Fireworks are a beautiful sight, but few people are aware of the science behind them. The average firework is made up of a mortar with a charge placed at the bottom made up of gunpowder. On top of the charge sits a structure called the “shell” which contains all the material that produces the actual firework display known as the “stars”. When a fuse is lit, the charge ignites creating an explosion that propels the shell upwards. The shell in turn has a timed fuse that ignites at a certain height. This fuse detonates a secondary charge attached to the shell called the “burst charge”. When the burst charge explodes, it disperses the ignited stars in the shell creating the colored lights we admire during celebrations. To generate bursts of different colors, different elements are used in the fireworks. The principle is that when an element is heated, its atoms absorb this energy and then release it as light of a wavelength characteristic of the element. To create a red color, the firework’s stars are made from the element strontium. For orange, calcium is used. For yellow, green, and blue, sodium, barium, and copper are used, respectively. To obtain a purple color, strontium and copper are mixed in the shell, and to generate the color silver, magnesium and aluminum are used. To produce white light in the firework, magnesium and aluminum are combined with titanium. This, of course, is just a general explanation of the science behind fireworks. There are a lot of nuances to fireworks such as the sounds they make (booms, crackling, or whistling), and the force and timing of the explosions and their directionality with regards to the components of the shell in order to create random or specific patterns in space, also including effects such as strobe or sparks. The video below shows a firework display in Germantown, Maryland in 2013.
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Everybody is familiar with chainsaws nowadays. We associate them with cutting trees, carving wood, or with grislier applications such as those depicted in some horror films. However, the true reason why chainsaws were developed is far removed from the world of lumberjacks, woodcarvers, or slasher movie psychopaths. Chainsaws were developed to aid in childbirth and to facilitate surgeries that involved cutting bones! In the era before anesthesia, antibiotics, or knowledge about the role of germs in infection, when babies got stuck in the birth canal, C-sections were often fatal, so doctors figured out other ways to deliver the baby. For this they performed what is called a symphysiotomy. Towards the front of the body, the birth canal is surrounded by two bones (pubic bones) that are joined together by a joint made out of cartilage called the pubic symphysis. This joint is located above the external genitalia and in front of the bladder. In a symphysiotomy, a doctor would cut through this joint, thus widening the birth canal and allowing birth. In an era when surgery had to be performed very quickly to reduce risks of infection, symphysiotomy, although an improvement over C-sections, was still a risky and laborious procedure that was carried out with saws and knives. But in 1785, the Scottish doctors John Aitken and James Jeffray developed a cutting technique using a hand-powered fine serrated link chain that shortened the length of the procedure and improved its precision. Further refinements to the invention were made until the development of anesthesia and aseptic techniques by the start of the 20th century improved the safety of C-sections and rendered symphysiotomies obsolete. The first chainsaw bearing a resemblance to current chainsaws was made in 1830 by the German Physician Bernhard Heine. It consisted of a serrated link chain that was powered by a hand crank and was called the “osteotome”. The osteotome was used in surgeries that required cutting bone and was an improvement over earlier methods using hammers, chisels, and saws which left splinters and caused a lot of damage to soft tissue. Chain saws designed to cut wood were created at the beginning of the 20th century, and were modelled based on Heine’s osteotome, although they were bulky contraptions that had to be operated by more than one person. It would only be in the 1950’s that the first chainsaws operated by one person were made. Soon thereafter chainsaws began to be used for woodcarving as an art form. This art has evolved into a sophisticated activity featuring various styles, skill levels, and themes that are displayed in national and international competitions. The time-lapse video below was shot at the Montgomery County Agricultural fair in Gaithersburg, Maryland, and features the wood carving art of Joe Stebbing. The image of an osteotome is a private photo taken at Orthopädische Universitätsklinik Frankfurt by Sabine Salfer who has released it into the public domain. One Day I was going to wash the dishes that had accumulated in the sink, but when I turned on the water, something happened that is captured in the video below. Through sheer happenstance, the oven pan placed in the sink was balanced over other dishes in such a manner that when I turned on the water, it started cycling through filled and drained configurations. We had unwittingly created a relaxation oscillator! What is that? The term comes from electronics and refers to a circuit where flowing current charges a device such as a capacitor. Once the capacitor reaches a certain level of charge, it discharges and returns back to its initial uncharged state, only to be charged again by the current repeating the cycle. These oscillating circuits produce low frequency signals that are used in applications such as beepers and blinking lights. However, the term relaxation oscillator can be applied to any system which builds up energy and then releases it, just to build it up again with certain periodicity. One example of a relaxation oscillator is the Old Faithful geyser in Yellowstone National Park. And, as many of my readers have probably figured out by now, the particular relaxation oscillator in my sink has a more colloquial albeit less interesting name: tipping bucket. These contraptions are often found in water parks, works of art, and in applications such as rain gauges. I went to the National Gallery of Art in Washington D.C. and saw an artwork by Jack Whitten entitled Ascension I. This interesting piece was made by applying a tool to generate wavy lines in a background of acrylic paint to create the diagonal interlace pattern that you see in some baskets. Apart from the art itself, one of the things that caught my attention is that when I moved, the pattern of the art piece seemed to pulsate, displaying changes in color and giving off a glare. I was able to capture this with my phone camera in the video below. These optical effects are an example of what is called spatial aliasing. The most well-known example of spatial aliasing is when two grates or meshes are placed on top of each other and one of them is moved. A series of banding patterns appear, which are called interference patterns or Moiré patterns. Spatial aliasing occurs when a signal is not sampled often enough along an axis in space. Our eye and the camera do not monitor reality in a continuous fashion, instead they take samples and then put them together much in the same way that the sensation of movement is generated in a film by playing individual frames one after the other. Spatial aliasing is a problem in any branch of technology that involves waves, such as when playing or recording sounds or generating or producing light. Many industries, ranging from computer graphics to recording studios, implement anti-aliasing techniques to improve the quality of the images or the sound. Another modality of aliasing, called temporal aliasing, is produced when the sampling rate for the signal is insufficient over time. A classic example is the apparent change in rotation speed and direction of the spokes of a wheel. I have previously made a video of the phenomenon of temporal aliasing I observed when shooting a video of the railroad tracks from a moving train. The photos belong to the author and can only be used with permission. I recently went to Left Fork Rocks in Frederick Municipal Forest in Maryland, and while climbing around I saw a snake. The snake was slithering into a cavity in the rocks, so I could not see its head, but I was able to identify it due to the presence of a rattle at the end of its tail. This is a specimen of the timber rattlesnake (Crotalus horridus). I have posted in general about rattlesnakes before, so in this post I will talk about the structure that makes them unique among snakes: the rattle. Many people find similarities between the noise made by the rattle of rattlesnakes and the noise made by maracas. However, unlike the maracas, the rattle does not have tiny balls inside banging against the wall that contains them. Rather, the rattle is composed of hollow segments made of keratin (the same stuff that makes up your fingernails). When the snake shakes its tail 50 – 100 times per second, the segments strike each other and produce the rattling sound. Every time a snake sheds its skin, it adds an additional segment to its rattle, but because the segments of the rattle can become damaged and fall off, the number of segments in a rattle are not a measure of the age of the rattlesnake or of the total number of times it has shed its skin. The function of the rattle is to protect the snake against animals that may inadvertently harm the snake and which are too large for the snake to eat. But how did rattlesnakes get their rattles? One hypothesis is based on the fact that many snakes shake their tails when threatened. Scientists have found that those snakes which are closely related to rattlesnakes shake their tails in a manner that is similar to that of the rattlesnake. Thus, it is suggested that this behavior was a signal precursor that allowed for the selection of snake rattles once they developed. One last interesting fact about the rattle of rattlesnakes is that the snake can’t hear the sound they make with their rattles! Rattlesnakes have inner ear structures which are attached to the lower jaw (they don’t have an eardrum or an external ear like we do) and can sense vibrations transmitted through the ground. Rattlesnakes can perceive airborne sounds that produce vibrations in their bodies, but their overall ability to hear sounds is limited compared to humans. The photograph belongs to the author and can only be used with permission. I went to Carol Creek Linear Park in the city of Frederick, Maryland, and saw this amazing work or art by artist William Cochran. The art, entitled “Archangel”, when viewed head-on appears to be the distorted shape of a winged person. However, when you see it from an angle, you see a normal shape. These types of images are what is called an "anamorphosis". An anamorphosis exploits the fact that our brain puts together a representation of reality based on spatial and geometrical cues. If you manipulate these cues in certain ways, you can produce images that will only appear normal when viewed from certain vantage points. A remarkable historical example of an anamorphosis are the photos taken by Arthur Mole and John Thomas during World War I as part of a campaign to sell war bonds. These photos featured soldiers forming patriotic symbols. In the photo of the Statue of Liberty composition below, the anamorphic character of the image is revealed by the fact that of the 18,000 soldiers that were employed for the image, 12,000 of those soldiers were required just to form the flame part of the statue! Artists both amateur and professional have created many striking anamorphic images. However, far from being something limited to art, anamorphosis is something that has to be taken into account by individuals producing designs that people will see from an angle. Such is the case with road markings. The Archangel photo belongs to the author and cannot be used without permission. The statue of liberty photo is in the public domain. Cats exhibit a behavior where they push out against a soft surface with their front paws alternating between the right and left paw while grasping the surface with each stroke. This behavior is reminiscent of a baker kneading dough and is sometimes referred to as “making biscuits”. As far as we can tell, kneading seems to be an instinctive behavior which most of the time indicates the animal feels secure or relaxed, although excessive kneading may indicate anxiety. There are many proposed explanations as to why cats knead. Among them are: signaling a desire for attention, showing affection, marking their territory, making their bed, stretching their muscles, and as a throw back to the times they were nursing and they would paw their mothers to stimulate the secretion of milk. In the video below, Science Cat demonstrates kneading behavior. When large flocks of birds start flying around back and forth over a given area, they are called a murmuration. Murmurations of birds are an amazing sight. The birds seem to follow each other, and their random movements create areas of low and high density of birds. The overall effect to the observer is that the flock of birds resembles one giant shape-shifting organism. This type of group behavior is also found in other living things such as insects or fish. Murmurations occur towards the end of the day when the birds are set to roost for the night, and they take place during the winter months. Although murmurations seem complex, the behavior that leads to the formation of a murmuration has been realistically recreated by computer simulations that follow simple rules. But why do murmurations happen? There are several hypotheses that have been put forward to explain murmurations. One is that the birds fly around to attract nearby birds in order to form large groups that will make them safer from predators. Another hypothesis is that birds join these large groups to share information about food sources. Yet a third hypotheses posits that the birds join these large groups to stay warmer during the night. The video shows a murmuration of starlings in Poolesville, Maryland. The video shows a light bulb that not only seems to be levitating while rotating but is also on, although it does not seem to be connected to a source of electricity. In case you are wondering, this is not a trick. The levitation is achieved by magnets. Magnets on the periphery of the base attract the light bulb, while magnets in the center of the base repel the light bulb. The result is that the light bulb is locked in position in midair. Once set in motion by a twist, the light bulb can rotate for a very long time because it experiences little friction from the air. As to how the light bulb is on, it is achieved by a phenomenon called “electromagnetic induction”, which was discovered by the English scientist Michael Faraday in 1831. Electromagnetic induction takes place when a moving magnetic field generates a current within a wire. In the case of the levitating light bulb, the base is connected to a power source that generates a moving magnetic field, which in turn induces the electric current inside the base of the light bulb. The principle of magnetic induction is behind electrical generators, and it powers all our electrical gadgets and appliances. With a height of 53 feet, Muddy Creek Falls is the highest free-falling waterfall in Maryland. The falls are in Garret County and are part of the Swallow Falls State Park. The rocks in the falls are mostly sandstones, siltstones, and shales belonging to a formation called the “Pottsville Formation” dating back to a geologic epoch called the Pennsylvanian Period some 300 million years ago. The waters of Muddy Creek Falls join the Youghiogheny River a few hundred feet below the falls. |
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