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ScienceNostalgia101

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Everything posted by ScienceNostalgia101

  1. Not quite, just that all that excess water vapour pumped into the air would shift the equilibrium somewhat, sort of like how a weight hanging from a spring shifts its equilibrium. Still an unreasonable assumption?
  2. https://www.youtube.com/watch?v=y-4qqcCxD6g So the following video shows a method; involving hydroxides, silver nitrate, and ammonia, for depositing silver directly onto a surface. 1. Could any excess silver (ie. not deposited onto the surface) be re-used? 2. Could something like this (make the metal deposit onto the surface) be used with cheaper reflective materials, like aluminum? 3. How cost-effective would this be, as a mirror-making method? Does it depend on whether it's a flat mirror, concave mirror, or convex mirror? Would this be good for creating especially large concave/convex mirrors if you already had a large surface onto which to make the silver deposit itself?
  3. So this parody of an old video game portrays a (fictional!) oil explosion on an island from a distance; and the resulting duration of silence before the noise. Obviously, if we were directly given the angle to one end of the island and angle to another we could use geometry to estimate this fictional island's length. But here we're only given the distance to the island (via sound delay) and the fraction the island takes up of the field of view. This got me wondering whether or not "field of view" can be used to estimate "range of angles" between the point of observation and the object being observed. For instance, is there a function relating what fraction of a field of view an object takes up to the difference, in angle, between a bearing to the left side of the object and a bearing to the right side of the object? Does it depend on what these angles are, or only on the difference between them?
  4. Trouble is, cities that have a solid, pragmatic reason to be placed where they do also suffer the consequences of forest fires. (Fort McMurray comes to mind.) I can see why people who built their homes in the middle of nowhere could reasonably be considered at fault, but what about cities with plainly practical reasons for their location? Why is there not more of a movement to create large enough firebreaks to stop the fire? Or irrigation systems within those firebreaks that could be remotely activated to spray the embers?
  5. Forgot I even had this thread! Asked this for the purposes of Christmas-themed problems for my students. Realized that, tempting as a "Santa Clausius" pun would be, other topics than Clausius-Clapeyron worked anyway. That said, I'm still curious, and I'm not sure I fully understand the answer. I assume what you're saying is that if the rate of change in pressure is proportional to the rate of change in entropy with volume... therefore that entropic processes like evaporation will have to change pressure in accordance with that proportionality, making the effect of being a dissolved substance evaporating same as that of being a liquid evaporating? In a nutshell, is that a "yes"? Also, while I'm at it, why is it called the Clausius-Clapeyron equation if Clausius only came into the picture decades later?
  6. I mean the latent heat of vaporization; as in, yes, it's still around, but more of it as potential energy and less as kinetic? Sounds good, but sounds like it'd take a while to make such drastic changes to infrastructure, whereas climate change needs to be dealt with more urgently. Maybe something to think of after the climate crisis is resolved?
  7. This issue has long been an obsession of mine, since before I even really had an accurate understanding of what it was. I used to think embryonic stem cells came from aborted fetuses; yet I get angry when hearing others spread the exact same myth. (For the record, for anyone reading, they come from in vitro fertilizations or from cloned embryos.) To avoid falling into the same sort of trap as before, I want to make sure I know what I'm talking about amidst an issue left murky by controversy. A. One popular talking point against embryonic stem cell research is that because other stem cells have (supposedly) gotten better results. Firstly, aren't they supposed to be useful for different purposes than other stem cells are? Secondly, how much time and/or money has been poured into research with embryonic stem cells vs. any other type of stem cells? B. Another is that you can supposedly "program" non-embryonic stem cells to act like embryonic ones. I heard a lot about this about a decade or so ago when Obama was lifting funding limits on this research, but it hasn't been in the mainstream discussion much since. Have any of you heard any updates on the efficacy of this one? C. There is also discussion on the tradeoff between public and private sector embryonic stem cell research. The supposed benefit of the latter is that the taxpayers who object to it can wash their hands of direct culpability for it, by the fact that it isn't their money going toward it. The tradeoff, however, is that any private company that profits more from the disease than they would from a cure has a perverse incentive not to cure that disease. As well, any cure they do release, they can patent and exorbitantly overcharge for. Critics of public funding for embryonic stem cell research claim that private companies would be involved in this research anyway. Is this true? If so, why does the government give private companies public tax dollars, and why can't they just cut out the middleman and do the research themselves?
  8. Enough people prioritize the environment over human lives to prevent thinning and firebreak-grids? Where were these people when the Lac Megantic derailment was used as an excuse for pipelines? (Putting aside the use of trains for other dangerous goods than just oil.) Quite frankly, that kind of thing makes me wish they'd not only create permanent firebreaks but salt the Earth beneath them as well.
  9. Hmm... what about the fact that some of the thermal energy that would otherwise go toward increasing surface temperature instead goes toward boiling water? Would that decrease temperature while simultaneously increasing humidity? (Assuming some of the water vapour above each pot of food/coffee escaped into outdoor air before condensing?) As for me, I don't cook. I work in places that have food available and/or eat canned fish/frozen dinners/peanut butter sandwiches for protein. Perhaps not the healthiest approach, but it's what I'm used to.
  10. https://www.youtube.com/watch?v=ci8ZXxYDajQ So in this Southland scene, a stolen taxi is aimed directly at a police car and driven toward them for a head-on collision. The cops swerve to avoid this. I'm just wondering now; is there any way to deploy spikes in the front of police cars, with springs behind the spikes, such that the engine and/or tires of the vehicle in front of them can be punctured, while the springs absorb the impact so the car's speed doesn't change as abruptly as that of the vehicle in front of them? That way, if this sort of thing happens in real life, they can deploy the spikes instead of swerving and stop the criminal sooner.
  11. So we as a society have categorized weight into "underweight," "healthy," and "overweight." We assume there is an interval of weight that is healthier, in and of itself, than weight above or below it. However, what I'm left wondering is; how do we distinguish the effects of weight itself from the high cholesterol that often happens to; but does not always; correlate with it? I was once underweight. I tried to put on the weight by eating a lot of fatty foods; ones that happened to be especially high, however, in saturated fats. That left me with high cholesterol while I was still underweight. It stands to reason that one can be overweight with low cholesterol. Americans also eat a lot of foods high in saturated fat, so it stands to reason the overweight Americans will be more likely to have high cholesterol. So how, then, do they know that the "weight" is what's causing their health problems, and not, you know, the cholesterol that tends to go with it? Have there been any studies on people who became overweight by, let's say, overeating avocado? Overeating peanuts? Overeating fish? Or any other such foods that are low in saturated fat and high in unsaturated fat?
  12. Time and time again, some part of the world's forests are on fire. I've discussed in this thread the notion of a network of water pipes above the forest, and I've been told it's unfeasible. I'm not sure if that has changed, but in the meantime, I intend to focus on the other options. A. Would increased logging of temperate forests significantly reduce the amount of combustible material in the long run? I've heard it temporarily increases it before decreasing it; why is that? (I would assume they'd find use for the wood, if not by incentivizing paper use as an alternative to other materials, then by incentivizing ) B. What if they created a large criss-crossed pattern of permanent firebreaks such that the larger "forest" is then divided into a set of smaller forests, such that only one of these smaller forests can catch fire at a time, such that the forests can still use fire to replenish themselves without presenting as much of a danger to human lives?
  13. What about enough heat to boil water for cooking food? That's useful even when it's warm. Also, if every household had a concave mirror for a rooftop, more sunlight would be absorbed by the boilers and less would be absorbed by anything else. Wouldn't that reduce the urban heat island effect? Could it also reduce the city's albedo to below what that of the pre-existing natural environment would have been? As for hail being not a big deal to solar panel rooftops, how come it's such a popular anti-solar talking point? Engineering angle aside, would replacing solar panels with concave mirrors do more good to the pro-solar movement or more harm from a PR standpoint? EDIT: And in light of Australia's wildfires, should I bump the "harnessing the energy of forest fires" thread or continue that discussion here?
  14. A number of my past posts relate to hypothetical alternative sources of electrical power. I'm wondering if it'd be more efficient (pun intended) to coalesce them all into one megathread, such that people could compare and contrast these hypothetical proposals. I'd like to reiterate all these proposals, and a few new ones: A. One common criticism of household solar panel rooftops is that they're vulnerable to hail damage. I'm not sure if there's some way to mitigate this vulnerability that the fossil fuel industry doesn't want us to know or whatever, but in the meantime, since thermal solar isn't as vulnerable to hail damage, would a better approach be to have some rooftop concave mirror and/or rooftop convex/fresnel lens, to boil water? (This might also be more efficient twofold in having a direct source of heat, instead of having to convert heat into electricity and then electricity into heat.) If fire safety's the issue, would it be worthwhile to have the water supply BE the convex lens; namely, a watertight (apart from some outlet/intake tubes at the top) roof filled with water, such that the point of convergence is some dark surface within this roof that happens to be surrounded by water? B: So lightning is a form of direct current, is it not? If so, does that mean that some device designed to attract lightning, and run it through some electrolysis device, would be able to convert its electrical energy into chemical energy?
  15. In introductory chemistry at university I heard of an equation called the Clausius-Clapeyron equation relating vapour pressure to temperature of a substance. I vaguely recall hearing it applies to other liquids than just water. What I do not recall hearing is whether or not it applies solely to substances in their liquid phase. Does it apply to solids? Does it apply to solids dissolved in liquids? Does it apply to liquids dissolved in other liquids?
  16. Let's say you're graphing some function... for simplicity's sake, some quantity over time. There's a time interval that needs to be skipped because nothing happens during that time interval. What would be the proper way to skip that interval on the x-axis? I've seen zig-zags, dotted lines, etc... and I would like to be filled in on what is the correct way. Thank you in advance.
  17. What about vertical structures designed to capture the moving air and use it to turn turbines? Would that be more practical?
  18. https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/115127.shtml?cone#contents So at this moment Hurricane Dorian is forecast to make a direct hit on Lake Okeechobee. If the floodwaters extend from the lake to the ocean, they'll essentially be the same body of water. But then I remembered, lakes are connected to rivers, which are connected to the ocean. This got me thinking; where does one body of water end and the next begin? Where does a river end and the ocean begin? Is there some threshold of salinity? If so, does that mean the boundary between a river and the ocean shifts as that threshold shifts? How do we distinguish rivers from lakes/ponds? Is there some metric of the velocity of the water? Does increasing/decreasing flowrate therefore shift this boundary?
  19. Which suggests it would take a long time to turn a profit, but doesn't suggest that it won't eventually do so, especially if someone would otherwise exercise a comparable amount of time anyway. Why does no one want to invest in this?
  20. We have coal, oil, gas, nuclear, and thermal!solar power plants that work by burning these boiling water, and turning turbines. We have wind and hydroelectric power plants that use their respective fluids to turn turbines directly. And yet, when people want to work out, they get on devices that USE electricity to run a motor. Something isn't right here. Is there any way to design a treadmill and/or stationary bicycle that can generate electricity from the user's motion?
  21. Forgot about this thread until now. Here's another one. At 6 minutes and about 20 seconds in, the fish claim they're going to "roll" the bags by swimming in water that's inside the bags. I guess the idea is that they're going to swim in a line that does not cross the center of mass, but that still leaves behind a question. If in swimming forward they push water backwards, is there any way for the torque they generate by this action force to not be cancelled out by the water-pushing reaction-force?
  22. Despite my background in physics, I've never fully wrapped my head around what weight's supposed to be, other than "not the same thing as mass." It used to hardly even matter, but now I need to know for my students. For instance, if an astronaut is in orbit around the Earth, and the centripetal force is provided by gravity at precisely the right magnitude for the astronaut to feel "weightless" in this non-inertial reference frame, said astronaut would experience "weightlessness," but force of gravity would not be zero. What would be zero is the normal force, as there is no need, until the astronaut encounters an object in spite of weightlessness, for a normal force. So is weight supposed to be the normal force, the gravitational force, or something else?
  23. I ask this as a teacher, not a student... if you have three sets of parallel plates... one of +2a and +a electric potentials, one of of +a and -a electric potentials, and another of +a and 0 which has the higher potential energy? I assume it's +a and -a as it relates to potential difference, I just want to make sure.
  24. This is school related, but I ask it as a teacher, not a student. https://wikimedia.org/api/rest_v1/media/math/render/svg/8c6ee5510ba3c7d6664775c0e76b53e72468303a The above is considered the standard form of the Universal Law Of Gravitation. However, if someone gave the following... https://wikimedia.org/api/rest_v1/media/math/render/svg/ebf0689fbd05781a129e2df24ef5bd8b7edf2f93 ...except without the function notation or r-hat notation, would this count as merely derived from the Universal Law of Gravitation, or as a form of it in and of itself?
  25. One of the advantages to farming in a dry state like California is that with less rain, you have so much more sunlight. One of the disadvantages is that you have to use a hell of a lot of non-salty water just to make it work. What I'm wondering is, what's stopping it from seeping into the groundwater, and gradually shifting toward non-farmland vegetation that could use it too? I look at the fact that California is on fire again; it seems to be an annual thing; and I find it odd that such a supposedly dry state could have naturally built up enough combustible vegetation in the first place to sustain several years' worth of forest fires. I cannot think of any other state as fire-prone as California. Could irrigation have played a role in this, or am I just barking up the wrong tree?
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