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Just a coincidence. There are too many quantities and not enough letters. It probably does make a difference that the fields in which these two equations exist (material science and electromagnetism) are well enough separated that you typically won't see them both in the same papers or textbooks; if that weren't the case, people would start using different ...

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As a native English speaker, I don't even see three definitions. The first two sounded 100% the same all the way up until you wrote the third. At which point the first one sounded pretty meaningless. You could just say motion if you meant any possible motion. To do science we have to make predictions. Which means you predict that one thing happens as ...

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Boosting means you are changing a frame of reference; boosting frames doesn't imply any actual motion. When you talk about boosting, you are talking about changing the way you are observing something instantaneously. Acceleration on the other hand, is a type of motion inside a frame of reference. When you talk about acceleration, you are talking about a ...

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Yeah, that's just a coincidence. The easy way to see this is that $\epsilon$ is a relatively static property of a dielectric but a totally dynamic property of a stretching material.

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Engineers created that problem. ;) (probably not) Many physics books use $Y$ for Young's modulus (Symon, Knight, Young & Freedman). Taylor's Classical Mechanics uses YM. Halliday, Resnick & -fill-in-the-blank- state that engineers use $E$. I suspect that physicists started using $Y$ for exactly this reason: to highlight a difference in the meanings ...

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The (Lie-)group $U(1)$ is the topological space $S^1$ (what we call a circle together with its standard open subsets) together with a rule how to multiply its points. In its representation as numbers in ${\mathbb C}$ with absolute value $1$, we have ${\mathrm e}^{{\mathrm i}\alpha}\bullet{\mathrm e}^{{\mathrm i}\beta}:={\mathrm e}^{{\mathrm ... 2 Introduction In general, a Physical System State is described by a set of variables Let’s consider the “System Internal Energy” variable System States A System is said to be in its “Ground State” when it is at the lowest possible energy level Any other State is then an “Excited State” and they would correspond to energy level greater than the ground ... 2 The problem in answering this question is that the term wave itself is so loosely used to define that which we observe. But fundamentally a wave is just an expression of the flow of energy in time and space. It's observable evidence that energy is flowing. It's clear that traveling waves expresses the flow of energy. And the interference or superposition ... 2 The uses of this two theories are completely different. Statistical Mechanics is used to see how by modelling the behavior of microscopic constituents you can predict the macroscopic phenomenas that you observe. On the other hand Many Body Theory uses first principle techniques to see what happens microscopically when you have large no of particles in your ... 1 It is a method that is generally used for conservative unidimensional problems (problems with only one degree of freedom, here your angle$\theta$or cartesian coordinate$x$). You'll notice that it is equivalent to using Newton's second law in this case : let us write the total energy$E = \frac{1}{2} m v^2 + V(x)$,$V\$ being potential energy. The problem ...

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Consider the following model of an atom: Keep in mind that it is only a model and while it is a good model that elevates our understanding of the subatomic world, it is still just a model and reality will look different. How exactly? We don't know. The model is good enough, though, to understand what an excited atom is. With this caveat out of the way, ...

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Terms like "Father of Physics" (or "Father of Modern Chemistry", or "Mother of Computer Science") aren't official titles, they're just subjective opinions. No one appoints them. Calling Einstein the Father of Physics is like giving your dad a "Best Dad in the World" mug--it's a nice gesture, but no one ever did a survey of every dad in the world to ...

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Let's say you are doing a typical SR experiment and you have Alice and Bob flying around in spaceships and such and you have each ship feeding you data. Things outside look one way to Alice and a different way to Bob because of their inertial frames. Let's say they're observing two supernovas and trying to determine their timing relative to each other, and ...

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Excitation is an elevation in energy level above an arbitrary baseline energy state. "In English, please!" So what this is effectively saying is that an atom is considered "excited" when its energy level is higher than the rest. This can be manifested as heat, light, etc. For example, the Aurora Borealis. The Aurora is when radiation from the sun ...

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