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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Why is locality an important requirement in physics?

Why is locality insisted upon in physics? Is it simple because empirical evidence suggests it, and also taking relativity into account, required due to the upper limit of propagation limited by the ...
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Lorentz Transformations understanding

I am wondering whether or not I fully understood what the variables represent in the Lorentz time and distance transformations. What I understand is: t′ is the 'proper time', the time taken to move ...
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A question in Special Relativity

In books the equation for length contraction is derived by supposing that the velocity of the spacecraft is the same for both observers. So the question is that, is the velocity really the same for ...
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Firing counter-propagating photons inside a moving train

This is sort of a follow-up to my other question, in which you have the following scenario: Have a photon gun firing two counter-propogating photons from the center of a moving train. The observer ...
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What happens when breaking simultaneity leads to different outcomes?

Consider the classic example to show that simultaneity does not hold: Have a photon gun firing two counter-propogating photons from the center of a moving train. The observer inside the train sees ...
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invariant angles in Minkowski space

Invariant intervals are fundamental in relativity. But if you make a triangle in space-time from 3 invariant intervals, then it will also have 3 invariant angles, by the cosine law which can easily be ...
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Velocity of approach of a beam of light and a moving object

I came across a problem on Brian Greene's course on Special Relativity. (http://www.worldscienceu.com/courses/6/elements/TnRUSU) From George's perspective, how fast does a beam of light approach ...
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Geometric definition of the Lorentz inner product

In Euclidean space one can define the dot product as projecting one vector to the other and multiply the length of the projected vector with the length of the other vector. This definition doesn't ...
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Video of light passing through water

How is this possible? https://www.youtube.com/watch?v=EtsXgODHMWk Video shows beam of light travelling through water. I was under impression that Einstein's equations showed that light speed is ...
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What are some ways to measure variations in the speed of light in vacuum?

To avoid confusion, I am not talking about measuring differences in the speed of light in vacuum as a result of a particular Lorentz boost. What I mean is, suppose the "constant speed of light" were ...
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What is meant by “the Klein-Gordon equation is unsymmetrical between the temporal and spatial components”, and why is this a problem? [closed]

The Klein-Gordon equation explicitly reads $\left( \frac{\partial ^2}{c^2\partial t^2} - \nabla ^2+\left( \frac{m_0 c}{\hbar}\right)^2\right) \psi =0$ Now I read here on page 8 that: What is ...
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Relativistic Energy

The question stated: By what percentage does your rest mass increase when you climb 30m to the top of a ten-story building? New to the concept of relativistic energy, I was a bit confused with ...
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Regarding different representations of the Lorentz Group & its defining properties

Take $\Lambda$ to be a Lorentz matrix, it satisfying $\Lambda^T \eta \Lambda=\eta$. By writing $\Lambda=\exp[-\frac{i}{2}\omega_{\mu\nu}\mathcal J^{\mu\nu}]$, we find that the generators satisfy $$ ...
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Are photons just electric waves in an electron's frame of reference?

They say that electrons emit photons when they jump to a lower orbit. But the way electrons should see it, there's no any emission, really. There's just rapid change in electric field due to a rapid ...
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Using Lorentz transformations

The question states that two particles in a high-energy accelerator experiment approach each other head-on with a relative speed of $0.890 \, c$. Both particles travel at the same speed on a straight ...
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Einstein on a train paradox: what's the resolution?

Okay, so Einstein is on a train looking at a mirror. The train is moving at $c - 1 \frac ms$. Einstein is facing in the direction of motion. All along the side of the train are stationary clocks. ...
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The effects of special relativity when accounting for two reference frames

If reference frame A is travelling past reference frame B could one argue that it is in fact B that is motionless as their motion is relative to each other? If this is the case then how does one ...
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Is there a reason why a relativistic quantum theory of a single fermion exists, but of a single scalar not?

When we try to construct the relativistic generalization of non-relativistic time dependent Schroedinger equation, there are at least two possible completions - Klein-Gordon equation and Dirac ...
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Why is the speed of light limited to (only) 299.792.458 m/s? [closed]

The speed of light (in a vacuum) is limited to 299.792.458 m/s. This sounds very fast, and it is on a global scale. But if you look at the Universe on a larger scale than it sounds quite slow, For ...
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Could light be limiting towards a more fundamental speed limit? [closed]

Could it be possible (as in strictly speaking, no evidence going against this) that light could be limiting towards a more fundamental speed, and that light truly does slow down when a mass goes a ...
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Special Relativity: Time Dilation

I am having difficulty solving the following problem: How fast must a rocket travel relative to the earth so that time in the rocket "slows down" to half its rate as measured by earth-based ...
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What does the first postulate of specially relativity really say?

I know these two versions of the same postulate is saying the same thing. But I failed to connect them. Please help me understand the links between them. version1 The laws of physics are the same ...
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Event times in different reference frames in the context of Special Relativity

I'm having a bit of difficulty puzzling out the correct way to move between frames in the context of a basic Special Relativity problem. The problem basically states that two bodies ($A$ and $B$) ...
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Problem conserving 4-momentum at CoM frame in an inelastic collision [closed]

I am confused about the case where mass is not conserved in a collision (not due to relativistic factors). The center of momentum (CoM) frame is not the same before and after the collision. Let's ...
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Energy in the Relativistic COM Frame

I have been taught that in Classical Mechanics, the total energy of a system of two particles in the Centre of Mass Frame is given by $$ E_\mathrm{total} = \frac{1}{2}MV^2 + \frac{1}{2}\mu v_r^2 $$ ...
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Would it be ok to say that not all light travels at the same speed when you consider its own perspective? [duplicate]

The reason I am asking is because higher energy would cause greater gravitational time dilation. Therefore I would expect, from the perspective of a radio wave, a gamma ray having more energy would ...
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Definition of probablity current in dirac space not including spatial dimension?

I'm currently reviewing (basic) relativistic quantum mechanics and stumbled upon the probability current in "dirac space", defined as $j^μ = (j^0,\vec j)^\mathrm T$ with $j^0 = c\,ρ = c\,ψ^+ψ$ and ...
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Lorentz Symmetry

Quick question about Lorentz symmetry. From the wiki page the feature of nature that says experimental results are independent of the orientation or the boost velocity of the laboratory through ...
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Is this statement correct or incorrect: Moving objects undergo length contraction because they appear in space-time cross-section

Why or why not? This is closely related to another question I posited here, Does it make sense to say that objects moving at relativistic velocities appear in space-time cross-section? What I mean ...
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Is Lorentz Transformation about the difference of coordinates or coordinates of itself?

I have seen different authorities talking about different interpretation of Lorentz transformation. In his book 'Introduction to Classical Mechanics', David Morin states We always talk about eh ...
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Relative Lorentz factor for two shells

Shell 1 is travelling at a speed $v_1$ with Lorentz factor $\Gamma_1$, and shell 2 at speed $v_2$ with Lorentz factor $\Gamma_2$. Just before the two shells meet, the relative lorentz factor ...
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Does it make sense to say that objects moving at relativistic velocities appear in space-time cross-section?

Let object A move at relativistic velocity relative to a frame O. In 4D space-time (Minkowski diagram) the space view of O at any given moment of its own time is a space-like hypersurface (hyperplane, ...
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Distance and Time

I understand that if an object is 10 light years away then the light I am seeing from that object is actually from 10 years ago. If this is the case, which a few posts on this forum seem to concur, ...
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Twin Paradox Problem

In every book the solution of twin paradox is that one have to accelerate thus two observer does not trace parallel lorentz vectors thus can't be compared. Through GR we get the one who accelerate ...
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The chirality of (2+1)D Dirac equation

Are there any definitions about the chirality of (2+1)D Dirac equation? For the (3+1)D Dirac equation, the Dirac field can be written as the sum of left- and right-hand Weyl field. Can this be reduced ...
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Navigating to a distant star

Suppose I have a space ship that can travel at $0.9c$, and I'm going to a star located at 20 light years or so from the Sun. From a practical point of view, if I keep pointing the nose of my space ...
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What happens to the observed thermal energy of objects at relativistic speeds?

When an object is observed to move near the speed of light, what difference in thermal energy is observed? Does time dilation imply that it's colder?
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Will I sunburn faster when driving compared to being parked?

I'm not sure if the same logic applies to light and rain when comparing running/driving with a stagnant situation. See, e.g. Why does driving faster make my windshield catch more rain? Suppose I have ...
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time distortion

Observer A is standing on a planet, and observer B is on a ship. At t=0 B is 1 light year away from A. Also at t=0 B will accelerate its ship to a 0,999999999...$c$ instantaneously (yes, its a very ...
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Is the car/wall comparison valid for speeds close to $c$? [duplicate]

At school, people commonly think about momentum and conservation of energy using the example of a car collision. A common phrase is "Do not try to think of two objects moving, think of one moving at ...
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Will objects heat up and become hidden at relativistic speed?

Let us assume there is a mirror travelling at extremely relativistic speeds, perhaps few picometers away from speed of light, and let us assume we have a very thin detector which is very small perhaps ...
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Objects colliding at relativistic speeds combined energy?

LHC is currently capable of accelerating a batch of atoms faster than $0.5 \, c$. What if we made a second LHC that intersects the original at, lets say the atlas chamber, but that runs in the ...
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Length Contraction Understanding Problem

Suppose a ball moving with 0.9c in the x-axis on a frame S' with axes parallel to frame S on which an observer sees the ball. Due to length contraction it appears as a vertical ellipsoid, when it ...
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Would Michelson-Morkey experiment measure wind in non-vacuum?

If we derive the speed of light from the Maxwell equations we will find it's a function of the permittivity and permeability of the medium. Now let's play with the thought that we are living in a ...
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Increase of an electron's (relativistic) mass

Considering the equivalence of mass and energy, is we want to increase the (relativistic) mass of an electron 1000 times, should we give it 5*10^5 * 1000 = 5*10^8 eV of Kinetic energy => 1001 electron ...