Nikolaj K.

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bio website graph.axiomsofchoice.org/… location age member for 2 years, 5 months seen 3 hours ago profile views 1,828

A duck walks into a bar. Animal control is promptly called and the duck is released into a near by park.

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 Feb23 comment Why is introductory physics not taught in a more “axiomatic” way? @TerryBollinger: Doesn't the abstract S-matrix approach do exaclty that? Feb23 comment Why is introductory physics not taught in a more “axiomatic” way? @TerryBollinger: Uncomfortable similarities? Stop worrying and learn to love the bomb. ;) Feb20 comment What is the difference between translation and rotation? That's vague. Can you give an example for a situation where "a rotation motion corresponds to a force acting on a body towards a direction perpendicular to its velocity." and where you can make precise what the "velocity", acting "force" and "rotation" is? Feb19 comment Does the 1-D poisson's equation have monotonic potentials if $\rho=\rho(\phi(z))$? @Anode: "It's no surprise that $\phi(z)=0$ in your example." What do you mean by that? The solution is $\phi(z)=a·z+b$ and these are valid for all $a,b$. The conclusion you should draw isn't that $\phi(z)=0$ follows. Feb19 comment Does the 1-D poisson's equation have monotonic potentials if $\rho=\rho(\phi(z))$? @Anode: So? $\rho(\phi):=0$ fulfills $\rho(\phi=0)=0$. So I'm pointing out that for the trivial case, the concluded relation is already broken. That's a general tool for investigating mathematics: If you're skeptical of a result obtained with free parameters, go back and choose particular examples for those parameters to see at which point in the derivation the system breaks down. Feb19 comment Does the 1-D poisson's equation have monotonic potentials if $\rho=\rho(\phi(z))$? For $\rho(\phi):=0$ the solution is $\phi(z)=a·z+b$ and the equation reads $0=0$. You say you "integrate up" and end up with $\frac{1}{2}a^2=0$. Magic. Feb15 revised Any examples of commensurable subgroups appearing in physics? How can our set comprehensions be real if our formulas aren't real? Feb15 suggested suggested edit on Any examples of commensurable subgroups appearing in physics? Feb11 comment What is the relation between General Relativity and Newtonian Mechanics? I know what you want to say in your first sentence, but what you write isn't information one can work with. And going further, it's not clear what "case ... can be proven means", but you are implying that at least any result obtained in Newtonian spacetime agrees with the corresponding one in general relativity. But that's not true and it's not clear in what sense you'd "arrive" at Newtonian equations. Feb10 revised Which areas in physics overlap with those of social network theory for the analysis of the graphs? edited tags Feb10 suggested suggested edit on Which areas in physics overlap with those of social network theory for the analysis of the graphs? Feb7 comment What justifies dimensional analysis? @KyleKanos: Well, if it's arguing to you then I can understand - otherwise one has the chance to learn. And I don't think people think enough about units to understand them, mostly because the practical approach suffices most of the time. When I say I don't understand physical units I mean in the sense that mathematicians don't understand prime numbers. Feb7 comment What justifies dimensional analysis? @KyleKanos: Of course you must give meaning to it, but it's not like that step is avoided in the case of making sense of $3\cdot 2\ kg\ s^{-1}$. You just effectively define "makes sense" as "no person working in a physics department has been able to publish a paper on it that others find valuable". You don't tell the OP something which he doesn't know. Feb7 comment What justifies dimensional analysis? But you don't justify why it doesn't make sense, you just observe that it's of no use for anyone you have heard of. You just have no application for the expression $3kg+2s^{-1}$ and think you can infer from this that it's meaningless, while $3·2\ kg\ s^{-1}$ is "physical". As a side note, I also don't know how to infer if something is physical or unphysical. Feb7 comment What justifies dimensional analysis? Here is a link to Terrence Tao's blog, where he discusses mathematical underpinning of physical units. I personally guess that types might be a better approach. @KyleKanos: I don't see how what you answered clears things up at all. You just say "that's how we do it". The motivation, or why certain things "make sense" and others don't, is lost on me. I, for one, am a PhD student with a physics degree and I don't quite why physical units work either. Feb6 comment Does Gravity / curved space cause rotation? Are you asking if an extended object tilts (and then rotates) when headed in the general direction of another massive object? Feb4 comment What is fundamentally physically impossible? Okay, so you define science to be that what scientists do and know, which can change. And then things "that absolutely cannot happen" are just the things what scientist at the moment where you life don't believe to be possible, right? Otherwise I don't think something we can comprehend could be impossible. For a statements like "mass of a particle can't change" (or whatever your impossible-candidate is) must necessarily be statements made by humans and hence underlie a theory (e.g. the idea of "mass") and every concept eventually gets corrected and replaces, rendering the old statements fuzzy. Feb4 comment What is fundamentally physically impossible? I don't understand the paragraph which is followed by "That is obviously...". And what does it mean for science to change? Are you saying there are things which are physically impossible or not? Feb2 comment interaction between mathematical structures Sounds like you're fascinated by the fact that multiplication is repeated addition and you want to draw an analogy between mathematical operations and physical objects. It's a little vague so far. Feb2 accepted In which field theories with fermions do string- and fivebrane structures not come up?