# 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.

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### Noether's theorem and energy in four-momentum

In Newtonian physics, momentum and energy are often treated as distinct entities, which happen to be separately conserved. In relativity, energy is regarded as the "time" component of the ...
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### Linearity of Lorentz Transformations from Principle of Relativity

Many derivations of the Lorentz transformations assume they must be linear maps on $\mathbb R^4$, where we identify the components of $\mathbb R^4$ with orthogonal coordinate systems associated to ...
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### What if the Twin Paradox use the "day time" and "night time" on earth as their age reference?

I've searched this site, I found a similar question here but not exactly like mine. So I can't understand the Twin Paradox when I use the "day" (bright time) and "night" (dark time)...
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### Can a massless particle travel along a timelike path [duplicate]

It seems to be generally accepted that massless particles always travel at the speed of light, but I have never seen any explanation for why that needs to be the case. What in our theories prevents ...
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### Lorentz-invariant Lagrangian for spinor field

Schwartz book on QFT (page 167), Zee book on group (page 461) and Maggiore book on QFT (page 55), prove that $\psi_R^{\dagger}\sigma^{\mu}\psi_R$ is a 4-vector, where $\psi_R$ is a right-handed spinor ...
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### Does any time dilation take place within an electrical conductor when electricity is flowing through it?

I am curious to know if any time dilation takes place within an electrical conductor when electricity is flowing through it. It is my understanding that an electrical current (electromagnetic waves) ...