The British power grid coordinates commercial breaks with the BBC, because they have a dedicated reactor that spins up 1min before the commercial starts and the entire goddamn country gets up and puts the kettle on.
The reason Babylonian ziggurat, Mesoamerican ziggurat, and Egyptian pyramids all look the same is because they're built at more or less the repose angle of stone. They didn't trade notes; that's just how you build rock piles that don't fall down.
One of the reasons stereotypical "Renaissance men" were so widely skilled was because musical instruments are insanely complex to engineer, and so being a musician was a requisite for practicing engineering. Same for music theory and mathematics.
The Navy used, and still has operational, geared computers that took in data about ocean and wind conditions in order to compute firing solutions for shipboard artillery. It took until the mid-70s in order for them to be displaced by electronic machines.
The development of gears has done more for the advancement of human technology than any other pursuit, peered only by the transistor. Clocks and automotive drivetrains are some of the most complex compact systems humans have deployed in scale.
Submarines at depth use an Inertial Navigation System that is basically a very large ball in oil with springs surrounding it. When the sub moves, the ball's momentum doesn't change right away, and it pushes on the springs. This allows measurement of the momentum change.
Naval research labs placed large masses of various metals on the seafloor in the '50s and '60s. Since then, the dissolved metals in seawater have precipitated onto them faster than the seawater has dissolved them, and they've grown significantly.
Satellites in the presence of a strong magnetic field, like Earth's, can CHEAT. We install special electrical coils that we call Magnetorquers(TM) because is that not the coolest word you've read today.
Speaking of light, photons don't travel through matter.
Lenses work because light strikes an atom and is absorbed, causing an electron to jump up a valence level. It takes non-zero time for that electron to fall back down, and when it does, it emits a photon.
Lenses also don't give you energy for free. You can't actually focus the source light to a single point, because that would violate thermodynamics. This is why you can't start fires through a telescope with moonlight, no matter how finely you focus.
You think trains go "click clack" because railways used to leave gaps between rail spars for expansion. We solved that by (a) building in the summer and (b) putting the rails under kilopascals of tension. This solves the buckling problem and the noise problem.
SCUBA-qualified air compressors use electrostatic and chemical filters, as well as physical, because they must produce air that is PURELY dinitrogen and dioxygen, plus a noble gas like helium or argon. Any other particle or gas will kill you (faster).
Satellites in low earth orbit have ~90 minute orbital periods, with ~30 minutes in full eclipse and ~60 in some sunlight. This causes an annoying thermal cycle, causing the metal in the computers to do weird things like grow whiskers.
Whisker growth is a combination of crystal impurities, vacuum, and thermal cycling. The metal traces in PCBs or wires can grow hairs that cause shorts and kill the satellite. We mediate this by spraying plastic coating over everything, so the metal has nowhere to go.
Eli Whitney's cotton gin is the classic example of industrial agriculture, but in truth it's the plowshare that revolutionized farming. Once we moved past the classic medieval yoked plow into more complex designs, productivity per person exploded.
Complex plows required industrialized metalworking, which is why they didn't appear until the late 1700s. They were further empowered by the spread of combustion engines able to replace animal labor, in the mid 1800s.
The easiest way to dilute gold money is to melt it, mix in other metal, and recast. But, other metals are lighter, so the alloy is less dense. Equivalent mass will be larger; equivalent volume will be lighter.
This was discovered by Archimedes, though it is not his eponymous principle. Archimedes' Principle is what keeps boats and zeppelins working. Archimedes used it as a solution for a (likely hypothetical) question about determining gold adulteration.
We consider space to begin at 100km altitude because that's where the air becomes so thin that the speed required to maintain aerodynamic flight surpasses the orbital velocity at that height. It's harder to be an airplane than a satellite here.
Specifically, Rome said "water can't flow uphill, so we're going to make a continuous downhill slope from the mountaintop collection points to our cities, and it will never go uphill ever" and made the aqueducts to fit.
I beams (shaped like ][ ) are used because the wide top and bottom resist torque, the load goes through the centerline, and the rest of the beam does no work. The beam performs better without the excess mass load, even.
The reason we put vertical steel rods in concrete, without tension, is because while concrete can tolerate absolute compressive force, it is less good at compressive pressure. The steel takes disproportionate pressure load while the concrete handles most of the force.
This allows for a reduction in pillar size without sacrificing overall load-bearing capacity. Furthermore, sideways forces are distributed through the steel rod, reducing likelihood of cracking from those loads.
Call this 51. The flying buttress was developed in Gothic architecture to hold up massive cathedrals whose roof and wind loads would otherwise blow out the walls and collapse. It's what enabled the advent of buildings with such massive open interiors.
52. While sprung siege engines, such as the onager, ballista, and catapult, have been known since antiquity, the trebuchet is the first European counterweight-driven engine and vastly changed the field of warfare.
53. Speaking of artillery, WWII-era battleships had guns up to 13" caliber firing half-ton projectiles. This is a mass on the order of a Volkswagen Beetle. We stopped doing this on boats when we got better at aerial bombardment.
54. Commercial aviation is a miracle of scheduling and planning to rival the actual engineering of the planes. I have mad, mad respect for the people who make the complex web of flight plans across the country and globe work.
54 cont: Flights are loaded with fuel to optimize fuel usage and efficiency for the trip. This requires assumptions about plane weight, and if the plane is underfilled it performs *worse*. This is why I flew for free until last year.
54 cont: If Delta could get another 150lb on the plane, it would raise the engine efficiency and save fuel, so even though I didn't buy a ticket I was still saving them money. Perks of having two parents in the aviation business.
55. Commercial lumber is impregnated with copper particles in order to make it toxic to rot-inducing microorganisms. This is done in a high pressure treatment which also improves the lumber's structural properties.
56. If you live in America, your floor (if not at ground level) is probably rated to support flooding of no more than seven to eight inches of water. In fairness, seven inches of water is really heavy.
57. Most residential lumber is one of a couple species of pine or fir. These trees grow straight and at a reasonably rapid pace. These woods are soft and flexible, which is one reason houses creak, but they're very hard to actually break.
59. Diesel trains are not trucks. The diesel engine runs a generator, and the train is powered by electric motors. Electric motors are vastly superior to mechanical transmissions at delivering high torque at low RPM.
60. Clutchless transmissions are two fans in very thick liquid and it utterly amazes me that this is an effective method of torque delivery. Clutched transmissions use friction between two very smooth plates so tldr cars are weird.
61 cont. Engines shouldn't be in front of the passengers, but they have to be in order to weigh the front end down during startup. Engines don't crumple, so that makes head-on collisions less pleasant.
69. Condoms and other sex products have intensive materials standards and manufacture/testing procedures, *obviously*. It sucks that the end result is considered taboo, because they take an impressive amount of work to create.
70. If you heat a metal ring, the inner radius expands too. This is one way to fasten rings to shafts without bolts: heat the ring, slip it over the shaft, then let it cool and it will shrink and lock in place.
71. Mechanical linkages can be designed to turn a constant rotation into either straight linear motion, or constant linear speed, or trace complex polynomials, and we've been doing that for three or four hundred years.
74. Multiple thinner cables twisted around themselves are significantly better than a single straight cable, whether we're talking about tensile strength in steel or signal conductivity in copper. Fun coincidence.
76. Clay embedded with ferromagnetic particles make better magnets than straight up metal blocks, because they're easier to shape and the domains are easier to align. Metal crystals have a lot of internal cancellation.
77. Tape measures are built to the optimal performance characteristics to be used as radio antennae and this is a real thing that satellites do. They're self-straightening, easily stored, and machined to high uniformity.
82. If you think time zones on the planet's surface are bad, you should see time zones distributed across a processor, since these things operate so quickly that the speed of clock-tick propagation is slow enough to seriously matter.
83. GPS mathematics is one of the few intersections of general AND special relativity, 4-D hyperbolic geometry, orbital mechanics, and time dilation. Speed-of-light lag is in there too but everyone deals with that anymore.
85. The grid system, while appealing, is hilariously bad at actual traffic routing which is one reason it never appears in systems which have self-optimized for traffic delivery, like your bloodstream and nervous system.
86. Metal structures in environments with acid rain or seawater exposure will have a sacrificial metal of some other metal, often bronze, painted over them to take the induced electrical damage without corroding the actual structure.
90. Surface mining basically scrapes the entire dirt and rock off the top of a mountain, sets it to the side, pulls out the ore, and pushes it all back. A lot more energy used, but safer and more thorough than bore mining.
95. This isn't engineering, but I think it's cool. There's a small window when throwing a ball where if you let go, it will go where you want. This window is far smaller than the time it takes to process and issue the "open fingers" command.
95 (cont) If we scale this up, it's like standing on the roof of a ten-story building, listening to a song playing on the ground below, then plugging your ears and going from memory to toss a drumstick off the roof and have it hit the drum kit below on the right beat.
96. Electricity is delivered in tri-phase because it converts to single-wave or DC more smoothly and with less voltage drop than pure single-wave does, and a short between two wires is slightly less awful than a short in single-wave.
97. An arc between all three lines of high-phase tri-voltage creates a UV arc of sufficient intensity to cause sunburns and blindness in onlookers. Great YouTube clips though, as long as you get the ones where nobody dies.
98. Safety glass is manufactured under internal tension so that if it starts to crack, it rips itself apart into tiny little pieces rather than allowing natural fault propagation that results in horrific shards.
99. The gold leaf commonly used to decorate churches is micrometers thick. Gold's ductility is such that it can be formed into very thin foil or wire without breaking, without significant infrastructure.