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The Fulton Skyhook May 26, 2012

Posted by peterxu422 in Science, Superheroes.
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One of the best scenes in The Dark Knight was when Batman was in Hong Kong apprehending a crime boss. He asked his tech expert, Lucius Fox, how he would be able to get back into a plane without it landing. Fox suggested Skyhook, a technique used by the CIA for getting their agents out of hotspots.

The Fulton Skyhook, as it was called, was developed by a man named Robert Edison Fulton Jr. The system works by attaching a modified weather balloon to a 500 ft nylon cable and the other end to the person or cargo to be recovered. The nose of the pickup plane is modified to have a protruding 30 ft ‘V’ that would hook onto the nylon cable as the plane flew into it, dragging the cargo with it. The back of the plane opens up where crewmen would try to reel in the cargo and bring it safely into the aircraft. More detailed information could be read here.

The article mentions an interesting test that was performed, where they tested the system on a pig.

The pig survived the test, even after it began to spin out of control while it flew through the air at 125 mph. Once the pig had its feet on the ground and regained its orientation, it began to attack the crew.

The first actual human pickup didn’t take place until 1958 when Marine Staff Sergeant Levi W. Woods was successfully hoisted in during a test of the system. The process took only 6 minutes and Wood’s avoided the spinning the pig endured simply by extending his arms and legs.

I find it interesting to note how Woods avoided the violent spinning situation by simply extending his arms and legs. In doing this, Woods increased what’s known as his moment of inertia (I), the tendency to resist rotation. The greater your moment of inertia, the less you will rotate. The reason this is true is because of nature’s tendency to conserve Angular Momentum (L), the amount of rotational motion. If your angular velocity, how fast you’re spinning, is w, then angular momentum and moment of inertia are related by the formula L=I*w. If you have a large I, then you must have a smaller w (you spin more slowly) in order to keep L the same.

The way you can increase your moment of inertia is by increasing the radius of your rotation. In Wood’s case, he did this by extending his arms and legs. The situation is exactly the same as a figure skater going into a spin. They spin faster when they pull their arms in close to their body because they have reduced their moment of inertia. To compensate, their rotation rate must increase in order to conserve angular momentum.

Here is the scene with the Skyhook in The Dark Knight. The final installment, The Dark Knight Rises, comes out July 20.

VIDEO: The dark knight plane scene

Getting To Columbia April 23, 2012

Posted by peterxu422 in education, Science.
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I avoid talking about myself on this blog unless it pertains to a personal experience with the scientific topic of discussion. But in lieu of recent events, I wanted to make an exception. A few days ago, I heard back from Columbia University informing me that I was accepted to their 3-2 Engineering Program. It is a joint program with certain liberal arts colleges where potential students spend three years in their home institution earning a B.A. and two years at Columbia earning a B.S. in a particular field of engineering. Students have to meet the requirements for graduation, meet the engineering course requirements, complete a major, and maintain a 3.0 GPA during their time at their home institution.

I began to seriously consider a career in engineering during my final year of high school. It started with seeing the movie Iron Man in theaters. Seeing the power of the technology and the work Tony Stark put into building it captivated my imagination and piqued my curiosity. I tried to start thinking more like an engineer and put more effort into solving problems in my classes.

But when I came to Queens College, a liberal arts school, engineering was not available. I was ready to go into Computer Science instead. Not long after, a fellow classmate told me about an engineering program that was offered by the Physics Department. I rushed to find out more and learned that this was a joint 5-year program with Columbia University. After speaking to the liaison, I learned that most students who did this program were physics majors because a lot of the courses overlapped between the Physics Department and the engineering requirements. He laid out a preliminary schedule of courses that he recommended I should take within the next three years to complete the program. It was booked with a heavy set of physics and math courses.

Physics was actually one of my weaker subjects in high school. Including the regents, I mostly scored in the low 80s. I did not think I would do well in the major unless I became interested in the subject itself. So that’s what I did. I read up on many articles and watched documentaries every week on the field to learn about the history of the subject as well as recent developments. I was fascinated and I loved it. It made taking the classes a lot easier and more pleasant. Rather than seeing my science courses as something I had to drag myself through, they became the fine tuners of the details of the bigger picture in which I saw science.

Though the 3-2 program guarantees admission to whoever meets all the requirements, it does not mean it’s a shoo-in program. To give this some perspective, the program has 150 seats available. According to QC’s liaison, the number of interested applicants from our school alone would fill all of those seats. But the actual number of students who get accepted from our school each year is on average five. From my perspective, doing well in the classes is not even the biggest challenge. The most difficult part is completing all of the necessary requirements within the allotted time. By the second semester, you would start to have on average 3-4 science and math classes per semester.

That can be something to fear or to look forward to depending on your mindset. If you are really genuinely interested in the field, what’s so terrible about learning more about the things you like? What I learned most from this program, aside from the wealth of technical knowledge, is that genuine interest and curiosity are much stronger mentalities and get you much further than rigid perseverance alone. You can keep telling yourself “just 3, 5, 10, or 20 more years of this and I’ll finally get what I’ve been waiting for.” If you’re only living for a reward, you don’t get to experience the path that gets you there, which can often be rewarding itself. Or worse, you set yourself up for greater disappointment should you fail in your endeavors. But if you can live with a curiosity and eagerness to learn about a particular field, I think you’ll be blessed with joy and satisfaction at any point in your life. Be a geek about something and good things will happen.

Engineering At The Nanoscale April 14, 2012

Posted by peterxu422 in Science, Technology.
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Devices keep getting smaller. Objects that once were only seen with the naked eye now can be looked at through a microscope. How do we keep putting more stuff in less space?

Building technology at the nanoscale, virtually at the atomic level, is the heart of our modern day technological revolution. It seems impossible that engineers can perform such a feat. How do they do it? It turns out some of the techniques used to fabricate at the nanoscale are not as Herculean as one might imagine.

Currently, I work in Dr. Vinod Menon’s Laboratory for Nano and Micro Photonics (LaNMP) at Queens College. The work I do there regularly involves creating structures with very fine thicknesses. For example, I often need to place a layer of material about 400 nm thick on top of a glass piece. The technique I use to accomplish this is called spin coating. There is a device called a spin coater which consists of a rotating platform. I place my glass slide on top of the platform, and use suction to keep it fixed on the mount. I take a liquid solution of my material and place a few drops on top of the glass. The spin coater allows me to adjust the spin speed and spin time. When I let it run, the platform begins to spin rapidly. Because of the centrifugal force caused by the rotation, a lot of the solution flings off the glass slide leaving only a very thin but even layer of material on top of my glass slide that is only nanometers thick. The faster it spins, the thinner it gets. The longer it spins, the thinner it gets.

This week, I went to City College to use one of their devices that allowed me to deposit thin layers of gold on top of a piece of Silicon. The device had an airtight chamber where I placed my samples inside as well as the gold I would be depositing. The gold was held between two metallic fixtures that kept it in place, and the Silicon pieces were laid underneath. The air is sucked out of the chamber to remove any impurities in the process. Because the gold piece is held between two metallic fixtures, I can pass a current through it which would heat up the gold and cause it to vaporize. I raise the current to 50 Amps and the gold piece begins to glow hot. A detector inside displays a reading of how thick the gold layer is and I see that the reading is increasing.

Intel, the largest semiconductor chip making company in the world, also uses special techniques to create their ever increasingly powerful chips. They use a technique called photolithography to fabricate their chips. The way it works is they usually have a base material called a substrate. Then they put a layer of semiconducting material on top of the substrate. This material is sensitive to light, meaning when light is shined on it, it vaporizes. They then put on top of this layer a stencil, that outlines the pattern they want to draw on their chip. Once the stencil is in place, they use light, usually ultraviolet light, to blast away the exposed layers. The parts that are covered by the stencil are kept intact and thus they produce a desired pattern on their chip. They repeat this process with other material as well until they have their completed structure.

There are a number of other techniques that can be used to engineer at the nanoscale. The ones I have mentioned are those that I have been exposed to and had personal experience with. As you can see, building nanoscale structures does not have to involve a very intricate and complicated process. We can use accessible macroscopic techniques to achieve microscopic creations.

Revisiting the Periodic Table April 8, 2012

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This week on the PBS show NOVA, David Pogue, a New York Times tech columnist, hosted a two hour program titled “Hunting The Elements”. Being the funny goofy person that he is, he made the episode very entertaining filled with fascinating science explained. It is definitely worth a watch for those who have Periodic Table phobia, a term I coined describing those who fear or dislike looking at a periodic table because they do not know how to read one. This program would be great medicine for that.

In the episode, he talks about the reactivity of elements, their origins, their uses, and their properties. In one scene, he goes to an explosion range where he and the fellow scientists test out the explosion speeds of different types of explosive materials like gunpowder, nitrate gel, and C4. He explains that how fast a substance explodes depends on how far away oxygen atoms are from each other within the molecules. Things that burn require oxygen, and so if oxygen is closer to the exploding substance, the reaction can occur more quickly and thus the explosion will be faster. Gunpowder was the slowest one because it has oxygen atoms far away. This is why it’s used to fire projectiles because it has enough force to shoot a projectile out but not enough to destroy the barrel of the gun. C4 is the fastest because the molecules that make up C4 have the oxygen atoms packed closely together.

In another sequence, he visits a bell manufacturing company and makes a whole bronze bell with them. He explains that bronze is made from a combination of copper and tin. Copper is malleable. So if a bell was made of copper and it was struck, it would not create a very good sound since the denting would absorb some of the mechanical energy that would have caused the vibrations to create the sound. Adding tin to the mixture fills up some of the gaps between the copper atoms which would restrict their movement. You get a much sturdier material which is very good for making the resonating rings of bells. Pogue then took a sample of the bell’s material to a lab to see if they had a good mixture of tin and copper. At the lab, they used an electron microscope and magnified the sample to such incredible scales that they were looking at the actual atoms themselves. It showed a very ordered layer of dots where the brighter ones were tin atoms while the darker ones were copper.

Electron microscope image of diamond and silicon

The last sequence I’d like to mention was about shark repellent material. Apparently, the lonely bottom two layers of the Periodic Table, the rare earth metals, have some purpose. These elements are supposedly able to repel sharks. The man who demonstrated this made a large powerful magnet out of one type of rare earth element and when he brought it close to a shark, it immediately turned its head away. They do a few other experiments that clearly illustrate the sharks do not like this material. They suspect the reason for this is that the sharks feel an electric shock when in the presence of this material. When they placed the magnet and a shark fin into a beaker of water, and connected two electric wires from a Voltmeter to it, they showed that a current was flowing. The atoms flowing off the magnet would lose their electrons making them positively charged. These positive ions are then attracted to the shark fin and they flow along it. This stream of moving charges creates a current thus giving a small jolt to the shark. However, the problem I see is that this explanation assumes that the magnet is inside the water. But when they brought the magnet close to the shark form the outer wall of the pool, the shark showed the same reaction. There must be more to the story than the explanation of the electric current.

Finally, to further your experience with the periodic table, I recommend downloading the free iPad app inspired by this program called The Elements. Pogue helped design it himself. It has an interactive Periodic Table, a fun molecule building game, and the whole Hunting the Elements program on it. David Pogue will be replacing Neil deGrasse Tyson as host of NOVA Science Now for the time-being. Dr. Tyson is taking time to film a reboot series of “Cosmos” formerly hosted by Carl Sagan. Pogue is an excellent choice for a host. I had the privilege of meeting him once and he is a very kind and funny person.

VIDEO: Preview for Hunting the Elements

Warp Speed March 25, 2012

Posted by peterxu422 in astrophysics, cosmos, Science, Technology.
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Even if you are not a card-carrying sci-fi fan, you may have at some point encountered the term warp speed and perhaps even contemplated about its realities. While inter-galatctic travel and teleportation are still a far reach technologically, theoretically, that is within the known laws of physics, they are not in violation with our understanding of nature.

Warp speed, if you are not familiar, is traveling through space much faster than the speed of light. According to Einstein’s theory of Special Relativity, the fundamental speed limit in the universe is the speed of light, 300 million meters per second. Sounds fast right? But let’s put that number in perspective. If you were to travel at the speed of light from Earth to the center of the Milky Way, it would take you 25,000 years to get there. Forget about going to another galaxy within a reasonable time period. Also from relativity, due to a phenomenon known as length contraction, we know that objects get contracted as they get faster and faster. If an object travels at the speed of light, it will ultimately become contracted and squeezed into nothingness. Not very convenient for space travel either.

But if the speed of light is the ultimate speed limit, how do we get around this problem? The potential solution lies in Einstein’s theory of General Relativity, which tells us how space is curved and can be warped. The one thing that can move faster than light is how fast space itself stretches. We know this because during the Big Bang, space expanded faster than the speed of light. Thus, to travel between two distant points in space, we can manipulate space itself to get to our destination.

The way to do this would be to expand the space behind you and compress it in front of you. The expansion of the space behind you gives the appearance of a push while the compressing space in front of you is dragging you forward. But realize that this does not violate Einstein’s postulate that nothing can travel faster than the speed of light. You yourself are not moving, but space is and it can move as fast as it wants.

The best way to imagine this is by taking a balloon, where the surface of the balloon represents space. Suppose you draw two dots A and B. You are at A but B is located very far away. Now imagine taking a cut-out spaceship and taping it to a ribbon that can wrap around the balloon so that the ribbon is tied around the balloon, but not bound to it. If you squeeze the portion of the balloon in front of the spaceship, “space” is being compressed. But you’ll also notice that point A got farther away from the spaceship and point B got closer. From your perspective, the spaceship did not actually move, space did.

How then do we actually go about warping space? Well, it’s not easy, and certainly requires technology beyond anything humanity possesses currently. But in theory, a way to accomplish this is by using a HUGE amount of energy, specifically negative energy. Negative energy has an opposite effect on things. For example, if something were about to collapse in on itself, negative energy would hold it outward. If something falls down, negative energy would make it float up. A combination of negative and positive energy pushing and pulling on the space around the spacecraft would give the desired warping effect of space. So a spaceship with warp drive capabilities would have on it an engine that could create something like a bubble of this negative and positive energy enveloping the vessel.

Also, as you may have seen in sci-fi flicks that when spaceships go into warp drive, the light from point sources in space begin to stretch and get all line-y. The reason it is rendered this way is because as the spaceship moves faster, it is catching up in speed to these light beams and so the crew on-board sees how the light actually looks in its beam form. But remember, the ship itself isn’t moving faster, the space around it is.

VIDEO: World Science Festival Warp Drive, Lawrence Krauss

Star Trek 2009 Warp

The Need To Look Up March 17, 2012

Posted by peterxu422 in astronomy, astrophysics, cosmos, Science.
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Whenever I leave campus during the evening, I look up at the clear night sky. First, I look for the moon, if it is visible. I then look at stars that have not been drowned out by light pollution. Finally, I look for Jupiter and Venus, which have recently been particularly visible. There is something marvelous about being able to look at a planet with the naked eye that makes you feel a lot more connected with the cosmos, which is often perceived as distant and separate from humanity.

Questions that arise while stargazing include “Is there life out there?” and “When will humans live in space?” Scientists search for intelligent life based on a potential civilization’s energy consumption. They categorize them as Type I, Type II, and Type III civilizations.

Type I is planetary. They control the energy of a planet. They have the ability to tap the energies of tornadoes, volcanoes, and earthquakes as opposed to running away from them.
Type II is stellar. They control the energy of a star, much like the Federation of Planets from Star Trek.
Type III is galactic. They control the energy of billions of stars in their galaxies, like the Empire from Star Wars.

We are a Type 0 civilization. Humans gather their energy from dead plants (oil and coal). But we are seeing the birth pangs of a Type I civilization. For example, the European Union is the beginning of a Type I economy. English is a Type I language. The Internet is the beginning of a Type I communication system. Rock and Roll, Rap music, Gucci, Prada, Hollywood celebrities are signs of a Type I culture.

While the transition from Type 0 to Type I is perhaps the most glorious of transformations, it is also the most dangerous. Type 0 civilizations are rather primitive and vulnerable. They are subjected to nuclear warfare, germ warfare, terrorism, fatal asteroid collisions, and many other dangers to which they do not have the means to stop. It is not certain whether we will make it to Type I.

I see the issues that our civilization faces and I become more convinced of the necessity of space exploration and extending our means of survival beyond the Earth. A rising world population comes with tremendous demand. As resources grow scarce, violence and aggression will spread as people fight to survive. The Earth will be unable to sustain us indefinitely, and it will simply be too much to keep asking people to compromise the comforts of their lives. Space colonization is the optimal, inevitable, and necessary solution.

But at the current rate efforts in space exploration are being promoted, it is not likely the solution will be achieved in time to meet the problems we face. NASA receives only half a penny for every tax dollar. Their entire 50 year running budget is less than the $850 billion bank bailout. That funding has paid for space rovers, spaceships, the Hubble telescope, sending a man to the moon – all monumental achievements that have pushed our understanding of the universe and our technological capabilities to horizons beyond. Imagine what our world would be like if they had the other half of the penny. But more importantly, when making efforts to pioneer space exploration, you do not make advancements in one field, but across many other disciplines like electrical engineering, mechanical, robotics, materials science, biology. The space program is the tent pole to the entire scientific enterprise that can give manifold benefits in various ways.

How then do we make this happen? I think the first step is that more people should start looking up. Appreciate the heavens, the possibilities, and the necessity of expanding our understanding of the cosmos. And hopefully, this collective desire will trickle over to those who have the capacity to take action and the vision to partake in great opportunities. Maybe then, we will have the chance to reach Type I.

VIDEO: Neil Tyson at UB: What NASA Means to America’s Future

“Why is the Sky Blue?” March 10, 2012

Posted by peterxu422 in Science.
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Do you remember asking this question when you were younger? Did you get an answer? If not, why did you stop searching for it? I find this to be a wonderful question with a fascinating explanation.

I remember one of the possible explanations I heard when I was younger was that the blue in the sky is the reflection of the blue ocean. But if you think about it, this could not be farther from the truth. We know from experience, that water is transparent. Look at any ordinary Poland Spring bottle and you will see that this is true. So in fact, the blue in the sky is not a reflection of the blue ocean, it is actually the other way around! The blue in the ocean is the reflection of light from the blue sky.

The sky is blue due to a phenomenon known as Rayleigh Scattering. It works as follows. Light is a form of electromagnetic radiation, and all EM radiation is composed of something called an electric field. When you put matter into an electric field, the protons and electrons become partially separated. They form one side that is slightly more positive and another side that is slightly negative. Something with a positive and negative end is called a “dipole” (i.e. two poles). If you have an electric field that flips back and forth constantly, or “oscillates,” the dipole oscillates as well. When a dipole oscillates, it emits its own EM radiation.

Scattering is a phenomenon when radiation, or any type of particle, collides with another particle and causes it to deviate from its path (imagine billiard balls colliding). Rayleigh Scattering occurs only with very small particles, less than 0.1 micrometers. When light hits these tiny particles, it causes them to oscillate, and they emit their own radiation. With particles of this size, they prefer to scatter blue light. The Earth’s atmosphere is littered with these tiny dust and gas particles. So sunlight, which is primarily white light (white light is composed of all colors), hits the atmosphere, and the tiny particles knock out the blue portion of the white light into every single direction. Thus our sky becomes illuminated with the color blue.

So why then, are clouds white? Clouds consist of bigger particles, like water molecules, much larger than 0.1 microns. So when light scatters off them, they do not scatter blue, but white instead.

Finally, the last question to ask is, “Why is the sky red during sunset?” Red light has less energy than blue light. When the sun is setting, it is at a much lower angle with the horizon than it is during the daytime. During sunset then, the sunlight passes through a larger amount of atmosphere than it does early on in the day. As it passes through a thicker atmosphere, the light scatters off more particles and loses more energy. The resulting energy of the light is much lower and so it ends up in the red portion of the spectrum. This red light is also reflected off clouds which is why we also see red clouds during sunset. It is interesting to note that as there is more pollution in the atmosphere, the more the light will scatter and lose energy, and the redder and more beautiful your sunsets will be.

I was leaving campus one day during sunset and took a chance to observe the surroundings. As expected, the horizon was primarily a yellow-red. But I also noticed that when I looked straight above and a little farther away from the horizon, the sky was still blue. I wondered why this was the case. My explanation for this was that the tiny amount of light that was passing through the upper portions of the atmosphere was traveling through a thinner layer than the light in the lower portion. And so that light would retain more of its energy and scatter blue instead.

So the next time you want to impress your lover, take him/her to see a beautiful sunset. And if you really want to sweep him/her off their feet, tell them about Rayleigh Scattering and answer their childhood question of why the sky is blue.

VIDEO: Watch this exciting MIT Lecture by the great Walter Lewin as he explains and demonstrates why the sky is blue. He makes his own blue sky and sunset in the classroom! (Start at 34:00)

Good News: CUNY Nobel Science Challenge Winner March 4, 2012

Posted by peterxu422 in education, Science.

I have the great pleasure and honor of winning 2nd place in the CUNY Nobel Science Challenge in the Physics category. The goal of the challenge is to get CUNY students to contribute to science literacy in New York City and become aware of the important scientific discoveries that these Nobel Laureates are making. The 2011 Nobel Prize in Physics was awarded to Saul Perlmutter, Brian Schmidt, and Adam Reiss for discovering the accelerating expansion of the universe, a discovery that is literally of cosmic proportions.

The winning essays can be found here on this site: Winning Essays

There are categories in Chemistry, Physiology/Medicine, and Economics as well. In the previous year, I submitted an entry but was not received as a winner. I was somewhat saddened, but content that I tried anyway. I got to learn a little bit about the previous year’s Nobel Winner’s exciting work which was in graphene, a 2-dimensional sheet of carbon atoms. It was a rewarding learning opportunity. This year I was hesitant about submitting an essay, but I decided to go through with it anyway. The previous year’s experience intrigued me so much about the Nobel Prize and the science behind it that I approached this more as a learning experience than as a competition. Fortunately, I came upon one of those blessed moments where fun and interest met reward.

The Award Ceremony was equally exciting. It was held at CUNY’s Central Office on the far East side of Manhattan and 1st Ave. The building was beautiful. Food was great too. They presented the award to each of the winners individually and spent some time on each one reading their bios and talking about their essays. Winners received an award encased in a beautiful frame and a very generous gift prize. I won an iPad2! Other winners received Kindles and iMac computers, and the grand prize winner received an additional $3,000. It was also a wonderful networking opportunity, as many higher order faculty of the CUNY system were there. I spoke to other fellow CUNY students and someone in charge of the Postdoc program who gave interesting advice about career paths. I was also privileged to meet Chancellor Goldstein and Tracy Day, co-founder of the World Science Festival. She was kind enough to thank me for volunteering during the summer as well as provide me her contact information so that I may be in touch with her this summer as I do an internship in China.

This essay challenge was a very wonderful idea and I am grateful to all of those who were involved in making it happen. Their efforts to raise scientific literacy and interest are evidently quite successful. I encourage everyone to participate in this challenge, not for the sake of winning, but for the sake of being informed. Even though I was unsuccessful in my first attempt, winning it the second time was more special because it solidified my resolve to remain informed about the happenings within the Nobel community every year. Though it seems like the iPad is one of the most valuable things in the world today, it can never replace the rewards of enlightenment and experience.

Photos From the Ceremony

Analog & Digital Signals February 25, 2012

Posted by peterxu422 in Science, Technology.
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For as long as I can remember, I have heard the terms Analog and Digital signals. In this advanced digital era, the terms have become more ubiquitous than ever. Though I was familiar with their names, I have never quite understood what they actually were or their differences until recently.

An analog signal is a continuous signal that varies with time. Continuous simply means that it is not interrupted. For example, a traditional clock with hands is an analog source. The hands keep moving without interruption and so it shows you EVERY moment of time during the day. A digital signal on the other hand only shows you finite quantities that change with time. A digital clock is, obviously, a digital source. Most only display up to the minutes. As a result, the time does not change continuously, but in steps of minutes. A digital clock that changes from 10:00 to 10:01 only shows you a change in the minute. But what about the seconds in between, or the milliseconds in between, or the nanoseconds in between? An analog clock on the other hand, technically shows you all of these and more, even though our human eyes are unable to detect them.

Another example of an analog signal would be that produced by a microphone. When you speak, your vocal chords cause the surrounding air molecules to vibrate which produce sound. If you hold a microphone close to you and speak into it, the vibration of the air molecules causes a metallic coil inside the microphone to vibrate accordingly. When the coil vibrates, it creates an electrical current that resembles the sound. The current is a continuous varying signal and so it is an analog signal. In technical terms, the current becomes an analog of the sound. This current is then fed to an amplifier and reconverted back into vibration which produces a louder sound.

What has puzzled me most about analog and digital signals is how they can be converted back and forth. Digital signals as we all know are composed of units of information called bits, which are represented by 0′s and 1′s. How then, I wondered, could a simple set of 0′s and 1′s represent something as complicated as a sound signal?

The way it works is as follows. Most analog signals can be converted to electrical currents. These electrical currents change with time and their “strength,” or amplitude, constantly changes as well. If you divide up the signal into sections, at certain points, the current will have a certain amplitude. At one instant it might be 7 Amps, then later on the signal could decrease and become 2 Amps. These values can be represented as binary numbers (number consisting only of 0′s and 1′s). If you do this for many amplitudes, you can essentially represent the entire analog signal in binary. This is the conversion from analog to digital.

In the end, the digital signal needs to be converted back to analog to get the original signal back (remember the microphone?). So you may ask what’s the point of this anyway? Well, the benefit of digital is that it is very useful for transporting data. Analog signals are constantly changing and controlling their amplitudes is difficult. Also, transporting them over long distances makes it more susceptible to signal degradation and quality loss. But with digital, you only need to control two values, 0 and 1, which is basically a no pulse or pulse of current. Since it uses just these two values and nothing in between, it makes it less likely for the signal to degrade. If a pulse of current is sent (1) and during its transport it slightly decreases and becomes say 0.80, on the receiving end it gets rounded to the closest value and becomes a 1 again, thus preserving the signal. This is the reason why digital signals are of such clear and high quality.

Let There Be Light…and Data February 20, 2012

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In my Optoelectronics class this semester, we study how principles in optics are applied to modern day communications technology. My professor pointed out that within a few years there may be a huge market for LED lights. LEDs may be a crucial component in allowing devices to send data between each other within sight.

Most data in this day and age is sent digitally. Digital data is represented by a series of 0′s and 1′s, which can physically represent no current (0) or a pulse of current (1). This is a very good system because a very complicated signal can be represented by just 2 values. Manipulating the order in which they appear determines what kind of signal you send.

Similarly, light can also be used as a binary system. Instead of using a current, it uses on/off light to represent 0′s and 1′s. Therefore, if you have a receiver that can detect these pulses of light, you can send data digitally using light. Imagine embedding these light sending/detecting technologies in mobile devices. It would completely change the way we send information to each other. Instead of sending data through Wifi, it would be through Lifi – Light Fidelity.

Some drawbacks you may notice are for example, that there may be very annoying flickering from the LEDs of devices as they send digital data through Lifi. But light detectors can be sensitive enough to detect slight variations in the brightness of light emitters. As opposed to turning the light completely off to represent a 0, it would just make it slightly less bright than the brightness setting for a 1. These variations would be so small that our human eyes would not be able to perceive them. Instead, what you would probably see is the LED turn on for the duration of the time it is sending the data. Another problem is that you have to be able to physically see the other device or else there is no possible way to send data using light. This is true, but it also offers certain levels of security protection that wifi does not offer. For example, if a hacker wanted to steal the data you were sending through Lifi, he/she would have to physically intercept the light beam somehow. Finally, you may say that if you can only send data, like a text message, to another device within viewing distance, you may as well just walk up to the person and tell them. But of course, this data sending is not limited to text messages by any means. For instance, you can send documents, photos, videos, and essentially any type of data you would send to a computer.

The promise of Lifi and LED communications technology are very great and, in my opinion, incredibly exciting. Watch an incredible TED talk below on Lifi and an awesome demonstration.

Harald Haas: Wireless data from every light bulb

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