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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Available material on Giant Gravitons

I am looking for a pedagogical introduction to giant gravitons (if one exists!). I have basic string theory/SUSY knowledge but no introduction to AdS/CFT. (Do I need to do some reading on AdS/CFT ...
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Could the gravitional pull of all the travelling photons “relativistic mass” in our galaxy explain “dark matter”? [duplicate]

Does that make sense mathematically? If we could sum up all the photons in-transit in our galaxy and calculate the total gravitational pull, could it provide an alternate explanation instead of ...
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36 views

Turning point of ball, when throwing it into the atmosphere

I am currently reading an introduction chapter about gravitation. One exercise was about calculating the escape velocity on earth. At one in the book it reached the following formular: $ r_{max} = ...
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Force and Advanced Physics: E.g. is gravity really a force? [duplicate]

I'm kinda beginner in physics but recently I've been studying really interesting concepts like the four fundamental forces and General Relativity. I started thinking that there is a weird ...
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77 views

Propagator for massless spin 2 particle

In my quantum field theory class, we saw ad derived the propagator for both spin-0 and spin-1 particles, massless and massive. I am curious to know what the propagator looks like for a spin-2 ...
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47 views

Minimum Distance for “Speed of Light Approach”

I tried to calculate the minimum distance between a planet and a test mass for the mass to attain the speed of light on colliding with the planet's surface if it were released from rest at the initial ...
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99 views

Is Energy attracted to Energy?

Newton taught us that bodies with mass attract each other according to the universal law of gravitation (mass-mass attraction) and Einstein taught us that mass and energy are equivalent though his ...
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4answers
169 views

How do I correctly introduce time into this equation?

So, for the past few years it's been my goal to create an equation that would give me the position of an object in a gravitational field at time $t$, given it's initial position and velocity. At first ...
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35 views

Relative time difference and the gravitational potential of the geoid

I'm having trouble with something from a problem set on relativity and time. We are given the equation for time elapsed on a clock on the Earth's surface relative to time at the geocenter ...
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1answer
63 views

What are the effects of increased mass on persons traveling at near light speed?

It's been a long time since I studied physics (and then only very superficially), so please bear with my gross naivete. This question's been running around in my head for about two weeks now, and I ...
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4answers
377 views

Effect of gravity upon light and bagels

According to this question and this web site, photons undergo twice the deflection from gravitational fields as do physical objects. However, the weak equivalence principle states that locally, ...
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30 views

The stability of falling through a planet [duplicate]

Let's say that you were standing on Earth, and stepped into a hole that went perfectly straight down through the entire planet to the other side. Would the terminal velocity of your fall, and the ...
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5answers
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Shine a beam of light horizontally, drop a stone from same height - would both hit the ground at the same time?

If a beam of light was shone horizontally, and simultaneously a stone was dropped from the same height, would they both hit the ground a the same time? Of course on Earth they would not, but let's ...
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34 views

why do everything tend to be stable? [duplicate]

Whenever I ask'why does a proton attract electron?' People say that 'because they are oppositely charged' But I want to know why do opposite Charges attract each other and tend to become neutralised? ...
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1answer
35 views

Definition of “nonlinear” in the context of perturbation of gravity

What exactly is the definition of a nonlinear perturbation when applied to a background spacetime metric? I have seen so called "linear perturbations" which look like $$ds^2 = -(1+2\Phi)dt^2 ...
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31 views

Does gravity get stronger with compression of matter? [duplicate]

I am wondering if gravity gets or would get stronger with ultra-compression (relativistic level) of matter? This may sound stupid but this is how my thought process went. Let us assume we have an ...
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1answer
140 views

Does all matter emit gravitational waves all the time?

I understand that gravitational force is a result of the curvature of spacetime and that the analogy with electromagnetic waves falls apart at a certain point. However, I have been confused when ...
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195 views

Is the method of images applicable to gravity?

It is well known that the method of images is a useful tool for solving electrostatics problems. I was wondering why this technique is not applied when considering newtonian gravity? Obviously there ...
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3answers
527 views

Is it correct to say that falling object are standing still?

As I was browsing youtube I came across the BBC video "Brian Cox visits the world's biggest vacuum chamber - Human Universe: Episode 4 Preview - BBC Two" He drops a bowling ball and a feather in a ...
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1answer
65 views

Is there any evidence that subatomic particles are affected by gravity?

If so what experiment has been done to show this?
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107 views

How does one calculate the full perihelion shift of Mercury, including perturbations from other planets?

I'm talking about the full calculation, including perturbations from other planets. I've seen the general relativistic correction done a half dozen times before, but I can't say that I've seen the ...
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3answers
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Finding the center of gravity of an object that does not have equal distribution of mass

NOTICE: I have very limited knowledge of physics so try not to confuse me, though I know it is inevitable. Say I have a grid of squares, where a □ has 1g of mass, while a ■ has 5g of mass. If I ...
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1answer
125 views

Thought Experiment: An object falling indefinitely under gravity?

So the other day, I devised this thought experiment: Consider an infinite tunnel, and you drop a coin of mass $m$ into it. Considering the effect of gravity to be applicable and neglecting air ...
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67 views

Space-Time and Entropic gravity [closed]

Gravity warps space-time, and Gravity can be thought of as Entropy. (Entropic gravity) So, as spacetime expands, how is space-time Entropy (or the inverse of gravity) effected? (If this is a noob ...
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1answer
62 views

Paradox of nesting black holes and release of energy

By dumping a gas cloud into a small black hole, I can produce radiation energy, this is how quasars produce energy. By dumping the previous black hole, with the gas cloud inside, into a black hole, ...
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101 views

What are the equations of motion that model near light speed orbits of a massive body about incredibly massive bodies?

In Kip Thorne's recently published book, The Science of Interstellar, he describes, by means of an illustration, the complex nature of a spacecraft orbiting a massive black hole with velocities ~ ...
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1answer
64 views

Am i trying to fly by pulling myself up by my hair? [closed]

I'm currently trying to build a multi-rotor of my own, and am testing it when i noticed that the lift that i am supposed to be getting is wayy less than what i am expecting. I have a rectangular body ...
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47 views

Is this cosmological scenario possible?

Is it possible that the universe is infinitely large and contains an infinite amount of mass that is distributed in such a way that gravitational force is never infinite? If so, is it possible that ...
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3answers
118 views

How strong must gravity be to stretch time?

I'm not sure if this is true or not but I heard that gravity has the ability to stretch time, and I was wandering if this is true. If so, how intense/powerful does the gravitational force have to be ...
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2answers
75 views

Does the escape velocity of a black hole exceed $c$ *before* a singularity is created?

As an offshoot of the question Can we have a black hole without a singularity? I'm curious if the point of no return at which the massive object is condemned to become a singularity happens before its ...
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4answers
447 views

Surface waves on Dr. Miller's planet

In the movie 'Interstellar', the crew land on a water world orbiting a black hole. The gravity is greater than that of Earth and there are huge surface waves present in the ocean that they land in. ...
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40 views

Is there a theory that physically explains the origin equivalence principle / explains gravity via acceleration?

I've been thinking about how gravity could arise from a 4th dimensional spinning cylinder with space-time that has pliability like rubber (which I think is a generally accepted analogy). The ...
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1answer
271 views

What is the largest disparity of gravitational time dilation from earth's that life can survive?

In certain theoretical scenario's a human can be in a gravitational field where he would age half as fast as on earth's surface. However, for light to travel half as fast in one direction, we are ...
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108 views

Can we make a “Gravity Mill” based on principle(s) of Newton's cradle?

DISCLAIMER: Newbie/Wannabe Physicist. What's to stop us from making a "Gravity Mill" which is a bar/rod attached with weights on both ends and pivoted at the ...
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Why does my apple not weigh 500 tons?

Related to this question: What is potential energy truly? $E=mc^2$ - energy equals mass. So, if an object has gravitational potential energy relative to another object, it should have additional mass ...
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2answers
106 views

Curvature gravity and a falling apple? [duplicate]

I know very little of physics after Einstein. I am aware of that Einstein's gravity theory says that the existence of matters creates curvature of a space-time, so that our Earth orbits our Sun. I ...
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36 views

To What Extent are Magnetism and Gravity Related and Unrelated? [duplicate]

I find many people (especially UFO-ologists) are quick to say there is an interplay between magnetism and gravity, especially when explaining antigravity of UFOs. On the other side, I see those who ...
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1answer
61 views

Generalized spin connection and dreibein in higher spin gravity

I am studying 3D higher spin gravity and I would like to know the mathematical and physical meaning of generalized spin connection and generalized dreibein that appear in this theory. It is well known ...
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1answer
75 views

Possibility of a Dark Star

I think it was a very early notion, pre-black holes, that there may exist a star that was so massive, all of its outgoing light would return to its source. Is this actually possible? Is there an ...
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2answers
80 views

Relationship Between Acoustics and Gravity?

I have studied some physics in college, but not enough to know the answer. My motivation: sound (or acoustics in general) does not exist in a vacuum, which means that acoustic waves are only present ...
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55 views

How would an observer feel the Einstein Thirring Lense Effect?

The Einstein Thirring Lense Effect, also known as Frame Dragging, is what happens when cellestial bodies have rotation. It states that when a body of mass is rotating around an axis it drags space and ...
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1answer
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Two different expressions for the Schwarzschild Radius? [closed]

This might sound as quite an obvious question at first, but in most places the expression I've seen for this radius is: $$\frac{2GM}{c^2}$$ but in other places, I've seen the expression as:$$\approx ...
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1answer
108 views

Modeling the motion of a bouncing ball

I'm writing a program that displays a line of text, and animates a ball that bounces from syllable to syllable (like a sing-along). The program knows the location of each syllable, and it knows at ...
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1answer
51 views

Light speed travel precautions [closed]

How strong would need to be gravitational shield on the ship if would encountered meteorite dust in diameter 50mm² at that speed?
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3answers
138 views

Gravity and bottomless pits [duplicate]

Assuming that someone is theoretically able to make a hole through the center of a large planet, and then jumps down the hole, what will happen? Given my understanding of gravity and energy, my ...
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2answers
80 views

Why does General Relativity predict more light deflection than Netwonian Physics?

If one looks at the limit as light's mass approaches zero, Newtonian Physics predicts a deflection of light (this can be seen by the fact that all objects are accelerate the same due to gravity.) ...
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1answer
58 views

Can gravitational force act as an impulsive force in any case? [closed]

Can gravitational force be termed as impulsive in any case? I' m thinking about it but couldn't get any answer. When two heavenly objects collide then the force exerted on each of them during the time ...
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1answer
121 views

Why will this plan for a perpetual motion device not work? [duplicate]

I have made a plan for a perpetual motion device, but I am sure that it won't work because otherwise the world would be relying on it right now. I know that perpetual motion defies the laws of ...
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2answers
95 views

Are time and gravity affected when at rest compared to free fall?

A falling object moves along a geodesic path ('straight path') in spacetime. When it comes to rest it now follows a 'curved path' through spacetime. Is the passage of time and force of gravity ...
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1answer
124 views

Curved paths through spacetime when standing still?

I have heard that falling objects fall at the same rate irrespective of their mass. They are 'following straight line paths through curved spacetime'. Does this mean that objects that accelerate in ...