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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Has the effect of magnetic fields on time ever been examined experimentally?

Relativity of time can be examined with satellites as gravitational or acceleration. Is there any similar experiment with intense magnetic fields?
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Speed of light, comparison of two light waves travelling side by side

okay so.here is setup of my question...say we have two observers A and A'..A is fixed to origin of coordinate axis x,y while A' is inside a hollow box (shown as rectangle MNRP) whose one side MN has ...
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Negative energy of free particle: classical and quantum picture

Classically, the energy of a free particle consists of only the kinetic energy given by $E=\frac{|\textbf{p}|^2}{2m}$ Since $|\textbf{p}| $is real and $m>0$, $E\geq 0$. However, since ...
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1answer
25 views

Time for two relativistic objects to meet

How do you prove that the time for two objects traveling towards each other at relativistic velocities is still d/(v1+v2). Answer seems to have something to do with velocity addition but I'm ...
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Trajectories in Rindler space with zero net time dilation

I've discovered a family of curves in Rindler space that have zero net time dilation. However I struggle to see why this should be so, i.e. what the physical significance of these curves is. My ...
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What speeds are “fast” enough for one to need the relativistic velocity addition formula?

In this question the accepted answer says: For objects moving at low speeds, your intuition is correct: say the bus move at speed $v$ relative to earth, and you run at speed $u$ on the bus, then ...
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Travelling twin's clock in twin paradox on the way back

Suppose the situation of the twin paradox: twin A stays on Earth, the other (B) goes to a star with velocity $v$, and at the beginning of the journey their clocks were synhronized. We know that when A ...
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1answer
52 views

Superluminal speed?

I came by the quotation below. I'm confused: does it mean that it's actually possible for light and even material objects to move faster than light? Gravitational fields are present the velocities ...
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1answer
48 views

What would happen to the human body if we went almost at the speed of light? [duplicate]

If we were to travel almost at $299\,792\,458~m/s$, or the speed of light, what would happen to the human body? Would we be fine or would there be consequences? Would our body shut down? I've been ...
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0answers
15 views

A Relativity question about radial acceleration? [duplicate]

How do you calculate the radial acceleration of a stationary observer in the Schwarzschild coordinates? I have calculated the 4-velocity and 4-acceleration but not sure how to proceed?
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2answers
63 views

Lorentz Transformations and time of event

Consider two inertial frames, $F$ and $F'$, such that $F'$ moves at $\mathbf{v} = (v,0,0)$ with respect to $F$ (assume $v > 0$). Suppose tat $x = x\prime = 0$, when $t = t' = 0$, where $x,t$ refer ...
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Special relativity question [on hold]

I have a problem. I´m trying to solve this, but I have no idea how to start, how to understand it. We have two objects moving away from each other, each has a speed $v$. We measure time in the system ...
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special relativity with four vectors [on hold]

I am new in the group and I have an exam on electromagnetism with special relativity tomorrow and I really stack on four vectors. It's the first time that I encounter four vectors. I got formulas in ...
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1answer
257 views

How come the concept of an instant of time is such a controversial topic with relativity, but with entanglement it's completely acceptable?

When talking about relativity most people say that a universal instant of time doesn't exist, but when talking about entanglement most will say that the particles are both measured instantaneously. ...
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Why doesn’t the Sagnac Effect disprove relativity?

It was my understanding that the speed of light is supposed to be constant for every observer, as in the classical mental experiment of the guy in the train with the flashlights which explain the ...
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48 views

A general relativity question about 4-velocity? [on hold]

In a general spacetime with metric $g_{\alpha\beta}$ where there exists coordinates such that there are observers with 4-velocity $u^{\mu} = \{1,0,0,0\}$, show that $$ g_{00} = -1 ...
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35 views

Could unfound matter travel faster than light? [duplicate]

Is it impossible to go faster than the speed of light or is it just that we have not yet found anything that travels faster?
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32 views

Theoritical outcome of rotating a disk of infinite strength at or near the speed of light [on hold]

If you rotate a disk of infinite strength at, or near, the speed of light; will this produce something with a fourth dimension?
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1answer
72 views

Does scale invariance imply massless or continuous mass distribution?

$\newcommand{\ket}[1]{\lvert #1 \rangle}\newcommand{\bra}[1]{\langle #1 \rvert}\newcommand{\scp}[2]{\langle #1 \vert #2 \rangle}$ In his 2008 slides Unparticle Phenomenology (PDF), Tzu-Chiang Yuan ...
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Camera on the ground vs camera in a train

A couple days ago my history teacher was explaining special relativity with the train example, where you are in a train close to light speed and you see a clock on the train terminal and the clock ...
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60 views

Does Special Relativity Define a Number divided by 0? [duplicate]

As a new student of special relativity, I am confused by the statement light experiences no time, because $$∆t = {∆t_0\over\sqrt{1-{v^2\over c^2}}}$$ Wouldn't that imply that ${1\over0}= ...
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Lagrangian for free particle in special relativity

From definition of Lagrangian: $L = T - U$. As I understand for free particle ($U = 0$) one should write $L = T$. In special relativity we want Lorentz-invariant action thus we define free-particle ...
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Is macroscopic causality an issue in the context of certain quantum experiments?

In order to formulate my question properly I need to explain a few things. Cramer_Herbert Zych_Brukner Reference 1. - John Cramer, Nick Herbert, "An Inquiry into the Possibility of Nonlocal Quantum ...
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Time dilation problem [closed]

A person on Earth signals with a laser beam at 6 minute intervals. Another person on a rocket moving away from Earth at 0.600c detects the signals. At what time intervals does the person on the rocket ...
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2answers
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Watching a LIVE stream in spaceship traveling away from earth close to speed of light

My name is Dennis. This might sound just straight up ignorant of basic concepts of physics. I was having a conversation with my friend in regards to streaming a LIVE event on earth to a spaceship ...
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Traveling near the speed of light

If I travel near the speed of light, form a stationary observer perspectives, I will take 1 year plus to travel 1 light year, but in my perspective, would I take less than 1 year to travel to that ...
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Is cause-effect always preserved in relativity?

I guess most of you are familiar with the "paradox" of the train passing through a tunnel smaller than itself on a speed close to the speed of light and 2 guillotines (1 in the exit and 1 in the ...
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Is Lorentz transformation applicable of light itself?

I've just studied Einstein's Special Theory of Relativity and have followed most part of it. I was just wondering that whether the equations of Lorentz transformation are applicable on light? i.e. can ...
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49 views

Frames of reference and why are they different

Here is a quote from "The Elegant Universe" by Brian Greene. Imagine two countries that have been at war are sitting down to sign a treaty ending hostilities while traveling aboard a train that is ...
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2answers
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“Derivation” of Minkowski metric?

Is there a deeper meaning behind the the Minkowski metric? Does it just come from the SR formulae? Or is there some deeper geometrical meaning, maybe in the context of GR?
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Time dilation. Why?

We are able to predict, measure and mathematically demonstrate time dilation, but are we able to explain 'why' it happens? what would be that explanation? Edit1 Think the question backwards: After ...
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1answer
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4 dimensional interpretation

Has it ever been hypothetized that, in a 4 dimensional space, being time the 4th D, one body could travel through the dimensions at the combined speed of $c$? If a body is at rest in the classical 3 ...
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Faster than light [closed]

I have been reading Professor Feynman's QED and I have a question.I hope this is the right place to ask it. In the book the Professor states that the speed of photons that is light can be more than ...
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3answers
58 views

Our speed and direction by comparing the speed of light?

If the speed of light is constant no matter the speed of the source, shouldn't we be able to know the direction and exact speed we are going relative to the absolute 0 in speed? If a photon is sent in ...
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Relativity and quantum mechanics in everyday tools [closed]

could you suggest me some everyday tools where technology is directly linked with quantum mechanics or relativity? I mean, computers are linked with quantum mechanics because of transistors, but I'd ...
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1answer
52 views

Time flow difference for satellites [duplicate]

Clocks in satellites have to be adjusted due to the effects of relativity; but does time for satellites (GPS) flow slower, due to the relative motion, or faster, due to the weaker amount of ...
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1answer
23 views

Do the mediums decrease or increase the speed of light? (source to target) [duplicate]

If sun is the source of light then is it possible that the speed of light might increase depending on the mediums its going through or its not possible.
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1answer
58 views

Planck length paradox [closed]

This is a paradox I thought of a few days ago, and I wanted to ask whether it makes any sense and where the mistake is. We know that the nothing but light can move faster than light itself. So in a ...
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What does it mean to perturb the electromagnetic energy with respect to a change in a Lorentz frame?

I am perturbing the energy of an electromagnetic field using \begin{align} \dfrac{\partial U}{\partial \zeta} = \dfrac{1}{\mu} \boldsymbol{H}\cdot \dfrac{\partial \boldsymbol{H}}{\partial \zeta} + ...
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3answers
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magnet moving in space

I know that a time varying magnetic field produces an electric field even in the absence of a conducting body, because thats how em waves work. But can you say the same for a space varying magnetic ...
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How to construct generators and Lie Algebra for Lorentz group?

I'm trying to figure out Lorentz group in 2+1. First of all, I'd like to think the special orthgonal group as a combination of rotation and boost in space. Then I construct it as below. First rotation ...
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is speed of light is the limit [closed]

If an electron is away from a proton about 1 kilometer and the proton is fixed what will be the velocity of electron when they collide? I calculated it its speed was coming out to be more than the ...
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1answer
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Relativistic momentum of an electron

Suppose we have some interaction between a photon and an (initially) stationary electron, and we wished to find the final momentum of the electron. Should we solve this using conservation of momentum, ...
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Is there any upper limit on a particles kinetic energy?

While the speed of light is the "ultimate speed limit" for any particle.. Is there any upper limit to kinetic energy?
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Symmetric Time Dilation in Uniform Relative Motion

I feel (and hope) this is an easily answerable question among physicists versed in GR. I promise that I searched for other answers on the forum. Here goes: Observer 1 starts at X distance from ...
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The speed of light sets a lower limit to the rate at which a reference frame can pass through time. Is there anything that sets an upper limit? [duplicate]

Is there any "slowest" velocity that sets a cap on how fast a reference frame passes through time, or can you pass through time infinitely fast given a "slow" enough velocity?
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speed of light and conservation of linear momentum

Acoording to the results of Michelson–Morley experiment, the speed of light is constant regardless of the velocity of the source. Now, I want someone to correct me if I am mistaking about the ...
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Both Special and General Relativity carry long term unresolved paradoxes. Should not they now be “inconsistencies”? [closed]

I thought when a theory carries paradoxes, and they go unresolved, eventually they get called inconsistencies and the theory is assumed wrong somewhere. GR doesn't work at distances, say between ...
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Amount of energy received from photons when traveling at near-light speed? [closed]

Special Relativity says that when you are traveling in a rocket ship at near-light speed, in effect your clocks "tick slower", however from your reference frame every one else's clocks "run slower". ...
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The Twin Paradox - Acceleration Is Relative [duplicate]

So here is how i explained the twin paradox to myself. The question is. Do you agree with this explanation? The twin paradox can be fully explained with SR. (no paradox at all but perfectly in accord ...