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The Physics of the New Year December 31, 2011

Posted by peterxu422 in Science.
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As December 31st comes to end, when the clock strikes midnight, the Gregorian calendar is reset to January 1st and another year begins. As you may have noticed, we do this every 365 days. Something must be repeating itself annually to represent the start of this new cycle. Obviously, it is a representation of the complete revolution of the Earth about the Sun.

It takes the Earth approximately 365 days to revolve around the sun. But where does this number come from? In math and physics, there is a way to mathematically represent periodic systems, i.e. systems that repeat in a regular pattern. In physics, if you have a system where an object goes around in a circle, that system has a certain period, because there’s a certain amount of time it takes the object to leave one position and return to the same position. The period is represented by T. The orbits of planets are such systems and so they have a period too. It turns out that the period of an orbiting object depends on the speed of its orbit.

To find the period of the Earth, you would have to apply Newton’s law of gravitation and his 2nd law of motion. Newton’s 2nd law simply says that the forces acting on an object are equal to the mass of the object times its acceleration, F = ma. His law of gravitation says that the gravitational force between two bodies depends on their masses (their size) and the distance between them.

According to his 2nd law, we must set the gravitational force equal to the mass of the planet times the centripetal acceleration, a = v^2/R. If we solve for v, we get the orbital speed, and since the period depends on the orbital speed, we can also find the period of the orbit. Plugging all the values in such as the gravitational constant G, the mass of the sun M, and the distance of the earth from the sun R, we can calculate the value of T which comes out to be 365.5 days.

Isn’t that just amazing? Isn’t it just so incredible that with a sheet of paper and a pencil, the laws of physics gives us insight into the motion of heavenly bodies and enable us to predict something as grand as the time it takes this planet to revolve around the sun? This is the power of math. This is the power of science. Happy New Year to you all.

Albert Einstein – His Work, His Contributions, His Legacy December 25, 2011

Posted by peterxu422 in Science.
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Albert Einstein is a household name, but few know of his work and his role in science.

When I was younger, my perception of Einstein was that he was a mad scientist who conducted all kinds of crazy experiments that led to his trademark frizzy hairstyle. But this could not be further from the truth. For Einstein was a theoretical physicist rather than an experimentalist. The only materials he required for his research were paper and pencil.

In his early years, Einstein worked in a patent office in Bern, Switzerland. Everyday, he would come into work, quickly analyze the patent applications on his desk, and proceed to secretly work on questions in theoretical physics of the day. It was here that he developed his famous theory of Special Relativity.

Relativity is one of the fields that gave rise to the Modern Physics revolution. Classical physics explains common human experiences such as falling objects, friction, electricity, and magnetism through Newton’s laws of motion and through the principles of Electromagnetism. Modern Physics explains events that are not common to our everyday experiences, such as objects traveling close to the speed of light and behaviors of atoms.

Special Relativity tells us that space and time are not static, but stretchy and dynamic. When Isaac Newton formulated his laws of motion, it was believed that time was constant throughout the universe, meaning the way one experiences time on Earth experiences it the same way on Mars. Time was seen as an arrow that when fired traveled in the same direction indefinitely. However, Einstein’s theory of Special Relativity told us otherwise. Time is not constant. People experience time differently. This was a completely non-intuitive way of understanding the universe and it shook the foundations of physics.

Special Relativity simply tells us that people in different reference frames experience things differently. Everything is relative, not absolute. Therefore, space and time are relative. The theory requires that nothing travel faster than the speed of light. But if you travel close to the speed of light, then very weird things begin to happen. Time slows down for you, and space compresses. These phenomenons are called Time Dilation and Length Contraction. Let’s suppose you stood on Earth, and I was in a space ship flying close to the speed of light past Earth. Suppose you were able to see exactly what I was doing in the space ship. If I were doing jumping jacks at a normal pace, you would actually see me doing it very very slowly. This is because time has slowed down for me in your reference frame. To myself, I would feel as if I were doing jumping jacks regularly. Not only would you see me doing jumping jacks slowly, you would notice that I am a lot thinner and contracted, like squeezing a picture together in Photoshop. This is a very bizarre and strange idea, but the mathematics indicates this.

You might say well that is nice that the math shows this, but it is all just a theory. But in fact, these effects have been experimentally verified. They tested time dilation by synchronizing two very precise atomic clocks so that they ticked in unison. One clock they left on the ground and the other they put on a PanAm aircraft. They flew this aircraft around the world in the direction of the Earth’s rotation to give it extra speed and when they brought back the clocks together, they measured the difference and the time difference was exactly the amount predicted by Einstein’s theory. Relativity has practical uses today too. You unknowingly experience these phenomenons when you use your smartphones or gps systems to navigate yourself through the world. GPS signals are provided by satellites orbiting the Earth. These satellites travel at very high speeds and as a result, they are affected by time dilation. To make sure they are synced properly, their clocks must be corrected to take these effects into account. Without Relativity, your GPS would be useless. Relativity is real.

Einstein’s contributions extend far beyond his theory of Special Relativity. His other work includes General Relativity, the Photoelectric Effect, theoretical foundations in lasers. One could write volumes about his work, and covering it all in one blog post would be too exhausting. This is but a taste of one of Einstein’s most important contributions to physics. With it, his legacy will continue to echo throughout generations to come.

VIDEO: Einstein’s Relativity – Time Dilation

The New American Dream December 11, 2011

Posted by peterxu422 in Science.
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My parents, and I would bargain the parents of most of my fellow Chinese, have made it through difficult challenges when they first immigrated here from China.

My father came here a poor man. He settled and he immediately looked for work which he contributed all of his earnings to his college education. He told me that he used to love eating peanut butter sandwiches but since that was the only thing he ate for a long time, because it was so cheap, he eventually got sick of it.

The only asset he had was his ability to speak English, which was a huge advantage over other immigrants. He worked in a restaurant, went home late to a dangerous neighborhood, studied for his Master’s, and went to classes. He faced other challenges along the way such as getting mugged, getting burned by a searing hot pan, and other hardships I can hardly imagine.

But eventually, he graduated, married my mother, had me and my sister, got a job at a Japanese company, got a teaching job, and bought a home and a comfortable life for his family. Considering the conditions of his own childhood background, he achieved the American dream and did his family proud. He has instilled in me a value of hard work, respect, and intelligence. Now, he and my mom have paved the way for me and my sister so that we may both live better lives.

But now that we have food, clothes, shelter, healthcare, and all these other luxuries that children like when my father was a child could barely comprehend, what does my generation have left to achieve? What is defined by a better life? Food, clothing, shelter, the basic necessities? Is it a good paying job as most Asian parents hope of their children? Have we hit the end of the road and reached the good life? Or is there another challenge that my Chinese generation must face in order to lead a better life as our parents hoped?

The challenge that I believe we face now is the glass ceiling. This arose in a discussion I had recently with my father and Uncle Charlie (not my actual uncle). We were talking about my future and career and to sum things up, Charlie is highly practical and encouraged me to pick a job that makes big money, regardless of the emotional fulfillment of the job. I told him I want to be an engineer and he told me to use my math skills as an accountant. He told me that I could not compete with foreign students in STEM fields and that the only advantage I have over them is my ability to communicate effectively in English and I needed to make use of this. I countered him saying that managers of tech businesses need both the tech knowledge as well as the communication skills.

Effectively, he told me that I did not seem like the managerial type. I was not white enough. In this society, the people at the top positions of our job markets are tall, handsome, white people. Even within our own native countries, you see white managers and CEOs in Hong Kong businesses. It is a white dominated world and I have no chance of breaking into that niche. So he encouraged me to aim a little lower than I expected, take the road of least resistance, and live a comfortable life.

Is this really what is expected of the Chinese community, even from those within our own Chinese culture? It is precisely because of this type of mindset that restricts our people from entering the ranks of high society. How are we expected to take on these roles if our own people do not believe we can acquire them? Did the Civil Rights movement take place because Dr. Martin Luther King told his people to aim for jobs as laborers and not as leaders? I am in no way comparing the difficulties of my generation to the difficulties of his, but I am drawing parallels that I see in terms of ethnic challenges that face both of our people.

It was my hopes to simply be an engineer who can build interesting technology and have a fun time doing it. But now I believe that I, and more Chinese of my generation, should aspire to be leaders in our respective fields. I believe we need to innovate and lead so that not only can our Chinese community be represented and recognized in the high ranks of society, but also so that we may serve as role models for the change and the good that we can contribute to the world.

The status quo is unsustainable. So forgive me Uncle Charlie, but I refuse to accept your advice. I refuse to aim lower than my expectations so that I can fill whatever goals I did not achieve with money. I refuse to pursue a career solely for its monetary rewards. I choose to continue on the more competitive path to being an engineer. And I choose to be one of the front runners paving the way for the future of this field. I will do what it takes to show that the Asian people are innovative, creative, strong leaders.

This, I believe, is the new American Dream that we should strive to achieve. Our parents have climbed the financial obstacles to get us to the base of the mountain. Now it is our turn to overcome the social barriers that we face. It’s time to break the glass ceiling and enjoy the view from up top.

Science Details of the Nobel Prize December 4, 2011

Posted by peterxu422 in Science.
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In my previous post, I mentioned that I would go further into the scientific details of the 2011 Nobel Prize in Physics. As a reminder, the winners of the prize, Saul Perlmutter, Brian Schmidt, and Adam Reiss were awarded for their discovery of the accelerating expansion of the universe. This was actually a surprising result that came out of their data, since what was believed for the last century was that the expansion of the universe was decelerating due to the inward pull of gravity.

To measure this supposed deceleration, they needed something known as a standard candle, an object that always shines with the same brightness. For their standard candles, they used Type Ia Supernovae. A supernova is the explosion of a star when it reaches the end of its life. Regular supernovae explode with different brightness depending on the surrounding conditions, making them unreliable standard candles. But Type Ia Supernovae have an interesting property that they always explode with the same brightness.

Type Ia Supernovae are the explosions of white dwarf stars. Near the ends of its lifetime, a star’s outer layer becomes very gaseous and it expands. What remains in the center is a very hot, dense, and white core composed of carbon and oxygen. Water has a density of 1 gram per cubic cm. A white dwarf has a density of 3 million grams per cubic cm. Our sun’s outer layer one day will expand and its circumference would engulf the orbit of the earth and it too will become a white dwarf. Type Ia Supernovae occur in binary star systems, a star system where two stars orbit each other. Since the white dwarf is so dense, its gravity becomes so strong that it sucks the material of its companion star causing the white dwarf to grow. When it grows and reaches the Chandresekhar limit (1.4 times the size of our sun), the white dwarf rips apart and explodes in a blast so powerful it can outshine an entire galaxy. It is believed that white dwarfs get their intrinsic brightness because they only explode when they reach this characteristic limit.

The laureates used two pieces of information of the supernova in order to determine the expansion rate: the brightness and the cosmological redshift. Redshift is a phenomenon where the wavelength of light gets elongated causing it to appear red (red light has long wavelengths, blue light has short). When light travels through space, it gets elongated because space itself is expanding. This causes it to appear red and thus this is cosmological redshift.

By comparing the observed brightness to the intrinsic brightness of the supernova, they determined how far away it was. And using the redshift, they determined how much the universe has expanded since that supernova occurred (as you look farther out in space, you look further back in time). Their plan was to observe supernovae at different distances, therefore different times, and compare them to each other to see how the expansion rate has changed. As you move standard candles farther away from you, they get less bright (imagine a flashlight moving away from you). Since they expected that the universe was decelerating, they also expected that the brightness of the supernova would get less bright more slowly. But what they found was that as they looked further out in space, the brightness became less much faster than they expected. Therefore the only conclusion they could reach was that the universe was expanding at an accelerating rate!

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