What is General relativity: Definition and 999 Discussions
General relativity, also known as the general theory of relativity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of partial differential equations.
Some predictions of general relativity differ significantly from those of classical physics, especially concerning the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light. Examples of such differences include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the gravitational time delay and singularities/black holes. The predictions of general relativity in relation to classical physics have been confirmed in all observations and experiments to date. Although general relativity is not the only relativistic theory of gravity, it is the simplest theory that is consistent with experimental data. Unanswered questions remain, the most fundamental being how general relativity can be reconciled with the laws of quantum physics to produce a complete and self-consistent theory of quantum gravity; and how gravity can be unified with the three non-gravitational forces—strong, weak, and electromagnetic forces.
Einstein's theory has important astrophysical implications. For example, it implies the existence of black holes—regions of space in which space and time are distorted in such a way that nothing, not even light, can escape—as an end-state for massive stars. There is ample evidence that the intense radiation emitted by certain kinds of astronomical objects is due to black holes. For example, microquasars and active galactic nuclei result from the presence of stellar black holes and supermassive black holes, respectively. The bending of light by gravity can lead to the phenomenon of gravitational lensing, in which multiple images of the same distant astronomical object are visible in the sky. General relativity also predicts the existence of gravitational waves, which have since been observed directly by the physics collaboration LIGO. In addition, general relativity is the basis of current cosmological models of a consistently expanding universe.
Widely acknowledged as a theory of extraordinary beauty, general relativity has often been described as the most beautiful of all existing physical theories.
The question is pretty simple, why would we even want to combine the two big theories to create a unified theory of everything? Is it not better to simply say that the laws of physics behave differently at these scales and that a theory of one doesn't necessarily have to work with another...
hello,
i want to know if there an experience that shows how can we verify the quantum physics that studies everything that is subatomic up to quark ,and thank u again
I am a high school student. I looked up Special relativity and grasped it pretty easily, without needing to learn any new math. But when I tried to read about general relativity, I was immediately confused by all the math, equations and notation. My problem is that I have no idea where to...
I'm currently doing a course on general relativity, and I'm struggling with the following exercise - I would greatly appreciate the help anyone might offer. Whilst not technically homework (not assessed or in a tutorial set) it is from a collection of difficult questions from a recommended...
This is from an older thread:
If that's true, how does the electron's spin cause it to behave like a small bar magnet? Why does relativity demand an electron have a magnetic field?
Thanks!
If I am traveling in a spaceship in a speed close to the speed of light the time will delay right? However I am in space where there is low gravity which means that time will speed up. What will exactly happens to time will it speed up because of low gravity or delay because of the speed...
Hi.
I saw this:
http://physics.stackexchange.com/questions/35431/is-the-law-of-conservation-of-energy-still-valid
Now, if that's the case, then I wonder about a related question: can general relativity be used to create perpetual motion machines? If not, then why not (i.e. how does energy...
In special relativity clocks are used to record events and proper time gives the time in an inertial frame so two times are used. In general relativity I only see proper time being used. Is there an implicit understanding about clocks?
Author: Bernard Schutz
Title: A First Course in General Relativity
Amazon Link: https://www.amazon.com/dp/0521887054/?tag=pfamazon01-20
Prerequisities: Better part of a undergraduate (BS) physics program
Contents: Undergraduate, upper level; Graduate, introductory
Table of Contents...
Is there a list of all the general relativity lecture videos somewhere? Most of the videos I find do not have very good resolution of the black boards.
Homework Statement
Show that Ui \frac{dU^i}{d\tau} = 0
Homework Equations
Raising Indices: Ui = gkiUi = Ui
where gk is a dummy index
The Attempt at a Solution
I'm interpreting this question to mean a scalar multiplying each component of a four vector = 0. Also, since the same...
Hello
(a) The universe U is a topological space whose elements are called events and as each event has a neighborhood homeomorphic to R^4.
(b) A local coordinate system is a homeomorphism between an open subset of U and a bounded subset of R.
(c) A world line segment is a continuous...
Author: Bernard Schutz
Title: A First Course in General Relativity
Amazon Link: https://www.amazon.com/dp/0521887054/?tag=pfamazon01-20
Prerequisities:
Author: Sean M. Carroll
Title: Spacetime and Geometry: An Introduction to General Relativity
Amazon Link: https://www.amazon.com/dp/0805387323/?tag=pfamazon01-20
Download Link: http://ned.ipac.caltech.edu/level5/March01/Carroll3/Carroll_contents.html
Prerequisities:
Contents:
Contents:
1...
Hi all,
I'm having a discussion with someone who believes they understand GR, here is their understanding of how gravity works...
"The time and space at your feet are different from the time and space at your head.
This has been experimentally verified, especially in terms of the time...
can you explain me please the difference between the special and general relativity
i did some research and only what i found and what i understand and i ' m not sure is that te SR is applied only in inertial frame and the GR is applied in the noninertial frame correct me please if i ' m...
I'm in the United States, taking undergraduate courses, and I believe I had what was an introduction to special relativity in Modern Physics class (Lorenz transformations, time dilation, the relativistic doppler effect, time dilation, length contraction, etc.). I just wonder what class general...
I have a broader question on this - is mass at all properly defined in GR context, including rest mass or so-called invariant mass?
Leaving aside concept of mass gain, I have been under the impression that mass itself is defined in different ways in different situations in GR, with caveats...
So this is purely for self-study purposes. Say I'm very keen on understanding GR well, but I don't even have the prerequisites done for even starting to grasp GR. Would anyone be able to give an outline of the skills necessary in understanding GR?
An outline would look something like this...
Hi, I have some questions about general relativity. I'd appreciate if somebody could enlighten me :)
I heard that according to Einstein, objects do not accelerate in a gravitational field, it is just spacetime that is warped around them. So what exactly does this mean? Is it that due to...
Hello everybody, I was watching a documentary about black holes the other day and I noticed something odd.
General Relativity is said to break down when you apply the mathematics on a singularity. In this case, the center of the black hole. The radius of a singularity would be 0. Now there...
I am unable to find any source describing at any lengths transformations of the type
x \rightarrow -x
beyond the case of static spacetime (and even in the case of static spacetime, it is rarely the fundamental definition, which tends to be more along the lign of orthogonality with an...
People seem to be seriously looking for "Lorentz violating" neutrino oscillations - meaning direct violation of special relativity.
What is a short name for the symmetry that distinguishes general relativity from special (the symmetry between acceleration and gravity)?
I think I read once that length does not exist in general relativity, though I'm not sure if I got that hopelessly muddled or if there are subtleties that I am missing. I have a vague understanding of length contraction, but I thought that what I was reading said that there simply is no length...
In f(R) gravity as http://en.wikipedia.org/wiki/F%28R%29_gravity ,
i have problem with the term [ g_ab □ - ∇_a ∇_b ] F(R) , well
actually is [ ∇_b ∇_a - ∇_a ∇_b ] F(R) , but F is a function of Ricci Factor and Ricci Factor is expressed as a(t) ( scale factor ) . for the a = b = 0 i say this...
Homework Statement
The gravitational redshift tends to decrease the frequency of light as it travels upwards a distance h,\frac{\Delta{f}}{f_{0}}=\frac{-gh}{c^2}
integrate both sides of this equation (from the surface of the gravitation body out to infinity) to derive the expression for the...
I would like to know if there are exact solutions using General Relativity to determine: 1) time dilation from velocity, and 2) velocity from redshift (arising from kinematic movement). I understand that Special Relativity can handle both of these questions, but the implementation of SR is...
I know little to nothing about G.R. but it is interesting to look up knowledge,especially physics, so please correct me if I am wrong..
It is easy to picture how one giant mass distorts spacetime on 2D scale, but what if there is multiple bodies of masses present and would this turn into a...
Homework Statement
I have derived the metric in for 2D Rindler space in a previous problem and it is explicitly given again here:
ds^2 = dx^2 - (dx^0)^2 = dw^2 - (1+gw/c^2)^2(dw^0)^2 ,
where (x^0, x) are Minkowski coordinates in an intertial system I and (w^0,w) the Rindler coordinates of a...
On 2 October, 5 days from now, Derek Wise will give an online international seminar talk which will be a followup to his June 2012 paper with Stefen Gielen---as I recall a lot of us found that paper very interesting and it topped the second quarter MIP poll.
So I want to review that paper, the...
Hi everyone, I was wondering if I could some advice from anyone who has some experience with higher level general relativity. Any help would be greatly appreciated!
Some background:
I'm currently working through Robert Wald's General Relativity and am struggling a lot with the "advanced...
Tides on Earth are described with Newton's theory of gravitation. Relativistic effects on tides theoretically become measurable on very strong gravitational fields, possibly becoming twice as strong as tides predicted by Newtonian gravity: http://adsabs.harvard.edu/abs/1983ApJ...264..620N...
Hi, I am in my 3rd year and have General Relativity as one of my options.
I'm kind of feeling the peer pressure of selecting General Relativity, but putting all the hype aside, is it really necessary to learn General Relativity for an Experimental Physicist?
I have to say, maths isn't really...
Hi everyone, first of all I have been a lurker here for years and have benefited greatly from many of the discussions in the math and physics sections. Thanks, I have received a lot of helpful information from these forums!
I have been working through Wald's General Relativity book and I am...
Plain old Newtonian mechanics is time-reversal invariant, i.e. if you view a recording of some events played backwards, it would still appear to be following the same physical laws (gravity attraction law in particular). This type of "time reversal" is exactly equivalent to just turning every...
I'm interested in using a fluid analogy of general relativity to more easily visual what is going on in certain situations, without having to resort to visualizing curved 4d space time which is doesn't come to naturally.
However, I don't know relativity quite well enough to understand what...
Hi
You guys probably have heard about the monkey and hunter problem.
Basically in the monkey an hunter problem you can see the dart hits all the time if you observe the experiment in an accelerated frame of reference ie your falling with the monkey. You see the bullet travel in a straight...
I'm looking for a good text on the foundations of GR. Geared towards physicists, but with a focus on the subtleties of the ideas that went into building the theory rather than on applications. Any recommendations? Thanks!
Homework Statement
Essentially, my adviser just told me to get the equation, then expand it so that it doesn't have any tensors. That's it. Just get rid of the tensors.
He said that this would be normally found in some textbook...? I've searched a lot of books, but I never saw anything...
Hey guys
I was just wondering the following. Since time slows down when traveling faster, and we move around 1.3 million miles per hour, using the CMBR as a frame of reference. Does this mean our perceived lightspeed is wrong? How fast would we measure time to travel if we managed to come to...
Homework Statement
Given the metric
ds^2=-e^{2\phi}dt^2+\frac{1}{1-\frac{b(r)}{r}}dr^2
find the time component of the 4-acceleration of an object moving with velocity v in the r direction.The Attempt at a Solution
The four-velocity of the object is u^a=(t', v)
where the prime stands for the...
Hey all!
So, in my study of general relativity, I've come to understand that gravity is actually what physicists would have classically called a "fictitious force", in that it is a force derived from the fact that the observer is not in an inertial reference frame, like in the case of the...
If the Higgs field is responsible for embuing particles with mass, and mass is responsible for gravity, is it possible that the Higgs field will provide the missing link between general relativity and quantum mechanics ie could the Higgs field be the basis of a quantum theory of gravity?
Alcubierre metric:
ds^2 = \left( v_s(t)^2 f(r_s(t))^2 -1 \right) \; dt^2 - 2v_s(t)f(r_s(t)) \; dx \; dt + dx^2 + dy^2 + dz^2
What formal conditions are required to verify a valid metric solution of the Einstein field equations?
How many possible valid metric solutions are there in General...
We know that the proper time between two events is the shortest possible time between those two events that can be measured in any frame. This follows from the idea that moving clocks run slow-- a stationary clock at rest in S' which moves relative to S at a constant speed v will be time dilated...