Einstein Definition and 788 Threads

Hey guys. I am 17 years old and I love physic. Recently I started to study about special/general theory of relativity. That what I love is the future of light. As eveyone knows light has a speed of "299.000 km/s",and his speed can not cumulated with other speed,so can not become bigger. My...

I’ve been trying to get my brain around Einstein’s theory of special relativity, and I find I'm a bit perplexed about his thought experiment (TE) involving the speeding train and the two simultaneous lightning strikes. To briefly summarize, observer M is standing on a stationary “embankment”...

Hello.The Einstein has following definition (in my course): Gμε = Rμε - 1/2Rgμε. But why don't we just: gμεGμε = gμεRμε - 1/2Rgμεgμε. <=> G = R- 1/2 . R . 4 = R- 2R = -R? Is this wrong or.? Also, what is the meaning of the ricci scalair and tensor?

If time is constantly moving the direction of increasing entropy and quantum systems are time symetric then how do macropscopic entanlged systems such as bose-einstein condensates relate temporally to themselves and larger systems of which they might be subsets? Because BECs are large enough to...

Who first studied variable speed of light? --- Einstein Variable speed of light is a hypothesis that states that the speed of light, usually denoted by c, may be a function of space and time. Einstein's first mentioned a variable speed of light in 1907, and he reconsidered the idea more...

Dear all, I encounter the following formula (for stain energy function) a lot in physics literature: W(\epsilon_{kl}) = \int_0^{\epsilon_{kl}} \sigma_{ij} \textrm{d}\epsilon_{ij} where all indices ranges from 1 to 3, both \epsilon and \sigma are 3x3 matrices. My question is what...

So, I'm a big fan of this t-shirt... http://www.redbubble.com/people/chuckirina/works/10042759-live-for-today?body_color=black&p=t-shirt&print_location=front&ref=shop_grid&style=mens However, I don't feel anyone should have to pay $30+ (after shipping) for a t-shirt. I've tried making pretty...

Homework Statement I'm confused about writing down the equation: \Lambda \eta \Lambda^{-1} = \eta in the Einstein convention. Homework Equations The answer is: \eta_{\mu\nu}\Lambda^{\mu}{}_{\rho}\Lambda^{\nu}{}_{\sigma} = \eta_{\rho\sigma} However it's strange because there seems...

I just read the thread entitled: "How did Einstein Define Time" and I'm very confused. At school, I was taught that time was an abstract representation of movement meaning that the word "time" can only be used to represent movements. For example, when Earth has completed a cycle around the...

I read that the number of Einstein equations is 10 and because of Bianchi identity, it reduces to 6. This is true because we have totally 16 components, but they are symmetric, so there are 10 independent components. However in four dimensional space-time, the number of second order partial...

I'm not a great scientist or math guru, I was in the naval nuclear power program and only pursue physics as a hobby. My question is this: according to Einstein gravity results from the curvature of space. If that is so wouldn't it be reasonable to say that gravity is an effect resulting from...

I can do this derivation the old fashioned way, but am having trouble doing it with einstein summation notation. Since \vec{B}=\nabla \times \vec{a} \vec{B}=\mu_{0}/4\pi (\nabla \times (m \times r)r^{-3})) 4\pi \vec{B}/\mu_{0}=\epsilon_{ijk} \nabla_{j}(\epsilon_{klm} m_{l} r_{m} r^{-3})...

This question is on the construction of the Einstein Field Equation. In my notes, it is said that >The most general form of the Ricci tensor R_{ab} is R_{ab}=AT_{ab}+Bg_{ab}+CRg_{ab} where R is the Ricci scalar. Why is this the most general form (involving up to the second derivative...

I wonder if Einstein equation E=mc^2 was used when the A bombes were designed and tested. How was the output estimated? Was all the matter thransformed into energy, as the equation indicates? Were there any restrictions to how this equation ( or nny other) was used? Thanks, Michael

Hi. For a Bose gas, my textbook states that below the critical temperature, which is given by n(λth)3/(2S+1)=2.612, the fugacity z=eβμ≈1. Why is this? The most basic explanation possible would be ideal, as I only need the rough idea. Thanks! :smile:

According to GR gravity is not a force so what is gravity according to GR? And according to Newton gravity is a force. Who's right and why?

in the special theory of relativity. nothing can move faster than photon but in netwon, if mass changed it effect right away though how far the two mass how can i understand??

End of chapter 28. "The great power possessed by the general principle of relativity lies in the comprehensive limitation which is imposed on the laws of nature..."

E=MC^2/ ∆T E ----- (Watt) M ------- (kg) c -------- (3* 108 m/s2) ∆T ------ (second) Physical meaning:- The energy take time to convert into mass and mass take time to convert into energy So the universe mass must increase every second Because of the initial...

Hi i have been following Hobson in their attempt to derive the einstein tensor, I have split the varied action into three terms and want to factor out \delta(g^{\mu\nu}) terms. The Riemann tensor R_{\mu \nu} must be expanded to R^{\rho}_{\mu \nu p} and then contracted back to the original...

prove the identity $$\nabla\times(f\cdot\vec{v})=(\nabla f) \times \vec{v} + f \cdot \nabla \times \vec{v}$$ I can do the proof with normal vector calculus, but I am in a tensor intensive course and would like to do this with einstein summation notation, but am having some trouble since I am...

do physics professors still misunderstand Einstein?? i registered at this site just to ask this question: why do physics professors still talk about gravity in terms of "pulling"?? i download podcasts of physics courses at Yale, Berkeley, etc... yet i always hear these guys say things like...

Hi! I would like to ask where the factor of 8π comes from in the Einstein Equations. I understand that it is augmented in order to comply with the Newtonian limit. But why did Einstein decide to place 8π and not for example 8.1π or 3π-3π/e=8.27 or whatever around this value (which would give...

Homework Statement We have the Einstein tensor G_{αβ} = R_{αβ} - \frac{1}{2}g_{αβ}R where R_{\alpha \beta}, R are the Ricci tensor and scalar. Homework Equations We want the metric to be small perturbation of the flat space, so g_{\alpha \beta} = \eta_{\alpha \beta} + h_{\alpha...

The most common definition of mass, at least in the Newtonian context, is in terms of a measure of inertia: The mass of an object is a measure of, and gives rise to, its resistance to changes in motion. F=MA presumably quantifies this idea of inertial mass. I'm wondering whether any...

Hey! How to transform the equation \bigtriangleup\vec E=\operatorname{div}(\operatorname{grad}(\vec E))=\epsilon_0\cdot\mu_0\cdot\frac{\partial^2\vec E}{\partial t^2} in Einstein Notation? Thank you all for your help!

A major part of the takeaway buzz in the popular press—and by a lot of authorities quoted it seemed—was that the Higgs boson/mechanism explained mass (and inertia). I was quite impressed by this fundamental mystery being solved and mentioned it to a prof and he said did not: mass and inertia...

Homework Statement Questions 11 and 12 specifically.. Homework Equations The Attempt at a Solution 11(a) 11(b) 12(a) 12(b) 12(c) 12(d) (I did the last part of 12(d) by normal vector methods and got 2a instead...which is the correct answer)

Hello Some authors claim that Einstein's second postulate (constant speed of light) simply emerges from the first one (or more precisely, its converse contradicts the first postulate). Serway Modern Physics: Now, is that true? And if yes, what's so special about light than other object (ex...

Homework Statement Find the Einstein luminosity (LE) in terms of just c and G (the speed of light and the gravitational constant), i.e. determine a power (in watts) from just these two terms using dimensional analysis. What is this value? Once determined, you should be able to show that an...

Was Einstein aware of the implications of relativity (such as length contraction) before he concocted it? Or were these implied concepts just happy accidents?

There are many threads about this on this forum: People are confused about the basic idea of Gravitation in General Relativity. They understandably don't understand how the very common balls-on-rubber-sheet-analogy explains anything. I usually post those two links to help them...

I am researching a hypothesis and looking for anyone who is familiar with differential topology (specifically Einstein manifolds). I have access to the Besse book Einstein Manifolds but am also looking for any open questions in differential topology that I am not aware of. I am attempting to...

Homework Statement Consider two Einstein solid A and B with N_{A} = 200 and N_{B} = 100. Suppose now that the oscillations of solids A and B are different. The energies of oscillators in solid A are measured in units of ε_{A}, so that the energy of solid A is U_{A} = q_{A} ε_{A}. Likewise...

So basically I have always wondered what motivated Einstein to move from Special Relativity to General Relativity. Anyone care to tell me what was going on in Einsteins mind after he completed his Special Theory of Relativity? I have done a course in Special Relativity, understand it and I...

I'm reading Spacetime and Geometry: An Introduction to General Relativity by Sean M. Carrol and in the chapter on gravitation, he derives the Einstein Field Equations. Here is the part I don't get. He starts with the equation R_{\mu\nu}-\frac{1}{2} Rg_{\mu\nu}=\kappa T_{\mu\nu} Wher R_{\mu\nu}...

Sorry guys, but this was the logical follow up of my previous thread. Your mission, if you choose to take it, is the following: who better "revolutionized" physics, Einstein or Newton? For now we will leave the question this simply, I may push for more clarifications later. Give your reasons.

I watched a video of Michio Kaku saying that according the Einstein's equations of black holes, physics literally breaks down into nothing. I just wanted to ask how accurate the things he says are. For example he states that the mass of the black hole being M and R describes the distance from...

Hello there I love physics, so I normally read a lot of physics books. I am fascinated about BECs and their possible applications. I've read about BECs and BEC vacuum theory, also that is possible to create black holes in superfluids (as BEC) using sound (sonic black holes). As far as I know...

Homework Statement Write out c_{j}x_{j}+c_{k}y_{k} in full, for n=4. Homework Equations The Attempt at a Solution So I figure we have to sum over both j and k. So the answer I obtained is: (c_1x_1+c_1y_1)+(c_1x_1+c_2y_2)+(c_1x_1+c_3y_3)+(c_1x_1+c_4y_4)+...

I'm trying to understand exactly why Einstein considered Maxwell's electrodynamics to be non-relativistic. As I read Maxwell's paper, it seems to me that it is concerned only with relative motions. I'm thinking that the problem must be with the stationary ether proposed by Lorentz, for then...

Could someone explain to me what specifically distinguishes Einsteins more advanced treatment of gravity over Newtons? Here’s what I (think I) know. Newton described gravity as a “force” of attraction between two bodies or masses. That force was given by the G constant times the two masses...

http://www.stuff.co.nz/science/8101704/Einstein-Medal-for-NZ-professor

Hello, I was hoping someone might be able to give a approachable explination of the Gross-Pitaevskii equation. All the sources I've been able to find seem to concentrate on the derivation, and I don't have the physics background to follow. From what I understand, however, is that the GP...

They say ZPE is the energy of the system at 0 K due to vibrations and even though the Schroedinger equation gives us the ground state minimum energy of the system (lets say by DFT/HF/QMC whatever), this energy is a little higher than that. My first question is, because I have learned that...

I can fairly well grasp the trace relationship between the Einstein tensor and the Ricci tensor, and see that Ricci tensor is a multiple of the metric. If the cosmological constant is included I don't get why the Einstein tensor shouldn't become a multiple of the metric (leaving out physical...

Hi, I am using Hartle to study GR and at one point, there is a leap that I don't understand. He finds the result for the geodesic deviation equation and introduces the Riemann curvature tensor. Then, we are told that there is an object called the Ricci curvature tensor which is a...

During one of the Einstein-Bohr debates, Einstein proposed a thought experiment that would prove that one could measure time and energy simultaneously. It's known as the Einstein box: http://en.wikipedia.org/wiki/Bohr%E2%80%93Einstein_debates#Einstein.27s_second_criticism Then Bohr came up...

Sorry if I am asking a too trivial question! I am having a confusion regarding the following-The solution to Einstein equation in vacuum is given by the Schwarzschild metric. However, what does the mass represent in the metric in Schwarzschild coordinate? Whose mass is it and how does it enter...

Hello, Please excuse me if the following questions are very mundane: (1) The Einstein tensor in indices form: Guv=Ruv-1/2guvR Does uv means the indices i.e. just as we define row column in a matrix.? (2) The Einstein tensor is symmetric. Does that mean in matrix as we mean aij=aji...