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 the Earth be ejected when the sun burns out?

My younger brother came home from school today and told us at the dinner table that when the sun burns out the Earth could be ejected from its orbit. Skeptical, I asked his source. He quoted his ...
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Are combined masses in space, such as galaxies, considered to be uniform bodies? *In addition, a related question about force

If we were to calculate the force that one galaxy exerted onto another, would we consider the individual masses within the galaxies, or the masses of the galaxies as a whole? Do the individual stars ...
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50 views

Consequences of inverse square law with vast distances (Gravity); (in addition, is light speed broken)? [duplicate]

As is well known, the gravitational force between two masses is dependent on the spatial distance between them. Therefore, even at vast distances, the masses exert equal and opposite forces on one ...
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132 views

What is the difference between gravitation and electromagnetism?

I am currently studying electrodynamics. And when looking at Maxwell's equations, I don't see any reason, why we cannot apply them to gravity. We know that charges generate a force field that ...
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54 views

Does the earth gets closer to the sun?

We know that the sun loses an amount of it's mass equivalent to the amount of energy it produces, according to the E=mc² equation. so the sun is losing mass every second. Does this affect the ...
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45 views

Chemical effect on gravitation?

We know, that gravitation field of charged black hole is different than one of uncharged. I this true only for objects with singularity or is true for all objects? If true, then may we say, that ...
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80 views

Energy Required to Rip Spacetime

I have heard that the presence of an extremely strong gravitational field possesses the capacity to warp or tear spacetime and to potentially create a wormhole. Is any energy lost when spacetime is ...
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212 views

What is the shape of a rope hanging from two ends

If I hang a rope from two points that are at the same height above the ground, what is the mathematical function that describes the shape of the rope between the two points? Assuming the mass of the ...
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4answers
188 views

Where does the idea gravity=curvature of spacetime really come from?

I have been searching for quite a while but mostly found the answer: Einstein's genius. Quite unsatisfactory. I know and understand that the idea gravity=curvature of spacetime works. Furthermore I ...
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33 views

Falling from Earth's sphere of influence [duplicate]

How can I make a graph of an object falling from say, the Earth's sphere of influence, where acceleration(,a) is the real force of gravity at the objects radius? ie, using $$s=ut+\frac{1}{2}at^2$$ ...
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56 views

Square Cube Law?

I've heard about something called the square cube law. What is it? All I know of it is that it has something to do with mass of large objects and their gravitational influence.
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Can one assign an equivalence principle of some kind to the EM field?

Introduction: Consider the EM field. There was a time when the field was defined in a similar manner to that of the gravitational field. This changed when the view on gravitation evolved to this ...
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How does the weak force between two neutrinos compare with their gravitational interaction?

In short, are there cases where the weak interaction between two neutrinos is actually smaller, in (absolute) magnitude, than their gravitational interaction? There is no principle that forbids this. ...
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changes in horizontal velocity and the effect on time airborne (thus overcoming gravity)

I would like to know if a object is launched horizontally in the air at a lower speed and a higher speed, why does the higher speed keep it airborne longer. what are the forces and why does gravity ...
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74 views

What physical conditions would allow for this kind of perpetual seesaw

I'm working with a simulator(Box2D) and need to create these conditions. I have a perpetual seesaw with two objects on either side. I'd like for the following conditions to be met. The first ...
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1answer
32 views

Galaxy velocity curve

When deriving the relation between velocity of a star and its distance $r$ from the center of the galaxy, one assumes that the masses outside $r$ have no contribution and those inside $r$ give a force ...
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1answer
29 views

maintaining atmosperic pressure on mars

how would mankind be able to maintain an earth like atmospheric pressure on mars since mars only has 1/3rd the mass? I am not, nor have i ever attended college, but am very curious.
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Is there a mistake in this example in my mechanics textbook?

This is a worked example in my mechanics book: But I think this worked example is wrong. In the 6th line. shouldn't $X=4R$ as the expression for distance above the surface is $(X-R)$ and when the ...
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Is $4 \pi G$ the true most fundamental gravitational constant? [closed]

Newton's law of gravitation is: $$F = G m_1 m_2 \frac{1}{r^2}$$ It looks simple and natural. But that's only in 3 dimensions. Let's look what happens in $n$ dimensions: $$n=2 : F = 2 G m_1 m_2 ...
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What was the Law of Gravity better explained by?

In mechanics, our professor made the declaration that "all laws of physics" have been disproven. He mentioned several examples including the Law of Gravity, mentioning briefly that it is better ...
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Magnetic fields and forces, Gravitation fields and forces

Is a current carrying wire affected by the magnetic field that it produces? In other words, will a current carrying wire be acted on by a magnetic force produces by its own magnetic fields? Is a mass ...
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Does the conversion of crude oil to greenhouse gases have any measurable effect on earth's gravitational pull?

Oil underground is much denser than greenhouse gas in the atmosphere. Does the conversion in anyway effect the gravitational force from earth.
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How did gravity affect gas clump after the big bang

In the first episode of Cosmos. It was said that after the big bang, gravity worked to pull clumps of gas together and heating them. My question is what was exerting the gravitational pull to make ...
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Statements about gravitational potential energy contradicting intuition?

So in my textbook I am told: two masses have gravitational potential energy because work had to be done in order to move one the masses form a position very far away (lets say infinity) to the ...
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What limitations are there in measuring physical properties accurately?

In a StackOverflow answer, I attempted to explain why a 32-bit float was perfectly adequate for representing the questioner's weight measurement: Physical properties are inaccurately measured ...
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3answers
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Speed/direction of gravity for a moving source [duplicate]

Consider the Earth, and a bowling ball held 186,000 miles (1 light second) above it. When the ball is released, it will start to fall vertically downwards towards the Earth. Now consider the case if ...
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Artificial gravity on rotating spaceship?

One of the possible ways to simulate gravity in outer space is to have a rotating spaceship, so that the centrifugal force experienced provides a gravity-like force. My question is: shouldn't this ...
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1answer
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Hydrostatic pressure at the center of a water planet [duplicate]

If we take an imaginary planet which consists entirely of water (i.e. a big ball of water in space), what would be the pressure at the center of it? My friend argued that it would be zero, since the ...
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Why not shoot a marble sized spacecraft at the moon?

I was thinking about the Google XPrize for Space Travel the other day. In order to claim the prize of building a robot that goes to the moon, travels 500m, and relays data, I had the idea of building ...
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73 views

Bose Einstein condensates and gravity

Are Bose Einstein condensates affected by gravitational attraction ? In sufficient quantity, do Bose Einstein condensates exert a gravitational force ?
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How close does light have to be, to orbit a perfect sphere the size and mass of Earth?

The moon orbits Earth at about $380,\!000 \,\mathrm{km}$ away from it, at around $3,600 \,\mathrm{km}$ an hour. I was thinking, with light traveling at $300,\!000 \,\mathrm{km/s}$, how close to ...
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1answer
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Gravity fed containers

Curiosity got the better of me, and was wondering if you have two containers full of sand each at different heights but both fed in a tube from a with the containers being in Y configuration, is there ...
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3answers
118 views

About the speed of light and gravity

I read (I think ) that part of relativity theory is that a strong gravitational field distorts the uniform passage of time. If this is true and a lightwave 'travelling' to Earth passes a star near ...
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1answer
84 views

Escape velocity problem

I was given a problem at school: How much Energy do we need to make a rocket of mass $m$ faster than the escape velocity so that it can travel in outer space? Here's how I worked: I know that ...
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539 views

Is gravitational time dilation fundamentally different than other forms of time dilation?

Is gravitational time dilation caused by "Gravity"...or is it simply an effect of the inertial force caused by gravity? Is gravitational time dilation fundamentally different than time dilation due ...
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How might eddy currents and terminal velocity be broken down?

This is a branch from this question. With regards eddy currents and terminal velocity I have located a homework question but would appreciate more detail (and translation of the symbols described ...
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Why does gravitational collapse occur suddenly in a supernova progenitor?

I was reading the Wikipedia article on Supernovae, and it says that one of the reasons why a supernova occurs is due to sudden gravitational collapse when the core of the star has little fusable ...
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3answers
613 views

Gravitational doubt [duplicate]

If we can shield a charge from electrical forces by putting it inside a hollow conductor. Can we shield a body from gravitational influence of nearby matter by putting it inside a hollow sphere or by ...
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1answer
92 views

Do Gravitational Waves Actually Repel Spacetime?

I read something explaining that g-waves actually repel space-time. It described the following. Mass bends space-time creating gravity. An object like the sun, if it suddenly disappeared the ...
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1answer
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What is the maximum current carrying capacity of a Josephson tunnel junction?

In 1962, Josephson predicted that for a sufficiently thin insulating layer, it should be possible for Cooper pairs to tunnel between two pieces of superconductor. With a potential difference $V$ ...
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Does dark matter get drawn into black holes? [duplicate]

Would dark matter get drawn into a black hole? Also, could enough dark matter be concentrated to create a "dark black hole"?
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1answer
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Modified gravity and dark energy

Is there a model of modified gravity that either was close to or have succeeded in modelling the problem of dark energy, and suffers from no instabilities and explains the observational data. Also has ...
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66 views

Why does gravitational lensing bend light rather than absorbing it?

I've read that gravitational lensing bends the light; I am a little confused about black holes and why lensing produces different results. Black holes absorb light whereas lensing should have also ...
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2answers
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Photons emitted at the event horizon?

While looking through the questions, a came across a section about black holes. I immediately though; what would happen if an atom is orbiting a black hole and emitted a photon perpendicular to the ...
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2answers
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Why do we orbit around the sun instead of one the other stars?

I am still very new to many physics theories, however while sat in class today, a thought came to mind that I have not been able to answer from simple googling. What is so specific about our sun ...
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Can He-4 atoms create black holes?

Suppose that in the intergalactic space far from any significant gravitational attractors there is a relatively small concentration of He-4 atoms. Due to gravitational attraction fermions in this case ...
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Relative effects of forces

Excuse me for my ignorance but I really couldn't find a solution. According to Einstein, every happening is possible to describe by both of interacted objects. Is there any other way to describe the ...
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1answer
58 views

Roche Limits and black holes

I am curious due to the course of the idle research that I am doing (my hobby), and I am curious for various reasons as to the answer of this question. Please forgive me in advance for possible ...
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0answers
60 views

Visualizing Tension in FBD — Rope With Mass

Asked to find the tension of a point that is halfway up a rope (where the rope has mass), given the system: The solution of the problem (FBD included) is as follows. In this diagram (Tm = tension ...
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1answer
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Physics behind a match performing a trick on center of mass

https://www.youtube.com/watch?v=Ucdw0DDI4n8 I've seen another variation where the whole match stick turned to ash. What's going on in this trick?