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Light particle is a vague term actually. There are two ways I can think of a particle being "light". If you mean has least mass than photons have zero mass so it is indeed lightest. The exact mass of lightest neutrino is not yet known. It is actually wrong to talk about "A photon" because it is not a single particle. Photon is a "quanta" of ...


An approach can be: find the force on position $x$ due to influence of mass on $x'$ all other: $$f_g(x,x',t) = \frac{G M(x,t)M(x',t)}{\left( x-x' \right)^2} $$ The integral of this equation, which is the resulting force on $x$ from the influence of all other massess, will be equal to momentum change in this point: $$ M(x,t) \int \frac{G M(x',t)}{\left( ...


If you take a particle approach, then you might want to investigate Particle-in-cell methods. In this particular approach, each point-charge is given a position, velocity, and charge in any dimension (1d, 2d, or 3d) and you evolve the particles using the Lorentz force law (1) and the position-derivative (2): \begin{align} m\frac{d\mathbf v}{dt}&=q\mathbf ...


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".


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.


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


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


The answer is yes. The de Broglie wavelengths of freely propagating particles (i.e. forget the influence of interactions and gravity perturbations, just consider the Universe as a whole) are redshifted by the expansion of the universe. Another way of saying this is that their peculiar momenta with respect to a co-moving local volume decrease as the inverse ...

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