What is Gr: Definition and 952 Discussions

I hope that some of the folks (Mike, Howard, Patrick, Robin) who have engaged in the other threads [1][2][3] on outcome counting (ie Patrick's APP) see this thread. Starting with the Feynman path integral formulation of ordinary quantum mechanics, it is pretty straightforward to derive...

im stuck on the last question of this lab. "what combination or masses would make the accelration of an atwood machine equal to 1/2 g?" a = g (m1 - m2/m1=m2) so i have to find out what m1 and m2 are eual to in that forumula if g = 1/2 im thinking a is equal to 9.81 because the...

hey again, still looking for projectile motion + circular motion problems (only in horizontal plane). Can anyone please help me make up a question with these two concepts in one. If possible make it a 5 STAR complex question! I am also studying charged particles in a electric field which...

Hello all, Can the method of analytic continuation [1] be applied to the calculation of the metric over a 4-d manifold? In other words, suppose that we are given the value of the metric g_ab as well as its power series at a single point p in a 4-dimensional manifold. Assume further that...

The perihilion of Mercury and the eclipse of 1919 (Eddington expedition) are given as the first experimental verifications of General relativity. However, feeling pedantic, I was curious just which one these is accepted as the vital first prediction of GR in agreement with the real world? If...

I've read in multiple locations that GR is necessary to properly explain a co-rotating perspective/observer of the experiment. Additionally, SR can explain the experience of non-inertial observer. The above two statements seem somewhat conflicting and leads to my question. Why is it that...

In black hole physics and GR, what does the term back reaction means?

When a canon shoots a ball straight up (one dimension), the ball only accelerates as long as the nongravitational force of the canon acts on it. After that, the ball decelerates in the gravity field until the point it turns back and accelerates in the opposite direction as it falls back on...

Does time-like curvature of spacetime cause light to bend, for example, around the sun? Or is the gravitational bending of light only due to the space-like curvature? So far, I understand the concepts as: Time-like curvature is caused by the mc^2 part of E, while space-like curvature is caused...

I am curious as to just when time dilation plays a part as an effect of GR. I am told that clocks tick slower in a gravitational field. Is this an accurate portrayal, or would it be more accurate to say that time ticks slower in all accelerating reference frames? That is, does GR time dilation...

In the past I've spoken about mass a kagillion times. There was one aspect that I had to hold off on until I taught myself the details and meaning to a good level of understanding. I've now come to that level and have made another web page to describe it. The aspect I'm speaking of is "active...

Hey folks, working problems in Hartle's GR book and having trouble with this one. Chapter 9 discusses the simplest physically relavent curved geometry, that of Mr. Swarzschild ds^s = -(1 - \frac{2 G M}{r}) dt^2 + (1 - \frac{2 M}{r})^{-1} dr^2 +r^2(d\theta^2 + sin^2\theta d\phi^2) In this...

Help Exam Tmr! 112 Physics *FORCES* As you may have guessed from the title, I'm in a bit of a bind here. You see the website with the answers to the review questions I'm working on isn't working... and there's an exam tomorrow. Here's a few of the questions any help would be greatly...

This is an analysis involving general relativity (GR). Let a spherically symmetric, uncharged, nonrotating star (not a black hole—that comes later) have an escape velocity = infinitesimally less than c at its surface. Then its r-coordinate radius (also known as the reduced circumference and...

So, who's going to this thing? http://insti.physics.sunysb.edu/itp/conf/GR2005/ Zz.

You might be interested in the contest that ran at the SLAC Summer Institute this year that asked: "What will be the first evidence to demonstrate that Einstein's theory of General Relativity (GR) must be revised, and when will that be found?" The...

I am studying general relativity now and I want to collect some pastpaper about general relativity. Could you mind share yours with me? :blushing: yukyuk

Hi, As I understand things we exist on the 'surface' of a 3 sphere of radius R in the context of general relativity. The popular analogy is that our 3D space can be visualized as the surface of an expanding balloon I would like to ask if anything 'exists' on the interior/exterior of the...

Hi, I am interested in what I can DO with the stress energy tensor once I've obtained it from a metric. I am not so interested in the formal development, just a book or paper that shows what its good for. I am interested in cosmology, specifically: brane worlds, brane gas cosmology...

Can someone help me understand something on page 220 of the book 'A First Course in General Relativity' by Bernard Schutz? Near the middle of the page, the line element is given as ds^2 = -dudv + f^2(u)dx^2 + h^2(u)dy^2 (I changed g to h so I can talk about the metric tensor) which I...

Well there are actually two questions i need some help with, if you could provide a full solution so i cna see the step by stpe thing it would be nice. Question 1 A quadratic function f(x) with integral coefficients has the following properties: f(3/2) = 0, (x-2) is a factor of f(x), and...

Hello, I stumbled upon this work some time ago. It is based on the k-calculus and claims to be a viable alternative to GR. It seems to me to be a whole load of arm waving and even exagerated claims. I am no expert on this though and so would like some more knowledgeable opinions on whether...

could dark matter simply be an error in general relativity or the effect of temporal effects on orbits, ie time is slower the nearer the sun, so the Earth rotates slower on the sun side, and so is pivotted towards the sun(or does this explain gravity only, or maybe the reason objects don't slow...

During many time i have searched a complete and rigorous derivation of Newtonian limit from GR but i found none. I suspect that it does not exist! I do not refer to that "supposed derivation" that appears in many textbooks of GR. I refer to a rigorous and unambigous derivation of Newtonian...

Where can I found an expressionfor the shear stress tensor in GR with some explanation about it? Thanks blue

I thought some here might enjoy a more pedestrian discussion of issues involved in unifying quantum theory with general relativity. I know I do. I need an occassional refresher course to get a grip on the brain bending stuff I usually read: The Problem of Time...

How do you calculate the speed of gravity using general relativity?

Alright, so Einstein came up with SR to make Maxwell's EM consistent with dynamics, correct? But SR was only for non-inertial reference frames and ignored gravity, so it was replaced with GR to make SR consistent with gravity. So why have I read (from many sources) that Einstein spent his...

The new paper is titled General Relativity Resolves Galactic Rotation Without Exotic Dark Matter It is on the arxiv at http://www.arxiv.org/abs/astro-ph/0507619 From the abstract

Ok, this is a really stupid question but it is something that is really confusing me. I am confused on the concepts of dimensions, for example of a sphere and how they relate to Euclidean geometry. A sphere in 2 dimensions using Euclidean 3 dimensional geometry doesn't really make too much sense...

excuse all the questions, but I've just recently started reading about quantum mechanics and want to know about what quantum physicists currently believe about GR.. How sure are physicists that a graviton exists? Is there such a thing as curved space-time in quantum mechanics, and if so is...

If the curve described by an object passing near a star is not due to a 'force of gravity', but to the space being curved by the star's mass, and the object is just following a 'straight' (geodesic) inertial path... then why would a still, not moving object begin to fall toward the star, if...

I want to understand why pressure creates gravity under GR (not how, why). What kind of pressure are we talking about here? Is this just the potential energy of pressure acting as mass? And the second part: I've been trying to model gravity as refraction of masses moving with constant...

A quick question for those fast with the GR and SR math. Assume you get in a spaceship and start accelerating away from Earth, and during the trip you and the people left behind compare clock speeds periodically (not elapsed time, but rather tick rates). At what combination of acceleration...

When we approach a calculation in relativity, do we have to change the cosmological constant in order to work with bigger dimensions? Because i know we are limited to seeing 1, 2 and 3 dimensions, i was just curious if you wanted to figure out an answer using an equation based on a bigger...

Some time ago I began my research in gravitation. Now I am actively working in GR and quantum gravity. I am sorry to say this but when I more study it, more I think that GR is not correct after all. For some criticism to GR, you can see the last part of my "paper" on string theory sited in...

I've just found that article about noncommutative model unifying GR & QM. http://arxiv.org/abs/gr-qc/0504014 A few quotes: Noncommutative geometry plays an increasingly important role in the present search for quantum gravity. It has also recently been recognized that it is a useful...

I know a bit about evidence supporting special relativity (muon decay, synchronized cesium clocks, etc.) and general relativity (perihelion of Mercury, etc.). BUT - is SR and GR considered "proven" or, in the minds of mainstream physicists, is the jury still out?

Hello, I was wondering if any of you can suggest some good introductory textbooks on GR around the graduate level. Thank you for your time. Yours Truly, TK.

Time travel can occur in general relativistic models in which one has closed time-like curves (CTC's). A time like curve is simply a space-time trajectory such that the speed of light is never equalled or exceeded along this trajectory. Time-like curves thus represent the possible trajectories...

I’m interested in how the rate of time compares in different locations of “deep” gravity fields. With GR we are good with the idea that a clock on the Moon runs faster than a clock on Earth. Here we’re looking only at GR the effects of acceleration/gravity. We can directly measure the...

Is it true that nothing physical can move in space-time? As a layman in GR i really wondered whether anything physical can move in space-time because movement in space-time is self-referential and will contradict the basic definition of space and time. Also check out this...

A GR? Does Acceleration or Gravity affect the force of electric charges? Example: Material is forming a Black Hole Heat is creating a ‘Cosmic Wind’ – that is blowing less dense matter away while denser matter is being favored for forming and enlarging the Black Hole. And material is made...

I do a little project about photon at the event horizon. I use GR to proved that anything in the event horizon can't escape from black hole, but a Prof. say that I must use string theory.But I did't accept with him.So, if someone know about it.Please Help me :cry: . (I have to tell you that...

It is my view that the road to a unified quantum theory of gravity and electromagnetism begins with unifying GR and E&M classically (i.e. a non quantum mechanical formulation). They show so may similarities that they may be more closely related than we think.

Where could i find the Hamitlon equation for General relativity to be derived in a simple way?..thanks.

I know there have been some frame dragging effect experiments, with the GPB being performed at the moment. Which other experiments are planned/ or have been performed that may show strong evidence for the theory of GR? any experiments at all will be appreciated...whether they show evidence...

The terms elliptic, hyperbolic and euclidean geometry are defined according to the sectional curvature, which is a generalization of the Gaussian curvature of a surface. Are there any restrictions on the sectional curvature for spacetimes in general relativity? The Ricci scalar, being a...

I posted one quantum theory about this paper: http://www.arxiv.org/abs/quant-ph/0501034 Chen uses a double Kalusza-Klein mod to GR with the two extra dimensions being timelike. He claims this introduces QM into the modified GR, so he has interacting QM and gravity, then he claims to support...

I am a student who is studying General Relativity, and I don't know enough tensor analysis to answer the following straightfoward question: Since the stress energy tensor is just a sophisticated representation of mass, and since einstiens field equations equate this energy to a representation...