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5

Yes! Any beam that is blocked by an object will basically make a shadow. For example, the IceCube detector can see the moon's cosmic ray shadow.


3

Hints: The action is $$\tag{A} S[y]:=\int_0^1 \! dt ~L(y,\dot{y}), \qquad L(y,\dot{y})~:=~\frac{m}{2}\dot{y}^2 -mgy, $$ with Dirichlet boundary conditions $$\tag{B} y(0)~=~0 \quad\text{and}\quad y(1)~=~-\frac{g}{2}. $$ Calculate explicitly the composed function $$\tag{C} s(\epsilon)~:=~ S[y_{\epsilon}] , $$ where $$\tag{D} ...


2

For example, acoustic shadow (http://en.wikipedia.org/wiki/Acoustic_shadow ).


2

In general Allen variance is not a good way to characterize non-harmonic processes and processes which modulate the phase, frequency or amplitude of the oscillator in a non-stochastic manner for the same reason that the conventional variance is not a good measure for processes that do not, at least approximately, follow a normal distribution. For practical ...


1

Continuity equations are an embodiment of local conservation laws, and they both reflect the fact that there is no 'quantity teleportation'. That said, the local transport of a quantity is perfectly possible within local conservation laws and it is precisely this that the continuity equation models. Your distinction between global and local conservation ...


1

In the equation (i.e. mathematically), where do you see the differences between continuity equations and conservation laws? The continuity equation is not sufficient to derive conservation of something. For example, continuity equation for fluid flow in non-relativistic theory is $$ \partial_t \rho + \nabla \cdot (\rho \mathbf v) = 0 $$ wherer $\rho$ ...


1

Duration is certainly a more physical concept than time. Duration is something you may measure between timelike separated events while time is always something you compute by adding up duration measurements + an arbitrary constant to fix the origin. Duration is experimental and relational while time (e.g. GPS time) is an abstract a posteriori ...


1

Okay, I am going to try and give this a shot, but this is most probably not going to be a decisive answer. Let us operate with the term event time and duration and consider only special relativity (SR). The conclusions of general relativity should be the same for reasonable space-times. (e.g. without closed time-like curves etc.) We expect event time to ...


1

Yes, for example a Crookes tube shows an electron shadow. The area I live (Chester, UK) is in a rain shadow.


1

Yes, the term "shadow" can refer also to something or (dare I say) someone that is dark, shady, inconspicuous, etc. One can also use it as a verb; to shadow someone is to follow them closely. Like "I'm having the new guy shadow me for a while until he learns how to do everything".


1

1. No, there is no "shift in meaning". "Accuracy", "precision", and "trueness" is a technical term for measurement not physics. And there is no such thing as a "measurement community" because measurement occurs everywhere. As such, "accuracy", "precision", and "trueness" are heavily overloaded technical terms used in varying fields like maths, computer ...


1

The web site you link is using the expression: $$ \rho_c = \frac{3}{8\pi G \theta^2} $$ where $\theta$ is the Hubble time and is equal to $1/H$. So your second equation should be: $$ \rho_c = \frac{3}{8\pi G \theta^2} = \frac{3}{8\pi G \left(1/H\right)^2} = \frac{3H^2}{8\pi G} $$


1

The best way to understand the nature of intensive and extensive quantities in thermodynamics is like this: Take a system of your interest. Make it into two portions (one large portion and the other a small portion) by using a partition, for example. Then see the property of interest of the two samples. Density of the two portions will be the same as the ...



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