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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Paradox in special relativity

Yesterday we started relativity on our physics class, and my professor taught us a few concepts. We did some examples on how things changed by looking them from different reference systems, and a ...
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2answers
61 views

Transition from 4-potential to E and B

In my lecture notes there is a step that i cannot follow: $$\frac{i}{2}[\gamma^{\mu},\gamma^{\nu}] (\partial_{\mu}A_{\nu}-\partial_{\nu}A_{\mu})=: \sigma^{\mu\nu}F_{\mu\nu}=i\vec{\alpha} ...
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57 views

Does sending current upwards reduce the voltage?

I was thinking about relativistic situation of having a vertical wire on a neutron star or high-gravity environment and then say if I send current upwards (away from the ground) will the voltage be ...
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0answers
23 views

p-adic and quantum mechanics [duplicate]

In physics we call integer based quantity as “quantization”, so you have energy, momentum etc taking quantized values. But in math, this kind of situation is really the age old problem of number ...
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4answers
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Will 1 gram of matter moving at relativistic speeds completely annihilate a larger quantity of stationary antimatter?

This is a question about the relativistic mass concept which I am having trouble understanding, mainly because of the scenario below. Simple scenario: Suppose 1 gram of matter is accelerated to 99% ...
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2answers
43 views

Rapidity and the momentum 4-vector

I'm having trouble making a conceptual leap in the Lorentz transformation of the energy-momentum 4-vector: The 4-vector in $S$ is related to $S'$ by, $$ \left( \begin{matrix} E' \\ p'_{x} ...
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2answers
74 views

Is time dilation based on the formula for period of a pendulum?

The theory Albert Einstein put forward about special relativity mentions a possibility for time dilation, in which he states gravity has a considerable effect on time. And in high school physics we ...
3
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3answers
83 views

Rotation in the x-t plane

I am currently studying special relativity using tensors. My lecture notes (which happen to be publicly accessible, see top of page 99) say that the standard configuration can be viewed as a rotation ...
2
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1answer
60 views

Does time really differs drastically?

As I heard/read time moves slower and slower for me as I speed up, but does it change drastically? Our current formulas say, If I go at a speed very close to light's, time almost stops. I've seen ...
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1answer
66 views

What is the meaning or purpose of inertial motions

It seems to me that, except for light, inertial motion is never possible in real world where there is gravity everywhere. It is at best some kind of idealization. But why inertial motions are so ...
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0answers
49 views

Can we make a particle travel faster than $c$ in this way? [duplicate]

In my sixth grade science class our teacher asked us, for homework, if it was possible to have anything travel faster than light. Thinking about this, I came up with a rough idea of a way to make ...
0
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0answers
28 views

Energy - Momentum relation summing of vectors - Relativity [on hold]

"A body of rest mass m0 moving at speed v approaches an identical body at rest. Find V , the speed of a frame in which the total momentum is zero." Does the energy- momentum relation (E^2 = p^2c^2 + ...
4
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1answer
42 views

Do 2-body elliptic orbits precess in special relativity?

Einstein famously explained the anomalous precession of Mercury by showing that in general relativity elliptic orbits precess even in the 2-body problem. But apparently in the early days of quantum ...
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0answers
43 views

Electrostatics and relativity [closed]

How to get the "d‘Alembertian acting on four vector A=-four vector j" from Poission's electric static equation by Lorentz transformation?
0
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1answer
48 views

Is there a spacelike curve connection two events in Minkowski space?

Assume two events in Minkowski Space (signature $(-,+,+,+)$) $p_1$ and $p_2$. One claims that there is a spacelike curve which connects these two points in Minkowski space. I have some trouble to ...
4
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3answers
120 views

Is it true that all particles that have a speed less than the speed of light must also have mass?

I've previously learned that massive particles cannot achieve the speed of light. But recently I read that, concerning the gels that refract and bounce light within around enough that it can travel ...
2
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1answer
29 views

Force on a moving charge in relative frame

Consider a particle of charge $q$ moving at velocity, $v$, enters a magnetic field $B$ which is perpendicular to its motion. Now consider two observers, one stationary and the other moving at the ...
2
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3answers
448 views

What is a body's momentum really equal to?

I know a body's momentum is equal to the product of its velocity and mass. But what kind of mass? Relativistic mass or rest mass?
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0answers
28 views

How to add together non-parallel rapidities?

How to add together non-parallel rapidities? The Lorentz transformation is essentially a hyperbolic rotation, which rotation can be described by a hyperbolic angle, which is called the rapidity. I ...
4
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1answer
71 views

General construction of equations of motion for free particles

I've got a question regarding the different Symmetrie-Lie-Groups of Newtonian Mechanics and special realtivity. Is there a canonical way to obtain the equations of motion for a free particle only by ...
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0answers
65 views

Lagrangian, geodesics and relativity [closed]

My background is in maths, but I have been studying some basic physics with occasional input from a friend who is studying for a physics PhD. Due to my background, I am keen to visualize things ...
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0answers
29 views

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 ...
0
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1answer
46 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 ...
2
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1answer
26 views

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
32 views

Is there serious research on superluminal travel? [closed]

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?
2
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1answer
54 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
4
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2answers
90 views

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 ...
0
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1answer
25 views

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 ...
2
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1answer
77 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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1answer
50 views

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 ...
2
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2answers
107 views

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
51 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 ...
7
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2answers
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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 ...
0
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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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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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40 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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2answers
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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 ...
2
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2answers
117 views

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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0answers
30 views

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 ...
0
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1answer
46 views

Lorentz invariance vs. covariance

I am a bit confused whether relativistic theory is Lorentz invariant or covariant. And please explain why?
2
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1answer
51 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 ...
0
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1answer
50 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 ...
0
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1answer
21 views

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) ...
1
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1answer
55 views

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} ...
2
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2answers
159 views

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 ...
0
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1answer
38 views

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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1answer
68 views

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 ...
4
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2answers
240 views

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 ...
0
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4answers
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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 ...
0
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1answer
50 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 ...