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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What is the deep reason of length contractions and time dilations? [duplicate]

In the theory of relativity, a spacetime can have length contractions or length expansions and time can have time dilations or expansions. In theory of special relativity, any physical object with ...
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27 views

Length Contraction and Acceleration [duplicate]

Say that I have a spaceship that needs to travel 490 lightyears to the exoplanet Kepler 186f. Half the way of the trip the spaceship accelerates with a constant acceleration of 1G and on the other ...
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1answer
32 views

How to calculate relativistic mass versus time?

I know that relativistic mass is calculated as: But when mass m0 gets bigger, also mass of the accelerating body mass m gets bigger so m0 gets bigger and so on. So if body accelerates with ...
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104 views

What is the basic concept of four-dimensions in physics?

I have been reading a few books lately and browsing the internet for an explanation on the concept of "four-dimensional" space (or, space-time, as some of them have been calling it). But, what those ...
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What am I missing about the interaction between electromagnetism and Lorentz length contraction?

I was recently reading this short article: http://galileo.phys.virginia.edu/classes/252/rel_el_mag.html It explains how magnetic and electric fields are related because in one frame of reference where ...
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Why are one-particle states called representations of Poincaré group?

The one-particle states in the Hilbert space of a quantized relativistic field theory are said to form representations of the Poincaré group. Why is that? I mean, popular texts in QFT do not ...
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Special Relativity and Space travel [closed]

I'm doing a science project on space travel where I have to include a part about special relativity and how time acts when you're traveling in space with high speed. I'm not really sure where to start ...
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2answers
61 views

At what speed is the conservation of angular momentum carried out?

If the sun suddenly slowed down would pluto's orbit immediately speed up? If so, then isn't the information pertaining to the sun's angular momentum change being carried to Pluto faster than light? ...
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Basic Special Relativity Problem [closed]

A cylindrical rocket 10 m long and 2 m in diameter moves at a speed $ V=0.9c $ with respect to earth, where $c$ is the speed of light in vacuum. I. Knowing that the pilot's heart beats 70 times per ...
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27 views

Real and relative velocity formula

What i need is a thing more complicated than the usual relative velocity formula. Imagine a radar. You are at the center, moving at some angle, but lets make it clear, you are always at the center. ...
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34 views

Why do we sum relativistic intervals in relativistic action of a massive point-particle, and not a function from it?

Relativistic action as follows (which should explain relativistic motion of a classical particle): $$ S = C \Delta s=C\int ds $$ Where $C$ is some constant and $\Delta s$ is relativistic interval. ...
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74 views

How is time dilation invariant of observer?

From one observer's perspective, on all moving objects time will run slower. But from the perspective of one of those objects, it's the observer who's slow. And the answer seems to be that both are ...
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44 views

Can we see ourselves slower due to time relativity?

Please bear with me because I'm noob at physics. Numbers don't have to be calculated, these are just examples, I'm just asking conceptual stuff. Just double check: Objects traveling at $0.99c$ in ...
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1answer
105 views

How can I prove that D'Alembert operator is invariant under Lorentz transformations?

I'm currently taking a course on Classical Electrodynamics and I'm trying to prove that the D'Alembert operator ($\square=\eta^{\mu \nu} \partial_{\mu} \partial_{\nu}$) is invariant under Lorentz-like ...
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1answer
77 views

What is the difference between scalar and vector mesons?

My understanding is that vectors and pseudooscalars change sign under parity operation and pseudovectors and scalars do not. However, I don't understand what the difference between a vector and ...
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2answers
123 views

Classical physics in curved space

I'm trying to learn General Relativity. As a stepping-stone between classic (Newtonian) physics and complete relativity, imagine a universe where space is curved, but time is perfectly flat. Also, the ...
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48 views

Travel by Earth rotation [closed]

why we can't go outside the atmosphere and travel with earth rotation .. and can we travel in the opposite direction of atmosphere by the same speed of atmosphere it’s moving at about 1,000 miles an ...
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1answer
55 views

Special relativity and Simultaneity

I am struggling on a problem involving 2 events seen in different reference frames and could do with advice or a starting point for this question: A spaceship approaches a galaxy travelling with a ...
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1answer
61 views

Atoms traveling at the speed of light [closed]

If an atom was to travel at the speed of light (although impossible), wouldn't the nucleus break apart? I say this because the particles holding the protons together in the nucleus wouldn't be able to ...
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1answer
79 views

Electron decay in high-energy accelerators

As far as I understand, electrons are infinitely stable since they are the least massive particle with non-zero electric charge. However, when accelerated to high-energies, the energy (or mass) of the ...
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232 views

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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61 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
40 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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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
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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
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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
100 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 ...
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$(\frac{1}{2},\frac{1}{2})$ 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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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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26 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
56 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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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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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
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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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62 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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30 views

Section 5 Transformation of velocities

In Landau and Lifshitz's The Classical Theory of Fields, section 5 we start with the given transformations: $$ ...
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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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164 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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37 views

Action of a particle travelling in Minkowski space [closed]

The action of a particle moving in Minkowski space [signature $(-+++)$] is given by $$S=-m \int dt\sqrt{-\eta_{\mu\nu}(X)\dot{x}^\mu \dot{x}^\nu}$$ Inserting in the Metric I get $$S=-m\int dt ...
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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
71 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 ...
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78 views

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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161 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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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
60 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 ...
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1answer
58 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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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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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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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 ...