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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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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98 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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79 views

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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163 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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112 views

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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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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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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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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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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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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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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71 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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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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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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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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54 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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57 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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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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151 views

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. It'...
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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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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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242 views

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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118 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 ...
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61 views

Effects of gravity on light on the surface of the Earth [closed]

I read over the question and answers on the effects of gravity on light. I would like to ask a more specific question about gravity and light. What is the effect of gravity on light on the surface ...
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202 views

Why does electromagnetism have torsion, whereas gravity does not?

Why don't we use torsion-free covariant derivatives for QM, even though we already do so in the case of GR? In general relativity, we use the Levi-civita connection, a torsion-free connection ...
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Gravity spacetime visualization [duplicate]

When gravity spacetime is visualized, it's a sag with the lowest point in the middle of the planet/star as you can see here: For all planets and stars, there is zero G in the core due to that the ...
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Detection limits on 'd' if gravity force was proportional to $1 / (R+d)^2$

Assume the force of gravity is proportional to $1/(R+d)^2$ where $d$ is sufficiently small, then, how small would $d$ have to be to evade detection by modern experiments? My thinking is that if $d$ ...
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With gravitational lensing could we see our selves from a right angle?

When looking at a black hole the ability to see ourselves is compromised by the small window for the light trajectory to come back to us. The light from the Earth that is bent by (almost) 180° and ...
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does my gravity theory sound logical? [closed]

hypothesis: space has the four forces built into it like a density that allows for the atoms and the EMR to move within confined limits i.e. the speed of light, fusion, etc.. Each change in dimension ...
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Simple metric of stellar collapse

Is there a simple metric (Lorentzian manifold) known which exhibits the formation of a black hole while not having any white hole counterpart and which moreover satisfies the strong and dominant ...
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if a meteorite is moving in space fast enough to generate a lot of mass shouldn't it generate gravity because its moving? [duplicate]

is it how planets form when is happens to have alot of mass to generate a little bit of gravity, oh and bullets for example they generate mass when moving and causes it generate mass?
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Atmospheric pressure

What is the significance of atmospheric pressure being referenced as 100 kPa ? Does that really mean 10000 kg/m$^2$ acting upon us ? If we are measuring only collision force on the surface and not ...
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If photon can bend spacetime how does it exchange graviton?

Say two photons moving beside each other through space at speed of light, since it carries energy it can bend spacetime. So both photons will exert gravitational force on each other at speed of light ...
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Why can't gravitational force have repulsive counter part?

The valleys in the space-time curvature signifies the existence of an attractive body which causes the curvature. So why can't we say that the hills in the fabric of space-time is a source of ...
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Can there be acceleration without velocity?

If I was in a spaceship continually accelerating at $9.81m/s^2 =1g$ in a straight line, I would reach near light speed within a year. On Earth, we are in a gravitational field of $1g$, which ...
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406 views

Zero $g$ in a black hole?

At the very centre of the Earth, masses cancel each other out, creating an effective zero-$g$ environment. Would the same happen in a black hole?
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3D donuts and the centre of a black hole [closed]

I have been trying to imagine ways to visualise the gravitational field of the earth... It's near zero at the outer edges of the atmosphere, strong at sea level, strongest at the quarter point, then ...
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Time dilation and freefall (follow up and simplification) [closed]

A person is four miles up in the atmosphere, and freefalls towards earth. Another person is standing on earth, watching them come down. During this period of freefall, which person experiences more ...