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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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 ...
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Will heating up an object increase its mass? [duplicate]

According to the $E=mc^2$ equation, will an object whose thermal energy (temperature) rises also weigh more? And by the same token, will the mass of an object decrease as its temperature approaches ...
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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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Length contraction, front middle or back

I still don't have a solid understanding of Length contraction. Imagine we have a ruler of length $L$ that starts at rest upon a ground with markings on it, then accelerates until nearly the speed of ...
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Doppler shift for a uniformly accelerating observer

This was given in textbook as an example. An observer on a spaceship with a four velocity $u$ is approaching from $x = +\infty$ a star at rest in the reference frame $S$ while undergoing constant ...
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What is the definition of density in a relativistic context?

In this question, there seems to be a clear presence of ambiguity, which raises the question: what is density in relativity? First of all, the question asks for the relativistic mass, "the apparent ...
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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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52 views

Transverse doppler effect in light

In most books to explain transverse Doppler effect the following example is given: Consider a source that emits flashes at frequency f0 (in its own frame), while moving across your field of vision at ...
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The Relativity of Simultaneity and its Impact on “Seeing” Events

Will the rocket really see the supernova L first for sure? The position of the rocket is not specific. We just know that it is at the left of the galaxy. We know that R will explode first in the ...
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558 views

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 ...
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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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Time Dilation Geometry

I was recently exploring time dilation from Gravity and from velocity and I came up with an interesting derivation that I have not seen before. I was wondering if there is a paper published showing ...
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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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About the relativistic wagon simultaneity problem

I'm getting utterly confused with this problem. The situation is basically to know what events to take in one frame in order to see them synchronized in another. I sketched the situation as this: ...
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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} ...
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Using Special Relativity in Uniform Circular Motion [duplicate]

Can one utilize the formulas of Special Relativity in uniform circular motion? The radial component of the object does accelerate, but sometimes we are just interested in its tangential speed. Here ...
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54 views

Plane curve transform to moving inertial system coordinates

As a non-phycisist I hope my question makes sense and is understandable. It deals with special relativity. I suppose there is a e.g. plane curve ( e.g. a circle ) given in the x-y plane of of an ...
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Relativistic centripetal force

The thought randomly occurred to me that a circular particle accelerator would have to exert a lot of force in order to maintain the curvature of the trajectory. Many accelerators move particles at ...
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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 ...
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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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What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...
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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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74 views

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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Vector spaces for the irreducible representations of the Lorentz Group

The definition of a representation is a map to the space of linear operators over a vector space. My question is: What are the corresponding vector spaces for the $(0,0)$ Representation ...
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How much real and how much relative is our universe?

Apologies in advance if my question appears more philosophical than practical. It is indeed philosophy, but a philosophy relating to our scientific understanding of the universe as a whole. Special ...
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4answers
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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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Can a relativistic quantum particle be completely confined into a finite hole?

If we write the Klein-Gordon equation in this form \begin{equation*} c^2 \hbar^2 \nabla^2 \Psi = \hbar^2 \ddot{\Psi} + 2i\hbar (U - mc^2) \dot{\Psi} + U (2mc^2 - U) \Psi \end{equation*} we have a ...
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Detecting absolute motion inside a box

This is not a contradiction and I know it is impossible but still consider a thought experiment by me and point out if something is wrong. See the following picture and then the explanation follows. ...
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Is there a mathematical reason that the Lagrangian is Lorentz invariant?

The Hamiltonian is directly related to the energy, which is just one component of a four-vector and therefore not Lorentz invariant. The Lagrangian is the Legendre transform of the Hamiltonian and I ...
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1answer
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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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Can the Cosmos itself be assumed as a reference frame?

Einstein believed that there are no reference frame in the universe in accord to his Special Relativity (SR). Now imagine a man, as the first observer, and his cat, as the second, are both at rest in ...
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Why magnetic field lines and force are not orthogonal with magnets?

The below explanation why magnetism exists is superb in this video. The explanation about magnets is also great in this video. A magnet has atoms with unpaired electrons forming mini magnets. The ...