Relativity

Einstein talks about creating a coordinate system with a lattice of imaginary measuring rods of unit length along the spatial axes. In the real world would such a rod's length have to be measured as a spatio-temporal distance? In practical terms ,if we put a person at the origin of the coordinate system and put such a rod in his/her hand and ask him to actually measure it how could he do this without recourse to a time element in the procedure? If he simply counted all the protons fortuitously along the rod's length the next question seems to be "how do you measure the length of the individual proton without there being a time elem…

Good day, So i got a quick question and maybe someone can help me to understand it. Light travels from Sun to Earth in about 8 minutes. So we can see Sun how it was 8 mins ago... (aprox). So here is the question: Moon does not illuminate by itself as we know. So if im sitting on the Sun and looking at the Moon, should i see it how it was 16 mins ago?.. Thank you. Regards

In special relativity, when a body reachs speeds near the light ones some strange effects could be appreciate by an external observator: Lorentz contraction, time dilatation and increase of mass. But, Is that last one correct? In particle accelerators like LHC the mass of a proton "increases" when it reachs high speeds (99,9% of light speed!), due to the equation which describe its linear momentum ( this reason can be applied also to macroscopic bodies) That could be write P=y*m*v, where y is the gamma Lorentz factor But in reality, the mass of a particle can't change, it is always the same. In fact the relativistic mass is only the multiplication between …

I'm somewhat familiar with GR but not all aspects of it, I do understand how the non-Euclidean nature of the 4D geometry enables us to consolidate gravitation and acceleration and the coordinate transformations, I studied this in some depth (and began with Eddington's space time and gravitation and the fascinating section on Gaussian curvature) but I'm not a mathematician and my knowledge is rather gappy (and nowadays rusty). As for QM I read about that too but nowhere near as much effort was put in and this was all in the late 1970s when I had time to indulge in these. So, having said all that - what is the simplest way to explain the deep incompatibilities bet…

I read up on a hypothetical way to travel faster than light in space, and that is to compress the space in front of the spacecraft while at the same time expanding the space behind the craft. They proposed this through the use of gravity to bend space while shielding the passenger and the interior of the craft from the effects of the gravity. My question is, does this actually make it possible to move faster than light relative to the passenger?

The following is an article and paper I came across. Can a relativist/physicist please explain in simpler detail, if possible? particulalry the following..."There are four distinct rotational relativistic transformations in the literature: the Langevin metric; Post transformation; Franklin transformation; and the absolute Lorentz transformation (ALT) in its rotational form." and how is validates or otherwise relativity. https://phys.org/news/2021-05-optical-reveal-basic-spacetime-rotating.html Researchers use optical data to reveal the basic structure of spacetime in rotating frames: One of the most basic structural aspects of relativistic spacetime i…

Consider a stationary Earth, with one end of a wormhole fixed nearby, and the other end fixed one light year away. The wormhole is a shortcut of negligible length connecting pairs of events, one at (0, t) and one at (1 LY, t). There are two twins, one on Earth and one in a rocket that travels at a relativistic speed relative to Earth (say 0.6 c or choose a convenient number). Who ages more in these 4 scenarios?: 1. The rocket leaves Earth, travels to and enters the far end of the wormhole, and ends up back at Earth, having been inertial the whole time. 2. The rocket leaves Earth through the near end, exits at the far end, and travels back to Earth, inertial the …

Why do we need to imagine it as I thought our concept of geometry was 3 dimensional.. And I need to add this question: Is Time One Dimensional?

The proper time of the Universe (the age of the first space(time)point seems to be absolute. Why do you think it is not? Relativ is the co-ordinate time within Space

An astronaut falls into an extremely large Schwarzschild black hole, so large that they don't notice any spaghettification-like effects. Their head can see their feet the entire time, and their helmet is constantly sending information to Earth, say. At some point, the astronaut sends a message basically saying "My feet are now inside the event horizon", and Earth eventually receives that message. Is there a mistake with this scenario? What prevents the astronaut's head outside the event horizon from seeing their feet inside the horizon, and how does that look to them if they're watching their feet the entire time? I have an answer in mind but I'm curious …

Is motion just the natural order of things and so we are really asking what changes motion? In any system is there a process of seeking a balance and this process is unattainable so motion continues? And why is there a favoured direction of motion (along geodesics)?

Suppose we have two reference frames that are not at rest wrt each other (even accelerating). Is there any way at all that a observers in their respective frames can agree upon a mutual time? Is there any way at all for the to synchronize clocks ,if only for the one instant?

First we consider the fact that the norm-square of the four acceleration vector is negative or zero. Indeed \[c^2=c^2\left(\frac {dt}{d \tau}\right)^2-\left(\frac {dx}{d \tau}\right)^2-\left(\frac {dy}{d \tau}\right)^2-\left(\frac {dz}{d \tau}\right)^2\] (1) Differentiating both sides with respect to time we obtain \[c^2\frac{d^2 t}{dt^2}\frac{dt}{d\tau}-\frac{d^2 x}{dt^2}\frac{dx}{d\tau}-\frac{d^2 y}{dt^2}\frac{dy}{d\tau}-\frac{d^2 z}{dt^2}\frac{dz}{d\tau}=0\] (2) We transform to an inertial frame where the particle is momentarily at rest. \[c^2\frac{d^2 t}{d\tau^2}\frac{dt}{d \tau}=0\] \[\Rightarrow \frac{d^2t}{d \tau^2}=0\](3) [the above holds since …

I am starting this as a split from Mordred's what is space topic as the subject has been broached. Henri Bergson's disagreement with Einstein is nearly one hundred years into the past. HB was observably wrong in at least the twins paradox. However he was right in this His metaphysics made matters worse rather than better in that he introduced two kinds of time ! I had to check with my copy to make sure you were not referring to another philosopher, Professor Berkson, whose book "Fields of Force" offers a rather different view. I don't think that either Bergson or yourself understand what I meant by " without an u…

So I've been running a lot recently. And running causes the mind to wander, and wonder. Here are some wanderings: Are all quantum observers required to be massive? Can something without mass, cause or contribute to waveform collapse of an another observable? Must all massless things in the universe move at the speed of light, relative to the massive things? Must all things that move in the universe at the speed of light be massless? Do all massive things move at the same speed relative to a massless thing? Do all massive things need space? Do any massless things need space? Do all massive things experience entropy? Do …

Link to file on the Google Drive https://drive.google.com/file/d/1C2-ru6uuDIw9u_e4HQ1bdwa01oKysQ-B/view?usp=sharing Material in Latex[It might be necessary to refresh the page for viewing the formulas and the equations] The paper establishes mathematically that the Riemann Tensor is a zero tensor Riemann Curvature |Tensor \[R^{\mu\nu}_{\quad\gamma\delta}=g^{\alpha\mu}g^{\beta\nu}R_{\alpha\beta\gamma\delta}\] (1) Interchanging the dummy indices alpha and beta we have, \[R^{\mu\nu}_{\quad\gamma\delta}=g^{\beta\mu}g^{\alpha\nu}R_{\beta\alpha\gamma\delta}\](2) Therefore, \[g^{\alpha\mu}g^{\beta\nu}R_{\alpha\beta\gamma\delta}=g^{\beta\mu}g^{\alp…

[One my have to refresh the page for viewing the formulas and the equations] We consider the transformation of the rank two contravariant tensor: \[\bar A^{\mu \nu}=\frac{\partial \bar x^{\mu}}{\partial x^\alpha}\frac{\partial \bar x^{\nu}}{\partial x^\beta}A^{\alpha\beta}\](1) Inverse transformation[for non singular transformations] \[A^{\alpha \beta}=\frac{\partial x^\alpha}{\partial \bar x^\mu}\frac{\partial x^{\beta}}{\partial \bar x^\nu}\bar A^{\mu\nu}\](2) For the diagonal components[alpha=beta] \[ A^{\alpha \alpha}=\frac{\partial x^\alpha}{\partial \bar x^\mu}\frac{\partial x^{\alpha}}{\partial \bar x^\nu}\bar A^{\mu\nu}\] (3) We consider …

Four Acceleration vector \begin{equation}\left(c\frac{d^2 t}{d\tau^2},\frac{d^2 x}{d\tau^2},\frac{d^2 y}{d\tau^2}, \frac{d^2 z}{d\tau^2}\right)\end{equation} (1) [[ct]=[x]=[y]=[z]] Let \begin{equation}c^2N=c^2\left(\frac{d^2 t}{d\tau^2}\right)^2-\left(\frac{d^2 x}{d\tau^2}\right)^2-\left(\frac{d^2 y}{d\tau^2}\right)^2-\left( \frac{d^2 z}{d\tau^2}\right)^2\end{equation} (2) We consider the metric \begin{equation}c^2d\tau^2=c^2dt^2-dx2-dy^2-dz^2 \end{equation} (4) \begin{equation}\Rightarrow c^2=c^2\left(\frac{dt}{d\tau}\right)^2-\left(\frac{dx}{d\tau}\right)^2-\left(\frac{dy}{d\tau}\right)^2-\left(\frac{dz}{d\tau}\right)^2\end{equation} (…

Metric: [Signature;(+,-,-,-)] \[c^2 d\tau^2=c^2 g_{00} dt^2-g_{11} dx^2-g_{00} dy^2-g_{00} dz^2\] (1) [In (1) g_00,g_11,g_22 and g_33 are the absolute values of the metric coefficients,the system of coordinates being orthogonal] By our choice let \[cdt=dx=dy=dz\] (2) Dividing both sides of (1) by (cdt)^2 We have \[ \left(\frac {d\tau}{dt}\right)^2=g_{00}-g_{11}-g_{22}-g_{33}\] (3) Since the left side of (3) is positive we have, \[g_{00}\ge g_{11}+g_{22}+g_{33}\](4) Taking Schwarzschild geometry \[1-\frac{2Gm}{c^2r}\ge \left[1-\frac{2Gm}{c^2r}\right]^{-1}+r^2+r^2{\sin}^2\theta\] (5) The above is not true for large r With \[c^2…

This post will be Revised.Pl wait. [it might be necessary to refresh the page or viewing the formulas/equations] In this writing we dive a highly restrictive relation for the metric coefficients in Genera Relativity We start with the the formula \[\sum g^{\alpha\beta}g _{\alpha\beta}=4\] (1) Summation extends over alpha and beta In the orthogonal systems (1) reduces to \[g_{00}g^{00}+ g_{11}g^{11}+ g_{22}g^{22}+ g_{33}g^{33}=4\] (1') Applying the reversed Cauchy Schwarz inequality to (1')we have, \[\left[ g_{00}g^{00}- g_{11}\left(-g^{11}\right)- g_{22}\left(-g^{22}\right)- g_{33}\left(-g^{33}\right)\right]^2\\ \ge\left(g_{00}^2-g_{11}^2-g…

The covariant derivative of a rank one contravariant tensor is a mixed tensor of rank two. Considering its transformation we arrive at a conflicting result[discrepancy] in the enclosed paper.Equation (3) should no be valid for an arbitrary tensor Transformation_Covariant_Derivative.pdf

In physics when we say two events occurred simultaneously at two locations--is that synonymous with saying they coexisted at those two locations? When we say the words “coterminous events”, it is taken for granted that we mean the two events coexist at a particular location and also that they occur simultaneously. However, to a layman like me, the advent of Special Relativity seems to have changed the concurrence between the two in the following way: We can no longer take it for granted that coexisting events that are not coterminous will also be simultaneous, because in Einstein’s original thought experiment (train/embankment) where he outlines his “most natural de…

It is how to understand dark matter when you reach light speed. ...warp speed is shown with no weight when you reach the speed limit

It is a no contest to the acceptance that Albert Einstein is the best thinker in physics. Scientists saved his brain for research and found that his cerebral was hard wired abnormally like no other people. That accounts for his weird thinking in the field of physics. He is definitely the best synonymous with genius. He perceived the weird fourth dimension and and the formula to make the atomic bomb that saved the United States from losing the war in World War 2. The U.S. should be thankful on this Thanksgiving day that he did not end up in the Jewish Holocaust. I just encourage the U.S. to never ignore my reverse order mathematics in reference to every physics equati…

We analyze the mathematical mechanism that slows the time of the traveler in the twin paradox and explain what distinguishes the traveler's frame from the Earth's frame Please read the article at https://www.scienceforums.net/applications/core/interface/file/attachment.php?id=18516 PDF: Twin paradox when Earth is the moving frame url removed or Word: https://www.academia.edu/39216040/Twin_paradox_when_Earth_is_the_moving_frame