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 May 13 comment Tension in a curved charged wire (electrostatic force) - does wire thickness matter? A very interesting question.. +1 May 13 comment Does the Planck scale imply that spacetime is discrete? Another related: physics.stackexchange.com/q/4453 May 13 comment How do you explain spinning tops to a nine year old? +1 for the bicycle wheel suggestion. It's a great way to get the point across in a way that can really be seen, and felt. Careful not to catch your nose on the spinning tyre though! ;) May 13 comment Help getting the distance an object has moved not only was the question very close to being a "do my homework" type question anyway, clearly not permitted in the FAQ, but your answer has gone one step further and does it. Hence why I phrased my attempt more as a guide than complete calculation. May 13 comment Maxiumum weight a buoy can float @Georg - The volume of pressurized are is not meaningless; it has a mass associated with its volume and density. However, I was assuming the walls of the buoy were thin, and the air wasn't significantly pressurized (since this would have a detrimental effect on the buoyancy anyway.) Perhaps I could have stated this but I didn't want to overcomplicate a brief comment. May 13 comment Maxiumum weight a buoy can float Buoyancy is related to the weight of the volume of material displaced. In your case this means the max weight would be equal to $3943mm^3$ of water, minus the 0.8kg weight of the buoy.. May 13 revised On black holes, Hawking radiation and gravitational atoms Typo May 13 comment Help getting the distance an object has moved @Georg and @Qmechanic An unusual unit for distance. If that is indeed the case here, well .. fine. May 13 comment Help getting the distance an object has moved @Omega - Is there a typo in your unit for the speed? 14hm/min doesn't make any sense.. May 13 answered Help getting the distance an object has moved May 12 revised Space-time hospitality added 5 characters in body May 12 comment Shape of Fan Blades @Martin - Very interesting, thanks. I wonder whether the same principle work for a water pump? I suspect one would require near-lamina flow from the internal pump to holes but have no idea if this is feasible.. May 12 comment The meaning of action This is a nice compliment to the others answers but I feel it necessary to point out that the book you cite (QFT Demystified) contains a huge number of errors and in many sections over-simplifies the theory. It should not be considered as a suitable introductory text to the subject, or even one that should be trusted. May 10 revised Space-time hospitality Typo May 10 revised Space-time hospitality deleted 3 characters in body May 10 answered Space-time hospitality May 10 comment Space-time hospitality Whilst this question is hugely hypothetical (and could have been better worded) I see no harm in considering the requirement of gravity on the possibilty of life. Up-voting to conteract down-votes that I believe to be unfair. May 10 comment What happens if you try to freeze water in an water tight container +1 for the great video link May 10 comment Protons' repulsion within a nucleus +1 for a perfectly reasonable question. I only wish I'd got an answer in before @Lubosh ;) May 10 comment Is it pions or gluons that mediate the strong force between nucleons? @anna I posed this question after having read @Lubosh's answer. I don't feel that it answers my question and, either way, I was kind of hoping for a slightly more expansive answer. When I get a chance I'll add an edit, containing some LaTex, that should better describe why I posted this query.