# Qwayway

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1. ## Video games are kinda physicsy

Computers are good at math, right? So it follows that video games should be able to do plenty of physics calculations while you run around shooting zombies and stuff, right? Well, the thing is, they have to do a lot of calculations - and they have to do them really, really fast. Take, for example, some game based on a large map, with somewhere around a hundred players, all trying to shoot each other to death. Handled naively, every time a player shoots, the game would have to continuously test if the bullet is intersecting any player on the whole map at any given point along its path. And even handling one single player isn't easy! It's gotta check if it hit the player's foot, leg, other leg, hip, abdomen, shoulder, arm, other shoulder, other arm, neck, head... And then it gets even more confusing when you suddenly have an impenetrable pan on your back blocking some bullets. Now, check for all of these intersections somewhere between twenty and a hundred and twenty times per second, for every single bullet, for every single player. Basically, it's kinda hard for even fast computers to keep up, while remaining accurate. But that's where humans and their fandangled logic comes in! Now, how could a bullet possibly hit someone, if it's practically in a different time zone from them? Short answer: it can't! (Unless you have teleporting bullets, in which case you should be selling the technology for billions, not shooting people with it). So, take this giant map, and split it up into anywhere from a few to a bunch (so specific, I know) of little bitty squares. Now, as players move around, you've gotta keep track of which square they're in, which takes a bit more work. But now, when you have a bullet (or a few thousand) flying through the air, there's no way it's going to hit someone that's not within either its own zone, or maybe one of the adjacent zones. Now you've gone from checking every player in the game, to between zero and a handful! Much easier! These same sorts of logical assumptions can be made for all sorts of locality-based applications, like virtual lighting (really, do you want to simulate a billion photons shooting around a room?), more advanced collision detection (we've done point-like bullets hitting round-ish parts of bodies, but what about really complex, non-convex things hitting each other?), as well as odd things like splitting up a group of points into non-spiky triangles (or tetrahedra). That actually has applications in fluid dynamics, modelling the density of stars in galaxies, and a bunch of other things way over my head.
2. ## Jacob's Ladders Are Cool

Electricity is cool. Electricity travelling through air is cooler. Well, it looks cooler at least. It's actually really hot. Jacob's Ladders are neat little devices that send a roughly-horizontal electrical arc travelling upward between two electrodes. Source: https://en.wikipedia.org/wiki/Spark_gap#Visual_entertainment This is a long exposure picture of a Jacob's Ladder - there's actually only one arc at any given time. The mechanism behind the ladder effect is actually pretty simple. When the arc initially forms, it heats the air up quite a bit, as is evident from the glow it produces. This hot air has more energy, so it expands, which decreases its density relative to the air around it. Since it's less dense, it experiences a buoyant force upward, and since the electrons can more freely travel through already-ionized air, the arc follows the hot air upwards. Once the arc reaches a length at which it can't keep the air hot enough to remain ionized, the arc breaks apart and the path of least resistance returns to being the very base of the ladder, so the process repeats.
3. ## Pendulums Are Weird

Pendulums seem fairly simple, right? You take some mass, you take some string, throw them in a gravitational field, and bam! It goes back an forth, back and forth, back and forth. Without any kinds of friction, this will continue forever! But, what if you take a pendulum, and then stick a pendulum on the end of that pendulum? Well basically, things get incredibly more complicated. For a single pendulum, especially one that has a small angle of oscillation, you can predict exactly where it will be in its cycle virtually infinitely far into the future. However for even a double pendulum, this becomes impossible, without calculating every single intermediate state of the pendulum. And the motion of multi-pendulum systems is incredibly complicated in and of itself - for an n-pendulum system, one must solve an n-dimensional system of equations do calculate the motion of each pendulum, involving the momenta, kinetic energy, and potential energy of each of the individual components of the system. Basically, multi-pendulums are hard. From https://en.wikipedia.org/wiki/Double_pendulum Another property of these systems is that they are so-called "chaotic," meaning that a small change in the initial conditions can lead to large changes in the end result of the system, especially as time goes on. For instance, say you have two double pendulums set up. You start them both at just about the same place, but offset the second one by a single degree from the first one. Initially they may follow very similar paths, but as time goes on, it will seem as if they could have started from completely different initial conditions. Chaos appears all over nature and mathematics.
4. ## Humans... How do they work?

Cheetahs. They're pretty fast, right? There's no way a human could ever catch one, right? Wrong. Humans are evidently not the fastest creatures to roam this planet, but we are pretty good at getting anywhere we want to be, no matter how long it takes us to get there. Many creatures rely on hind legs to thrust them forward - have you ever noticed how a cat's or a dog's back legs are practically springs? They push themselves forward, accelerating incredibly rapidly, but at the expense of quite a bit of energy - and all that muscle movement in the abdomen can make it difficult to breathe effectively in the midst of a sprint. Humans, though? We just fall over. Seriously. Try to start walking forward, but then don't put your foot down - actually, don't, I don't want to be liable for any injuries. But the thing is, humans walk by simply falling forward, and then relying on that forward momentum to help lift us back up again. Talk about efficiency! You might not be able to run a mile in a minute, but you could certainly walk several before you run out of breath. So, about that cheetah. How could you ever catch it, you might ask? Well that's simple! Just keep walking (or, in Dory's case, swimming)! Eventually, the cheetah will tire out, and be forced to rest. When you catch up to it, it won't be able to run any more! Now, this is all relatively related to something that's more of an engineering term - mechanical advantage. In the simplest of terms, you can use the same amount of energy to do two things: go really far, or go really fast. The more Physics-y relationship is Work = Force * Distance. For the same amount of work, you can either maintain a large force over a short distance, or maintain minimal force over a large distance. Humans have opted for the minimal force over a large distance - most of the work we do is actually just to keep us from falling to the ground. Gravity basically just uses our legs as a lever to do the rest.

6. ## Isaac Newton Appreciation post

Yeah, he was a pretty cool dude. Shame he couldn't be alive now, now that we have so much amazing technology to study the universe with. At least he left a huge mark on the world. Who knows where we'd be if Newton wasn't so curious. Probably not taking Physics C. :P