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Posts posted by ScienceNostalgia101

  1. Originally I was going to make this a "relative motion" thread, but I think the notion of analyzing movie physics is more interesting overall.



    In "Rat Race," a mechanic startled by the passing supersonic landspeeder fires a bullet parallel to its path. (At about a minute and a half into the clip.) To the drivers, however, the bullet appears to be suspended in mid-air, as it is moving at approximately the same velocity as the landspeeder.


    1. Would the bullet's path be kept horizontal for any non-negligible amount of time by air resistance, or would the vertical component of its motion immediately assume downward acceleration like everything else?


    2. How quickly would the horizontal component of its motion be slowed by air resistance?


    3. Either way, would it be safe for the drivers of this landspeeder to reach out of the window and grab the bullet, provided they maintained the same velocity as the bullet while it was in contact with their hands?

  2. This isn't meant to endorse such a project, just speculate on whether or not it's possible.


    Suppose Earth disposed of all its nuclear weapons by firing them at Mars or at craters on the moon. The thermal radiation would presumably be at least partly absorbed. Would there be a layer of molten rock that would then solidify in a semi-spherical shape perpendicular to these planets' gravity, sort of like the almost-flat manner in which ponds freeze over, or would it just sublimate directly into gas?


    If the former, would this be functionally equivalent to a convex mirror? Would we then have a "virtual image" of the sun at night that would be smaller than the sun and brighter than the moon, and/or contain the same proportion of colours of the sun's spectrum? Or is the moon's absorption of UV rays more a function of its moon rock material than of its diffuse-reflective nature?

  3. I felt reminded of this thread by another thread.


    I now have another follow-up question; what kind of materials would a town/state/country need in order to make these kinds of solar collectors (relatively) inexpensively? Would used tinfoil be useful for them? Apart from tinfoil, would it be more expensive, or less, to melt down old aluminum cans to make them, or to purchase cast aluminum in bulk for the same purpose? Are maintenance costs comparable to nuclear or lower?

  4. Here's what I've been thinking about lately. If solar collectors can store excess energy as molten salt...


    ...and electricity can be used to melt metal...


    ... why can't they use "molten metal storage" and/or "molten salt storage" from excess electricity as a whole to store energy?


    Or alternatively, what about desalinization of water? California has massive problems with shortages of clean water, and desalinizing water would strain the power grid, so why not use excess energy to store up huge reservoirs of desalinized water so you can shut down desalinization plants when electricity is scarce?

  5. So I was recently thinking about solar angles. A fairly straightforward, everyday example of solar angles.


    Or so you'd think.


    However, recently one thing came to mind. Suppose it was 6 hours before or after noon during a fall or spring equinox (for our purposes it wouldn't matter) at the equator. Since it was "halfway" between sun-over-the-horizon and sun-overhead, I presume the solar angle would be 45 degrees, right?


    Now suppose at the same time someone else was, let's say, at 45 degrees latitude; (north or south for our purposes wouldn't matter) at the same time. How would one determine, then, what the solar angle there would be? Is there some sort of angular equivalent of the "vector components" used in physics and in linear algebra? If so, what would these angular equivalents be, and how would you add them to determine the combined effects of time of day and degrees of latitude on solar angle?

  6. There are a number of factors in whether or not a particular reaction will occur between chemicals, and/or the extent to which it will. An introductory course in chemistry, even at the university level, goes into Gibbs energy, but never goes so far as to say whether or not it's adequate to predict whether or not any given reaction will occur. (If I had my time back, I'd have asked, but as an undergraduate I was only concerned with getting through it.)


    Does whether or not a spontaneous reaction will occur depend solely upon the Gibbs energy and activation barrier? Is there software out there that can predict for us the reactions between any combinations of chemicals (ie. so a science teacher doesn't have to try them all to decide which looks the most interesting) or is that prohibited for fear of someone misusing it? And what of non-spontaneous reactions? Is there likewise any "formula" and/or software for predicting the products of electrolysis or no?

  7. Okay, being that it's been a month I don't want franco's thread to go to waste... that and I've been thinking lately about this myself too.




    At 5 and a half minutes in, the narrator talks about the Kola superdeep borehole, which was halted only 1/3 of the way through the Earth's crust because at 180 celsius it was too hot for the drill to operate further. If one were to pour substances that had boiling points, even at high pressure, of less than 180 centigrade, down into that hole, could they have used the expansion due to boiling to generate power and/or bring the temperature down?

  8. 1 hour ago, Strange said:

    What bashing? Please provide some examples so we know what you are talking about 

    Who told you that? Robots are already doing many jobs and, in future, will probably do many more. 


    Well, for starters, conservative pundit Gavin McInnes insists he's always called everything that isn't STEM "Marxist-Leninist brainwashing school" and blamed parents who sent kids there for them going into student debt. His fandom, which correlates with the large voting blocs of conservatives with whom colleges have to compromise in order to receive voter support for public funding, seems to for the most part agree with this.


    More broadly, TV news in general from time to time talks about automation and the replacing of old jobs with new jobs maintaining the robots that do the old jobs, but no particular names come to mind.

  9. I'm talking about how the usual reasoning for such bashing of every other degree program (though I more often hear it from conservative pundits than from actual engineers, granted) was about how we'll always need technology, yet now I'm being told using engineering to design robots to do the other jobs is unfeasible.

  10. So I'm reviewing my rules of radicals prior to teaching it to students, and found out I'm a little rusty on them.

    Suppose you hit an answer that ends with a prime number as your radicand. Provided you used mathematically valid reasoning to get there, does this prime-number radicand now suggest that you arrived at the most simplified form, or are there "dead ends" distinct from the right answer?

  11. On 9/12/2018 at 6:36 AM, Sensei said:

    You (and I!), are too used to software engineers.. :)

    In my description, I was thinking about building engineer. Somebody who is managing group of workers to make building, or something like that.



    Somebody who is responsible for finishing building project at a right time, within budget..


    "Software engineer" I am simply calling "programmer", therefor misunderstanding.. :)

    (including "senior software engineer" aka "project manager" etc. etc.)


    So the same question applies. Can there be too many engineers, even if a large enough fraction of them are software engineers hired by a government program designed to make as many other jobs obsolete as possible?


    (Forgot I even had this thread until now, sorry about that.)

  12. So I was recently thinking about the similarity in formulae between spheres' volume (4*pi*r*r*r/3) and their surface area. (4*pi*r*r)


    Firstly, I noticed that the surface area looks like it's the derivative of volume with respect to radius... which come to think of it makes sense as the rate of change in volume at a point in time is that outer spherical shell being added times its thickness.


    But secondly I also noticed that the ratio of the two is r/3. As in, as if the average particle in a sphere were only a 1/3 of the way to the outside.


    More generally, V/A is in length units. Am I figuring this right? Does V/A represent average distance, root mean square distance, or whatever other measure of central tendency from center to outside?


    More generally than that, how is this extrapolated to other shapes? Does V/A represent anything in particular more generally or is its dimensionality usually meaningless?

  13. Majoring in engineering's kind of a damned-if-you-do, damned-if-you-don't these days.


    If you major in engineering, you're told there's an excess of engineers anyway and it's on you if you don't find a job with it.


    If you DON'T major in engineering in, you're trash-talked on the basis of whatever else you studied supposedly being worthless.


    What I'm wondering is, how can there be too many engineers in the first place? Surely all those other jobs could eventually be done by robots, and the more engineers we have, the sooner we'll get there. Why isn't the government hiring the "excess" engineers to design robots to do all the other jobs?

  14. https://www.nhc.noaa.gov/gtwo.php?basin=atlc&fdays=2


    See, this is the kind of thing I was talking about earlier in the thread. Right now, off the coast of Cancun, Mexico, there's a storm brewing that has a 50-50 chance of developing further, on top of all the other storms the North American continent is about to face in the near future.


    Cancun is about 200km from the west coast of Cuba, while Key West, Florida, is about 150km north from Havana, Cuba. If we had rows of interconnected floating wind turbines along at least those stretches of ocean, to harvest the wind while it was still gale force, would at least somewhat cut down on hurricane development?

  15. http://www.hawaiinewsnow.com/story/38954656/brush-fire-in-lahaina-prompts-evacuations


    So apparently, in spite of the rain, wildfires are raging in Hawaii. There's plenty of water... it's just that most of it's not fit to drink.


    It seems inefficient to have to choose between "using tap water that had to be processed on the taxpayers' dime to be fit to drink, on a fire that can be put out just as effectively with impure water," and "trucking impure water from the flood to the fire." Why can't there be two separate sets of infrastructure; one for water that's pure enough to drink, and another that's adequate for firefighting purposes and doesn't have to be processed?

  16. They're hundreds of kilometres wide... so definitely tens of thousands, probably hundreds of thousands, of square kilometres.


    How efficiently could offshore wind turbines be mass-manufactured in assembly lines if we took all possible money away from building any other type of power plant? (Ie. Coal, oil, natural gas, solar, geothermal, hydroelectric and nuclear?)

  17. Wasn't sure whether to take this to the physics or chemistry forum, as it involves both, but for now I'll put it here.




    • Hurricane Lane will create "whiteout conditions," life-threatening flash floods and landslides as it hits the Kilauea volcano.
    • When it hits the lava, the rain creates steam that's loaded with particles and toxic gases, such as hydrochloric acid.
    • In 2013, eruptions from Kilauea increased the intensity of thunderstorms and lightning around Tropical Storm Flossie.

    Why would lava contain hydrochloric acid? Wouldn't hydrogen chloride be more likely to come out of solution at the higher temperatures of lava than at the lower temperatures of rain-cooled lava?


    Or does it dissolve-without-dissociating in lava, then react with rainwater to form hydrochloric acid?


    I was expecting this to be an "at least we won't have to worry about the lava once the water freezes it, or about the ash once the rainwater dissolves it" situation. So much for that...

  18. Bumping because of Hurricane Lane. (It's been a week and a day since the other post.)


    Another question now; if they had enough rows of offshore wind turbines, harvesting about 3/5 of the wind energy at every row, would they be able to prevent hurricanes from forming in the first place?

  19. 6 hours ago, Sensei said:

    The easiest thing would be to let microorganisms consume it and build their cells and sugar, which eventually could be fermented to produce ethanol, and release more CO2 (which will be reused by microorganisms in 1st stage).. Ethanol would have organic origin, so it could be consumed, or used as a cheap fuel, or used to produce acetylene C2H2, which could be used in e.g. chemistry industry as precursor to e.g. plastic.

    That actually sounds like a pretty damn good idea.


    Would any of us be entitled to a slice (however small) of the profits if they ever used it?

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