# Tag Info

9

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. ...

7

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 ...

6

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 ...

4

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 ...

3

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

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 ...

3

In Physics what we do is try to understand reality based on the scientific method. What we do is build a mathematical model based on observations and then using it make predictions that are again verified. When we create a model and find out that it is compatible with nature we don't ask "why nature behaves like that", we simply found out that it does. And ...

2

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 $\alpha$ ...

2

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 ...

2

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 ...

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 ...

1

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 ...

1

The "adjustable constant" in that statement is the total energy $E$, and they mean it's "adjustable" in that the behavior of the system is completely independent of $E$ - this is known in physics as a symmetry, in that they system doesn't change if it has a different total amount of energy. In this case, the way to "adjust" the amount of energy would be ...

1

Well, when you pursuing a graduate degree, you might have to work under a supervision of one professor in your university. To put it simple, you have to choose a lab that suit your interest the most. While there are many laboratories, they usually classify into either experimental or theoretical. So, it is kind of up to you to decide, and of course the ...

1

Can anyone describe, (or point me to a paper that describes) time without referring to something else. No. Nobody can. However I can point you to Presentism, and to A World Without Time: The Forgotten Legacy of Godel and Einstein. I can also point out that relativity accurately models our world using spacetime and worldlines and geometry, but that the map ...

1

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 ...

1

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.

1

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 ...

1

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

1

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 ...

1

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.

1

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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