# Tag Info

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SR: Flat Space-time (Minkowski metric), no gravity, Lorentz coordinates transformations (usually $\Lambda \in SO^+(3,1)$, the proper orthochronous Lorentz group). Acceleration is allowed, but you usually want to work with inertial frames. RG: Curved Space-time (non trivial and dynamic metric tensor), theory of gravitation, generic coordinates ...

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What is “special” and what is “general” in Relativity? The "special" in special relativity refers to the fact that it is not a universal theory. Predictions made by special relativity only apply under certain special circumstances. Those special circumstances are where gravitation is not present or can essentially be ignored. Initially I thought in ...

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Special relativity is physics in a $3+1$ dimensional Lorentzian spacetime, with the additional requirement that the spacetime is flat, which determines spacetime completely. General relativity is physics in a $3+1$ dimensional Lorentzian spacetime, with no additional geometric requirement. An equation for the metric is required to determine the spacetime, ...

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In special relativity the laws of physics are covariant under Poincaré transformation, whereas in general relativity the laws of physics are generally covariant, meaning that they take the same form under any smooth co-ordinate transformation. The Lorentz transformations are a special case of general transformations which is why we call them special and ...

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We say "superposition" when we talk about the adding of the amplitudes of two waves. Typically it is called "interference" when this adding results in an different waveform (for example, regions with no signal - like the fringes in Young's slits experiment). However really all interference is superposition, and all superposition is a form of interference.

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Interference is an effect of superposition. If you add two waves of close amplitudes, the interference picture will be the strongest. If one of the waves is of a much smaller amplitude, the resulting wave will be that of the highest amplitude, practically with no interference effect.

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The sling is not what makes it a trebuchet instead of a catapult. Catapults get energy from tension (usually torsion) and the arm hits a stop near the top of its arc to release the projectile. Trebuchets get their energy from gravity. The arm is off-center on an axle with the longer "launch" end (with or without a sling) holding the projectile and the ...

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The statement that special relativity is valid locally is equivalent to general relativity. This was indeed Einstein's initial logic. He realised that every point in spacetime has a local inertial frame. In other words a falling man feels no gravity - gravity is a fictitious force based entirely on your reference frame! Originally special relativity was ...

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"The Fabric of the Cosmos-Space, Time, and the Texture of Reality" by Brian Greene is the book which I read first to get introduced with GR and SR. Here is the brief passage to explain the general difference: In an empty unchanging universe-no stars, no planets, no anything at all-there is no gravity. And without gravity, spacetime is not warped-it ...

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Diffraction is the result of the influence of an edge on a wave. Behind every edge an electromagnetic radiation forms a fringe pattern. This is an intensity distribution and is called the interference pattern. Behind two close together lying edges (a slit) both EM radiation and water waves form intensity distributions. The only difference is that the ...

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The terms trajectory and orbit both refer to the path of a body in space. Trajectory is commonly used in connection with projectiles and is often associated with paths of limited extent, i. e., paths having clearly identified initial and end points. Orbit is commonly used in connection with natural bodies (planets, moons, etc.) and is often associated with ...

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