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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If I kept getting closer and closer to the speed of light, would I turn into a black hole with respect to an observer?

Now, with special relativity applied to the scenario of me getting closer and closer to light speed, my mass would increase with respect to the observer, and also my length would contract in the ...
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Mass of photon, is it possible? [duplicate]

$P=E/C$ In relativistic mechanics a Photon is defined as. $P=hf/C$ Replacing "P" $ mc=hf/C$ $M=h/CT$ What does it mean, did they have mass?
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Hardy's paradox (see the article “Quantum Mechanics, Local Realistic Theories, and Lorentz-Invariant Realistic Theories”)

Does this thought-experiment (Phys. Rev. Lett., Vol. 68, No. 20, page 2981, year 1992) represent a proof against Bohm's interpretation of the quantum mechanics? The analysis of Hardy rules out local ...
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Why does weak equivalence principle say gravity is equivalent to acceleration?

I am told that the weak equivalent principle, that $m_i=m_g$ (inertial and gravitational masses are equivalent) is equivalent to the statement that in a small system you can't tell whether you are in ...
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Synchrotron radiation and special relativity

My questions below are for all those who assume the point-like electron of special relativity, that strange entity with no inner structure (!), but with intrinsic (?) rest energy, magnetic moment and ...
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Twin paradox, different starting locations

Let's say I have a twin who is at rest relative to myself and ten light years away from me, we are both in rocket ships. We have agreed that I will send a laser pulse and that when he receives it we ...
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Why isn't length contraction permanent even though time dilation is?

It's my understanding that when something is going near the speed of light in reference to an observer, time dilation occurs and time goes slower for that fast-moving object. However, when that ...
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Do paradoxes exist due to velocity addition?

Do paradoxes exist due to velocity addition ? .. In the above diagram, we have a very lengthy 259,627.885 km long space station. Rocket "A" is parked at the left end of the space station. Let us ...
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A neutrino has rest-mass and travels at (near) $c$, why isn't its mass/ energy (nearly) infinite?

If the total energy of all three types of neutrinos exceeded an average of 50 eV per neutrino, there would be so much mass in the universe that it would collapse. This limit can be circumvented ...
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101 views

Is imaginary time a fifth dimension? [duplicate]

I've read that by introducing the concept of imaginary time, the dimension of time can be treated like a spatial dimension mathematically. Assuming, without imaginary time, one considers the universe ...
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Does the (relativistic) mass change? Why?

I learned recently that when an object moves with a velocity comparable to the velocity of light the (relativistic) mass changes. How does this alteration take place?
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535 views

How will the Twin Paradox become, for Time Dilation, if no acceleration was ever involved?

I think one catch in Twin Paradox was about the big acceleration that can turn back the traveling twin from light speed outward bound, to become light speed inward bound. What if there is strictly no ...
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Turning off point for 1g acceleration

Let's say I am on a ship accelerating with 1g. I want to keep the engine running for half a year ( to an observer from my point of origin ) but due to time dilation it would have to be sooner than ...
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Finding the total energy in centre of mass frame

I'm working through a problem in a special relativity textbook (Woodhouse) and I'm having some difficulty. I have to show that if I have a particle of rest mass $M$, total energy $E$ colliding with a ...
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Lorentz transformation of scalar field [on hold]

How can I show that $$\phi(x^{\mu}) - \frac{1}{2}\lambda^{\sigma \rho}L_{[\sigma \rho]}\phi(x^{\mu}) = \phi(x^{\mu} + \lambda^{\mu \nu}x_{\nu}) \,\,\, ? $$ Here, $\lambda^{\rho \sigma}$ are the ...
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Lorentz transformations of spinors in $SL(2,\mathbb{C})$

I was wondering what the matrix representations of all the coordinate rotations and Lorentz boosts of the $SL(2,\mathbb{C})$ were along with a general method of solving for them. I've been able to do ...
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What does Weinberg–Witten theorem want to express?

Weinberg-Witten theorem states that massless particles (either composite or elementary) with spin $j > 1/2$ cannot carry a Lorentz-covariant current, while massless particles with spin $j > 1$ ...
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Time slowed by gravity

If time moves more slowly on Earth (due to our proximity to a gravitational body) than for someone orbiting Earth in a spaceship, yet the opposite occurs in the frequently cited "twin paradox" of the ...
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3answers
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In special relativity, do explanations involving clocks require that the clocks are ticking and that $c$ is fixed?

Are the explanations involving clocks only valid if the clocks are ticking when light hits? Is it true that these thought experiments experiment could only be valid due to the invariance of $c$?
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Is it correct that there is time dilation and time contraction in the same reference frame?

I have played a bit with spacetime diagrams and Lorentz transformation and can see time dilation, length contraction and the relativity of "at the same time". Classical: ...
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Electromagnetic mass of a continuous charge distribution [closed]

I am trying to understand if it is possible to have a consistent solution to Maxwell's equations and Lorentz force equation simultaneously with no other forces present. The Lorentz force density is ...
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1answer
104 views

Schroedinger Equation and Special Relativity

From what I understand, the Schroedinger equation describes how the wave function of a quantum system evolves in space over a given time (I am referring to a relativistic version of the Schroedinger ...
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56 views

Prove the relation between relative velocity ,momentum and energy

In Chapter 8 of F.Mandl's book Quantum field theory, during the derivation of the differential cross section, the following relation is used: $$E_1E_2v_{rel}=\sqrt{(p_1p_2)^2-m_1^2m_2^2} \,\, ,$$ ...
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Can asymmetrical Lorentz forces account for Relativistic affects near the speed of light?

The underlying thought here is that at low relativistic speeds all objects are subjected to emf radiation from all directions. This is basically the sum of all the radiation (light, infra-red, ...
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Special relativity paradox and gravitation/acceleration equivalence

One of the features of the black hole complementarity is the following : According to an external observer, the infinite time dilation at the horizon itself makes it appear as if it takes an ...
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Why does the group velocity of 2D plasmon diverge at small wave number?

Now plasma represents collective wave-like motions of charged particles. In 3D, their frequency is well known to be almost a constant, $\omega^{3D}_p \approx \sqrt{4\pi n e^2/m}$, with $n$=charge ...
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Real representations of chiral fields

Why we can´t have real representations of chiral fields, i.e. why does a multiplet of chiral field (Weyl spinors) under a real representaiton of a Lie Group transforms as a "vector". It is easy to see ...
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Relativistic Kill Vehicle

What would happen if a significantly supra-molecular object (say ranking from grams to low kilotons) would be accelerated to relativistic speeds (>.10 c) such that its worldline would intersect with a ...
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Newton's Bucket

Newton's Bucket This thought experiment is originally due to Sir Isaac Newton. We have a sphere of water floating freely in an opaque box in intergalactic space, held together by surface tension and ...
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129 views

Why should we believe in clock hypothesis?

It is often assumed in special relativity that the rate of a clock in a non inertial frame does not depend on the proper acceleration of the observer. The point is, Rindler's observer shows us that ...
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How can the 'choice' of a photon said to be delayed?

My question arises from two ideas that seem to be contradictory. Idea One: Wheeler's Delayed Choice experiment is an interesting variation of the double slit experiment. Idea Two: In the "reference ...
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Do we move at the speed of light relative to light?

My understanding of relativity isn't very sophisticated, but it seems to me that relative to a photon moving at the speed of light, we are moving at the speed of light. Is this the case?
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Faster than speed of light [closed]

So, I know this maybe dumb but I can't help but to think about this possibility: Let's say that we live in 2050, and we can slow down time. Now, let's say that we slow down time and we turn on a ...
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How are these types of time dilation related?

How are these two phenomena related (if at all): 1. Gravitation slowing down time 2. High speed slowing down time
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Relativity and light speed communication

Say Alice could instantly encode another human being, Bob, into photons. Say Alice then beams those photons to a receiver on another planet, Vogon, one light year away. Charlie is controlling the ...
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Two clocks along different worldlines

I have been reading and watching videos about this subject for a while now. I just can not seem to grasp the idea. Let's say we have two clocks. I leave one at home and keep one in my pocket. Then, ...
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Thought experiment: Tethered galaxies - to the extreme

If two rocks were tied together with a tight, absurdly long, non-elastic rope, and placed on planets at either end of Earth's observable universe - or beyond - What would happen? Is the structural ...
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Length contraction in cyclic space

Consider a flat universe with at least one finite cyclic spatial dimension: travel x meters in one direction, and you will end up back where you started. For an object that is of small size relative ...
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1answer
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Occlusion of light with very fast objects

Take this graphic: On the left there is a light emitter, which can fire light on command, towards the right. There are also two receptors, A and B, both $1$ light second away from the emitter. ...
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There must be free positive charges, moving oppositely to electrons for the wire with current to stay neutral

All popular expositions (e.g. these ones) of relativistic electromagnetism claim univocally that electrons in motion become more dense due to the speed. They teach that Lorentz contraction of charges ...
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$E=mc^2$ why is it $c^2$ and not just $c$?

Why is constant for the conversion of mass to energy square of the ligths speed? is it bedside it's the fastest real matter? .
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Faster than light possibility? [duplicate]

According to general relativity, speed is relative, so for example if you are running at 20 km/h and a car passes you at 30 km/h, the runner is actually moving at 50 km/h relative to the car. Now ...
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There can be nothing with zero mass [closed]

Zero mass has no meaning and is an outcome of 2nd postulate of STR .The STR can be developed without this postulate and thus the postulate is redundant besides being contradictory to 1st postulate.The ...
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Energy of resultant photons from meson decay

I am a little unsure how to answer the following question, Find the energies of two photons emitted in opposite directions along the pion's original line of motion if the pion has a r.m.e of 500MEV ...
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Calculating the velocity of an electron to cause a photon to recoil [closed]

I have a question which asks me to calculate the calculate the velocity that an electron is required to have in order for a photon which strikes it to bounce back along it's incident path and for the ...
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1answer
204 views

Reunion condition in the Twin Paradox

In the Twin Paradox two twins initially at rest in the same reference frame are separated and take different journeys through spacetime. Eventually they are reunited. What is the condition for the ...
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2answers
117 views

Why photon only have helicity other than spin? [duplicate]

When learning angular momentum in quantum mechanics, a spin 1 particle have 3 states. Then I saw from sakurai's modern quantum mechanics that photon's two polarization are just like spins, but with ...
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146 views

What is the theoretical upper limit on the rigidity of a material?

Take a perfectly rigid metal rod of length $2\ell$ and some uniform linear density. Place one end (‘south’) at $(0,-\ell)$ and the other (‘north’) at $(0, \ell)$. Over some reasonably short time ...
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Rotating Observers in Special Relativity: Coriolis-like effect?

Do any noninertial "forces" [terms in the metric] (like Coriolis in Newtonian mechanics) appear to a rotating observer (reference frame) in special relativity? Is the resulting spacetime after ...
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Collisions in special relativity

I am wanting to teach some basic trigonometry to school age kids using relativity and would like help to check my reasoning. First, is my problem formulation correct with respect to special ...