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.

learn more… | top users | synonyms (1)

5
votes
1answer
97 views

Two places having same gravitational acceleration - Do they also have same curvature of space time?

If there are two places (possibly on/above two different planets) having same gravitational acceleration (g), would it imply that the two places have same extent of space time curvature and will have ...
0
votes
1answer
45 views

Is there a parametrization for the shape of space?

I was thinking about how the space is curved. And how do we know that the shape of space arround a singularity is something like that: So I was trying to make a similar parametrization of this kind ...
3
votes
1answer
97 views

Is there a path to go from GR, to Gravitational Waves, to Gravitational Particles (Gravitons), to Quantum Gravity?

The articles on the subject often say : a part of the mass of the 2 celestial bodies became energy for gravitational waves after merging : E(gravity waves) = (M1 + M2 - M_merged).c^2 Intuitively I ...
0
votes
1answer
58 views

Is the correspondence between our universe and cellular automata in the presence of time travel just co-incidence? [closed]

I've written a paper discussing a modification to the game of life. Essentially, the traditional game is modified so that a cell is alive if there are 5 or 6 alive neighbours in total across the ...
2
votes
1answer
73 views

Dirac equation from a vierbein operator?

Klein-Gordon equation can be derived straightforwardly by getting the mass-energy relation from special relativity in tensorial form, $$\eta^{\mu\nu}p_{\mu}p_{\nu} = m^2c^2$$ and promoting the ...
0
votes
1answer
126 views

About the LIGO result and Abhas Mitra [closed]

Well I read this article https://en.wikipedia.org/wiki/Abhas_Mitra and he has claimed that "The so-called massive Black Hole Candidates (BHCs) must be quasi-black holes rather than exact black holes" ...
1
vote
2answers
101 views

Is Time Dilation in GR Simply a Consequence of Curved Space?

My understanding of time dilation in General Relativity is that it is the consequence of particles traveling at the speed of causality following longer, curved paths. Since it takes longer for two ...
2
votes
3answers
143 views

Gravitational wave detection and electromagnetic counterpart

Background Referring to this article on Fermi EM signal, 0.4 s after the gravitational wave detection by LIGO, FERMI detected an electromagnetic signal (poorly localized) with a false alarm ...
1
vote
0answers
73 views

Einstein's relativity of simultaneity train/embankment thought experiment

Einstein's thought experiment I'm referring to is this one: http://www.bartleby.com/173/9.html briefly: train/embankment experiment is where lightning strikes at either ends of the running train (...
1
vote
0answers
42 views

Can nonconserved energy in GR be thought of as going into gravitational field energy?

One of the most striking features of GR is that energy is not conserved. Carroll's GR text has an interesting statement about this: Clearly, in an expanding universe... the background is changing ...
1
vote
1answer
79 views

Is it possible to travel faster than the speed of light under extreme warping of spacetime?

The event horizon of a black-hole is defined as the point at which light itself cannot escape, supposedly due to a black-hole's immense gravity and effect on spacetime. However, would this not require ...
0
votes
4answers
105 views

Theoretical Possibility of “Opposite” Gravitational Mass? [duplicate]

This is an unusual idea that I have been entertaining for some time, and I can't find anything about it online. However, it is so simple that someone must have conceived it before. First, I will ...
3
votes
2answers
133 views

Finding geodesics: Lagrangian vs Hamiltonian

I have a question referring to how to compute geodesics of a given spacetime (say, Kerr). I know that the direct way is via the geodesic equation $$\frac{d^{2}x^{\mu}}{d\lambda^{2}}+\Gamma^{\mu}_{\...
0
votes
0answers
22 views

Gravitational Ripples [duplicate]

Recently the observance of Gravitational Ripples was reported using the LIGO detector. LIGO consists of two arms perpendicular to each other through which a split laser beam is passed and then ...
0
votes
0answers
65 views

Which formula was used to get Gravitational Waves animation?

I would like to make animation like this by myself It is from wikipedia article "Gravitational wave". But if I use formula from wikipedia article "Gravitational wave" subsection "7.2.2 Wave ...
0
votes
1answer
83 views

What field property may allow faster than $c$ speed?

What field property may allow faster than $c$ speed? Is there theoretical field or what property it needs to have to allow wave speed larger than $c$? What is the speed of the gravitational wave? Is ...
2
votes
1answer
65 views

Gravitational waves induce changes in the $h_{00}$ (time) component of the metric?

I'm rather stumped by a subtle point regarding metric perturbations of GW. I'm well aware the GW are able to produce changes in the flat space metric, They are transverse and have planes of ...
2
votes
2answers
95 views

How does the general relativity describe the pressure?

The general theory of relativity describes the gravity as a geometrical feature (in very twisted geometry). That's comprehensible to me when the motion occurs and "the most straight" trajectory is to ...
1
vote
1answer
78 views

LIGO: Importance of photons

In LIGO, a photon beam travels in two perpendicular direction and time taken by each beam is noted. Non zero time difference is a signature of GWs here. What if I use electron beam travelling at ...
0
votes
2answers
45 views

What is the relationship between the flow rate of time and gravitational field?

I have heard, qualitatively, about the fact that time's rate of flow slows when the gravitational field is "strong". Here I am looking for some more rigorous descriptions of this phenomenon. My first ...
1
vote
3answers
138 views

Is the local Lorentz transformation a general coordinate transformation?

There is a saying in Nakahara's Geometry, Topology and Physics P371 about principal bundles and associated vector bundles: In general relativity, the right action corresponds to the local Lorentz ...
4
votes
0answers
104 views

General Relativity as a Special Relativistic Field Theory

In this question, I want to consider only the classical case. I have seen the statement that general relativity can be considered as a spin-2 field living on a Minkowski background. In that case, you ...
4
votes
3answers
237 views

Gravitational self-interaction

Today, someone asked me why "the warped space-time warps itself" (he read it in Kip Thorne's: The Science of Interstellar). I guess this is related to the gravitational self-interaction. But I don't ...
3
votes
0answers
86 views

How much energy can be radiated as gravitational waves from black hole merger?

In the black hole merger, recently observed by LIGO, about 5% of energy was irradiated in form of gravitational waves. source of data Is there any theoretical limit to how much energy can be ...
1
vote
1answer
101 views

$AdS_5$ Schwarzschild Black hole Temperature

This question is an extension of my previous Phys.SE question, but now in $AdS$ spacetime. I am attempting to derive the Temperature of the Schwarzschild solution in this space, which is given by: $$-...
0
votes
1answer
106 views

The equivalence principle and identifying free-fall as a locally inertial frame

As far as I understand it the equivalence principle in general relativity is the statement that a frame at rest in a uniform gravitational field is equivalent (indistinguishable) to an accelerated (...
1
vote
1answer
88 views

GR Tetrads & ZAMO example

I am self-learning GR. Intro: Tetrads are a way of representing general relativity in a coordinate-independent fashion. I am having trouble understanding tetrad notations. Basically, I know that I ...
1
vote
1answer
77 views

Difference between local inertial frame and coordinate chart

In the most cases the local inertial frame is definied "physically" but I'm searching for a mathematically meaningful definition of the local inertial frame to solve my problem: Is the local ...
3
votes
2answers
117 views

Can we make any implications about the internal structure of black holes from the 'chirp' that LIGO observed?

Are there any implications about a black hole's internal structure we can make based on the chirp issued? For example that a black hole does in fact contain or does not contain a singularity rather ...
2
votes
2answers
118 views

How does some of the black hole (BH) mass escape the event horizon (EH) of either BH, or the merged EH of two merged BHs?

BH mass is a conserved quantity and cannot escape the horizon of a BH. Yet in mergers some percent (in GW150914 it was about 5 percent, or 3 solar masses) of the binary's mass escaped either before (...
1
vote
1answer
59 views

Vibrating black holes

From http://ligo.org/science/Publication-S5S6RD/index.php "Every star in the universe vibrates or oscillates in some manner. Turbulence on the surface of the Sun causes well-known solar oscillations ...
1
vote
0answers
36 views

Can a micro black hole hover above a regular black hole?

So let's say you have a black hole $A$, that is small enough for its gravity to be very small, but has strong hawking radiation, and larger black hole, $B$, with very small hawking radiation, but ...
1
vote
2answers
236 views

Why does LIGO have an arm length of few kilometers? Is the distance dependent on Gravitational Wave wavelength?

Antennas for capturing radio waves need to have $\frac{\lambda}{2}$ length for optimum reception of signal. Does it imply LIGO arm length is $\frac{\lambda}{2}$ of Gravitational Wave it is trying to ...
1
vote
0answers
29 views

How is a black hole formed? [duplicate]

As far as I know, whenever we talk about a black hole, we refer to a static or stationary solution to Einstein field equations. I know the formation of a black hole can be discussed by the numerical ...
1
vote
1answer
65 views

When we spin and feel our arms fly, is it the effect of gravity?

If accelerating reference frames can be treated as normal inertial reference frames but with gravity, then for a rotating reference frame, is the centrifugal force = gravity? More specifically, I was ...
-12
votes
1answer
301 views

Could the September 2015 LIGO gravity wave “detection” from “merging black holes” be fake? [closed]

The following Physical Review D article gives reasonable bounds for gravitational wave detection for Supernova core collapse. These bounds cannot be overwhelmingly different from the bounds on GW ...
1
vote
0answers
57 views

Physical and non-physical solutions to Einstein's field equations

Einstein predicted gravitational waves in 1916 as a solution to his field equations. Apart from doing experiments, is it possible to tell which solutions exist in the real world and which don't? Are ...
0
votes
1answer
115 views

How can a five-dimensional black hole 'break' general relativity? [closed]

By the laws of general relativity and the existence of black holes, what makes our universe to be just 4 dimensional but not 5 or more because a 5-d black hole can violate theory of relativity? ...
2
votes
3answers
120 views

How can geometrized units have more than one constant equal to 1?

I can understand how you could manipulate units to make a certain constant equal to $1$, like $c$ or $G$, et cetera. But how can you make it so two constants (in this case $c$ and $G$) are equal to $1$...
1
vote
3answers
122 views

Practical time travel: time dilation above the event horizon

Imagine there is a huge black hole with very small gravity gradient so that one doesn't get killed by spaghettification after even nearing the event horizon. Now imagine a very curious creature ...
0
votes
4answers
72 views

Are we sure that there are at most x different types of black holes?

If I'm not mistaken, there are a limited different types of black holes. Depending on were I look, the black holes are categorizes according to size, or categorized according to surroundings and ...
5
votes
4answers
165 views

Is the energy released by gravitional waves kinetic energy or converted rest mass?

It is said that at the binary black hole collision LIGO detected recently, the energy equivalent of 3 solar masses has been released. Since no matter can escape a black hole, the only source I can ...
-1
votes
1answer
77 views

Special relativity - Nokton theory [closed]

Is this theory described in this link Nokton theory respects special relativity conditions.
1
vote
3answers
100 views

Effect of Gravitational Waves on light?

We all know about the gravitational lensing effect. From the analogy of fabric of space time used to explain this concept to laymen like me, i understand that light follows the curvature of spacetime. ...
3
votes
3answers
123 views

Can light escape a black hole? [duplicate]

I heard that a black hole is not black because it's escape velocity is greater than or equals to the speed of light. But instead it is black because the light that gets emitted from a black hole gets ...
1
vote
1answer
74 views

Is this actually how gravity is illustrated? [duplicate]

In general relativity, gravity is said to be caused by the curvature of space time. And there are examples that illustrate gravity such as this video https://www.youtube.com/watch?v=MTY1Kje0yLg, and ...
7
votes
1answer
121 views

Gravity with more than one metric tensor

As weird as it sounds, yes, there are gravity theories with more than one metric tensor. This is called bimetric gravity. My question to those who have encountered bimetric gravity before: a) ...
0
votes
1answer
76 views

Trouble in understanding spacetime

I have a problem in understanding spacetime. What i understood from the conversion of time to distance is that the interval between any two events is always the same for any observer. But how is that ...
6
votes
2answers
114 views

Scanning the universe - edit: expanding or shrinking

I know that this may sound as a very basic question, but how come that we can detect CMB radiation, light or gravitational waves from the big-bang era? Shouldn't this radiation has overtaken us a ...
6
votes
3answers
367 views

How does the curvature of spacetime exert a force on a stationary object?

I understand the idea that, when spacetime is warped by a large mass, objects that try to travel in straight lines instead move along curved geodesics, something Newton would describe as an ...