The special theory of relativity describes the motion and dynamics of objects moving at significant fractions of the speed of light.

learn more… | top users | synonyms (5)

0
votes
1answer
74 views

Would forcing a photon to travel under $c$ even after it leaves a medium break Relativity? [duplicate]

So, I stumbled onto this article which really blew my mind (http://www.bbc.com/news/uk-scotland-glasgow-west-30944584). To sum it up, these researchers set up some kind of material that slowed a ...
1
vote
1answer
54 views

Relativity of simultaneity: two light sources

A. Suppose a moving train. The train has two wheels(front and back) and each wheel is connected to light source inside the train. The light source is triggered(light is emitted) when train passes ...
-3
votes
2answers
135 views

Lorentz contraction explanation correct? [closed]

I was having a heated SE chat debate with someone re relativity. One of us believes the explanation above is correct, while the other believes it is not. Who is correct, and, if the explanation is ...
0
votes
1answer
37 views

In relativistic electrodynamics , why doesn't the Lorentz force not change its formulation ? And only the electric and magnetic fields transform ?

My question is that when we want to find the Lorentz force acted on a particle moving in an electric and magnetic field , the equation is invariant in any two inertial relativistic frames. Why is that ...
1
vote
1answer
35 views

Lorentz Invariants and Time dilation/Distance contraction?

If distances contract in direction of motion and time dilates at high speeds, why are the rest mass $m_0$ and proper time $t_0$ called "invariant" under Lorentz transformations. Since depending on ...
1
vote
1answer
58 views

Does travelling towards something at relativistic speed cause it to appear to speed up?

If one were to travel towards a giant TV floating in space, at a fraction of the speed of light, would a video playing on the TV appear to play faster? I'm guessing the answer is no. From what I ...
1
vote
2answers
70 views

Is the speed limit as light speed just based on what we see? [duplicate]

I know, the title makes no sense, generally. Let me explain. I am just asking a question for which I found an answer nowhere (not even here). i think similar questions has been asked before and, no ...
1
vote
3answers
85 views

Mass has the same value in all inertial reference frames?

Is mass the same in all inertial frames? If it is, why is that? If not, can you also explain?
3
votes
3answers
152 views

A train on a track--relativity paradox

While answering a question over on Worldbuilding.SE I found myself looking at a situation that I can't figure out: You have a train track of length L that makes a very large circle. You have a train ...
1
vote
2answers
114 views

(Hyper)Surface of Simultaneity

How can I determine the surfaces of simultaneity if I know the metric? In particular, what are the surfaces of simultaneity for rotating disk with Langevin metric: $$ ...
2
votes
1answer
82 views

Michelson Morley experiment? [closed]

Its not that I question the conclusions reached concerning the Michelson–Morley experiment, however I would like to know how the following issue was addressed please? If I could pass bob through a ...
0
votes
1answer
31 views

Force required to produce a specific motion on a particle [closed]

This exercise comes from the Exercises for the Feynman Lectures, Chapter 15. The full question: 15-6 A particle of rest mass $m_0$ is caused to move along a line such that its position is: ...
0
votes
1answer
50 views

Using light clocks, can one derive the length contraction formula without the 'bouncing' of the photon?

In the following link, the equation for time dilation is derived by allowing the photon to just go from the lower mirror to the top, without reflecting back to the bottom: ...
1
vote
1answer
50 views

Why is the spatial term for contravariant 4-gradient negative, whereas for other 4-vectors it is the covariant part that is negative spatially?

The contravariant 4-displacement is: $${x}^{\alpha} = (ct,\mathbf{r})$$ And the contravariant 4-gradient is: $${\partial}^{\alpha} = (\frac{1}{c}\frac{\partial}{\partial{t}},-\nabla)$$ From what I ...
-1
votes
1answer
53 views

Error in deriving relativity velocity addition formula [closed]

$D$ is traveling at .995c with respect to $C$ who is traveling at .995c with respect to $B$ all in the same direction. We want to compute $D$'s velocity as observed from $B$. Note that the Lorentz ...
3
votes
1answer
117 views

How is it possible to change the direction of a spin by boosting?

In Weinberg QFT section 2.5.5, he defines the states of momentum $p$ by $$\Psi_{p,\sigma}=U\bigl(L(p)\bigr)\Psi_{k,\sigma}$$ up to some irrelevant normalisation, and $L(p)$ is the Lorentz ...
1
vote
1answer
95 views

What is the meaning of $\mathrm{d}^4k$ in this integral?

From Gerardus 't Hooft's Nobel Lecture, December 8, 1999, he states the following equation (2.1): $$ \int \mathrm{d}^4k \frac{\operatorname{Pol}(k_{\mu})}{(k^2+m^2)\bigl((k+q)^2+m^2\bigr)} = \infty ...
0
votes
1answer
54 views

Twin Paradox From Neutral observers perspective

Suppose two planets A & B, with B moving away from A at velocity v. A spaceship departs from A in the direction of B at velocity v (putting it in the same inertial frame as B), and remains that ...
0
votes
1answer
49 views

Active transformation and passive transformation of a scalar field

For the Lorentz transformation $x \to x'=\Lambda x$, the active transformation is $\phi(x) \to \phi'(x)=\phi(\Lambda^{-1}x)$ and the passive transformation is $\phi(x) \to \phi'(x)=\phi(\Lambda x)$. ...
-3
votes
2answers
96 views

Rational for the Principle of Relativity [closed]

When Galileo postulated his principle of relativity, it seems like quite a logical assumption. After all, velocities combine cleanly, and everyday observation seems to show that the laws of physics on ...
0
votes
0answers
43 views

Relativistic oscillator vs. non relativistic oscillator

Consider a particle of mass $m$ that is constrained to move under the potential $U=k|x|$. In the case where the particle's motion is non-relativistic, the Lagrangian for the motion is ...
8
votes
3answers
2k views

Is there a maximum energy for a relativistic particle?

So I was told today that the Standard Model breaks down at really, really high energies. The lecturer mentioned particles such as electrons hypothetically having energies equivalent to that of entire ...
1
vote
0answers
122 views

Model special relativity is built. Question: rod length is reduced by the fact, or it seems to us? [closed]

Model of special relativity is a system of two observers and two rods (Figure 1a). Here $AB$ and $A\,'B\,'$ - rods with a length $l_{\,0}$. At points $D$ and $D\,'$ are observers. $R$ - permanent ...
0
votes
0answers
51 views

A couple of questions on mass increase

I found these experimental data on mass increase. Data of the Bertozzi experiment show close agreement with special relativity. Kinetic energy of five electron runs: 0.5, 1, 1.5, 4.5, 15 MeV ...
35
votes
4answers
1k views

Is there an underlying physical reason why the Coriolis force is similar to the magnetic component of the Lorentz force?

I couldn't help but notice that the expression for the magnetic component of the Lorentz force, $$\mathbf F = q\,\mathbf v \times \mathbf B\,,$$ is very similar in its mathematical form to the ...
0
votes
1answer
43 views

Motion in space

Does a space shuttle travelling in space experience any resistance to its motion? If a body in space is applied constant force, does it attain speed of light after sufficient time?
0
votes
0answers
45 views

Twin Paradox Variation using 2 rockets [duplicate]

Instead of a twin on earth and a twin on a rocket, what would happen if they were both on separate rockets facing opposite directions. One fires off at 0.7c and the the other fires off at 0.2c. Then ...
0
votes
0answers
67 views

How the state of elementary particles change under lorentz transformation?

Let us take three observers namely Alice, Bob and Charlie. Bob is stationary with respect to Alice, but his axes are rotated from her's.We can get Bob's coordinate axes by rotating Alice's through 60 ...
0
votes
1answer
69 views

How to derive the components $\Lambda^i_j$ of a Lorentz-transformation given a boost $\vec{v}$?

I am stuck in deriving a specific formula concerning Lorentz-boosts. In my Classical Mechanics skript there is a chapter dealing with special relativity. In this chapter the Lorentz transformations ...
0
votes
0answers
23 views

Understanding what a tranformation on a Ray and Hilbert space

I've been referring to Chapter 2 of Introduction to Quantum Field Theory by Weinberg where he talks about symmetries and how they go about. Now, there are two points that he mentions. A ray, which by ...
0
votes
0answers
35 views

Relativity of simultaneity: light source inside and outside

(Orange are light sources and red are observers) There is a train, which is moving right. In each side, there is a light source, which emits light when the train passes certain point on a track. And ...
1
vote
1answer
57 views

What would happen if light was converted into matter as it is propogating?

If light is a form of energy and can be converted into matter then does light slow down since no mass full object can reach the speed of light
33
votes
6answers
4k views

What is the proper way to explain the twin paradox?

The paradox in the twin paradox is that the situation appears symmetrical so each twin should think the other has aged less, which is of course impossible. There are a thousand explanations out there ...
2
votes
2answers
84 views

Does invariant mass depends of temperature? [duplicate]

From special relativity theorie we know that $E = mc^2$. When a system acquires energy, mass becomes greater. That is clear for kinetic energy, because we have a formula that gives m as a function of ...
0
votes
2answers
67 views

Time Dilation diagram on wikipedia

The wikipedia article on Time Dilation (http://en.wikipedia.org/wiki/Time_dilation) has an explanation involving the following two diagrams: I have some problems with these diagrams. In the second ...
0
votes
2answers
78 views
-1
votes
3answers
86 views

How time dilation happens by velocity?

i got many explanation and proving that relative velocity causes time dilation. Einstein's moving light experiment proves it. but that is a clock works with light detector. as detecting the light gets ...
-3
votes
1answer
59 views

Why is there a cap on the speed at which we can attain? [duplicate]

Also, If you are traveling 1 mph under the speed of light on a train and throw a baseball in front of you at 20mph what would a viewer outside the train see?
5
votes
2answers
202 views

How does light change directions? [duplicate]

To the best of my knowledge, light will always travel at the speed of light. How then does it get reflected and change directions? Wouldn't it have to decelerate, come to a stop, and then accelerate ...
0
votes
0answers
18 views

A few positrons collide with a solid body at rest; what can happen?

Suppose we have a macroscopic solid object. Now we have a beam of Positrons that is injected into this solid Body at vacuum. What can happen? There will take place a pair Annihilation of electrons ...
2
votes
1answer
56 views

Canonical field momentum in quantum field theory

In the context of the second quantization and the use of fields in the canonical quantization, the canonical momentum of the field is defined as the derivative of the field by the time coordinate. But ...
0
votes
2answers
52 views

Speed of light and infinite energy [duplicate]

While browsing some physics websites, I saw that to make an object reach the speed of light, it requires infinite energy and talked about its relation with Einstein's famous equation $E=mc²$. However, ...
1
vote
0answers
81 views

What is the status of Lorentz Invariance in String Theory ? Is it global or local?

The questions is simple, what is the status of lorentz invariance in string theory ? Is it global or is it only local ? The proof of absence of anomalies assumes lorentz invariance. However, I believe ...
1
vote
2answers
59 views

Would this be correct for kinetic energy in special relativity?

In galilean relativity $$p=mv$$ and $$KE=\frac{1}{2}mv^2$$ If I understand it in special relativity the equation for momentum is $$p=\frac{mv}{\sqrt{1-\frac{v^2}{c^2}}}$$ In galilean relativity ...
1
vote
1answer
84 views

How do you calculate time dilation when neither frame is inertial?

I'm reading Hartle, Gravity and read bout the Twin Paradox. I understand why there isn't really a contradiction, one frame is inertial, the other isn't. However, I'd like to know how to calculate time ...
3
votes
1answer
53 views

Is time a vector in Minkowski space? [duplicate]

I am arguing about this topic with my school teacher in so long time, I want to finish this debate. My teacher's opinion is "Yes, Time is vector" because four-vector has $t$ component, and mine is ...
1
vote
1answer
133 views

What are the expression for Energy and Momentum of tachyons in terms of their 'rest mass'?

We examine the possibility of tachyons under the criteria that they form the energy momentum four vector that transforms according to Lorentz Transformations. Therefore, $E$$'$ ...
4
votes
0answers
41 views

How does combining special relativity with quantum mechanics produce spin? [duplicate]

I have read and heard that the intrinsic property of spin that elementary particles have comes from combining special relativity with quantum mechanics. How does combining special relativity with ...
1
vote
2answers
32 views

time of flight between two scintillators

I found this page on Wikipedia about finding distance between time of flight of two particles passing past two scintillators, https://en.wikipedia.org/wiki/Time_of_flight_detector, but I can't find ...
1
vote
0answers
22 views

Time in the early universe [duplicate]

When it is said, for example, that grand unification took place "Between 10−43 second and 10−36 second after the Big Bang", how are these figures of time derived? Moreover, do these figures have any ...