ScienceNostalgia101

Okay, another question now. What would be a good foundation for such a solar collector? I'm hearing that a halfpipe costs a minimum of $800 to build. Is there any cheaper alternative onto which I can place the tinfoil and still concentrate sunlight comparably well?

So last time I was in China (more than a year ago, I assure you) I noticed what appeared to be farmland from the balcony of an apartment building more than a dozen stories high. This apartment building wasn't exactly in the middle of town, but it was along the outskirts of a major city, with a major supermarket nearby, so it was clearly in an at least somewhat urban setting. This is weird because from debates over big cities vs small towns, you always see advocates of the latter say things like "we farm your crops!" So I'm wondering; is this done for medical reasons, or just economic ones? Is urban land too polluted for any first-world democracy to find it acceptable to get our food from it, (China isn't known for food safety as recent events have shown) is the crowding considered a pathogen-spread risk, or is it just a matter of first-world urban land values being too expensive for farming? Or is there something else I'm missing?

What if I had a smaller dish (ie. 1/4 cup metallic measuring cup) in which to put the hot water? Could the effect of covering most of the top surface with a spoon almost as large as the top surface, and filling the spoon with olive oil, still be considered negligible then?

Well, for starters I live in a town where the solar noon is presently 24 degrees and decreasing. So... sin(24)=0.4, about. Multiply that by 1368 watts per square metre and you get 556 watts per square metre. I most definitely wouldn't go for the Fresnel-lens approach, more like, approximating the shape of a concave mirror through several flat mirrors. (Ie. Half an octagonal prism instead of a half-cylinder... or something like that.) So obviously all 8 sides of an octagonal prism wouldn't equally reflect light onto the water boiler, as they wouldn't have the same angle with the sun's rays. So it'd be not less than or equal to 556, but strictly less. Where would I find information on the rate at which wood absorbs energy from sunlight? Of course, thus far this is presuming I bring the concave mirror/solar collector back inside by February, which I doubt. Odds are I'd need to use a solar angle corresponding to sometime between February and May, as I don't want to have to put away a valuable source of heat energy. This is just more so to figure out whether or not I'm on the right track before I take this idea any further.

So I've recently been getting back into my fascination with concave mirrors, and was considering using them and/or some other means of a solar collector for boiling water as we get closer and closer to those winter months. However, before I float this with my landlord and/or boss for my home and/or workplace, I want to make sure I can keep potential fire hazards to a minimum. A. If I make a concave mirror whose focal point is inside the mirror (ie. half-sphere concave mirror) does that mean that there is no risk of it causing a fire if it falls off the balcony or comes loose? B. If I were to instead of using a concave mirror, use a marginally less efficient arrangement of several flat mirrors pointed at the same water-boiler, would that be free of potential for fire hazard? Would it depend on whether I used an actual mirror or just covered several flat surfaces in aluminum?

So recently I've been putting olive oil in a spoon floating in boiling water in a metal dish so that it gets warm enough to put in my ears. I assume the oil will warm as the water transfers heat to it, then cool as the water cools, (or at the very least is not transferring enough energy to the oil to outweigh the rate at which the oil loses heat energy) but I don't know how to predict when the oil will hit its warmest temperature. I figure I could one day set aside the spoon and put a thermometer in boiling water in a metal dish (though I keep forgetting to buy an actual themometer) to gauge how long it would take to cool without having to heat up the olive oil at the same time. However, I'm also wondering... is it possible that instead of cooling slower, the water cools faster, as there's no spoon or olive oil to "insulate" the temperature drop? What factors would need to be taken into consideration in determining how long it takes to max out in temperature, and how that differs between with or without a spoon with olive oil?

Disclaimer: If I ever try this, I will try it only on a teaspoon at a time, and ensure adequate time to be as certain as possible I am not getting severely intoxicated off the vapour. I do not recommend vaping alcohol in a general sense; this is more about the scent than the extent of drunkenness. There are some interesting smells from some alcoholic beverages, but leaning in the scent is only so strong. I've heard the boiling point of pure ethanol is 78.37 degrees centigrade... probably boiling point elevated when it's part of a solution, but still I presume from Clausius-Clapeyron that its vapour pressure increases more rapidly than that of water when heated. I'm curious whether increasing its temperature; such as, let's say, from a spoonful of liquor floating in hot water; would, as per Clausius-Clapeyron, increase the extent of the scent, but I'm also a little concerned about whether any of the other chemicals present than just the water and the ethanol could theoretically also be increased to harmful concentrations, with less pleasant effects. Does it depend on the liquor involved? Would doing this with, let's say, rum, work differently than doing this with whisky?

Why not suspend travel until adequate facilities are built?

So seeing as how international travel helped spread coronavirus in the first place, obviously the most practical measure would've been to cut off the disease at the source. But I'm wondering... if instead of an outright ban, international travellers were met with a tunnel directly from the airplane to a series of quarantine rooms; with one entrance from the tunnel, and one exit into the rest of society; and no access to the exit until one has gone through a 14-day quarantine, then a first hermetically sealed door, gotten tested for it, tested negative, then a second hermetically sealed door and then out into society; would that have been just as effective in spreading the disease in the first place? If so, does that mean those who failed to implement this policy should be ignored on what to do about future pandemics or no? Because we tried the "self-isolate when you come back" thing, and because of a few reckless scumbags who didn't actually DO that, hundreds of thousands of people are dead. We'll need something more foolproof next time.

I like to bring my toothbrush to work and brush my teeth at work, but sometimes I forget to bring my toothbrush. I was going to leave one at work, but I can't leave it in an airtight safe or it won't dry properly, and I can't just leave it on a cup in the office because I don't know if my coworkers might use it and I might catch whatever diseases they may have. Is there any lockable container I can put something in, that I need a key and/or combination to access, but that allows anything put in it to dry out?

Disclaimer: I do NOT presently intend to actually attempt this myself, NOR would any future attempt at this myself hinge exclusively or even primarily on the direction of this thread. Obviously if I were to ever become a stuntman in the future I would consult with actual experts. For now, this is intended primarily out of curiosity. I do not recommend this for anyone without consultation with actual experts as even to a layman there are a bunch of obvious issues (debris on the road, tripping up and falling face flat on a moving road) that could go wrong. Suppose someone wearing roller blades, or riding a skateboard or bicycle, or whatever else (presume an abundance of safety gear; and perhaps some springs between their multiple suits of armor) attached a spring, or a bungee cord, or a spring attached to a bungee cord, so as to connect themselves or their bicycle to a motor vehicle like a car. Whether for the thrill of it, or as a semi-convenient means to transport their bicycle for lack of room in the car, or both. I presume the non-motorized vehicle would get infinitesimally closer and closer in both acceleration and velocity to that of the motorized vehicle, as there is only so much a spring or bungee cord can stretch. But I'm kind of stuck on how to figure out what the acceleration would be as the vehicle begins to move. Obviously there would be a major gap in both acceleration and velocity as the bungee cord and/or spring stretched to accommodate the fact that the vehicle in front is driving the motion and the non-motorized vehicle is just acting as a load. How much of a gap will that be? All I have right now is that the only force acting forward on the non motorized vehicle is F=-kx; and that the only one acting backwards on it is friction. I have no idea how to figure out what the next step is. I presume from the nature of the question that it's plentifully obvious this is neither a homework question nor a lesson planning question.

So I was recently thinking about this P&T:BS episode from a few years ago. Having been an environmentalist in childhood, I at first found it jarring, but eventually refreshing, to see perspectives openly dissenting against the conventional wisdom on environmentalism with which I had been brought up. Is Penn Jillette right on this one, though? I'm just thinking if you're going to be growing trees to make paper, and if those trees are going to die anyway if not chopped down to make paper, then one might as well combust the paper underneath a kettle to boil water in a rural/suburban setting. Still not sure what the best possible use of waste paper would be in a more urban setting, though. For the record, this same episode endorses aluminum recycling, and doesn't weigh in specifically on glass or plastic recycling. However, it does end on a scene about a landfill in California that uses the methane from active decomposition for energy. Would this be comparable to, better than, or worse than, the idea of combusting the waste directly? I would guess it would be at least slightly better, if only for the fact that energy from combustion doesn't have to be consumed by the need to dry out wet organic waste before it can catch fire. But if so, how come this isn't the norm for landfills, if only to address landfills' collective reputation for being a climate hazard?

So recently I was watching a movie (I'll not specify which in the interest of avoiding spoilers) where a character claims she'll curse another character's name until the day she dies, and then the character dies that same day. I know it sounds pedantic as all hell, but it got me wondering whether what she said was technically true. For the word "until" to be applicable in a discrete context, would more than one day have to be involved, or would one-day intervals also count? More generally, would "until" have to include the end date in the interval? I'm going to leave this thread open to other words as well, in case others are wondering about how other words' mathematical definitions compare/contrast with their common ones. (Although I probably will wonder about them myself.)

Good to know, thanks. Does anyone have a source in mind confirming as much such that I can cite it elsewhere if need be?

Roads are often the go-to example of things that need to be a public service. I've always thought health care was a stronger example, given what happens in countries where it's public vs. where it's not, but I'm willing to entertain the idea that roads are a better one. For the purposes of this thread, I want to put aside all concerns about whether toll roads are unfair to the poor in and of themselves. It's not that I want to trivialize that; I'm absolutely concerned about it and I think both Canada and the USA could do with a stronger public sector; but there was one specific aspect of road privatization that stands out to be more than its effects on the poor: what happens when you have a grid structure in a city? Let's say, first street, second street, etc... intersecting with first avenue, second avenue, etc. Assume each of these roads are built by a separate company. Who then gets to run the intersections between these roads? Would it have to be a venture done jointly? If so, who gets to decide who gets the final say in some paving/streetlight placement/etc... decision in the context of these intersections? Would territory be demarked in an sealed-letter-like pattern? Even so, what rules would govern left turns, right, turns, etc...? And at the end of the day, what's stopping the company behind, let's say, first street, from colluding with the company behind, let's say, first avenue, to make their intersections with second street or second avenue harder to use?

So when crude oil is refined, it is separated into different products. Some of it is used to make gasoline, some of it is used to make plastic, and I assume the rest of it us used for everything in between. And yet, I often hear of how gasoline is "not the best use" of oil and how plastic would be so much more reusable. But if different parts of the oil are used to make different products, how can that which was not channelled toward making gasoline be repurposed toward plastics?

https://imgs.xkcd.com/comics/nerd_sniping.png So this XKCD comic got me thinking... can the resistance of an electrolytic solution in water can be modeled as infinitely many resistors of infintesimal resistance? After all, the distance between the ions of electrolyte is a discrete quantity, but so is the number of said ions; or the number of water molecules between them; and we still model these things as continuous fluids. So obviously the resistors are in parallel; there are pseudo-infinitely many paths they can take. But no matter what path they take they have to jump between ions several times, so it's also in series. Is there any formula that could account for the combined series-and-parallel nature of a circuit through an electolytic solution? . . . Why yes, I did dream last night that I was caught in a thunderstorm with the car windows only partially rolled up, how could you tell?

How would such a buffer put people in danger?

Encouraging alternatives to meat until we improve our healthcare system then sounds like it's a good way to make a dent in climate change and new pandemics alike.

Got it, thanks! Speaking of The Simpsons... DISCLAIMER: I would not try this at home. NOR at any convenience store, for that matter. However, it reminds me of my curiosity about the issue of cryonics. I'm not sure who to believe on this issue. There are those who claim there are ways to survive being cryogenically frozen, if society would invest in them. Others dismiss it as hopeless. Are the former just wishfully thinking? Are the latter just trying to stop cryonics from cutting in on religion's afterlife action? If I found a professional service to freeze my body, would it be safer to do it immediately after death, immediately before death, or significantly before death in the context of some terminal illness or whatever? (Obviously I'm not going to cut drastically short whatever life I have now just on the offchance of being revived later.)

Man, so many of the things I thought were no-brainers were a hell of a lot more nuanced than I thought. Very well, then. So what's the real solution to the current forest fires? More prescribed burns? More permanent firebreaks? Or just leaving California permanently and putting a giant pot of water over it hoping the boiling will make it pay for itself?

Once again, California is on fire. Apart from the threats to property and safety, that's a lot of chemical energy in nature that is being squandered on a fire that isn't occurring underneath a boiler to boil water for food or electricity. I wonder, now... if society were to hire more of the recently-unemployed as loggers, and have them cut down enough trees that the wood could be burned in lieu of fossil fuels, (and/or be converted to paper and used as such before being burned) would this double as a way to make forest fires less severe, by the fact that there are fewer trees available, per square kilometre, to catch fire in the first place?

But in many smaller cities, where space is not as limited, two-way streets are still the norm, not the exception. Might lives be saved in the long run if we switched to one-way and took away the "basic human judgment" factor on when/where it's safe to turn left?

So long as two-way roads have a grid structure, every intersection will include an option for turning left a green light. And every time a driver makes a judgment call on whether or not it's safe to do so, this risks getting them killed. I'm just wondering, wouldn't one-way streets create fewer options, per intersection, on which way to turn? For instance, if a north-heading street met an east-heading street, the north-heading cars could only turn right onto the east-heading street, not left. The east-heading cars could only turn left onto the north-heading one, sure, but you could also reserve one lane for traffic that is "joining" the street, such that they only merge into the traffic when they've caught up. Is there anything to go on as to whether or not replacing our existing grids of two-way streets with grids of one-way streets would constitute a net improvement in safet?

Incidentally, I'm type 1 diabetic myself. So frequent eating of sugars and starches without protein to go with it contributes to type 2 diabetes even if the person eats in moderation and/or exercises to burn it off?