# Tagged Questions

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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### Gravitational waves' Amplitude

Gravitational waves are disturbances in gravitational field which in turn is the curvature of space-time. So my question is it possible to somehow measure the amplitude of a gravitational wave and if ...
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### 'Hovering' light rays on the edge of a black hole

According to Prof. Hawking, light rays will 'hover' on the edge of a black hole. If this is true, and the light 'stops' on the edge, how can the electric/magnetic fields which, constitute the light, ...
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### Is mass per surface area / gravity a constant?

While playing with an online calculator for planetary parameters I found I was consistently getting 1.17E+10 kg/m^2 making a surface gravity of 1g. This seems to hold anywhere from degenerate mass (...
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### About relativity [duplicate]

We know that the curvature of spacetime is gravity itself and it is not a force.so,why do we feel our weight in a curve spacetime but not in a straight(I mean not curve) space time like zero gravity ...
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### Gravitational force would also be a fictitious force based upon a field model in which particles distort spacetime due to their mass [duplicate]

Then why does theories of quantum gravity treats gravity as a fundamental force
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### Testing General Relativity using radioactivity on the Moon

I was reading a question involving an ultracentrifuge to test General Relativity. Instead of using an atomic clock the asker posited using radioactive decay as the metric to evaluate time dilation ...
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### Negative Mass's Effect on Gravitational Time Dilation [duplicate]

When I was playing around with the equations for Gravitational Time Dilation, I discovered that when a negative value was plugged in for $M$, the equation gave the exact same answer, and it would ...
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### Why doesn't the earth collide with the sun in 64 years?

According to another answer on this site, the time it takes for two bodies in space to collide can be computed with the following formula: $$\frac{\pi}{2\sqrt{2}}\frac{r_0^{3/2}}{\sqrt{G(M+m)}}$$ ...
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### Universe Expanding

Quick question that I was just hoping to get some clarification on. Current theories state that the universe is expanding; with those planets farther away moving away from us at a faster rate. Is it ...
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### Why does two masses with energy attract each other?

I have heard that every mass attract another mass with a force directly proportional to the multiplication of their masses and inversely proportional to the square of distance between them, but newton ...
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### Gravity and circular logic [closed]

My research into gravity indicates that warped spacetime, with time as the major influence, is gravity. It also indicates gravity causes time dilation. Why is this not a circular argument. It is ...
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### What kind of fundamental interaction is gravitation?

Einstein showed that gravitation is not a force but a effect caused by curvature of space time. Then why does theories of quantum gravity treats gravitation as one of fundamental force?
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### Does gravity exist between quarks in a neutron?

Does gravity exist between quarks in a neutron? I mean, I've learned that gravity exists between objects that have mass/energy. But does this apply between quarks in a neutron?
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### How does Modified Newtonian Dynamics (MOND) violate Newton's laws?

I have read some articles on MOND which indicate that a modification of gravity violate Newton's third law, but I don't know how exactly that works. I do know that if Newtonian acceleration is smaller ...
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### Why are black holes black? [duplicate]

If heard two explanations for this. One explanation is that the gravity is so strong that space is being stretched inward faster than the speed of light and thus no photons could possibly escape. The ...
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### Does curved spacetime arise from inhomogeneity of gravitational field?

In general relativity textbooks such as Sean Carroll's Spacetime and Geometry, there is often a line of reasoning that goes like this: Strong equivalence principle states that free falling frames ...
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### Centripetal and Centrifugal force

If water stays in a pail of water that is whirled around a circular path, the water stays in the pail. But is it because of centripetal force or inertia? I'm getting confused by all the different ...
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### Tidal effect on pressure at sea floor

The tidal movement of water is explained by the gravitational changes due to the movement of earth, sun and moon. So simply thought, sea water climbs higher in areas where the sum gravitation is ...
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### How does the inclusion of vacuum energy modify Newtonian gravity equation of motion?

The equation of motion (in the center of mass frame) due only to gravitational forces between two point masses is: $$\frac{d^2r}{dt^2} = -\frac{GM}{r^2}$$ How does the equation get modified when a ...
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### Any method to determine the gravitational constant $G$ from observations in cosmological scale?

By the observations in cosmological scale, I mean observations by astrophysicists like motions of quasars in far distance from us, relative motions of our galaxy to others, etc. I know the famous ...
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### Is this video's notion of general relativity correct? [duplicate]

In this video it explains the path of the apple in the general relativity version of gravity as being a straight line on a curved surface. Is this valid? Edit: this isn't a duplicate of the supposed ...
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What are the conditions at which free fall occurs? If a body is falling freely under the effect of gravity only without external resistance, the motion is called free fall. This definition gives me ...
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### Is it possible to find the G forces of one of the axis rather than the total?

I am investigating the g-forces and acceleration experienced on roller coasters and have data for $x$, $y$ and $z$ acceleration every $0.2$ seconds of the ride as well as the total acceleration and ...
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### Space time curvature and gravity [duplicate]

Is Space time curvature responsible for gravity or Gravity responsible for the curvature in space-time.
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### Distorting the space-time fabric

If point masses could be generated in a controlled manner distorting the fabric of space-time objects could be made to move in any direction relative to each other and not simply attract as is ...
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### Gravity Theory Question [closed]

Three Questions: Is the Modern Five Dimension Theory of gravity an adaptation of Einstein's relativity theory? If so, can it allow us to accurately predict the movement, speed and direction of ...