# Tag Info

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All conservative phenomena (not laws), do indeed, take a finite time to propagate, therefore "information" can't travel faster than light. Also, just because phenomena take time to propagate, does not mean that the phenomena are not being conserved at any given instant of time. In fact, there is no moment, when the phenomena are not conserved!

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Others have explained that they don't propagate. That's a real puzzler though, and the real question is how does the stuff (energy, charge, whatever) always add up when a transfer takes finite time? The answer to figuring that out was a profound pillar of modern physics: the field contains momentum (etc.). So while an electron is handshaking with another ...

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Possibly in the slightly negative energy region of a Casimir mirror pair However, the effect is really small

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There may be scope in this question to mention the faster than light (FTL) capabilities of Tachyons (should they exist). If (in the language of Speacial Relativity) we apply the first postulate of SR to tachyons and there is an instantaneous transmission of information in one inertial frame then it would be true to say this occurs in all inertial frames. I ...

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Let's look at an example, electromagnetism. The electromagnetic field (the combination of electric and magnetic fields) has momentum. Charges have momentum. The charge feels a force right where it is, a force based on the fields right where it is. This changes the momentum of the particle. The field loses an equal and opposite amount of momentum and also ...

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See https://en.wikipedia.org/wiki/Continuity_equation - I was just writing some text there that I think helps explain. Continuity equations are a stronger, local form of conservation laws. For example, the law of conservation of energy states that energy can neither be created nor destroyed—i.e., the total amount of energy is fixed. But this ...

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Conservation laws do not propagate instantaneously (or really at all), it really means that some property of the system does not change over time. In the case of momentum conservation, the information about the collision propagates (at most) at the speed of sound in the medium. This is why you see the cars continuing along their path during a collision: ...

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Conservation laws don't "propagate". They are inevitable consequences of symmetries of the dynamics by Noether's theorem, and the dynamics propagate with whatever finite speed they do.

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Exactly what here is referred to be "faster than light?"  By fast than light it means that if you put a light beam to your left and to your right and you ball take off like racers running towards a take across a finish line that you get to the finish line first. And how does this work? Are you clumping together a punch of exotic matter at the ...

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I think the comment was talking about a race type situation. For instance if you had a 50m dash with a bunch of runner lined up horizontally and running towards a horizontal finish line with some tape across the finish line they could race and see who hits the tape first. It is exactly (and only that sense) that the warp drive arrives first. Let's say ...

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I was watching a Physics TV show, When someone called Alex Filippenko said that when there was the Big Bang, the Space extended at a speed faster than speed of light. He said that it wasn't against the theory of relativity because space isn't a particle and can go faster than speed of light. As far as I know it's true. Imagine space is like a stress ...

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Because there was no space around it, all matter has a speed barrier which is the speed of electromagnetic radiation in vacuum (and gravitons in case they exist) inside the space time fabric of our universe, the boundary of the universe doesn't have that limitation since there is nothing outside, at least that is the proposal to explain how the universe ...

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Okay, let's start with the basics. The Big Bang was not like an explosion in space from which spewed all matter in the universe. The Big Bang was a moment in time. We have this thing called a spacetime metric. I won't bore you with the details, but essentially it is the equation we use to describe all of the geometry in the universe. It includes all the ...

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The Alcubierre drive is like an escalator. Space expands behind the ship, and this is like the moving stairs coming out of the floor behind you, while space contracts in front of the ship, like the moving stairs disappearing into the floor in front of you. This is not, however, a description of the actual Alcubierre process. We live in de Sitter space, ...

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The possible room for the nasty alternative scenario mentioned in WetSavannaAnimal's answer has been worked out in detail in this article. When the OPERA experiment due to a flawed cable connection appeared to have seen faster than light neutrinos, it was possible to calculate that this was impossible, because the room there exists for Lorentz invariance ...

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I'd like to continue from Jims Bond's already comprehensive answer. Suppose that we had conclusive proof of our observation of a $V>c$ and that we've ruled out alternative (5) of Jim's answer. I agree with Jim that the next most likely of Jim's alternatives is: 2) We would be forced to conclude that $c$ is not the limiting speed of information ...

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To simplify things a bit assume small oscillations and a point-like mass. The relativistic Lagrangian for the 1-dimensional case is $$L = -\frac{mc^2}\gamma - \frac12kx^2.$$ The equation of motion turns out to be $$\ddot x + \frac13\frac1{c^2-\dot x^2}\frac{\text d}{\text dt}\dot x^3 + \frac{\omega^2}\gamma x=0,$$ where $\omega^2 = \tfrac km$. I haven't ...

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There is no such a thing as rigid body in real world as well as in the theory of special relativity. Hence a very large pendulum is impossible. For a string, Given the momentum of the pendulum has, small oscillation is impossible. For very large string, depends on how large it is, special relativity is defined on small scale, in a very large (~edge of ...

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There are two important reasons why this is impossible. For one, it is impractical. The gravitational pull would have to be so extreme that it would break the material used for the rope, or the length would be so long that it is under a weaker and weaker force of gravity as it gets farther away. Even if you had an unbreakable rope and an enormous mass very ...

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Light will never be completely at rest, but we have succeeded in slowing it down significantly. (See this for example) In a medium, particles can move faster than the speed of light. (The speed of light in that medium) In fact, this is used in some particle accelerators to detect certain particles. When a charged particle travels faster than the speed of ...

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I'm no expert but: you have to assume that you stand still in your initial system. And also because of these contractions it doesn't sum up straight v1+v2 (like the pre-answered said). There are other thought experiments like when you turn yourself and you look out in the universe, things can then pass way faster than light but only because your angular ...

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I think I see your mistake: it's the classic mistake. You would think that if you travel in a rocket moving at the speed of light and flash your flashlight out from it in the same direction the speed of the light would be $2c$ (where $c$ = speed of light), but in truth, due to time dilation and length contraction etc, etc, relative velocity would still be ...

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