# Tag Info

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Mathematically, yes. Physically, no. Tachyons are a sign of an unstable theory and need to be dealt with. tachyons are these weird particles which move faster than the speed of light. Special relativity tells us that mass tends to infinity as an object's velocity tends towards light speed i.e. $$m = \frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}},$$ which as ...

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If you get accelerated forces act upon you. Therefore you can tell exactly that it is you who accelerates and not the whole universe.

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I agree with Симон Тыран. "If you get accelerated forces act upon you. Therefore you can tell exactly that it is you who accelerates and not the whole universe" To answer the follow-up comments - Even if we can not distinguish between who has actually accelerated, the body that is accelerated, does feel the acceleration. And clock speed is influenced by ...

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One of the premises of special relativity is that observations made in different non-accelerating (or "inertial") frames are equally valid, and that there are certain quantities that all such observers agree on. One such quantity is the proper acceleration $\vec{a}^2-a_0^2$. All inertial observers agree on whether an object is accelerating or not. This ...

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Why do we have a universal speed limit? Is there a more fundamental law that tells us why this is? The more fundamental laws are causality and locality. Causality expresses the fact (or assumption) that effects cannot precede causes, and locality expresses the fact (or assumption) that fundamental causal relations are described by differential equations. ...

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This an attempt to give a more detailed explanation since the question really is quite fundamental and has mostly been explained by referring to the impossibility of a co-moving observer detecting any effects of the non accelerated linear motion whatever the speed might be. Its the same as saying you must just trust Einstein without explaining the mechanism ...

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You seem to be asking two things, could a black hole's magnetic fields cool nearby matter, and could this cooling produce cold fusion. But maybe we should first ask whether "cold fusion" is a real thing. Nuclei contain protons and neutrons held together by pions. Fusion is when two nuclei become one. The barrier to this happening, is the positive electric ...

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Prologue This is a work in progress - in particular the third section on the arrow of time could be improved. All suggestions for improvements are welcome. This a community wiki answer so anyone should feel free to edit it. However if you want to make large changes, e.g. completely rewrite a section, please post the revised text as a separate answer and I ...

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The laser pen will point in the same direction for the moving observer, but the light ray will emerge at an angle. So the direction of the light ray won't be the same as the direction of the laser tube. To see why this is imaging looking at a single pulse of light as it travels along the laser pen towards the aperture: From your perspective, with the ...

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Honestly, nobody has the answer. I spent hours every day to search for answers after the question was posted. I never find a beginning of independent explanation to "why there is a speed limit ?". The constancy of speed of light was postulated after Michelson-Morley experiments. The theory is consistent after a century of observations. When comes the time ...

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