 I promise we'll start recording in a little bit, I just have to figure out how to keep this light from rotating like this. I need a moment. Let's say that you're one of those people who's going a little crazy in quarantine and doing some home improvement, and as you're working outside you see a butterfly landentally on your roof. Knowing some basic physics, you know that every action has an equal and opposite reaction, which must mean that the shingle the butterfly has landed on is now exerting one butterfly's worth of force upward. But that shingle is now pushing down with an extra butterfly's worth of force, and has to be pushed upward by the plywood beneath it. That plywood is pushing down on a roof beam, which is pushing down on a framing beam, which is pushing down on a load bearing wall, which is pushing down on a floor joist, which is pushing down on a concrete slab, which is pushing down on the earth. The butterfly is ultimately being supported by the earth itself through a winding path of forces that starts under its feet and passes through every piece of the building in between it and the ground. This idea of how structures resist pushing and pulling, tracing the path of maximum stress through each element is called load path analysis, often used by architects and engineers to evaluate how structures will behave when forces are applied to them. It's a silly exercise when you're talking about a butterfly, but when you're considering hurricane force winds, or an Anvil dealership on the top floor of a building, it pays dividends to think of how exactly those forces will be resolved, how they'll make their way through the structure to be cancelled out by some equal and opposite force, hopefully. Load path analysis is also useful for designing things like watches, cars and TV remotes. Where the forces of springs, motors and button presses have to be cancelled out somewhere inside the device. For engineers, short and direct load paths are highly preferable to long winding ones, because all materials, even very strong materials, have some amount of give, some amount of elasticity or springiness. A load path that meanders a long way through a structure is going to result in more stretching when that load is applied, which is a bad thing if you're not looking for it. Imagine trying to lift a dumbbell versus a water balloon of the same weight. The balloon warps and deforms and sloshes around as you try to move it, making it much harder to manage. Some of your lifting energy is going into that extra motion, so you have to work harder to move it the same distance, and your muscles will wear out quicker. When you imagine that sort of sloshing in nominally rigid parts of an engine or a bridge, where you're wearing out supports or load bearing members instead of muscles, you can understand why shorter load paths are usually better. We've talked before about the engineering principle of failing gracefully, of anticipating how something might break and designing it to do so in the least catastrophic way possible. When a structure fails to withstand a load, it's because a member of the load path fails, bending, buckling, or breaking out of the way. Now unsupported, the load will find a different path through the structure. It's easy to see how this might cause a cascade of failures. If one leg of a chair buckles, it's not like the other three will happily support your weight. But exercising some foresight can allow a designer to create secondary load paths that, with a little luck, will still support a load if the primary load path fails. Many bridges are built, so if one support breaks, others are positioned in a way that will help distribute the load to the remaining structure. Load path analysis can also highlight places where structures aren't doing useful work, which helps designers find opportunities for saving weight or material. You may have seen structures like this one, with large circular cutouts in the reinforcement plates, sometimes called speed holes. They aren't just for looking cool, although they do look very cool. They significantly reduce the overall weight of the structure without sacrificing much strength. When you apply a force to the structure, the load path through the plate is high stress at the edges, but low stress here in the center. And so long as we stay well away from the load path as it traverses the plate, we can remove material without affecting how the force will be resolved. Load paths are such a useful conceptual tool that I find myself thinking in similar terms, even outside engineering. For example, planning for emergencies can be overwhelming, but thinking of how load paths will be redistributed in the event of a failure can help to process how things might go wrong and how to prevent them from spiraling out of control when they do. As a human, much like the butterfly has a load path that terminates in the ground, I have a load path that terminates in the sun's energy. I eat a burrito. The burrito comes from a food truck. The food truck owner gets burrito ingredients from a market, the market gets them from a supplier, the supplier gets them from a farm, and the farm grows them from the sun. Certain failures of that chain can be circumvented with a different load path. If the food truck is closed, I can cook my own burrito. But more serious failures will require that I find a different way to cancel out my energy load in the sun, maybe using canned goods, maybe growing my own vegetables. The shorter that load path, the fewer steps between me and the sun's energy, the less I'm subject to variance in the intermediate steps. If only I could figure out photosynthesis. If you're a programmer, you might be struggling a little with the term load path, which means something entirely different in software, but you may have recognized a possible analog in coding. The paradigm of flat code urges programmers to reduce or eliminate complexity that's created by deeply nested statements, making the program more readable and easier to follow. A critical operation buried in a five level deep set of if statements requires the reader to hold a number of different things in their heads to fully understand what's going on. While a flatter program puts that operation closer to the main flow of instructions, easier to debug, potentially faster and less likely to fail. When considering arguments for or against some idea, there's always a few big issues that stick out as being especially important, pressing items that really demand some sort of response. If someone claims to have a million dollar idea, they'll need to explain why they don't have a million dollars. If they claim to have solved ethics, they should probably address why philosophers haven't cracked it for 2,000 years. If the argument doesn't address these issues directly and succinctly in its main thrust, if it responds to them through meandering tangents loosely coupled with the main point, it feels finicky and unreliable, like the load path for weighty objections is wobbly and ungrounded. In a similar vein, good writing connects an audience to an idea in a straightforward way, not requiring them to follow any labyrinth and reasoning or leaving large gaps in the explanation that might invite confusion or counterpoints. So how did I do? Can you think of any other places where thinking in terms of load paths might be useful? Please, leave a comment below and let me know what you think. Thank you very much for watching. Don't forget to blah blah subscribe, blah share, and don't stop thunking.