The special theory of relativity describes the motion and dynamics of objects moving at significant fractions of the speed of light.

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Relativistic transformation of electrical current [closed]

If, in frame $S$, we have an electrically neutral wire with some current $I$, modelled as positive charges moving in $x$ direction and negative charges moving in $-x$ direction, then how would one ...
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Dirac Equation in RQM (as opposed to QFT) is written in which representation?

In introductory Quantum Mechanics treatments it is common to see the Schrödinger's equation being written, simply as: $$-\dfrac{\hbar^2}{2m}\nabla^2\Psi(\mathbf{r},t)+V(\mathbf{r})\Psi(\mathbf{r},t)=...
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Help understanding Bell's spaceship paradox

The problem statement of Bell's Spaceship paradox is this: Two spaceships float in space and are at rest relative to each other. They are connected by a string. The string is strong, but it ...
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1answer
41 views

Reference for Reichenbach synchronisation and non-standard special relativity

My professor introduced in the last lesson a new method for clock synchronisation, which he called "Reichenbach synchronisation". In this new method, two clock A and B synchronise themself with the ...
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Parallel axes between inertial frames in Special Relativity

In "CLASSICAL ELECTRODYNAMICS" by J.D.Jackson, 3rd Edition , $\S$ 11.3, the author gives in equation (11.19) a generalization of Lorentz transformation as follows : If the axes in K and K' remain ...
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What spacelike, timelike and lightlike really mean?

Suppose we have two events $(x_1,y_1,z_1,t_1)$ and $(x_2,y_2,z_2,t_2)$, then we can define $$\Delta s^2 = -(c\Delta t)^2 + \Delta x^2 + \Delta y^2 + \Delta z^2$$ which is called the spacetime ...
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After proving that the photon remains stationary in the fourth dimension, must we conclude that the fourth dimension is moving at c? [closed]

Firstoff, in his general relativity Einstein showed that dimensions could bend, curve, and move. This is an experimentally proven fact. Dimensions can, and do, move. In an earlier post we ...
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1answer
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How do photons experience time? [duplicate]

I know that as velocity approaches the speed of light the time dilation shoots to infinity as shown below. 1)So I want to know how time is perceived from the point of view of the photon? 2)Since ...
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How does a photon experience space and time?

To an an external observer it appears that time has stopped for photon. But this relation is reflexive, so for an observer travelling with the photon it appears the universe has stopped everywhere. ...
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Does photon experience time? [duplicate]

According to the special theory of relativity, for all observers the speed of light is c. Any observer travelling at the speed of light c does not experience time. Hence even protons shouldn't ...
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1answer
264 views

Are we traveling through time at the speed of light? [duplicate]

In the image below the y axis represents time and x represent velocity. Point D represents velocity c, point E represents 1 second per stationary observers second. What this chart is showing is as you ...
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Calculating speed in four dimensions [closed]

If you are moving at $c$ in 3D space and $c$ in time axis too, What would be your total speed? Edit: Since question has been voted to be closed, I shall make an Edit. In 4D world all objects move ...
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How to derive addition of velocities without the Lorentz transformation?

Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of addition of velocities $$w~=~\dfrac{u+v}{1+uv/c^2}$$ without Lorentz ...
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7answers
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Why are the electric force and magnetic force classified as electromagnetism?

I confuse the four kinds of fundamental interactions, so I think the electric force and magnetic force should not be classified as a big class called electromagnetism. Here is my evidence: The ...
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2answers
384 views

What does $v=c$ in the Lorentz transformation for time tell us?

For the simpler cases as boost in the x-direction, the time dilation formula following the Lorentz transformation for time is $$\Delta t'=\gamma(\Delta t-v\frac{\Delta x}{c^2})$$Now, we observe that ...
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1answer
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According to Einstein & Brian Greene, does the photon remain stationary in the fourth dimension? [duplicate]

According to Einstein and Brian Greene, does it logically follow that the photon remains stationary in the fourth dimension? In An Elegant Universe, Brian Greene writes: “Einstein found that ...
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1answer
43 views

Proper time of world lines in twin paradox

I was thinking about the twin paradox in Special Relativity and I thought I understood it fine, but when I view the "paradox" in a certain way, I get confused. So we have two twins, John and Jim. Let ...
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Is time an observable in Relativistic Quantum Mechanics?

Relativistic Quantum Mechanic is based, as far as I know, in the Dirac Equation. Now, the Schrödinger equation, in the abstract state space takes the form: $$i\hbar \dfrac{d|\psi(t)\rangle}{dt}=H|\...
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The path that a light beam takes in empty space

First excuse me if this question is very simple for you but for me and for my friend is not. Recently we were discussing what path a light beam will follow in a box moving at a constant velocity in ...
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1answer
45 views

Yukawa Potential in non-relativistic limit

In Peskin's book "An Introduction to Quantum Field Theory", on page 121 (section 4.7) , it tries to recover the Yukawa Potential in the nonrelativistic limit, but there's a simplification that I don't ...
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Local Phase Transformation of the Dirac equation

The Dirac Equation ("free Dirac") is a relativistic Equation of Motion (EoM) for a free ($V=0$) Spin $1/2$ particle (like an electron). The free Dirac equation is invariant under global phase ...
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Working out Length Contraction

I'm having trouble reconciling the quantitative and conceptual aspects of length contraction. This example is taken out of a book: Say a particle is moving toward us at 0.99c, relative to us. If at ...
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How does EM radiation depend on the reference frame?

In special relativity, magnetism is electrostatics in a different reference frame. This is how we explain the magnetic field being produced by moving charges (aka currents). Charges that move produce ...
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Physical reasons for metric definition in special relativity [duplicate]

I am working through "General Relativity" by Wald, and am currently going through the brief section on Special Relativity. The spacetime metric is defined as $\eta_{ab} = \sum\limits_{\mu, \nu=0}^3 \...
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Derivation of force law in special relativity

I've seen force defined in special relativity as the rate of change of 4-momentum $$ {\bf{F}} = \frac{d {\bf{p}}}{dt} $$ Can anyone comment on the following derivation of that relation? Take one ...
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Two particles of different velocities travel through a region of time-dependant acceleration. At what time do they meet afterwards? [closed]

Two projectiles: $P_{1}$ and $P_{2}$ have velocities $v_{1}$ and $v_{2}$, both propagting in the x direction and starting at $x=0$. They propagate with constant velocity over a distance $L$ and reach ...
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How do simple two-component Fierz identities follow from a property of the Pauli matrices?

On page 51 Peskin and Schroeder are beginning to derive basic Fierz interchange relations using two-component right-handed spinors. They start by stating the trivial (but tedious) Pauli sigma identity ...
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Rest mass of phonon: is this concept definable?

Phonons are obtaied by non-relativistic quantization of the lattice vibration. The dispersion relation is given by $\omega=c_s k$ where $c_s$ is the velocity of sound. What can we say about the mass ...
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Trouble understanding spacetime and invariant interval

First, how is the invariant interval useful? How can it help us understand things around us in the universe? Second, I know that they changed time into space or better say SPACETIME in order to ...
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3answers
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$F=ma$ can only be used if the relativistic mass of the object is known, true?

I have received this question "Einstein's ideas on mass mean in essence the equation $F=ma$ can only be used if the relativistic mass of the object is known. Describe in your own words to what ...
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“Constant Fermion”

I was talking to a professor in my institution which works in Lorentz Violation of various QF theories. While we talk about a SUSY lagrangian, I asked him if we could have a fermion acquiring VEV and ...
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Question about time dilation for a traveler that can reach the “edge” of the universe

I thought I understood time dilations but I feel now confused. Imagine somebody traveling in a rocket near the speed of light, close enough so that he will be able to reach the edge of the universe in ...
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Tensor notation of Maxwell's equations

Tensor notation of Maxwell's equation read So when we explicitly try to find the Maxwell's equation from the above tensor equation we only get gauss law and curl of B. The div.B=0 and curl of E are ...
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How to show invariance using the Maxwell tensor?

I want to show the invariance of $E^2-c^2B^2$ under the Lorentz transformations. The obvious way to do this is to show that $$E^2-c^2B^2=E'^2-c^2B'^2,$$ where $E'$ and $B'$ are the Lorentz ...
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Colliding beams vs static target

In this problem I need to find the threshold energy of a positron-electron collision that creates a Z boson (the reverse of the following picture; Z mass 92 GeV) in two distinct cases: collision ring ...
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Is proper time a vector?

Proper time is identical with the spacetime interval of a timelike movement. A spacetime interval is the dot product of two vectors and thus a scalar. Proper time however is always pointing exactly ...
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Special Relativity and its relation to refractive index [duplicate]

As is known, light slows down (compared to vacuum) whenever it enters a medium. Also, Special Relativity effectively puts a limit on the max. speed of any body. So is it possible for a body (in a ...
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Are all diffusion-like processes described as wave-like in relativity-compatible formulations?

Citing from Wikipedia's article on relativistic heat conduction: For most of the last century, it was recognized that Fourier equation (and its more general Fick's law of diffusion) is in ...
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1answer
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Speed of a particle approaching that of light relative to itself

There's a particle moving at a certain speed $v$ with respect to a reference frame $A$ through an axis I will call $x$. We thus know that for the frame of reference located at the particle itself, the ...
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2answers
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Rotation matrix for aligning x-axis in an arbitrary direction

I want to align the x-axis of my coordinate system, with an arbitrary direction in space $\hat{n}$. About which axis should I rotate? Ceratinty rotation about x-axis or $\hat{n}$-axis will not serve ...
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In relativity, perpendicular motion does not show contraction… Isn't the whole concept lost?

I read in HC Verma's Concept of Physics that a body moving in direction perpendicular to length, doesn't show Length Contraction. And Length Contraction, they said, is to maintain the velocity of ...
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1answer
352 views

Application of special relativity on sound waves

What is the difference between an electromagnetic wave and other waves that amounts to the EM wave following the Special Relativity. I have been reading about the Special Relativity for some time, and ...
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41 views

Intuitive picture for Mandelstam $t$

In tree-level electron-positron scattering one has two possible channels corresponding to Mandelstam variables $s$ and $t$. The $s$-channel ist fine, there $\sqrt s$ is just the center of mass energy ...
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Rotating magnet and magnetic field intensity change?

if magnetic disc is rotating on it's axis super fast and electric field is produced(because of time varying magnetic field),does this means that in the frame of non moving observer magnetic field no ...
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Help needed for Simple derivation for duality of matter

A teacher told showed me a way to derive an equation which shows the duality of matter. We know, $E=hc/\lambda$. and $E=mc^2$ So, $hc/\lambda=mc^2$ We get, $p$ ( momentum ) = $h/\lambda$. How ...
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Time variable in Lorentz transformations

When an object goes with a speed near from the light celerity, it inflates in the direction of its speed. The inflation rate is given by Lorentz transformations as follows: $x'= γ(x-vt)$ where $v$ ...