# Questions tagged [special-relativity]

The special theory of relativity describes the motion and dynamics of objects moving at significant fractions of the speed of light.

5,801 questions
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### Wigner-Eckard theorem in 3+1 Minkowski dimensions

From this source, I have: I cannot find much (if not any) information online for Wigner-Eckard in 4D, hyperboiloid harmonics etc. And there are many facts just states in this source that I would ...
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### Converting an invariant matrix to a non-invariant tensor

I'm working on the following problem: In 4-dimensional notations, given a transformation matrix Calculate the matrices $\Lambda_{\mu\nu}$, $\Lambda_\mu^\nu$ and $\Lambda^{\mu\nu}$ The ...
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### The Necessity of Light for the Synchronization of Clocks in Special Relativity

In Einstein's paper, "On the Electrodynamics of Moving Bodies" light is used to synchronize the clocks of two different points in space. Thus if a frame S' is moving relative to frame S, an observer ...
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### Einstein's frozen wave?

Here's the quote from Stephen Hawking's latest book. At the age of sixteen, when he (Einstein) visualised riding on a beam of light, he realised that from this vantage light would appear as a ...
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### $(1,1)$ representation of $SL(2,\mathbb{C})$

How do you prove that the $(1,1)$ representation of the $SL(2,\mathbb{C})$ group acts on symmetric, traceless tensors of rank 2?
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### Showing the Lorentz-Fitzgerald length contraction

I'm trying to show that if we have a rod of length $L$ that is at rest wrt the inertial frame $K$, and we have a observer $K'$ moving wrt $K$ with speed $v_0$ in the direction along the length of the ...
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### Does the inertia of an object changes with its temperature? [closed]

$F=ma$ is not accurate enough at relativistic speeds. Does the inertia of a rigid body related to its temperature?
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### A Non-Velocity Dependent 4-Vector Transformed as Velocity Dependent 4-Vector

I would appreciate it if someone could explain the following: It is understandable that the Minkowski space Gauss' and Ampère-Maxwell equations in index notations \partial_{\nu} F^{\...
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### What if a spaceship going half the speed of light turned on its headlights in both directions?

If the spaceship, travelling at c/2 were to turn on only its forward facing headlights, then after one second (relative to us, the stationary external observers) we would see that the ship has moved ...
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### information theory and energy mass relationship (E=mc2) - just a hunch … [closed]

I was walking on the street the other day and thought to myself, maybe E=mc2 can be derived from information theoretic principles. I did not do too much work on this, just want to brainstorm a bit. ...
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### Do lengths contract or expand due to relativity?

Ok I have a simple question. We consider two frames, one is $F$ which is at rest and one is $F'$ which is moving with $v_0$ in the $+X$ direction with respect to $F$. Suppose a rod is at rest in $F$ ...
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### Space time diagrams : Length contraction

I am trying to get a better understanding for length contraction in a geometric sense and came across this diagram: but what I am having trouble with is why in the ref frame of the blue vector ...
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### What happens to a uniform electric field when a point charge is sent moving in a direction neither parallel nor perpendicular to the field?

If you have two reference frames, one where a charged particle is stationary but in a uniform electric field, and another where the system is moving at speed $\vec v$ in a general direction (neither ...
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### A bus and a ditch - an extension of the barn ladder paradox [duplicate]

Suppose, a bus is travelling with constant velocity in a straight road, and there is a ditch in front of it. Suppose, the rest length of the bus and the ditch are equal. Suppose the speed of the bus ...
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### How do we know that light cannot travel faster than it does?

We assume the speed of light in vacuum is its maximum speed but can we not assume that it could be faster, or slower?
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