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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Is this a quaternion representation of the equations of motion of General Relativity?

In The Quaternion Group and Modern Physics by P.R. Girard, the quaternion form of the general relativistic equation of motion is derived from $du'/ds = (d a / d s ) u {a_c}^* + a u ( d {a_c}^* / ...
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149 views

How do gravitational waves sustain and propagate large scale spacetime curvature?

I understand that gravity in GR is a manifestation spacetime curvature dictated by the field equations by the principle that objects follow the geodesic path in spacetime. And, I get how ...
3
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1answer
163 views

Understanding the E=MC2 for multiple objects

Im actually not a very good at physics, but I was playing with this functions (just for fun and education, so this question might end at the Scifi forum), and would like to know if this logic is ...
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1answer
130 views

Can we develop in the future a technology that can send a message to the past? [duplicate]

Possible Duplicate: Is it possible to go back in time? I believe that everything is possible in this world. If that can be done then why aren't we receiving any message from the future.
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463 views

Is spacetime moving in general relativity?

Is spacetime moving in general relativity? If not, how does spacetime retain its past, while moving toward future?
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3answers
369 views

Theory that gets rid of dark matter/energy

Is there any physics theory that either groups together gravity and dark energy/dark matter or eliminates dark energy/dark matter by modifying standard understanding of gravity or any force? If so, ...
2
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150 views

Calculating a Deflection of Light Integral from Einstein's 1907 paper on Gravity and Light

$\frac{1}{c^2}\int_{\theta=-\pi/2}^{\theta=\pi/2} \frac{kM}{r^2}cos\theta ds=2\frac{kM}{c^2\Delta}$ An observation: $\cos\theta=\frac{\Delta}{r}$
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1answer
625 views

Energy conservation and center-of-mass inertial frames

For a given set of fast-moving objects in empty space, the maximum mass-energy that can be extracted by using only interactions between objects in the set (e.g., colliding all of them together) is ...
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1answer
392 views

The Strength Of A Black Hole

Does the gravitational strength of a black hole at its singularity change the more it pulls things into it?
2
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1answer
228 views

Can a charged black hole interact via electromagnetism? [duplicate]

Possible Duplicate: Detection of the Electric Charge of a Black Hole Light cannot escape from a black hole. However light is also interpreted as the carrier of the electromagnetic force. So ...
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1answer
109 views

Does General Relativity require that Spacetime must be a orientable? [duplicate]

Possible Duplicate: Can spacetime be non-orientable? Apart from the constraints put on the topology of spacetime by QFT (Parity For example), if the global topology of a universe is that of ...
0
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1answer
308 views

Gravimagnetic monopole and General relativity

Review and hystorical background: Gravitomagnetism (GM), refers to a set of formal analogies between Maxwell's field equations and an approximation, valid under certain conditions, to the Einstein ...
12
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711 views

Why is there no dynamics in 3D general relativity?

I heard a couple of times that there is no dynamics in 3D (2+1) GR, that it's something like a topological theory. I got the argument in the 2D case (the metric is conformally flat, Einstein equations ...
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1k views

What is the stress energy tensor?

I'm trying to understand the Einstein Field equation equipped only with training in Riemannian geometry. My question is very simple although I cant extract the answer from the wikipedia page: Is the ...
6
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1answer
540 views

Wick rotation and the arrow of time

It is well known that we can switch from a statistical system to a quantum mechanical system by a Wick rotation. Has this rotation some implication on the way the time flow? namely, this is an ...
3
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3answers
199 views

Is the gravity we feel in our everyday life mainly curvature of the time coordinate?

The question is pretty clear I think. I only started learning GR but the results I've seen so far and from some lectures I saw from Leonard Susskind on YouTube I understood that for low energy ...
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1answer
222 views

A Query on the Trapped Null Surface

A a compact, orientable, spacelike surface always has 2 independent forward-in-time pointing, lightlike, normal directions. For example, a (spacelike) sphere in Minkowski space has lightlike ...
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2answers
145 views

Why is matter drawn into a black hole condensed into a single point within the singularity? [duplicate]

Possible Duplicate: Why is matter drawn into a black hole not condensed into a single point within the singularity? When we speak of black holes and their associated singularity, why is ...
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1answer
275 views

How does General Relativity Emerge from Brans-Dicke Gravity with an Infinite Omega Parameter?

The action for the Brans-Dicke-Jordan theory of gravity is $$ \\S =\int d^4x\sqrt{-g} \; \left(\frac{\phi R - \omega\frac{\partial_a\phi\partial^a\phi}{\phi}}{16\pi} + ...
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2answers
631 views

Where do I start with Non-Euclidean Geometry?

I've been trying to grok General Relativity for a while now, and I've been having some trouble. Many physics textbooks gloss over the subject with an "it's too advanced for this medium", and many ...
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3answers
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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 ...
3
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1answer
421 views

Why is matter drawn into a black hole not condensed into a single point within the singularity?

When we speak of black holes and their associated singularity, why is matter drawn into a black hole not condensed into a single point within the singularity?
3
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2answers
355 views

About space-time and its four dimensions

I explained to someone I know about General Relativity (as much as I know). He said that he didn't see how it could be correct. He argued: How is 4-dimensional space-time space different to ...
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5answers
616 views

Are gravitomagnetic monopoles hypothesized?

My understanding is that gravitomagnetism is essentially the same relativistic effect as magnetism. If so, why is it that I've heard so much about magnetic monopoles, but never gravitomagnetic ...
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219 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
405 views

The Black Hole Problem

Consider a spherical body of uniform density $\rho$ and initial radius R. You can imagine this body containing another sphere of radius R/2 which touches the center and the periphery of the larger ...
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1answer
919 views

$\pi$ and the Curvature of Space

If one draws a circle on a sphere and measures the ratio of the diameter to the circumference, that value varies depending on the diameter of the circle compared to the diameter of the sphere it is ...
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1answer
274 views

Is a black hole's surface area invariant for distant intertial observers?

Let's imagine I'm very far from any massive objects, so my local space-time is Minkowskian. Off in the distance is a black hole, far enough away that it doesn't noticeably curve space-time near me, ...
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1answer
228 views

Will a black hole increase the speed of sound above the speed of light in this medium

For the sake of this question we are inside the EH and a sound wave enters from our perspective as the sound moves closer to us at the EH would it speed up. Specifically how would the extreme ...
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0answers
345 views

Newton's Law of Gravitation, Gauss Law and GR

From One of My Unpublished Papers $$\frac{d^2 x^{\alpha}}{d\tau^2}=-\Gamma^{\alpha}_{\beta \gamma}\frac{dx^{\beta}}{d\tau}\frac{dx^{\gamma}}{d\tau} \tag{1}$$ For radial motion in Schwarzschild’s ...
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1answer
143 views

Pseudo-Superluminal Motion and the Synchronization of Clocks

Let's consider two points A an B separated by a finite distance in curved space time. A light ray flashes across an infinitesimally small spatial interval at B. Metric: ...
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1answer
632 views

Curvature of spacetime in only required to explain tidal forces?

I'm a bit confused about the equivalence principle in GR. I'm quoting from Wikipedia: An observer in an accelerated reference frame must introduce what physicists call fictitious forces to ...
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3answers
187 views

Apparent non-aberration of gravity waves

Since GR assumes that gravity waves travel at speed c, we expect we would be able to some day detect an aberration effect similar the that of light. Of course, gravity waves are so tiny in magnitude, ...
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2answers
759 views

Zero divergence of energy-momentum tensor and gravitational energy

Trying to teach myself general relativity and have just hit yet another confusion. I'm reading that in curved spacetime the energy-momentum tensor has zero divergence, ie ...
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1answer
425 views

Geocentric Model in General Relativity

In classical mechanics, if I want to view the Earth as the fixed center of the solar system, I must accelerate my reference frame to keep it centered on the Earth. That accelerated reference frame ...
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2answers
149 views

Effect of gravity at near-lightspeeds

Let's say I'm in a space station, hurtling towards our galaxy nearly close to the speed of light. From my reference frame, I see the galaxy coming towards my ship at the same speed. I pass the Sun, ...
2
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1answer
415 views

General Relativity - Einstein field equation and quantum field theory

Einstein field equation has many solutions. Out of them, is there any solution that is incompatible with quantum field theory? Also, what solutions of Einstein field equation would be incompatible ...
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0answers
185 views

Comparing Lagrangian in Special Relativity vs General Relativity for a weak gravitational field

This is a sequel to this question. Who knows a difference between the Lagrangian in SR and GR for a weak gravitational field in non-relativistic case? What is the reason of this difference?
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1answer
398 views

Does the current acceleration of universe imply that our universe is open?

Does the current acceleration of universe imply that our universe is open? If the universe is closed, from the Friedmann's equation, the acceleration of universe wouldn't be possible, would it be? (Of ...
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2answers
2k views

How is Big Bang related to theory of relativity?

I'm not someone with good scientific knowledge, so if my question are weird, correct me. I was reading about big bang and I came by the theory of relativity. Can someone explain the relation between ...
0
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1answer
266 views

The Light Cone in GR-----A Flickering One?

Events in relativity[SR or GR]are marked by coordinate values and not by physical values.We write a metric for motion along the x-axis: $$ds^2=g_{00}dt^2-g_{11}dx^2$$ ----------- (1) For physical ...
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1answer
703 views

metric signature explanation

Can anyone explain what metric signature is? I have a basic knowledge regarding tensors, btw. Also, how is it related to fundamental understanding of general relativity? Thanks.
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2answers
286 views

Confusion regarding geodesic of thrown ball - curved or Cartesian coordinates?

I'm confused trying to understand what's happening in terms of spacetime geodesics when a ball is thrown and its trajectory plotted, height against time to give a parabola. I read (from more than ...
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3answers
1k views

Why do objects follow geodesics in spacetime?

Trying to teach myself general relativity. I sort of understand the derivation of the geodesic equation ...
1
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1answer
497 views

spacetime expansion and universe expansion?

First of all, does the expansion of spacetime solely cause the expansion of universe? Secondly, if spacetime is the sole cause, do objects(matter with mass) themselves expand? Thirdly, by spacetime ...
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3answers
1k views

Will free-fall object into black hole exceed speed of light $c$ before hitting black hole surface?

In Newtonian mechanics, if we throw an object in against direction of gravity with speed $v$ and it achieve max height of $h$. Now if we allow object to fall from that height $h$, it will eventually ...
5
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1answer
439 views

Interpretation of the Einstein-Hilbert action

Everyone knows the famous Einstein-Hilbert action $S_{EH} = \int d^4x \sqrt{-g} R$. I'd like to know if, after we first explicit the Ricci scalar in terms of the metric, it could be possible to ...
2
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2answers
320 views

How does gravitation propagate along curved spacetime?

In this wikipedia article it is described how a beam of light, with its locally constant speed, can travel "faster than light". That is to say it travels a distance, which, from a special relativistic ...
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467 views

shouldn't gravity travel at light speed immediately

if gravity travels at c(light speed), why aren't objects pulled to earth at that speed? Since the velocity of gravity is 9.8 meters per second squared, will it eventually accelerate until it maxes ...
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763 views

How does the string worldsheet affect the space-time in which they live?

I don't understand much about string theory and never really got much further past the Nambu-Goto action and very basic supersymmetry (SUSY) lectures in my undergraduate courses, but the only thing ...