Questions tagged [gravity]
Gravity is an attractive force that affects and is affected by all mass and - in general relativity - energy, pressure, and stress. Prefer newtonian-gravity or general-relativity if sensible.
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Why is a black hole black?
In general relativity (ignoring Hawking radiation), why is a black hole black? Why nothing, not even light, can escape from inside a black hole? To make the question simpler, say, why is a ...
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Can water falling from a tap follow a spiral path?
The faucet design depicted below is driving me crazy. The water falling from the tap appears to follow a spiral path. No one seems to agree whether it is physically possible for the water to spin in ...
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How do we know that gravity is spacetime and not a field on spacetime?
How do we know that gravity is the curvature of spacetime as opposed to a field, which couples equally to all objects, on spacetime?
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Why did we expect gravitational mass and inertial mass to be different?
I've read many times that the fact that gravitational mass is equal to inertial mass (as far as we can tell) used to be a puzzle. I believe that Einstein explained this by showing that gravity is ...
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What does it mean to say "Gravity is the weakest of the forces"?
I can understand that on small scales (within an atom/molecule), the other forces are much stronger, but on larger scales, it seems that gravity is a far stronger force; e.g. planets are held to the ...
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Where does gravity get its energy from?
I would like to know where gravity gets its energy to attract physical bodies?
I know that the law of conservation states that total energy of an isolated system cannot change. So gravity has to be ...
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Would you be weightless at the center of the Earth?
If you could travel to the center of the Earth (or any planet), would you be weightless there?
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How can dark matter collapse without collisions or radiation?
I understand that dark matter does not collapse into dense objects like stars apparently because it is non-interacting or radiating and thus cannot lose energy as it collapses. However why then does ...
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Shine a beam of light horizontally, drop a stone from same height - would both hit the ground at the same time?
If a beam of light was shone horizontally, and simultaneously a stone was dropped from the same height, would they both hit the ground a the same time?
Of course on Earth they would not, but let's ...
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Gravity as a gauge theory
Currently, (classical) gravity (General Relativity) is NOT a gauge theory (at least in the sense of a Yang-Mills theory).
Why should "classical" gravity be some (non-trivial or "special" or extended)...
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Can two heavy objects circling around their C.M. be separated because of the speed of gravity?
Imagine two massive objects, with the same mass (M) circling around their center of mass (C.M.). Let's assume that the distance between them is 1 light hour. Don´t the two bodies get accelerated and ...
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Experimental bounds on spacetime torsion
Did Gravity Probe B provide any bounds on Einstein-Cartan torsion? is a non-zero torsion value at odds with the results regarding frame-dragging and geodetic effects?
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Is the graviton hypothetical?
Wikipedia lists the graviton as a hypothetical particle. I wonder whether graviton is indeed hypothetical or does its existence directly follow from modern physics? Does observation of gravitational ...
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Does the curvature of spacetime theory assume gravity?
Whenever I read about the curvature of spacetime as an explanation for gravity, I see pictures of a sheet (spacetime) with various masses indenting the sheet to form "gravity wells." Objects ...
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The problem of self-force on point charges
Allow me to preface this by stating that I am a high school student interested in physics and self-studying using a variety of resources, both on- and off-line, primarily GSU's HyperPhysics website, ...
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