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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A list of inconveniences between quantum mechanics and relativity?
It is well known that quantum mechanics and (special and/or general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them?
E.g. ...
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9answers
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Can Maxwell's equations be derived from Coulomb's Law and Special Relativity?
As an exercise I sat down and derived the magnetic field produced by moving charges for a few contrived situations. I started out with Coulomb's Law and Special Relativity. For example, I derived the ...
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12answers
2k views
Is it possible for information to be transmitted faster than light by using a rigid pole?
Is it possible for information (like 1 and 0s) to be transmitted faster than light?
For instance, take a rigid pole of several AU in length. Now say you have a person on each end, and one of them ...
20
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6answers
2k views
Why is there no absolute maximum temperature?
If temperature makes particles vibrate faster, and movement is limited by the speed of light, then temperature must be limited as well I would assume. Why there is no limits?
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5answers
2k views
Do photons gain mass when they travel through glass?
Please correct me if I'm wrong, but I believe that photons slow down when travelling through glass. Does this mean they gain mass? Otherwise, what happens to extra kinetic energy?
I understand now ...
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2answers
633 views
Covariant Description of Light Scattering at a fastly rotating Cylinder
Let us consider the following Gedankenexperiment:
A cylinder rotates symmetric around the $z$ axis with angular velocity $\Omega$ and a plane wave with $\mathbf{E}\text{, }\mathbf{B} \propto ...
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1answer
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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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7answers
10k views
How can a photon have no mass and still travel at the speed of light?
I've read a number of the helpful Q&As on photons that mention the mass/mass-less issue. Do I understand correctly that the idea of mass-less (a rest mass of 0) may be just a convention to make ...
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4answers
3k views
Why does GPS depend on relativity?
I am reading A Brief History of Time by Stephen Hawking, and in it he mentions that without compensating for relativity, GPS devices would be out by miles. Why is this? (I am not sure which relativity ...
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4answers
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Einstein's postulates <==> Minkowski space. (In layman's terms)
What's the cleanest/quickest way to go between Einstein's postulates [1] of
Relativity: Physical laws are the same in all inertial reference frames.
Constant speed of light: "... light is always ...
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3answers
740 views
What is the length of 1 second in meters
If time is treated as a fourth dimension of spacetime, what is relation between length and time units?
Or in other words, how can I convert time units to length units, for instance seconds to meters?
...
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2answers
1k views
What happened to the idea of tachyonic or other superluminal neutrinos?
While hunting around for information about the recent OPERA measurement that hints at superluminal neutrinos, I discovered that this idea was actually considered back in the 1980s. Wikipedia lists as ...
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4answers
2k views
How is the classical twin paradox resolved?
I read a lot about the classical twin paradox recently. What confuses me is that some authors claim that it can be resolved within SRT, others say that you need GRT. Now, what is true (and why)?
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10answers
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Does the Pauli exclusion principle instantaneously affect distant electrons?
According to Brian Cox in his A night with the Stars lecture$^1$, the Pauli exclusion principle means that no electron in the universe can have the same energy state as any other electron in the ...
14
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5answers
682 views
Relativistic Cellular Automata
Cellular automata provide interesting models of physics: Google Scholar gives more than 25,000 results when searching for "cellular automata" physics.
Google Scholar still gives more than 2.000 ...
14
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1answer
326 views
a priori validity of $W=\int Fdx$ in relativity?
There are lots of different ways of arriving at the relativistic relations involving mass, energy, and momentum such as $E=mc^2$ and $m^2=E^2-p^2$ (the latter with $c=1$). One that I've seen in some ...
14
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2answers
654 views
Definitions: 'locality' vs 'causality'
I'm having trouble unambiguously interpreting many answers here due to the fact that the terms locality and causality are sometimes used interchangeably, while other times seem to mean very different ...
14
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1answer
542 views
Phase space volume and relativity
Much of statistical mechanics is derived from Liouville's theorem, which can be stated as "the phase space volume occupied by an ensemble of isolated systems is conserved over time." (I'm mostly ...
13
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2answers
557 views
Symmetrical twin paradox
Take the following gedankenexperiment in which two astronauts meet each other again and again in a perfectly symmetrical setting - a hyperspherical (3-manifold) universe in which the 3 dimensions are ...
13
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1answer
146 views
Is period of rotation relative?
My question is inspired by the following answer by voix to another problem:
"There is a real object with relativistic speed of surface - millisecond pulsar. The swiftest spinning pulsar currently ...
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4answers
453 views
Thought experiment regarding an object approaching a mirror
Here's a thought experiment I came up with in class today when my mind drifted (I however highly doubt I'm the first to think about this since it is pretty rudimentary) :
Let's say superman ...
12
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3answers
1k views
Electrons faster than speed of light
While looking at some exercises in my physics textbook, I came across the following problem which I thought was quite interesting:
It is possible for the electron beam in a television picture tube ...
12
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2answers
279 views
What does a sphere moving close to the speed of light look like?
What shape does the viewer in a reference frame with $v=0$ perceive? I suppose that since the sphere moves in one direction only (oX only, not oY) its section would change into an ellipse, where the ...
12
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9answers
444 views
How to explain (pedagogically) why there is 4 spacetime dimensions while we see only the 3 spatial dimesions?
I have been asked this question by a student, but I was able and in the same time incapable to give a good answer for this without equations, so do you have ideas how one can explain this in a simple ...
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5answers
858 views
Why did Einstein get credit for formulating the theory of special relativity?
See "The Principle of Relativity" here: http://en.wikisource.org/wiki/The_Principles_of_Mathematical_Physics This was written by Poincare in 1904, a year before Einstein published his theory of ...
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3answers
310 views
Are gravitomagnetic monopoles hypothesized?
My understanding is that gravitomagnetism is essentially the same relativistic effect as magnetism. If so, why is it that I've heard so much about magnetic monopoles, but never gravitomagnetic ...
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3answers
934 views
Is the universe a quantum computer - is light speed barrier a computational constraint
There is currently a debate ongoing on leading maths blog Gödel’s Lost Letter, between Gil Kalai and Aram Harrow, with the former arguing that building a quantum computer may not be possible due to ...
12
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3answers
858 views
Why the vacuum polarization does not decrease the speed of light?
On one hand, in the classical electrodynamics polarization of transparent media yields in lowering the speed of light by the factor of $n=\sqrt{\epsilon_r \mu_r}$ (refractive index).
On the other, in ...
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8answers
986 views
The Four-Clock Special Relativity Conundrum
Two open-car trains approach each other at fixed velocities. Each has a radar to see how quickly the other train is approaching, but apart from that the trains have no a priori knowledge of each ...
11
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4answers
376 views
Is there an easy way to show that $x^2-t^2=1/g^2$ for a (relativistic) body undergoing acceleration g?
A professor asked me about the (c=1) equation:
$$x^2 - t^2 = 1/g^2$$
which I used in a paper. Or with $c$:
$$x^2 - (ct)^2 = c^4/g^2.$$
I told him that it was the exact equation of motion for a ...
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2answers
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Is kinetic energy a relative quantity? Will it make inconsistent equations when applying it to the conservation of energy equations?
If the velocity is a relative quantity, will it make inconsistent equations when applying it to the conservation of energy equations?
For example:
In the train moving at $V$ relative to ground, ...
11
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6answers
1k views
Is the Planck length Lorentz invariant?
The planck length is defined as $l_P = \sqrt{\frac{\hbar G}{c^3}}$. So it is a combination of the constants $c, h, G$ which I believe are all Lorentz invariants. So I think the Planck length should ...
11
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3answers
319 views
Do particles have different spins in different frames of reference?
Let's say we have two photons, whose momentum vectors point to opposite directions. Also spin angular momentum vectors of the photons point to opposite directions. (Sum of spins is zero)
Now we ...
11
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2answers
598 views
A simple pendulum moving at a relativistic speed - how does the period change?
I've been pondering the precise mechanism of time dilation for the example of a simple pendulum in two different situations:
The observer and ground are at rest in one frame of reference; the ...
11
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1answer
184 views
Can the CPT theorem be valid if Lorentz invariance is only spontaneously broken?
Earlier, I asked here whether one can have spontaneous breaking of the Lorentz symmetry and was shown a Lorentz invariant term that can drive the vacuum to not be Lorentz invariant. How relaxed are ...
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13answers
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What are the mechanics by which Time Dilation and Length Contraction occur?
What are the mechanics of time dilation and length contraction? Going beyond the mathematical equations involving light and the "speed limit of the universe", what is observed is merely a phenomenon ...
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4answers
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Travelling faster than the speed of light
Let's say I fire a bus through space at the speed of light. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus will I in fact be traveling faster than the speed of ...
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9answers
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Accelerating particles to speeds infinitesimally close to the speed of light?
I'm in a freshmen level physics class now, so I don't know much, but something I heard today intrigued me. My TA was talking about how at the research facility he worked at, they were able to ...
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5answers
1k views
How do photons travel at a speed that should be impossible to attain?
If it requires infinite amount of energy to travel at the speed of light then how photon attains this speed? Its source is never infinitely sourced.
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2answers
271 views
Limitations on how far one can travel in the universe
Someone once incorrectly told me that, given the speed of light is the speed limit of the universe, aliens would have to live for hundreds of years if they are to travel distances of hundreds of light ...
10
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5answers
105 views
How large is the universe?
We know that the age of the universe (or, at least the time since the Big Bang) is roughly 13.75 billion years. I have heard that the size of the universe is much larger than what we can see, in other ...
10
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4answers
2k views
Einstein's special relativity beyond the speed of light
Could someone with access to this paper which claims to have new transformations between frames with relative motion faster than light which are supposedly consistent with special-relativity, say what ...
10
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2answers
224 views
The derivation of the Belinfante-Rosenfeld tensor
It seems me that there is a "difference" (at least apparently) in how the Belinfante-Rosenfeld tensor is thought of in section 7.4 of Volume 1 of Weinberg's QFT book and in section 2.5.1 of the ...
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2answers
273 views
Does relativistic mass have weight?
If an object was sliding on an infinitely long friction-less floor on Earth with relativistic speeds (ignoring air resistance), would it exert more vertical weight force on the floor than when it's at ...
10
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4answers
342 views
The definition of an inertial reference frame in Einstein's relativity
I'm reading Sean Carroll's book on general relativity, and I have a question about the definition of an inertial reference frame. In the first chapter that's dedicated to special relativity, the ...
10
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1answer
603 views
How realistic is the game “A slower speed of light”?
The game "A slower speed of light" from MIT claims to simulate effects of special relativity:
Visual effects of special relativity gradually become apparent to the
player, increasing the ...
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2answers
697 views
Is the “How to break the speed of light” minute physics video wrong?
I am referring to this video, on YouTube, by minutephysics, which has quite a lot of views.
In the video it states that if you flick your wrist while pointing a laser that reaches the moon, that the ...
9
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6answers
490 views
Proving that interval preserving transformations are linear
In almost all proofs I've seen of the Lorentz transformations one starts on the assumption that the required transformations are linear. I'm wondering if there is a way to prove the linearity:
Prove ...
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7answers
652 views
Does the discreteness of spacetime in canonical approaches imply good bye to STR?
In all the canonical approaches to the problem of quantum gravity, (eg. loop variable) spacetime is thought to have a discrete structure. One question immediately comes naively to an outsider of this ...
9
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2answers
349 views
Essential background for QFT study
The preface to Mark Srednicki's "Quantum Field Theory" says that to be prepared for the book, one must recognize and understand the following equations:
$$\frac{d\sigma}{d\Omega} = ...
