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Questions tagged [special-relativity]

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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Why haven't we yet tried accelerating a space station with people inside to a near light speed?

Is that something we could do if we use ion or nuclear thrusters? Wouldn't people in the station reach 0.99993 speed of light in just ...
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0answers
19 views

Why physical / cosmological models that have been falsified weren't abandoned?

Before anything, I'd like to say that I'm a layman (non physicist) and english is not my main language; I apologize if my choice of words make me sound rude / arrogant, that is not my intent. I often ...
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6answers
787 views

Time dilation and uniform motion

Assume a period of uniform relative motion (no acceleration) of a spaceship in reference frame, B, going 80% of light speed observed from my reference frame, A, when it passes by Earth (my references ...
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0answers
31 views

Pair production problem, how is energy not conserved here?

The problem is asking me to find the minimum photon energy that would produce an electron-positron pair when it collides with a free electron at rest. This is my attempt at trying to conserve both ...
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0answers
16 views

Would Color Confinement apply in higher dimensions?

As I understand it color confinement comes from the fact that as the distance between two color charges increases the color potential energy increases, instead of decreasing, and the energy needed to ...
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1answer
51 views

Does Sagnac effect imply anisotropy of speed of light in this inertial frame of reference?

There seems to be a consensus that the one - way speed of light is anisotropic in a rotating frame of reference (Sagnac Effect). Imagine a rotating ring of infinitely large diameter. In accordance ...
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0answers
43 views

Why isn't there a quantum number associated with the Lorentz boost?

It is a re-post of this question since there is no answer. I am doing problem 3.2 of Schwartz's QFT and figured out all previous questions, where we identified the conserved current of Lorentz ...
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1answer
37 views

What is the energy of a photon reflected off of a moving mirror?

In accordance with the above diagram, a photon with energy $E$ is reflected off of a moving mirror with speed $v$. I think I am supposed to use the conservation of four momentum to find the reflected ...
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1answer
35 views

Boost as a generator of constant acceleration

In Covariant Loop Quantum Gravity by Carlo Rovelli p204, Sec 10.4, there is a paragraph which states ..., a trajectory at constant acceleration is generated by the boost generator $K_z$ in the ...
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1answer
782 views

Time travel future (with calculations)

First, I have seen a few similar questions, but none involved the formulas and calculations I want to find. This is why I do not consider this as a duplicate. I know time travel to the future is ...
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0answers
21 views

Momentum transfer due to Thompson scattering

Sorry to ask here, but I've been stuck with this problem for over a week and I just needed some guidance on how to proceed (since this applies for other types of scattering processes as well). ...
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1answer
225 views

Special *set* of inertial frames in an EM field?

Just looking for confirmation of my understanding of the Wikipedia article on classification of electromagnetic fields: The article states that in the case where $E\cdot B = 0$ and $E^2-B^2 \not= 0$...
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1answer
76 views

Accelerated frame vs gravity frame

Can accelerated frame change curvature of space as gravity does? Can there accelerated frame be pure inertial frame?
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0answers
20 views

Doppler Shift in Michelson-Interferometer

I've used a michelson interferometer with a moveable mirror in order to verify the doppler effect for light waves. But whilst writing the theory for my lab report I encounterd an issue I'm not able to ...
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0answers
28 views

What is the Lenz reaction due to Radial EMF generated by a rotating cylindrical magnet with a steady magnetic field?

Per the top answer to the question "What is the electric field generated by a spinning magnet?", a rotating magnet can generate an electric field even if it does so on its axis of cylindrical-symmetry....
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3answers
134 views

Why is electric field $E^i = E_i$ instead of $E^i = - E_i$?

Let us consider the Minkowski spacetim. Generally, we know that when we lower or raise the index of the convariant or contravairant tensor, we need to use the metric $\eta^{\mu \nu}=\eta_{\mu \nu}=(+,...
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Relativity of Simultaneous Events

I'm used to relativity of simultaneity situations that are like the Einstein lightning train thought experiment. This problem is different. Say an observer on the space station observes lamps 1 and 2 ...
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1answer
46 views

Tangent space of pseudo-Euclidean manifold

My textbook says (without any justification that I can see) that "since Minkowski spacetime is pseudo-Euclidean, the tangent space $T_P$ at any point $P$ coincides with the manifold itself". My ...
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13answers
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“Reality” of length contraction in SR

I was in argument with someone who claims that length contraction is not "real" but only "apparent", that the measurement of a solid rod in its rest reference frame is the "real length" of the rod and ...
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1answer
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How do u get Eq3 from Eq2&Eq1 [on hold]

I keep getting the wrong results by subbing eq1 into eq2 It’s from Kleppner’s an introduction to mechanics 2nd edition
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2answers
214 views

Relationship between mass preserving four-fources and proper acceleration

Background I studied Rindler's book on Relativity. Relevant information from this book is available on-line here: http://www.scholarpedia.org/article/Special_relativity:_mechanics Given that we ...
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0answers
28 views

Question about Relativity and Proper Reference Frames [duplicate]

If your in a space ship moving at relativistic speeds in reference to an observer on Earth, time would have to be going slower on the space ship and faster on Earth. However, wouldn't the Earth be ...
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1answer
36 views

Conservation of Energy and Momentum - Special Relativity

I am confused as to how we can assert that energy and momentum are conserved in special relativity. I was attempting a problem on the elastic collision of two particles and came across this. I have ...
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1answer
373 views

Minkowski metric: Why does it look like it does? [duplicate]

I have been searching for why would we even start with Minkowski spacetime metric as being written as: $$ds^2=-dt^2+dx^2+dy^2+dz^2.$$ No really, so why would we have a negative sign for temporal ...
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5answers
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Does the fact that we can only measure the two-way speed of light undermine the axiom of invariance?

When we measure the speed of light we get the same answer in all directions. This is taken to undermine the aether or absolute motion hypothesis and give support to the proposal that the speed of ...
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5answers
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Relativistic explanation of attraction between two parallel currents

This has been answered a lot of times, and I have been reading about it on many websites, including PSE, but I still don't get it. So please don't mark it as a duplicate unless it really is one. Two ...
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7answers
7k views

According to special relativity, has the future already happened? [closed]

According to special relativity, a photon traveling at the speed of light, does not “experience” time. It is traveling into the future at an infinite rate, right? That would mean that everything that ...
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1answer
36 views

What does the line of constant space time (interval) represent?

In this diagram, what do the hyperbola represent. I understand that for a given hyperbola t^2-(x/c)^2 is constant, but in an answer given to this question: What spacelike, timelike and lightlike ...
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1answer
44 views

Minkowski diagram

I have not well understood the picture of geogebra regarding the angle of time (t') that is inclined compared to (t) of 26.57°angle . In the picture we see that the velocity is setted at 0.5c, for ...
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3answers
198 views

Write electromagnetic field tensor in terms of four-vector potential

How can we know that the electromagnetic tensor $F_{\mu\nu}$ can be written in terms of a four-vector potential $A_{\mu}$ as $F_{\mu \nu} = \partial_{\mu} A_{\nu} - \partial_{\nu} A_{\mu}$? In the ...
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0answers
17 views

A charge moving relativistically in electric field [on hold]

I need help in the following question: At $t=0$ a charged particle is moving at some speed $u$ in the X direction,and enters a constant electric field E in the direction of Y (all measured in lab ...
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2answers
77 views

Lorentz-transformation

I don't understand how to derive the matrix representing the Lorentz-transformation given two systems S and S': $$x' = \Lambda x$$ these transformations do not leave the differences $\Delta x^\mu$ ...
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0answers
23 views

Flux through a ball of a moving relativistic particle [on hold]

I have been struggling with the following question for so long that I decided to give up and ask you, the professionals. It seems that the relativistic idea of the question is not the problem, but the ...
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2answers
542 views

The Meaning of Newton's Second Law of Motion Being Invariant Under Certain Transformations

What do we mean when we say that Newton's Second Law of Motion is invariant under Galilean transformations? Does it mean that the value of a force measured in one reference frame is the same when ...
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1answer
88 views

From relativistic equation to find Dirac matrices

Is this possible and then how? $$((\gamma \otimes \mathbf\sigma)\bullet\mathbf p)(\gamma^\prime\otimes\mathbf 1_2) = \gamma\gamma^\prime\otimes\sigma \bullet \mathbf p $$ where $\gamma$ and $\gamma^\...
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0answers
28 views

How can a vertical beam of light move sideways with an interferometer? [duplicate]

The picture is of the Michelson Morley Interferometer. How can the upward, vertical beam of light move sideways with the interferometer? This brings me to the conclusion that "Aether are attracted ...
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1answer
94 views

Voyager spacecrafts life span and theory of relativity

The Voyager spacecrafts are moving with an approximate constant speed of 16 to 17 km/s. As per Einstein's theory of relativity, time passes more slowly for them compared to us. Then, is it possible ...
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2answers
2k views

Schutz's geometrical 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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1answer
617 views

Relativity and a Rotating Rod

I was doing a problem on relativity and I was thinking about the problem in terms of the postulates of Special Relativity. Special Relativity only considers motion in inertial reference frames and I ...
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0answers
35 views

Antiparticles travelling backward through time [duplicate]

Could someone please explain to me Feynman and Wheeler's theory of waves acting forward and backward in time? I have read about their idea of an antiparticle behaving as a particle travelling ...
2
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1answer
134 views

Proof that 4-potential exists from Gauss-Faraday field equation

This is a problem concerning covariant formulation of electromagnetism. Given $$\partial_{[\alpha} F_{\beta\gamma]}~=~ 0 $$ how does one prove that $F$ can be obtained from a 4-potential $A$ such ...
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3answers
84 views

Four-velocity vector of light

Please note that my question is not a duplicate, it is not about the speed of light, my question is only technical about the four velocity vector for light, its definedeness, value and constantness. ...
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1answer
424 views

Combining two Lorentz boosts

Is it possible to express two Lorentz boosts $A_x(\beta)$ and $A_y(\beta)$ along the x/y-axis as one boost described by $A(\overrightarrow \delta)$? To answer this, I start by defining $\theta \equiv ...
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0answers
29 views

Why can't we rule out other synchronization procedures?

According to what I've read, it is generally regarded that Einstein's choice to have the speed of light equal in every direction is only a convention, and since there is no way to measure the one-way ...
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1answer
77 views

Maximum scattering angle for relativistic elastic collision

In Landau Classical theory of fields, in the section of elastic collision(chapter 2, section 13), he mentions that for $m_1>m_2$, the scattering angle $\theta_i$ cannot exceed a maximum value, and ...
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1answer
60 views

Expression of proper time with light perturbation on Minkowski metric

In my lecture on General relativity, it is said that, by taking the following metric : $$g_{\mu\nu}(x)=\eta_{\mu\nu}+h_{\mu\nu}(x),~ {\rm with}\ h_{\mu\nu}\ll1$$ one has the definition below of ...
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0answers
69 views

Do synchronized clocks retain the same time delta between two inertial frames? [closed]

Let's say we have a device made of a succession of clocks (red squares in the scheme) which are synchronised, in the device inertial reference frame, using Einstein synchronisation. Each clock is ...
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3answers
197 views

Separating the topics of general and special relativity

So, I have managed to confuse myself beyond the point of repair. I am not a physics student, so my physical knowledge is limited. Anyway, there are a few topics of relativity, which I can not seem to ...
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3answers
5k views

Potential energy in Special Relativity

In Special Relativity, the energy of a free particle is $E^2=p^2c^2+m^2c^4$. But what would be the energy when there is potential energy? If it's something like $E=\sqrt{p^2c^2+m^2c^4}+U$, what ...