# Tag Info

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The shape of the spout of your milk jug makes the milk from the edges flow towards the center - but as this means that the profile is trying to get narrower, the milk "has to go somewhere" and makes the jet wider in the other direction. However, surface tension is pulling back on the liquid (it would prefer the jet to be a perfect circle) so the liquid ...

2

Obviously darkness of lake water depends on depth of lake, impurity in water and many other things. But my answer to the question What causes the surface of lake to appear darker in some places? is Its depends on two things, [1] Position of observer [2] Position of sun in the sky. If sun is nearer to horizon then the amount of light, reflected from ...

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It is an interplay between the wind and the shoreline, and basic laws of reflection. As you can see in your photo, where the water surface is still, you see a reflected image of the skyline - lighter for the sky, darker for the buildings. Where the water surface ripples, you get reflections "from everywhere" - some from the sky, some from buildings, etc. ...

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It depends. It could be wind, simply the lighter section is rougher and the waves scatter light back to you while the flatter section appears darker because the light is scattered in a different direction. It can also happen where waters mix. A fresh water stream merges into an ocean, a flowing river meets a shallow stagnant area or (as below) river water ...

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Here is a link to the paper - within another doc. http://www.xtal.iqfr.csic.es/Cristalografia/archivos_10/Bragg-firstpaper-mini.pdf

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The Weights and Measures Act (the origin of the Imperial Units) does not speak of temperature. It was intended to create a uniform system for trade. You don't sell temperature, in the way you sell a pint of milk or a yard of cloth. And frankly, when it was first conceived (before Magna Carta, which already stated: "There shall be but one Measure ...

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According to the wiki page on Imperial and US customary units Fahrenheit is part of both the Imperial and US customary system. I can't think of any reason it wouldn't be included in the Imperial system. Note that in the wiki page on Imperial units it is mentioned that the weight's and measures act (which defined the Imperial system) explicitly used the ...

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Use Google Scholar search! It turns up the paper when searching for 2012 J. Stat. Phys. 148 513-547 or even J. Stat. Phys. 148 513-547 Barring a good academic search engine, a longer route is using something like Web Of Knowledge or Scopus, but those both need subscriptions which, in light of Google's excellent search engine, seems a bit daft. A third ...

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My understanding is this. I invite a discussion on this answer. While pouring the milk from the glass, Lets say "N" milk-molecules is reaching the air in the open space say "S". As the milk is more viscous fluid the milk-molecules are interested in coming as close to each other and hence it converges and hence the space in which the milk travels is reduced ...

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I'm not completely sure what you want, but honestly the entirety of Spivak's Calculus on manifolds is devoted to exactly that. If you want something that feels familiar, you can simply find $\nabla$ in various coordinate systems in Wikipedia, but if you want a less coordinate-centric view then you're probably going to need to step outside of your comfort ...

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I would say that the Wikipedia page on curvilinear coordinates and the article Mathematical Physics Lessons - Gradient, Divergence and Curl in Curvilinear Coordinates by James Foadi are enough to understand what is going on.

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Let's take the example of the white Gaussian noise. The total (rms) power of noise is a particular number with units of power. However, it is often more interesting to know how much power there is at a given frequency. And this is where a fractal dimension comes in. Gaussian white noise has constant power spectral density. In general, when you look at the ...

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The only context in which I can think of something like this coming up is in distributions near phase transitions. For instance, if you ask about the correlation of two spins in a magnet near the Curie temperature, it will have a power-law dependence on their separation, $$\langle \vec{s}(x) \cdot \vec{s}(y) \rangle \propto |x - y|^\alpha,$$ where $\alpha$ ...

3

In the US, if you purchase a balance or set of reference weights (masses) or a scale for scientific purposes, you can also purchase with it a certificate of traceability. This is a document that states how your device was compared to a reference, and how that reference was traceably compared to an even better reference, and so on, up to the standard kilogram ...

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When the I nternational prototype kilogram (IPK) was created, copies were made and sent to the most important countries in the world and are kept in a protected environment. Periodically they are returned to France, checked and compared and, surprisingly enough, their masses do not match anymore. Factories that produce these items have access to them or ...

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I second The Cartoon Guide to Physics by Larry Gonick, but I also have to add Einstein for Beginners by Joseph Schwartz. Those two books are probably the most responsible for getting me into my physics career. I'd also give a big nod to Thinking Physics: Understandable Practical Reality by Lewis Carroll Epstein. This is a phenomenal choice for excellent ...

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The below seems to be a candidate for the first use of the term 'Majorana fermion'. (I'm not sure if it satisfies your other criteria.) Salam, Abdus, and J. Strathdee. Super-symmetry and non-Abelian gauges. International Centre for Theoretical Physics, Trieste (Italy), 1974.

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Consider the drift diffusion equation $$\dfrac{\partial}{\partial t}\psi=\mu\dfrac{\partial}{\partial x}\psi+\kappa^2\dfrac{\partial^2}{\partial x^2}\psi.$$ Dimensional analysis tells us that $\mu$ is a characteristic length per time (drift velocity) while $\kappa$ is a characteristic length per square root of time. This small factoid has curious ...

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Introducing Quantum Theory: A graphic guide is a very good graphical book. It really provokes one to study more and more in this area. It uses the Pilot wave theory which is a negative point. Neverthless, the pictures are really breathetaking! Physicists here explain their contributions & the problems by themselves! Being jealous at the Solvay ...

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$\hat{I}_D(k)={{g^2}\over4}\int_0^1d\alpha\int_0^\infty d\sigma\int\sigma\mathrm{e}^{-[q^2+\alpha(1-\alpha)k^2+m^2]\sigma}\vec{a}q$. Just a wild guess. [Oh, you asked for two formulae. Sorry.] Either that, or it is $\int_0^\infty\mathrm{e}^{-a\alpha}\sigma d\sigma=a^{-2}$.

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The name T-duality stands for Target-space duality, see e.g. this preprint.

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It comes from S matrix theory, long before quarks were imagined, S,T and U characterize the type of exchange in the Feynman diagrams entering the S matrix calculation, and they are called Mandelstam variables. s channel-------------------------- t channel------------------------u channel duality meant that the sums could be done either in S ...

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Yes. Two particles at a given position, one moving and the other at rest are having the same kinematic state. But dynamic state takes in the velocity. When you need to specify both position and velocity - it becomes kinetic state. After all kinematics + dynamics = Kinetics.

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For the most part, you are right. Physics is tough, and in many ways high school physics is the hardest because it is the first introduction to a new and difficult way of thinking. Furthermore, teachers are under pressure to complete the curriculum. And there's always the possibility that the teacher him/herself does not have a firm grasp of the subject. ...

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sorry to hear that things are frustrating. I don't think you need the Huygen principle for the double slit experiment. Take a look at the diagram below... The diagram shows two rays from a double slit experiment. The path lengths are slightly different from the two slits. In one case the waves arrive in phase and you get the bright fringe - constructive ...

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Relativists tend to use the proper time, $d\tau$, and the proper distance, $ds$, interchangably. If you're working with proper time you'd expect the equation for it to look like: $$d\tau^2 = dt^2 + \text{other terms}$$ while if you're working with proper distance you expect: $$ds^2 = dx^2 + dy^2 + dz^2 + \text{other terms}$$ The sign problem comes ...

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Could you provide a simple reason for these two conventions? The reason behind the (-,+,+,+) convention (the "mostly plus metric") is that a positive length in 3 dimensional space (e.g., the distance from my head to my toes) should still be a positive length in 4 dimensional space-time. Why should the distance from my head to my toes all of a sudden ...

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One never pluralizes unit abbreviations. Your link goes to the BIPM, the body responsible for maintaining the definitions of the international system of units, and is authoritative. The folks at NIST agree and address most of your questions. I would say The pipe is 0.75 m long. or The pipe is 75 centimeters long. or even The pipe is ...

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cms and kgs are wrong. The SI units are abbreviations which are also used in the plural. You will write 2.6 m/s or 1 m/s, but say "2.6 meters per second" or "1 meter per second" respectively. Keep in mind the SI units are also used in tons of other languages that do not form the plural by attaching an -s. The units look the same in those languages. (e.g. ...

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The first difficulty in making a measurement of this kind is, of course, to build the facility. However once you solve all the engineering issues and put your machines in place, the experiment flow is pretty straightforward: you run and you get the data, in principle without any human intervention. Up to here you just let Nature do its work in a pretty ...

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Most of the reproduction of results in particle physics comes from two sources: Competing experiments running nearly simultaneously. In this case both ATLAS and CMS got comparable results. Now, they are both using the beam from the LHC, so how do we know the beam is properly understood? Because while they were commissioning those machines they reproduced ...

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Do we have any similar experiments where we confirm a theory without being able to reproduce those results? Not today, but once we know how it works we can repeat it on a smaller and cheaper scale. The first electronic calculators required an entire floor, consumed staggering amounts of power and cost a budget-busting amount of money. Today, my phone ...

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The question is "how much scientific confidence can we put into things like the mass of the Higgs". Well, what is the level of certainty? According to CERN it is around 7 sigma. In simple terms at 7 sigma, both the CMS and ATLAS teams are reporting that there’s only a 0.0000000001% chance that they haven’t found a Higgs-like particle.

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A firm understanding of classical physics is essential. This means understanding the qualitative and quantitative aspects of: 1) Newton's three laws of motion (Kinematic and Dynamic perspective) 2) Rotational motion dynamics 3) Electromagnetism 4) Newtonian mechanics (Newtonian gravity) 5) Principle of superposition and waves 6) Classical thermal ...

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