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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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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Why should we believe in clock hypothesis? [closed]

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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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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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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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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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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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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243 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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657 views

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 relativity,...
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Why does the equivalence principle not violate special relativity?

If the equivalence principle asserts that there is no way to determine whether our reference frame is accelerating or is being acted upon by gravity (i.e. the laws of physics are the same in both ...
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Can Minkowski spacetime be redefined as a non-flat riemannian manifold?

Minkowski space time is defined in terms of a flat pseudo-Riemannian manifold. I have wondered if it can be redefined as Riamannian manifold and in the case what type of curvature would there appear. ...
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Is it possible to transfer classical bits of information faster than light speed?

Is there any known, verifiable way to transfer classical information faster than light, using quantum entanglement or other phenomenon? Does quantum teleportation, or other known phenomenon, allow ...
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Decompose a massive four vector in to two massless ones

I'm trying to decompose a massive four-vector, $p_1$ with $p_1^2=m^2\neq0$, in to two massless ones, $k_i$ with $k_i^2=0$. But I'm having trouble find basis vectors $k_i$ such that I can always ...
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179 views

Einsteins idea about solving the ether problem [duplicate]

I'm struggling a bit with my Special Relativity course. Most exercises are quite trivial and can be done without much effort, but when you really start to think and analyse why and how certain things ...
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Textbook for relativity: modern version of Bondi's Relativity and Common Sense?

I am looking for a textbook on relativity for school children. A background in simple vector based mechanics could be assumed. Primarily it needs to be readable at high school English reading level ...
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What happens in the twin paradox if the ship doesn't return?

What happens if the twin in the spaceship doesn't return? Would he still be younger than his other twin? Is the symmetry broken simply by accelerating out of earth? If it is still symmetrical when ...
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Magnetic force and frames of reference

I'm having a hard time trying to understand the next situation: Suppose that I have a magnet that creates a quite uniform magnetic filed $\vec B$. In the vicinity of this magnet there is a particle ...
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Why is light different than sound in terms of the assumptions we make regarding causality?

I am having trouble understanding, from a conceptual point of view, why it would be impossible to travel faster than the speed of light. I have read one explanation given in the form of an example ...
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Einstein's space-time theory [closed]

I'm a high school student who never studied any relativity before, but I'm just wondering what was THE question that Einstein asked himself before going into this field. I knew he has done lots of ...
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How does a particle of light reach the max speed of light? [duplicate]

Possible Duplicate: How can a photon have no mass and still travel at the speed of light? First of all I am not a professional physicist. I was curious as to how a particle of light can reach ...
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Length Contraction Confusion

i'm having a bit of trouble wrapping my head around special relativity, so i'd like to explain what I think is going on, to see whether or not I have understood. The question i'm thinking about is ...
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What conservation law corresponds to Lorentz boosts?

Noether's Theorem is used to related the invariance under certain continuous transformations to conserved currents. A common example is that translations in spacetime correspond to the conservation of ...
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Does Special Relativity require a “ruler postulate” analogous to the “clock postulate”?

It's fairly well known that the clock postulate is needed in Special Relativity when dealing with accelerated clocks, so does something analogous exist when dealing with accelerated spatial ...
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Consistent answers in special relativity [closed]

I was doing a question about if a train fits in a tunnel. From the train frame it does not and from the tunnel frame it does. Then the question asked are these two answers consistent? What does this ...
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Has relativity of simultaneity been directly observed?

I know that thought experiment about trains when a flash of light in the middle reaches the both end simultaneously for a passenger but different times for the bystander. So were there (non-thought) ...
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Can matter be annihilated to form kinetic energy

I don't know much about conversion of energy and all, but I had a simple question: Can the energy released by converting matter into energy be used to set other particles in motion (increase their ...
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Question from Griffiths (EM): Synchronized clocks

There's this vague conceptual question from the textbook Introduction to Electrodynamics by David Griffiths Problem 12.5 Synchronized clocks are stationed at regular intervals, a million km apart, ...
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Moving coil contradiction of Faraday Induction

In Faraday's Induction Experiment, the e.m.f. induced in the induction coil becomes zero when the relative velocity of the coil and the magnet becomes zero. But one can also argue from a stationary ...
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Spin of an operator in supersymmetric theories

How exactly is the spin of an operator in the context of a supersymmetric theory defined? For example, in page 25 of [1], $\mathcal{N} = 2$ supersymmetry is defined to have operators $J, G^{+}, G^{-}, ...
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Scalar products in the spinor helicity formalism

In A. Zee's book Quantum Field Theory in a Nutshell (2nd edition), Chapter N.2, page 486, the momentum $p$ is written as a $2\times 2$ matrix: $$ p_{\alpha\dot{\alpha}} = p_{\mu} (\sigma^{\mu})_{\...
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Problems when a disc is rotating at extreme speeds (theory)?

I was wondering the problems that would occur (aside from mechanical friction), when a disc rotates at high angular velocity. Is centripetal force an issue if high torque is applied on a disc (massive ...
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How can I calculate the time dilation factor for velocities as low as 10 m/s? [closed]

I need to calculate time dilation factors; I tried using my calculator but for some reason my calculator cannot go that low when the velocity is on the order of 10 m s-1. What mathematical techniques ...
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Perceived direction of light emitted in moving reference frame

I was thinking the other day about the simple example used to demonstrate time dilation effects and to derive the Lorrentz factor - where the time it takes for a light pulse to be emitted, bounce of a ...
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Is Helicity an intrinsic property of massive Neutrinos?

Hyperphysics states that, unlike an electron, the helicity of a neutrino is invariant because we cannot change to a reference frame where it is different: This and subsequent experiments have ...
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Lorentz transformations: Which coordinate system is marked?

I am confused about a basic special relativity question. So we have the Lorentz transformations $$\begin{align} x' &= \gamma(x-ut) \\ t' &= \gamma(t-ux/c^2)\ , \end{align}$$ where frame $S'$ ...
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Light angles measured in moving reference fame (SR, homework)

I've managed to get through all of this question without trouble until part d). The full question is given here: I've calculated the "true" angles of Star A and Star B as 71.57 degrees and 45 ...
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Formal definition of an observer?

What is the formal definition of an observer in special relativity? I have seen a few: The actual coordinate system. The collection of synchronised clocks that cover the coordinate system. A well ...
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Why is coordinate time frame dependent? [duplicate]

Here is what I understand by coordinate time. It is the time difference measured between two events, using two synchronized clocks, one present at each event, and the difference is measured in an ...
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Why do we write the lengths in the following way? Question about Lorentz transformation

Yesterday we have studied the Lorentz transformation in school. So we have two frames of reference, $S$ and $S'$ . $S$ is stationary and $S'$. $S'$ has a constant velocity $v$, relative to the $S$ ...
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Does path integral and loop integral in a Feynman diagram violate special relativity?

Consider a correlation function between two points $A(x_1,t_1)$ and $B(x_2,t_2)$, we need to integrate over paths which could be infinite long. But the time length $(t_1-t_2)$ is finite, so if $A$ and ...
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Maxwell's Equations using Differential Forms

Maxwell's Equations written with usual vector calculus are $$\nabla \cdot E=\rho/\epsilon_0 \qquad \nabla \cdot B=0$$ $$\nabla\times E=-\dfrac{\partial B}{\partial t} \qquad\nabla\times B=\mu_0j+\...
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Question about time dilation and relativity [duplicate]

Take this scenario for example: I am on a rocket ship that will take a trip into space and back at 90% the speed of light. And my friend "Bob" stays on Earth. As soon as I leave Bob and I both start ...