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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Is Twin Paradox solved in Special Relativity or General Relativity? [duplicate]

I'm getting pretty frustrated about finding the true solution to the Twin Paradox. If I open 10 relativity books, they all tell that they have the correct solution and the other books are wrong. So I ...
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35 views

How to determine which object in a special relativity physics problem has proper time?

I'm having some difficulty determining which object/location should have proper time applied to it in relativity physics problems. Example: If an electron travels at 40% the speed of light then ...
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1answer
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Polarization of light for a fast moving observer

For a fast moving observer the frequency of light becomes shifted due to the (relativistic) Doppler effect. But what about the polarization of the light? Could it be, that e.g. circular polarized ...
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1answer
27 views

Is there serious research on superluminal travel? [on hold]

I was wondering if there are any serious attempts, or any ideas for loopholes in the current theories, that would enable us humans to travel with a speed greater than the speed of light?
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42 views

Is there a time dilation between my left and right arms?

Is there a time dilation between my left and right arms when walking? due to special relativity I guess Thanks
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where is the logical hole in this reasoning? (special relativity)

I cannot see the problem in the following reasoning, so I'd be glad if you could help me out. The problem is defining a notion of "length" that is consistent with the constancy of the speed of light ...
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Perpendicular doppler effect photons

If I have a photon with frequency f in the lab frame and the observe it in a inertial frame moving perpendicular to the photon. The direction of the velocity of the photon must change but does this ...
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1answer
69 views

Massless particle that have momentum not equal to 0

I saw some problems in special relativity that use conservation of total energy and momentum and the conclusions are spectacular. My problem is the following: how can a massless particle like neutrino ...
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Space Contraction [duplicate]

Is there any experimental evidence of space contraction which theory of spacial relativity predicts? You should bear in mind that GPS & muon detection beyond the distance permitted by its half ...
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1answer
35 views

special theory of relativity-time dilation [on hold]

What is actual mathematical relation for time dilation?Is the time recorded by th moving frame greater than time recorded by stationary frame or is it opposite..? tell me answer.....
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Does time dilation imply that events do not take place?

I take two mirrors parallel and facing each other. A light pulse is being infinitely reflected between the two mirrors $M_1,M_2$. $E_1,E_2$ are the events when the pulse is reflected by $M_1,M_2$, ...
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1answer
36 views

Can we travel faster than the speed of light? [duplicate]

So my question is completely a theoritical question. For example i have a stick made of the strongest material and lightest material and its lenght is as long as the solar system's diameter. The end ...
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Is Einstein's characterization of “time” as “the position of the little hand of my watch” definitive and binding in the RT?

In Einstein's very first publication dealing with the Theory of Relativity, effectively as a preamble to all subsequent thought-experimental considerations and descriptions, Einsteín put the ...
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Fraction of kinetic energy carried by neutrons after D-T fusion [on hold]

I am trying to answer the following question: Ignoring the initial kinetic energy and momentum of both particles in a D-T fusion reaction calculate the fraction of the released kinetic energy ...
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1answer
42 views

Tachyons and the light barrier

I read somewhere that if something breaks the light barrier, i.e. a tachyon, that it will take infinite energy to make it go slower than the speed of light. So, does that mean that the object will ...
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29 views

Why direction of Light is considered perpendicular to the motion of the objects in S.Relativity Equations? [on hold]

When I look at Special Relativity Equations(Time Dilation/ Length Contraction), I see the direction of light is considered perpendicular to the motion of the object and then the Pythagoras theorem is ...
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35 views

Clock ticks slower [closed]

Why does our clock tick slower in a deep gravitational well or when we travel at near the light speeds?Why is it said(theoretically) that we will be able to go backwards in time when we travel at ...
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16 views

At the speed of light [duplicate]

Is it possible to accelerate a body to the speed of light?Why is is said that at the speed of light,the mass of a body would be converted to energy?
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41 views

Special relativity : time dilatation [on hold]

A space shuttle is flies away from the earth with $v=0.8c$ . When it has reached a distance of $d=6.66\cdot 10^{11}m $, a light flash is sent from the earth. How long does the signal need to reach ...
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1answer
60 views

Derivation of lorentz transforms relativity - Problem understanding one step [on hold]

Hi, I'm confused about how to move from the third equation to the fourth equation. Why do we need to substitute every term in? That is, why would ct' = (gamma)(x-vt) be wrong? Thanks in ...
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39 views

The Lie algebra of the Lorentz group is $su(2) \oplus su(2)$. Is there a similar relation for the algebra of the Poincare group?

It can be shown easily, by introducing new generators from the usual ones that we can think of the Lie algebra of the Lorentz group as being built up by two copies of the $SU(2)$ Lie algebra: $$ ...
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What would happen if a space ship may travel as quickly as the speed of light? [closed]

Ofcouse, it is impossible. Beacuse of need of infinite energy to accelarate infinite mass... Bur if it might be possible...??? I did a fictional study as an amateur. I shared it, but i need feedback ...
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21 views

Clocks in moving inertial frames [closed]

A clock $C$ is at rest at the spatial origin of an inertial frame $S$. A second clock $C'$ is at rest at the spatial origin of an inertial frame $S'$ moving with constant speed $u$ relative to $S$. ...
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Is it possible to travel ONLY through Time and not Space? [closed]

The question is as stated above. I although think, the most probable answer is no, but I really want to know the reason to it. If, One can travel through only space by travelling at the speed of ...
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2answers
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What would a nuclear explosion look like at relativistic speeds where time dilation and length contraction become significant?

Suppose a rocket carrying a nuclear weapon is moving past our planet at very near the speed of light while a stationary observer watches from here on Earth. As the rocket passes directly overhead, an ...
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Hydrogen atom Ionization by Magnetic Field [closed]

The source of a magnetic field (it could be a magnetic dipole) is moving at relativistic speed. This magnetic field encounters a hydrogen atom at rest with respect to the source. Will this encounter ...
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1answer
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Lorentz invariance vs. covariance

I am a bit confused whether relativistic theory is Lorentz invariant or covariant. And please explain why?
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49 views

Time changing potential gives rise to “force”?

Imagine a charged particle inside a Faraday cage (i.e. charge on outside, zero electric field inside, but non-zero electric potential on the inside). Suppose the charge distributed on the outside of ...
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48 views

How length contraction will work in this case?

Observer is in a spaceship XYZ. In front of him a rod AB is travelling at velocity V. Attached to the 2 ends of the rod are light sources(Red and Green) at different heights. Now these 2 sources emit ...
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Poynting vector from 1st term in Lienard-Wiechert field

I start with 1st (non-radiative) term from Lienard-Wiechert fields: $$ \vec{E} = q (1-v^2) \frac{\vec{R_{t'}} - \vec{v}R_{t'}}{(R_{t'} - \vec{v}\vec{R_{t'}})^3} $$ $$ \vec{H} = - q (1-v^2) ...
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Indices of a Pauli matrix transformed in the Lorentz representation

When Peskin and Schroeder want to prove a Fierz identity on page 51, they make use of the identity $$(\sigma^{\mu})_{\alpha \beta} (\sigma_{\mu})_{\gamma\delta} = 2 \epsilon_{\alpha \gamma} ...
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2answers
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What exactly is meant by saying that two events had been “simultaneous in an inertial frame”?

In order to address my question based on a concrete example setup let the following two separate events be given: participants $A$ and $J$ encountering each other in passing (additional participants ...
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What's the phenomenon where it looks like more particles exist at relativistic speeds?

From the perspective of an observer moving close to the speed of light, the surrounding environment has very high energy which leads to pair production. What is the name of this phenomenon? I can't ...
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4-momentum of massless photons

The time component of a particle's 4-momentum is $$ E'=\frac{E-up}{\sqrt{1-u^2/c^2}}\tag{1} $$ Now suppose it is photons that you are observing from a system moving at $u$ on a line towards ...
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Maxwell's equations invariant under all linear transformations?

Maxwell's equations in tensor notation read: \begin{align} \partial_\mu F^{\mu\nu} &= J^\nu \\ \partial_{[\lambda}F_{\mu\nu]} &= 0 \end{align} Consider doing a general coordinate ...
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What is the proper time interval for simultaneous events?

Let us take a rod of length L and the two ends A and B have two photon guns. A----------------------B Let the end A fire a pulse (event ...
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1answer
49 views

Relativistic Momentum in One Frame

(I) What is the momentum of a proton traveling at v = 0.75c? This problem requires a simple substitution. Using the equation $\ p_{rel} = m*u * (1/\sqrt(1 - v^2/c^2))$, where $v$ is the speed of a ...
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Is there any evidence for the increase of mass due to time dilation also causing a strengthening in said mass' gravity? [duplicate]

Logically it make sense that gravity would strengthen with an increase of mass but I want to know if there is evidence for this.
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Derivation of four-velocity using proper time?

Let us say we have an accelerating particle. 4-velocity is given by the derivative of 4-position with respect to proper time. Derivations that I have seen say that: $$d\tau=\frac{dt}{\gamma}$$ But why ...
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Electric fields and magnetic fields [closed]

I would love to know if this is roughly correct with regards magnetic fields. I recently heard someone say that there are people still looking for monopoles. I said I don't think that can be true as ...
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51 views

Lorentz contraction in continuously accelerating rod

I was having a little thought experiment about Lorentz contraction, and I couldn't really figure out what would actually happen. Note that I'm not looking for a answer 'this effect is barely ...
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Causality principle and Entropy (Second Law)

I was reading about the light cone in relativity and I got to the point where in order to avoid paradoxes one can introduce the causality principle: Causality Principle: For every inertial ...
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1answer
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Matrix dimensions in the spacetime interval equation don't seem to agree? (Possible notation misunderstanding)

The spacetime interval in flat space can be expressed as $(\Delta s)^2 = g_{\alpha \beta} \Delta x^\alpha \Delta x^\beta$. I understand covariant, $x_a$, and contravariant, $x^a$, vectors to be row ...
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Is (rest) mass conserved in special relativity?

I don't understand why it is said that the (rest) mass of a system is not conserved in relativity. I mean, the momentum of a system is conserved (i.e.: it remains constant in a frame of reference ...
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In special relativity, is it correct to say the speed of a body B relative to A is the same as measured by every observer?

Here, two objects A and B are moving relative to each other. I use the Einstein velocity addition formula $v = {v_1 + v_2\over 1 + {v_1 v_2\over c^2}}$ to calculate the relative speed between A and ...
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46 views

Dimensionless numbers in relativistic theory

Dimensionless numbers allow physicists and engineers to extend the physical modeling landscape by reducing otherwise complex mathematics to a simple proportional relationship. For example by assuming ...
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Proof that spacetime interval is invariant

I'm trying to understand the proof that spacetime interval is invariant under for any two inertial observers. I know it's easy to arrive at the result using Lorentz transformation but I'm trying to ...
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Relativistic Momentum and Energy - Lorentz Transformations [closed]

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab is colliding fully ionized gold (Au) nuclei accelerated to an energy of 200 GeV per nucleon. Each Au Nucleus contains 197 ...
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A spin on relativity's twin paradox?

What if a twin is in a rocket in a synchronous orbit with the equator of the Earth while the second twin is standing at the equator watching his twin in space. If we use 0.87c for ease of calculation ...
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Theory of relativity. Relative to what? [duplicate]

If I properly understand relativity, time ticks faster for an object sitting still than for an object passing by. So, in a universe with only two objects which have the same "age", object A is ...