I waited for something, and something died
So I waited for nothing, and nothing arrived
OOOOOOOOOOOOOOOOHHHHHH
Still kicking.
Internet, you have no idea how much has been going on over the last few months. I can’t even remember most of it myself. Did any of it even happen? Are you still out there? Am I still here?
So! So so so. Why are we here? What are we doing?
Well, I might need a while to recalibrate. In the meantime, here’s a fun fact: nobody really knows why planes fly.
No joke! There are these things called the Navier-Stokes equations which explain viscous flow – specifically, how air flows around a wing (plus the rest of the aircraft). Thing is, they’re really, really difficult to solve – hell, they might not even have a general solution. Apparently you can simplify them down based on a series of assumptions and spam numbers at them until they spit out something sensible, but… well, there’s a $1 million bounty on figuring them out for good, and nobody’s spilled the beans just yet.
So in the meantime we’ve come up with (or fallen back on) a series of less accurate but easier to work with formulae which are good enough. As the boundaries of human ignorance are inexorably rolled back, these formulae will likely shift and change and improve.
Still, kind of scary, huh? The physics that govern flight are still an unknown, so we’re running on a complex structure of deductions based on supposedly empirical data which itself is based on a series of assumptions we may never be able to prove.
Those of you who know me in meatspace might sense a tangent developing. And your senses would be right.
Just what can we know, anyway?
I mean, we fly on the assumption that the laws of physics as we know them will hold well enough to see us through. We haven’t been presented with any evidence that the relevant laws of physics would flaunt our understanding in such a dramatic way that aircraft will stop flying and fall out of the sky. But as Asimov’s Multivac stated in The Last Question:
“INSUFFICIENT DATA FOR MEANINGFUL ANSWER.”
By the way, if you haven’t read The Last Question: for the love of God, open a new tab and read the thing start to finish. It won’t take long, and your mind will be blown like the guy from Scanners. Unless you have no imagination, or have heard or conceived of something similar before… or if I haven’t taken sufficient account of the massive diversity of human perception and it just doesn’t really do anything for you. I know people for whom the Beatles do nothing, which I can’t for the life of me understand… I can only respect their abilities for form valid value judgements in a state of dazed befuddlement.
Point is this: we base our entire perspective on the assumption that our senses and cognitive abilities will provide an accurate picture of reality – something we know can be wrong. Magic tricks rely on simple but finely-controlled distraction and slight of hand, and yet are quite capable of duping us all. How do you know you’re not dreaming that you’re reading this text, and you won’t wake up as an unusually-intelligent butterfly with a major identity crisis?
Descartes pointed out that if I think, then I am… but note that only applies to the first person. I only know that I am alive, and nothing more. This makes solipsism a tempting refuge… but I refuse on principle to go along with that, because it just seems ridiculous. Perhaps I am the ridiculous. Perhaps time will prove me right. Or wrong. Who knows? I certainly don’t.
We’ve established that we can’t really know much of anything (this may itself be wrong)… so what now?
We assume, that’s what. Sure, it makes an ass of you and me, but damn it, it’s the only thing we can do to progress.
We start with something simple.
You see an apple falling from a tree. Do all the apples fall in the same direction and with the same acceleration? If you picked up an apple in one hand and a bucket in the other, would they both fall at the same speed if you dropped them? Are the answers to these questions reliably identical?
Now take one of the apples and throw it, making sure to record its trajectory. What is the shape of its flight? Does it fall down again? How much distance does it cover during its journey? How long does it stay aloft?
Repeat the apple throwing multiple times, then try throwing it at different angles. How do the answers to the initial questions change? Now repeat the experiment with a bunch of different objects.
You’ve started to lay the framework for a basic understanding of Newtonian physics applied to solid objects. Next, we’ll try fluid dynamics.
Run a bath. Get into the bath. Does the water level change, and by how much? Now get out of the bath. Does the water level return to its original state? Run your hand through the water with your palm facing the direction of movement. What did you feel? What is the surface of the water doing? Now repeat, but this time with your palm facing perpendicular to the direction of travel. Was that easier, or harder? Has the water behaved any differently?
Now pop the kettle on and brew yourself a mug of boiling water. It’s hot, isn’t it? Now throw it into the bath. Is the bath boiling hot?
Now pick up a piece of paper by two corners and blow over the top. Does it rise?
It all comes down to testing stuff over and over again until you think you’ve got a working model. You acknowledge that someone might come along with a more convincing explanation… but then again, they may not. Now ask yourself: can I use this model I have created to solve a problem or just make something exciting?
And I guess that’s engineering in a nutshell: taking an idea about how the universe works and applying it to solve problems, and learning and improving it if it doesn’t behave according to expectations.
OK, bizarre philosophical rant over. Normal service to resume… well, probably much less than 6 months from now. But who knows?
Basic Model Aircraft Design 