometry?

In Laser Interferometry, you propagate a laser beam, split it into two different paths, reflect once, combine it back and deduce the phase difference accumulated from the path difference, from the ...
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Diffusion vs Gravity in water: does a dissolved ion tend to “sink”?

Im a french student in geochemistry. My question might be silly, but I became really too confused to answer it myself. Does gravity affect the diffusion of ions in water ? Lets imagine a vertical ...
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Space: a vacuous void or an entity?

I am a chemist and, until recently, a senior Research Manager with a major chemical company. Please excuse the potentially naive ramblings of an idiot in what follows, but I do not have the ...
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Is there experimental evidence supporting the equivalence principle between different particles?

Knowing virtually nothing of GR, and only hints of particle theory, this might be something of a naive question. If I've misunderstood somethings, I would gladly like to know why. Perhaps a more ...
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Ricci tensor of Metric black holes with nils and solv geometries of Horizon

The metric of black holes with nils and solv geometries of the horizon is generically represented by $$\mathrm{d}s^2=-r^{2z}\mathrm{d}t^2+\frac{\mathrm{d}r^2}{r^2}+\sum_{I=1}^3 r^{2q_I}(w^I)^2$$ How ...
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Why can't light escape a blackhole? [duplicate]

Gravity attracts objects which have mass right. We know that light is massless so why does a black hole's gravity attract light?
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Travelling through a worm hole

In every documentary I've seen about worm holes, I have noticed that they usually say that according to the General Theory of Relativity, there could exist worm holes called traversable wormholes; ...
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1answer
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The g-force of common objects hitting the floor

At my friend's work they have an accelerometer which measures the force with which certain objects hit the ground. He claims that from four feet high, cell phones hit a solid metal surface with a ...
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4answers
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In $1$-dimensional space, how would the gravity generated by an electron affect a photon moving away from the electron if the photon can’t slow down?

Suppose we had a universe obeying the same physical laws as our own. But it had only one spatial dimension (represented by the $x$ axis) and it was totally empty. There are just two point-like ...
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How to derive this equation? [closed]

How to derive this equation? It comes from a book named Seismic Wave Propagation in Stratified Media.
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Before Einstein came up with General Relativity, were there serious reasons to doubt Newton's theory?

Before Einstein came up with General Relativity, was there any serious reason to doubt Newton's theory (and its various developments)? I only know about the discrepancy in Mercury's orbit, which may ...
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How to apply the Relation between net acceleration and time in this case?

I have a small doubt ... I read online about some elevator problems and concluded that , If a body is falling downwards, the net acceleration of the body is = acc.due to gravity - acc. of the body ...
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How can matter reach the singularity of a black hole if time stops at the event horizon? [duplicate]

Black holes are said to be composed of two parts: A singularity at the center, where all the mass of the black hole is condensed in a point of zero volume. A black and empty ball delimited by the ...
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Acceleration due to Gravity: Free Fall [duplicate]

If we are in a free fall which implies we are accelerating at 9.8 m/sec every sec. And let's say that we are falling into a pit that has enormous depth. So isn't this be possible that we may ...
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Could gravity be repulsive at short distances?

I was wondering if it would be consistent with empirical data if gravity became extremely repulsive at short distances. For example (please bear with my use of classical formulas, I know little of ...
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Would the presence of B-modes in the CMB provide evidence for quantum gravity?

Finding B-modes in the CMB (which aren't due to foreground contamination) would be evidence for gravitational waves, because they cannot be produced by density perturbations (to first order, is my ...
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Is possible to generate energy from gravity?

When the wind goes through the vanes of an wind turbine, it's generate energy. When the water goes through the water turbines, it's generate energy. So my question is short and simple, is possible ...
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Why doesn't the light get out?

You're standing on a gedanken planet holding a laser pointer straight up. The light doesn't curve round, or slow down as it ascends, or fall down. It goes straight up. Now I wave my magic gedanken ...
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Gravitoelectromagnetism higher-order effects

See http://en.wikipedia.org/wiki/Gravitoelectromagnetism#Higher-order_effects According to the Higher-order effects... "Gravitomagnetic arguments also predict that a flexible or fluid toroidal mass ...
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Will boomerang work in vacuum chamber on Earth?

Earth's gravity, the way we spin and air pressure are essential to have fun with the boomerang. Suppose we do same thing except in a vacuum chamber totally devoid of air will it still be able to ...
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Is there any way gravity can reflect light?

I know gravity leads to certain interesting optical phenomenon. I know light curves around a massive body, I know light red shifts if we look far enough in space. Is there any configuration that could ...
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how to make an equal-arm balance beam?

Use an equal-arm balance beam, with a 250 kg counterweight suspended 5 cm in the air on one end, and the mass to be moved just touching the ground on the other end. Energy storage is in gravitational ...
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Similar effect to gravity horizontally? [closed]

I've been pondering this today. Say you have a moving vehicle, with enough space to move around in (say, an empty moving truck). How fast would it have to be going for you to jump and go flying across ...
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If I launch a coin, will it always fall down?

I was running in the university aisle (I was late for the statistics lesson) when I heard: "In normal condition there is a possiblity that if you launch a coin instead of falling down it'll go up". Is ...
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Is negative energy a consequence of gravitational energy? [closed]

Assumption Treat all objects as a point. Gravitational constant = 6.67384 × 10^-11 m^3 kg^-1 s^-2 Acceleration of the object is 1 ms^-2 The setup Imagine there are 2 identical objects with mass of ...
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How is the conservation of momentum satisfied in long-range attraction such as electromagnetism and gravity?

I'm not a physicist, but my understanding is that electromagnetism (including attraction between opposite charges) is mediated by the photon, and gravity is probably (hypothetized to be?) mediated by ...
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Study the center and interior of a black hole using quantum entanglement

Having just watched the latest in a long line of space movies; Interstellar tries to combat the problem of studying the center of a black hole and understanding what's going on inside. My question is, ...
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Acceleration to lightspeed using gravity

Suppose we have a very advanced spaceship that (aside from colliding with planets or entering a blackhole) is indestructable, and can go very fast, but is incapable of moving at lightspeed on it's ...
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What causes light to travel through a curved fountain of water?

Today I observed a tilted fountain spurting water upward (the water fell smoothly; no detectable turbulence). A colored light was shown upward into the water as it left its source. This light traveled ...
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What observation(s)--if any--confirm that the types & concentrations of energy, which are influenced by gravity, are the same ones that cause gravity?

General relativity allows various forms of energy to participate in the gravitational force. What observation(s)--if any--confirm general relativity's notion that the various types & ...
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Real-world evidence that non-massive entities (or even: antiparticles), and their behaviors, are sources of gravity?

The theory of general relativity tells us that non-massive entities, and their behaviors, are possible sources of gravity. Mass isn't needed, the theory says. What's the real-world evidence that ...
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2 different density liquids in space

Lets say you are in deep space with basically zero gravity. You have a ball of water floating in front of you. If you carefully injected that ball with a syringe filled with vegetable oil, what ...
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What are Galileons good for?

Lately I've seen many papers (for example "The galileon as a local modification of gravity"; 292 total hits on the arXiv) on types of field theories known as Galileons, and I'm wondering what the ...
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Gravity in $d$ spacetime dimensions

Given the following action $$S=\frac{1}{16\pi G}\int d^4x \sqrt {-g}(R+aR^2+bR_{\mu\nu}R^{\mu\nu}+cR_{\mu\nu\lambda\sigma}R^{\mu\nu\lambda\sigma}),$$ which is in 4D. How to we generalise this ...
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Thought experiment on graviton breaking the speed of light [closed]

The effect of gravity travels at the speed of light. Suppose we can entangle a pair of gravitons (which are only theoretical, but who knows for sure?) and separate them over a vast distance. Hold on - ...
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Will a hot object have more gravity than a cold object?

Imagine two objects, identical and having the same mass. Now my question is, if you heat one object and do not do anything with the other object, will the hot object possess more gravity (because it ...
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1answer
115 views

Can energy bend space? [duplicate]

I know mass bends the space around it and I also remember matter can be converted into energy and vice versa, so my question is: can energy interact with space in a similar fashion as matter does?