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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Conservation of angular momentum in Earth-Moon system

We all know about the fact that tidal friction is slowly slowing down the Earth's rotation about its axis, and that subsequently the Moon is slowly drifting away, in order for the angular momentum of ...
2
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0answers
36 views

Work by Gravity using Tensors [on hold]

Now I'm familiar with the various methods for deriving work done by gravity, but I noticed a few things about the situation, and wanted to see if I could properly apply a tensor treatment to the ...
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0answers
27 views

Freely falling body applied some external force [on hold]

A body of mass $10kg$ is thrown upwards with initial velocity = $10m/s$. Then it moves up and falls back down at the same point, after which an external force of $10N$ is applied in the upward ...
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8answers
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How do stars from far away affect Earth?

I know that we obviously get light (or we wouldn't be able to see them), but are there any other ways that they affect Earth and maybe just our solar system in general?
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2answers
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How gravitation affects tides

I know that tide is caused by the gravitational pull of moon but what I don't know is how it affects water. I have actually these doubts. Why does gravity of the moon creates tides only in water? ...
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1answer
50 views

Would the Moon be able to take water from Earth?

I know that if you add mass to the moon, it would get closer to the Earth. We all know that the moon causes the tides because it's gravity pulls the water. So, my question is: If the moon gained more ...
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1answer
57 views

Virtual particles, gravity, and dark matter? [on hold]

In Hawking's radiation, virtual particles respond to intense gravitational tidal forces with pairs being ripped apart. One crosses the event horizon and the other escapes. On the other hand, in ...
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0answers
34 views

Could a satelite be pulled away by gravity while the object it was orbiting keeps unaffected in its own orbit?

I'm asking this, since I try to educate my self a bit in the field of astrophysics. From my point of knowledge the by title given scenario could occur. But I haven't yet read anything that sounded ...
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3answers
221 views
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99 views

If gravity is due to curvature, how does gravity work in situations with no curvature?

The strength of the gravitational field falls off as the inverse square of the distance from a spherical source. It only falls off as the inverse of the distance from an extended cylindrical or line ...
5
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2answers
93 views

How much additional light does Earth receive from the Sun due to Earth's gravitational field?

I was reading about how gravity affects light, and that got me wondering how much additional light is collected by the Sun due to the Earth's gravitational field. Is it a significant amount of light ...
7
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1answer
230 views

Explanation of the waves on the water planet in the movie Interstellar?

We will ignore some of the more obvious issues with the movie and assume all other things are consistent to have fun with some of these questions. Simple [hopefully] Pre-questions: 1) If the water ...
0
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1answer
36 views

Gravity, Acceleration, Time Dilation and the Equivalence Principle

Three clocks are started at exactly the same time on Earth. The first and second clocks are taken into the vacuum of space. The first clock accelerates until it reaches 100,000m/s, then stays at this ...
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665 views

Dark energy vs. gravity

If dark energy is everywhere around us, then why don't we get separated? For example why don't I get separated from the pen kept in front of me? Or take a similar example in free space. Is dark ...
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4answers
438 views

What truly is mass, and is there a direct way to measure it?

We know a mass of an object of one kilogram as an object that weighs W = mg = 9.8 N and we reference it to that, (when it should as a fundamental parameter describe weight not the opposite). But if we ...
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0answers
23 views

At what temperature can water escape from the earth?

After a period of million years the water level of the earth increased. But I'm wondering whether the amound of water is always has been the same since that time. Imagine the atmosphere is about ...
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1answer
22 views

Eddy current induce emf

Q1Suppose there is a wire having AC current so as ac current is alternating it creates back emf wether that back emf produces current ?? If yes then that current is same as eddy current or not?? ...
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0answers
47 views

Gravitational and electrical field [closed]

Electric field is due to charges and nagnetic field is due to magnet poles right my question is why the charges exits in electron and proton and why magnetic poles exist . And why masses attract each ...
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2answers
812 views

How can gravity truly be infinite?

From my knowledge, gravity is infinite and extends throughout all of space. It diminishes as distance increases but is still present everywhere. So given enough time, no matter where something is in ...
2
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2answers
648 views

Three-Dimensional Gravity

Does anyone have any references that discuss gravity in three-dimensions? I'm trying to make my way through some papers by Witten relating $SL(2,\mathbb{C})$ Chern-Simons theory and gravity in three ...
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2answers
39 views

Gases Expanding Vacuum

Why do gasses expand in space rather than attract forming a liquid? Do some gasses attract when they are colder?
2
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4answers
307 views

A ball in the gravity potential field of a black hole — seems a paradox

As illustrated in the following diagram (A, B, C, D are 4 specified space points, and C is close to a black hole), a small ball at distance of a black hole is stationary (suppose now it's mass is m0) ...
3
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1answer
85 views

Could there exist (and if not: why?) non-elementary particles composed of gravitons?

I read about glueballs, which should be particles made purely out of gluons. This is a quite theoretical thing but its existence has at least been theorized. Now, I don't know so much about ...
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2answers
123 views

Falling with same acceleration and meaning of gravity

My question is what does falling with same acceleration has to do with what Einstein concluded concerning the gravity in terms of the curvature?
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1answer
43 views

Precision of the Gravitational Constant [closed]

I went to a theological talk where the speaker, while answering a question on intelligent design, claimed that, if $G$ was different by one part in $10^{120}$,then the universe would either collapse ...
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1answer
100 views

Atoms, Gravity and Electrostatic Charge [closed]

How close do 2 atoms of any type the have can be together before gravity with an electrostatic charge that repulses?
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32 views

Can 1km diameter ball of water preserve it's integrity before hitting the ground falling from 10km altitude?

I still argue with my friend over some big ball of water (1km in diameter) that is being instantly created 10km over the surface of the earth in perfect sphere form. I stated, that as it hit the Earth ...
2
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1answer
34 views

Is the polarization of light changed by gravity?

The Gravitational_redshift shows, that the wavelength of light gets altered in a gravitational field. But what about polarization of light? I imagine that e.g. by tidal forces circular polarized light ...
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1answer
80 views

How much force would it take for you stop the Moon from crashing into the earth once it has started to fall?

In my previous question, I asked how much force it would take to destabilize the Moon's orbit enough for the moon to start falling into the Earth and collide. Assume this has already happened. Now, ...
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0answers
31 views

Centripetal force at the pole is different from the equator

why is the centripetal acceleration in the poles and equator if different? I know that it's related to Equatorial budge. But what I don't get it is that the centripetal force is zero at the poles. ...
3
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1answer
165 views

The cosmological constant as a Lagrange multiplier?

The cosmological constant $\Lambda$ can be introduced into the gravitational action like this : \begin{equation} S = \frac{1}{2 \kappa} \int_{\Omega} (R - 2 \Lambda) \sqrt{-g} \; d^4 x + \text{matter ...
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0answers
50 views

What happens when one uses a blender in zero gravity?

I was recently told by a friend that using a blender type apparatus in a zero gravity environment will act like a centrifuge instead mixing properly. Is this the case? Furthermore, can anyone provide ...
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0answers
46 views

Unification: was gravity a part of it or not? [closed]

This question is regarding the unification of the fundamental forces in the early history of the universe. It seems that the unification of electromagnetism and the weak nuclear force (the ...
2
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2answers
324 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 ...
5
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1answer
118 views

Do metric theories with torsion contradict solar system observations?

Obviously, the answer to this question can be "maybe, if you make the torsion tensor small enough", but my question is, given some "typical" size to the torsion tensor, do the spin-orbit couplings ...
5
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1answer
133 views

How to measure Torsion and Non-metricity?

In General Relativity, we most often work with the Levi-Civita connection (metric and torsion-free). What kind of experiment can we make to be sure that our physical space-time indeed is torsion-free ...
11
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1answer
687 views

Spacetime Torsion, the Spin tensor, and intrinsic spin in Einstein-Cartan theory

In Einstein-Cartan gravity, the action is the usual Einstein-Hilbert action but now the Torsion tensor is allowed to vary as well (in usual GR, it is just set to zero). Variation with respect to the ...
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1answer
37 views

Will the energy of gravitational collision be the same?

If you put two small stationary spherical objects (say 1 meter wide weighting 1kg) 1 light year across and let them collide after some time. Will the energy of collision be the same as if you put ...
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2answers
145 views

Super massive Black Hole and photon reduction [closed]

This is a picture of 2 galaxies taken from The Hubble. The arrow shows a smaller galaxy's black hole starving of the usual stars because of the binary rotation about the bigger galaxy that is pulling ...
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1answer
28 views

Does matter stacks up as it approaches Black hole?

When something approaches Black hole it'll experience time dilation with respect to a frame away from the black hole. So to an observer away from the hole the object would seem to slow down until ...
3
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1answer
77 views

Why is the gravitational constant.. constant? [duplicate]

Many scientists have now come to the conclusion that a big bang might not explain the 'start' of the universe and are coming up with alternatives. Could it be that gravity is dependent on the ...
10
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3answers
437 views

Are there models/simulations of antigravitational antimatter-galaxies?

In the comments to another question's answer, I started wondering: Assuming antimatter possessed negative gravitational mass§ (which is not proven impossible to date, though deemed unlikely), ...
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1answer
129 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 ...
4
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1answer
40 views

Electron-Positron Annihilation in a Gravitational Field

When an electron and positron annihilate what happens to any gravitational energy they have? In a way the energy is 'shared' between these two particles and all the matter in space. It must take a ...
0
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0answers
62 views

Would a grid of $10^{57}$ hydrogen atoms collapse?

Assume we have a gridded cube of $10^{57}$ hydrogen atoms, with all atoms 1mm apart from other atoms. This 'cube cloud' is in an area of space that would otherwise be at zero g, were it not for the ...
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1answer
136 views

Confusion about gravity

I understand the “rubber sheet” model of Relativistic gravity is just an illustration, and beyond the initial issues of mixing three dimensional objects with a two dimensional representation of 3D ...
2
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1answer
55 views

Gravity is Instant [duplicate]

Without being able to manipulate gravity. How do we know that gravity is restricted to the speed of light? or gravitational effects from an exploding star would be felt (if we were near) before we ...
0
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1answer
35 views

What fluid dynamics equations are like in zero gravity?

I don't know if this is a proper question. I am not so familiar with fluids. I am just curious about what Navier-Stokes equations for fluids will look like in zero gravity. Are they stay the same? If ...
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2answers
185 views

Gravitational waves and time

Two questions. It is said that time can only go slower in gravity fields and if you move faster. I have heard that when a gravitational wave pass earth then the space/time vibrate and time change ...
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1answer
77 views

What effects would a finding of Gravitational Repulsion Between Matter and Anti-Matter in the ALPHA Experiment have on Mainstream Theory? [closed]

The actual nature of the gravitational force between matter and anti-matter (attractive or repulsive) remains unsettled: See Are there experiments taking place right now that might show evidence for ...