Category Archives: Physics

Radar: Luftwaffe’s Nemesis

Figure 1
Figure 1

Ever since Louis Bleriot made the first flight across the English Channel, the Britons realized that the possibility of being attacked from the air became a reality. It is this historical event that caused the Ministry of Defense to start developing an air defense system known as the “Chain Home Network”. The primitive stages of this defense network comprise of large ‘hearing blocks’ where the Royal Air Force (RAF) would have someone sit in front of the concrete blocks (above Figure 1) and listen for the sound of approaching airplane armadas. This method did produce results, however, by the time the personnel was able to hear the airplanes and relay it to command center, it was already too late for the RAF to launch an effective counter response. Hence, the Ministry of Defense decided to use another system, which they named the “object-detection system”, but little did they know that it is precisely this system that would turn the tides in favour of the Brits and change the fate of the war during the Battle for Britain. Many historians throughout the world till this day believe that the United Kingdom was key to putting Hitler’s ‘unstoppable’ Blitzkrieg (or lightning war) to a halt in Western Europe. Although what many previously did not realize is that the key component in stopping the infamous Luftwaffe during the Battle of Britain and effectively preventing the invasion of Britain was in fact an intangible system. This system had a classified name: “Radio Detecting and Ranging” object-detection system; or in today’s terms, it’s commonly known as RADAR.

Figure 2
Figure 2

I knew that the RADAR aided the British in stopping the Luftwaffe from my previous knowledge in the history of World War Two, but how did the RADAR do it?  Well, the RADAR transmits pulses of radio waves or microwaves with very long wavelength that bounces off (or reflects off) of any object in their path. Regardless of the size of the object, it returns a tiny part of the wave energy to a radar dish or antenna (shown above) that’s usually located at the same site as the transmitter. The components of RADAR are actually quite simple; it has a transmitter, a waveguide, a duplexer, a receiver, and an electronic station. The transmitter generates the radio signal with an oscillator, which emits the pulses from a radar (similar to that of a sonar sound you hear in the submarines) and the duration is controlled by a modulator (charges up with high voltage to release the pulse which is sent out through the antenna). The waveguide links the transmitter to the antenna, which broadcasts the radio signal. The duplexer is a switch between the antenna and the receiver or transmitter for the signal when the antenna is used in both situations. The radar receiver, receives the signal that is reflected off the object hit by the pulse emitted from the transmitter. This signal is then sent back to the electronic station for interpretation (commonly a visual image of that object on a circular screen showing the location of that object in Figure 3 shown below). I know this to be true because in my Phyiscs class I’ve learned that this concept of radar is valid and proven. So, by being able to detect the German bombers way before they reached Britain, the RAF was able to effectively assemble a counter-attack strike force against the bombers.

Figure 4
Figure 3
Figure 3
Figure 4

In figure 4, it shows the radar (mounted on the top of the AWAC airplane). The radar emits radios waves 360 degrees and when these radio waves ‘hit’ an object (e.g. airplane, flock of birds, etc.) the radio waves are reflected back to the airplane. The amount of time the radio waves take to travel back to the airplane is how far the object is from the radar source. This was the basic functioning of radar. The invention of radar is important then and now because if it weren’t for the development and use of RADAR in World War Two, then a lot more British civilians in London would have been killed and potentially the Luftwaffe might not have been harassed by the RAF on their bombing runs to London, and the Germans could’ve potentially invaded Britain. So, from a British military perspective, the invention of radar not only helped the RAF defend the British mainland but also aided them in bombing runs by methods of triangulation or honing in on a target to get the British bombers on track and hit their targets during blackouts at night. On the contrary however, from a German military perspective, the invention of the radar by the British became a nuisance and a great cost to the Luftwaffe. This is because they now no longer have the advantage of a surprise attack, due to the long detection ranges of the radar, and they have to defend the German cities not only from the American daylight bombing runs, but now from the British night bombing runs as well.

This knowledge and use of radar is also important to modern day times because little do we know that we actually rely on radar almost every single day. Radar has expanded its usage by being placed on airplanes and used for detecting the position of airplanes by air traffic control. Otherwise without radar and with thousands of airplanes flying over the continental US at the same time, it is very likely to crash into another airplane. Another use of radar today is to detect weather patterns and climate change, e.g. formation of a tropical storm/ hurricane, or seeing the position of storm clouds, etc. Now the technology of radar has gotten so advanced that it’s now instead of just detecting objects, radar has now been used to jam other radar in order to make an object become ‘invisible’. So, a major implication from this is that even though radar was designed intentionally for military purposes, throughout the century it has expanded into other areas. This goes to show how such a major invention in World War Two that potentially changed the tide in the Battle for Britain, has found new purposes and adapted in today’s world.

Works Cited:

Brain, Marshall. How Radar Works. HowStuffWorks. Web. 9 Oct. 2011.

How does radar and the Doppler system work?. RADARS. Web. 9 Oct. 2011.

Radar Modulator. Radar Basics. Web. 10 Oct. 2011.

Faster Than LIGHT!

Some of you might heard the news about a new discovery that has the potential to shake the foundation of modern science. A group of nearly 200 scientists works at the Gran Sasso underground laboratory in central Italy discovered a phenomenon that was categorized as impossible by Einstein’s theory of relativity. The scientists discovered a particle, neutrino, that travelled faster than the speed of light, which was viewed as the speed limit in our universe for a long time. (Aczel, Amir D.)

stock-photo-a-glowing-planet-earth-illustration-with-glowing-rings-of-light-spinning-around-it-13173847

How fast is the speed of light? Light travels at a speed of 3*10^8 m/s. In other words, light can go around the Earth for more than 8 loops in 1 second. And according to the modern physics, no matter can travel at or above the speed of light because as matter’s velocity gets closer to speed of light, its mass increases to infinity and time slows to almost zero. This situation is unlikely to happen, and the process takes infinite amount of energy, too. As a result, no matter can be speeded up to the speed of light.

Neutrino is one of the fundamental particles that makes up the universe. Even though neutrino is similar to electrons, but it is electrically neutral, so no forces other than gravity and short-ranged sub-atomic force work on it. This property suggests that neutrino has little interaction with other particles. As the result scientists have little knowledge about neutrinos.

Despite the difficulty to observe, the existence of neutrino was predicted by the theorist Wolfgang Pauli in 1931. He found that energy and momentum of atoms were not conserved during radioactive decay, and this led him to conclude some energy and momentum must be lost through another form, in the form of neutrino. The first electron neutrino was observed in 1959 by Clyde Cowan and Fred Reines. In 1962, Brookhaven National Laboratory and CERN discovered another kind of neutrino that had different properties than electron neutrino was observed. This neutrino was named muon neutrino. The third kind of neutrino, tau neutrino, was discovered in 1978 in SLAC (Stanford Linear Accelerator Center). Lastly, the mass of neutrino was measured in 1985, and the number is surprisingly small, about 10,000 times smaller than that of electron. (“What’s a Neutrino?”)

In modern day, scientists use detector called Super-Kamiokande to detect the presence of neutrino. Neutrino is neutral, but it still interacts with other particles slightly. Super-Kamiokande is filled with water that surrounds by detector, and the detector detects the byproduct of neutrino’s interaction with water molecule. Super-Kamiokande also detects neutrino’s interaction with particles around detectors, and combining both observation to give data. (“Super-Kamiokande”)

Why do we need to care about such tiny particle that hardly interact with anything else? Because it might topples many physic theories and astronomical observations that we have established over the past 100 years. Most of our astronomical observations and physic theories are based on relativity, and one important principle is that nothing can travel faster or at the speed of light. If relativity is proved wrong, then anything build on top of that will no longer be valid. We need to construct everything from the beginning. Other than shaking the foundation of modern science, this discovery might make things human never dare to dream possible. Things such as space travel and even time travel are possible if we can go beyond the speed limit of matter.

Regardless the exciting and influential changes that the discovery might brings, many scientists are still skeptical about the discovery, and they doubt that the discovery is actually a experimental error.

Source

Aczel, Amir D. “Rest Easy, Einstein—Faster-Than-Light Neutrinos Would Not Violate Relativity.” discovermagazine.com. Discover Magazine. 28 September 2011. Web. 11 October 2011.

Matson, John. “Faster-Than-Light Neutrinos? Physics Luminaries Voice Doubts.” scientificamerican.com. Scientific American. 26 September 2011. Web. 11 October 2011.

“What’s a Neutrino?” ps.uci.edu. UCI. n.d. Web. 11 October 2011.

“Super-Kamiokande.” ps.uci.edu. UCI. n.d. Web. 11 October 2011.

Krauthammer, Charles. “In a blink, physics goes lawless, chaotic.” reporternews.com. reporternews. 10 October 2011. Web. 11 October 2011.

(An Invisible Title)

Harry Potter Invisibility Cloak

“I am Harry Potter and this is my invisibility cloak! Look – now you see me… and now you don’t!” The eleven year old me gushed as I was getting ready for a night of trick-or-treating.

“It is just a black cloak wrapped around you, I still see you.” That was when I realized that invisibility was only possible in Harry’s magical world.

Or is it?

Recently, I stumbled across an article that claimed that scientists have created an invisibility cloak by using the ‘mirage effect’. Propelled by my childhood dream to possess such a cloak, I began to delve further into this topic. Before we can move into the science behind how such a cloak is made, we need to first understand the concept of refraction, how the human eye perceives objects and how this leads to the mirage effect. Humans are able to see an object because light waves are reflected or refracted (bent) from the object and then travel to the human eye. Sometimes, however, light waves from an object pass through another medium and bend the light wave another direction. Imagine, for instance, a spoon inside a glass of water – when inside a glass of water, the spoon appears to be ‘broken’. This is because the light waves reflected from the part of the spoon submerged under water, are refracted when they pass through the surface of water. Unfortunately, our brain does not know the light waves from the spoon have been refracted, and thus we perceive the spoon to be at different position under water. Figure 1 below further explains this concept.

Concept of Refraction

Figure 1: Concept of Refraction

The mirage effect is based off this concept. Many of you must have probably experienced driving down a road on a hot summer day and seeing a pool of water in the distance, only to realize that it was actually a mirage. Mirages form because of a temperature gradient between the air and surface of the ground. Usually, light waves from the blue sky are reflected off the surface of a road and thus allow us to see the road ahead. However, in a mirage, a very hot surface causes the light waves from the sky to refract before coming in contact with the road. Since our brain does not know the light wave has been bent, the eye traces the light wave in a straight line to the ground, thus causing our eyes to incorrectly perceive the light waves as a pool of water in the distance (when it is actually refracted light waves from the sky).

Using the concept of the mirage effect, scientists have made an invisibility cloak out of a lattice of carbon nanotubes that when electrically stimulated, either by electrical heating or by a pulse of electromagnetic radiation, create a temperature gradient that cause light waves to bend away from whatever object is under the invisibility cloak. The most important aspect of such an invisibility cloak is the lattice of carbon nanotubes. In order to bend visible light waves, the lattice of carbon nanotubes (also known as metamaterial) must be spaced less than the wavelength of visible light. Till now, researchers have only been able to succeed with near-infrared radiation as our technology is not sophisticated enough as yet to create a lattice with smaller spaces between the carbon nanotubes. Thus, until scientists are able to create a lattice small enough to bend light waves from the visible spectrum, an object will remain visible to the human eye.

Refraction of Light Waves to make Object Invisible

Figure 2: An object covered in an invisibility cloak made of carbon nanotubes that bend the light waves around the object, making the object invisible.

So what does all this really mean? Could Harry Potter’s invisibility cloak really exist? In the future, perhaps yes. Yet, there are even bigger implications of a possible invisibility cloak – good and bad. Using metamaterials to bend light waves, society could improve its security by placing ‘invisible’ policemen around each city. A country’s military could also benefit from such technology as tanks and airbases could be hidden from the human eye. However, such an invisibility cloak could also increase crime rate in the future as this technology could be further developed to bend sound and magnetic waves as well, allowing terrorists carrying guns or bombs to walk through metal detectors undetected. This could arouse an ethical debate over the use of metamaterials and invisibility cloaks. Yet, the debate can wait till the day researchers create the first cloak invisible to the human eye.

Bibliography:

1. “HowStuffWorks “Metamaterials: Bending Light Waves”” HowStuffWorks “Science”Web. 07 Oct. 2011. <http://science.howstuffworks.com/invisibility-cloak6.htm>.

2. “Researchers Create Functional Invisibility Cloak Using ‘Mirage Effect’ | Fox News.” Fox News – Breaking News Updates | Latest News Headlines | Photos & News Videos. Web. 07 Oct. 2011. <http://www.foxnews.com/scitech/2011/10/05/researchers-create-functional-invisibility-cloak-using-mirage-effect/>.

3. “How Do ‘invisibility Cloaks’ Work?| Explore | Physics.org.” Physics.org | Home. Web. 07 Oct. 2011. <http://www.physics.org/article-questions.asp?id=69>.

Why is the Sky Blue?

Perhaps most people know why the sky is blue. But I didn’t. Recently, my little brother asked me, “Why is the sky blue?”. I remember asking this question once, but I never got an answer. As I got older, I forgot all about it and consequently, I never found out the answer. My brother’s question made me remember the curiosity I had as a child and I want to be able to answer his question. This led to my research on why the sky is blue.

Visible light may appear white but is actually a mixture of different colors. The different colors have different wavelengths and frequencies with violet having the shortest wavelength and the highest frequency and red have the longest and lowest frequency. Light travels in a straight line when there is no obstruction. As light enters the atmosphere, it continues in a straight line until it collides with gas molecules or other particles. When light collides with larger particles, it gets reflected. The reflected colors of light are all reflected in the same direction and thus, appear white. However, when light collides with particles that are smaller than the wavelength of light, scattering occurs. Scattering is “a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass“.

Rayleigh scattering, the “dispersion of electromagnetic radiation by particles that have a radius less than approximately 1/10 the wavelength of the radiation“, explains the why the sky is blue. The amount of Rayleigh scattering depends on the size of the particles and the wavelength of the light and is more effective at shorter wavelengths. Therefore, blue light is scattered more strongly than light that are of longer wavelengths. However, if light is scattered more strongly at shorter wavelengths, then another question arises: why isn’t the sky violet? After all, violet light has the shortest wavelength. The reason why the sky isn’t violet is because the sun emits less violet light and our eyes are less sensitive to violet light. This is because our retina has three types of color receptors (cones): red, blue, and green. Our eyes respond most strongly to light at these wavelengths and because the color receptors are stimulated in different proportion, our visual system constructs the colors we see. When we look at the sky, the red cones respond to the small amount scattered red light as well as the orange and yellow lights (but less strongly). The green cones respond to yellow and more the strongly scattered green and green-blue wavelengths. The blue cones on the other hand, respond to colors near the wavelength of blue light, which are very strongly scattered. Because the most strongly scattered indigo and violet wavelengths stimulate both the red cones (slightly) and the blue cones (strongly), we perceive the sky as pale blue.

As children, most of us constantly asked the question why. We used to question almost everything we saw around us, eager to learn more about this world. However, as we grow up, we lose the tendency to ask why and we accept things as they are. As Bernard Baruch said, “Millions saw the apple fall, but Newton asked why.” Asking questions leads to learning; We should try to regain the curiosity we had as children.

Sources

Gibbs, Philipst. “Why is the sky blue?.” The Physics and Relativity FAQ. N.p., n.d. Web. 16 May 2011. <http://math.ucr.edu/home/baez/physics/Administrivia/copyright.html>.

“Blue Sky.” Blue Sky and Rayleigh Scattering. Hyper Physics, n.d. Web. 22 May 2011. <http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html>.

“Rayleigh scattering.” Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica, 2011. Web. 22 May. 2011. <http://www.britannica.com/EBchecked/topic/492483/Rayleigh-scattering>.

“Why is the Sky Blue.” Science Made Simple. SCIENCE MADE SIMPLE, INC., n.d. Web. 22 May 2011. <http://www.sciencemadesimple.com/sky_blue.html>.

“Scattering.” Wikipedia. Wikepedia, 11 05 2011. Web. 22 May 2011. <http://en.wikipedia.org/wiki/Scattering>.

How do nuclear bombs work?

In light of the recent catastrophic events in Japan, I cannot help but wonder about nuclear power, and how it achieves the immense effects it has on our environment. Thus, for this blog post I’ve decided to examine the science behind the workings of the atomic bomb, perhaps one of the greatest threats to the existence of mankind that derives its power from nuclear reactions.

There are two processes from which nuclear or atomic bombs obtain energy: nuclear fission and/or nuclear fusion. Most atomic bombs use nuclear fission, the splitting of the particles of a nucleus of an atom, usually Uranium’s isotopes Uranium-235 and Uranium-233, into smaller particles with a single neutron. This is the process that generates the colossal amount of energy released during an explosion.

Uranium is used in many fission bombs because its isotopes are very heavy and not stable, which means the slightest disturbance to it can set off a series of nuclear fission reactions. When thinking about fission reactions, picture a special set of dominoes that falls not in a single line pattern, but spreading evenly in all directions in a circle. The single domino that is pushed to set off the fall is equivalent to the neutron that starts the nuclear reaction. The reaction is self-sustaining, as soon as an atom of Uranium is split into two lighter atoms, gamma rays and 2 or 3 other neutrons are produced. These newly formed neutrons can then go on to collide with other nuclei and the reaction becomes a vicious cycle of destruction.

In an atomic bomb, there is a vital factor know as the critical mass. When making a bomb, the uranium must be concentrated enough – ie. in supercritical mass – to generate a powerful explosion. Going back to the dominoes metaphor, subcritical mass is where the dominoes are placed too far from each other, and cannot fall properly to make the pattern that it is supposed to. However, if the dominoes are placed closely, in supercritical mass, they will for sure hit one another and induce each and every fall, spreading evenly to keep the falls, or reaction in the case of a nuclear bomb, going. In order for the masses of Uranium to be supercritical, two subcritical masses must be brought together. To do this, the easiest way in a bomb is to collide one subcritical “bullet” of U235 with another subcritical “sphere” of U235

Structure of an Atomic Bomb

When a bomb is dropped, a pressure sensor determines the correct time to set off the explosive charge, when it goes off, the bullet drops down the barrel and hits the sphere. This starts the nuclear fission reaction. The tamper is made of another isotope of Uranium, upon being expanded by the fission reaction it surrounds, exerts pressure and deflects some emitted neutrons back into the reaction to make it even more powerful. Eventually the bomb will explode, and…well, we should all be pretty familiar with the rest from movies and history.

Untwisting the enigma of atomic bombs made me reflect upon a common conflict in society today. As our technology makes amazing improvements upon our lives, it also gives us fantastic power. The bomb described above is ironically named “Little Boy” and yet it is equal to 14,500 tons of TNT. With the fantastic power we have also found fantastic ways to destroy, it seems. And that has with it many risks that will have dire consequences. Thus, when evaluating technology, many people today only see the shortcuts and time it saves us. This is true, of course, the Internet has connected people around the world, and medical advancements save thousands of lives daily. And yet we must remember that not all advancements are positive, or will turn out to be good for mankind. Perhaps Albert Einstein did not foresee the development of the atomic bomb when he began his research on nuclear physics years ago, but the fact of the matter is that atomic weapons could destroy our world, and life as we know it, in a matter of hours today.

MLA Sources:

Fuller, John, and Craig Freudenrich. “HowStuffWorks “How Nuclear Bombs Work”” HowStuffWorks. HowStuffWorks.com. Web. 13 Apr. 2011. <http://www.howstuffworks.com/nuclear-bomb.htm>.

N/A. “The Basic Principle of the Atomic Bomb.” Hiroshima Spirit. Japan Peace Memorial Museum. Web. 13 Apr. 2011. <http://www.hiroshima-spirit.jp/en/museum/morgue_w12.html>.

With a Flick of the Wand…

The first time I saw it, I was amazed. The comforting warm that radiated from it, the welcoming hue that overflowed the room, the occasional snap that filled the silence of the night. Of course, I am speaking of fire.  And with any good fire, there is always an accompanying pale of water. Knowing that water puts out flame is one of the first things that we learn; yet the same simple principle is applied today to combat wildfires and house fires. However, this often causes water damage to the environment, not to mention the need for large amounts of water to be available. But what if there was a way to extinguish such fires with just a flick of a wand?

http://www.ericksonaircrane.com/firefighting.php
http://www.ericksonaircrane.com/firefighting.php

No, I am not speaking of Harry Potter’s magic wand. Scientists at Harvard have developed their own “wand” that can extinguish flame, using electric fields. The “wand” generates an electrical field that can suppress flames very quickly and at a distance as well. Researcher Ludovico Cademartiri demonstrated at the 241st National Meeting of American Chemical Society how such a device worked. He plugged in a 600-watt amplifier and attached the “wand” to the amplifier. With the power of 600 watts, the “wand” was able to generate an electric field of about 1 million volts per meter. While that seems like an absurd amount of energy, 1 million volts per meter is “approximately the field necessary to generate a spark in dry air”, and is therefore, not dangerous to a healthy human. The scientists proceeded to move the rod towards an open flame, about 50 centimeters tall, and almost instantly, the flame died.

A phenomenon like this deems the word “wand” almost fitting, but the concepts behind it are actually quite simple. Inside of any flame, there are electrons, Ions and soot, which all respond to electric fields. By generating a current through the “wand” an electrical field is created and like opposite sides of a magnet, the field generated by the wand repels the electrons, ions and soot inside of the fire. This resulted in the fire being, “pushed” away from its fuel source, and without fuel, the fire will die.

Of course, in real life, firefighters are faced with much larger flames, so a small wand would not be much help. However, scientists are working to increase the distance that the field affects flames, and increase the power of the field generated, so large scale fires can be combated. As this technology develops, the size of the “wand” will decrease, as will the wattage it uses. It seems that only a tenth of what Cademartiri used in his demonstration is needed to put out a that same 50 centimeter flame. Nonetheless, adapting this electrical “wand” for the use of firefighters would be very beneficial to both the economic and environmental aspects of firefighting. Advancements in the “wand” technology will allow firefighters to potentially replace their use of water to put out flames, effectively removing the issue of water damage to the building as well as their reliance of an available water source. Cademartiri also reported that the “wand” could be used to control the heat distribution of flames, so this technology would not be limited to just firefighters. Any technology that requires constant care for overheating can benefit from this technology, as the “wand” and redistribute the heat to prevent overheating.

Works Cited
Choi, Charles. “Electric Wand Makes Fire Disappear.” Daily Nature and Science News and Headlines | National Geographic News. 29 Mar. 2011. Web. 6 Apr. 2011. <http://news.nationalgeographic.com/news/2011/03/110329-electric-wands-fire-firefighters-extinguish-science-harvard-chemical/>.
Melville, Kate. “Electrical “wand” Extinguishes Fires.” Science News, Research And Discussion. 28 Mar. 2011. Web. 6 Apr. 2011. <http://www.scienceagogo.com/news/20110227210048data_trunc_sys.shtml>.

A Wall of Water

March 11, 2011. Breaking News: Japan’s most powerful earthquake since records began has struck the north-east coast, triggering a massive tsunami. In the family room, we watched in silence as the footage of the giant debris-filled wall of water making its way inland was replayed over and over again. As the reporter recounted the details of this earthquake with an intensity of 9.0 on the Richter scale, my mind drifted towards the science behind the formation of these giant havoc-wreaking monsters that have frequently caused heart-breaking destruction and loss of life. More importantly, how do earthquakes lead to these deadly 10meter tall tsunamis?

Before we understand how tsunamis are formed, it is important to understand that the Earth’s crust is not one giant spherical unbroken land mass. Rather, it is made up of jigsaw puzzle like pieces called tectonic plates. These plates move approximately 2 inches a year because of the movement of heat carried from the inner core to the Earth’s crust; however, sometimes the plates move abruptly (as the regular movement is restricted by friction), causing an earthquake.

“But not all earthquakes are the same. It depends on whether the relative movement between the plates is horizontal or vertical.” In addition, the location of an earthquake could be on land, or under the ocean floor. Tsunamis are only formed when the relative movement of the tectonic plates is vertical and under the ocean floor. When the plates move vertically under water, the movement (“thrust”) produces a large displacement of water from its equilibrium position that needs to somehow regain its equilibrium as the gained potential energy converts to kinetic energy in the form of a fast-moving wall of water.

“The water has to go somewhere,” explains Dr Wayne Richardson of the International Seismological Centre, “and it has to go at once. It’s not like a wave breaking at the beach. It’s a mass movement. It can travel, depending on the depth of the water, at up to 950 kilometres per hour (589mph) in the deep ocean.”

As the topography of the sea floor changes and the wave approaches shallow water, the speed slows down and the height of the wave increases (as illustrated in diagram below).

How Tsunamis are Formed

Yet, it is important to note that not every single underwater earthquake will form a tsunami – the magnitude of an earthquake, measured by the Richter’s Scale, must be taken into consideration. Scientific research has proven that usually earthquakes 7.0 and below do not result in tsunamis, and if they do, they rarely lead to massive destruction.

Tsunamis are natural disasters, and they cannot be prevented. It is, therefore, our responsibility to be adequately prepared for this natural calamity.

Due to the fact that Tsunamis have a small amplitude and a long wavelength (up to hundreds of miles) offshore, they can frequently pass unnoticed until they reach shallow water, and therefore it is very important for tsunami-prone nations to install adequate and accurate tsunami sensing and early warning technology. This can be a challenge for poor, underdeveloped nations and I believe that they should be supported by developed nations.

It is also important for the governments of tsunami-prone nations to make wise decisions when building infrastructure offshore/close to shore that could have catastrophic and life-threatening consequences if hit by a tsunami e.g: nuclear power plants, offshore drilling rigs, etc. (as seen in the recent nuclear plant meltdown in Japan)

Last but not the least, it is important that a communication system is in place that allows tsunami warnings to reach every individual in the risk region and an evacuation policy that allows all to be evacuated in due time.

Bibliography:

“Earth Plate Tectonics.” Windows to the Universe. Web. 15 Mar. 2011. <http://www.windows2universe.org/earth/interior/plate_tectonics.html>.

News, Roland Buerk BBC. “BBC News – Japan Earthquake: Tsunami Hits North-east.” BBC – Homepage. Web. 15 Mar. 2011. <http://www.bbc.co.uk/news/world-asia-pacific-12709598>.

Melina, Remy. “Why Do Some Earthquakes Cause Tsunamis But Others Don’t? | Earthquakes & Tsunamis | Life’s Little Mysteries.” Life’s Little Mysteries – A Daily Investigation of the World Around You. Web. 15 Mar. 2011. <http://www.lifeslittlemysteries.com/why-do-some-earthquakes-cause-tsunamis-but-others-dont-1125/>.

“Tsunami Science: a Wall of Water.” Tsunami Science: a Wall of Water. Channel 4 News, 11 Mar. 2011. Web. 15 Mar. 2011. <http://www.channel4.com/news/tsunami-science-a-wall-of-water>.

Reply to Ian’s Post: Shake or Stand?

After reading Ian’s blog post ‘Shake or Stand?’, I suddenly made a connection to my physics class. This is because in his post he had mentioned the words ‘natural frequency’ and coincidentally, we’re learning about waves and natural frequencies in physics. So, what is natural frequency? A frequency that’s natural? No, it is the frequencies at which an object tends to vibrate with when hit, struck, plucked, strummed, or somehow disturbed is known as the natural frequency (the Physics classroom). In simple English, it’s a frequency that causes an object to vibrate back and forth. In his post he also mentions that each building has it’s own unique natural frequency. I did a bit of research and found that the natural frequencies of vibration of a building depend on its mass and how stiff the building is. So, a taller building will have a lower natural frequency because it’s heavier and taller which makes it more flexible (IDEERS). Why is this important? It is important to determine a building’s natural frequency so then you know how the object vibrates, which in turn you can counteract that vibration by using a damper. A damper is a heavy weight that vibrates in the opposite direction of the building thus effectively canceling out any vibrations caused by the building.

The Damper that engineers use in Taipei 101 to counteract any vibrations in the building.
(Figure 1: The Damper that engineers use in Taipei 101 to counteract any vibrations in the building.)

Ian’s post mentions a building reaching it’s natural frequency potentially from vibrations from earthquakes, but a natural frequency of a building doesn’t occur just from earthquakes. It’s also possible for the natural frequency of a building to be reached from wind. As stated in the post, an earthquake causes the ground to vibrate, which in turn sends shockwaves up to the building that causes it to vibrate. The same principle applies to wind, except this time the vibrations start from the top. Wind is weaker at lower elevations because friction (e.g. mountains, hills, buildings, trees) will cause the wind to slow down, and wind is stronger at higher elevations because there is little to no friction. (Air Pressure and Wind). So the higher the building, the more susceptible it is to strong winds. Now, in the present day, engineers have revolutionized their thinking when it comes to buildings, instead of fighting against nature, why not work with nature? The Shanghai World Financial Centre (SWFC) applies this concept. At 492 meters all, the SWFC is the third tallest building in the World. At this height, it means that it is very susceptible to strong winds and it has a huge surface area at the top, which could then lead to the possibility of the building tipping over.

(Figure 2: Picture showing how the wind flows around a building.)
(Figure 2: Picture showing how the wind flows around a building.)

Think of an empty water bottle, it you blow towards the bottom of the bottle it requires a lot of strength to knock it over, however, if you blow towards the top of the water bottle, it tips over very easily. This is the same concept for a building. Which is why engineers have decided to put a big opening at the top of the SWFC, to allow the wind to flow through the building, effectively decreasing the possibility of the building tipping over and vibrating as a result from strong winds.

Figure 2: Picture of the Shanghai World Financial Center
(Figure 3: Picture of the Shanghai World Financial Center)

But wind doesn’t just affect buildings; it also affects other structures such as bridges. A famous example is the Tacoma Narrows Bridge in Washington State. On an early morning of November 7th, 1940, under strong wind conditions, the bridge began to twist and turn in a vertical motion (transverse vibration) (Wikipedia). As the wind became stronger and stronger, it caused the amplitude of the vibrations to increase because the wind was ‘putting in’ more energy then the flexing of the structure can dissipate. The Tacoma Narrows Bridge (aka Galloping Gertie) soon reached its natural frequency and snapped in half. The bridge was rebuilt and this time, the engineers were much more careful and regarded wind with the respect it deserves. A local camera store clerk recorded the collapse of the bridge on film and to this day, it serves to engineering, architecture, and physics students as a warning that nature is not to be underestimated.

Figure 3: Picture showing the collapse of the Tacoma Narrows Bridge in Washington State
(Figure 4: Picture showing the collapse of the Tacoma Narrows Bridge in Washington State)

Click here to see footage of the collapse of the Tacoma Bridge.

Click here to learn more about Resonance and Natural Frequencies.

Click here to learn more about Natural Frequencies and Simple Harmonic Motion

Works Cited:

Resistant Buildings – Vibrating – The Natural Frequency of a Building. IDEERS from Bristol University, 2008. Sun. 27 Feb. 2011.

Resonance and Standing Wave – Natural Frequency. the Physics Classroom, 2011. Sun. 27 Feb. 2011.

Tacoma Narrows Bridge (1940). Wikipedia, 2011. Sun. 27 Feb. 2011.

Wind. Air Pressure and Wind, 2003. Sun. 27 Feb. 2011.

Shake or Stand?

Taipei 101
Taipei 101

Recently in my physics class, the teacher talks about waves and I suddenly remember a show that I watch on National Geography before about Taipei 101, now one of the world’s tallest buildings. Taiwan is a place where earthquakes happen frequently, thus it is very important to make buildings quakeproof, especially for Taipei 101 because of its extraordinary height. To understand how building is designed to be shockproof, we need to first understand how building collapses under the effect of waves, either winds or earthquakes.

So, how does building fail when it is under the effect of waves? Using an earthquake as an example, during an earthquake, the ground is shaking, and the lower part of a building shakes in the same direction as the ground. However, it takes some time for the waves to transfer to the upper part of the building, so the displacements of the lower part and upper part are different. The number of times that a building swings back and forth is called frequency. And all building has a natural frequency, which is a frequency that the energy of the quakes can be transferred most efficiently. When the frequency of quakes get closer to building’s natural frequency, the greater the building will swing, and more damage will be done to the building. (Thomas, “Quake-proof”)

Taipei 101 locates at a place where earthquakes happen frequently, and with its amazing height, wind vibration is also a problem. And how do the builders of Taipei 101 solve the issues of continuous vibrations of the building? They build a huge and heavy tuned mass damper (TMD) within the building. For building as big as Taipei 101, the TMD must be huge. In fact, the TMD in Taipei 101 is 5.5 meter in diameter and weights more than 600 ton. The damper is a pendulum hung from 92nd floor to 88th floor that is “tuned” to match the natural frequency of the building. It will vibrate in the opposite direction to the building, so the forces cancel each other out. Those people who are in IB Physics class might remember the video that Mr. Happer shows us in class on how two waves in opposite direction cancel each other out when they meet. (“Taiwan On Top”)

Tuned Mass Damper in Taipei 101
Tuned Mass Damper in Taipei 101

Why do people build architectures? The purpose is to protect us from the natural forces in the environment around us. The forces can be as small as a rain or as big as an earthquake, and buildings are supposed to shield us from those forces. Our ancestors develop different kinds of building styles in response to differnt dominated forces in a region; throughout time, the building styles become part of our culture. People live in different terrains build architectures differently because they have different problems to solve. However, the difference in building styles demonstrates a common attitude amongst all cultures. This attitude can be best described by a Daoism principle, to act like water. Water is soft and easily changable, and it can change to adapt its environment. The design of Taipei 101 reflects this attitude, since it doesn’t try to fight against nature, but rather the building “shakes” with it.

BiBliography

Thomas, Rachel. “Quake-proof.” +Plus Magzine.com. +Plus Magazine, 10 Feb. 2005. Web. 21 Feb. 2011.

“Taiwan On Top.” ArchitectureWeek.com. ArchitectureWeek, 02 Mar. 2005. Web. 21 Feb. 2011.

“Structure.” Taipei 101.com.tw. Taipei 101, n.d. Web. 21 Feb. 2011.

“Giant Damper Doubles as Building’s Interior Adornment.” ENR.com. 24 Nov. 2003. Web. 21 Feb. 2011.

Reply to Nate’s Post: The Wonders of Fireworks

When I was a child, I used to think fireworks were tricks much like the sparks out of a magician’s wand. Nate’s blog post really made clear for me the chemistry behind the colors, sounds, and psychology behind fireworks. However, I couldn’t help but want to dig deeper into these fascinating explosives that light up our sky.

Which is why, upon further research, I came across a field that I have never before heard of: Pyrotechnics. According to the American Pyrotechnics Association, the definition is as follows: “controlled exothermic chemical reactions that are timed to create the effects of heat, gas, sound, dispersion of aerosols, emission of visible electromagnetic radiation, or a combination of these effects to provide the maximum effect from the least volume.” In a nutshell, pyrotechnics is the science behind creating fireworks. My interest in this field stems from the fact that Pyrotechnicians must have extensively knowledge in both chemistry and physics. Colorful light, as Nate has explained in his post, come from exciting the electrons in different metal salts. But it isn’t only about lights and colors, what about the shapes of fireworks?

A very typical shape for a firework is what’s known as a “spider” effect, which is uniformly round in shape. In order for this shape to be achieved, the aerial shell must be shot high into the air, and a powerful explosion must propel the stars contained within the shell in a straight trajectory, so that they may fan out in all directions (thus creating the round shape) before falling and burning out. Notice as well that the second picture in Nate’s post is a series of fireworks in the “spider” shape.

Fireworks in "Spider" Shape
Typical Spider Firework

Another popular type of fireworks is the roman candle, this firework is outwardly shaped like a candle, as suggested by its name, and is lit from the top (similar to the first picture in Nate’s post). The structure of this type of firework begins with the ignition charge on the very top. Once it is ignited, the fuse will burn through the delay charge and light the star after it. Because the star is packed loosely, the fire may travel via the fuse to the lift charge under the star, igniting that and thereby propelling the star out of the candle and causing it to explode.

Structure of a Roman Candle
Structure of a Roman Candle

This of course is merely two shapes out of many that could be created by applying the studies of Pyrotechnics. In the scientific world today where a myriad of new discoveries are made daily, progress is the key world. And yet the field of Pyrotechnics is build upon the ancient discovery of fireworks by the Chinese, almost 5000 years ago. For us as students, it is important to keep in mind that science is always founded upon previous discoveries, and a simple matter of seeing a firework light up is actually a complex set of ignition and electron transfer happening simultaneously, encompassing topics in both physics and chemistry, and also a entire field devoted to the science behind fireworks. Nothing is ever as simple as it seems, and science can be found within almost every aspect of our lives.

Bibliography:

Ropeik, David. “The Scientific Flash behind the Fireworks.” Science on MSNBC.com. MSNBC, 29 June 2010. Web. 04 Feb. 2011. <http://www.msnbc.msn.com/id/3077329/ns/technology_and_science-science/>.

N/A. “How Do Fireworks Make Those Crazy Shapes? – Newsweek.” Newsweek. Harman Newsweek LLC, July 2009. Web. 15 Feb. 2011. <http://www.newsweek.com/photo/2009/06/30/photos-how-do-fireworks-make-those-crazy-shapes.slide1.html>.

N/A. “Glossary of Pyrotechnic Terms.” American Pyrotechnics Association. American Pyrotechnics Association. Web. 15 Feb. 2011. <http://www.americanpyro.com/Safety Info/glossary.html>.

Russell, Michael S. “Chemistry of Fireworks.” Royal Society of Chemistry. RSC Publishing. Web. 15 Feb. 2011. <http://books.google.com/books?id=-1G-HLDjuP0C&lpg=PP1&hl=fi&pg=PA66#v=onepage&q=roman%20candle&f=false>.