# Tag Info

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Must admit, have found it sometimes difficult to justify why I did a PhD. Ideally because I have lust, errrr lust for knowledge Most subjects get more interesting beyond the undergrad degree level, it just seems natural for me to say physics is more interesting than other subjects. As well, with theoretical physics you develop mathematical skills and this ...

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Theory without experiment is mathematics. Experiment without theory is just doing random things. Perhaps there is a "fundamental truth" to nature, perhaps there isn't. Theoretical physics is independent of that, because theoretical models are what gives science predictive power. Theoretical models are things that give you formulae with which to ...

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The notations $\int f(r)\, dr$ and $\int dr\,f(r)$ are equivalent. The latter is convenient if you have nested integrals, e.g. $$\int_0^\infty dr\int_0^\pi d\theta\,f(r,\theta),$$ so that you can see which integration limit belongs to which integration variable. The notation $d^3r$ is a shorthand for "integrate over 3D space", for example $dx\,dy\,dz$ if ...

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From what I can see in your photo, it looks like you want to do this $$h_{\nu}^{\alpha},_{\mu \alpha}$$ which is h_{\nu}^{\alpha},_{\mu \alpha} EDIT: I think @NowIGetToLearnWhatAHeadIs is correct, the comma is on the subscript level (with $\mu{}\alpha{}$). Additionally, separating the $\nu$ and the $\alpha$ is possible by using the $\{\}$ characters. ...

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Electromotive force is not a mechanical force, but a driving electrical force for charges or the potential energy per unit charge stored in the electrical source. It can be seen as the work that can be done by the source to drive off electrons in a circuit, provided there is no internal resistance of the source. This potential is the gradient of the ...

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International Handbook of Research in History, Philosophy and Science Teaching quotes the English translation of Guisasola et al. (2008), which discusses some of the early history of the EMF. The man who coined the term "electromotive force" was Alessandro Volta, who stated that there was a force separating the charges in current flowing in a closed circuit. ...

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The problem is that many "human scale" phenomena are terribly difficult to treat: friction, fluid dynamics, vorticity, heat transfer... Even if they are ubiquitous in our everyday lives, these things are really difficult (and sometimes impossible!) to treat analytically. Just think about friction: the microscopic mechanisms behind this force that rules our ...

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In addition to the answer by dmckee and to answer the question how high in energy you could get a photon it might be worth thinking about 'Gamma Ray Astronomy' where the highest energy photons are detected. The record highest photon energy observed is apparently currently 80 TeV, which corresponsds to a wavelength of $1.5 \times10^{-20}m$ wavelength (if I ...

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Higher energy gamma and longer wavelength radio? Keep in mind that the different 'kinds' are merely human labeling conventions for a spectrum that is continuous in the mathematical sense. There is no feature of "radio" that distinguishes it objectively from microwaves. We just pick a boundary on the basis of some technological limitations that apply when ...

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Quantum teleportation is a concept of transferring quantum states of matter. Not teleporting matter itself. To "clone" an object to the destination, you need to have the same material as the object already prepared at the destination. You can teleport the state of the object to the destination (of course, purely talking in theory). Then you may be able to ...

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In almost every technical field, one of the key goals of an undergraduate degree is to prepare one to work as a professional in that field. Working as a professional physicist pretty much means having a PhD in physics. The key focus of an undergraduate physics degree is to prepare students to enter a graduate school program in physics. Excluding ...

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Most of the "intermediate scale" problems were "solved" long ago, and are now mostly the domain of engineering: application of physics to real world problems. I put "solved" in quotes: "real world" solutions require that you don't make all the simplifying assumptions that make many problems "solvable" - this is no such thing as a spherical cow. Nonlinearity, ...

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