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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Proof of Lorentz contraction?

The measurement of the flux of muons at the Earth's surface shows that many more muons are detected than would be expected, based on their mean half-lifetime of 2,2 microseconds. This is a good proof ...
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Only one invariant speed in special relativity

This is taken from Rindler's Special Relativity: Any effect whose speed in vacuum is always the same could have used to derive the Lorentz Transformation, as light was used in our derivation. Only ...
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Homogeneity of the Lorentz Transformation

The standard Lorentz transformation is linear and homogeneous. This fact implies the following: $\Delta t'= \gamma\ (\Delta t - \frac{v \Delta x}{c^2}),\ \Delta x'= \gamma\ (\Delta x - v \Delta t),\ ...
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At what velocity would a body need to travel at to experience noticeable (couple minutes) time distortion?

When a person experiences higher speeds, the light must travel a greater distance to reach the person whom is moving compared to that whom is staying still. Right? So therefore, light takes slightly ...
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Why does the thought experiment of a photon bouncing of a mirror imply anything for other objects?

Okay, so I am reading a book, "The Elegant Universe" by Brian Greene, which talks about motion and its effect on time. Greene makes the point that time changes with motion by saying that if you have ...
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I'm having trouble interpreting the Lorentz transformations

There are two frames which I will call O and O'. Suppose I'm someone in O. Are the lorentz transformations a means by which to calculate coordinates on O' in a way that only frames like me would ...
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What is Minkowski spacetime?

I was browsing through an article on spacetime when I caught the words Minkowski Spacetime. A Wikipedia search brought me an article too complex for me to totally understand. So what is Minkowski ...
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1answer
139 views

Special Relativity & QuickSilver from X-Men

In the movie X-Men: Days of Future Past, the mutant character Quicksilver possesses the ability to move very fast. A particularly memorable scene in the movie is one where he runs around very quickly ...
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Do tachyons move faster than light?

I am trying to understand whether or not tachyons travel faster than light. The linked Wikipedia page shows some seemingly contradictory statements, and they are confusing. For instance, the first ...
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Simple relativity question

I have a simple question in foundation SR that I hope someone can clarify. Given a mirror of length l travelling at a relativistic speed wrt a 'stationary' frame of reference containing two laser ...
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142 views

Origin of the Lorentz force from the point view of relativity?

I'm a physicist, when I'm working on the quantum spin hall effect, I recollected the high-school knowledge on Lorentz force and try to explain the origin of it, but didn't get it in the first glance. ...
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140 views

Does matter become energy at the speed of light? [closed]

According to modern physics, we can't push matter to the speed of light. It would slow down (relative to its environment). But theoretically, if matter were to travel the speed of light, would it ...
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125 views

States in light cone string theory

Currently I'm trying to understand string theory in the light cone quantization. I just have had a look into Polchinski (Vol. 1, Introduction to the bosonic string), because – as far as I could see – ...
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51 views

Can relative speed be faster than c [duplicate]

If there are two spaceships moving away from each other(in opposite directions) at a speed 0.6c, then wouldnt that make the relative speed of one from the other's frame of reference 1.2c? Does this ...
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19 views

A theoretical speed of light question [duplicate]

This is a hard question to explain so bear with me. Let's say that Earth is moving at 1/3 the speed of light to the 'right' (obviously I realize there is no constant left or right). If I were to ...
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2answers
66 views

During relativistic effects what would a person feel experiencing length contraction?

It has been determined that when accelerating a mass towards light speed it gains mass, experiences length contraction, and time dilation. During such a period of special relativity what would a ...
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63 views

How fast does an object have to be going to turn into energy [closed]

Albert Einstein's equation, $E=mc^2$, says that an object has to be going at the speed of light squared to turn into energy. How fast would this be in miles per hour?
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Is it possible that the geometry of spacetime isn't Minkowskian, if we only take special relativity into account? [duplicate]

If you don't consider general relativity, could you say that the geometry of spacetime might be different from how it's specified by the Minkowski metric? Or is Minkowski spacetime the only geometry ...
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1answer
49 views

Is there experimental evidence of time order inversion for spacelike events?

The title sums up the question. Given two events separated by a spacelike interval, say one takes place after the other in an inertial frame, then by a suitable boost we may invert the time order of ...
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Can surrounding masses influence the speed of time (excluding the time dilation due to gravity)?

https://www.youtube.com/watch?v=ev9zrt__lec @6:22-7:22 If you removed the middle and front spaceships, will the time of the last spaceship flow differently? As this is what it appears to suggest.
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What is the relation between $\eta^{ab}x^2$ and $x^ax^b$?

What is the relation between $\eta^{ab}x^2$ and $x^ax^b$? Here $\eta$ is the Minkowski metric in $d=4$ and $x$ is a 4-vector. In particular, a tensor like $$x^a x^b x^c (\eta_{ab}x^2 - x_ax_b) ...
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74 views

Is it correct that whenever energy change, mass also change?

Can I simply claim that, according to the mass-energy equation $E=mc^2$, whenever the energy of an physical object (not necessarily a microcosmic one) changes, its mass also change? Okay, I ...
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44 views

What is the factor that controls the speed of electrons accelerating in vacuum?Won't they accelerate infinitely? [duplicate]

We all know that speed of light can not be exceeded. So the question is if electric field accelerates electron in a vacuum tube with enormous length won't the electron accelerate till a point where it ...
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89 views

Special relativity thought experiement

Say you see a spaceship moving relative to you. On this ship you see a timer. When a beam of light is emitted from one end of the ship the timer starts. When the light reaches the other end of the ...
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Spin of vector boson in higher dimension

A vector boson $V^{\mu}, \mu = 0,...,3$ has spin 1. To my understanding (correct me if I'm wrong) this is because it transforms as a 4-vector under Lorentz transformation $SO(1,3)$. So the $\mu = ...
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Is special theory of relativity compatible with quantum mechanics? [duplicate]

Is special theory of relativity compatible with quantum mechanics? If yes, which is a good starting book which deals with this ? "Bird is bird. Knife is knife. Death is death." So special theory of ...
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How would an observer distinguish between space and time in a “Lineland” universe?

Note: "Lineland" here is borrowed from the Flatland novella. If you were placed as an observer inside a "Lineland" universe, i.e. a Minkowski spacetime that has one space dimension and one time ...
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What is the relation between a basis transformation and an induced transformation $\psi(\Lambda^{-1} p)$ on the wave function? [closed]

I'm having trouble understanding why is $\psi(\Lambda^{-1}p')$ the correct wave function in the Lorentz transformed frame $p' = \Lambda p$. Suppose the state in frame $O$ is given by $$ ...
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28 views

Faster than light travel at half speed [duplicate]

Peter and Susan are facing each other in outer space. Both of them ignite their their incredibly powerful jet pack thrusters and accelerated away from each other to just over half the speed of light. ...
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132 views

Does light itself experience time dilation?

This seems weird for me. Every time I see light, I will think, "Hey, that light travels from the past far away from us!" Correct me if there is misconception.
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Is it possible to not move?

Whenever we consider velocity, it is always from a frame of reference. This means that if I am travelling .5c, I'm travelling at a speed between the speed of light and my current frame of references' ...
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1answer
54 views

What are the differences between special and general relativity? [duplicate]

What are the differences between special relativity and general relativity? I am looking for a naive, non-mathematical explanation.
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How is it possible for the wavelength of light to change in a medium?

So my physics class has just finished a long unit on optics while at the same time I've been trying to teach myself relativity. I admit my understanding is probably rudimentary, but I figured all the ...
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Four-vectors and metric tensor

I think it's safe to say that if $x^\mu=(x^0,x^1,x^2,x^3)$, then $x_\mu=(x^0,-x^1,-x^2,-x^3)$. But I don't really understand why one follows from the other. Could someone explain? Also, I've been ...
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Relativity Paradox involving two charged particles

Suppose there are two charged particles separated by some distance $d$ both with an equal positive charge of $q$. The particles also have equal masses of $m$. $m$ and $q$ are chosen so the ...
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$? = mc^{1.9}$ makes me crazy [closed]

If energy equals mass times the speed of light squared, what is mass times just under the speed of light? It's not energy,,,yet. Michio Kaku said in a physics video that the faster mass goes, the ...
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If tachyons existed, would we notice them?

In special relativity the space-time can be seen as a static four-dimensional picture that contains the entire past and the future of a flat universe. And the patterns in it are subject to several ...
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What is the role of the spacetime algebra?

For Minkowski space $M^4=\mathbb{R}^{1,3}$ the Clifford algebra $Cl_{1,3}$ (Dirac algebra) with $\{\gamma^\mu, \gamma^\nu \}=2 g^{\mu \nu}$ is sometimes called "spacetime algebra". What is its ...
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Finding Casimir operators for the Poincare group $ISO(1,2)$

I was asked to write the generators for translations and Lorentz-transforms in 1+2 dimensions and then to find the Casimir operators. For the generators I can take the same ones as in 1+3 case ...
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Measuring speed of an object relative to what? [duplicate]

I understand that everything in the universe is moving through spacetime and the spacetime vector is equal for all the objects. So if If something is moving at speed of light, the mass of it is zero ...
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1answer
297 views

What does v=c in the Lorentz transformation for time tell us?

For the simpler cases as boost in the x-direction, the time dilation formula following the Lorentz transformation for time is $$\Delta t'=\gamma(\Delta t-v\frac{\Delta x}{c^2})$$Now, we observe that ...
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What “is” energy in sub-atomic particles?

This question may be simple or not, I don't know but I can't find the answer anywhere. The electromagnetic spectrum is the range of light particles in different wavelengths and is supposed to be ...
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If I am a light travel around Earth, what relativistic phenomenons do I have?

In school, or even in university, we are only taught Lorentz transformation in one direction. It is quite easy: $$\begin{align} t' &= \gamma \left( t - \frac{vx}{c^2} \right) \\ x' &= ...
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How would I relate $\Lambda=e^{-i\omega_{\mu\nu}J^{\mu\nu}/2}$ to the Lorentz boost matrix?

$\omega_{\mu\nu}$ contains infinitesimal parameters and $J^{\mu\nu}$ contains generators of boost and rotation. Any 4-vector transforms as $p^\mu=\Lambda^\mu_\nu p^\nu$. Starting from given ...
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Definition of a symbol $s_{NN}$ appearing in particle physics

What is the meaning of $s_{NN}$ in particle physics? See e.g. here http://www4.rcf.bnl.gov/brahms/WWW/thesis/karabowicz_phd_thesis.pdf page 18 in the pdf. What is its relation to energy? I ...
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What are the effects of increased mass on persons traveling at near light speed?

It's been a long time since I studied physics (and then only very superficially), so please bear with my gross naivete. This question's been running around in my head for about two weeks now, and I ...
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light falling on a completely reflecting friction less mirror

If you had a perfectly reflective mirror whose face was perpendicular to the ground and was kept on a friction less track on the ground, and you shined a flashlight on it, what would happen? Would ...
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Trying to understand relativistic action of a massive point particle

I got badly lost in derivation of relativistic formulas for energy and momentum. I stumbled upon relativistic action as follows (which should explain relativistic motion of a classical particle): $$ ...
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Spacelike to timelike four vectors

First at all, let me just say that I'm not a Physicist, I study mathematics. So, I have this question. If you have a spacelike four vector, is there any transformation that could change it to be a ...
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Causality and Simultaneity in special relativity

I am a little confused about the implications of special relativity on causality and simultaneity. Are the following two statements true? For two events A and B that are close enough in space and ...