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Euclidean

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Euclidean last won the day on May 30 2013

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  1. While the Gyrojet was clearly a failure on several levels, the idea of gyroscopically stabilizing rounds seems effective if it is implemented correctly. Has there ever been a new attempt at this technology, or was the concept abandoned altogether?
  2. Kepler orbits about 40 miles or 65 kilometers away from Earth. Since messages are sent using electromagnetic waves, it probably doesn't take long for data to reach Earth (not more than a few microseconds). If anything, sending pictures might be slow because of poor signal strength, and because pictures tend to take up several megabytes of data. Also, if the Kepler takes a lot of pictures in a short span of time, it may have a backlog of images to send due to the slow data transfer rate.
  3. They theorized it and then conducted an experiment to confirm their theory. When it comes to normal substances with positive Kelvin temperatures, we define temperature as the average kinetic energy of the particles in the substance. However, quantum physicists discovered that the energies of the individual particles vary greatly. In a pot of boiling water, for example, only a few of the particles have high energies, while most still have low energies, even though to us the pot is painfully hot to the touch. The distribution of energies in a substance is known as a Boltzmann distribution, and if you look at a Boltzmann distribution for any normal substance, you will see that most of the particles are clustered at the lower end of the energy scale, and only a few actually have high energies. The German scientists, however, sought to create a new substance that essentially inverted the Boltzmann distribution. This means that most of the particles would have high energies, while only a few would have lower energies. In order to create an inverted energy distribution, they needed to enforce a maximum energy for the particles in the gas. Since the total energy of a gas includes its potential and its kinetic energy, they needed to place maxima on both energies. To illustrate why, consider a set of balls on a hill. At the top of the hill, the balls have a lot of potential energy, and therefore they want to roll down the hill and convert their potential energy to kinetic energy. If the kinetic energy of the balls is already maximized, however, then the potential energy cannot be converted, so the balls stay at the top of the hill, and, amazingly, the system remains stable. Using lasers and magnets, the scientists were able to induce maximum values on the potential and kinetic energies of the particles in the gas, and therefore they inverted the Boltzmann distribution of the substance. Since the distribution was inverted, it makes sense to define the absolute temperature as negative, since the term "negative" implies an inversion or negation of something. Hopefully this explanation helped. I essentially condensed the explanation I found online. If you want to read about this concept more in depth, or if my explanation didn't help, check out this article: http://www.mpg.de/6776082/negative_absolute_temperature
  4. When we think of Kelvin temperature, we think only in positives, since zero Kelvin is also absolute zero, the point at which a particle has absolutely no energy, and thus no movement or vibration. Scientists in Germany, however, managed to create the hottest temperatures ever recorded by creating a substance with a negative Kelvin temperature. How is this possible? Well, in order to understand this bizarre concept, we have to go back to our definition of temperature. In thermodynamics, we typically refer to temperature as the average temperature of the particles in a substance. However, because quantum physics deals with energies as the smallest of small scales, and because quantum physics is, from a mathematical perspective, about probabilities, it makes more sense to define temperature as the distribution of the energies of the particles in a substance. So, for example, a boiling pot of water would obviously have plenty of high energy particles buzzing around, but it would have a few low-energy particles too. We simply would pay them no mind because the average energy of the particles is consistent. To a quantum physicist, however, those few low-energy particles matter, because they form part of the energy distribution of the substance. By definition, when a substance has a positive Kelvin temperature, the particles start from a minimum temperature (absolute zero) and spread out toward higher energies. The German scientists, however, wanted to create a substance that started at a maximum temperature and spread toward lower energies. By definition, such a substance would have a negative temperature. Paradoxically, having a negative temperature makes the gas that the scientists created extremely hot. Since the particles start from a maximum temperature and spread to lower temperatures, and since energy flows from hot to cold, heat will always flow away from the negative temperature gas, making it the hottest thing we've ever observed. One of the other interesting properties of negative temperature gases is that they not only have the hottest temperatures, but negative pressures. Normally, a gas concealed in a container would spread out and apply pressure to all sides of the container. A negative temperature gas, on the other hand, causes the atoms in the container to cave inward, as if everything converges to a single point. Because dark matter is believed to have negative pressure as well, this characteristic of negative temperature gases leads scientists to think that studying them may reveal more to us about the elusive dark matter that is believed to account for a lot of "missing mass" in the universe. You can read more about the negative temperature gas and the study conducted by the German scientists here: http://www.sciencenews.org/view/generic/id/347370/description/Hottest_temperature_ever_measured_is_a_negative_one
  5. When quantum physics deals with the smallest of small particles, and computer science deals with elaborate algorithms and problem solving, you might wonder why these two sciences would ever cross paths, but research since the 1980s has spawned a new science from these two already elaborate fields: quantum computing. In quantum computing, rather than using ones and zeros to represent data, the unique quantum state of electrons is used to encode information. This principle is particularly useful in one of computer science's sub-disciplines: cryptography. Cryptography is the study of encrypting and decrypting secret messages and other information. It in itself is a dense field of study because of all the tricks hackers have devised to crack security systems and steal valuable information. Quantum computing though, promises to take cryptography to a whole new level. In traditional cryptographic systems, messages are encoded and decoded using a special key known only to the sender and receiver, but in quantum computing, the individual and unique spins of electrons are known only to the sender and receiver. What is the advantage? Well, if a hacker, for instance, decides to listen in on the conversation, the spins of the electrons will change, and the sender and receiver will know to stop communicating. How does this happen? How can a electron's spin change just by the mere act of observing it? Remember that we see things because photons enter our eyes. Sensors are designed to observe electrons or other atomic and subatomic particles using photons just like the human eye. Recall, though, that a photon is a bundle of energy. Thus, whenever a photon strikes an electron, it gives the electron enough energy to change the electron's trajectory. Thus, the mere act of observing an electron changes the electron's motion. This conundrum is the reason for The Uncertainty Principle in quantum physics, which says that the more you know about the momentum of a particle, the less you know about its position, and the more you know about its position, the less you know about its momentum. This powerful feature - knowing exactly when someone eavesdrops on a conversation - makes quantum encryption virtually unbreakable. Of course, quantum cryptography relies on waves being sent between the sender and receiver, and sometimes it can be difficult to get a clear signal, making quantum cryptography somewhat unreliable at the moment, but with advances in technology, and an evolution in wireless communication, we may one day live in a world where messages are sent safely to their destinations and we will no longer have to worry about hackers intercepting sensitive information. You can read more about a recent study in quantum cryptography here: http://www.sciencenews.org/view/generic/id/349318/description/News_in_Brief_Quantum_cryptography_takes_flight
  6. Euclidean

    The Sound Cloak

    Seeing and hearing are two senses that operate similarly, in that both require waves as sensory input. With sight, light waves enter our eyes, which bend the light toward the retina, which in turn convert the light into electrical impulses that carry information to our brain. With hearing, sound waves cause vibrations in the hairs of our cochlea, an inner part the ear, and the vibrations translate into electrical impulses that go to the brain. Knowing this, scientists have sought for years to cloak objects from our seeing and our hearing by making light and sound waves pass around the objects. While this seems like the most obvious solution, it requires the design and development of complex (and sometimes expensive) synthetic materials. At the Polytechnic Institute in Spain, though, researchers took a different approach. Rather than using some complicated mechanism to make the waves pass around the object, why not change the way the object scatters the waves. Thus, they designed a cage-like structure, which they wrapped around a plastic sphere. The purpose of the strange-looking apparatus was to essentially cancel out the sound waves scattered by the plastic sphere. The waves that scattered from the sphere would, in effect, cancel out with the sound waves emitted by the cage-like structure, so no sound would escape the cage. While the research is admittedly quite preliminary, it opens a door to a whole new angle of cloaking research. Who knows? A decade from now, the US Navy (which, unsurprisingly, helped to fund this research) might be sporting submarines invisible to sonar detectors. You can read more about this fascinating research here: http://www.sciencenews.org/view/generic/id/349255/description/Sound_cloaks_enter_the_third_dimension One thing that stood out to me a lot when I first read the article was that the researchers used a computer simulation that predicted that the sound waves from the sphere and cage-like structure would cancel out. One day, I would love to build simulation programs that can help scientists to do studies like this one. Computer modeling affords us a lot of time saved from frustrating trial and error, and it affords us safety, since we don't have to experiment with something firsthand all the time and we can model the experiment instead. In essence, computer modelling can't replace experimentation, but it can certainly guide our experiments by helping us avoid unnecessary complications. This study is just one of many examples of the advantages of computer modeling.
  7. Euclidean

    Lasers

    Lasers are everywhere. We use them in medicine, telecommunications, manufacturing, and even in our personal computers (to burn a CD, for example). How exactly do they work, though? Typically whenever we turn on a light of some sort, the photons it emits propagate in all directions, yet with a laser, all the photons flow in a neat, straight, steady stream (making them ideal pointers). How does that happen? Many people do not realize it, probably because the term has become so commonplace, but the word "LASER" was originally an acronym that stood for Light Amplification by Stimulated Emission of Radiation. Lasers earned their technical-sounding from the process scientists use to create them. Essentially, light behaves in two ways: like a wave and like a particle. The particle aspect of light, known as a photon, is essentially a tiny bundle of energy. In a laser, electricity sends energy into a sea of excitable atoms, and when the atoms become "excited," their electrons "jump" to a new orbit further from the nucleus. This new orbit is called an energy level, because electrons require an energy transfer to jump from one level to another. In this case, electrons first jump up a level when given energy from a stream or burst of electricity. Afterward, they drop back to their normal energy level, but in order to do so, they must discharge the energy they gained that allowed them to jump in the first place. That discharge occurs in the form of a photon, and when billions of electrons in billions of atoms all emit photons of the same frequency in the same direction at relatively the same time, you have that steady flow of photons we call a laser. Not all photons have the same energy. Max Planck showed that the energy of a photon is directly proportional to its frequency, and the frequency of a photon determines its color as well. Therefore, lasers that emit low-energy photons will appear red, for example, while high-energy photons will appear blue or purple, and mid-energy photons will fall somewhere in the middle, like yellow or green. Thus, the color of the laser emitted from a particular device depends on the energy of the photons being emitted from the electrons as they fall back to their normal energy levels. It's pretty amazing how much physics goes into something as simple-looking as a laser.
  8. Have you ever wondered how spacecraft like the Hubble Telescope or the Kepler can see so remarkably far into space? The physics behind it lies in how light bends around planets and stars as it propagates through space. Einstein showed that massive objects bend the four-dimensional spacetime continuum (with the fourth dimension being time). As a result, light passing by massive objects, like planets, stars, and black holes, bend around the objects as they pass by. The bending of light can magnify or distort the image of a particular object in space, so a colleague of Einstein asked him if it was possible to use this bending phenomenon to create super-telescopes that could peer into the depths of space. Einstein, despite viewing such a notion as pointless, showed mathematically that creating a telescope that used the bending of light around massive objects was indeed possible; however, in the paper he published on the subject, Einstein made a point of noting that such a notion was impractical and would never actually be used. Less than fifty years later, we have the Hubble Telescope orbiting the Earth, giving us breathtaking images of the limitless depths of space. So much for Einstein's pessimistic prediction! Sadly, the Kepler spacecraft recently suffered a malfunction in one of its reaction wheels, which serve as a pointing device for the spacecraft. The malfunction cannot be fixed by astronauts, as with the Hubble telescope, because the Kepler is too far away from Earth. Thus, the malfunction threatens to put the Kepler spacecraft out of business. You can read about the incident here: http://www.sciencenews.org/view/generic/id/350445/description/Kepler_mission_may_be_over Thankfully, all is not lost. The Kepler was intended to collect data for four years, and it slightly exceeded that goal. Also, of the four years of data that the spacecraft collected, much of the last year of data has not been analyzed, so while no new data will be coming in (or at least, less data may be coming in), the scientists at NASA have plenty of not-yet-analyzed data to keep them busy. With already several discoveries of Earth-like planets orbiting distant stars, the remaining data seems promising to astronomers.
  9. For years, scientists have tried to make fusion a viable source of renewable energy for the world. In the sun, hydrogen molecules are smashed together to form helium nuclei and tremendous energy that allows the sun to give off its brilliant light. Scientists have tried to recreate this fusion reaction on a smaller scale so that they can produce tremendous amounts of energy and essentially solve our world's energy problem. In order for an energy source to be viable, the reaction involved must be able to produce more energy then the reaction requires. While we have been able to create fusion reactions in a laboratory (and not just in the hydrogen bomb), the fusion reactions not occurring in hydrogen bombs fail to produce even a half of the energy they require. More frustratingly, every time scientists think they have gotten to the point of achieving a successful fusion reaction (which they have dubbed ignition), rather than one which yields to little energy, they find that they must overcome some new curve ball. In 2009, scientists completed simulation programs, pumped with millions of lines of code and tons of equations and data from careful experiments and measurements, that were designed to predict the behavior of a fusion reaction that would occur in the National Ignition Facility (NIF). The programs were run through the world's fastest supercomputers, and even those took days to weeks to run through the simulations and return the results. Encouragingly, the simulations predicted that lasers fired from all directions at a small pellet of hydrogen fuel would be able to implode the pellet and create a brief, self-sustaining fusion reaction that would produce over 100 times the energy needed by the lasers to induce the reaction. Sounds promising, right? Well, sadly, when the simulations were put to the test, ignition failed miserably, and ever since, scientists have tweaked the process and the hardware to get better results. While they have gotten progressively closer to ignition, they still have a long way to go, and with billions of dollars already spent on the project, scientists and politicians are beginning to wonder if fusion is still a practical option. Now, fusion projects are springing up around the world, with everyone looking for a new or better way to achieve fusion and ultimately achieve ignition. The University of Rochester (right in our backyard!) has been experimenting with the Omega laser to create fusion reactions by firing the lasers directly at the hydrogen pellet, rather than at a hohlraum, or target container, as the NIF laser has. Another project, called ITER, aims to create fusion using powerful electromagnets rather than lasers. The quest for ignition is an uphill battle, with nature throwing curve balls continually at hardworking physicists. While some scientists (and especially politicians) are beginning to wonder if fusion will ever be a practical source of energy, I am still optimistic. If we can finally get it working, we could solve our energy problem almost completely, so even with a multi-billion dollar price tag, I think the research, trial-and-error, and even the disappointments will all be worth it someday. For more information on fusion and the quest for ignition, see the article here: http://www.sciencenews.org/view/feature/id/349381/description/Ignition_Failed
  10. A few years ago, I remember watching a CSI: NY episode where thieves were stealing expensive jewelry from different jewelry stores, and a peculiar problem left the investigators stumped for a part of the episode. The problem had to do with the shattered glass from the glass displays. If a person strikes a glass object, like the casing in the stores or a window, the inside of the glass, which can be seen from a side view of a shard, will leave telltale marks indicating the direction from which the criminal struck the glass. Problematically, the glass from the jewelry stores had no such marks, as if no one touched the glass when it shattered. Eventually the investigators discovered that the thieves, a trio of college physics students, used a high pitch sound generator to create sound waves that shattered the glass without anyone putting a hammer or a fist to the glass directly. The investigators did not realize this at first, even though they'd already found the generator, because it produced sound waves above the range of human hearing. They realized that the mysterious devise was a sound generator when one of them noticed that a dog they found at the scene and had collected for evidence would become aggravated whenever the machine was turned on. When aimed at a piece of glass, the machine caused it to shatter with no telltale marks, and the investigators got one step closer to finding the perpetrators. Sounds a little bizarre, right? Well, it turns out that studying glass patterns can help forensic scientists more than we realized. A recent study found that when high velocity bullets pass through a thin sheets of glass and Plexiglas, the number of cracks created by the bullet is related to the bullet's velocity. So, in theory, forensic scientists can use a windshield's pattern of cracks to get an idea of how fast a bullet was going. Since not all guns fire bullets at the same speed, and since bullets sometimes get damaged when they hit something, making it difficult to analyze the bullet, knowing the bullet's velocity could help investigators to identify a murder weapon when the bullet itself cannot help them. While the study is very preliminary, and used controlled conditions not quite reflective of the materials we use and see in everyday life, it does open our eyes to the possibility of using glass from a crime scene to help tell the story. Here's a like to the story: http://www.sciencenews.org/view/generic/id/350088/description/Counting_cracks_in_glass_gives_speed_of_projectile
  11. Here are links to the stories I found: http://www.sciencenews.org/view/generic/id/349712/description/Dark_matter_detector_reports_hints_of_WIMPs http://www.sciencenews.org/view/generic/id/349352/description/Cosmic_ray_detector_confirms_hints_of_dark_matter
  12. One subject that has received a lot of attention, speculation, and research in the last twenty or more years is the elusive Dark Matter. It gets its peculiar name from the fact that dark matter does not look or behave like normal matter. In fact, we don't even know if it really exists! However, recent experiments, both here on Earth and up in outer space, seem to give clues as to the nature of dark matter. So where did the idea of dark matter come from? It came from a discrepancy in the mass of galaxies, similar to the discrepancy we observe in atoms. The nucleus of an atom consists of protons and neutrons, and since we know the mass of both particles, one would think that we could find the mass of a particular atomic nucleus simply by adding the masses of its constituent protons and neutrons. However, if you take the mass of the nucleus directly, and compare that mass to the sum of the masses of the protons and neutrons in that nucleus, you will find that some of the mass is missing from the nucleus. Einstein explained that when protons and neutrons (which are essentially a proton and electron smashed together) come so close together, as in a nucleus, a Strong Force is needed to hold all those charges together. The discrepancy in mass happens because some of the mass from the protons and neutrons is converted to nuclear energy that fuels the strong force holding the nucleus together. Thus, the mass of the nucleus itself is less than the sum of the masses of its parts. Interestingly, scientists noticed a similar discrepancy in the mass of galaxies. Apparently, a galaxy's stars, planets, dust, and other matter do not fully account for that galaxy's mass. Much of the mass is missing. So where did it go? Why can't we see or detect it? Theoretical physicists proposed the idea that this missing mass is hidden in dark matter, which is supposed to outweigh normal matter in mass by more than 5 to 1. Recently, two experiments have yielded clues about the nature of dark matter. One experiment, known as the Cryogenic Dark Matter Search, used silicon and germanium crystals cooled to near absolute zero. Why? Scientists think that dark matter may consist of Weakly Interacting Massive Particles (WIMPs). In theory, if WIMPs exist, they should very occasionally strike the nucleus of a silicon or germanium atom, which would cause a release of energy and therefore a small vibration in the extremely cooled crystals. The crystals were placed about 700 underground to keep out background noise like stray protons and electrons that could trigger false positives in the crystals. Over the course of about a year, the crystals picked up three signals that could be WIMPs, but scientists have guarded optimism about the results, largely because so few signals have been detected. As a result, they plan to move the crystals further underground (about 2 kilometers) and they plan to use just germanium crystals, which are supposed to be more sensitive than the silicon ones, primarily because the three detected signals occurred at the very lower limit of the crystal's sensitivity, an observation which clashes with the current theories about WIMPs and dark matter. Another, more hopeful experiment, took place on the International Space Station. There, a device known as the Alpha Magnetic Spectrometer (AMS) detected and observed billions of electrons and positrons buzzing in space around the Earth. The purpose of the experiment was to uncover the link between dark matter and cosmic rays, which are essentially charged particles zipping through space. Scientists believe that dark matter particles can collide and annihilate each other, causing bursts of matter and antimatter pairs, such as electrons and positrons or protons and antiprotons. The AMS collected data which showed that the number of positrons observed in cosmic rays increases as their energies rise, but after a certain point, the increase trails off. Scientists want to collect more data from the AMS because, if the number of positrons at high energies suddenly plummets, it could be a sign of dark matter. Of course, some scientists view the AMS data skeptically, remarking that data about positrons and cosmic rays will never reveal anything about dark matter. I, however, am hopeful that this new data, once its collection has finished, will open more avenues of research into dark matter.

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