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timo

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Everything posted by timo

  1. From the context I am assuming that "theorist" is supposed to mean a theoretical physicist (wouldn't be sure how one could be "someway through a degree to become a theorist" otherwise). Pretty much all areas of physics, as well as some interdisciplinary fields, have theoretical physicists working in them. Looking at the theory departments of universities' physics faculties will give you examples. Some examples coming to my mind at the moment: biophysics, solid state physics, particle and astrophysics, polymer physics, phase transitions, non-linear dynamics, neurophysics, econophysics, physical chemistry. And I am pretty sure the nuclear physicists and optics guys also have theoretical physicists. Just don't happen to know anyone personally.
  2. I assume the reason someone was upset with Dekan's answer was the undiplomatic use of "abnormal", which is 1) a bit insulting and 2) a bit reciprocal (since may people's views on "normal" are based on abrahamic religions' belief over thousands of years, I think). Apart from that, that would have been my first thought, too (although admittedly without having any competence in that field). Especially since these religions come with a claim of absolute truth - it's not "my gods are stronger than yours" but "only my god exists". That said, one should probably be careful to deduce a rule from what could possibly be cosidered a single event/religion. As any natural scientist will tell you: It is always easy to make up an explanation for a small set of data because the human mind is very creative. But most explanations turn out to be wrong when exposed to a larger set - at least that is what usually happens to me
  3. I think society, ethics and language aren't that bad ideas, either.
  4. Most people agree that more than two objects exist in nature. So for a natural scientist these questions are somewhat irrelevant. And the majority of scientists working with/on relativity are natural scientists.
  5. The statement made by Aarhus university seems very strange to me. So I tried to find the article. I could not, but I found a few quite remarkable things: The university page lists publication up to 2016 (i.e. two years in the future), which is rather uncommon in my experience. The scientist quoted in the article is apparently quite an active writer, having written (or being about to publish) five books this year (not counting book chapters and papers). But I could not find a publication listed that, judging from its title, seems to cover water shortages due to water requirements of energy generation - I may have missed them, though. So far, this all looks a bit alien to me. But my point is not trying to make ad hominem attacks on the statement. My point is: Does anyone know where to read the actual two publications that are referred to in the article? I would really like to read the actual finding, since I do not believe the validity of press coverage or interview statements (I know how our crap results are being sold by our head of section ...).
  6. Great reading, especially since it appears to build upon a large amount of experience (personally meeting the people was a surprising level of involvement I had not expected). A keeper for my PDF collection and also a text that makes you think - even if the number of such cases is probably low compared to total society. I was a bit disappointed that "be rude" turned out to be the only non-case-specific lemma, though. Natural sciences are probably less suited to be put into a computer since you only get out what you put in - and it is usually the "what is put in" that is the matter of debate. I was hoping for some magical insight/guide until the very end.
  7. It might be worthwhile noting that common applications involving anti-matter are not in the field of energy supply. Neither is common research into anti-matter, as far as I know.
  8. Was about time that someone on the Internet finally finds out that relativity is wrong.
  9. Physics is commonly understood (amonst physicists) as a discipline that tried to quantitatively describe nature. That is, "all apples are attracted by earth, which is why they fall down" is not the description of nature that physics is about. The description that physics is about is "each apple is subject a force of F=mg due to earth attraction, where g is a universal constant. Since F=ma, the apples are accelerated towards earth as a consequence, unless a counteracting force exists" (in case it is not clear: the quantitative aspect comes in when you plug numbers in for the letters). Consequently, physics in the sense of today's understanding of the term is not possible without mathematics.
  10. It may well be that new members need a certain minimum number of posts before they can post images/attachments. For some strange reason I also have the feeling this may be a very good setting to have.
  11. To my knowledge the largest share of PV modules comes from China. That may be satellite contractors (not sure how many million satellites China has in space), but I doubt they have a large influence on German or US politics. In my experience, westerns companies mostly provide the AC/DC converters for the installations. An AC/DC converter, however, is not exactly the first piece of hardware I would expect in satellites or military equipment associated with PV. @Tom: Siemens At least in a physicist's world in which a power grid is a set of connected lines with a certain length and resistivity, some power sources and sinks at which some of the lines end, and some magic that controls the flow at the nodes. With a universal language spoken by all nodes, of course. And a well-defined optimization problem to solve. And perhaps even with correlations discarded for simplicity. A bit more than two years ago I was still in physics, too. And I would have said the same. Then I switched into a field called "distributed energy management", and supposed tautologies start to be a bit more tricky when it comes to details. Examples: In reality, there is a strong hierarchical structure in the nodes. The magic that controls the power flow at the nodes is devices built by engineers who knew that power flow is always from the central production to the distributed consumption. So no need to build an engine that supports power flow in the other direction. On the ICT side a lack of common communication protocols is an issue. As is the lack of common goals. On the business level, the whole thing is much more complicated than "I buy electricity from the shop who sends it via line", and there is a whole lot of different parties involved. And correlations of random production on different scales may even create new problems for the already-existing grid. Wind power may look distributed. But in Germany on a country-wide level most wind is in the north, requiring large new grid lines to be build from the north to the south. So on that scale wind power production is more centralized than coal or nuclear power, which you can spread evenly (or even better: put where the demand is). To put it back into the physicist's perspective: Even if large amounts of PV production were a good idea a phase transition into a new grid state may be required (grid in this case meaning the whole of physical grid, protocols, laws, parties, ...) which is likely to be associated with a phase transition barrier that must be crossed (or catalyzed), Derailing the thread even a bit more: The problems mentioned in the previous paragraph are problems that can probably be solved somehow. What is left is the archenemy of distributed generation: Captain Corporate Capitalism with his mighty hammer "local jobs may be endangered". Big companies that can afford to build large power plants, with little competition because not many others can afford it, are not interested in people putting solar panels on their roof and producing their own energy (and neither in having a lot of competitors if they went into that market, themselves). Smaller companies cannot afford to support an army of lobbyists and PR agents.
  12. A more straightforward scenario, though admittedly not exactly being what the OP asked about, would be solar-powered charging stations for bicycles with batteries. Those could be full e-bikes or, currently more likely, the very popular pedelecs. This could be integrated at home (trivial solution), at the workplace (technically pretty much the same, but possibly with extra constraints from stupid laws), or at bike-rental stations (most innovative but also most interesting). Conceptually, electric bikes would not be too different from electric cars in this picture.
  13. Usually, the position of objects is described by coordinates that are real numbers. In that picture the number of locations of a single atom in any finite space is infinite. Subsequently, the number of possible arrangements of N atoms is infinite, too. You might make a lot of magic statements claiming that quantum mechanics or the Planck scale were having and answer to your question. But I do not expect that they have any more merit than the classical picture. All those cases would merely be trying to make a very strong statement about reality of nature based on a mathematical approximation to it. The possibly more interesting/relevant question possibly is: Could you tell an infinite amount of states apart from each other? Let's assume a perfect watch, where the pointer for the minutes is perfect and always points to the exact fraction of a minute: Could you tell two very similar states apart from each other? Probably not, even though I would not know where and how to draw the line between two states being distinguishable or not. This straightforwardly leads to another question: Could you even tell that the pointer has an infinite amount of states? At least human perception could not tell the infinite amount of states apart from a pointer that has only 100000000000000435122 possible states. In my experience "infinite" is often overrated, and "practically infinite" usually is the more relevant property. The disadvantage to this stance of course is that statements start to depend on the context (particle physicists approximate millimeters with being an infinite distance, whereas architects disagree on this approximation).
  14. I still recommend focussing on trying to make sense rather than focussing on maxing out cynism. Not expecting this to happen, judging from what I have seen in this thread so far, I am out of this. It is not uncommon to consider mass as the charge in newtonian gravity.
  15. I would expect that it is normal for non-relativistic equations to not be Lorentz invariant (interpreting v<<c as "non-relativistic", here). In fact, you don't even know what the term is supposed to represent in the first place. It might be a force with non-force dimensions. But that's just a semi-random guess. I considered quite a lot of possible criticism on the OP. But in the end it boiled down to "it's not even criticizable".
  16. You might want to put a little more effort into explaining what you are talking about and what the reasoning behind your conclusion is (but please start with the first part, reading reasoning without knowing the context is pointless). Labelling all terms appearing in an expression is a good thing. But while it could be considered necessary it is certainly not sufficient.
  17. A few comments of mine: First of all, copyrighting and patenting are probably not the same thing. Copyrighting refers to having the rights to multiply a particular piece of work. Patenting is the exclusive right to commercially exploit an invention for a certain amount of time. Neither has to do with "giving credit" or "getting recognition" but instead see the world from a purely economical point of view (as most laws do). In fact, more often than not the inventor/creator/artist/scientist is actually not the copyright holder (music, movies, software, scientific publications, ...). What the OP mean is closer to patents, but not quite, though. Microsoft, Apple, ... don't hold thousands of patents because they want recognition for their ideas. They want to keep others out of their business. If the OP find the grand unified theory of the universe and conceives a kick-ass device employing an aspect of that theory then while the theory cannot be patented/copyrighted in itself, the kick-ass device can be patented (possibly after presenting a working prototype ...). Interestingly, the copyright situation with software seems to be comparable to that of scientific publications. Me and the people on my project recently discussed that with a lawyer with regard to a piece of software we develop in the project. According to the lawyer, ideas and the design/architecture of the software cannot be copyrighted. Only the particular implementation of it can. From the perspective of the creators that is a bit disappointing, of course: just as doing the research is more work than writing the paper about the results there is more intellectual work in the architecture of a software than in the implementation of the architecture. But from a "whole picture" perspective I believe that no one should have legal rights on ideas (I am a rather strong opponent of patents, btw).
  18. It's really not clear what you are trying to say. What is "the 12i deal"? You have +12i and -12i in your term, so they add up to 0i=0. For many cases you can treat the "i" just as any regular variable (e.g. (4i)^2 = 4^2*i^2, just as (4x)^2 = 4^2*x^2). Except that you know more about it than about other variables (e.g. that 4^2 * i^2 = 16 * (-1) = -16). There's little point in learning about complex numbers ahead of time hoping to get an edge in understanding QM. But complex numbers are really simple, so there is nothing wrong with learning about them for fun. A fun use of complex numbers is in fractals like the Mandelbrot Set. Completely useless, but fun to program and play around with. That's where I first encountered complex numbers.
  19. Contrary to popular misconception most words used in physics do not have that unique definition that is the same between all physics texts or even within a single textbook (despite Wikipedia giving you the impression - that is because they have to decide on one definition to use in their text). Physics texts should be read in context and with the attitude of a sentient being. Not with the attitude of a 20th century computer (21st century computers can read context ...). It is uncommon to count centrifugal effects into gravity. It would be much less uncommon to count them into "g" (in fact that is what I would expect from "g"). But both can or can not be done, as long as it is clear what is meant on the physical level (which may not have a 1-to-1 mapping onto human language). In this particular example, for me the meaning of the sentence in question is pretty clear. In the sense that the physical scenario is apparent. If you had the full text, it would probably be even much more obvious, since the sentence quoted probably comes at the end of an explicit calculation of the correction number quoted. Both alternative texts; "gravity and the centripetal centrifugal acceleration" and "due to the apparent g", would be fine, too (assuming "g" being defined). If it is the first time this results is stated the two alternatives may in fact be more suitable than what the book writes.
  20. It's remarkable that all perpetual motion devices proposed on SFN in the past ten years base on magnetism. I wonder if that warrants looking into "potential energy of a dipole-dipole system" and possibly writing up a small explanation on it.
  21. timo

    Frictional work

    You might want to consider the sign your answer should have. In other words, what would be the effect of positive or negative work being done by the oil? Note that formally the statement "A = B <=> |A| = |B|" that appears in your calculation is wrong; as readily verified by A=+1 and B=-1. Probably won't matter for med school where logic tends not to be on the curriculum. But since you posted your calculation I might as well comment on that.
  22. Who would have though atheists spend their time wondering about what they would do if god sent them a sign.
  23. You can even consider the center of mass of two people not holding hands. It's just that in the case of hydrogen atoms doing so can make sense for, e.g. scattering experiments or separating the full solution into parts that one can associate physical effects to. In the case of two persons you are not very likely to find a scenario where the concept of their common de Brogile wavelength helps with anything, partly because it is going to be much smaller than the relative positions.
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