• balsoft@lemmy.ml
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    9 minutes ago
  • randombullet@programming.dev
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    8 hours ago

    Consider a dam that is 10m tall

    Then consider the height of water behind that dam is 5m tall.

    Does the dam need to be built stronger if the water behind it is 1 km long?

    How about only 500m?

    How about 1m?

    The answer is, it doesn’t matter. Water exerts pressure equally regardless of how much water is behind it.

    Therefore a graduated cylinder that is 10m tall needs to resist the same amount of force as a dam 10m tall regardless of how much water is behind the dam. Even a thin sliver of water 1mm thick and 5m tall has the same force as a 5m lake behind the dam.

    Incompressible fluids are pretty insane

    • davel@lemmy.ml
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      51 minutes ago

      Thank you. Your hypothetical question has been a nagging, unresolved background radiation in my mind for decades, but I’d never gotten around to investigating.

    • balsoft@lemmy.ml
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      1 hour ago

      Therefore a graduated cylinder that is 10m tall needs to resist the same amount of force as a dam 10m tall regardless of how much water is behind the dam. Even a thin sliver of water 1mm thick and 5m tall has the same force as a 5m lake behind the dam.

      Technically only the pressures are equal, and the actual force will be linearly dependent on the area of the dam (or the surface area of the cylinder). That’s why you can make a tall water tank with relatively thin walls, but an actual dam will have to be quite thicc to handle the tensile/compressive stress (depending on the shape of the dam).

    • MajorMajormajormajor@lemmy.ca
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      5 hours ago

      That is accounting for static bodies of water, wouldn’t there be force generated in a dynamic situation? Ie the flow of a fast river? Or if the lake is large enough tidal forces? I’m sure it’s negligible levels but still something that must be accounted for?

        • xthexder@l.sw0.com
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          44 minutes ago

          Another point is that if the dam is 10m tall, it has to be built to withstand 10m of water. just because it sits at 5m most of the time doesn’t mean a heavy rain couldn’t raise the level, and if the dam collapses that’s going to be catastrophic vs just spilling over the top.

  • Commiunism@beehaw.org
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    7 hours ago

    A somewhat political fact, but one that made some of my friends dumbfounded:

    When a bank issues a loan, it generates that money literally out of thin air and credits that money to the loan account rather than using deposits they already had. For example, if you want to borrow $100,000, the banker approves the loan and doesn’t hand over cash or move existing money around - instead, they just go on their system and credit your account with the sum, that’s it.

    • faktotum@leminal.space
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      1 hour ago

      While I think your point is true that its much more abstract than people realize. When I worked at a bank and we disbursed loans and credited/debited fees it was from “GLs” (General Ledger?) which were basically just separate accounts to help keep track. Like we had a “member service” one which was for basically anything with good reason. One time someone did a very large amount but he just basically got told to do it a different way.

      Its all just in a computer. I could’ve accidentally credited someone a million dollars but it would’ve been realized when I tried to close my drawer and balance everything out. And the branch would have to be balanced at the end of the day so I assume the bank did as well.

      On a related note banks take out loans from other banks. I think a lot of people don’t realize that banks have savings accounts so they have money to lend.

  • socsa@piefed.social
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    8 hours ago

    That Mark Zuckerberg holds several records for most fists shoved inside a human body at once

  • tetris11@lemmy.ml
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    9 hours ago

    There was this racehorse named Pot-8-Os who won over 25 races and went on to sire a horse empire of winners. His father was a legend himself named “Eclipse”

    • Nakoichi [they/them]@hexbear.net
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      8 hours ago

      Did you also know that one of the first motion pictures was shot to measure the gate of a race horse by Leland Stanford, who would go on to create Stanford University where the eugenics movement would get its legs and horse breeding theories of genetic prowess were applied to humans, and subsequently they would use the Stanford University as a test bed to breed umbermensch that would go on to inspire the Nazis? Yes this sounds insane but all of it is true. Also college football became a method to study human combat ability for the US military.

      • tetris11@lemmy.ml
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        8 hours ago
        • camera → racehorse → leland → stanford → eugenics → nazis: There’s a lot there
          • camera → (developed for) → racehorse → (by) → leland: this I follow
          • eugenics → (popular in european elites with racehorse breed overtones) → nazis : this I follow
          • leland → (founded) → stanford : this I follow
          • stanford → (created) → eugenics : this I tentatively follow, but missing the gap of an entire atlantic ocean
    • POTOOOOOOOO@reddthat.comOP
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      9 hours ago

      Also an unbelievable fact, you responded to user Potoooooooo about Potoooooooo the horse.

      I really love this story about the horse.

  • WittyProfileName2 [she/her]@hexbear.net
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    10 hours ago

    The bluestones in Stonehenge come from West Wales. Instead of quarrying stone from near the monument, they dragged these huge blocks from ~278km away. Likewise, the altar stone comes from ~700km away in North-East Scotland. It must’ve been very important for the ancient Britons to’ve used these specific rocks for some reason, but their religious practices were conveyed via a now extinct oral tradition so no-one knows exactly why they did it.

    • balsoft@lemmy.ml
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      41 minutes ago

      It’s actually 0.06 microseconds (0.00000006 seconds) per day, or ~22 μs (0.000021915 s) per year.

      Also, technically, anything moving up or down in Earth’s gravitational field while physically connected to it is having an effect, however it’s usually to small to be reasonably measurable.

      (I wonder what would happen if the rotation speed was changed by 0.06 seconds per day - that feels like a lot, adding up to 22 seconds per year, but would anyone except timekeeping nerds actually notice? I don’t even know how to begin figuring something like that out.)