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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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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30 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 ...
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87 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 ...
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40 views

Gravitational Lensing Example

Can the actual size of a black hole be hidden behind by the photon sphere like this tomato wrapped underwater? Like an eye in a eyelid.
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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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63 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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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 ...
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41 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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Could the recent evidence of a gravitational force orbiting the solar system indicate not the existence of a ninth planet, but rather a black hole?

In case you haven't heard already, researches at the California Institute of Technology discovered mathematical evidence of large object orbiting the sun at a distance about 20 times further than that ...
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How is the temperature of a star related to gravity?

As far as I know the Sun gets its energy from the fusion reaction, where Hydrogen is converted into Helium. I was watching an episode of Cosmos: A spacetime odyssey. There Neil deGrasse Tyson said, ...
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129 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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75 views

Velocity change with height

The formula $v^2 = u^2+2GS$(where $v $ is final velocity, $u $ is initial velocity, $G $ is acceleration due to gravity and $S $ is the linear displacement) assumes that gravity remains constant ...
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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 ...
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173 views

How should we understand the value of a recent theory published on Phys. Rev. D? [closed]

I would like to know what to make of this paper, published on Phys. Rev. D on the 11$^{th}$ of January: Quantum field theory of gravity with spin and scaling gauge invariance and spacetime ...
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61 views

Why does mass attract? [duplicate]

Question stands as title says: Do we know (straight probable is reasoning is meant by "knowing") why mass is doing so?
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54 views

Help with Gravity question

I need some help with this question from my homework. An Oort cloud comet moves on an orbit so eccentric that it can be well approximated by a radial straight line through the Sun. The comet starts ...
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96 views

As The World Turns 2

When dinosaurs roamed the Earth was the Earth rotating faster creating less gravity to allow for their size? How much would 100 kg weigh then?
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rocket vertical landing [closed]

SpaceX has published a couple of videos that show one of their heavy-lift rockets landing vertically in a highly specific location. How is it possible that they are able to control so many ...
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146 views

Is gravity Lorentz-invariant?

If I go whizzing past the Sun in my spaceship at 0.8c, I will see that the Sun looks like it has been squished. That is, it will be Lorentz-contracted along the direction of my motion (by a factor of ...
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How Do Low Kinetic Energy and High Kinetic Energy Atoms Attraction differ?

Will atoms of 2 difrent energy levels electron and/or Kinetic attract more than 2 Atoms at he same energy level? Do 2 high energy level atoms attract more than 2 low energy atoms?
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132 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 ...
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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 ...
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27 views

If gravitons are particles, how do they escape BH gravity if nothing can? [duplicate]

If gravitons are particles, how do they escape BH gravity if nothing can? So are the gravitons really particles or is there really just/only curvature of space-time?
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45 views

How are orbits made stable

I understand the concept of object staying in some orbit due to centrifugal force and gravity. However I do not understand how is orbit of a body like satellite or planet has perfect balance between ...
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How are gravitational waves exactly produced?

I was thinking about gravitational waves, and I found out that I may have a doubt about their production. Assuming the whole calculations find a wave-like solution to be understood, I was wondering ...
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1answer
39 views

Who can explain me better 'the condition with no weight'? [closed]

This is related to gravity and vaccuum, which says that when the body is in vaccuum, its weight is lost. I need any examples.
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Why doesn't gravity mess up the double slit experiment?

So let's say you are doing a double slit experiment. Also, let's use electrons. My question is, won't the gravity of the electron affect the earth, thereby causing it decoherence and its wave ...
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Why is spacetime curved by mass but not charge [duplicate]

According to general relativity theory, the deformation of spacetime is proportional to energy tensor $$T_{\mu\nu}.$$ $$ R_{\mu\nu}-\frac{1}{2}g_{\mu\nu}R = 8\pi G T_{\mu\nu}. $$ Does it mean that ...
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71 views

What will hapeen if we remove air from a pipe [closed]

At first i did not know if this relate to engineering or physics but i think it mostly relate for physics so i posted here. My question is what would happen if we have a pipe set vertically and have ...
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2answers
103 views

Gravitation, light and black holes

I have few basic misunderstandings about black holes. I know that heavy mass causes a curved space time around it, what i don't understand is if this mass is a star and it becomes a black hole, why ...
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Space time expansion near galaxies

I understand that on galactic scales, the expansion of space time has no appreciable effect, gravity being dominant and thus distance between stars remains fixed despite universal expansion. Can ...
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67 views

Gravitational Lensing Diffrence between Big and Small Black Holes

Would you see more of the back holes iris in smaller black holes compared to larger ones and if so can one be big enough the photon sphere would completely cover it and it would look like distorted ...
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26 views

Why does individual N2 molecule rise when heated?

I get that hot air is less dense so it rises due to floatation and all, but what happens to one individual diatomic Nitrogen that it increases it's distance from ground? And why is it that the air is ...
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23 views

Calculating satellites orbits [duplicate]

Do Newton's and Einstein's theory of Gravity differ very much when calculating satellites orbits. If they don't, in what areas do they actually differ?
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109 views

Gravitation - Is going beyond a model possible? [closed]

I can not really understand why two bodies attract each other, what happens between? One points out the gravitational field to explain this phenomenon and one say that it is because of the general ...
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59 views

Are parts of objects part of that object's mass?

Disclosure: I'm not a physicist or a scientist, so there is a chance that this will seem like a silly question for some of you. But I'm really curious about this and I want to know the answer. ...
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How exactly are the relative strengths of gravity and electromagnetism quantified? [duplicate]

I've often heard it said that gravity is much weaker than electromagnetism, and after looking at several questions on SE, I feel that I've got at least a qualitative handle on the concept -- gravity ...
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1answer
44 views

Can the helium from a gas bottle lift the bottle?

Does a gas bottle full of helium contain so much helium that, if the helium can expand into a baloon, can lift the empty gas bottle? And input on this question highly appreciated...
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54 views

Acceleration in a space capsule which is falling to the earth [closed]

At first I apologize for asking such a career killing question in such an elite platform. Today I tried to prove something to four graduated engineers which I will mention below. The argument ...
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Time Dilation Equals Red Shift looking in or blue shift looking out

We can see the center of our galaxy. With more density near the center of our galaxy is red shifting observed from our perspective? From the center of the galaxy looking at us would a blue shift be ...
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1answer
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What is the property which flows as described by the stress energy tensor in GR?

I found the following definitions: The stress–energy tensor (sometimes stress–energy–momentum tensor or energy–momentum tensor) is a tensor quantity in physics that describes the density and flux of ...
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How is it possible that Thermosphere can maintain so much heat? [closed]

Thermosphere is the Layer of Atmosphere in approx 100-1000 km altitude. Particles in thermosphere are typically at 1400 K temperature. But the sun activity can raise the temperature up to 2300 K. ...
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Gravitons, photons and conservation of momentum

How can gravitons be emitted from a mass to cause an attractive force to another mass? The same question could be asked of attractive e-m forces as well. Don't these violate the conservation of ...
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If gravity dropped off with the cube of distance

If gravity, for instance, dropped off with the cube instead of the square of distance from the Sun, would the planets still follow elliptical paths?
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How does a mass create the gravitational field of GR? [closed]

As far as I understand, and please correct me if I am wrong, but the basic idea of general relativity is that spacetime is curved by matter. What we call gravity is then not a force as per Newton but ...
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54 views

Where does gravity get's its energy from? [duplicate]

So I have read this post and I have another question about it. The first answer says that if we lift an object up that is the energy we "give" to gravity and then gravity uses that energy to pull the ...
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When sitting on a chair is it the chair actually pushing against me?

I was listening to The Infinite Monkey Cage on the BBC and they were talking about general relativity and gravity. They were saying that gravity is not a force as Newtonian laws describe and is at ...
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What is gravitational energy in general relativity?

In GR the curvature of spacetime "is gravity". This curvature is expressed via the Riemann tensor (or the Ricci tensor + Ricci scalar). The curvature is connected via the Einstein Field Equations with ...
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1answer
86 views

Why do the satellites revolves on a circular path around a planet at orbital velocity? [duplicate]

We know that there is a particular velocity with which a satellite will move in a circular orbit ( orbital velocity ) but if its velocity is more than the orbital velocity but less than the escape ...
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31 views

Gasses and Gravity

I have two questions. First question. When gas is placed inside a container it fills the container evenly with constant pressure. If the container size varies the gas expands or is compressed but the ...