A theory that describes how matter produces and responds to the geometry of space and time. It was first published by Einstein in 1915 and is currently used to study the structure and evolution of the universe, as well as having practical applications like GPS.
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459 views
Does a Weak Energy Condition Violation Typically Lead to Causality Violation?
In the answer to this question: ergosphere treadmills Lubos Motl suggested a straightforward argument, based on the special theory of relativity, to argue that light passing through a strong ...
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2answers
353 views
Why is Mendel Sachs's work not taken seriously? Or is it?
Back in college I remember coming across a few books in the physics library by Mendel Sachs. Examples are:
General Relativity and Matter
Quantum Mechanics and Gravity
Quantum Mechanics from General ...
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2answers
114 views
Does gravitational redshift imply gravitation time dilation?
The EEP is used to justify that if an observer on the ground shoots a beam of light towards a tower, then when the light reaches the tower, it will be red shifted. This is because of what happens in ...
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2answers
89 views
Does the distance to the cosmic horizon Lorentz-contract? Does the universe Lorentz-contract?
Our universe has a finite size. It is often called the "radius of the universe", or "distance of the cosmic horizon".
If we would fly with relativistic speed at the position of our Earth, would this ...
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2answers
141 views
What's the relationship between quantum entanglement and the relativity of time?
Apologies in advance for what may be a stupid question from a layman. In reading recently about quantum entanglement, I understood there to be a direct link between entangled particles, even at ...
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2answers
137 views
General Relativity & Kepler's law
According to Kepler's law of planetary motion, the earth revolves around the sun in an elliptical path with sun at one of its focus.
However,
according to general theory of relativity,
the earth ...
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2answers
99 views
The relativistic mechanics of a battery that is being charged and accelerated at the same time
This might be an interesting question:
Let's attach a battery into one end of an electric cable. Then we rotate the battery around, with accelerating speed, using 100 Watts of power, while the ...
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2answers
191 views
Is the Graveyard Really so Serious?
Calculations in relation to black holes are solely in consideration of spacetime curvature and its effects. They are in total alienation with respect to the action of inertial agents[external ...
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1answer
180 views
What does the equivalence principle mean in quantum cases?
We know that electron trapped by nuclear, like the hydrogen system, is described by quantum state,and never fall to the nuclear.So is there any similar situation in the case of electron near the ...
6
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1answer
275 views
Do spacelike junctions in the Thin-Shell Formalism imply energy nonconservation and counterintuitive wormholes?
The Thin Shell Formalism (MTW 1973 p.551ff) is used to properly paste together different vacuum solutions to the Einstein equations. At the junction of the two solutions is a hypersurface of matter – ...
4
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1answer
87 views
“Redshifting” of forces in stationary space - times
Here's the problem statement:
Let $(M,g_{ab})$ be a stationary spacetime with timelike killing field $\xi ^{a}$. Let $V^{2} = -\xi _{a}\xi ^{a}$ ($V$ is called the redshift factor).
(a) Show that the ...
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1answer
92 views
Liouville's theorem and gravitationally deflected lightpaths
It is customary in gravitational lensing problems, to project both the background source and the deflecting mass (e.g. a background quasar, and a foreground galaxy acting as a lens) in a plane.
Then, ...
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1answer
68 views
Could a bipolar nebula be produced by a time gradient?
M2-9 is an example of a bipolar nebula that resembles two back-to-back rocket nozzles. Is it possible that this shape (somewhat unusual for an explosion) is the result of a time gradient? A rotating ...
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1answer
106 views
Rotation of Spacetime => Change in orbit/path
Along the idea of frame-dragging;
Will the rotation of a black hole, which has some velocity v and angular momentum, influence its path in 3D space?
I've seen the fact that depending on the ...
2
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1answer
252 views
Gravitational Redshift around a Schwarzschild Black Hole
Let's say that I'm hovering in a rocket at constant spatial coordinates outside a Schwarzschild black hole.
I drop a bulb into the black hole, and it emits some light at a distance of $r_e$ from the ...
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1answer
237 views
Why dynamic Casimir effect does not appear in static gravity field?
Dynamic Casimir effect tells us that a constantly-accelerated mirror should emit radiation due to interaction with vacuum. Following principle of equivalence, a similar mirror placed in static ...
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1answer
14 views
Can we build a synthetic event horizon?
If we imagine ourselves to be a civilization capable of manipulating very heavy masses in arbitrary spatial and momentum configurations (because we have access to large amounts of motive force, for ...
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1answer
51 views
Local inertial coordinates
It is said that we can introduce local inertial coordinates for any timelike geodesic. But why only for timelike geodesics? What about null geodesics? Perhaps it has to do with invertibility or ...
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1answer
86 views
How can the derivative of this trace be constrained?
I am studying for my exam on relativity and I am going through some problems sets including ones where I was not very successful in so I want to know how to do this problem.
(Convergence of ...
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1answer
55 views
Gravitational time delay and contraction of matter
How can any matter contract to its Schwarzschild radius if gravitational time dilation clearly states that all clocks stop at that point. So any contraction any movement would stop. If that is so why ...
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1answer
55 views
A physical sense of an Inertial frame
Definition clarification needed, please: I am hoping to get physical sense of an "inertial frame".
Do inertial reference frames all have zero curvature for their spacetime?
So is an inertial frame ...
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1answer
122 views
Why does weak equivalence principle say gravity is equivalent to acceleration?
I am told that the weak equivalent principle, that $m_i=m_g$ (inertial and gravitational masses are equivalent) is equivalent to the statement that in a small system you can't tell whether you are in ...
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1answer
248 views
warp drive with gravitational waves in the nonlinear regime
gravitational waves are strictly transversal (in the linear regime at least), also their amplitudes are tiny even for cosmic scale events like supernovas or binary black holes (at least far away, ...
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0answers
254 views
Gravitation and the QFT vacuum
I'm asking this to get yet another lessson in the inability of QFT and GR to cohabit. Many people believe GR must yield to quantization. The question here is as to why the activity of the vacuum ...
