• balsoft@lemmy.ml
    3·
    3 months ago
    • PM_Your_Nudes_Please@lemmy.world
      0·
      3 months ago

      The electric field one is also interesting, because the cable length doesn’t actually determine how long it takes to turn on. All that matters is the distance between the power source and the device. Electricity travels at the speed of light, which means we can measure how long it should take to travel down the wire.

      But let’s say you have a 1 light year long power cable, made out of a perfect conductor (so we don’t need to worry about power loss from things like wire resistance or heat). Then you set the power source right next to the device and turn it on. The logical person may say that the device would take a full year to turn on, because the cable is one light year long. Others may say that it will take two light years to turn on; Long enough for the electricity to make a full circuit down the cable and back to the power source again.

      But instead, the device turns on (nearly) instantly. Because the wire isn’t actually what causes the device to turn on. The device turns on because of an EM field between itself and the power source. The wire is simply facilitating the creation of that field. The only thing that matters is the distance between the source of power and the device. That distance, divided by the speed of light, is how long the device will take to turn on. If the device was a full light year away from the power source, it would take a full year to turn on. But since the device is sitting right next to the power source, it turns on right away.

      • balsoft@lemmy.ml
        2·
        3 months ago

        But instead, the device turns on (nearly) instantly. Because the wire isn’t actually what causes the device to turn on

        That’s not exactly true. In this case, the energy transmission would go like this: (change of electric field in the little bit of wire next to the power source) -> (change of magnetic field in the air between the wires) -> (change of electric field in the wire next to the load). This limits the amount of energy transmitted significantly and incurs a lot of losses, meaning if you had something like a lamp plugged in it would start glowing extremely dimly at first (think about how some cheap LED lights keep glowing even with the switch off - it’s similar, albeit it happens due to inter-wire capacitance and not induction). It would then slowly ramp up to full power over a course of a year.

        Here’s a video from the same person about it: https://www.youtube.com/watch?v=2Vrhk5OjBP8 (although I haven’t watched this yet)

        Edit: after watching the video, I think I was actually wrong in a couple of my assumptions. First of all, it looks like the reason for the initial energy transmission is wire capacitance and not induction, so (electric field in wire) -> (electric field in air) -> (electric field in wire, in the “opposite direction”, but because the wire goes back and forth it’s the same current direction). This means that my LED example is even more potent. And the second one is that because it’s capacitance and not induction, this means that there’s no slow ramp-up, it just makes the light glow very dimly all the way until the electric field makes it through the wire, and then it ramps up very quickly.

  • hOrni@lemmy.world
    2·
    3 months ago

    Not really favourite, but definitely most unbelievable: They elected Donald Trump for president in the US. Twice.

  • jet@hackertalks.comEnglish
    2·
    3 months 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

    • juliebean@lemm.ee
      2·
      3 months 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.mlEnglish
        1·
        3 months 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

  • WoodScientist@sh.itjust.worksEnglish
    2·
    3 months 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.

  • sp3ctr4l@lemmy.zipEnglish
    2·
    3 months 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.

  • ryathal@sh.itjust.works
    1·
    3 months 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.

  • randombullet@programming.dev
    1·
    3 months 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

    • balsoft@lemmy.ml
      1·
      3 months 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).

  • Resol van Lemmy@lemmy.worldEnglish
    1·
    3 months ago

    In my country, which is Morocco, the organ of love isn’t the heart, it’s the liver.

    My mom sometimes calls me “lkbida diali” which just translates to “my liver”.