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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Dimensional Paradox Demonstrated by Light Moving Between Parallel Mirrors

In a thought experiment, there are two parallel mirrors which are very long which also face each other. One has a hole in it and one flash from a strobe light shines into that hole. One observer in ...
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1answer
62 views

Restrictions on the form of a function imposed by Lorentz invariance

I need help proving a couple of theorems regarding the most general form of a function with some particular Lorentz-transformation properties. By the way, the question is possibly (though not ...
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1answer
49 views

Matrices belonging to orthochronous Lorentz group

My Professor says that all members of the orthochronous Lorentz group may be written as $e^\Gamma$, where $$ \Gamma^{\mu}_{\nu}=\Lambda^{\mu \rho} \eta_{\rho \nu}$$ Here $\Lambda$ is an antisymmetric ...
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2answers
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Are Lorentz transformations a fundamental law?

I've seen derivations of Lorentz transformation but are they really derivations or are we just teasing out the formula using some special cases and then assuming it to be valid for all the cases. Is ...
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4answers
97 views

Relativistic acceleration in sinusoidal electric field

Consider a relativistic charge $q$ moving with an oscillating electric field $E_z$ with phase velocity $v_p=c$ in direction $\hat{z}$ (e.g. radially polarized laser coprogating with electron). What ...
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1answer
61 views

Hafele Keating in space: twin paradox redux

So Hafele-Keating made sense of the results by taking the center of the Earth as the reference frame. The westward flight "undid" part of the Earth's rotation and those clocks sped up relative to our ...
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What would be seen when a ship is accelerated to relativistic speeds and back down? [duplicate]

Consider this scenario: Two identical space ships, the SS Observer and the SS Accelerator. Each ship is indestructible and contains an indestructible clock. They begin positioned 1 light-day away ...
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1answer
110 views

Can we accelerate photons to travel at speed of $1.5c$? Or any $xc$ when $x > 1$? [closed]

Can we move photons to travel at speed greater than speed of light in vacuum? If no then why? For example: I want to send some photons at 1.5c. Is that possible? How a photon of light can go from 0 to ...
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64 views

$(\frac{1}{2},\frac{1}{2})$ and $(\frac{1}{2},0)\bigoplus (0,\frac{1}{2})$ [duplicate]

I am confused about the notation. What's the differences between $(\frac{1}{2},\frac{1}{2})$ and $(\frac{1}{2},0)\bigoplus (0,\frac{1}{2})$, or maybe $(\frac{1}{2},0)\bigoplus (\frac{1}{2},0)$ ? (...
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35 views

Fixed background theories which feature lorentz invariance?

Are there fixed background theories that also display lorentz invariance? Could be with lorentz invariance being true only approximately at some limit... Realized we can still arrive at time-dilation ...
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29 views

What would be seen if a firing laser is accelerated to relativistic speeds then back?

Consider this scenario: Two identical space ships, the SS Observer and the SS Accelerator. Each ship is spherical with a band of mirrored material around the outside and contains a green laser. They ...
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1answer
89 views

Tachyons and Lorentz velocity transformation

In general, is it possible to apply the Lorentz velocity transformation to a tachyon? I have tried to do so but the results seemed very illogical. Here's my attempt: suppose an evil spaceship named ...
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1answer
46 views

Time Dilation, Relativity Theorie

i have a question on which i've spent a fair amount of time thinking, but couldnt figure it out : We observe (in rest frame) 2 events happens at the same time, one (Event1) happened on Earth and one (...
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2answers
141 views

is following alternative interpretation of total energy possible? E=m'v^2 instead of E=m'c^2 [closed]

I have read the paper, http://arxiv.org/pdf/physics/0206061.pdf "Fundamental Disagreement of Wave Mechanics with Relativity", some time ago, in which the author claims that there is another way to ...
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1answer
50 views

How to find the magnitude of electric and magnetic fields in an arbitary inertial frame?

In the context of special relativity, and using proper Lorentz transformations: If the electromagnetic fields have an uniform value [= constant in space and time] in an inertial frame, how will the ...
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2answers
71 views

Minkowski geometry definition

The general relativity is based on Minkowski geometry definition with its special properties. The general relativity cant be approved wihout Minkowski geometry definition. Why Minkowski geometry is "...
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1answer
34 views

Section 5 Transformation of velocities

In Landau and Lifshitz's The Classical Theory of Fields, section 5 we start with the given transformations: $$ v_x=\frac{v_x'+V}{1+v'_x\frac{V}{c^{2}}},\;v_y=\frac{v'_y\sqrt{1-\frac{V^2}{c^2}}}{1+v'_x\...
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2answers
268 views

Doppler effect of matter waves

We all know that the relativistic mass of a moving object in Special relativity increases for an observer who is measuring it for a moving object. We also know the the concept of particle-wave ...
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3answers
270 views

Why do objects traveling faster appear shortened rather than elongated?

I'm sure this seems like a stupid question but I hope someone can try to explain it as if to a child... This relates to Lorentz contraction. Why do objects in motion relative to the observer not get ...
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1answer
71 views

Given the 1st Postulate of SR, doesn't the 2nd Postulate go without saying? [duplicate]

i've been looking over possible duplicates of this question and haven't found one yet. so, using Wikipedia as the textual source: The Principle of Relativity – The laws by which the states of ...
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1answer
74 views

How can light follow curved spacetime?

At the speed of light, there is supposedly infinite length contraction so the entire universe is a single zero-dimensional point (or an infinitely thin 2D plane perpendicular to the direction of light'...
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2answers
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Are there continuous spacetime events?

What is the formal definition of an event? According to Wikipedia, "an event is a point in spacetime (that is, a specific place and time) and the physical situation or occurrence associated with it." ...
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291 views

Is there a time operator in quantum mechanics?

The question in the title has been asked many times on this site before, of course. Here's what I found: Time as a Hermitian operator in QM? in 2011. Answer states time is a parameter. Is there an ...
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1answer
44 views

What happens when a contracted object going at speeds comparable to light is fit in a tight space, but has been brought to rest

What happens when a rod of length L moving at a speed comparable to the speed of light, is made to fit in a space of length say 3/4*L and is brought to rest. Does it exert some force on the walls ...
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2answers
61 views

Light and Gravity

The gravitational force does not affect the speed of light rather affects the frequency of light (hence light changes colors, red to blue and vice-versa). I know this has been verified but I have 2 ...
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1answer
64 views

Can blue light encounter slower clock time over red?

I am aware that matter with mass experiences dilation and photon is massless. there is no inertial frame where photon is at rest. However, wave form of light has momentum and energy. Blue light wave ...
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1answer
144 views

Is max speed of causality (light) proven experimentally?

Is it possible to have an alternative theory which is consistent with experiments supporting GR, but which doesn't mandate a speed limit on causality? In other words, I understand there is ...
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27 views

Are only measurements registered as events?

When we measure an electron or some other system behaving quantum mechanically, we observe something. Now, this can be called as an event in relativity terms meaning if we live in 1-D spacetime, only ...
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0answers
81 views

how to analyze the collision of two photons with four-momentum vector? [closed]

Q: If two photons with energies $E_1$ and $E_2$ collide, with their trajectories making an angle $\theta$. Is the following right about individual initial 4-momentums and total initial 4-momentum? and ...
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1answer
99 views

Special Relativity in water

If there are 2 observers in water moving relative to each other as well as to water, they measure different speeds of light. So does time dilation occur for them? (since Time dilation is based on ...
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1answer
85 views

A fast object (0.8c) getting overtaken by another fast object (0.9c): why don't times agree?

I'm trying to work on an exercise in Wolfgang Rindler's book "Introduction to Special Relativity" and I'm stuck on the following exercise: Two particles move along the x-axis of S at velocities 0....
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1answer
48 views

Hows does one account for the speed of light delay in field equations?

Suppose I have a simple time varying classical field $\vec{f}$. The force of the field on an object with a charge $X$ at a position $S$ is: $ \vec{F_f}\left( t \right) = X \vec{f}\left( t \right) $ ...
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1answer
226 views

Inverse Lorentz transformation confusion

I've been tripped up for a very long time by this question. I hope that someone can explain it for me once and for all. My question is that when does one use the Lorentz transformation and when does ...
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1answer
88 views

Constant charge in special relativity

We had special relativity introduced in our course and used it to derive some facts. At one place we used the fact that if in frame of reference $U$ the electron has charge $e$, then it also has ...
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52 views

Calculus/Vector Calculus and so on in special relativity book recommandation

I want to learn calculus 1,2,3 vector calculus, analysis and so on in special relativity. But I never found a good and clear book/source on it. Can someone recommend an easy book or internet source on ...
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1answer
43 views

Calculate the relativity of time of an event occurred in different frames

Imagine we have a train which is moving with a velocity and there's an observer inside of that train and there is an observer that is outside of the train observing the train moving. There's a ball ...
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1answer
85 views

Special Relativity Kinematics Problem with My Wrong Solution [closed]

You are traveling toward a large fixed mirror at a constant relative speed 0.20 c0 . At t = 0, when the mirror is a distance d from you, you emit a light pulse from a lantern and then detect the ...
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2answers
89 views

Form of Spin Four-vector

The spin angular momentum of a gyro is represented, in special and general relativity, by a spin four-vector $S^{\mu}$. In the rest frame of the gyro, the spin four-vector takes the form $S^{\mu}=(0,S^...
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1answer
73 views

Why aren't we all moving at the speed of light relative to photons? [duplicate]

Using basic logic.... We know speed and velocity is relative. My point is if we take our speed with respect to a photon moving in opposite direction we are practically moving at speed greater than ...
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1answer
65 views

Time dilation on Satellites due to GR

I am trying to determine the time dilation onboard a satellite (say GPS @ 20,000km) w.r.t an observer on the earth. I have already determined the special relativity component using: $$ t' = \frac{t}{\...
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46 views

What will the point of view be when you move faster than light in a medium?

In water the light become slower to the point where electron in water moving faster than light (in the same medium). So in electron frame of reference what will electron's point of view be? From what ...
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1answer
53 views

Can I prove observed causality like this?

From an older exercise sheet in my relativity class which I completed, but didn't annotate enough to remember it everything was correct: Let $X$ be an inertial observer noticing that a spacetime ...
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2answers
88 views

Why is the relative speed between two inertial frames the same for observers in each frame?

Consider two frames $S$ and $S'$, moving relative to each other. If I stand still in frame $S$ and watch frame $S'$, I can measure its speed to be $V$. However, why is this speed the same as the ...
2
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1answer
84 views

relativistic addition of velocities using tensor notation? [closed]

I know the way of deriving the formula using usual lorentz transformation formulas,,but is there a way out of deriving it using 4-vector notation??please help
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35 views

Redirectioning photons through magnetic lenses

What shape magnet/s would I need to create parallel lines from the ends of a rod shaped magnet?or what shape of magnet would create parallel lines? Is this close?
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1answer
67 views

Question regarding the mass of an alpha particle when travelling at a speed approaching the speed of light [duplicate]

The speed of an Alpha particle is: 10^7 m/s. This is a speed approaching the speed of light. hence, should the (relativitic) mass of the Alpha particle vary?
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About twin paradox [closed]

It is not actually a twin paradox but I have no idea what to call it. So let's assume that there are two person named Alvin and Jack. Alvin drive a spaceship at the speed of 0.6c where Jack is ...
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1answer
116 views

Help me understand Pound and Rebka's experiment

I am a second year undergrad physics student and up until now have done some classical mechanics and some electrodynamics. For some reason I have always been really interested in light. A couple of ...
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What is the relationship between the “mass” of QFT and that of Newtonian mechanics?

In QFT we work with Lagrangians which contain terms $m$ such that the relativistic relation $E^2 = p^2 + m^2$ is satisfied. By classical analogy $m$ is called the 'mass'. We note that due to the ...
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42 views

Relativistic momentum (Lorentz boost) low velocity expansion

If I have a momenta $p^{\mu}=(E, p_x, p_y, p_z)$ and transform it via lorentz boost in x-direction with velocity v I'll get for the new 0th component $E'=\gamma E + \gamma v p_x$ why is this in the ...