• randombullet
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    6 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

    • MajorMajormajormajor@lemmy.ca
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      4 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?

      • randombullet
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        3 hours ago

        No, that’s absolutely true. Dynamic loads will need to be accounted for in real world examples.

  • Commiunism@beehaw.org
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    5 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.

  • socsa@piefed.social
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    6 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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    8 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”

  • WoodScientist@sh.itjust.works
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    13 hours ago

    Due to two facts:

    1. The samurai class in Japan officially lasted way later than you probably think

    2. The earliest primitive fax machine existed much earlier than you probably think.

    It is technically possible for Abraham Lincoln to have received a fax from a samurai.

    There’s no evidence it ever happened, but it technically could have happened.

    • SwingingTheLamp@midwest.social
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      12 hours ago

      For some reason that reminds me of how the first member of the Wampanoag tribe to greet the Pilgrims at Plymouth Colony, named Samoset, spoke to them in English. Then he came back later with another tribe member, Squanto, who also spoke English.

      • Captain Aggravated@sh.itjust.works
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        9 hours ago

        1840s, actually. The patent was granted to a Scottish man named Alexander Bain.

        First thing’s first, the telegraph. An electric circuit which can be energized or not energized at the push of a button called a telegraph key. At the other end is a solenoid which is spring loaded up, and an electromagnet on the circuit pulls down when the line is energized. Originally this was supposed to cut into paper tape to “print” the morse code message, but telegraphers quickly learned how to hear the letters in the clicks, a good telegrapher just…hears words. So they did away with the tape.

        Morse code telegraphs require a single circuit to transmit an on/off keying message, the following aparatus uses five:

        If I understand this right, the message would be written on non-conductive paper with conductive ink, and then wound around a cylinder that featured a whole bunch of insulated conductive pins, each kind of forming a “pixel.” A mechanical probe would check each one of those pins in turn, each pin in a row, and then shifting to the next row at the end. if it was conductive it meant there was ink there so click. So it would perform a raster scan. At the other end was paper that was coated with an electrosensitive material that would darken with the application of current, so at each pixel if the conductive ink on the original completed a circuit, current would be applied at that pixel on the copy, producing a low quality probably unusable copy. It was difficult to get them truly in sync plus it would have been hilariously low resolution. But it did somewhat function.

  • Elise@beehaw.org
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    11 hours ago

    Bees kill invaders in their nest by climbing all over them and shaking their bodies.

  • sp3ctr4l@lemmy.zip
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    14 hours ago

    I’d have to pick between two things that sound like insane conspiracy theory nonsense, but are actually true.

    1 - George W Bush’s grandfather Prescott Bush literally ran a massive bank before / during WW2 that was shut down by the FBI for money laundering massive sums to the literal Nazis.

    …in the same vein…

    2 - IBM literally built and operated (as in, sent employees to Germany to operate the machines) the computers used by the Nazis to tabulate and do the ‘accounting’ of the Holocaust. The numbers tattooed on concentration/desth camp victims are very likely UIDs from these IBM systems.

    … If an actual, real AGI ever gains self awareness and sentience, I would imagine one of the first things it would do would be to study the history of computing itself to figure out how it came to be.

    And it will find that its ancestors were basically invented to compute artillery firing range tables, to encrypt and decrypt military intelligence, commit a genocide, and guide early weapons of mass destruction to their targets.

  • SwingingTheLamp@midwest.social
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    12 hours ago

    James Blunt possibly prevented the start of World War 3. (But became best known for the song You’re Beautiful. Reality is weird.)

    • Berttheduck@lemmy.ml
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      12 hours ago

      Care to expand on that one? I know he’s ex military but haven’t heard anything like that before.

      • SwingingTheLamp@midwest.social
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        12 hours ago

        It’s explained on his Wikipedia page. He was an Army captain in the Kosovo War, when a NATO commander (Wesley Clark, who later ran for President) ordered his unit to secure Pristina Airport, which Russian troops had already occupied. Blunt refused to engage them, long enough for the British general get involved to countermand the order, on the grounds that he didn’t want his men to start WW3.

  • ryathal@sh.itjust.works
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    16 hours ago

    Lots of people know a broken clock is right twice per day, but many are unaware that a clock running backwards is right 4 times per day.

    • tetris11@lemmy.ml
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      7 hours ago

      a clock running backwards is moving away from the current time at twice the rate, so isn’t your example the same as saying that a clock that runs twice as fast is right 4 times a day?

      • ryathal@sh.itjust.works
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        5 hours ago

        No, if you go twice as fast, it would only align with one at 12 and one at 24. It’s not about speed, it’s about the intersections of forward and backward laps.

          • ryathal@sh.itjust.works
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            25 minutes ago

            You can picture a clock or a track. If you have one going forward and one backwards, they meet at the halfway point (6), and again at the full lap (12). This happens twice in a day.

            If you have one going twice as fast, they only meet when the faster one laps the slower one. The two clocks would be at 3&6, 6&12, 9&6(18), 12&12(24)

    • lemmy689@lemmy.sdf.org
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      16 hours ago

      Most frequent occurence is the mode. Most ppl have 10. The median would be less than ten, while the mean average is skewed down, I would think, by some people losing fingers as the grow. Having extra fingers is pretty rare. So the mean might be 9.95 fingers, just to toss a number out.

      • tetris11@lemmy.ml
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        7 hours ago

        Mode assumes categorical data and is unbounded by range, whereas median makes the most sense for decimal numbers, albeit with rounding in this case

        “People have round(median(data)) fingers”

        edit: though, if we’re counting just fingers and not counting half-fingers, then maybe this really is categorical data (¯\(ツ)/¯?)

      • davidgro@lemmy.world
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        12 hours ago

        For 10 to not be the median it would also have to not be the case for the majority of people (just the plurality at best), and while I don’t have proof handy I’m pretty sure a vast majority have exactly 10, making that the precise median and the mode. Only the mean would be a different number of digits. (Both definitions)

      • bamboo@lemmy.blahaj.zone
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        14 hours ago

        I assume the median and mode are the same value, 10 fingers, but have no data to back that up. I guess saying mode would have been a safer statement to make, but think that even if 49% of people have 0-9 fingers, the median number of fingers would still be 10.

  • jet@hackertalks.com
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    16 hours ago

    Every eye has a tiny blind spot near the middle. But your brain makes it disappear and you don’t realize it’s there.

    You can verify this. Draw a dot on a bit of paper. Close one eye, stare at a fixed point, now move the paper around the center until the dot disappears…magic

    What we consider reality, is a synthesis our brain is presenting to us, it is an approximation… realizing that is a real mind blower

    • RisingSwell@lemmy.dbzer0.com
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      9 hours ago

      Oh I thought my eyes were fucked. I look at a star in my periphery and it’s there, I look at it directly and it’s fucking gone.

    • juliebean@lemm.ee
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      12 hours ago

      fun fact: the blind spot is because our optical sensors are installed backwards and that hole is so the optic nerve can pass back through the back of the eye to the brain. some other critters with independently evolved vision systems, such as cephalopods, avoided this particular evolutionary pitfall.

      • murmelade@lemmy.ml
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        11 hours ago

        Another fun fact: through that hole there’s also vasculature and capillaries coming through and you can actually see them by looking at a well lit white surface and creating a tiny pinhole with your hand right in front of your eye and wiggling it. Better explained here at around 5:30

    • Tetsuo@jlai.lu
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      9 hours ago

      Also we only see the past since our vision has a bit of “latency”.

      So I guess we never see reality but just a delayed representation of our environment as interpreted by our brain.

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      16 hours ago

      I’m going to qualify this—all vertebrate eyes have a blind spot. Cephalopods also have eyes that are like vertebrates (this type of eye is called ‘camera eyes’), but their eye anatomy is such that no blind spot exists for them.

      Piggybacking on your fact about the brain effectively editing what we visually perceive, we don’t see our nose (unless you made a concerted effort to look at it) because the brain ignores it.

    • bobs_monkey@lemm.ee
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      15 hours ago

      What we consider reality, is a synthesis our brain is presenting to us, it is an approximation…

      It’s also a coordinated synthesis from all of your input senses (sight, hearing, smell, etc). It also explains why those who have a certain sense stunted (aka blindness, deaf, etc) report having all their other senses heightened. And it’s up to the individual’s brain to assemble those sensory inputs into a complete picture of the world around them, what we dub “reality.” Which then brings into question the nature of common reality, and what defines it. Trippy shit.