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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What is the irreducible set of fundamental principles of Special Relativity?

This is something that I have been pondering for some time. The fundamental principles of special relativity are usually presented as forming a twofold: There is no absolute reference frame of ...
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1answer
29 views

Maximum Angular Momentum for an orbit in GR

[The reference for this question is the book Gravitation by Misner,Thorne, & Wheeler.] The trajectories of massive particles around a spherically symmetric body is governed by the effective ...
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1answer
36 views

Why speed of light is constant with respect to any inertial frame of reference? [duplicate]

Its getting too difficult to think.if we travel at the speed of light then will light will cross us at same speed or travel with us adjacent (special theory of relativity)
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24 views

Total dilation of a signal from Tau Sagittarii [on hold]

Please forgive my ignorance, but I'm attempting to figure out how to do this... I want to learn how to evaluate the total dilation of a signal (waveform) leaving Tau Sagittarii to us. This assumes ...
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1answer
38 views

use of earth magnetic field

If we use earth magnetic field as a big magnet and take earth opposite charged electromagnet than it is possible that earth opposite charged electromagnet repel from earth surface.
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Question on the Derivation of Lorentz Invariance of Electric Charge

On Zwiebach's "A First Course in String Theory" textbook, there is a problem 8.2 that derives the invariance of electric charge given a few assumptions: 1. Conservation of Maxwell 4-current $j = (c\...
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If the four velocity of a photon is undefined, what can we say about the velocity of a photon? Is Brian Greene right about motion through spacetime? [on hold]

Edit: THIS QUESTION IS ASKING ABOUT THE FOUR VELOCITY OF A PHOTON. THE PREVIOUS QUESTION DOES NOT. PLEASE ANSWER THIS QUESTION, WHICH HAS NOT BEEN ASKED. If the four velocity of a photon is ...
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Do electronic energy levels of an atom effectively shift for scattering processes if the atom is moving in the lab frame?

When an electron of low energy scatters off an atom it interacts with one of the electrons in its shell and can transfer energy to it. The energy transfers would be discrete, since the shell electron ...
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1answer
66 views

One particle states in an interacting theory

Question: What is the general definition of one particle states $|\vec p\rangle$ in an interacting QFT? By general I mean non-perturbative and non-asymptotic. Context. 1) For example, in Weigand'...
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1answer
58 views

Lorentz Transformations in Minkowski space

If $\Lambda$ represents the Lorentz transformation matrix, then the transformation of contravariant components $x^\mu$ is given by $$x'^\mu=\Lambda^{\mu}{}_{\nu} x^\nu$$ and that of the covariant ...
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4answers
110 views

If a photon has no mass why doesn't it have infinite speed? [duplicate]

Please help a naïve layperson understand -- if a photon has no mass, why is its velocity limited at all? Shouldn't a particle with no mass be able to travel at an infinite speed?
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1answer
52 views

Deriving invariance of interval

I'm reading a book called A First Course In General Relativity, and when I got to the invariance of the interval, the book didn't derive it. Also, when the book derived time dilation and Lorentz ...
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47 views

Twin paradox without gravity [on hold]

Suppose we have 3 people Person1 was already born on a spaceship that travels in the speed of 0.5c toward person2 Person2 was born in a point in point in the space also in the exact time of person1 ...
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22 views

Is mass relative? [duplicate]

This question has to do with the relativistic mass of an object. I have been reading that as energy increases, so does mass to a much lesser extent, and that this applies to kinetic energy as well. ...
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34 views

What is the irreducible decomposition of the tensor product of left and right weyl spinor representations, i.e. $(1/2,0)⊗(0,1/2)$?

What is the irreducible decomposition of the tensor product of left and right weyl spinor representations of the group $SL(2,\mathbb{C})$, i.e. $(1/2,0)⊗(0,1/2)$? I mean, the tensor product of two ...
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3answers
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Length contraction in special relativity: can space be at rest in any frame?

Suppose a rod is moving at speed $v$ relative to me along its length. $L_0 = {}$length of the rod in the frame in which the rod is at rest $L = {}$length of the rod in my frame Then $$L = L_0 \sqrt{1-...
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67 views

Lorentz transformation: Can distance between two observers depend on the observers? [on hold]

Consider reference frames S and S'. S' is moving in positive x direction at speed v relative to S. Time measured by S is t and that measured by S' is t'. When t = 0, then t'= 0. Coordinate systems ...
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Special Relativity Problem: What's wrong here? [on hold]

Two 1 kg blocks float in space. After an explosion, they move left and right at 0.6 c. Consider their momentum relative to a frame of reference moving a 0.6 c to the right relative to their center of ...
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1answer
71 views

Proof of two Lorentz-algebra identities

I am currently working through the QFT introduction text by Peskin and Schroeder and try to fill in two identities that I wasn't able to prove (it should be fairly simple, but my experience with this ...
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1answer
41 views

A puzzler in induction and special relativity

Some reading I was doing jogged my memory about a puzzle in E&M that hit me back in my undergrad days, but I just let it go at the time and never found an answer. A pretty common undergrad E&...
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29 views

Can orbiting a black hole 99.99% speed of light make other object with relatively fast clock travel faster than light, relative to me?

If i orbit a black hole, 99.9% speed of light, time for me is moving slowly, relative to me, planet earth is aging fast, and i have traveled 10 years into the future(relatively) in 1 second, suppose ...
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Imagine I'm on a spacecraft that was accelerated to 1.0$c$ could I only move backwards? [duplicate]

Imagine I'm in a sapcecraft1 that is moving with 1.0$c$ or at least is so close to that speed that a few miles per hour would just be left to reach $c$. So when I'm traveling now in the direction ...
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What exactly were the “asymmetries which do not appear to be inherent in the phenomena” in Einstein's 1905 SR paper?

The first ¶ of Einstein's "On the Electrodynamics of Moving Bodies" says (my emphases): It is known that Maxwell's electrodynamics—as usually understood at the present time—when applied to moving ...
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3answers
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Why must $v$ be $< c$ in the Lorentz transformations? Do these equations not apply to light? [duplicate]

I was trying to understand how things look from the perspective of light. Looking at the Lorentz transformations, it seems that the universe would contract along the direction of movement into a plane,...
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What did Einstein contribute to Special Relativity that hadn't already been done by Lorentz in 1904 and Poincaré in 1905? [duplicate]

What did Einstein contribute to what is now called Special Relativity theory that hadn't already been done by Lorentz in his 1904 "Electromagnetic Phenomena in a System Moving with any Velocity ...
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81 views

What is the geometric explanation for why the interior angles of a triangle sum to 180 degrees in both Euclidean space and Minkowski spacetime?

Four-dimensional Euclidean space has the same topology and affine structure as Minkowski spacetime, though the two have different metric structures. Given that the interior angles of a triangle ...
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Kinetic Energy Relativistic Correction

When trying to add relativistic corrections to the standard Schrödinger equation, the kinetic energy correction is given as $H'=-\frac{p^4}{8m^3c^2}$ (e.g. page 14 https://www.tcd.ie/Physics/people/...
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Do Physical Singularities Exist? Is Mass Infinite at $v=c$? [closed]

Looking at the Minkowski light cone and the STR on the Boundary at $v=c$. STR calculates infinite mass/infinite energy which would burn the universe to a crisp. Aren't we simply saying Undefined; and, ...
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Relativity - Twin Paradox and Absolute Frame of Reference - Why Not? [closed]

Absolute Reference Frame is a very discussed topic here and at other forums. For me it seems natural that the Relativity twin paradox should be explain in respect to such frame. The wikipedia article ...
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1answer
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Speed of light from moving source evidence [closed]

The speed of light in a vacuum is taken to be a constant $c$ from a light source moving in our frame. What experiment(s) provide direct evidence for this. To what level of precision do we know this ?
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77 views

Why cannot Paul be the observer? (Questions about Twin Paradox)

Here is the explanation to the Twin Paradox in Feynman's Lecture on Physics 16–2. we consider a famous so-called “paradox” of Peter and Paul, who are supposed to be twins, born at the same time. ...
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Special Relativity - oscillator paradox

I am reading about the Special relativity and the original Einstein papers from 1905 and 1920 where he derives the Lorentz transformation and the effects of the time dilation and space contraction ...
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1answer
38 views

By special relativity, a particle can only couple to an EM field? [closed]

By special relativity, the Lagrangian for the coupling must be $$ u_i A^i . $$ Here $u_i $ is the four-velocity, and $A^i$ is the four-potential. So, a particle can only couple to an EM field? ...
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Conceptual interpretation of the left- and right-handed spinor representations of the Lorentz group

I understand mathematically that the Lorentz group's Lie algrebra $\mathfrak{so(3,1)}$ (given by eqns. (33.11)-(33.13) in Srednicki's QFT book) is isomorphic to $\mathfrak{su(2) \times su(2)}$ (given ...
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1answer
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What is physical meaning of Lorentz boost?

Physical meaning of spatial part of Lorentz transform is, obviously, rotations in R-space. Does anybody have a nice physical interpretation of boosts though? I can understand to some extent off-...
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Symmetry, Space-Time interval, and Coordinate Time

I had the following question I was working from a book: Question: A physics professor runs across the hallway covering 120 ns of distance in 150 ns of time as measured in the frame of the earth....
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47 views

From gauge invariance to charge conservation in covariant electrodynamics

I tried to solve the equations of motion using the action for the electromagnetic field interacting with a current, like $$ L = F_{\mu\nu}F^{\mu\nu} + A_{\nu}j^{\nu} $$ getting the right Maxwell's ...
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1answer
52 views

Speed of light when accelerating

I'm studying special relativity and saw the 2 postulates of Einstein. The most remarkable one for me is the universal speed of light. Einstein postulated that the speed of light in vacuum is the same ...
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1answer
26 views

Does increasing the energy of a relativistic particle increase thrust?

I know this particular chestnut has been asked before, but I have a specific variation on the theme: Particle accelerator space thrust. Specifically, cyclotrons to generate the thrust. They are ideal ...
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1answer
36 views

What happens to forces when a charge travels at near c?

Suppose 3 electrons are travelling at $c - 1$mm at 1 cm distance The charges are at rest relative to one another in their frame, but what happens to fundamental forces Fe and Fg? What Fe does A get ...
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Can the momentum of a system be spacelike?

For a particle, we always have $Eu=p$ where $u$ is the speed of the particle and correspondingly the momentum is always timelike. For a system of particles, if the potential energy is not considered ...
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2answers
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A method of showing how mass increases with higher velocity. I don't get it

I am a high schooler interested in physics and recently started reading a book about relativity. The name of the book is "What Is Relativity" by Jeffrey Bennet. In page 54 there is a paragraph that ...
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1answer
146 views

Strange implication of the relativistic invariance of the Dirac equation

At least as normally formulated, the law of transformation of a wave function solution of the Dirac equation to another inertial frame seems to indicate that if observer 1 is certain the particle is ...
2
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1answer
63 views

Lorentz transformation of an antisymmetric tensor

I'm trying to find the infinitesimal Lorentz transformation of a rank 2 antisymmetric tensor. Looking through Peskin, all I can see is the transformation of a vector, and even there it is simply given....
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1answer
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Is this the correct method for deriving E=mc^2?

So lately I tried to deriving Einstein's $$ E = mc^2$$ which later I found from this website : http://www.emc2-explained.info/Emc2/Derive.htm They use calculus based method, so I tried another way. ...
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1answer
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Invariant upper bound for velocity of a particle

In the book Relativity book by Wolfgang Rindler, he explains that the Galilean and Lorentz transformations exhaust all the possible transformations. And explaining that he says, "Now, either there is, ...
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Another Special Relativity Paradox inspired by Herbert Dingle's Paradox

Suppose spaceships A and B with clocks A and B move along the same straight line at uniform speeds differing by 161 miles per second. At the moment when B passes A, their clocks both read noon. ...
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How does the comparison of rates depend on mutual speed?

If I'm moving with a considerable fraction of speed of light, the time and any process in my system will be going slower. If B is an outstanding person that is watching me passing by, he will see ...