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 will be destroyed? The Moon or the Death Star?

The situation: Suppose Death Star passes by the Earth towards the Moon (near speed of light) and fires its laser (starting from the center of Death Star) against the Moon. If the laser gets to the ...
2
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1answer
88 views

What's the deal with Relativistic Mass? [duplicate]

So I have taken a first course in Special Relativity and the Relativistic Mass is defined as: $$m = \frac{m_o}{\sqrt{1 - v^2/c^2}}.$$ Now, when this was introduced in the course, it was introduced as ...
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Is there a bound on spacelike intervals between the trajectories of a pair of chronometrically rigid participants in flat spacetime?

Considering, in flat spacetime, two participants, $A$ and $B$, who were "chronometrically rigid" with respect to each other (i.e. $A$ found constant ping duration with respect to $B$, and $B$ found ...
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1answer
77 views

Invariant mass spectrum to a transverse momentum distribution

For the decay of the Higgs boson in 2 photons having the following invariant mass formula: $$M = 2E_{1}E_{2}(1 - \cos \theta)$$ How can I go from an invariant mass spectrum distribution to a ...
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174 views

Can an object spinning near the speed of light be accelerated significantly in any direction?

This question made me curious. It refers to a ball which is rotating so that its equator is approaching the speed of light, then talks about what it would look like if the observer moved. What I'm ...
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4answers
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Meaning of fourth component of velocity four vector

Can any one help me to understand what the fourth component of velocity four vector mean physically?
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2answers
107 views

Velocity addition rule in special relativity

I just worked out a problem showing peculiarities of the velocity addition rule in special relativity. This was the statement for the problem: "Nefarious thieves flee the scene of their bank ...
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11answers
4k views

What happens if a super fast rotating ball accelerates near speed of light?

Assume we have a ball with diameter 1 meter and mass 1 kg rotating at 99,5% speed of light ...
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4answers
177 views

Astronaut travels 16 lightyears and ages 15 years - am I misreading this question?

The astronaut is travelling to a star sixteen lightyears away. During this trip he ages fifteen years. What is the speed u at which the astronaut travels? It's obvious he can't be traveling at ...
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64 views

Interval nonvariant under Lorentz Transformation [closed]

How do I show that physical quantities don't change after Lorentz transformations?
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0answers
47 views

How does Photon travel in spacetime? [duplicate]

To travel spatially from point A to point B, you have to move in time also. We know that Photon travel with a speed of light, thus in their frame of reference according to special relativity time ...
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6answers
374 views

Reconciling Minkowski and 3+1 view of special relativity

I am having some trouble reconciling the Minkowski (4-dimensional) and the pre-Minkowski (3+1-dimensional) approach to special relativity. Let me describe (how I interpret) the Lorentz transformations ...
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Conceptual problem about the theory of relativity

Suppose a frame F is moving with a relative speed with respect to another frame S. Now, relative to a person in S, clock in F run slowly. Obviously then w.r.to person in F, clock in S run faster. But ...
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108 views

Why don't constant motion charges produce waves?

I'm a little confused about the origin of electromagnetic waves. Although I can understand their origin mathematically, I get a little confused about the physical intuition of... Information ...
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3answers
86 views

Justification of $P_{\text{photon}}=E/c$ in derivation of $E=mc^2$

I recently was reading up on the derivation of $E=mc^2$. Now, I came across this derivation at this link. I noticed that several lines into the derivation they throw in the equation ...
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3answers
146 views

Do relativistic events need to match if accounted for time dilation and length contraction?

To explain the question let me give you a short example. In the scenario there are two references frames A and B. A consists of a x'=1 Ls (lightsecond) long pole ...
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2answers
109 views

How to find kinetic energy given relativistic linear momentum?

The relativistic energy of a particle is given by the expression \begin{equation} E^2 = m^2c^4 + p^2c^2 \end{equation} The rest energy is $E_{0}=mc^2$ and the momentum is $p=mc$. In the rest frame, ...
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3answers
149 views

4-velocities in different frames

We have an observer in an inertial frame $S$ who measures a particle's 4-velocity as $U$. We then have another inertial frame $S'$ with $X'=\Lambda{X}$, where $\Lambda$ is a matrix representing a ...
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65 views

The twin paradox and positively curved space

I'm reading about the twin paradox in special relativity - if there are two identical twins, one of whom who sets off in a high speed rocket to a planet, and then heads back, will find the twin who ...
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3answers
250 views

Muon demonstration of time dilation

Looking at the second paragraph of page 120 here. Is the half life given measured in the rest frame of the muon? Then the calculation shows that the time to reach sea level from the muon's perspective ...
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Mass of a particle ( relativity)

A hypothetical atom has a rest mass of $15.000000136\,\mathrm{u}$. Overtime it undergoes a spontaneous breakdown into two masses of $7.000000229\,\mathrm{u}$ and $6.902727019\,\mathrm{u}$ ...
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72 views

Acceleration of objects with speeds comparable to $c$. Can we find acceleration of the frame by treating $v$ in $1/\sqrt{1-v^2/c^2}$ as variable?

We know that the $v-t$ graph for constant acceleration is a straight line. But when the speed becomes comparable to $c$, the speed of light, relativistic effects come into play. Suppose if a rocket on ...
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41 views

Under what conditions is the time component of proper acceleration zero?

Given the magnitude of a proper acceleration, the derivative of proper velocity with respect to proper time, how do you determine what component is from the spatial vs temporal dimensions. I am led ...
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50 views

Why Space Element of Four Momentum Vector is 3 Momentum Vector?

For example, if we look at the relation between space element of 4-velocity and 3-velocity; and space element of 4-force and 3-force $V = v\cdot\gamma(v)$ $F = f\cdot\gamma(v)$ But ...
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0answers
63 views

Is temperature a frame dependent quantity? [duplicate]

The temperature of an object is proportional to the average kinetic energy (1/2*m*v^2) of its particles (or molecules), then shouldn't the temperature depend on the frame of reference since v^2 will ...
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1answer
96 views

Do photons have no mass? [duplicate]

My Quantum Mechanics' teacher said today on the class that photons don't have mass. I was puzzled because I knew that photons have momentum. If a particle hasn't mass then its momentum sould be $0$ ...
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2answers
87 views

Where does the 3-velocity live?

Imagine a four-dimensional affine space $\mathcal{M}$ with the standard metric $\eta = \text{diag} (1,-1,-1,-1)$. Let $\mathcal{C}$ be a worldline of a point particle parametrized by an affine ...
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Is This Educational Model of Relativity Right? [closed]

After watching and reading about Special Relativity I am still left with some questions unanswered. Can you please tell me if this educational model of relativity, simplified to level of a cartoon, ...
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1answer
62 views

Taking the classical limit $v\ll c$ in special relativity

I'm trying to understand some of my class notes. My professor reached 2 equations: $$m_0c^2 \frac{d\gamma}{dt}=\textbf{F} \cdot \textbf v\tag{1}$$ and $$m_0\frac{d\gamma \textbf v}{dt}=\textbf ...
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1answer
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Can observers in different reference frames agree on the time an event took after the fact?

Ok, I don't think I did a good job of communicating this, so here's a better way to phrase the experiment. There is a spaceship traveling horizontally in the x-direction at near the speed of light ...
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1answer
39 views

Why are the topological dimensions of spatial\timelike\null infinities 0\0\2 respectively?

I have a question regarding spatial, timelike and null infinities in Minkowski spacetime. I shall start with an explanation of my intuitive understanding of these concepts, and then proceed to my ...
3
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1answer
238 views

In what sense is BMS a symmetry? (What is kept invariant?)

Recently I've started to read about BMS (Bondi-Metzner-Sachs), and I've encountered several statements such as the following (from [1]). [I]t turned out that the asymptotic symmetry group at null ...
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Work out components $F^{01}$ and $F^{ij}$ of the antisymmetric tensor $F^{\mu\nu}$ under the Lorentz Transform [closed]

Work out explicitly how the components $F^{0i}$ and $F^{ij}$ of the antysymmetric tensor $F^{\mu\nu}$ introduced in chapter I.6 transform under a Lorentz transformation This problem is from Zee, ...
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1answer
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Did Einstein plagiarize Poincare? [closed]

http://www.bibliotecapleyades.net/esp_einstein.htm This site makes such claims including: Jules Henri Poincaré (1854 - 1912) was a great scientist who made a significant contribution to special ...
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What is the equation of a ellipsoid in motion and how to obtain its semi-axes? [closed]

The equation of an ellipsoid is given by $$\dfrac{x^2}{a^2}+\dfrac{y^2}{b^2}+\dfrac{z^2}{p^2}=1$$ where $a,b,p$ are the length of the semi-axes. If $a=b=p=R$ then this ellipsoid is a sphere of radius ...
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1answer
81 views

Warp Drive conundrum - Speculative science question [closed]

Let me begin by stating that this question about Warp Engines/Drives, which i understand is a speculative, also I am not a Professional scientist or someone with a degree in physics. The question will ...
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3answers
403 views

How to prove a symmetric tensor is indeed a tensor?

Our professor defined a rank $(k,l)$ tensor as something that transforms like a tensor as follows: $$T^{\mu_1' \mu_2'...\mu_k'}{}_{\nu_1'\nu_2'...\nu_l'} ~=~ ...
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4answers
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Are photons inside the media massive? If yes, why there is no Meissner effect?

We all know in vacuum travels with speed $c$, hence its rest mass has to be 0. In the media the light speed $v<c$. Then the photon renormalized by the medium (call it "quasi-photon" if you like), ...
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1answer
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De Broglie wavelength of a massive particle as v approaches c

We understand that from a relativistic version of De Broglie's wavelength-momentum relation that as velocity approaches 0 the wavelength trends to infinity and as velocity approaches the speed of ...
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84 views

Electromagnetism and a simple doubt [duplicate]

Why don't electromagnetic waves need a medium to propagate? How does light get such a magnificent velocity?
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73 views

Can light travel with a speed less than its speed at same time?

I know that the velocity of light with respect to anything is constant ($c$) . What, then, is velocity of light with respect to light?
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1answer
91 views

Heisenbergs Uncertainty Principle in different intertial frames

Say there is a single particle in a box. If we switch to a different inertial frame (without the box) travelling close to the speed of light we see the box get smaller. At a high enough speed the ...
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1answer
45 views

How is $\dfrac{A^2}{8\pi}$ is the energy per unit volume of light?

In his 1905 paper, under the section: 8. Transformation of the Energy of Light Rays. Theory of the Pressure of Radiation Exerted on Perfect Reflectors, Einstein states: Since $\dfrac{A^2}{8\pi}$ ...
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1answer
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What do we mean by saying that one clock had been “running slower” than another clock; or that two clocks had been “running equally”?

Several posts on this site, especially on the topic of relativity, refer to comparisons between clocks in terms of their "running"; one having "run faster" than the other, one having "run slower" than ...
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397 views

Explanation of Supplee's paradox

I was reading about Supplee's paradox, which is about whether a relativistic projectile, subject to uniform gravitational acceleration, would float or sink underwater. However the solution of the ...
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1answer
69 views

Time Dilation When In Orbit

Imagine a space ship orbiting the sun at near relativistic speeds, when compared to Earth (say from the reference frame of the sun) there would be x amount of time dilation. This would mean people on ...
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1answer
113 views

Is the amplitude proportional to frequency in electromagnetic waves?

In Einstein's 1905 paper, under the section: § 7. Theory of Doppler’s Principle and of Aberration Einstein derived the relativistic Doppler effect: $$f'=f\dfrac{1-\cos\phi \cdot ...
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1answer
128 views

Is there any way to measure the one-way speed of light?

Is there any way (practical or theoretical) to measure the one-way speed of light? The two methods that come to mind are: Stellar aberration, and Using adiabatic clocks: synchronize clocks, then ...
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1answer
69 views

Why $x=-ct$ line in a spacetime diagram?

I can understand why the $x=ct$ line is needed as follows: If $c \Delta t \geq \Delta x$ then the event can be causally related to your current position, so the event could not appear in reverse ...
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Alongside a light ray (in another medium)

It is a said fact that the speed of light is insurmountable. But can the validity of this fact be questioned in another medium? If I pass a beam of light in, say water (here the light speed is ...