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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Tomorrowland movie and tachyons? [duplicate]

Would be possible if tachyonic existed to send info to the past or see the future? since the tachyons according to special relativity could travel to the past? i have searched in wikipedia and the ...
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Relativity and “light years”

As I understand relativity, time is relative to your velocity, meaning your watch moves slower relative to those who are stationary (relatively) when moving at great speeds. So if that's true then ...
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Is static gauge quantization of the particle equivalent to covariant quantization?

In the covariant quantization one is able to get directly (from the constraint $p^\mu_\mu+m^2=0$) the Klein-Gordon equation. But if one uses the parametrization $\tau=X^0$ then the Schrodinger ...
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Constant Jerk Relativistic Rocket [duplicate]

A quick google search will give many helpful pages and calculators regarding constant acceleration relativistic rockets, but my question is somewhat different. What if jerk is the parameter to be ...
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Why cannot a perfect clock exist?

I have a question about the reason Feynman gives for why a perfect clock - a clock that remains in sync while in motion with a stationary clock, cannot exist. It is clear why the "light clock" ...
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Prove that the spacetime interval is not invariant under Galilean transformations [closed]

The spacetime interval $(\Delta s)^2 = (\Delta x)^2 + (\Delta y)^2 + (\Delta z)^2 - c^2(\Delta t)^2$ is invariant under the Lorentz transformation and this isn't the case for the Galilean ...
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Is the double slit experiment valid in all inertial frames?

In a double slit experiment done with particles having mass (say electrons), the results are inferred as being caused by probability waves. The wavelength of these waves is dependent upon the velocity ...
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How can light cross $c$ in the given hypothetical experiment? Where I am wrong? [closed]

There is a concave mirror, which has somehow maintained the speed $\frac{c}{2}$ toward west ( for instance) , and there is a light wave or you can say a ray of light is moving in N-E direction. So we ...
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Boosting massless particles

How does one calculate the boost matrix to go from a photon of (standard) four-momentum $k^\mu = (k,0,0,k)$ to $p^\mu = (p,0,0,p)$? (in terms of $|p|/|k|$) Weinberg in his Quantum Field Theory Vol.1 ...
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What is a Lagrangian of a photon? [duplicate]

In sense of classical mechanics+special relativity what is lagrangian of a photon? Lagrangian of a relativistic massive particle is as follows: $$ L_{massive}= -mc\sqrt{c^2-v^2} $$ So is it a zero?
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Does the rest mass energy include the potential energy of the particle?

The potential energy (as far as I have studied - that is, mainly classical physics) depends on the reference level, since its absolute value cannot be calculated. It can therefore be negative as well. ...
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Does constant acceleration (from starship crew pov) to relativistic speeds look newtonian?

The last 25 years I thought that time dilation, mass increase and length contraction is "scaled" that way that on the first glance the crew of an accelerating starship could think everything is ...
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Why is the speed of light a limit? and why is it just $3×10^8\,\text{m/s}$? [duplicate]

Why does light travel with speed $3×10^8\,\text{m/s}$? and why not more?
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Relativistic approach of a car and a train to a crossing: seeming contradiction

Suppose a car is approaching a railroad crossing at a high relativistic speed, while on the tracks, a square rail car is also approaching the crossing at the same speed. (The road and the railroad ...
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What exactly is $T_{\mu\nu}$?

Continuous matter is described in special relativity by the matter tensor which is the so-called stress-energy-momentum tensor. I am finding a difficulty understanding how a tensorial tool ...
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Is there a geometric interpretation of the spacetime interval?

In Euclidean space, the invariant $s^2 = x^2+ y^2+ z^2$ is equal to the length square of the position vector $r$. This is easily understood and can be represented geometrically in a graph. On the ...
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How should I interpret relativistic mass? [duplicate]

If I have a mass that gets accelerated to a near the speed of light, before it gets I would think its relativistic mass would expand its Schwarzschild radius enough to turn it into a black hole. I ...
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What defines the spin of a certain field? (formally)

Update: see the restatement of the question below! I've seen this question over and over through the archive of questions, but so far the closer to an answer was this. But I still don't understand. ...
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Special Relativity and Gravity

As Einstein was seeking a relativistic theory of gravity, he thought that special relativity should be upgraded to general relativity thus promoting the Minkowski space to curved pseudo-Riemannian ...
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Physics behind this neutrino-related joke

In the comment section of a newspaper article reporting on the 2015 Nobel Prize for Physics, which was awarded for work on neutrino oscillation, I found the following joke: "I'm sorry, we do not ...
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Does my interstellar pole thought experiment violate casualty? [duplicate]

I have heard that it is impossible to send a signal faster than light. However, what if I had a long (4.5 light years) pole and placed one end on Earth and the another end around Proxima Centauri. If ...
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Observing light speed

Consider an observer B is moving with speed $0.8c$ relative to another observer A in standard-configuration (I think it is called that in english: that the system B is only moving along the $x$-axis ...
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Question/Doubt about Time Dilation Symmetry in Special Relativity

Apologies if this has been asked and answered before, as I am still having doubts reconciling the symmetrical effects of time dilation (i.e each frame sees clocks of other frame slowing down), and I ...
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What is the physical significance of Rapidity in Relativistic kinematics?

Recently I have came across a new term called rapidity in relativistic kinematics. We are using it in relativistic kinematics due to its additivity whereas velocity is not a additive quantity in ...
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Why must the speed of the aether wind be so small compared to the speed of light?

I was doing some reading on the Michelson-Morley Experiment. One of the principle equations for the equations is this one. $$\frac { 2w }{ c } \times \frac { 1 }{ 1-\frac { { v }^{ 2 } }{ { c }^{ 2 ...
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Could this be a valid reason for why the universe could be infinite?

So, special relativity says that every frame is as good as any other frame, and there is no absolute frame of reference. All good. Suppose there is a finite universe (let's just assume the universe ...
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How can length contraction result in electron circular motion in a magnetic field?

If you ask around about magnetic fields, you will read seemingly-authoritative articles which say magnetism is a consequence of length contraction. This is widely taught and is repeated in answers ...
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Why is the speed of light in vacuum what it is?

Three-pronged question on the speed of light. One: simply, do we know why the speed of light in a vacuum is what it is and why nothing is allowed to go faster? Two: if we knew why the speed of ...
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Relativity of simultaneity: Is my reasoning here correct?

I have a situation similar to that underlying the twin 'paradox' - the observer m1 below remains stationary while the observer m2 goes off on a space-time trajectory, and then returns to m1's ...
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How can relativistic effects be the cause of magnetic forces when the normal speeds of carrier charges are so low?

I had read here that magnetism arises from a current because of the special relativistic effect associated with the speed of the moving charges in that current. However that speed is only on the ...
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Determining the velocity of an inertial frame of reference

Back in grade 12 I was told by my physics teacher that one would have no way of determining the velocity of an inertial frame of reference without comparing it to another (e.g. if a person was in a ...
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Why is light in vacuum so slow? [duplicate]

Accepting the speed of light in vacuum and infinite mass and all that, I wonder why light does not have infinite speed? I know light does not have rest mass, but people use the term infinite mass ...
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Are there any well-known large body objects moving at a significant fraction of the speed of light relative to earth?

Introduction I've been reading a book called PsychoPhysics, part of the "Illuminati God Series" by Mike Hockney (a pseudonym). Without getting into too much detail, they basically believe that the ...
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What speed does a proton have with the energy 7 TeV?

So this is a question from the 2014 admission test for Chalmers University of Technology, Gothenburg. To clarify some rules (cited and translated from the test): Calculators and physics ...
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In a nuclear reaction, where does the energy go?

Lets say two hydrogen fuse together, where does the energy released go? Is it carried away as momentum imparted on the helium atom? Is it carried away in neutrinos? Is it carried away as gamma rays? ...
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What experiments have been done that confirm $E=mc^2$?

What experiments have been done that confirm $E=mc^2$? Are there experimental results that contradict $E=mc^2$? Or are experimental results consistently showing this famous formula to be true?
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Michelson-Morley expression for relative phase

I am trying to find the relative phase when ether is propagating vertically versus when ether is propagating horizontally. The question is written below When the light (of wavelength) is split at the ...
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Deduce time dilation from a Minkowski diagram?

Is it possible to deduce the phenomena of time dilation from a carefully constructed Minkowski diagram? For example, consider the image below. Here, Let us say the Euclidean distance between the ...
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If changing inertial reference changes velocity/energy, shouldn't that produce conflicting observations of gravity?

A particle $X$ has mass $m$ and passes above observer $A$ with an apparent horizontal velocity $v$. Colinear with these is another observer $B$ moving with apparent horizontal velocity $u$. Colinear ...
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Why does photon have to travel in sideways to hit the light clock?

From this article, Let’s say Alice is holding a light clock, and Bob is watching her run by, while holding it, with speed V. Alice is standing still (according to Alice), and the time,$ \tau$, ...
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Given the intervals of a punctured flat spacetime how to reconstruct the intervals of the complete flat spacetime?

A set $\mathcal S$ of events can be characterized as a flat unbounded spacetime through a function $s^2 : \mathcal S \times \mathcal S \rightarrow \mathbb R$ which assigns spacetime interval values to ...
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Calibration of a clock [duplicate]

I was inspired by this interesting question on this forum: How do I measure an earth year without a clock? Say you're stranded on an alien planet without any significant tools. How would you ...
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How is viscosity related to the forces in fluid?

I think it was that the forces are only perpendicular but do not know how this is related and from where it comes from. EDIT: I am asking for the difference between viscous and non-viscous fluid in ...
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Tensor as outer product

This is a problem I am trying to solve and need help with. Given a $ \left( \begin{array}{} 0 \\ 2 \end{array} \right)$ tensor h such that h$(\quad ;A)=\alpha $h$(\quad ;B)$ for any two vectors ...
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Finding the momentum of a muon in $\pi\to\mu\nu_\mu$ [closed]

The $\pi$-meson's mass is 139.57 MeV, and it decays into a muon and a neutrino. The muon has a mass of 105.4 5MeV, and a proper lifetime of $2.197 \times 10^{-6}$. The neutrino can be treated as ...
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Does relative velocity time dilation occur at any relative velocity?

The reason I ask this question is due to the fact that every example I've found is presented such that the relative velocity is "near the speed if light", or that it happens as the object " approaches ...
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Speed of light in vacuum - definition and Constancy [duplicate]

This question has been nagging me for sometimes now, and even after studying all those relativity still cannot find an appreciable answer. The speed of light is $c$ defined and measured as constant ...
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Relativistic spaceships moving towards each other

There are two spaceships, A and B, moving towards each other, such that they will eventually pass each other. At a point equidistant from both ships, their velocities are both 0.5c towards that point. ...
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What is the rigorous description of scattering in relativistic QFT?

The first conundrum is what picture of QM to choose, in order to describe such a scattering. Unlike in non-relativistic QM, in RQFT the three all-known pictures are not at all equivalent. The ...
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What will be destroyed? The Moon or the Death Star?

The situation: Suppose Death Star passes by the Earth towards the Moon (near speed of light) and fires its laser (starting from the center of Death Star) against the Moon. If the laser gets to the ...