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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Why is light different than sound in terms of the assumptions we make regarding causality?

I am having trouble understanding, from a conceptual point of view, why it would be impossible to travel faster than the speed of light. I have read one explanation given in the form of an example ...
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Einstein's space-time theory [closed]

I'm a high school student who never studied any relativity before, but I'm just wondering what was THE question that Einstein asked himself before going into this field. I knew he has done lots of ...
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The Relativity of Simultaneity and its Impact on “Seeing” Events

Will the rocket really see the supernova L first for sure? The position of the rocket is not specific. We just know that it is at the left of the galaxy. We know that R will explode first in the ...
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Length Contraction Confusion

i'm having a bit of trouble wrapping my head around special relativity, so i'd like to explain what I think is going on, to see whether or not I have understood. The question i'm thinking about is ...
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Does Special Relativity require a “ruler postulate” analogous to the “clock postulate”?

It's fairly well known that the clock postulate is needed in Special Relativity when dealing with accelerated clocks, so does something analogous exist when dealing with accelerated spatial ...
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Consistent answers in special relativity [closed]

I was doing a question about if a train fits in a tunnel. From the train frame it does not and from the tunnel frame it does. Then the question asked are these two answers consistent? What does this ...
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Can matter be annihilated to form kinetic energy

I don't know much about conversion of energy and all, but I had a simple question: Can the energy released by converting matter into energy be used to set other particles in motion (increase their ...
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Question from Griffiths (EM): Synchronized clocks

There's this vague conceptual question from the textbook Introduction to Electrodynamics by David Griffiths Problem 12.5 Synchronized clocks are stationed at regular intervals, a million km apart, ...
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Spin of an operator in supersymmetric theories

How exactly is the spin of an operator in the context of a supersymmetric theory defined? For example, in page 25 of [1], $\mathcal{N} = 2$ supersymmetry is defined to have operators $J, G^{+}, G^{-}, ...
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Scalar products in the spinor helicity formalism

In A. Zee's book Quantum Field Theory in a Nutshell (2nd edition), Chapter N.2, page 486, the momentum $p$ is written as a $2\times 2$ matrix: $$ p_{\alpha\dot{\alpha}} = p_{\mu} ...
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Using Special Relativity in Uniform Circular Motion [duplicate]

Can one utilize the formulas of Special Relativity in uniform circular motion? The radial component of the object does accelerate, but sometimes we are just interested in its tangential speed. Here ...
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About the relativistic wagon simultaneity problem

I'm getting utterly confused with this problem. The situation is basically to know what events to take in one frame in order to see them synchronized in another. I sketched the situation as this: ...
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Problems when a disc is rotating at extreme speeds (theory)?

I was wondering the problems that would occur (aside from mechanical friction), when a disc rotates at high angular velocity. Is centripetal force an issue if high torque is applied on a disc ...
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Time Dilation Geometry

I was recently exploring time dilation from Gravity and from velocity and I came up with an interesting derivation that I have not seen before. I was wondering if there is a paper published showing ...
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What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...
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How can I calculate the time dilation factor for velocities as low as 10 m/s? [closed]

I need to calculate time dilation factors; I tried using my calculator but for some reason my calculator cannot go that low when the velocity is on the order of 10 m s-1. What mathematical techniques ...
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Perceived direction of light emitted in moving reference frame

I was thinking the other day about the simple example used to demonstrate time dilation effects and to derive the Lorrentz factor - where the time it takes for a light pulse to be emitted, bounce of a ...
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Is Helicity an intrinsic property of massive Neutrinos?

Hyperphysics states that, unlike an electron, the helicity of a neutrino is invariant because we cannot change to a reference frame where it is different: This and subsequent experiments have ...
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Lorentz transformations: Which coordinate system is marked?

I am confused about a basic special relativity question. So we have the Lorentz transformations $$\begin{align} x' &= \gamma(x-ut) \\ t' &= \gamma(t-ux/c^2)\ , \end{align}$$ where frame $S'$ ...
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Why photon only have helicity other than spin? [duplicate]

When learning angular momentum in quantum mechanics, a spin 1 particle have 3 states. Then I saw from sakurai's modern quantum mechanics that photon's two polarization are just like spins, but with ...
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Time slowed by gravity

If time moves more slowly on Earth (due to our proximity to a gravitational body) than for someone orbiting Earth in a spaceship, yet the opposite occurs in the frequently cited "twin paradox" of the ...
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Why is coordinate time frame dependent? [duplicate]

Here is what I understand by coordinate time. It is the time difference measured between two events, using two synchronized clocks, one present at each event, and the difference is measured in an ...
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Is there a mathematical reason that the Lagrangian is Lorentz invariant?

The Hamiltonian is directly related to the energy, which is just one component of a four-vector and therefore not Lorentz invariant. The Lagrangian is the Legendre transform of the Hamiltonian and I ...
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Can the Cosmos itself be assumed as a reference frame?

Einstein believed that there are no reference frame in the universe in accord to his Special Relativity (SR). Now imagine a man, as the first observer, and his cat, as the second, are both at rest in ...
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Vector spaces for the irreducible representations of the Lorentz Group

The definition of a representation is a map to the space of linear operators over a vector space. My question is: What are the corresponding vector spaces for the $(0,0)$ Representation ...