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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In a nuclear reaction, where does the energy go?

Lets say two hydrogen fuse together, where does the energy released go? Is it carried away as momentum imparted on the helium atom? Is it carried away in neutrinos? Is it carried away as gamma rays? ...
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3answers
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What experiments have been done that confirm $E=mc^2$?

What experiments have been done that confirm $E=mc^2$? Are there experimental results that contradict $E=mc^2$? Or are experimental results consistently showing this famous formula to be true?
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Michelson-Morley expression for relative phase

I am trying to find the relative phase when ether is propagating vertically versus when ether is propagating horizontally. The question is written below When the light (of wavelength) is split at the ...
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2answers
98 views

Deduce time dilation from a Minkowski diagram?

Is it possible to deduce the phenomena of time dilation from a carefully constructed Minkowski diagram? For example, consider the image below. Here, Let us say the Euclidean distance between the ...
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1answer
29 views

If changing inertial reference changes velocity/energy, shouldn't that produce conflicting observations of gravity?

A particle $X$ has mass $m$ and passes above observer $A$ with an apparent horizontal velocity $v$. Colinear with these is another observer $B$ moving with apparent horizontal velocity $u$. Colinear ...
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1answer
60 views

Why does photon have to travel in sideways to hit the light clock?

From this article, Let’s say Alice is holding a light clock, and Bob is watching her run by, while holding it, with speed V. Alice is standing still (according to Alice), and the time,$ \tau$, ...
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Given the intervals of a punctured flat spacetime how to reconstruct the intervals of the complete flat spacetime?

A set $\mathcal S$ of events can be characterized as a flat unbounded spacetime through a function $s^2 : \mathcal S \times \mathcal S \rightarrow \mathbb R$ which assigns spacetime interval values to ...
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3answers
85 views

Calibration of a clock [duplicate]

I was inspired by this interesting question on this forum: How do I measure an earth year without a clock? Say you're stranded on an alien planet without any significant tools. How would you ...
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1answer
119 views

How is viscosity related to the forces in fluid?

I think it was that the forces are only perpendicular but do not know how this is related and from where it comes from. EDIT: I am asking for the difference between viscous and non-viscous fluid in ...
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1answer
47 views

Tensor as outer product

This is a problem I am trying to solve and need help with. Given a $ \left( \begin{array}{} 0 \\ 2 \end{array} \right)$ tensor h such that h$(\quad ;A)=\alpha $h$(\quad ;B)$ for any two vectors ...
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0answers
51 views

Finding the momentum of a muon in $\pi\to\mu\nu_\mu$ [closed]

The $\pi$-meson's mass is 139.57 MeV, and it decays into a muon and a neutrino. The muon has a mass of 105.4 5MeV, and a proper lifetime of $2.197 \times 10^{-6}$. The neutrino can be treated as ...
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2answers
74 views

Does relative velocity time dilation occur at any relative velocity?

The reason I ask this question is due to the fact that every example I've found is presented such that the relative velocity is "near the speed if light", or that it happens as the object " approaches ...
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Speed of light in vacuum - definition and Constancy [duplicate]

This question has been nagging me for sometimes now, and even after studying all those relativity still cannot find an appreciable answer. The speed of light is $c$ defined and measured as constant ...
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2answers
72 views

Relativistic spaceships moving towards each other

There are two spaceships, A and B, moving towards each other, such that they will eventually pass each other. At a point equidistant from both ships, their velocities are both 0.5c towards that point. ...
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0answers
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What is the rigorous description of scattering in relativistic QFT?

The first conundrum is what picture of QM to choose, in order to describe such a scattering. Unlike in non-relativistic QM, in RQFT the three all-known pictures are not at all equivalent. The ...
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1answer
122 views

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
89 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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3answers
178 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
171 views

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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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
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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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1answer
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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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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1answer
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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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2answers
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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
153 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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2answers
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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
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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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1answer
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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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1answer
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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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0answers
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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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1answer
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
97 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 $0$ ...
2
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2answers
88 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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1answer
107 views

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
89 views

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
40 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
250 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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1answer
66 views

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
219 views

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 ...