Category / Explanations

Where the magic happens

by ams9006

The Science Behind Paper Airplanes

Have you ever thrown a paper airplane? How did it fly? Paper airplanes vary widely in design, and those differences lead to meaningful differences in the way that they fly. Some airplanes fly quickly through the air, while others glide slowly. Sometimes, a paper airplane will tip its nose upward, leading to a stall. Why do these things happen?

The mechanics of paper airplanes are interesting because they are similar to those of most things that move quickly through the air. They have four basic forces acting on them:

via auntannie.com

The thrust comes from you when you throw the plane. Thus, the plane has no thrust in flight. The reason it doesn’t continue to slow down during flight is because it is also falling, “converting” its potential energy into thrust as it falls.

The lift comes from the difference in air pressure above and below the wing. This is caused by the shape of the wing, known as an airfoil. Lift is proportional to the size of the wing and the square of the speed of the plane.

So how do these forces affect how a plane flies? Take for example the standard paper “dart” plane:

via Wikigami

If you have flown this plane before, you know that it flies quickly, but drops to the ground relatively quickly. This can be explained as the plane having little drag, but little lift as well. More specifically, the lift and gravity forces are not perfectly aligned like they are in the first image. Rather, the center of gravity is slightly ahead of the center of lift in this plane, causing it to tip downwards and fly towards the ground.

Another popular plane is this “glider”:

via Instructables

This plane has a slow and steady flight if thrown gently or even dropped from a high place. Even without thrust from the person who throws it, it is able to maintain steady flight, if at the cost of a slight drop at the beginning. This indicates that its gravity and lift forces are aligned correctly. While it does not fly as fast, it has a larger wing surface area, which allows it to get enough lift at lower speeds.

With these ideas in mind, it’s easy to pick the correct airplane for any task. (That’s a common issue people have… right?) I once participated in a paper airplane competition based on longest total flight time. Knowing this, I instantly started folding large-winged gliders. When my plane nosedived too often, I folded it to place less paper in the front half, which moved the center of mass further back to compensate for the nosediving, which led to a steady-flying glider.

I went on to win $20 in that small competition. While, in real life, paper airplanes competitions are few and far between, this knowledge is not useful exclusively in these rare situations. Just to understand the basic mechanics at work in the planes, drones, and squirrel suits of the world is enlightening.

by ams9006

What Is Noise Cancelling?

If you look on amazon right now under the headphones/audio department, you’ll see headphones advertised as noise reducing, noise blocking, noise cancelling, or sound isolating. Upon first glance, they may all appear to be the same. Either that, or they’re all different and shopping for headphones just got a lot more difficult. However, there’s only one term that is worth the hype.

Noise cancelling is the only term from the many listed above that actually means something. All of the other terms simply refer to headphones that passively obstruct your ears from noise, such as with foam padding and a good shape to fit the side of your head. Noise cancelling is more than that.

Technically known as Active Noise Control (ANC), noise cancelling is simply intentional destructive interference of sound waves. Sound waves are all around us, and the microphones built into noise cancelling headphones can detect these sound waves accurately in real time. Then, the noise cancelling headphones actually play a sound to your ear that is the exact same as the noise incoming from the outside.

This seems counter-intuitive at first. How can noise be reduced by playing more of the same noise? Well, this is where the destructive interference comes in.

As seen below, the waves are either in line with each other and amplify each other or out of line with each other and cancel each other out in destructive interference. This is what happens with sound waves when noise cancelling headphones play replay exterior noise; the sound waves are precisely aligned through calculations involving the frequency of the sound and the speed of sound such that the exterior sound and the replayed sound cancel.

Image interference

Wave interference taken from UCSD

All of these calculations are done in real time by headphones when noise cancelling is activated, which is pretty incredible. However, noise cancelling has more applications than just headphones. If instead of isolating a single person from all noise someone wanted to muffle a single noise from all people, this same technique can be applied to loudspeakers strategically placed in a room/area with an unwanted noise. For example, if a private conversation were happening in a room, active noise control could be used to hide the conversation from eavesdroppers by creating what the IEEE calls a “quiet zone” within a certain radius. This could also muffle the sound of loud interior HVAC systems or the background noise in plane cabins.

This application of active noise control, called 3-D ANC, has its limitations. With multiple speakers needed to project sound in all directions/areas, these multiple sound sources could create unpredictable or unwanted areas of constructive, rather than destructive interference. Thus, a true “quiet zone” that covers the intended area is very difficult to achieve. However, it still has its useful applications in reducing noise pollution and increasing privacy, as well as possible less useful theoretical applications where I could go around and delete other people’s conversations from existence. That’s not science fiction; it’s science.

by ams9006

Why Are Instruments So Expensive?

Are you ever surprised by how vast the difference is between a rare artifact’s mundane appearance and its contrasting exorbitant price? These luxury objects are usually exclusive and handmade using rare materials, perhaps in limited quantities. Usually, these items are relatively useless and mostly for show, but occasionally these extremely high-end products are the necessary tools of a trade. For example, professional photographers use cameras worth thousands of dollars as well as many lenses worth thousands more in order to do what they do. Professional bike racers spend thousands of dollars on a competitive bike. Professional politicians spend significant chunks of their savings on their campaigns. In the same way, cellists end up spending more than they’d prefer to on their instruments.

This is the situation that cellists like me find themselves in. I don’t regret choosing the cello, but it definitely is the most expensive hobby I have ever been involved in. That is understandable, I hope, since many instruments are expensive and instruments are usually not impulse buys. However, cellos are among the most expensive of all orchestral instruments.

Go ahead and take a guess and write down how much you think a student cello or professional-grade cello should cost. Write those values down, and I’ll let you know whether you were right at the end of this post. In the meantime, let me explain the remarkable construction of a cello that leads to its unique sound and price.

Cellos are handmade, and they take several months to make. This in itself speaks volumes about how much manpower it takes for a cello to exist. However, the labor is only one part of the cost. Cellos have some pretty special parts made of relatively rare materials. The pegs, nut, fingerboard, and tailpiece are all made of ebony, an incredibly hard and dense wood that is also quite rare. The main body of the cello is made of mostly maple, but with a pine front, all hand-carved and/or bent.

parts of a cello from wikipedia

The strings of a cello are made of similarly unique materials. In the baroque era of music, most cello strings were made of dried sheep/goat intestines. Today, they are usually made with a core of steel or synthetic materials. However, wound around this core is a coil of tungsten, steel, aluminum, or silver, which itself can be plated with chrome or gold to gain the desired sonic effect. These rarer metals predictably make a set of strings cost up to hundreds of dollars, which I am reminded of often as strings have to be replaced approximately every year under regular use, and far more often for professionals.

But wait, there’s more! The cello is a bowed instrument, and the bow itself has many unique parts. The main body of the bow, the stick, is made of pernambuco wood, also known as brazilwood. Unfortunately, the pernambuco tree is officially an endangered species with its international export now illegal, so bow makers are now sometimes adopting alternative materials such as carbon fiber. The hair of a bow is bleached horsehair from the horse’s tail, and the grip is made of leather or snakeskin. The frog can be made of ivory or ebony with a mother-of-pearl inlaid within. The tip of the bow (not seen) is also traditionally made of ivory.

Parts of a bow from Sessionville

To protect these valuable instruments, musicians need a protective case. However, the cello is rather unwieldy, necessitating not simply a strong case, but also a lightweight one such that a person could carry it to and from gigs, rehearsals, and performances. Most cello cases are made of fiberglass and/or carbon fiber. This also contributes to the cost of owning a cello.

Now, for the moment of truth. Due to the above factors, a student-quality cello would cost from $3,000 to $10,000, and a professional-quality cello would cost from $10,000 to the hundreds of thousands of dollars. How does this compare to your initial impression?

What’s the point of paying so much money for a cello? Is there any alternative? Well, the the point of paying all this money is that there are some things you simply need as a professional musician. There really aren’t many alternatives today, since the art of instrument making is so detailed and traditional that modern technology is hard to apply to the process.

The point of this article is not to scare you from learning a new instrument or to complain, but rather so that you are more aware of something that I feel needs more attention. From now on, you will not be like my roommate’s classmate, who estimated Yo Yo Ma’s cello to be worth “about two hundred dollars.”

Edit: I found a website that completed an entire
study on the costs associated with owning a string
instrument, check it out!
by ams9006

eSports Are Not Sports… Or Are They?

According to Google, the definition of sport is “an activity involving physical exertion and skill in which an individual or team competes against another or others for entertainment.” This definition makes sense; every sport requires athletes that train to be the best and compete in front of an audience. According to this definition, competitive video games are not sports, because there is no physical exertion. However, it’s not that straightforward.

First, some background. Competitive video games are known today as esports. Professional esports “athletes” compete in one of several games full-time to entertain viewers and win prize money in tournaments. Esports are an industry growing so quickly that its expected by Forbes to be worth over $1 billion by the end of 2018. This year, the League of Legends North American Championship had of 76 million viewers, which is 72% as many viewers as the 2018 Super Bowl, and that is only one of many tournaments in one of many games.

Esports are significant and cannot be ignored; however, are they sports? The main argument against this definition of esports as sports is that there is little physical exertion. While this may be true, many other activities that are popularly considered sports lack physical exertion as well, such as target shooting, motor sports, and fishing. These sports are defined less by heavy physical exertion and more by precision, coordination, and experience. These three skills required of athletes in these (admittedly minor) sports are all skills required in esports.

Does this mean that esports are just as much a sport as target shooting, motor sports, and fishing? I believe that technically, it does. Of course, culturally, it is not accepted as a sport, so I wouldn’t go around referring to it as a sport since it’s not popularly accepted as one. However, I believe it has enough similarity to a sport that it deserves the same recognition as as a sport.

Esports cannot be dismissed due to its economic size, as I noted earlier that the esports industry is skyrocketing. However, esports players cannot be dismissed as athletes either. Their physical precision, team coordination, and work ethic require more hours of work than I can imagine. An ESPN article reports that common practice hours include 12 hours a day, 7 days a week of scrimmages, strategy analysis, and drills. Like most competitive scenes, esports has incredibly fierce levels of competition that require relentless work.

This relentless work found in sports leads to a tragic end: early retirement. Like in many sports, esports players experience mental burnout, physical injury, and displacement by up-and-coming younger players that force them to retire early, usually as young as in their early twenties. Like retired athletes in other sports, esports players often settle down after their tumultuous careers and finally go to college and get a more standard job.

Esports are like any other sport. They have a gigantic and growing market and viciously competitive players. They have dedicated fan bases, an international audience, inspiring underdog victories, and tragic downfalls. However, society often relegates esports to the role of youthful fad. I cannot deny them by claiming that esports are sports by definition, but I can say that esports are real and they cannot be ignored for much longer.

by ams9006

What Goes Up Must Come Down

What goes up must come down, except for spacecraft. Some tend to keep going up, or at least stay up for a long time. However, all of the spacecraft, satellites, and junk in earth orbit still comes down. In fact, they have, are, and will always be on their way down. Everything in orbit is falling, because everything in orbit feels the gravitational pull of earth.

Based on our cultural knowledge we accumulate from media here on earth, it appears as if there is no gravity in orbit. The incredible pictures and videos we are given by NASA and other space travel organizations paint a picture the of harsh, yet serene silence and stillness of space, where everything is so isolated and untouchable that not even gravity can displace it. However, despite the fact that everything in space appears to hover and not fall to gravity, that is not the case. Everything in orbit is under the influence of gravity, and it’s all falling.

Why is reality different from perception? Wikipedia put it best: “objects in orbit are in a continuous state of free fall, resulting in an apparent state of weightlessness.” Everything in the International Space Station is falling just as quickly as the International Space Station itself is falling. Just as you feel weightlessness in a falling roller coaster, so do astronauts and cosmonauts in the falling space station.

So why has the space station been falling from an altitude of 250 miles for 20 years and never hit the ground?

Because it’s going insanely, ridiculously, crazy fast. Specifically, the space station is floating along at about 7.67 kilometers per second, or 17,200 miles per hour. This is over 22 times the speed of sound and fast enough to orbit the earth every hour and a half. This means that falling, in the traditional and logical sense, does not apply here.

https://youtu.be/Xjs6fnpPWy4?t=1m25s

a real-time video demonstrating the International Space
Station's one and a half hour orbit period

To illustrate this, compare the International Space Station to a ball tied to a string.

a rather colorful, round space station (source)

When the ball is spinning around, there is a constant pulling force toward the center of the circular path. However, because the ball is constantly moving forward, the force only shifts the direction in which the ball is travelling. The physics students among you would recognize this as centripetal acceleration; those of you who haven’t taken physics would recognize this as really boring.

What’s not boring is that the International Space Station undergoes the exact same process on an almost unimaginably ginormous scale. It experiences 90% as much of the pull of gravity as we feel down on the surface of earth, but it is just going so fast that gravity does not pull it down to the ground, but just around, leading to a circular path around the planet that we simply call orbit.

by ams9006

Why Is My Computer Slow?

If you’re like me, you spend a lot of time on the computer. You have years upon years of experience using computers, and you’re approaching light speed at completing digital tasks. However, your computer is not. Every time you start it up, your computer does its best attempt to mock and imitate the way you wake up on a Saturday morning, taking far too long and trying to convince you to just let it go back to sleep. However, computers aren’t people; they don’t get tired (unless they run out of battery). Why are computers so slow?

It may appear at the surface that a computer is simply slow because the processor is outdated and the computer needs to be replaced. However, there are several ways in which a computer can be lacking the resources it needs to perform. One of the most common reasons that a computer is slow is not because the processor (often described as the “brain”) is slow, but rather because the storage device is slow.

Storage devices for personal computers come in many shapes and sizes. In the ancient past (read: a few years ago), data was stored on floppy discs. These were large, had capacities measured in kilobytes or megabytes, and most importantly, had bandwidths of about 1 Mb/s. Until recently, most storage was on hard drives (or hard disc drives, or HDDs), which were 100 times faster than floppy discs and had 10,000 more storage capacity. Keep in mind that the time span between these technologies was only a decade or two; technology improves significantly every year.

Today, most devices run on solid state drives (SSDs). These run on a fundamentally different type of technology. While CDs, DVDs, floppy discs, and hard drives all operated by writing and reading from spinning discs, solid state drives read and write from transistors. Thus, they are solid state because there are no moving parts, which makes them far, far more durable than previous mechanical forms of storage. However, that is not the main reason why they are used today.

We use them because they are crazy fast. Obscenely fast, even. They’re fast enough to transcribe the entirety of the English language Wikipedia in under a minute. They are obviously more expensive than hard drives, but computer manufacturers have learned that this is the feature that makes their computers feel fast.

This video demonstrates the real-world impact of an SSD

There still are applications which require large amounts of processing power; professions in the sciences and digital arts require professional (expensive) computers to do the job. However, most users don’t synthesize new data and content on their computers; they are simply looking to retrieve data that already exists on their computer or on the internet. They turn on their computer, check their email, watch videos, move documents, search the internet, and turn off their computer. All the computer is doing is shuffling things around, whether from the internet to the computer or from the storage drive to the user’s eyeballs.

That is why having a fast storage drive is important. If your computer is slow, it’s probably because your computer uses a hard drive. Fortunately, upgrading a hard drive to a solid state drive is as simple as backing up your data, unplugging one small metal rectangle, plugging in the new slightly smaller metal rectangle, and re-downloading the backup.* However, that’s a blog post for another day.

*it’s actually a bit more complicated than that
by ams9006

How 3D Printing Works: Explained in Under 500 Words

3D Printing is just like 2D printing on regular paper.

Why is that, you may ask; isn’t 3D printing by definition totally different, introducing a whole other (excuse me) dimension of technology and complexity? How are they comparable?

On a “normal” paper printer, a user first sends the file they want to have printed from the computer to the printer. This file is a two-dimensional image or document; on a 3D printer, the file is a three-dimensional model. However, the process is the same.

The printer (2D or 3D) does not know how to interpret an image, document, or 3D model because it is simply a connected collection of motors, nozzles, and buttons. It is the computer that interprets these files and translates them into specific instructions for the printer to follow. For example, the first commands given a paper printer would be to bring a sheet of paper down to the print area and to move the nozzle to the top left corner of the sheet.

When a paper printer receives these commands, it proceeds to move its ink nozzle around the surface of the paper, depositing ink in the predetermined pattern to form the image provided by the computer. In the same way, a 3D printer simply interprets the commands by moving its nozzle across the bed of the printer and depositing plastic in the predetermined pattern. (3D printers have to melt their plastic as they are placing it though.) However, unlike a paper printer, the 3D printer does not spit out the page after drawing the image on the bed of the printer. Instead, the plastic laid on the bed of the printer becomes the new “paper” or printing surface, and the printer continues to deposit another layer of plastic.

The many layers of plastic needed in a 3D model

The image formed by each layer of plastic can be thought of as a “slice” of the 3D model. All of these slices joined on top of each other forms the product, a functional plastic object.

Just like with 2D printers, 3D printers can print in different colors. However, not only can they print in different colors, they can print in different materials as well. Different plastics have different properties that are desirable for different applications. For example, if I wanted to print a tire for an RC car, I would use flexible filament for its rubbery texture that can grip many surfaces.

The way I see it, 3D printing can do everything that paper printers do and more. This comparison applies to the end use of the products as well. Printed paper is used to store, share, and display information and images. 3D objects do the same thing; there are 3D printed art pieces and educational models all over the internet. However, plastic isn’t just used to make art and information; it can be used for functional purposes as well. This is the magic of 3D printing: you can think of an object, search for it online to try and print it, not find it, make it yourself, and have it, all within an hour.

Edit: Due to unforeseen (see: predictable) circumstances, this explanation has surpassed 500 words. I apologize for any inconveniences caused.