Questions tagged [general-relativity]

A theory that describes how matter interacts dynamically with 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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Does mass gives a object/particle a decrease of time dilation and length contraction?

And that’s why a photon don’t experience time and distance because he experience total time dilation and length contraction?
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What is $\frac{\delta (\partial_\kappa \sqrt{g})}{\delta g^{\mu\nu}}$?

Title says it all, is there a closed expression for $$\frac{\delta (\partial_\kappa \sqrt{g})}{\delta g^{\mu\nu}}$$ where $g = \det g_{\mu\nu}$?
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If strong gravitational fields bend and slow down time, how can travelling near the speed of light do the same?

I was wondering how travelling near the speed of light could slow down time, seeing that light approaching a strong gravitational field would get curved and therefore reach its destination in a longer ...
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By changing the direction of velocity of all particles does time reverse, as well as the development of the wavefunctions and the expansion of space?

If (in our mind) we reverse the velocity of every elementary particle in the Universe, does time reverse too? And if so does the same happen to the development of the all the wavefunctions and the ...
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How rotation affects geodesics on earth (Gravity Probe B)?

What situation gives Gravity Probe B or frame-dragging after 16 million years ? If light is following space-time geodesic and light is bent in Kerr metric (instead of straight in Schwarzschild) ...
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How can they see 1 day and 23 years at the same time in the gravitational twin paradox of Interstellar movie?

In the middle of the movie Interstellar, a crew of astronautes land on Miller's planet. For them only one day passed. For the one astronaute left in the station, 23 years passed. If we admit there is ...
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In TOV equations of hydrostatic equilibrium

in TOV equations of hydrostatic equilibrium $\{P(r),M(r),v(r)\}$ are coupled with 1st order and $P(r)$ , $M(r)$ have initial values at $r=0$ but $v(r)$ is at the boundary of the star. Therefore, when ...
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Should Einstein's Field Equations be modified when using conformal time?

Let us consider the FRW metric for flat space expressed in terms of conformal time $\eta$ and cartesian spatial co-ordinates $x,y,z$: $$ds^2=a^2(\eta)\{d\eta^2-dx^2-dy^2-dz^2\}.$$ As in the standard ...
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Matter beyond event horizon

Assuming that antimatter is matter with time arrow reversed, would it be right to say that matter beyond black hole event horizon then would become antimatter because of space and time axes exchanged? ...
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Should any matter form a singularity before crossing the event horizon?

I guess the destiny of any object that falling into a black hole will depend on its size and the density of the black hole it falling in. And from distant observer it should looks different. A small, ...
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Is the spacetime for gravity described with gravitons flat?

Gravity has two equivalent descriptions. One is general relativity, the other is the mechanism by the exchange of gravitons. Is in the latter the spacetime flat?
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Comparing durations for two simply described motions in Schwarzschild geometry

I have some basic qualitative questions about the setup with: one satellite $A$ orbiting freely, on a stable circular path, a spherical non-rotating object of mass $M$; and another participant $B$ ...
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Nomenclature “Material System”

This is just a quick question about nomenclature from General Relativity. Most textbooks refer to "material systems"; 1) Does a material system have to be a system with mass? or can it just be a ...
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Do Quantum Mechanics At The Macro Scale Disprove General Relativity or Prove Something New?

We all know about the discrepancy between relativity and quantum physics at the scale relative to particles. Wouldn't the fact that recent experiments show quantum effects at the macro-scale in some ...
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Time and gravity relation

I was reading about relativity when I crossed by the applications of relativity in real life, and they said that as the elevation increase time increase so gravity decrease Can someone explain to me, ...
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black holes and white holes

i have a question and i just couldn't get another way to get its answer. My question is regarding black hole and the possibility of a white hole. we know that even light cannot escape a black hole ...
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Infinite gravity

We know that gravity works at an infinite distance. By Einstein's theory of gravity it is the result of space time curvature. So can we say that the curvature is infinitely long? How can this be even ...
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Is there a name for the linear quantity corresponding to the (quadratic) “interval $\Delta s^2$”?

Recently it has been affirmed here (again) that the quantity called "interval (also 'spacetime interval' or 'invariant interval')" is referring to two (in general distinct) events as arguments, such ...
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Does the apparent radius of the event horizon of a black hole depend on the distance of the observer from the black hole?

Does the apparent radius of the event horizon of a black hole get smaller and smaller as an observer approaches a black hole? If this were true, it would seem to allow communications to be relayed ...
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Repulsive gravity formulation: a query

I was going through this arxiv paper by Magnano: gr-qc/9312008 For modeling non linear and repulsive gravity he takes the generic lagrangian $$L = f(R)\sqrt{-g}.$$ Varying this $L$ with $g^{\mu\nu}$, ...
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How can matter falling into a black hole make it grow?

None of the answers to this question or this question answer my question. Once an object falls past the event horizon, it can no longer act as a source of gravity. Also, if one tiny object falls into ...
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Given a Spacetime in terms of Lorentzian distance values, how to determine which pairs of events were spacelike separated?

The geometric relations between pairs of events of a spacetime $\mathcal S$ can generally be characterized by values of Lorentzian distance (cmp. J.K.Beem, P. Ehrlich, K.Easley, "Global Lorentzian ...
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What is the covariant derivative of the Ricci Tensor?

How do I take the covariant derivative of the Ricci Tensor? Could someone be so kind as to give me the process of how it is done?
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do rockets follow a straight path but is looks curved because of space time?

does path of the rocket or anything going straight up will look curved because the mass of the earth is curving space time but if we assume the earth, the rocket and all the celestial bodies whose ...
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Why being invariant under the Lorentz transformation is so sacred for inertial observers?

I know that equations are invariant under the Lorentz transformation in SR, and thus if the lab observer measures that the moving observer's clock runs slower, the same is done from the viewpoint of ...

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