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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Can one create mass from energy?

Due to $ E =m c^2 $, one can convert mass to energy. A classic example would be matter/anti-matter annihilation to produce energy (photons, etc.). Can one do the reverse? So could one do something to ...
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223 views

Relativistic addition of velocities of spaceships [duplicate]

If Spaceship 1 is traveling at speed $.5c$ relative to Earth, and Spaceship 2 is traveling at speed $.3c$ relative to Earth in the same direction, what does Spaceship 2 see Spaceship 1's speed as? I ...
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188 views

Time dilation in special relativity

Suppose a star ship is moving with some velocity. Two light pulses one in direction similar to star ship another opposite to it is shot towards the space ship. Then how time inside space ship adjust ...
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What does a frame of reference mean in terms of manifolds?

Because of my mathematical background, I've been finding it hard to relate the physics-talk I've been reading, with mathematical objects. In (say special) relativity, we have a Lorentzian manifold, ...
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Breaking the speed of light relative to a moving object [duplicate]

You can't go faster than light, and light can't be additive (if you shine a light from a spaceship, the light is not going $c$+"speed of spaceship", it's just going like it always does). But what ...
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Is the “How to break the speed of light” minute physics video wrong?

I am referring to this video, on YouTube, by minutephysics, which has quite a lot of views. In the video it states that if you flick your wrist while pointing a laser that reaches the moon, that the ...
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1answer
89 views

Why is $\phi$ constant in the hyperbolic Lorentz transforms?

If two spacetime events are separated by $(dx,dy,dz,dt),(dx',dy',dz',dt)$ in two reference frames $K,K'$ respectively, whose relative motion is purely along the $x$-axis, then, purely due to the ...
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2answers
107 views

State of constant motion

Why does an object remains in its state of constant motion if there are no forces acting on that object? My understanding is that all the energy of the motion will be kept inside and a change in the ...
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1answer
57 views

velocity in inertial and nontial frames

I got confused about the difference between the last term of both pictures. In the first one, we have w x r, but in the second we have w x r underlined. Does anyone have a better explanation? They ...
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2answers
73 views

Query into the cumulative velocity of mounted platforms

Consider throwing a stone at an object from rest, it travels at Vms-1. Now throw that stone whilst running at Ums-1. It seems in the latter scenario the total speed of stone is V + U. Now imagine ...
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2answers
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Why is the Faraday Tensor derived from the Lorentz force?

If we start from the Lorentz force, $$\textbf{F}=q\textbf{E} +q\textbf{v}\times\textbf{B}$$ and use the four velocity u$^{\mu}$ and the four momentum p$^{\nu}$, then we get to ...
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1answer
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The scissor paradox: can we pass the information faster than light? [duplicate]

click to view the image Before I start, I want to say that this is not a duplicate of "Is it possible for information to be transmitted faster than light by using a rigid pole?", Since point A is ...
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2answers
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Are signal fronts in a beam not at rest to each other?

I'd like to investigate how the notion of "mutual rest" might be applied consistently, but distinctively, in the following thought experiment: Consider a light source ("$A$") which directs a beam ...
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1answer
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Relativistic Elastic Collision

I am having trouble getting my head around the transfer of energy in a relativistic elastic collision. My understanding of a relativistic elastic collision is one in which the total rest mass on each ...
1
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1answer
96 views

Colliding particles at speeds aproaching c [closed]

(In natural units where $\hbar=c=1$.) Two particles are to be collided. Each of these particles has a rest mass of 0.9 GeV and they will be collided at equal but opposite speeds. What is the minimum ...
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2answers
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Is 2.5x speed of light possible between two objects?

These news are in Finnish: http://www.hs.fi/ulkomaat/Kaukaisin+havaittu+galaksi+et%C3%A4%C3%A4ntyy+maasta+valoa+nopeammin/a1305618680897 The main excerpt is: "Distant galaxy moves away from us as ...
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3answers
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Extended Rigid Bodies in Special Relativity

I was reading Landau & Lifshitz's Classical Theory of Fields and I noticed that they mention that an extended rigid body isn't "relativistically correct". For example, if you consider a rigid ...
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1answer
367 views

Relativistic Doppler effect on gamma rays

I'm trying to solve the following problem : An electron-positron pair annihilates, creating two photons. At what speed must an observer move along the line of the photons in order that the ...
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1answer
51 views

Taking signal travel time into account in Special Relativity

I am having problems taking the time it takes for a light signal from an event to reach an observer into account: For instance, if we have two observers $A$ and $B$ who synchronize their clocks when ...
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2answers
122 views

Is speed of light ( Sun-to-Earth ) related to the movement speed of solar system?

The speed of light has been measured to be 299 792 458 m/s. Now, the Solar System is traveling at an average speed of 828,000 km/h (230 000 m/s). Summing up the numbers we get close to 300 000 000 m/s ...
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1answer
192 views

Learning the stress-energy tensor

I am learning dynamics in special relativity and come across the stress-energy tensor. I have real trouble understanding it. I would love answers on How to motivate the definition of this tensor. ...
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160 views

Magnetism due to relativity?

So I have been reading in some books that magnetism does not have to be assumed a priori, but can be obtained from the electric field + special relativity. And I have seen how this leads to the common ...
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What happens when relativistic effects stop?

I'm currently learning special relativity in high school and we only primarily deal with what happens when an object is moving at constant relativistic speeds. But what if the object slowed back down ...
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1answer
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Non-relativistic limit in a Lagrangian density

What criteria should I consider when determining the non-relativistic limit of a Lagrangian density? For example, how would I take the non-relativistic limit of the following Lagrangian density: ...
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1answer
132 views

In Minkowski space, why does the hyperboloid appear to each observer as a circle whose radius is increasing faster than the speed of light?

I read the assumption in the above question in the paper Hyperbolic geometry on a Hyperboloid by William F. Reynolds (see here, page 444), but it was not clarified further (the discussion was rather ...
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Are there 'special' cases for when special relativity can be applied for accelerating bodies?

I have the following theoretical situation: A space station modeled as a ring in free space is rotating about its centre point at a high speed. I am trying to work out where time flows slower. From ...
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367 views

Homogeneity of space implies linearity of Lorentz transformations

In the derivation of Lorentz transformations, the Wikipedia article mentions a couple of times that the linearity comes from the homogeneity of space. I am looking for a thorough explanation on this. ...
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How can photons interact with anything?

I read photons do not age because they move at the speed of light. So when a photon interacts with my eyes, aren't they apart in space-time by the difference of the time in the frame of reference of ...
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Relativistic momentum finding

Kinetic energy of an object $mc^2$. I want to evaluate the momentum. We know Kinetic energy, $$E_k = \frac{p^2}{2m}$$ $$mc^2 = \frac{p^2}{2m}$$ $$ p = \sqrt{2}mc$$ Note that the momentum is the ...
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174 views

Units in time dilation calculation

I am currently working through Brian Greene's "World Science U" course on special relativity, and I have a question regarding one of the calculations performed for an exercise on time dilation (MODULE ...
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1answer
953 views

Mandelstam variable equality derivation for $s$-channel process

I am supposed to show that the Mandelstam variable $s=(p_1^2 + p_2^2) = 4(P_{cm}^2 + m^2)$ for an electron/positron interaction, where $p_1$ is the incident 4-momentum of the electron and $p_2$ is ...
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How did the scientific community receive Einstein's theories when he published them? [closed]

By now, we have had multiple indications through observations and experiments that Einstein's theories on general and special relativity are correct. We recently had our second observation of ...
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1answer
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In space I am moving wrt to what?

Let us suppose I am running on a street. When my eyes are open, I can see many things moving backward, and thus it gives me an idea that I am moving wrt those things. Not even this, even if I close my ...
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Time dilation formula and example

What is the time dilation formula by constant velocity? Is the right formula $$t'=t\times \sqrt{1-v^2/c^2}$$ or is it $$t'=\frac{t}{\sqrt{1-v^2/c^2}}$$ ? And can someone show me a computational ...
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If a photon is a boson and has spin 1, shouldn't it have 3 spin orientations since spin 1 is a triplet? [duplicate]

I've gotten used to the fact that a spin can be described by its total spin and its $z$-component. And I've learned that a particle (really, anything) with spin 1 forms a triplet with three possible ...
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1answer
80 views

Observers in Special Relativity

Suppose I am an observer in Minkowski space, observing a particle traveling with a constant velocity $v$. If I want to calculate the particle's Lorentz factor, given that the particle is traveling at ...
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Is there a fourth component to the electric field and magnetic field?

The Question If the three vector electric and magnetic fields come from the four component four-potential, then is there a fourth component to the electric and magnetic field? Related Question I ...
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Do particles have different spins in different frames of reference?

Let's say we have two photons, whose momentum vectors point to opposite directions. Also spin angular momentum vectors of the photons point to opposite directions. (Sum of spins is zero) Now we ...
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1answer
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What is the formula for determining time dilation (as the object in motion)? [duplicate]

The formula for calculating how much time passes for a still observer is T=TO/(1-v^2/c^2)^1/2. How do I calculate what TO is?
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Derivation of the general Lorentz transformation

The standard Lorentz transformation or boost with velocity $u$ is given by $$\left(\begin{matrix} ct \\ x \\ y \\ z \end{matrix}\right) = \left(\begin{matrix} \gamma & \gamma u/c & 0 & 0 ...
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Weird case for relative velocities and special relativity

This has bothered me for a while. I've been taught that the formula for determining the perceived velocity on an object from another moving object's reference frame under special relativity is: $$v = ...
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Including special relativistic effects in momentum in Heisenberg's Uncertainty Principle

I've been told that an electron is somewhere within the space of $10^{-10}m$ and am supposed to find the uncertainty in its velocity. Simply applying $m\Delta x \Delta v \geq \frac{h}{4\pi}$ results ...
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1answer
299 views

What is the role of the speed of light in mass-energy equivalency? [duplicate]

Where does $c$ squared come into play in the equation $E=mc^2$. Multiplication obviously but how does energy equal mass times the speed of light?
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Can a revolving body self-gravitate?

If a body is revolving around a point at radius R with tangential velocity V, does General Relativity predict that at some tangential speed, the body will revolve around the point without any external ...
2
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1answer
145 views

All possible electromagnetic Lorentz invariants that can be built into the electromagnetic Lagrangian?

Given the electromagnetic Lagrangian density $$ \mathcal{L}~=~-\frac{1}{4}F_{\mu\nu}F^{\mu\nu}~=~\frac{1}{2}(E^2-B^2) $$ is a Lorentz invariant, how many other electromagnetic invariants exists that ...
3
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1answer
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Special relativity: how to prove that $g = L^t g L$?

We have $$X^\textrm{t}gX = 0 \iff X^\textrm{t}L^\textrm{t}gLX = 0,$$ where $X$ is a column vector of length four, $L$ is a non-singular $4 \times 4$ matrix, 't' denotes matrix transpose, and $$g = ...
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1answer
184 views

Does the light speed change in media? [duplicate]

Does the light speed change? The Theory of Relativity says that the speed of light in vacuum is the same and unchangeable, while I read that the speed of light in glass is lower than in air, and that ...
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1answer
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What happens if a body free-falls at a certain speed?

It is known that a body falling to the ground is affected by gravity, and its velocity increases by 9.8 m/s per second. But when this body is falling, and it reaches the speed of 340 m/s (the speed of ...
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Breaking the simultaneity

I have expressed my self in a detailed way. I've labeled the points to which I want an answer. I have doubt in the Einstein's rail experiments which he mentioned in his book. In this experiment ...
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2answers
628 views

Criticism of the Thomas precession literature

From an earlier version of the Wikipedia article on Thomas precession concerning TP and LP=Larmor precession, regarding the paper: G B Malykin, "Thomas precession: correct and incorrect solutions", ...