Einstein Definition and 788 Threads

Why kinetic energy is ½ m v2? Why it is different from Einstein’s equation for Energy E= m c2?

Is it true that the Einstein Field Equations have an infinite number of solutions when the pressure is zero?

If the speed of light would change in the universe without any other natural constant changing, would all clocks be affected in the same way by this? This is implied by Einstein in this paper on page 368 http://myweb.rz.uni-augsburg.de/~eckern/adp/history/einstein-papers/1912_38_355-369.pdf...

Homework Statement The Lagrangian density for the ##h=h^{00}## term of the Einstein gravity tensor can be simplified to: $$L=-\frac{1}{2}h\Box h + (M_p)^ah^2\Box h - (M_p)^b h T$$ The equations of motion following from this Lagrangian looks roughly like (I didn't calculate this, they are given...

At the end of the (fourth), 1905’s E=mc² paper Einstein claimed: “The fact that the energy withdrawn from the body becomes energy of radiation evidently makes no difference”. This sounds odd to me, given that the change L(γ-1) in kinetic energy resulted from calculating radiation energy. Light...

A recently published paper discusses the necessity of applying Einstein’s Equivalence principle to the quantum realm. It’s validity adds mor constraints on how quantum particles may move. https://phys.org/news/2018-08-einstein-equivalence-principle-quantum-world.html

I would be grateful if some one would consider my following thought and indicate to me the likely mistakes, which I cannot do. Following the paper “Why the Riemann Curvature Tensor needs twenty independent components” by David Meldgin UC Davis 2011, I understand that with a coordinates...

Homework Statement I know that by definition Γijkei=∂ej/∂xk implies that Γmjk=em ⋅ ∂ej/∂xk (e are basis vectors, xk is component of basis vector). Can I write it in the following form? Γjjk=ej ⋅ ∂ej/∂xk Why or why not? Homework EquationsThe Attempt at a Solution

Some of the most profound statements on the nature of science have come from Albert Einstein, one of the greatest scientists of all time. What do you think Einsteine meant when he said: "The most incomprehensible thing about the world is that it is comprehensible"?

Does anybody have any references where Einstein speaks about Time Machines? From collected sources I found, he strongly rejected the idea of Time Machine but through his theory implied that time travel may be possible if wormholes existed. Something needs to be infinitely fast to do this? Have...

A star and a black hole again confirm Relativity. https://www.space.com/41291-relativity-revealed-milky-way-core.html

Hello I am doing some exercises in continuum mechanics and it is a little bit confusing. I am given the following equations ## A_{ij}= \delta_{ij} +au_{i}v_{j} ## and ## (A_{ij})^{-1} = \delta_{ij} - \frac{au_{i}v_{j}}{1-au_{k}v_{k}}##. If I want to take the product to verify that they give...

Please let me know if this statement is correct, too vague, or blatantly wrong. I am doing research for an article I am writing, but am not a physicist, nor have I ever taken any physics instruction. If you have suggestions to fix it, please let me know! Thanks! Einstein thought the initial...

Hello I am investigating a thought experiment conducted by Einstein in which he imagines a man on a train platform (it is being explained on a documentary I am watching). Two lightning bolts equidistant from him strike at either side. He sees these bolts of lighting strike at the same time. A...

I am glad that this Summer I was introduced to an awesome novel, The Other Einstein. The book is the fictional portrayal of Mileva Maric, the wife of my favorite scientist Albert Einstein, and her struggles to balance life and work. The author has done a good job in researching the life of...

Hello, I am currently taking a course on general relativity with the book "General Relativity: An introduction for physicists" by M.P. Hobson. I am a having a hard time understanding the derivation presented for the Einstein equations. The book states that Einstein proposed the following...

So the other day I saw a YouTube video on how gravity works according to general relativity. From what I understand, objects bend space_time with their mass and create a shape which is close to a cone. Since objects only move forward in time through a straight line, the bent space_time makes...

Homework Statement I am unsure as to how to write the dot product in terms of the summation notation? May you please explain? Homework EquationsThe Attempt at a Solution

I see this has been already discussed but the old threads are closed. EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited "In this example, Einstein presents a paradox in QM suggesting that QM is inconsistent, while Bohr attempts to save consistency of QM by combining QM with the...

I'm working on a project at university to calculate the magnetocaloric effect of dysprosium. This will be done using a new technique designed at the university of which its not necessary to go into detail about. In short, the Dy is placed in a solenoid, through which a current runs, the current...

The next questions will be in english and spanish, since my birth language is spanish I may be mistaken in a few english words. --------------------------------------------------------------------------------------------------------------------------------------------- Spanish Debo advertir que...

I read that in 1911 Poincare asked Einstein a rather deceptive question. What is the mechanical basis of SR. Einstein replied none, and promtly left, while Poincare was left in shock. I will not say what I think (yet), but was Poincare right to be shocked Einstein dismissed such a question...

I've tried every way google searching to find the actual einstein bohr debates. But it's basically just commentary and summaries on them. I want to actually read the debates word for word, as well as any other dialogue the two had between them that was made public. Does anyone have any sources?

https://www.forbes.com/sites/startswithabang/2018/02/14/black-holes-must-have-singularities-says-einsteins-relativity/amp/

Anyone has the original paper on the Bose-Einstein condensate? Searched on Google without any success.

Hello, everyone! My name is Hannah Taylor and this is my first time contributing to a forum so bear with me while I figure everything out. In the meantime let me share a few facts about myself with all of you.. I was born and raised in a small village called Cowden, we have about 650 people &...

Hi. Thanks for letting me ask this question. It is a stupid one. I'm a newbie at relativity theory, and I'm reading On the electrodynamics of moving bodies, By Einstein, A. He associates time with space, and tells us that you can measure the "time" of an event if you are in the coordinates of...

Hi everyone, I just have some confusion regarding Planck's and Einstein's equation. The following is an explanation of the photoelectric effect using Einsteins theory: Light is composed of photons. Each photon has energy hf and mass hf/c^2. When ultraviolet photons are brought to rest by zinc...

What do I have to do if I want the EFE's to approximate a weak gravitational field, where for example, an inversely proportional to the cube ( ##1 / r^3## ) of the distance law between the masses applies?

Homework Statement I'm having some trouble with this problem as it seems my concept of the problem is completely wrong. Could someone look through my solutions and point out what I understood wrongly? Thanks in advance. Homework EquationsThe Attempt at a Solution a) 21 macrostates - this...

I continue to see references to time dilation that I don’t understand. Maybe the bluntest one is in a textbook by Resnick. Introduction to Special Relativity, p. 93: “Indeed we find that the phenomena are reciprocal. That is, just as A’s clock seems to B to run slow, so does B’s clock seem to...

The Einstein equivalence principle (EEP) states that “The outcome of any local non-gravitational experiment in a freely falling laboratory is independent of the velocity of the laboratory and its position in spacetime.” I’m trying to make sure I’ve understood this correctly. I’m I correct to...

Testing Quantum Gravity Johan Hansson, Stephane Francois (Submitted on 19 Oct 2017) The search for a theory of quantum gravity is the most fundamental problem in all of theoretical physics, but there are as yet no experimental results at all to guide this endeavor. What seems to be needed is a...

Actually from the Einstein field equation I am trying to compute the R00 component and get at a point R00=k(.5Tg00-T00) where,T=gαβTαβ now I am trying to apply the weak field approximation ,how will I proceed?

My question is why is the lagrangian density term in the action is equal to ricci scaler for gravitational field

I know that according to Einstein's theory of relativity, space-time is like a fabric which can be pliable. Gravity is the shape, or the warping of that fabric. In this analogy, what would dark energy (the unknown form of energy that is causing the universe to expand) be?

Did the 2017 eclipse prove Einstein was right or the jury is still out? I can't find any references to the new measurements and what they proved (or did not).

My son is taking a chemistry class in high school, and he was telling me this morning that their teacher had taught them there was some kind of fundamental distinction between scientific laws and theories. He said the teacher had told them that laws are just fundamental regularities observed in...

So, I'm going to learn general relativity but I'm confused in which book I start with Bernard Schutz book seems excellent but I'm more interested in d'Inverno book, And Misner/Throne Book Seems complete but its giant and good for reference, So I think I will go with d'Inverno , but first I need...

Pardon me if this has been asked before, but I'm confused with the implication that SR makes, that there is no objective moment of present. Do the science still believe that the time flows (i don't mean the arrow of time, but the phenomena of flowing/passing, eq. flowing of a river)? I mean, how...

Homework Statement The question asks us to write down the matrix represented by the following summation. 2. Homework Equations The question summation... $$\sum_{j,k=1}^{3} a_{ij}b_{jk}x_{k}$$ The Attempt at a Solution $$ \sum_{j,k=1}^{3} a_{ij}b_{jk}x_{k} =...

I'm an engineer who has an amateur interest in physics. I have been reading about Einsteins light clock experiment. I understand the principal that when a light clock on a train etc is moving relative to a standing still observer then the light must travel a longer distance per tick. given that...

I saw a documentary the other day where Michio Kaku said something that really peaked my interest. He said that Einstein in his last days was working on something having to do with how small geometries of some sort being the cause of gravity. Does anyone know the details of Einstein's Unified...

Many scientists are regarded as geniuses based on their work (Einstein, Newton, etc). What is it about their work that is so clever that few others could have done it?

This is a just for fun question. I saw the movie "Contact" and they built a machine that generated gravity by spinning rapidly. I assume this comes form general relativity. Is this correct? My question then is this. Is there a simple formula that can be used in which something moving in an orbit...

Dear All, I am doing the Special Relativity course at World Science U, and came across this question which I got wrong: When 100 nanoseconds have elapsed on traveling Gracie's watch, she immediately stops, turns around, and heads back toward George at the same speed of her outbound journey...

Dear All, Just wanted to share this excellent free Special Relativity online course I came across by Brian Greene, which I believe is one of the best around. Not sure if it's been shared before here. Special Relativity — World Science U, by Brian Greene...

Hello! Does ##(x_\mu)^2## actually means ##x_\mu x^\mu## in Einstein notation?

Two spaceships with their engines shut off and identical radio receiver-amplifier-reemitting devices are in the empty space, very far from each other and from any celestial body. The lag time from absorbing to reemitting in the device is vary small compared to the return time of the signal (2t)...

Hello! I'm trying to simulate a one dimensional time independent BEC, I hope this is the right place to ask for help. First of all, here's my code in Python. import sys import numpy as np import matplotlib.pyplot as plt if len(sys.argv) == 1: niter = 100 elif len(sys.argv) == 2: niter...