Nah, I want to talk about boomerangs. Maybe I’ll talk about how lasers work and why and all that in a different post.
Boomerangs though, they’re cool. You hold one in your hand in whatever way feels right, you throw it as hard as you can, and watch it as it flops awkwardly through the air and thuds into the ground and breaks in half. Throwing a boomerang is actually kind of hard if you don’t know what you’re doing. Making one can be pretty hard too. Luckily for you, I’ve done both, and here I am to talk about it.
First off, I’m going to give you a tiny non-expert’s crash course in aerodynamics because everything is better if you understand the basics. In case you didn’t know, boomerangs are all about aerodynamics. The main thing you need to know about aerodynamics is that faster air flow equals less air pressure (Bernoulli’s principle). That’s about it, really. That’s how a wing works, how a propeller works (which is really just a wing), how a boomerang works (which is really just a wing), why a ball curves through the air when it’s thrown with a spin, and why a ping pong ball will float in place if it’s put in a vertical air stream.
Science museums and exhibits (and I’ve actually even seen it at a fair before) will sometimes have a thing set up where an air hose is pointed straight up and a ping pong ball or beach ball or any lightweight ball basically levitates on top. It’s a bit counterintuitive to think about, a stream of air holding something in place rather than just pushing it away, but it makes sense if you know what’s really happening. First of all, the air is pushing the ball up and thus counteracting gravity, but then why does the ball stay in the stream and not just fall out of it? Because faster air means less air pressure, and the air outside of the stream isn’t moving as fast. Every time the ball moves to a side, the pressure from the still air that’s outside the stream is slightly higher than the fast-moving air inside the stream, and it pushes the ball back into the stream.
A curveball curves because a spinning ball catches the air around it (a boundary layer) and causes it to spin around the ball as well. If you were to throw a perfectly smooth ball with a spin, it wouldn’t curve. Because the ball is also moving through the air, the air on one side of the spinning ball moves faster than on the other side, creating a difference in pressure that pushes the ball.
This effect won’t happen to a ball spinning around the axis its direction is in. That instead (due to gyroscopic forces) will actually stabilize the ball’s flight and cause to curve less. That effect is exploited for bullets, and it’s why rifling on a gun is effective.
Moving on, a typical wing is shaped in a way that the air below the wing has a straight path, but the air that passes above the wing has a longer path.
Because a wing moves through (relatively) still air without pushing it forward, the air the passes above and the air that passes below take the same amount of time to cross the wing. They take the same amount of time to go different distances, so their speed is different (the air on top has to travel faster), and so they create a pressure difference, which is called lift. The more pronounced the curve on top of a wing and thus the longer the distance air has to travel, the more lift is created. Until you do too much and just kind of bulldoze the air. Bulldozers don’t fly, believe it or not. Unless you make one out of styrofoam and gave it really good wings, then maybe. I don’t know.
Propellers are wings stuck together that spin to create lift (referred to as thrust).
Boomerangs are also pretty much just wings, just weirdly shaped ones. There are a couple different types of boomerangs, depending on their purpose, separated broadly into returning boomerangs and non-returning boomerangs.
Non-returning boomerangs were most likely the original type of boomerang, and are essentially just well-tuned throwing sticks used for hunting. They’re shaped such that they fly as straight as possible for as long as possible. They can fly hundreds of feet and weigh up to four or five pounds, more than enough to break an animal’s leg or neck on impact. They’ve been used for tens of thousands of years and across multiple continents, although they are still used by aboriginal groups in Australia.
Returning boomerangs aren’t really as practical for hunting, though it’s been proposed that they were used to scare birds towards the hunter who threw it, but no evidence has been found to corroborate that theory. Returning boomerangs were probably discovered by tinkering with non-returning ones (flattened throwing sticks) and realizing that they could made to curve in flight.
Back to how one works, a returning boomerang (henceforth referred to as just a boomerang again) consists of two (or more) wings connected at an angle. The way it works is, as the boomerang spins through the air, it creates lift in the direction perpendicular to its spin. That’s why if you were to throw a boomerang oriented horizontally, it would curve up, and when you throw it near vertical, it curves around and comes back to you.
Now how to throw a boomerang. First of all, as the last paragraph states, don’t hold the boomerang horizontally. It doesn’t work. What you should do is grip it loosely in your hand, hold above and behind your head, the boomerang oriented almost but not quite vertically, and throw in a smooth motion without bending your elbow, releasing just above the horizon. It’ll feel like you’re throwing it into the ground (and chances are you will), but when you get the hang of it, the boomerang should fly back to you. If it doesn’t, and you made the boomerang yourself, eh, you might have made it wrong.
If you want to make one yourself and don’t know how, then look up a tutorial (it’s actually pretty easy). I’ve written enough on this for now. Bye.