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

learn more… | top users | synonyms (5)

0
votes
0answers
24 views

The wavelength of EMR reaching an orbiting ship at .99 c

In this answer John Rennie says that, if a ship is orbiting the Earth at .99 c: .. observer on the Earth sees time moving slowly for the astronaut, while the astronaut sees time moving fast for ...
-1
votes
1answer
49 views

Is the time dilation experiment for real?

A popular experiment is described in books on special relativity, that claims that an atomic clock was flown at high speed and later compared with a similar atomic clock on earth, and it was found ...
-2
votes
2answers
64 views

What particles travel near the speed of a photon?

I know photons travel at the speed of light. How does the size of a particle determine its maximum velocity? Phonons, Preons, Electron ect. Is there a scale in from the smallest particle's maximum ...
1
vote
2answers
69 views

Why does Special Relativity apply to more than just light?

It is my understanding that time dilation is derived from the constancy of the speed of light in vacuum. I would assume this implies that the quirky consequences would therefore apply only to light. ...
0
votes
0answers
20 views

Relativistic Mass and Potential Energy

In the chapter 16–4 of the Feynman Lectures, Feynman employs a thought experiment to explain why "if two particles come together and produce potential or any other form of energy; if the pieces are ...
2
votes
2answers
38 views

Pole and Barn Paradox w/ Spacetime Interval

I'm having trouble with a pole and barn paradox problem. The problem is as follows: A pole vaulter is running with a pole at $ v=\frac{\sqrt3}{2}c $. Her pole has a proper length of $L$. She runs ...
0
votes
0answers
24 views

Colliding beams vs static target

In this problem I need to find the threshold energy of a positron-electron collision that creates a Z boson (the reverse of the following picture; Z mass 92 GeV) in two distinct cases: collision ring ...
7
votes
4answers
2k views

Am I just some energy traveled at light speed? [on hold]

I don't understand $E=mc^2$ very well, and here is my question: Does this equation mean masses are just condensed energy? And does this mean that the extra energy an object has when traveling at ...
1
vote
1answer
49 views

Einsteins theory of relativity and formula of kinetic energy [duplicate]

After seeing both Einstein's theory of relativity ($E=mc^2$) and the formula of kinetic energy (K.E=$\frac{mv^2}{2}$), I noticed that that they are mostly the same, with the only difference that ...
2
votes
0answers
38 views

Is the helicity of photon Lorentz invariant?

If the helicity of a photon is $+1$ in an inertial frame, then is the helicity of this photon $+1$ in another inertial frame? The helicity operator is $$ h=\mathbf{S}\cdot\hat{\mathbf{p}} $$ with $$ ...
1
vote
1answer
74 views

Where is the mistake in the following rationament [duplicate]

Well... kind of hard to translate in English so bare with me :). Let's consider a wheel that spins in the void. Each point of the wheel has the speed $v = ω r$. That means that for any $ω$, there is ...
4
votes
2answers
152 views

Nature of light in Special Relativity

What is the nature of light in the context of Special Relativity? Is it a photon, or an electromagnetic wave, or something else? I have doubts, because a photon seems to me a quantum mechanical ...
-8
votes
0answers
36 views

is it possible to use c (speed of light) to validate a fourth dimension of space? [on hold]

Let's observe the orbital path of the moon around the earth if the earth were reduced to a single point of equal mass/gravity on a 2 dimensional plain. Now let's pause the moon and call that position ...
0
votes
2answers
63 views

Is time a coordinate or a parameter in Newtonian mechanics?

In classical (Newtonian) mechanics we only ever seem to consider 3-dimensional space, with physical quantities being represented by 3-vectors. My understanding for this is because in classical ...
1
vote
2answers
41 views

Motivation for usage of 4-vectors in special relativity

I understand that if one considers a 4-dimensional space-time from the outset then 4-vectors are the natural quantities to consider (as opposed to 3-vectors as in Newtonian mechanics), since the ...
3
votes
1answer
53 views

Relativistic correction to Hydrogen atom - Perturbation theory

Given the relativistic correction $$ H_1' = - \frac{p^4}{8m^3 c^2} $$ to the Hamiltonian (i.e. a perturbation), what does it mean when $[H_1', \mathbf{L}] = 0$? The book I'm reading says this implies ...
0
votes
0answers
52 views

Galileo's ship experiment with a laser pen instead of a rock

Ship's mast experiment with the boat moving at speed v: If a rock is dropped from the mast, then for an observer inside the boat they will see this: For an observer outside the boat and on the ...
-8
votes
0answers
57 views

Meaning of constant $c$ [on hold]

I have a puzzlement over Einstein's expression $E = mc^2$. The constant expressed as $c$ is the measured speed at which Light crosses a vacuuum. BUT it is also used to denote the maximum possible ...
0
votes
0answers
47 views

Speed of light interpretation [on hold]

I was wondering if any theory interprets the speed of light such that light needs to stay and visit some small open set for each tick of time? Then it could be renamed law of the good guest or ...
0
votes
0answers
39 views

Speed of the Coulomb Field Measured To Be “Infinite”

The paper "Measuring Propagation Speed of Coulomb Fields" by R. de Sangro et al points out that: ...the Lienard-Weichert retarded potential leads to the same formula as the one obtained assuming ...
0
votes
1answer
34 views

Momentum equation of a beam hitting a stationary target to create antiprotons

I'm struggling with the solution of a physics exercise which is to calculate the minimum energy needed to create antiprotons when a proton beam scatters on a stationary proton target: $$p + p ...
1
vote
0answers
58 views

Zeroth component of 4-momentum and relativistic energy-momentum relation

As I understand it one is forced to use 4-vectors since we require objects that transform as vectors under application of Lorentz transformations and 3-vectors do not (technically they do under ...
3
votes
1answer
67 views

Homogeneity and isotropy and derivation of the Lorentz transformations

In deriving the Lorentz transformations I have found (from reading a few different sets lecture notes) that it is argued that they must be linear and thus there general form must be $$x'=Ax+Bt,\quad ...
0
votes
0answers
26 views

Inertial coordinate systems [duplicate]

In Newtonian mechanics, by the following two assumptions: (i) The time is absolute. (ii) The length is absolute. it is easy find the relations betweem two coordinate systems with uniform motion ...
1
vote
2answers
73 views

Definition of the Lorentz transformations [on hold]

Until very recently I believed that the Lorentz transformations were defined as "the transformations that carry one inertial reference frame into another". In Wikipedia's page we find something along ...
1
vote
0answers
58 views

Path integral (sum over paths where $v>c$) [on hold]

The path integral formalism is used to get for example the propagator of particles. In this formalism we integrate over all mathematically possible paths (and weight them with the non-relativistic ...
2
votes
2answers
48 views

How do we determine if a certain physical quantity is a vector?

For instance in Newtonian physics we treat position of objects, displacements, velocities, forces, momenta, angular velocities etc all as vector quantities (little arrows in space which have a certain ...
0
votes
3answers
34 views

Frames of reference, relativity, and a ball thrown in the air

Ever since my high school physics days I found relativity fascinating but I don't think I have great insight even into special relativity. For example, in almost every lesson or video they give an ...
-4
votes
0answers
34 views

Formation of nucleus [closed]

Is it even remotely possible for a nucleus to be formed in the following way? Consider two nucleons approaching each other at extreme speeds. Could the relativistic increase in mass be so high to ...
6
votes
5answers
398 views
+200

Can you deduce absolute motion through magnetism?

Trying to understand magnetism I stumble into this example: Suppose there are two electrons travelling side by side in deep space (say, between Mars and Jupiter) at 1 cm distance at .99 c. In this ...
0
votes
1answer
52 views

Questions about null geodesic [closed]

Show for the null geodesic in 3D flat spacetime using polar coordinates so the line element is $ds^2=-dt^2+dr^2+r^2d\phi^2$. Do light rays move on straight lines? My question is that I only learned ...
2
votes
1answer
81 views

What is really sought when we purpose Einstein's postulates in Special Relativity?

Special Relativity can be motivated by looking at Maxwell's Electrodynamics and noticing that there is some kind of inconsistency between it and Newtonian Mechanics. Indeed, as Einstein pointed out on ...
5
votes
1answer
79 views

How to motivate the importance of the spacetime interval

The spacetime interval is a rather important thing in Special Relativity. It allows us to define the separation between any two events as spacelike, timelike or lightlike and more importantly, the ...
-3
votes
0answers
32 views

Difference in time for clock in attic vs clock in cellar [closed]

This question is regarding relativity: Two clocks are stationed in a house, one in the cellar and one it the attic. Which one of the following statements is true? A : The clocks tick at the ...
0
votes
2answers
100 views

What is the inconsistency between Maxwell's electrodynamics and newtonian mechanics?

As far as I understand, when a modification of a theory is made it is because some observation required this modifcation. Quantum Mechanics is a nice example of that: observations of microscopic ...
0
votes
2answers
65 views

Does contracted spring weigh more than stretched one?

(One of examples that potential energy contributes to mass.) Does hot object weigh more than cold one? (One of examples that kinetic energy contributes to mass.) If these are true and justified by ...
3
votes
1answer
65 views

Limits used to find non-rel limit of the Klein-Gordon equation

I just have a question regarding assessing the non-relativistic limit of the Klein-Gordon equation. In the book I'm following (Quantum Mechanics by Bransden & Joachain) they use the limits (Chpt. ...
3
votes
2answers
52 views

Classical Klein-Gordon theory is a free relativistic theory

The classical Klein-Gordon theory for a real scalar field is called a relativistic free theory. It is called a free theory because the dynamics of the degrees of freedom in the momentum space of the ...
0
votes
0answers
36 views

The derivation of the Mass-Energy(including mechanical energy) equivalence principle [duplicate]

(Not duplication! I couldn't find the answer for the general case, instead of the special case that I've already seen in Youtube I hyperlinked.) I will fully satisfy with not only a mathematically ...
1
vote
1answer
30 views

Livestreaming at near lightspeed [duplicate]

Please forgive me if this is a stupid question as I have a very rudimentary understanding of physics. I was reading about how the large hadron collider speeds up subatomic particles to near ...
1
vote
0answers
23 views

The mass-energy equivalence is a principle which can not be derived from anything? [duplicate]

Not duplication) I couldn't find the answer for the general case, instead of the special case that I already seen in Youtube I hyperlinked. I will fully satisfy with not only a mathematically ...
1
vote
1answer
82 views

Simulation of relativistic probe passing through an external solar system

I recently read about the Breakthrough Initiative to launch "StarShot", a nano-probe that is designed to travel to Alpha Centauri at $0.2c$. One of the challenges to be solved involves the precise ...
0
votes
0answers
32 views

Electron in a Magnetic Field: Force parallel to velocity?

According to the four-force given in this question, Force is parallel to velocity. But the Lorentz Force is perpendicular to velocity in a constant magnetic field. Is this a contradiction? [a ...
0
votes
1answer
64 views

Why do we not apply length contraction when finding out the time taken for objects moving at relativistic speeds?

I was going over a question on my own, then I took a brief look at the solution...it's basically about A rocket has a proper length of 250 m and travels at a speed v = 0.950c relative to the Earth. ...
1
vote
2answers
69 views

Twin paradox in special relativity: length contraction

Can the concept of twin paradox be applied to length contraction as well? meaning that the twin which is in spaceship will have its meter rod "actually" contracted while he will see his brother's ...
1
vote
0answers
19 views

Time Dilation for a photon [duplicate]

Does a photon experience any time. Since a photon is massless and hence travels at (c) then it should suffer infinite time dilation, and hence shouldn't experience no time?
0
votes
2answers
38 views

How to calculate the maximum speed of an object?

There is a spaceship, whose mass is $100 \, \mathrm{kg}$. The thrust of its rocket is $300 \, \mathrm{N}$. How is it possible to calculate the maximal speed that the spaceship can reach, and the time ...
0
votes
0answers
21 views

Lorentz invariance & Noether theorem of classical ED

I want to check invariance of the action under Lorentz boosts for classical electrodynamics. The action is $$S = \int \mbox{d}^4x F_{\alpha \beta} F^{\alpha \beta} $$ I assumed that the fields ...
1
vote
1answer
51 views

The Energy Equation

I've been studying the energy equation in relativistic motion $E= \frac{mc^2}{\sqrt{1-v^2/c^2}}$, which can be expanded as $$E = mc^2 + \frac{1}{2} mv^2\text{ + some other terms.}$$ I'm curious ...
1
vote
1answer
49 views

Which reference frame decides the relative velocity of two reference frames?

The following thought experiment is often used to introduce Special Relativity: The thought experiment fails to specify which reference frame establishes $\vec{v}$--the observer on earth or the ...