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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Motion on a rolling Body

How can an object can continue to run on a rolling circle along the X direction and maintain a balance with specific acceleration.
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How can the orbit of a planet having a 3600 year period and a perigee between Uranus and Neptune be computed

There is a significant difference between the distance that gravity would move a planet with no velocity and the distance that gravity curves space time for a moving object. The 'fictitious' ...
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21 views

What is the time dilation effect in the presence of two equal and opposite gravity sources? [duplicate]

If one were between two equal and opposite gravity sources, would the time dilation effect cancel out, since the acceleration is cancelled out?
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26 views

what health per-captions should be taken for theoretical senerios [on hold]

so i been working on some detail research and i been having some difficulty applying perceptions since half of the experiment affects are only currently applying as theoretical phenomenons. but let me ...
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0answers
24 views

What is the difference between cosmological horizon and event horizon?

Do the terms cosmological horizon and event horizon mean the same thing?
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1answer
39 views

Shouldn't dark matter distort light and there for be directly detectable?

It is an established fact that gravity bends space time and therefore distorts light. We know that Dark matter acts gravitationally. So, just for giggles, lets say I had a sphere of dark matter ...
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27 views

Variational principle conformal time in cosmology

I am studying mimetic gravity in which physical metric is written as $$g_{\mu \nu}= \tilde g^{\alpha \beta}\partial_{\alpha}\phi\partial{\beta}\phi \tilde g_{\mu \nu}$$ The action of ...
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2answers
41 views

Principle of equivalence

Einstein's principle of equivalence states that one can not distinguish between a freely falling nonrotating system in a gravitational field and a uniformly moving system in the absence of a ...
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0answers
62 views

A few questions about gravity [on hold]

Please don't count this as a duplicate, I have searched so many similar questions and have not found the answer. Also, don't count this as too broad because I can't find the answers anywhere else so ...
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1answer
42 views

Earth density distribution from shooting neutrinos?

I am interested in possibility of inferring Earth interior structure from gravitational data. As classical calculus problem shows, it is impossible to understand non-uniform density distribution ...
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1answer
139 views

Certain doubts regarding the movie 'Interstellar' [on hold]

In the movie, or rather a scientific fiction, Interstellar, we saw in the last part, that the actor falls into the black hole, travels in time, which is a dimension inside the black hole, and then, ...
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1answer
44 views

Difference between mass and weight [duplicate]

I already know that when I standing on weighing machine it's measuring my mass not my weight, but when I take the same machine to moon it's will read different value. According to my information that ...
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1answer
20 views

Would a fast moving (approaching $c$) stream of particles be affected by the gravitational pull of a gas giant?

I was inspired by this SE question. Would the gravitational field of a gas giant (such as Yavin IV) have an effect on the super laser (i.e. slow it down, change the direction), or is the mass so ...
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2answers
62 views

Where to use acceleration due to gravity $g\propto\frac{1}{r^2}$

I (and we all) know that acceleration due to gravity $g\propto\frac{1}{r^2}$.Now my question is can I use this for depth.If not,why?If we can use it for depth or not struck me when I was trying to ...
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1answer
2k views

Why don't lakes have tides?

There's a tidal effect that we can clearly observe in oceans, which is the effect of gravity from the Sun and the Moon. If gravity affects everything equally, why don't lakes have tides?
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0answers
29 views

How to calculate backreaction in AdS space?

This might be a very straight forward and basic question in GR. I am interested in calculating backreaction due to certain matter field (say, scalar) in AdS space. Should I put the energy-momentum ...
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3answers
80 views

Could black holes interact with dark matter at distances far greater than matter?

I watched this Nova episode on super massive black holes and learned that the speed at which the outer stars in a galaxy orbit correspond to the size of the black hole at the galaxy's center. They ...
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2answers
67 views

Before we realized that supermassive black holes were at the center of large galaxies, how did the models explain galaxies?

So, I was watching this show on Netflix about supermassive black holes. I didn't realize that astronomers were surprised to find these black holes at the center of galaxies, because I cannot imagine ...
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0answers
39 views

Why the Yang-Mills ansatz is able to describe every interaction we know? [on hold]

All interactions which seem to rule the microscopic world we have access to are described by the standard model, which is a Yang-Mills theory for the SU(2) x SU(3) x U(1) group. Also, gravity can be ...
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1answer
45 views

Gravity and centre of mass

Does gravity act entirely as if on the centre of mass? Often I have heard this, but it seems more realistic (even if less practical) if it acts on individual bits of matter, therefore weaker further ...
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25 views

Expanding Electric Field, Magnetic Field in post-Newtonian Gravitational Potential

I've cross-posted this question from Mathematics since Physics is probably better suited for the nature of the question. I've ...
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0answers
17 views

Controlling the flow of powder from a container, based on grams selected [closed]

was wondering how you would control the flow of powder from a container (with a small cylindrical dispenser at the bottom). The container is filled with powder. As the container drains, less ...
-1
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0answers
63 views

Why are gravitational forces always attractive? [duplicate]

In my curiosity, gravitational forces, unlike electric forces, is always attractive, because of the empirical evidence. However, why is it so? In what model or theory can this phenomena be explained ...
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0answers
28 views

water pressure for various pipe diameter if water tank pressure is known [closed]

can anyone help me out please.. I have a water tank which is 20ft from the outlet and the capacity is 1000lt. pressure from this water tank is 8.66psi. Now how to calculate the water pressure for ...
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1answer
35 views

Gravitational intensity [closed]

I calculated the gravitational intensity and potential at a point P due to a horizontal linear mass distribution of length '$L$', mass '$M$' and uniform linear density at a distance '$R$' apart from ...
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2answers
2k views

Are there tides in the atmosphere?

Analogous to the tides of Earths oceans, do the Moon and Sun cause our atmosphere to bulge in what could be described as a low and high tide?
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1answer
44 views

Meaning of “physical” and “gravitational” metrics

I've recently been reading some notes (following a paper by J.D. Bekenstein, titled "The Relation between Physical and Gravitational Geometry": http://arxiv.org/abs/gr-qc/9211017) on alternative ...
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3answers
267 views

gravity delayed by speed of information transfer

A few months ago I had the pleasure of listening to an episode of RadioLab (a very informative podcast I would recommend to everyone) when they had Neil deGrasse Tyson on. He was discussing the very ...
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2answers
53 views

The pressure in a container of water is based on depth. So what happens if I remove the bottom of the container?

So I understand that if we have a system that involves a container of water the pressure will equal atmospheric pressure at the top and as we go further down the container the pressure will increase ...
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0answers
15 views

Books on Spin-2 Gravity / Fierz-Pauli theory

I am trying to find a good pedagogical book/set of notes on Gravity as a spin-2 particle. I have been reading through Gravity & Strings by Ortin but it's very brief and offers little ...
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2answers
111 views

Why does gravity affect time?

So Special Relativity states that for all non-accelerating objects of matter the laws of physics are the same. I'm confused on why this law of physic applies to objects in acceleration and gravity ...
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2answers
74 views

Why is sometimes more difficult to lift a baby?

I have a small cousin and she enjoys when I pick her up, which I can do pretty easily. Sometimes though she decides she wants to make my life difficult, and when she decides so, she tells me she is ...
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0answers
22 views

Singular isothermal density distribution

Does anyone know where the Singular isothermal density distribution $$ \rho(r)=\frac{\sigma_{V}^{2}}{2\pi\,G\,r^{2}} $$ or how it was derived. Are there any good references on how this equation was ...
2
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2answers
173 views

Has the speed of gravity been measured experimentally? How? [duplicate]

In Newtonian physics, changes in gravity propagate instantly. In general and special relativity, gravity propagates at the speed of light, $c$. From reading answers to questions about gravity on this ...
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1answer
137 views

What causes gravity in M-Theory?

New and updated, because people were misunderstanding what I meant! General relativity describes gravity as the result of....(very roughly) spacetime curvature Newtonian gravity describes gravity as ...
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1answer
57 views

How relativity affects projectile motion?

If For example; I'm in a train traveling on earth at .99c, and I drop a ball from a 1m height inside that train how long would it take to hit the ground from the ball's frame of reference? I can see ...
3
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1answer
35 views

What does gravitational mass mean if (weak) equivalence principle invalid? [closed]

As equivalence principle states Mass and weight are locally in identical ratio for all bodies. --Newton This implies that the gravitational mass does only depends on its inertial mass. Suppose ...
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2answers
83 views

Infinite Accelatation

Before I ask my question, let me just say, I know very little about particle physics and general relativity, so I may ask a obvious question or a question that makes little or no sense. Now, what ...
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1answer
376 views

2D space-time curvature

Actually, why is the space-time curvature considered 2D plane. As 2-D dimensional space-time curve is used to explain why moon revolves around the earth stating because the massive objects wraps the ...
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0answers
33 views

Generalized gravitational entropy and entanglement entropy

What are the differences (if any) between Generalized gravitational entropy (Lewkowycz-Maldacena) and holographic entanglement entropy (Ryu-Takayanagi)? More specifically, I was wondering following ...
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0answers
44 views

If a spaceship accelerates enough can it overcome spaghettification?

If a spaceship accelerates at the right amount would that counteract the spaghettification caused by falling into a black hole?
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1answer
70 views

Do black holes have a puff pastry point?

If a person falls into a certain sized black hole they accelerate very fast, which increases the g forces on them. These g forces flatten the person out into a pancake. As the person falls further ...
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6answers
14k views

Am I attracting Pluto?

My question is simple: as the title says, am I exerting a force over for example Pluto, although it is a very small force, it is there, right? Or maybe let's go further: Am I exerting a gravity force ...
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2answers
67 views

Stand on a black hole

Is there an theoretical possibility that an black hole rotates so fast that the acceleration pushing you out of the black hole is nearly equal to the gravity?
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1answer
86 views

Does acceleration of time explain gravity (rather than the other way round)? [closed]

I have a question about interpreting (explaining, even) the general theory of relativity. A common interpretation of GR, as I understand it, is to imagine two-dimensional space represented by ...
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2answers
35 views

Save a falling person by nullifying their mass or reversing gravity [closed]

Let's say you have the superpowers to manipulate matter, mass and gravity. Imagine a person falls off a plane, flying few kilometers above the air, and they are about to get splattered onto the hard ...
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3answers
74 views

Can Gravitational force between two bodies always produce motion?

Imagine there are two bodies of mass 1 Kg each separated by some distance.Then by Newton's formula of calculating gravitational force we can see that the gravitational force between them is very ...
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1answer
90 views

What would be gravity in one spatial dimension? [duplicate]

First of all, I should say that I understand if this is put on hold for being unclear... but I'll try my best to make it as clear as it can get. For all the time I spent learning Newtonian Gravity ...
3
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3answers
288 views

Why Can a Skydiver Hit the Ground and Be Killed? [duplicate]

This is a follow on question from Physics SE Question "Can a Skydiver Land On a Large Slide and Survive?". User Steeven gives this answer here. User Dargscisyhp asks: What is it exactly that ...
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6answers
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Can a Skydiver Land On a Large Slide and Survive?

Please forgive my lack of artistic ability, but here's my question: Consider that a skydiver, without using his parachute, were to fall exactly parallel to a giant curved slide that starts at ...