Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
2answers
88 views

Finding the expression for probability density (the Klein Gordon equation)

Source: Quantum Field Theory for the Gifted Amateur by Tom Lancaster, Stephen J. Blundell. I am struggling to understand the logical step from the outline of the 'proof' in the footnote, to the fact ...
-1
votes
1answer
45 views

What does the photon feel when it hits an asteroid on its path to earth [duplicate]

If a photon was approaching earth, after 1 minute(from earths reference frame) an asteroid comes on the photons path. And it hits the asteroid, but from the photons reference frame time doesn't pass ...
-1
votes
0answers
17 views

What's a good book about tensors? Also when to learn special relativity using tensors? [duplicate]

I've tried learning basic tensor calculus (transformation law, inner & outer products, adding , etc..) and I could 'work' with the math with no problem, but sometimes I couldn't quite understand ...
0
votes
1answer
49 views

Deriving Doppler effect in observer's frame

I am attempting to find the Doppler factor from the frame of the observer. In the frame of the observer, the source is moving at velocity $v$ towards the observer. Since the source emits at time ...
1
vote
0answers
72 views

Books, papers, etc on Lorentz and Poincare groups/algebras/etc

I'm currently trying to learn more about the Lorentz- and Poincare Lie-algebras and the representation theory about them. But I'm really struggling with the material that we were given and I'm also ...
-2
votes
0answers
50 views

Pole in the barn paradox [duplicate]

I was reading Schutz relativity when I came across the barn-pole paradox. I have seen many videos and explanations on the internet including Minkowski diagrams but I don't seem to understand it enough ...
1
vote
1answer
57 views

Energy and mass at absolute zero temperature

Hi my question is if the temperature of a particle is reduced to absolute zero the that particle has lost its energy so it has no movement. Particles have mass and Einstein said mass equates to energy....
0
votes
1answer
74 views

Duration of a accelerated movement in special relativity

Consider a point $P$ which does the following (one dimensional) movement: Uniform acceleration $a_0$ (proper aceleration) from $t=0$ to $t=T$ (time measured in lab's frame). Uniform deceleration $a_0$...
1
vote
2answers
70 views

What does $U^{-1}(\Lambda)\phi(\Lambda y) U(\Lambda) = \phi(y)$ physically mean?

In QFT, let $U(\Lambda)$ denote a unitary representation of the Lorentz group. Let $\phi(x^{\mu})$ be scalar field operators in the Hilbert space; in other words: $$U^{-1}(\Lambda)\phi(x^{\mu}) U(\...
1
vote
0answers
55 views

Why do like charges repel in a spin-1 gauge theory, while they attract in spin-2 theories?

A presenter recently said this at a colloquium, but they didnt explain why. I know a fair bit of GR and Yang-Mills theory, so dont shy away from the details (unless they are cumbersome and don't aid ...
1
vote
0answers
51 views

Elasticity, clocks, and rate of chemical reactions in special relativity

This is a true or false question. I think I heard this idea somewhere. But first, I need to describe the context. Consider two electrons that are traveling side-by-side at a constant speed in a ...
0
votes
2answers
87 views

How does 4-vector notation work?

In particle physics we are going over 4-vector notation. However, my background on this is a little shaky, and I'm having difficulty differentiating the notation and visualizing what it actually means....
0
votes
0answers
93 views

Relativistic weight of a bouncing ball

I was thinking about the mass–energy equivalence, which means that for example a hot gas weighs more than a cold gas and I tried to imagine that microscopically. Lets imagine a gas in a chamber on a ...
2
votes
2answers
84 views

Can the magnetic field *always* be transformed away?

In the book, "Einstein's General Theory of Relativity..." by Øyvind Grøn and Sigbjorn Hervik, the following statement is made: "The Lagrangian density of an electromagnetic field is the energy-scalar ...
0
votes
1answer
45 views

Do Events Conditional to Simultaneity Occur in Every Reference Frame?

Imagine a train with a table that contains a light on both ends (so that the line between the two sources of light is parallel with the line of motion of the train) and a light sensor in the perfect ...
-4
votes
0answers
43 views

Violation of Einstein's speed of light postulate? [duplicate]

Consider the following scenario. You are moving towards the left with velocity c (Speed of light) and your friend is moving to the right with velocity c as well. Now the relative velocity of your ...
1
vote
1answer
68 views

Einstein's Simultaneous Lighning and the Lorentz Transformation

I am reading Einstein's book, "Relativity: the Special and General Theory" translated by Robert W. Lawson, and I have some questions concerning Special Relativity -- specifically, the thought ...
1
vote
2answers
66 views

Relativistic effects on charge

Does charge of the body gets affected by relativity or is constant in all frames of references?
1
vote
0answers
33 views

The Electro-Dynamics of Moving Bodies

In his original paper ''On the Electro-Dynamics of Moving Bodies'', in presenting the case of a rod AB moving with velocity v in a stationary system or frame K, Einstein states that the time interval ...
2
votes
3answers
89 views

Mass of potential gravity energy?

Assume a system where there only two 1 kg solid iron balls floating in space. The two balls are touching each other, so the potential gravitational energy between them is 0. Now I move them 1000 m ...
0
votes
1answer
61 views

Retarded time and corresponding position

EDIT: Added Clarification. By various methods, it's possible to determine that in the formula for Electric potential for the position of a charge in uniform motion, $V=\frac{q}{4\pi\epsilon_0\kappa \...
0
votes
1answer
46 views

Effect of non-zero photon rest mass in optics

If photon has nonzero rest mass, I have inferred that the gauge invariance is broken and the Maxwell's equations change and Klein–Gordon equation comes into picture. What is its effect in optics such ...
1
vote
1answer
30 views

Pion decaying energy

The question is: A pion decays into a muon and a neutrino (which is almost massless, so we’ll take it to have a mass of zero). If the pion is initially at rest, find the energy of the outgoing ...
4
votes
2answers
60 views

Are representations of $\text{SL}(2,\mathbb{C})$ indexed by one half-integer or two?

I am very confused by this. In Hall's book on Lie theory, he states that the representations of $\text{sl}(2,\mathbb{C})$ are indexed by a half-integer. This is the usual result for $\text{su}(2)$ in ...
3
votes
1answer
127 views

Why there's a Lorentz inner product in the unitary representations of the translation group?

Consider Minkowski spacetime. Its translation group is just the additive group $\mathbb{R}^4$. This is an abelian locally compact group. Next, consider one unitary representation $T : \mathbb{R}^4\to ...
-2
votes
3answers
113 views

How to differentiate permanent age difference in the twin paradox from reciprocal time dilation? [duplicate]

I'm hereby editing my previous question about the cause of permanent age difference in the twin paradox example as a result of the links I've been given as answers to my original question. I am trying ...
4
votes
2answers
101 views

Deriving special relativity free particle Lagrangian using infinitesimal boost?

At the very beginning of Landau and Lifshitz Mechanics they derive the form of the Lagrangian for a free particle in Newtonian mechanics. I want to see how to do the analogous derivation in special ...
2
votes
3answers
102 views

Is $E=mc^2$ only partially true? [duplicate]

I've obviously seen that $E=mc^2$. But I've also seen that the equation $E^2=(mc^2)^2+(pc)^2$ (where $p$ = momentum) is true. If you square $E=mc^2$, and subtract the result from the other equation, ...
1
vote
1answer
45 views

Biological aging interval equals Proper Time interval?

In special relativity does proper time interval equal biological aging interval in every inertial reference frame?
0
votes
3answers
106 views

Time's ticking slower vs. fewer events' occurring [closed]

In modern physics, or at least its non-mathematical version for laymen, we hear of time's "going slower" or "faster." In the rocket experiment for the Twin Paradox, for example, time "went slower" ...
1
vote
3answers
89 views

Derivation of Inverse Lorentz Transformation in Index Notation

To review my special relativity I tried to work out the inverse lorentz transformation explicitly. This led to a lot of confusion; I would like to ask what the issue was with the assumptions I made in ...
-1
votes
0answers
29 views

Twin Paradox without any third object [duplicate]

ADDENDUM For anyone that ends up here: see these other posts for suitably non-technical answers. Why does only one twin travel in the twin paradox? Twins paradox question ORIGINAL POST The ...
-3
votes
3answers
103 views

Rest mass of the photon [closed]

Why is the rest mass of the photon is taken to be zero? If rest mass of the photon is non zero, then it leads to infinite energy of the photon (by $E=mc^2$ equation) and there is a violation of ...
-2
votes
1answer
47 views

Can we differentiate Einstein mass-energy relation $E=mc^2$ with respect to position $x$ to get force?

The question is as the title. Can we differentiate Einstein mass-energy relation $E=mc^2$ with respect to position $x$ to get force? I don't know whether my question is valid and logical but just ...
0
votes
0answers
31 views

Charged particle moving perpendicular to the wire. Lenght contraction and Lorentz force

We can easy imagine intuitively lenght contraction when particle is moving parallel to the electric wire which result is increas density of charges. But what force affects on particle, which moves ...
0
votes
1answer
42 views

Change of frame in a uniform magnetic field using relativity

Let's say a charged particle is at rest in a uniform magnetic field. Now if we change our frame of reference the particle appears moving. Now according to classical physics the particle should move in ...
1
vote
3answers
62 views

Method to observe clocks on spaceships moving near $c$?

I have read the explanation for clocks slowing down on a spaceship moving relative to a stationary observer -- something like a beam of light between two mirrors taking longer for the observer to ...
6
votes
1answer
124 views

Can we measure the speed of light in one direction?

I'm sorry if this is a dumb question. Recently I was learning that it's impossible for us to measure the speed of light in one direction. We can only measure it in two directions and we assume that it'...
2
votes
1answer
44 views

If electron drift is slow how can magnetism be a product of length contraction in special relativity?

I've been told both are true, but it confuses me on what is actually happening and what is carrying charge in the wire itself. Length contraction would be almost nothing at the speeds at which ...
0
votes
1answer
24 views

If we shoot to photons to a surface, in which conditions we can differentiate the points where the photons collided with the surface?

Now, I heard this example from one of my professor 4 years ago when I first entered university, and at that I had some objections (and I still do), because, I think, if we flick our wrist fast enough, ...
0
votes
1answer
41 views

Centre of mass collision

A proton with momentum 3 GeV in LAB frame of reference is difussed elastically by a stationary proton. The angle of diffusion of one of the protons, in the CM system is 10º, corresponding to a moment ...
0
votes
0answers
16 views

When a charge starts moving, does it's electric field change into magnetic field? [duplicate]

If the electric field does change into magnetic field, how does it happen? And if it doesn't happen, then what happens to the electric field?
1
vote
1answer
65 views

Time component of momentum four-vector

In Landau-Lifshitz, Classical theory of fields (second chapter), the four-momentum is defined by the equation $$-\frac{\partial S}{\partial x^i}=p_i\tag{9.12},$$ where $S$ is the action integral. The ...
-2
votes
2answers
64 views

Relativity from a basic assumption

Is it possible to derive Lorentz transformations just by assuming that if two spaceships are moving away from each other with a constant speed, it is impossible for them to tell who is moving, even if ...
-4
votes
1answer
34 views

Looking back in past [closed]

Can faster than light communication give us the ability to see in the past, that is to say, if we can imagine a ultra huge highly advance telescope 60 light minutes away from earth and we want to look ...
0
votes
0answers
36 views

Equivalence in all inertial frames

Suppose there is a train moving to the right. and inside the train there is an observer, A. Outside the track, there is another observer B. When the train passes in front of B, right at the instant ...
0
votes
0answers
27 views

Constant acceleration space travel: velocity relative to the Earth? [duplicate]

Suppose we are in a spacecraft that is moving away from the Earth along a straight line with a constant acceleration of $1G$, and that this acceleration can be sustained indefinitely. Accelerating at ...
0
votes
0answers
67 views

How can we justify time dilation if we look through an spyglass at Einstein's light clock?

Assume that a space shuttle travels in a circular path having a radius $r_s$ at a tangential speed $v_s$ - a considerable fraction of the speed of light. There is a light clock inside the shuttle ...
15
votes
1answer
257 views

What is the spin-statistics theorem in higher dimensions?

In $d = 3+1$ dimensions, the spin-statistics theorem states that fermionic particles have half-integer spin and bosonic particles have integer spin, in a well-behaved relativistic quantum field theory....
-5
votes
1answer
59 views

When we burn a match stick it did not go at $c$ speed, why?

When we burn a match stick then mass is converting into energy then according to the relativity match stick particles should go at speed of light but it did not happen why