Questions tagged [gravity]

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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Effective Geometry of Non-Extremal Near Horizon RN Black Holes

We know that we can obtain AdS$_2\times S^2$ by considering the near horizon limit of extremal RN black holes in $4d$ with various asymptotics, i.e., either Minkowski$_4$, or (A)dS$_4$. How about the ...
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Can gravitational time dilation be thought of as there being “less time” near a massive object?

In the descriptions of gravitational time dilation I have read, clocks are said to run more slowly near a massive object when compared to clocks farther away. I have never heard this described as ...
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What is rate of change of Earth's gravity (jerk, 3rd derivative of position)? [closed]

We know that gravity changes with height so there must exist a jerk. Could I know the method to find it. Does there exists jounce(4th derivative of position) for Earth's gravity?
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Do two stars on exact opposite sides of a black hole pull on each other gravitationally?

If so, how do their gravitational fields go through the black hole? Can information be sent this way (via gravitational waves)?
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Can gravity and hydro power be utilized in a closed system to generate efficient electricity? [closed]

This is my second post on this topic. The first one had some flaws but I resolved them with this new design. This is more of a thought experiment - which I don't think is that outlandish given ...
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A system with effective negative gravitational mass but positive inertial mass [closed]

This post is related to an earlier question "https://physics.stackexchange.com/questions/589812/is-it-possible-that-antimatter-has-positive-inertial-mass-but-negative-gravitati?noredirect=1#...
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Another doubt on Newman-Janis Algorithm

I) THE ROTATING METRIC: Following the question (and the answer) of mine: Doubt on Newman-Janis algorithm for a traversable Wormhole (I just changed the typos of the functions) we realized that given ...
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Is it possible that antimatter has positive inertial mass but negative gravitational mass? [duplicate]

Newtonian mechanics seems to allow for both positive and negative gravitational mass as long as the inertial mass is always positive. The situation is analogous to electrostatics but with the ...
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How do black hole properties change with added mass?

How do the spin, lifespan, radiation, gravity, and relativistic effects (time dilation in relation to proximity) change as you start from minimal mass to more massive black holes (not limited to the ...
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Why is “Gravity as a result of space-time curvature” not accepted as a fact? [duplicate]

Now that gravitational waves are confirmed. Not to mention the other numerous experimental verifications. Why do we still need an elusive graviton? Isn't there not enough evidence that the space-time ...
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Right after the Big Bang, how did particles overcome extreme gravity and other forces and manage to fly apart?

I have read this question: Why did the universe not collapse to a black hole shortly after the big bang? where Lubos Motl says: This matter has no center - it is almost uniform throughout space - and ...
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If gravitational field is not real, then am I gaining energy?

I don’t know much about General Theory Of Relativity but I have heard that it does not consider gravitational fields like Newtonian Mechanics. If an object were to be free falling, then according to ...
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Demonstration of the Brans-Dicke's Lagrangian

The Lagrangian in general relativity is written in the following form: $$ \begin {aligned} \mathcal {L} & = \frac {1} {2} g ^ {\mu \nu} \nabla \mu \phi \nabla \nu \phi-V (\phi) \\ & = R + \...
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Does the energy density of space create cause gravitational attraction beyond what would be computed from an object's mass alone?

I am starting from the assumption that the gravitational warping of spacetime increases its volume, so a spherical region of space with a fixed surface area would be able to fit a larger number of ...
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Nilpotency of BRST operator in gravity

I am going through the BRST quantisation in Perturbative quantum gravity and looked at the papers of Nishijima and Ojima. I am confused about the closure of the BRST operator; I.e $s^2=0$, ...
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For vertical circular motion, why does the minimum speed for a full cycle depend on what the ball is attached to?

Suppose we have the following situation and I'm asked for the minimal speed to be given to the ball so it can continue a full cycle. If the ball is connected to the middle point with some hard ...
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How does a black hole capture an approaching star and force it to start an elliptical orbit?

Let's assume that a standing still black hole attractor can have a star orbiting it in an orbit if the star was somehow a result of the same past proccesses as the black hole.So the star must be on a ...
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What is the consensus of the physics establishment regarding cosmic expansion being the cause of gravity? [closed]

After an epiphany I was certain I'd proved gravity is the cause of cosmic expansion, then find that others have considered the same starting with Friedman about 1920. Jen Jamison's article was very ...
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Conceptual problem with general relativity

According to Einstein, mass curves spacetime and objects in the nearby field tends to travel in the shortest possible path to reach their heavier counterparts. My question is was not Newton's ...
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How can Earth accelerate toward US and China with no expanding? [duplicate]

In this video it's explained that there is no gravity force, it's all acceleration: Earth moving toward us, but how that's possible without expanding (toward people standing on the opposite sites of ...
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What form or state of matter is a black hole

Neutron stars form dense clusters of neutrons which I have heard being called an element 0 and theoretically could form strange matter and the like from what I have read. Given that a black hole is ...
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Is 'Action at a distance' really a troublesome concept?

I often watch videos where they say that even Newton was bothered by the idea of action at a distance, and that General Relativity solved that problem. But why is 'Action at distance' a problem in the ...
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Height oscillations in orbit induced from lunar gravity

I am trying to numerically solve the orbit of a space probe around the moon in a non-spherical gravitational field . $ \Large \begin{align} \frac{d^{2} x}{dt^2} = - \frac{G M x}{(x^2 + y^2)^{3/2}} - \...
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Mass lossage of a human over iterative falling due to heat

I watching a video that mentioned that a meteor loses mass as it falls via energy being converted to heat, so say we are on the Burj Khalif ($828$ meters), how many times would a human, say $6$ ft ...
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How far the galaxy's 'flat part of rotation curve' extends?

I know that the galaxy rotation curve doesn't obey general relativity and instead of decreasing, the star velocity remains constant which is shown by a flat rotation curve (rotation velocity v/s ...
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Do two specks of antimatter experience antigravity between each other? [duplicate]

Do two specks of antimatter experience antigravity between them? If no is the answer then what 2 specks may ever be the cause of that?
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Question about inclined planes and constant velocity [closed]

I apologize that this is such a simple question, but I am a beginning physics student trying to learn more in his spare time. I can't find a satisfactory answer anywhere since most inclined plane ...
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Can projectile motion under gravitational fields be considered an example of collision?

It is given in my book that the scientific definition of collision is that two or more bodies are said to collide when their motion is affected by the force they exert upon each other. For Eg. When ...
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Why does the speed of an object affect its path if gravity is warped spacetime?

I think I understand the idea of thinking about gravity not as a force pulling an object towards another object but instead a warping of space so that an object moving in a straight line ends up ...
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If we can live with classical EM field in atomic physics, why can't we live life with a classical theory of gravity? [duplicate]

In basic atomic physics of light-matter interaction, very often we assume the atom is quantum mechanical with quantized atomic levels but assume the electromagnetic field to be a classical wave. It is ...
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Black Holes in Higher Derivative Gravity

It is well known that Einstein Theory of General Relativity has pathological solutions, called black holes, where the theory fails at some point and gives us infinite values. In order to solve this ...
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If gravity were a “real” force, then how would I be able to tell if I'm falling or accelerating in space or on Earth?

Background: I think it would be helpful for laypersons like myself to understand how, in practice, a "real" force differs from a pseudo-force. Virtually all explanations (eg, on this stack, ...
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Event horizon vs high gravitational field: How is it light can escape a gravity greater than the speed of light

Calculated event horizon using Schwarzchild radius for 10 Earth mass primordial black hole and get a diameter of 17.7336cm. Using spherical gravity calculation of g=GM/r^2, I get gravity at 1 meter ...
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Potential energy for accelerating frames

Given a large mass and a smaller mass at infinity, the total amount of work done on the object due to the force of gravity is -Gpe, for a given radius (r) end point. All fine there. But a thought ...
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Can gravitational effects extend to the other fundermental forces?

It is known that gravity is not a force, but a bending of 4D spacetime. Could charge (as well as mass) have an analog in this regard? Why does mass bend spacetime but charge does not? Sorry for the ...
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Did we just misunderstand gravity?

Einstein told us that a spring balance under free fall shows zero deflection and thus derived that gravity is a curvature in the fabric of spacetime and all those stuffs. Now let's assume we have a ...
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Conditions for Schwarzschild Metric to be applicable

The Wikipedia article regarding the two-body problem in General Relativity states that the Schwarzschild metric "corresponds to the external gravitational field of a stationary, uncharged, non-...
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Are there different types of gravitational forces based on different types of masses ( inertial or relative etc)

There are different types of masses like inertial mass, passive gravitational mass, active gravitational mass, relative mass, et cetera. does Are there different types of gravitational forces that is ...
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Action of Higgs gravity coupling

I was going through Higgs-gravity related literature. I have a question about the sqrt(-g) term in the action. Is there any condition on the g-metric tensor components to come up with sqrt(-g)>=0 ??...
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How to calculate the gravitational force of a black hole outside event horizon at a given distance $r$? [duplicate]

Let $g_{bh}$ $[kg·\frac{m}{s^2}]$ be the force caused by the gravity of a black hole. How do we calculate the force $g_{bh}(r)$ outside event horizon $R_{Sch} = \frac{2GM}{c^2}$ onto a satellite with ...
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Speed of gravity's time energy value [duplicate]

If light cant escape from a gravity well, how can gravity escape? we see that gravity of one object attracts another, obviously attracts itself. Is there a point that there is so much gravity that it ...
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What would a graph of distance between two gravitational objects vs time look like?

Lets say there are two objects in space that are attracted to each other, and are a distance r from each other. The gravitation force between the two objects is $$G\frac{Mm}{r^2}$$ As they accelerate, ...
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If a black hole bends light what does to a beam that arrives at a zero degree angle directly towards the singularity? [duplicate]

We can only speculate what is going on but does the black hole singularity make the light arrive faster than it would in space not affected by gravity?
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How to calculate the strength (“space force”) of dark matter within galaxies?

Let's first have a look at the observed speed within galaxies (source): On the left side we can see the speed of celestial bodies within galaxies derived by gravity only (gravity is usually created ...
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Deriving Kepler's third law

In Arnolds book in the section of dimensional analysis he tells to show that in a homogeneous central force field (i.e $U(ar) = a^v U(r)$ for some fixed $v$ and any $a$), if $r$ is an orbit, then for ...
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To find the angle of slipping of a falling coin

In an attempt to predict the outcome of a toss, I dropped a coin with its edge just touching another sharp edge as shown in figure. (The edge is flat and sharp with very less friction as in case of a ...
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Does turning a circuit on increases its gravitational pull?

I've been taught that things that have mass "create" a gravitational pull, and that an electron has mass, even though it's really small. So I was thinking, does the electron's gravitational ...
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Are there other theories than gravitational attraction taken into account as a reason for the extreme accumulation of matter in the universe?

This question is about how small the interstellar density is (less than 1 atom per cubic centimeter). But although the interstellar density is very low, matter tends to extremely aggregate in certain ...
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Why is the Weyl tensor square gravity non-unitary?

I want to understand constraints of unitarity in quantum field theory. There is quite folklore statement: gravity with a Weyl tensor square term is non-unitary How to understand this? (I think that ...

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