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Everything posted by swansont

  1. In addition to your lack of air flow analysis, you haven’t shown how quickly the virus, much more massive than air molecules, would get up to speed.
  2. Not a good start. Solar and wind are cheaper. That article doesn’t say that energy consumption is being slashed. (you have a bad link, BTW) https://www.sciencedaily.com/releases/2019/07/190712151926.htm It won’t rise if they install green energy. And that last part is easier, now that wind and solar are cheaper sources of electricity. One problem here is that you are basing your “argument” on old data. What was true in the 1980s is not necessarily true today
  3. Present evidence that this is happening, or it’s a reasonable expectation. You claimed they were “completely ignoring possible benefits” and I debunked that. If they feel that the negatives outweigh the positives, how can you be sure this isn’t a conclusion? How about presenting evidence, instead of moving the goalposts. Disparagement and assertion. No science. A pity you won’t apply your education here. How much warmer is it up in those mountains?
  4. The last straw? For some, perhaps. But I am reminded of the tweet from Dan Hodges regarding Sandy Hook “In retrospect,” wrote Hodges, “Sandy Hook marked the end of the U.S. gun-control debate. Once America decided killing children was bearable, it was over.” (from https://www.miamiherald.com/opinion/op-ed/article33250299.html) I think the same sentiment applies here. Previous incidents, almost too numerous to mention, should have been the last straw — and weren't. Too many have decided this is tolerable, or ignorable. IOW, I wouldn't hold my breath hoping that this one incident swings the pendulum very far. People who have tolerated this kind of violence over time aren't going to be swayed. They are more incensed by Colin Kaepernick taking a knee. Pointing out the racial injustice hurts them more than the injustice. What I think is more likely is that reform comes if we vote the people who have supported or tolerated this kind of behavior out of office, but they will be voted out for other reasons as well. If that happens, this will be part of it, but nowhere close to the whole of it. edit to add: one difference here is Trump stepping in, owing to the protests. His anti-Midas touch might amplify things.
  5. And you also used the term effective mass. I was issuing a caution that, for example, if one says "mass" it usually means rest mass, unless one is being sloppy. IOW there are plenty of posts here and web pages elsewhere, where people insist that photons have mass, because they aren't making a very necessary distinction.
  6. https://neutrinos.fnal.gov/mysteries/handedness/
  7. The short answer is: Theory says this, and experiment confirms the theory is correct. Either/both aspects of this can be discussed, but it's best if you already have familiarity with the subject. But can fermions have a left- or right-handed nature. In the standard model, neutrinos are left-handed. One must be careful. Mass generally refers to rest mass or invariant mass. To say that photons have mass requires one to use a different definition of mass (e.g. effective mass, or relativistic mass). When one does not pay close attention to the details, it can cause confusion.
  8. This isn't an analysis, it's a hand-wave. You're making an assertion that isn't backed up by any analysis, and yet, this is a science site. It's not unreasonable to expect that this be backed up by some science and/or engineering. It also assumes you have a room where you can put that amount of vent area in the ceiling. You want a certain result, but have done little to show if such a result is feasible. You haven 't even done something simple, like showing that a 10' x 10' room with air moving at 2 mph / 3' per second in the middle means the air must be moving up to 12 mph at the vent (since it has to be moving ~6x faster if there's no change in pressure) and that this is moving 18,000 cfm through a single room. What kind of system handles that? What kind of pressure do you need in the ducts to get that kind of airflow? IOW, you can't just say "lets move the air in the room at 2 mph" and ignore all of the ramifications and system requirements, like you have a magic wand to make these other problems go away.
  9. If you mean any given human can survive, then the statement is trivially false, as we have already observed that humans die when it gets hotter, and areas of the globe would be uninhabitable. If you mean humans as a species, and that's all that matters, then this is an argument not in good faith, since nobody is arguing extinction of the species will be the result, or that the impact is limited to humans. If they conclude that the temperature will go up by XºC over some span of time, under some set of conditions, that is neither an affirmative nor pessimistic bias. And, as scientists have discussed positive impacts, your argument to the contrary is moot. e.g. https://www.climate.gov/news-features/climate-qa/are-there-positive-benefits-global-warming Why would you expect anyone to take this "argument" seriously? Because land is evenly distributed on the globe? And arable land is all that matters?
  10. Can/will you answer my question? And make no mistake, if you are proposing this mechanism, you are replacing GR.
  11. Gravity isn’t the only effect of GR. How does an “index” give rise to e.g. frame dragging? Or other effects of GR?
  12. Yes. The atoms in an atomic clock, for example, explicitly experience the effect. It’s not specifically the gravitational force that results in time dilation, it’s the potential - the position in the gravitational field. So a constant g would still result in time dilation for different vertical positions. If your slits were spaced vertically, there would be an effect. Or if you tossed atoms in a superposition, where the two states would go to different heights. Mark Kasevich has done such experiments with his 10m tower.
  13. Waves are localized? I never claimed it was “opposite” It’s a wave test, to be sure. Classical particles do not interfere. Photons undergo interactions with only one atom, even though its wavelength is much larger than the atom, and other atoms are around. That’s not how waves behave.
  14. Send a particle through a double slit, and it will interfere. Through a single slit it will diffract.
  15. Many have mass, sure, but quantized energy and localized interaction do not require mass. Photons exhibit these behaviors as well.
  16. There are two wave behaviors to consider: the wave function, from Schrödinger’s equation, and the matter-wave behavior from deBroglie’s equation. The two are not identical. The “collapsed state” issue applies to the former, not the latter. IOW, you will still have wave behavior even in a single quantum state No, I disagree. Quantum particles have quantized energy and a localized interaction region, which are not wave behaviors.
  17. Right. the force exerted on the object is in the FBD. The force exerted by the object is not.
  18. swansont


    I see something
  19. There are chemicals used in smoke/fog machines.
  20. I wasn't aware the Wikipedia prevented editing or participation based on geography. If you Google free body diagrams, you will find plenty of the other kind Take a peek at one of the permutations of Halliday & Resnick, a very popular into to physics textbook https://www.wileyplus.com/physics/halliday-fundamentals-of-physics-11e-eprof18272/ No, and using the dot renders that moot. By the diagram? It was only recently posted.
  21. I wonder if this convention is geographic in nature. FBDs I have seen and made look a lot like the one shown. That is unfortunate, but otherwise the arrows would have to overlap, which might be more confusing. Given that action-reaction is typically introduced very early in the curriculum, I am also sure it's not intended.
  22. I don't see meartha in your equations (i.e. the reaction force to the weight of the book). And you have not labeled your normal forces to indicate the source of that force. The normal force of the book on the table, or the normal force of the table on the book. Only one of them appears in an equation. Not both. What is F in the equation? It's not given in the problem. Whether the weight and normal force are equal in magnitude has nothing to do with action-reaction. FAB = -FBA There are no caveats on that equation. If the book is in freefall, the earth still feels a pull from the book, and the two forces are equal and opposite. mearthaearth = -mbookabook There is no way I can reconcile this with Newton's third law. The weight of the book is not something that is acting on the table, as the weight of the book is not a gravitational force. The force the book exerts on the table is a normal force. It's a true statement, but it's not just that it's two different objects. It's the same two objects, and category of force. I would say that your statement is less precise. Gravity acts on the book, and on the table, so that's forces acting on two objects. But those are not an action-reaction force pair.
  23. In a valid free-body diagram, no action-reaction force pairs will appear. Because in a FBD, all forces are acting on the same object, while for action-reaction, it's a force acting between two different objects.
  24. Your question is a mainstream science question. Yes, I have. PhD in experimental atomic physics, so I have used vacuum equipment for a long time. I've been through multiple iterations of having to fix vacuum problems. And so I know that you hadn't given enough information to diagnose the problem. (also, being a scientist, I wouldn't be using inches of Hg) Like I said, it could be the gauge, it could be the pump, it could be a leak. You didn't tell me what kind of gauge you were using - it matters. You didn't say anything about the setup - it matters. It gets harder and harder to lower pressure the lower the pressure gets. A mechanical pump will only get you so far (a good one gets you to the low end of "low vacuum" in the list Strange presented). All systems leak; the question is how much. Outgassing and virtual leaks will limit you as well. For good vacuum one bakes the system to speed up the outgassing, but that's usually not an issue for just a mechanical pump.
  25. Action-reaction pairs don’t compensate for anything, either. They don’t appear in equation of motion because one of the forces doesn’t act on the body. There is no composite system under discussion. That’s a distraction to the question that was posed. The question asked gives no reason to look at the book+table system. The issue of misidentifying action-reaction pairs is a quite common misconception that students have, in my experience. It’s best not to feed it.
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