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"I would never die for my beliefs because I might be wrong."

-- Bertrand Russell


Nov
28
comment Is there a theory about kinetic energy “particles”?
When you bombard electrons with photons, you are in effect giving them kinetic energy. All particles are "kinetic energy particles". There's no need for an extra kind of particles. A change in kinetic energy corresponds to work being exerted by or on the system.
Nov
28
comment Four-dimensionalism vs energy economy
Never heard of it. Unless it means: the universe can be described as a 4-dimensional manifold, then it is a part of for instance GR or quantum field theory, but in and of itself, it is not rich enough to constitute a physical theory.
Nov
28
comment Four-dimensionalism vs energy economy
Not sure this is even a physics question. Remember however there is a holographic principle stating that all information in a N-dimensional space can be encoded on a (N-1)-dimensional boundary. If that principle holds true, I don't see any problem.
Nov
27
comment Best example of energy-entropy competition?
I'd say all living organisms seem to enter this cathegory. But it's hard to prove quantitatively. But obviously, when we eat, we don't do so to increase our energy (except when growing), we eat to diminish or keep our entropy low.
Nov
27
revised Is there a difference between observing a particle and hitting it with another particle?
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Nov
27
answered Is there a difference between observing a particle and hitting it with another particle?
Nov
27
comment If the light velocity is a vector quantity, why vector addition cannot be applied to it?
You can also mention that there is a kind of adapted addition law.
Nov
26
comment Did Einstein prove $E=mc^2$ correctly?
OK, I never meant to start a flame war. I have adapted my reply, I changed the "lousy" to "not great" and I have stricken the Hilbert comment and refered to Marek's reply. Everybody happy now? ;p
Nov
26
revised Did Einstein prove $E=mc^2$ correctly?
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Nov
24
revised Did Einstein prove $E=mc^2$ correctly?
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Nov
24
comment Did Einstein prove $E=mc^2$ correctly?
Well, how can I address it properly if I don't know what Ohanian is saying? So, thank's for the link.
Nov
24
answered Did Einstein prove $E=mc^2$ correctly?
Nov
23
comment Rope tension question
Yeah, I think Mark is right. That, or I'm always explaining it incorrectly to students. Please, don't say I screwed up so bad. :p
Nov
22
comment Linearity of quantum mechanics and nonlinearity of macroscopic physics
You start with a huge mistake. Newton's equation of motion is in general non-linear. Only for special cases such as the harmonic oscillator is the equation linear. Take for instance Newton's equation for the Kepler problem (two gravitating masses) and see if you can combine two solutions linearly to obtain a new one. It is however correct that linear equations will never lead to chaos, but that doesn't mean that linear equations can't be difficult. As you correctly point out, quantum systems have exponentially more variables as compared to their classical counterparts.
Nov
20
answered Modified Maxwell's equations
Nov
20
answered What is the difference between “kinematics” and “dynamics”?
Nov
20
comment Escape velocity from long ladder
There's a guy who often shows up in my university town who uses the escape velocity argument to demonstrate that the moon landings and all space travel are a big government conspiracy. That's not the only flaw in his argument(s). Funny dude, but totally off his rocker.
Nov
19
comment Is it guaranteed that wavefunction is well behaved everywhere?
For sure Marek, but I don't see why the Schrödinger equation is not considered a mathematical idealization then? After all, it's only a non-relativistic approximation. And if we're gonna start like this, everything that has ever been conceived of in physics is an idealization. Your decision to consider one more physically relevant than the other is arbitrary if you don't specify the bounds within which the approximation is valid or not. So, without doubt, the Schrödinger equation can do more than models for Anderson localization which are not unphysical, only less broadly applicable.
Nov
19
comment Is it guaranteed that wavefunction is well behaved everywhere?
Take the Bloch electrons in Noldorin's post. Some of the models describing the wave functions of these electrons satisfy neither 1 nor 4. As a result, the wave functions can be fractal.
Nov
18
comment Is it guaranteed that wavefunction is well behaved everywhere?
@Robert: seems to me the bound state of the Dirac potential doesn't fulfill condition 4. Keenan is still correct. Anyway, wether we agree to include 0 or not, I don't think condition 4 is necessary.