Through all of these 8 weeks, I think each and everyone of us learned a lot about subjects that none of us knew a lot about. The ones that always complained and even though they always did complain, I guarantee they still learned some new facts. We are constantly learning things no matter if we wanted to or not, each post allowed us to learn a little bit more. All in all I think this blogging experiment was a good idea. It may have started of with a lot of complaining and a little rough at first, because it was something new to us, and it ended with a lot more complaining, but I still think that this was a good learning experience.
Pertaining to the topics, I personally learned a lot of facts about each topic. They are all interesting and they were fun to research. The last few ones were a little rough because they were required to be longer but I personally enjoyed those ones the most because I learned the most out of the longer posts. I especially enjoyed the last twelve paragraph topic of natural disasters. I found out that there were a lot more natural disasters then I actually realized. I liked most of the topics. I wasn't really fond of the holography one, I think this was definitely my least favorite one. I know I learned a lot from completing these postings, due to all the researching that I had to due to find out all the information for my postings.
If I had to blog again, I would definitely make my comments better next time. I feel that they were lacking and I didn't put a lot of thought into them. I enjoyed all of the topics, but holograms. I would've enjoyed more topics based on physics, like roller coasters. But overall, I would keep a lot things the same, maybe change the topics next time.
I definitely enjoyed this project, even though we had our hard times as a class and bumper our heads with the teacher. We still all got through this project weather of not we like it, it still got done. I hope everyone benefited some way or another with this blogging project weather you complained every single day about doing it. I still personally think everyone still benefited from this project. It allowed us to research a variety of topics, I'm almost certain that a lot of us didn't know a lot about. I feel we gained an abundance of information on each and every topic, as well as adequate information. Overall, I feel that this project was a very good idea and I for the most part enjoyed it.
Tuesday, May 20, 2008
Thursday, May 15, 2008
Natural Disasters
Introduction
There are many natural disasters out there that take many lives each year. All anyone can do is warn people when they are going to occur. There is nothing to stop these nautral disasters. All you can do is board up your house, hope it's going to be there when you get back if you evacuate, and evacuate for your safety.
Tornado
Tornadoes are one of weathers most deadly and fascinating forces. Even though they are often limited by size (not being more than one kilometer wide at most) they leave vast areas of destruction and death behind them. They are also called twisters or cyclones. Tornadoes are characterized by violent winds that swirl in a counter clockwise direction north of the equator and clockwise south of the equator. Most people recognize them as a towering black funnel extending downward from the base of a large cumulonimbus cloud. It rotates at speeds up to three hundred miles per hour (480 km) or in some rare cases, even faster. In the center of the tornado, the air pressure is very low in comparison to surrounding air pressure. The speed of the wind is the primary cause of deaths and destruction of property. Many people are killed by flying objects and debris (missiles). The funnel shaped cloud travels in a skip like movement, and usually never lasts for more than a couple of minutes in any one given place. It is because of this skip movement that the tornado leaves some areas wrecked while others a few yards away almost untouched. Certain parts of the world (i.e. Australia, the Midwestern and Southern US) are more prone to have tornadoes. They also occur more frequently in the spring and summer months. Tornadoes usually occur as part of a severe thunderstorm and often come in advance of cold fronts, however, they can also occur (although less frequently) ahead of warm fronts, and even behind cold fronts. The greatest killer tornado in the United States occurred during the year 1925 in Indiana, Illinois, and Missouri. It was the fastest and largest one ever recorded, with a destructive path two hundred and twenty miles long and one mile wide, and traveled at a speed of sixty miles per hour. It killed six hundred ninety five people and injured over two thousand.
Volcano
A Volcano is a vent in the earth through which hot gases and molten rock rise to the surface. A cone shaped mountain of erupted material around such a vent is also called a volcano. The name is taken from Volcano, an island north of Sicily in the Mediterranean Sea. The island was given its name by the ancient Romans because it spewed smoke like vapor, and was thought to be the home of Vulcan, their god of fire. A Volcano consists of a fissure in the earth's crust, above which a cone of volcanic material has accumulated. At the top of the cone is a bowl-shaped vent called a crater. The cone is formed by the deposition of molten or solid matter that flows or is ejected through the vent from the interior of the earth. The study of volcanoes and volcanic phenomena is called volcanology. Most volcanoes are composite landforms built up partly of lava flows and partly of fragmental materials. Italy's Mount Etna, in Sicily is an example of a composite cone. In successive eruptions, the solid materials fall around the vent on the slopes of the cone, while lava streams issue from the vent and from fissures on the flanks of the cone. Thus, the cone is built up of layers of fragmental materials and flows of lava, all inclined outward away from the vent. Deep lakes, such as Crater Lake in Oregon, eventually occupy some enormous, craterlike basins, called calderas, at the top of long-dormant or extinct volcanoes. Some calderas are the result of cataclysmic explosions that destroy the erupting volcano. Others form when the subterranean magma chamber, emptied by repeated eruptions, can no longer support the weight of the volcanic pile above it. Therefore it collapses.
Tsunami
"Tsunami" is the Japanese word meaning tidal wave. A tidal wave is a large sea wave caused by a submarine earthquake or volcanic explosion. When the ocean floor is tilted or offset during an earthquake, a set of waves is created. These waves are similar to the concentric waves generated by an object dropped into the water. Usually tsunamis move entirely across an ocean to the shore. A tsunami can have wavelengths of 60 to 120 mi and may reach speeds of 800 km/h. When the wave enters shallow waters, the wave, which may have been half a meter high out at sea, grows rapidly. When the wave reaches the shore, it may be 50 ft. high or more. Tsunamis have incredible energy because of the great volume of water affected. They bring waves of destruction capable of killing thousands of residents along the coast. Towering walls of water have struck populated coastlines with such fury that entire towns have been destroyed. In 1896 a population of 20,000 in Sanriku, Japan were wiped out. Tsunamis have resulted in waves as high as 135 ft. above normal sea level. When a tsunami strikes the shore, it creates a number of waves with troughs that are lower than normal sea level. Each following wave is higher than the one before it. The period between waves is 10 to 30 minutes. This usually gives people ample time to escape to high ground after the first wave. Most tsunamis originate along the Ring of Fire. The Ring of Fire is an area of volcanoes and seismic activity 24,000 mi long. It encircles the Pacific Ocean. Since the year 1819, more than 40 tsunamis have struck the Hawaiian Islands. A tsunami warning system has been developed in areas such as Hawaii, where many devastating tidal waves occur. Hawaii, the highest risk area, averages one tsunami every year with a damaging occurrence every 7 years. Alaska, also at high risk, averages a tsunami every 1.75 years and a damaging event every 7 years. Seismograph records provide the warnings. Seismographs help determine the location of where a submarine earthquake occurred. These earthquakes usually originate in one of the deep trenches in the Pacific Ocean floor. One of the largest and most destructive tsunamis ever recorded traveled at least half way around the world in 1883 after the collapse of Krakatoa, a volcano in Indonesia. Waves up to 100 ft. high caused great damage along the coast of Sumatra. In 1964, an Alaskan earthquake generated a tsunami with waves between 10 and 20 feet high along parts of the California, Oregon, and Washington coasts. This tsunami caused more than $84 million in damage in Alaska and 123 fatalities in Alaska, Oregon, and California. Although tsunamis are rare along the Atlantic coastline, a severe earthquake on November 18, 1929, in the Grand Banks of Newfoundland generated a tsunami that caused considerable damage and loss of lives at Placentia Bay, Newfoundland. In 1946, a tsunami with waves of 20 to 32 feet crashed into Hilo, Hawaii, flooding the downtown area and killing 159 people. The Tsunami Warning Centers in Honolulu, Hawaii, and Palmer, Alaska, monitor disturbances that trigger tsunamis. When tsunamis are recorded, it is tracked and a tsunami warning is issued to the threatened area. Most deaths during a tsunami are a result of drowning. Associated risks include flooding, polluted water supplies, and damaged gas lines. Since 1945, more people have been killed as a result than as a direct result of an earthquake's ground shaking.
Lightning
Even today the phenomenon of lightning is still not fully understood. It is awesome and frightening to many and because of the mystery that surrounds it, several cultures have developed different beliefs about it. Some African cultures believe that when someone is hit by lightning that he/she was cursed even before the event. The Romans and Greeks believed that the gods were fighting and this was one of their weapons. Lightning kills and injures many people, starts thousands of forest fires, and causes millions of dollars in property damage every year. Lightning is characterized by the discharge of electricity between rain clouds or between a rain cloud and the earth. It is usually seen as an arc of extremely bright light, which can be many kilometers in length; however, there are other forms as well. Accompanying the lightning is the giant roar of thunder. The thunder is caused by the expansion of air that has been heated by the lightning, which then collides with cooler air, creating the sound of an explosion. Thunderstorms are the most common types of storms, and thunder itself, although frightening, is not dangerous. It is the lightning that causes the problems. Lightning and thunder occur together, however we hear the thunder after we see the lightning. Sound waves travel about one mile in five seconds, while light travels at more than 186,000 miles per second. Therefore, lightning is seen immediately when it occurs, and thunder is heard a little later. The different sounds of thunder (deep roar/loud crash) is caused by the different types of lightning, for example, the thunder that has the sharp crackle like sound is caused when the large trunk of lightning forks into many branches.
Earthquake
An earthquake is a shaking of the ground caused by the sudden dislocation of material within the earth's outer layer, or crust. When forces pushing on a mass of rock overcome the friction holding the rock in place and blocks of rock slip against each other an earthquake may occur. Some earthquakes are so slight, and some occur in such remote areas, that they are barely felt. Others are so violent that they cause extensive damage.
Drought
Drought is a period or condition of unusually dry weather within a geographic area where rainfall is normally present. During a drought there is a lack of precipitation. Droughts occur in all climatic zones. However, its characteristics vary significantly from one region to another. Drought usually results in a water shortage that seriously interferes with human activity. Water-supply reservoirs empty, wells dry up, and crop damage ensues. Its seriousness depends on the degree of the water shortage, size of area affected, and the duration and warmth of the dry period. In many underdeveloped countries, such as India, people place a great demand on water supply. During a drought period there is a lack of water, and thus many of the poor die. Most precipitation depends on water vapor carried by winds from an ocean or other source of moisture. If these moisture-carrying winds are replaced by winds from a dry region, or if they are modified by downward motion, as in the center of an anticyclone, the weather is abnormally dry and often persistently cloudless. If the drought period is short, it is known as a dry spell. A dry spell is usually more than 14 days without precipitation, whereas a severe drought may last for years. Statistics indicate that every 22 years a major drought occurs in the United States, most seriously affecting the Midwestern states. The drought of 1933-35, during which large areas of the Great Plains became known as the Dust Bowl, is an example of a disastrous drought that took place in the United States. Overcropping, overpopulation, and lack of relief measures brought about the effect of the drought. Although drought cannot be reliably predicted, certain precautions can be taken in drought-risk areas. These include construction of reservoirs to hold emergency water supplies, education to avoid over cropping and overgrazing, and programs to limit settlement in drought-prone areas. The Southern Africa Development Community monitors the crop and food situation in the region and alerts the people during periods of crisis.
Flood
Floods are one of the most common hazards in the United States. Flood effects can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states. However, all floods are not alike. Some floods develop slowly, sometimes over a period of days. But flash floods can develop quickly, sometimes in just a few minutes and without any visible signs of rain. Flash floods often have a dangerous wall of roaring water that carries rocks, mud, and other debris and can sweep away most things in its path. Overland flooding occurs outside a defined river or stream, such as when a levee is breached, but still can be destructive. Flooding can also occur when a dam breaks, producing effects similar to flash floods. Be aware of flood hazards no matter where you live, but especially if you live in a low-lying area, near water or downstream from a dam. Even very small streams, gullies, creeks, culverts, dry streambeds, or low-lying ground that appear harmless in dry weather can flood. Every state is at risk from this hazard.
Landslide and Mudslide
Landslides and mudslides are a serious problem among those people who live in areas with many large hills and mountains, and have affected almost every state in the United States. On the average, 25-50 people in the U.S lose their lives due to mudslide and landslides. Across the world, they have caused billions of dollars in damage and taken thousands of lives. Safety and preparedness are big issues when speaking of mudslides and landslides. But before this very subject can be breeched, an understanding of the cause of mudslides and landslides needs to be acquired. A landslide, by general definition, is the sudden process of a piece of land, usually from an elevated area, breaking away from the whole, and through gravity, is carried down to lower elevations. Landslides are typically associated with periods of heavy rain or large amounts of melting snow. Areas that have been burned by fire have an increased risk of landslides, due to increased soil exposure. Flooding, which is a major concern during heavy rain and snow melt in the first place; can become increasingly worse with the occurrence of a landslide. A mudslide or debris flow, is a type of fast moving landslide. They usually start on steep hillsides as shallow landslides that liquefy and accelerate to speeds that are typically about 10 miles per hour, but can exceed 35 miles per hour. Gravity is the force driving landslide movement. Factors that allow the force of gravity to overcome the resistance of earth material to landslide movement include: saturation by water, steepening of slopes by erosion or construction, alternates freezing or thawing, earthquake shaking, and volcanic eruptions. The consistency of debris flows ranges from watery mud to thick, rocky mud that can carry large items such as boulders, trees, and cars. Debris flows from many different sources can combine in channels, and their destructive power may be greatly increased. They continue flowing down hills and through channels, growing in volume with the addition of water, sand, mud, boulders, trees, and other materials. When the flows reach flatter ground, the debris spreads over a broad area, sometimes accumulating in thick deposits that can wreak havoc in developed areas. Any area composed of very weak or fractured materials resting on a steep slope can and will likely experience landslides. These areas include but are not limited to existing old landslides; the bases of steep slopes; the bases of drainage channels; and developed hillsides where leach-field septic systems are used. Look for various warning signs that would indicate that a landslide is possible, if not probable.
Wildfires
Wildfires are very common in many places around the world, including much of the vegetated areas of Australia as well as the veldt in the interior and the fynbos in the Western Cape of South Africa, and of course, California. The forested areas of the United States and Canada are also susceptible to wildfires. The climates are sufficiently moist to allow the growth of trees, but feature extended dry, hot periods. Fires are particularly prevalent in the summer and fall, and during droughts when fallen branches, leaves, and other material can dry out and become highly flammable. Some suggest that global warming has been increasing the intensity and frequency of droughts in many areas, creating more intense and frequent wildfires. Wildfires are also common in grasslands and scrublands. Wildfires tend to be most common and severe during years of drought and occur on days of strong winds. With extensive urbanization of wild lands, these fires often involve destruction of suburban homes located in the wild land urban interface, a zone of transition between developed areas and undeveloped wild land. Today it is generally accepted that wildfires are a natural part of the ecosystem of numerous wild lands, where some plants have evolved to survive fires by a variety of strategies (from possessing reserve shoots that sprout after a fire, to fire-resistant seeds), or even encourage fire (for example eucalypts contain flammable oils in their leaves) as a way to eliminate competition from less fire-tolerant species. Smoke, charred wood, and head are common fire cues that stimulate the germination of seeds. In 2004, researchers discovered that exposure to smoke from burning plants actually promotes germination in other types of plants by inducing the production of the orange butenolide. However, many ecosystems are suffering from too much fire such as the chaparral in southern California and lower elevation deserts in the American Southwest. The increased fire frequency in these areas has caused the elimination of native plant communities and has replaced them with non-native weeds. These weeds create a positive feedback loop, increasing fire frequency even more. On occasions, wildfires have caused large-scale damage to private or public property, destroying many homes and causing deaths, particularly when they have reached urban-fringe communities. Wildfires are extremely dangerous, but some are purposely caused.
Extreme Heat
Heat kills by pushing the human body beyond its limits. In extreme heat and high humidity, evaporation is slowed and the body must work extra hard to maintain a normal temperature. Most heat disorders occur because the victim has been overexposed to heat or has over-exercised for his or her age and physical condition. Older adults, young children, and those who are sick or overweight are more likely to succumb to extreme heat. Conditions that can induce heat-related illnesses include stagnant atmospheric conditions and poor air quality. Consequently, people living in urban areas may be at greater risk from the effects of a prolonged heat wave than those living in rural areas. Also, asphalt and concrete store heat longer and gradually release heat at night, which can produce higher nighttime temperatures known as the "urban heat island effect."
Winter Weather
When winter temperatures drop significantly below normal, staying warm and safe can become a challenge. Extremely cold temperatures often accompany a winter storm, so you may have to cope with power failures and icy roads. Although staying indoors as much as possible can help reduce the risk of car crashes and falls on the ice, you may also face indoor hazards. Many homes will be too cold—either due to a power failure or because the heating system isn't adequate for the weather. When people must use space heaters and fireplaces to stay warm, the risk of household fires increases, as well as the risk of carbon monoxide poisoning. Exposure to cold temperatures, whether indoor or outside, can cause other serious or life-threatening health problems. Infants and the elderly are particularly at risk, but anyone can be affected. To keep yourself and your family safe, you should know how to prevent cold-related health problems and what to do if a cold-weather health emergency arises. The emergency procedures outlined here are not a substitute for training in first aid. However, these procedures will help you to know when to seek medical care and what to do until help becomes available. What Is Extreme Cold? What constitutes extreme cold and its effects can vary across different areas of the country. In regions relatively unaccustomed to winter weather, near freezing temperatures are considered “extreme cold.” Whenever temperatures drop decidedly below normal and as wind speed increases, heat can leave your body more rapidly. These weather related conditions might lead to serious health problems. Extreme cold is a dangerous situation that can bring on health emergencies in susceptible people, such as those without shelter or who are stranded, or who live in a home that is poorly insulated or without heat.
Hurricane
Hurricanes are one of natures many destructive forces. The word comes from West Indian; hurricane ("big wind"). Hurricanes are seasonal storms and are most prevalent in August and September. They develop from easterly waves, which can later develop into a tropical depression with winds up to 31 miles per hour. Later, it might develop into a tropical storm with winds up to 73 miles per hour, and eventually a hurricane. Thunderstorms often form with hurricanes and then produce waterspouts. Hurricanes are huge tropical cyclones that originate over oceans near the equator, such as the Caribbean Sea and the Gulf of Mexico. Usually they follow a parabola shaped path and sometimes do not reach any land at all. However, if they do reach land, destruction of property is imminent. Winds whirl in a counter clockwise direction in the northern hemisphere and clockwise in the southern hemisphere. Wind speeds of a hurricane range from seventy to one hundred fifty miles per hour. These winds blow circularly around a low-pressure center known as the eye of the storm. Hurricanes cause numerous deaths in addition to the millions of dollars of property damage each year due to the intense winds and huge tidal surges. One of the most destructive elements of a hurricane is the huge wave that is formed because of the strong winds and heavy rains. These waves called a storm surge can rise several feet above water levels, especially during high tide. The worst hurricane in the United States was the one during the year of 1900 in Galveston Texas, where a hurricane swept a fifteen-foot wall of water out of the Gulf of Mexico and into the city, washing away and killing six thousand people. Drowning causes about 90 percent of deaths during a hurricane. Another devastating outcome of a hurricane is the mudslides that can follow. The heavy rains and extensive deforestation in some areas cause these. A good example of this was during the month of July 1998, when a huge mudslide that followed a storm in a little Himalayan village in India, killed hundreds of people.
Cyclone
In meteorology, a cyclone is an area of low atmospheric pressure characterized by inward spiraling winds that rotate counter clockwise in the northern hemisphere and clockwise in the southern hemisphere of the Earth. The generic term covers a wide variety of meteorological phenomena. These include tropical cyclones and extra tropical cyclones, so meteorologists rarely use "cyclone" without additional qualification. There are a number of structural characteristics common to all cyclones. Their center is the area of lowest atmospheric pressure, often known in mature tropical and subtropical cyclones as the eye. Near the center, the pressure gradient force (from the pressure in the center of the cyclone compared to the pressure outside the cyclone) and the Coriolis force must be in an approximate balance, or the cyclone would collapse on itself as a result of the difference in pressure. The wind flow around a large cyclone is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere as a result of the Coriolis effect. (An anticyclone, on the other hand, rotates clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere.) Cold-core cyclones (most cyclone varieties) form due to the nearby presence of an upper level trough, which increases divergence over an area that induces upward motion and surface low pressure. Warm-core cyclones (such as tropical cyclones and many mesocyclones) can have their initial start due to a nearby upper trough, but after formation of the initial disturbance, depend upon a storm-relative upper level high to maintain or increase their strength.
Typhoon
Pacific typhoon refers to tropical cyclones forming in the northwestern Pacific Ocean. The basin is demarcated within the Pacific Ocean from Asia, north of the equator, and west of the International Date Line. Storms from the Eastern and Central Pacific crossing the date line are re-designated as typhoons. This basin features the strongest cyclones on record. Typhoon seasons include the entirety of the calendar year. Most storms tend to form between May and November.
Avalanche
An avalanche is an abrupt and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches are among the biggest dangers in the mountains for both life and property. Several types of snow avalanche may occur. Loose snow avalanches occur when the weight of the snow pack exceeds the shear strength within it, and are most common on steeper terrain. In fresh, loose snow the release is usually at a point and the avalanche then gradually widens down the slope as more snow is entrained, usually forming a teardrop appearance. This is in contrast to a slab avalanche. Slab avalanches account for around 90% of avalanche-related fatalities, and occur when there is a strong, stiff layer of snow known as a slab. These are usually formed when snow is deposited by the wind on a lee slope. When the slab fails, the fracture, in a weak layer, very rapidly propagates so that a large area, that can be hundreds of meters in extent and several meters thick, starts moving almost instantaneously. The third starting type is a slush avalanche, which occurs when the snow pack becomes saturated by water. These tend to also start and spread out from a point. As avalanches move down the slope they may entrain snow from the snow pack and grow in size. The snow may also mix with the air and form a powder cloud. An avalanche with a powder cloud is known as a powder snow avalanche. The powder cloud is a turbulent suspension of snow particles that flows as gravity current. Powder snow avalanches are the largest avalanches and can exceed 300 km/h and 10,000,000 tones of snow; they can flow for long distance along flat valley bottoms and even up hill for short distances. Snow avalanches occur when the load on the upper snow layers exceeds the bonding forces of a mass of snow (bonding to layer beneath, horizontal internal stability, support from anchors such as rocks and trees, stress support from top or bottom of slope). A low timberline will exacerbate the threat because trees help hold snow in place and slow it down once it begins moving. All avalanches are caused by an over-burden of material, typically snow pack that is too massive and unstable for the slope that supports it. Determining the critical load, the amount of over-burden, which is likely to cause an avalanche, is a complex task involving the evaluation of a number of factors. These factors include: Vibrations sound etc.
Lahars
A lahars is a type of mudflow composed of pyroclastic material and water that flows down from a volcano, typically along a river valley. The term 'lahars' originated in the Javanese language of Indonesia. Lahars have the consistency of concrete: fluid when moving, then solid when stopped. Lahars can be huge: the Osceola lahars produced 5,600 years ago by Mount Rainier in Washington produced a wall of mud 140 meters (460 ft) deep in the White River canyon and extends over an area of over 330 square kilometers (130 sq mi) for a total volume of 2.3 cubic kilometers (0.55 cubic miles). Lahars can be extremely dangerous, because of their energy and speed. Large lahars can flow several dozen meters per second and can flow for many kilometers, causing catastrophic destruction in their path. The lahars from the Nevado del Ruiz eruption in Colombia in 1985 caused the Armero tragedy, which killed an estimated 23,000 when the city of Armero was, buried under 5 meters (16 ft) of mud and debris.
Storm Surge
Storm surge is simply water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level 15 feet or more. In addition, wind driven waves are superimposed on the storm tide. This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tides. Because much of the United States' densely populated Atlantic and Gulf Coast coastlines lie less than 10 feet above mean sea level, the danger from storm tides is tremendous. The slope of the continental shelf also determines the level of surge in a particular area. A shallow slope off the coast (right, top picture) will allow a greater surge to inundate coastal communities. Communities with a steeper continental shelf (right, bottom picture) will not see as much surge inundation, although large breaking waves can still present major problems. Storm tides, waves, and currents in confined harbors severely damage ships, marinas, and pleasure boats.
Disease
Outbreak is a classification used in epidemiology to describe a small, localized group of people or organisms infected with a disease. Such groups are often confined to a village or a small area. Outbreaks may also refer to epidemics, which affect a region in a country or a group of countries, or pandemics, which describe global disease outbreaks.
Conclusion
Now that you know a little bit more about all the natural disasters out there, hopefully you won't be wondering as much about how they are created or formed and where they hit.
There are many natural disasters out there that take many lives each year. All anyone can do is warn people when they are going to occur. There is nothing to stop these nautral disasters. All you can do is board up your house, hope it's going to be there when you get back if you evacuate, and evacuate for your safety.
Tornado
Tornadoes are one of weathers most deadly and fascinating forces. Even though they are often limited by size (not being more than one kilometer wide at most) they leave vast areas of destruction and death behind them. They are also called twisters or cyclones. Tornadoes are characterized by violent winds that swirl in a counter clockwise direction north of the equator and clockwise south of the equator. Most people recognize them as a towering black funnel extending downward from the base of a large cumulonimbus cloud. It rotates at speeds up to three hundred miles per hour (480 km) or in some rare cases, even faster. In the center of the tornado, the air pressure is very low in comparison to surrounding air pressure. The speed of the wind is the primary cause of deaths and destruction of property. Many people are killed by flying objects and debris (missiles). The funnel shaped cloud travels in a skip like movement, and usually never lasts for more than a couple of minutes in any one given place. It is because of this skip movement that the tornado leaves some areas wrecked while others a few yards away almost untouched. Certain parts of the world (i.e. Australia, the Midwestern and Southern US) are more prone to have tornadoes. They also occur more frequently in the spring and summer months. Tornadoes usually occur as part of a severe thunderstorm and often come in advance of cold fronts, however, they can also occur (although less frequently) ahead of warm fronts, and even behind cold fronts. The greatest killer tornado in the United States occurred during the year 1925 in Indiana, Illinois, and Missouri. It was the fastest and largest one ever recorded, with a destructive path two hundred and twenty miles long and one mile wide, and traveled at a speed of sixty miles per hour. It killed six hundred ninety five people and injured over two thousand.
Volcano
A Volcano is a vent in the earth through which hot gases and molten rock rise to the surface. A cone shaped mountain of erupted material around such a vent is also called a volcano. The name is taken from Volcano, an island north of Sicily in the Mediterranean Sea. The island was given its name by the ancient Romans because it spewed smoke like vapor, and was thought to be the home of Vulcan, their god of fire. A Volcano consists of a fissure in the earth's crust, above which a cone of volcanic material has accumulated. At the top of the cone is a bowl-shaped vent called a crater. The cone is formed by the deposition of molten or solid matter that flows or is ejected through the vent from the interior of the earth. The study of volcanoes and volcanic phenomena is called volcanology. Most volcanoes are composite landforms built up partly of lava flows and partly of fragmental materials. Italy's Mount Etna, in Sicily is an example of a composite cone. In successive eruptions, the solid materials fall around the vent on the slopes of the cone, while lava streams issue from the vent and from fissures on the flanks of the cone. Thus, the cone is built up of layers of fragmental materials and flows of lava, all inclined outward away from the vent. Deep lakes, such as Crater Lake in Oregon, eventually occupy some enormous, craterlike basins, called calderas, at the top of long-dormant or extinct volcanoes. Some calderas are the result of cataclysmic explosions that destroy the erupting volcano. Others form when the subterranean magma chamber, emptied by repeated eruptions, can no longer support the weight of the volcanic pile above it. Therefore it collapses.
Tsunami
"Tsunami" is the Japanese word meaning tidal wave. A tidal wave is a large sea wave caused by a submarine earthquake or volcanic explosion. When the ocean floor is tilted or offset during an earthquake, a set of waves is created. These waves are similar to the concentric waves generated by an object dropped into the water. Usually tsunamis move entirely across an ocean to the shore. A tsunami can have wavelengths of 60 to 120 mi and may reach speeds of 800 km/h. When the wave enters shallow waters, the wave, which may have been half a meter high out at sea, grows rapidly. When the wave reaches the shore, it may be 50 ft. high or more. Tsunamis have incredible energy because of the great volume of water affected. They bring waves of destruction capable of killing thousands of residents along the coast. Towering walls of water have struck populated coastlines with such fury that entire towns have been destroyed. In 1896 a population of 20,000 in Sanriku, Japan were wiped out. Tsunamis have resulted in waves as high as 135 ft. above normal sea level. When a tsunami strikes the shore, it creates a number of waves with troughs that are lower than normal sea level. Each following wave is higher than the one before it. The period between waves is 10 to 30 minutes. This usually gives people ample time to escape to high ground after the first wave. Most tsunamis originate along the Ring of Fire. The Ring of Fire is an area of volcanoes and seismic activity 24,000 mi long. It encircles the Pacific Ocean. Since the year 1819, more than 40 tsunamis have struck the Hawaiian Islands. A tsunami warning system has been developed in areas such as Hawaii, where many devastating tidal waves occur. Hawaii, the highest risk area, averages one tsunami every year with a damaging occurrence every 7 years. Alaska, also at high risk, averages a tsunami every 1.75 years and a damaging event every 7 years. Seismograph records provide the warnings. Seismographs help determine the location of where a submarine earthquake occurred. These earthquakes usually originate in one of the deep trenches in the Pacific Ocean floor. One of the largest and most destructive tsunamis ever recorded traveled at least half way around the world in 1883 after the collapse of Krakatoa, a volcano in Indonesia. Waves up to 100 ft. high caused great damage along the coast of Sumatra. In 1964, an Alaskan earthquake generated a tsunami with waves between 10 and 20 feet high along parts of the California, Oregon, and Washington coasts. This tsunami caused more than $84 million in damage in Alaska and 123 fatalities in Alaska, Oregon, and California. Although tsunamis are rare along the Atlantic coastline, a severe earthquake on November 18, 1929, in the Grand Banks of Newfoundland generated a tsunami that caused considerable damage and loss of lives at Placentia Bay, Newfoundland. In 1946, a tsunami with waves of 20 to 32 feet crashed into Hilo, Hawaii, flooding the downtown area and killing 159 people. The Tsunami Warning Centers in Honolulu, Hawaii, and Palmer, Alaska, monitor disturbances that trigger tsunamis. When tsunamis are recorded, it is tracked and a tsunami warning is issued to the threatened area. Most deaths during a tsunami are a result of drowning. Associated risks include flooding, polluted water supplies, and damaged gas lines. Since 1945, more people have been killed as a result than as a direct result of an earthquake's ground shaking.
Lightning
Even today the phenomenon of lightning is still not fully understood. It is awesome and frightening to many and because of the mystery that surrounds it, several cultures have developed different beliefs about it. Some African cultures believe that when someone is hit by lightning that he/she was cursed even before the event. The Romans and Greeks believed that the gods were fighting and this was one of their weapons. Lightning kills and injures many people, starts thousands of forest fires, and causes millions of dollars in property damage every year. Lightning is characterized by the discharge of electricity between rain clouds or between a rain cloud and the earth. It is usually seen as an arc of extremely bright light, which can be many kilometers in length; however, there are other forms as well. Accompanying the lightning is the giant roar of thunder. The thunder is caused by the expansion of air that has been heated by the lightning, which then collides with cooler air, creating the sound of an explosion. Thunderstorms are the most common types of storms, and thunder itself, although frightening, is not dangerous. It is the lightning that causes the problems. Lightning and thunder occur together, however we hear the thunder after we see the lightning. Sound waves travel about one mile in five seconds, while light travels at more than 186,000 miles per second. Therefore, lightning is seen immediately when it occurs, and thunder is heard a little later. The different sounds of thunder (deep roar/loud crash) is caused by the different types of lightning, for example, the thunder that has the sharp crackle like sound is caused when the large trunk of lightning forks into many branches.
Earthquake
An earthquake is a shaking of the ground caused by the sudden dislocation of material within the earth's outer layer, or crust. When forces pushing on a mass of rock overcome the friction holding the rock in place and blocks of rock slip against each other an earthquake may occur. Some earthquakes are so slight, and some occur in such remote areas, that they are barely felt. Others are so violent that they cause extensive damage.
Drought
Drought is a period or condition of unusually dry weather within a geographic area where rainfall is normally present. During a drought there is a lack of precipitation. Droughts occur in all climatic zones. However, its characteristics vary significantly from one region to another. Drought usually results in a water shortage that seriously interferes with human activity. Water-supply reservoirs empty, wells dry up, and crop damage ensues. Its seriousness depends on the degree of the water shortage, size of area affected, and the duration and warmth of the dry period. In many underdeveloped countries, such as India, people place a great demand on water supply. During a drought period there is a lack of water, and thus many of the poor die. Most precipitation depends on water vapor carried by winds from an ocean or other source of moisture. If these moisture-carrying winds are replaced by winds from a dry region, or if they are modified by downward motion, as in the center of an anticyclone, the weather is abnormally dry and often persistently cloudless. If the drought period is short, it is known as a dry spell. A dry spell is usually more than 14 days without precipitation, whereas a severe drought may last for years. Statistics indicate that every 22 years a major drought occurs in the United States, most seriously affecting the Midwestern states. The drought of 1933-35, during which large areas of the Great Plains became known as the Dust Bowl, is an example of a disastrous drought that took place in the United States. Overcropping, overpopulation, and lack of relief measures brought about the effect of the drought. Although drought cannot be reliably predicted, certain precautions can be taken in drought-risk areas. These include construction of reservoirs to hold emergency water supplies, education to avoid over cropping and overgrazing, and programs to limit settlement in drought-prone areas. The Southern Africa Development Community monitors the crop and food situation in the region and alerts the people during periods of crisis.
Flood
Floods are one of the most common hazards in the United States. Flood effects can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states. However, all floods are not alike. Some floods develop slowly, sometimes over a period of days. But flash floods can develop quickly, sometimes in just a few minutes and without any visible signs of rain. Flash floods often have a dangerous wall of roaring water that carries rocks, mud, and other debris and can sweep away most things in its path. Overland flooding occurs outside a defined river or stream, such as when a levee is breached, but still can be destructive. Flooding can also occur when a dam breaks, producing effects similar to flash floods. Be aware of flood hazards no matter where you live, but especially if you live in a low-lying area, near water or downstream from a dam. Even very small streams, gullies, creeks, culverts, dry streambeds, or low-lying ground that appear harmless in dry weather can flood. Every state is at risk from this hazard.
Landslide and Mudslide
Landslides and mudslides are a serious problem among those people who live in areas with many large hills and mountains, and have affected almost every state in the United States. On the average, 25-50 people in the U.S lose their lives due to mudslide and landslides. Across the world, they have caused billions of dollars in damage and taken thousands of lives. Safety and preparedness are big issues when speaking of mudslides and landslides. But before this very subject can be breeched, an understanding of the cause of mudslides and landslides needs to be acquired. A landslide, by general definition, is the sudden process of a piece of land, usually from an elevated area, breaking away from the whole, and through gravity, is carried down to lower elevations. Landslides are typically associated with periods of heavy rain or large amounts of melting snow. Areas that have been burned by fire have an increased risk of landslides, due to increased soil exposure. Flooding, which is a major concern during heavy rain and snow melt in the first place; can become increasingly worse with the occurrence of a landslide. A mudslide or debris flow, is a type of fast moving landslide. They usually start on steep hillsides as shallow landslides that liquefy and accelerate to speeds that are typically about 10 miles per hour, but can exceed 35 miles per hour. Gravity is the force driving landslide movement. Factors that allow the force of gravity to overcome the resistance of earth material to landslide movement include: saturation by water, steepening of slopes by erosion or construction, alternates freezing or thawing, earthquake shaking, and volcanic eruptions. The consistency of debris flows ranges from watery mud to thick, rocky mud that can carry large items such as boulders, trees, and cars. Debris flows from many different sources can combine in channels, and their destructive power may be greatly increased. They continue flowing down hills and through channels, growing in volume with the addition of water, sand, mud, boulders, trees, and other materials. When the flows reach flatter ground, the debris spreads over a broad area, sometimes accumulating in thick deposits that can wreak havoc in developed areas. Any area composed of very weak or fractured materials resting on a steep slope can and will likely experience landslides. These areas include but are not limited to existing old landslides; the bases of steep slopes; the bases of drainage channels; and developed hillsides where leach-field septic systems are used. Look for various warning signs that would indicate that a landslide is possible, if not probable.
Wildfires
Wildfires are very common in many places around the world, including much of the vegetated areas of Australia as well as the veldt in the interior and the fynbos in the Western Cape of South Africa, and of course, California. The forested areas of the United States and Canada are also susceptible to wildfires. The climates are sufficiently moist to allow the growth of trees, but feature extended dry, hot periods. Fires are particularly prevalent in the summer and fall, and during droughts when fallen branches, leaves, and other material can dry out and become highly flammable. Some suggest that global warming has been increasing the intensity and frequency of droughts in many areas, creating more intense and frequent wildfires. Wildfires are also common in grasslands and scrublands. Wildfires tend to be most common and severe during years of drought and occur on days of strong winds. With extensive urbanization of wild lands, these fires often involve destruction of suburban homes located in the wild land urban interface, a zone of transition between developed areas and undeveloped wild land. Today it is generally accepted that wildfires are a natural part of the ecosystem of numerous wild lands, where some plants have evolved to survive fires by a variety of strategies (from possessing reserve shoots that sprout after a fire, to fire-resistant seeds), or even encourage fire (for example eucalypts contain flammable oils in their leaves) as a way to eliminate competition from less fire-tolerant species. Smoke, charred wood, and head are common fire cues that stimulate the germination of seeds. In 2004, researchers discovered that exposure to smoke from burning plants actually promotes germination in other types of plants by inducing the production of the orange butenolide. However, many ecosystems are suffering from too much fire such as the chaparral in southern California and lower elevation deserts in the American Southwest. The increased fire frequency in these areas has caused the elimination of native plant communities and has replaced them with non-native weeds. These weeds create a positive feedback loop, increasing fire frequency even more. On occasions, wildfires have caused large-scale damage to private or public property, destroying many homes and causing deaths, particularly when they have reached urban-fringe communities. Wildfires are extremely dangerous, but some are purposely caused.
Extreme Heat
Heat kills by pushing the human body beyond its limits. In extreme heat and high humidity, evaporation is slowed and the body must work extra hard to maintain a normal temperature. Most heat disorders occur because the victim has been overexposed to heat or has over-exercised for his or her age and physical condition. Older adults, young children, and those who are sick or overweight are more likely to succumb to extreme heat. Conditions that can induce heat-related illnesses include stagnant atmospheric conditions and poor air quality. Consequently, people living in urban areas may be at greater risk from the effects of a prolonged heat wave than those living in rural areas. Also, asphalt and concrete store heat longer and gradually release heat at night, which can produce higher nighttime temperatures known as the "urban heat island effect."
Winter Weather
When winter temperatures drop significantly below normal, staying warm and safe can become a challenge. Extremely cold temperatures often accompany a winter storm, so you may have to cope with power failures and icy roads. Although staying indoors as much as possible can help reduce the risk of car crashes and falls on the ice, you may also face indoor hazards. Many homes will be too cold—either due to a power failure or because the heating system isn't adequate for the weather. When people must use space heaters and fireplaces to stay warm, the risk of household fires increases, as well as the risk of carbon monoxide poisoning. Exposure to cold temperatures, whether indoor or outside, can cause other serious or life-threatening health problems. Infants and the elderly are particularly at risk, but anyone can be affected. To keep yourself and your family safe, you should know how to prevent cold-related health problems and what to do if a cold-weather health emergency arises. The emergency procedures outlined here are not a substitute for training in first aid. However, these procedures will help you to know when to seek medical care and what to do until help becomes available. What Is Extreme Cold? What constitutes extreme cold and its effects can vary across different areas of the country. In regions relatively unaccustomed to winter weather, near freezing temperatures are considered “extreme cold.” Whenever temperatures drop decidedly below normal and as wind speed increases, heat can leave your body more rapidly. These weather related conditions might lead to serious health problems. Extreme cold is a dangerous situation that can bring on health emergencies in susceptible people, such as those without shelter or who are stranded, or who live in a home that is poorly insulated or without heat.
Hurricane
Hurricanes are one of natures many destructive forces. The word comes from West Indian; hurricane ("big wind"). Hurricanes are seasonal storms and are most prevalent in August and September. They develop from easterly waves, which can later develop into a tropical depression with winds up to 31 miles per hour. Later, it might develop into a tropical storm with winds up to 73 miles per hour, and eventually a hurricane. Thunderstorms often form with hurricanes and then produce waterspouts. Hurricanes are huge tropical cyclones that originate over oceans near the equator, such as the Caribbean Sea and the Gulf of Mexico. Usually they follow a parabola shaped path and sometimes do not reach any land at all. However, if they do reach land, destruction of property is imminent. Winds whirl in a counter clockwise direction in the northern hemisphere and clockwise in the southern hemisphere. Wind speeds of a hurricane range from seventy to one hundred fifty miles per hour. These winds blow circularly around a low-pressure center known as the eye of the storm. Hurricanes cause numerous deaths in addition to the millions of dollars of property damage each year due to the intense winds and huge tidal surges. One of the most destructive elements of a hurricane is the huge wave that is formed because of the strong winds and heavy rains. These waves called a storm surge can rise several feet above water levels, especially during high tide. The worst hurricane in the United States was the one during the year of 1900 in Galveston Texas, where a hurricane swept a fifteen-foot wall of water out of the Gulf of Mexico and into the city, washing away and killing six thousand people. Drowning causes about 90 percent of deaths during a hurricane. Another devastating outcome of a hurricane is the mudslides that can follow. The heavy rains and extensive deforestation in some areas cause these. A good example of this was during the month of July 1998, when a huge mudslide that followed a storm in a little Himalayan village in India, killed hundreds of people.
Cyclone
In meteorology, a cyclone is an area of low atmospheric pressure characterized by inward spiraling winds that rotate counter clockwise in the northern hemisphere and clockwise in the southern hemisphere of the Earth. The generic term covers a wide variety of meteorological phenomena. These include tropical cyclones and extra tropical cyclones, so meteorologists rarely use "cyclone" without additional qualification. There are a number of structural characteristics common to all cyclones. Their center is the area of lowest atmospheric pressure, often known in mature tropical and subtropical cyclones as the eye. Near the center, the pressure gradient force (from the pressure in the center of the cyclone compared to the pressure outside the cyclone) and the Coriolis force must be in an approximate balance, or the cyclone would collapse on itself as a result of the difference in pressure. The wind flow around a large cyclone is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere as a result of the Coriolis effect. (An anticyclone, on the other hand, rotates clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere.) Cold-core cyclones (most cyclone varieties) form due to the nearby presence of an upper level trough, which increases divergence over an area that induces upward motion and surface low pressure. Warm-core cyclones (such as tropical cyclones and many mesocyclones) can have their initial start due to a nearby upper trough, but after formation of the initial disturbance, depend upon a storm-relative upper level high to maintain or increase their strength.
Typhoon
Pacific typhoon refers to tropical cyclones forming in the northwestern Pacific Ocean. The basin is demarcated within the Pacific Ocean from Asia, north of the equator, and west of the International Date Line. Storms from the Eastern and Central Pacific crossing the date line are re-designated as typhoons. This basin features the strongest cyclones on record. Typhoon seasons include the entirety of the calendar year. Most storms tend to form between May and November.
Avalanche
An avalanche is an abrupt and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches are among the biggest dangers in the mountains for both life and property. Several types of snow avalanche may occur. Loose snow avalanches occur when the weight of the snow pack exceeds the shear strength within it, and are most common on steeper terrain. In fresh, loose snow the release is usually at a point and the avalanche then gradually widens down the slope as more snow is entrained, usually forming a teardrop appearance. This is in contrast to a slab avalanche. Slab avalanches account for around 90% of avalanche-related fatalities, and occur when there is a strong, stiff layer of snow known as a slab. These are usually formed when snow is deposited by the wind on a lee slope. When the slab fails, the fracture, in a weak layer, very rapidly propagates so that a large area, that can be hundreds of meters in extent and several meters thick, starts moving almost instantaneously. The third starting type is a slush avalanche, which occurs when the snow pack becomes saturated by water. These tend to also start and spread out from a point. As avalanches move down the slope they may entrain snow from the snow pack and grow in size. The snow may also mix with the air and form a powder cloud. An avalanche with a powder cloud is known as a powder snow avalanche. The powder cloud is a turbulent suspension of snow particles that flows as gravity current. Powder snow avalanches are the largest avalanches and can exceed 300 km/h and 10,000,000 tones of snow; they can flow for long distance along flat valley bottoms and even up hill for short distances. Snow avalanches occur when the load on the upper snow layers exceeds the bonding forces of a mass of snow (bonding to layer beneath, horizontal internal stability, support from anchors such as rocks and trees, stress support from top or bottom of slope). A low timberline will exacerbate the threat because trees help hold snow in place and slow it down once it begins moving. All avalanches are caused by an over-burden of material, typically snow pack that is too massive and unstable for the slope that supports it. Determining the critical load, the amount of over-burden, which is likely to cause an avalanche, is a complex task involving the evaluation of a number of factors. These factors include: Vibrations sound etc.
Lahars
A lahars is a type of mudflow composed of pyroclastic material and water that flows down from a volcano, typically along a river valley. The term 'lahars' originated in the Javanese language of Indonesia. Lahars have the consistency of concrete: fluid when moving, then solid when stopped. Lahars can be huge: the Osceola lahars produced 5,600 years ago by Mount Rainier in Washington produced a wall of mud 140 meters (460 ft) deep in the White River canyon and extends over an area of over 330 square kilometers (130 sq mi) for a total volume of 2.3 cubic kilometers (0.55 cubic miles). Lahars can be extremely dangerous, because of their energy and speed. Large lahars can flow several dozen meters per second and can flow for many kilometers, causing catastrophic destruction in their path. The lahars from the Nevado del Ruiz eruption in Colombia in 1985 caused the Armero tragedy, which killed an estimated 23,000 when the city of Armero was, buried under 5 meters (16 ft) of mud and debris.
Storm Surge
Storm surge is simply water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level 15 feet or more. In addition, wind driven waves are superimposed on the storm tide. This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tides. Because much of the United States' densely populated Atlantic and Gulf Coast coastlines lie less than 10 feet above mean sea level, the danger from storm tides is tremendous. The slope of the continental shelf also determines the level of surge in a particular area. A shallow slope off the coast (right, top picture) will allow a greater surge to inundate coastal communities. Communities with a steeper continental shelf (right, bottom picture) will not see as much surge inundation, although large breaking waves can still present major problems. Storm tides, waves, and currents in confined harbors severely damage ships, marinas, and pleasure boats.
Disease
Outbreak is a classification used in epidemiology to describe a small, localized group of people or organisms infected with a disease. Such groups are often confined to a village or a small area. Outbreaks may also refer to epidemics, which affect a region in a country or a group of countries, or pandemics, which describe global disease outbreaks.
Conclusion
Now that you know a little bit more about all the natural disasters out there, hopefully you won't be wondering as much about how they are created or formed and where they hit.
Wednesday, May 14, 2008
Holography
History
Denis Gabor made the first hologram while working on electron microscopes in England in 1947. He used a mercury arc lamp and produced a hologram of a small transparency containing the names of famous scientists. His main problem was the lack of a coherent light source. The invention of the laser in the 1960s gave holography the coherent light source needed to give the size, brightness and depth of image which have intrigued and delighted viewers ever since. At first lasers were only available in universities and research laboratories, but now they are much cheaper, making them available to individuals. Further development introduced pulsed lasers which give a very powerful flash of only a few nanoseconds, enabling holograms to be made of living subjects.
In 1962 Emmett Leith and Juris Upatnieks of the University of Michigan recognized from their work in side-reading radar that holography could be used as a 3-D visual medium. In 1962 they read Gabor's paper and "simply out of curiosity" decided to duplicate Gabor's technique using the laser and an "off-axis" technique borrowed from their work in the development of side-reading radar. The result was the first laser transmission hologram of 3-D objects (a toy train and bird). These transmission holograms produced images with clarity and realistic depth but required laser light to view the holographic image. Their pioneering work led to standardization of the equipment used to make holograms. Today, thousands of laboratories and studios possess the necessary equipment: a continuous wave laser, optical devices (lens, mirrors and beam splitters) for directing laser light, a film holder and an isolation table on which exposures are made. Stability is absolutely essential because movement as small as a quarter wave- length of light during exposures of a few minutes or even seconds can completely spoil a hologram. The basic off-axis technique that Leith and Upatnieks developed is still the staple of holographic methodology.
Yuri Denisyuk, a Russian, devised an elegant method of using a single beam to act as both reference and object beam. Placing the film between the laser and the object allows the beam to pass through the film and be reflected off the object, so that the reference beam impinges on the film from one side, and the object beam from the other. Transmission holograms illuminated by white light give a "rainbow smear" effect. In 1968 Stephen Benton discovered a way of eliminating this effect. He made a transfer hologram masking off the master hologram through a narrow horizontal slit; when the second hologram is flipped, the image of the slit appears in front of the hologram close to the viewpoint, and only light of one colour is seen. This gives rise to the "rainbow" effect; as the viewpoint is moved vertically, the colour of the hologram changes. The invention of an embossing technique meant that holograms could be mass-produced for use as security devices and to enhance magazine covers. I
n 1972 Lloyd Cross developed the integral hologram by combining white-light transmission holography with conventional cinematography to produce moving 3-dimensional images. Sequential frames of 2-D motion-picture footage of a rotating subject are recorded on holographic film. When viewed, the composite images are synthesized by the human brain as a 3-D image.
Types of Holography
Transmission Holograms: Viewable with laser light. They are made with both beams approaching the film from the SAME side.
Reflection (White Light) Holograms: Viewable with white light from a suitable source such as spotlight, flashlight, the sun, etc. They are made with the two beams approaching the holographic film from OPPOSITE sides.
Multiple channel holograms: Two or more images are visible from different angles. There are different types of multiple channel holograms: Simple ones with 2, 3, or a few images each viewed from a different angle.
Multiplex: A large number of "flat" pictures of a subject viewed from different angles are combined into a single, 3-dimensional image of the object. A COMPOSED hologram.
Rainbow holograms: The same image appears in a different color when viewed from different angles.
Real Image Holograms (H-2's): These are usually reflection holograms made from a transmission original (H-1). The image dramatically projects IN FRONT OF THE PLATE toward the viewer. Most holograms in holography museums are of this type. The procedure for making them is quite elaborate and demands precise control of angles.
How It Works
The way that holograms work is described here. Holograms work by recording the patterns of light and interference patterns on holographic film or plates. You see light is a wave (and a particle but that part isn’t relevant here.) As with any wave, light has crests and troughs. The crest is the top of the wave and the trough, the bottom. When two waves meet, one of a few things happen: The crests and troughs coincide. When this happens the amplitude (”height”) of the wave doubles. This is called constructive interference (sounds like an oxymoron, doesn’t it?)
The two waves are completely out of sync. This causes the crests and troughs to overlap. If the two waves had the same amplitude, they will cancel each other out completely. This is destructive interference.
The last possibility is when the waves aren’t in perfect sync, or perfectly inverse. When this happens you get a unique pattern of interference. How does that make holograms?” When you make a hologram, you are actually recording those patterns of interference. The principle is that if you take two waves and put them together, you get a unique third wave. By subtracting one of the first two waves from the third you can re-create the other original wave. So by shining light on the hologram, you get one of the patterns of light waves back. Because the light you shine on the hologram is constant (not in a pattern) it looks the most like the reference beam (the one that shines directly on the film). This causes the other light waves to be re-constructed, giving you the object beam. And the object beam is a “copy” of the light reflected off the original object. Because the light picked up by each eye is a little different, and because the interference pattern is different for every light beam that hits the hologram, it comes out differently. Because the eyes pick up slightly different versions of the image, the brain is fooled into seeing a 3D image. So in reality this is basically an optical illusion.
Current and Future Uses
Some current applications that use holographic technology are:
· Holographic interferometry is used by researchers and industry designers to test and design many things, from tires and engines to prosthetic limbs and artificial bones and joints.
· Supermarket and department store scanners use a holographic lens system that directs laser light onto the bar codes of the merchandise.
· Holographic optical elements (HOE’s) are used for navigation by airplane pilots. A holographic image of the cockpit instruments appears to float in front of the windshield. This allows the pilot to keep his eyes on the runway or the sky while reading the instruments. This feature is available on some models of automobiles.
· Medical doctors can use three-dimensional holographic CAT scans to make measurements without invasive surgery. This technique is also used in medical education.
· Holograms are used in advertisements and consumer packaging of products to attract potential buyers.
· Holograms have been used on covers of magazine publications. One of the most memorable Sports Illustrated covers was the December 23, 1992 issue featuring Michael Jordan. Holograms have also been used on sports trading cards.
· The use of holograms on credit cards and debit cards provide added security to minimize counterfeiting.
· Holography has been used to make archival recordings of valuable and/or fragile museum artifacts.
· Sony Electronics uses holographic technology in their digital cameras. A holographic crystal is used to allow the camera to detect the edge of the subject and differentiate between it and the background. As a result, the camera is able to focus accurately in dark conditions.
· Holography has been use by artists to create pulsed holographic portraits as well as other works of art.
Future applications of holography include:
· Future colour liquid crystal displays (LCD’s) will be brighter and whiter as a result of holographic technology. Scientists at Polaroid Corp. have developed a holographic reflector that will reflect ambient light to produce a whiter background.
· Many researchers believe that holographic televisions will become available within 10 years at a cost of approximately $5000. Holographic motion picture technology has been previously attempted and was successful in the 1970s. The future of holographic motion pictures may become a reality within the next few years.
· Holographic memory is a new optical storage method that can store 1 terabyte (= 1000 GB) of data in a crystal approximately the size of a sugar cube. In comparison, current methods of storage include CD’s that hold 650 to 700 MB, DVD’s that store 4.7 GB, and computer hard drives that hold up to 120 GB.
· Optical computers will be capable of delivering trillions of bits of information faster than the latest computers.
Denis Gabor made the first hologram while working on electron microscopes in England in 1947. He used a mercury arc lamp and produced a hologram of a small transparency containing the names of famous scientists. His main problem was the lack of a coherent light source. The invention of the laser in the 1960s gave holography the coherent light source needed to give the size, brightness and depth of image which have intrigued and delighted viewers ever since. At first lasers were only available in universities and research laboratories, but now they are much cheaper, making them available to individuals. Further development introduced pulsed lasers which give a very powerful flash of only a few nanoseconds, enabling holograms to be made of living subjects.
In 1962 Emmett Leith and Juris Upatnieks of the University of Michigan recognized from their work in side-reading radar that holography could be used as a 3-D visual medium. In 1962 they read Gabor's paper and "simply out of curiosity" decided to duplicate Gabor's technique using the laser and an "off-axis" technique borrowed from their work in the development of side-reading radar. The result was the first laser transmission hologram of 3-D objects (a toy train and bird). These transmission holograms produced images with clarity and realistic depth but required laser light to view the holographic image. Their pioneering work led to standardization of the equipment used to make holograms. Today, thousands of laboratories and studios possess the necessary equipment: a continuous wave laser, optical devices (lens, mirrors and beam splitters) for directing laser light, a film holder and an isolation table on which exposures are made. Stability is absolutely essential because movement as small as a quarter wave- length of light during exposures of a few minutes or even seconds can completely spoil a hologram. The basic off-axis technique that Leith and Upatnieks developed is still the staple of holographic methodology.
Yuri Denisyuk, a Russian, devised an elegant method of using a single beam to act as both reference and object beam. Placing the film between the laser and the object allows the beam to pass through the film and be reflected off the object, so that the reference beam impinges on the film from one side, and the object beam from the other. Transmission holograms illuminated by white light give a "rainbow smear" effect. In 1968 Stephen Benton discovered a way of eliminating this effect. He made a transfer hologram masking off the master hologram through a narrow horizontal slit; when the second hologram is flipped, the image of the slit appears in front of the hologram close to the viewpoint, and only light of one colour is seen. This gives rise to the "rainbow" effect; as the viewpoint is moved vertically, the colour of the hologram changes. The invention of an embossing technique meant that holograms could be mass-produced for use as security devices and to enhance magazine covers. I
n 1972 Lloyd Cross developed the integral hologram by combining white-light transmission holography with conventional cinematography to produce moving 3-dimensional images. Sequential frames of 2-D motion-picture footage of a rotating subject are recorded on holographic film. When viewed, the composite images are synthesized by the human brain as a 3-D image.
Types of Holography
Transmission Holograms: Viewable with laser light. They are made with both beams approaching the film from the SAME side.
Reflection (White Light) Holograms: Viewable with white light from a suitable source such as spotlight, flashlight, the sun, etc. They are made with the two beams approaching the holographic film from OPPOSITE sides.
Multiple channel holograms: Two or more images are visible from different angles. There are different types of multiple channel holograms: Simple ones with 2, 3, or a few images each viewed from a different angle.
Multiplex: A large number of "flat" pictures of a subject viewed from different angles are combined into a single, 3-dimensional image of the object. A COMPOSED hologram.
Rainbow holograms: The same image appears in a different color when viewed from different angles.
Real Image Holograms (H-2's): These are usually reflection holograms made from a transmission original (H-1). The image dramatically projects IN FRONT OF THE PLATE toward the viewer. Most holograms in holography museums are of this type. The procedure for making them is quite elaborate and demands precise control of angles.
How It Works
The way that holograms work is described here. Holograms work by recording the patterns of light and interference patterns on holographic film or plates. You see light is a wave (and a particle but that part isn’t relevant here.) As with any wave, light has crests and troughs. The crest is the top of the wave and the trough, the bottom. When two waves meet, one of a few things happen: The crests and troughs coincide. When this happens the amplitude (”height”) of the wave doubles. This is called constructive interference (sounds like an oxymoron, doesn’t it?)
The two waves are completely out of sync. This causes the crests and troughs to overlap. If the two waves had the same amplitude, they will cancel each other out completely. This is destructive interference.
The last possibility is when the waves aren’t in perfect sync, or perfectly inverse. When this happens you get a unique pattern of interference. How does that make holograms?” When you make a hologram, you are actually recording those patterns of interference. The principle is that if you take two waves and put them together, you get a unique third wave. By subtracting one of the first two waves from the third you can re-create the other original wave. So by shining light on the hologram, you get one of the patterns of light waves back. Because the light you shine on the hologram is constant (not in a pattern) it looks the most like the reference beam (the one that shines directly on the film). This causes the other light waves to be re-constructed, giving you the object beam. And the object beam is a “copy” of the light reflected off the original object. Because the light picked up by each eye is a little different, and because the interference pattern is different for every light beam that hits the hologram, it comes out differently. Because the eyes pick up slightly different versions of the image, the brain is fooled into seeing a 3D image. So in reality this is basically an optical illusion.
Current and Future Uses
Some current applications that use holographic technology are:
· Holographic interferometry is used by researchers and industry designers to test and design many things, from tires and engines to prosthetic limbs and artificial bones and joints.
· Supermarket and department store scanners use a holographic lens system that directs laser light onto the bar codes of the merchandise.
· Holographic optical elements (HOE’s) are used for navigation by airplane pilots. A holographic image of the cockpit instruments appears to float in front of the windshield. This allows the pilot to keep his eyes on the runway or the sky while reading the instruments. This feature is available on some models of automobiles.
· Medical doctors can use three-dimensional holographic CAT scans to make measurements without invasive surgery. This technique is also used in medical education.
· Holograms are used in advertisements and consumer packaging of products to attract potential buyers.
· Holograms have been used on covers of magazine publications. One of the most memorable Sports Illustrated covers was the December 23, 1992 issue featuring Michael Jordan. Holograms have also been used on sports trading cards.
· The use of holograms on credit cards and debit cards provide added security to minimize counterfeiting.
· Holography has been used to make archival recordings of valuable and/or fragile museum artifacts.
· Sony Electronics uses holographic technology in their digital cameras. A holographic crystal is used to allow the camera to detect the edge of the subject and differentiate between it and the background. As a result, the camera is able to focus accurately in dark conditions.
· Holography has been use by artists to create pulsed holographic portraits as well as other works of art.
Future applications of holography include:
· Future colour liquid crystal displays (LCD’s) will be brighter and whiter as a result of holographic technology. Scientists at Polaroid Corp. have developed a holographic reflector that will reflect ambient light to produce a whiter background.
· Many researchers believe that holographic televisions will become available within 10 years at a cost of approximately $5000. Holographic motion picture technology has been previously attempted and was successful in the 1970s. The future of holographic motion pictures may become a reality within the next few years.
· Holographic memory is a new optical storage method that can store 1 terabyte (= 1000 GB) of data in a crystal approximately the size of a sugar cube. In comparison, current methods of storage include CD’s that hold 650 to 700 MB, DVD’s that store 4.7 GB, and computer hard drives that hold up to 120 GB.
· Optical computers will be capable of delivering trillions of bits of information faster than the latest computers.
Tuesday, May 6, 2008
Renewable Energy
Wind Power
Using the wind to create electricity has been around for a long time you've probably seen windmills on farms. When the wind turns the blades of a windmill, it spins a turbine inside a small generator to produce electricity, just like a big coal power plant. A windmill on a farm can make only a small amount of electricity enough to power a few farm machines. To make enough electricity to serve lots of people, power companies build "wind farms" with dozens of huge wind turbines. Wind farms are built in flat, open areas where the wind blows at least 14 miles per hour. How a wind turbine works: A wind turbine works the opposite of a fan. Instead of using electricity to make wind, a turbine uses wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. The electricity is sent through transmission and distribution lines to a substation, then on to homes, business and schools.
Solar Power
“Solar” is the Latin word for “sun” and it’s a powerful source of energy. In fact, the sunlight that shines on the Earth in just one hour could meet world energy demand for an entire year. We can use solar power in two different ways: as a heat source, and as an energy source. People have used the sun as a heat source for thousands of years. Families in ancient Greece built their homes to get the most sunlight during the cold winter months. In the 1830s, explorer John Herschel used a solar collector to cook food during an adventure in Africa. You can even try this at home. Today we can use solar collectors for heating water and air in our homes. If you’ve seen a house with big shiny panels on the roof, that family is using solar power. We can also use solar energy to make electricity. The process is called photovoltaics. If you have a solar powered watch or calculator, you’re using photovoltaics. In 1954, scientists at Bell Telephone discovered that silicon (an element found in sand) created an electric charge when it was exposed to lots of sunlight. Just a few years later, silicon chips were used to help power space satellites.
Wave Power
Waves are caused by the wind blowing over the surface of the ocean. In many areas of the world, the wind blows with enough consistency and force to provide continuous waves. There is tremendous energy in the ocean waves. Wave power devices extract energy directly from the surface motion of ocean waves or from pressure fluctuations below the surface. Wave power varies considerably in different parts of the world, and wave energy can't be harnessed effectively everywhere. Wave power rich areas of the world include the western coasts of Scotland, northern Canada, southern Africa, Australia, and the northwestern coasts of the United States.
Hydro Power
When it rains in hills and mountains, the water becomes streams and rivers that run down to the ocean. The moving or falling water can be used to do work. Energy, you'll remember is the ability to do work. So moving water, which has kinetic energy, can be used to make electricity. For hundreds of years, moving water was used to turn wooden wheels that were attached to grinding wheels to grind (or mill) flour or corn. These were called grist mills or water mills. Water can either go over the top of the wheel, or the wheel can be placed in the moving river. The flow of the river then turns the wheel at the bottom. Today, moving water can also be used to make electricity. Hydro means water. Hydro-electric means making electricity from water power. Hydroelectric power uses the kinetic energy of moving water to make electricity. Dams can be built to stop the flow of a river. Water behind a dam often forms a reservoir. Dams are also built across larger rivers but no reservoir is made. The river is simply sent through a hydroelectric power plant or powerhouse. Hydro is one of the largest producers of electricity in the United States. Water power supplies about 10 percent of the entire electricity that we use. In states with high mountains and lots of rivers, even more electricity if made by hydro power.
All of there are very efficient ways to save and conserve energy. I think they all work really well but for some reason solar and wind power stick out to me the most as in they would be the most effective ones to use. I think they would produce the most amount of electricy or "power".
Using the wind to create electricity has been around for a long time you've probably seen windmills on farms. When the wind turns the blades of a windmill, it spins a turbine inside a small generator to produce electricity, just like a big coal power plant. A windmill on a farm can make only a small amount of electricity enough to power a few farm machines. To make enough electricity to serve lots of people, power companies build "wind farms" with dozens of huge wind turbines. Wind farms are built in flat, open areas where the wind blows at least 14 miles per hour. How a wind turbine works: A wind turbine works the opposite of a fan. Instead of using electricity to make wind, a turbine uses wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. The electricity is sent through transmission and distribution lines to a substation, then on to homes, business and schools.
Solar Power
“Solar” is the Latin word for “sun” and it’s a powerful source of energy. In fact, the sunlight that shines on the Earth in just one hour could meet world energy demand for an entire year. We can use solar power in two different ways: as a heat source, and as an energy source. People have used the sun as a heat source for thousands of years. Families in ancient Greece built their homes to get the most sunlight during the cold winter months. In the 1830s, explorer John Herschel used a solar collector to cook food during an adventure in Africa. You can even try this at home. Today we can use solar collectors for heating water and air in our homes. If you’ve seen a house with big shiny panels on the roof, that family is using solar power. We can also use solar energy to make electricity. The process is called photovoltaics. If you have a solar powered watch or calculator, you’re using photovoltaics. In 1954, scientists at Bell Telephone discovered that silicon (an element found in sand) created an electric charge when it was exposed to lots of sunlight. Just a few years later, silicon chips were used to help power space satellites.
Wave Power
Waves are caused by the wind blowing over the surface of the ocean. In many areas of the world, the wind blows with enough consistency and force to provide continuous waves. There is tremendous energy in the ocean waves. Wave power devices extract energy directly from the surface motion of ocean waves or from pressure fluctuations below the surface. Wave power varies considerably in different parts of the world, and wave energy can't be harnessed effectively everywhere. Wave power rich areas of the world include the western coasts of Scotland, northern Canada, southern Africa, Australia, and the northwestern coasts of the United States.
Hydro Power
When it rains in hills and mountains, the water becomes streams and rivers that run down to the ocean. The moving or falling water can be used to do work. Energy, you'll remember is the ability to do work. So moving water, which has kinetic energy, can be used to make electricity. For hundreds of years, moving water was used to turn wooden wheels that were attached to grinding wheels to grind (or mill) flour or corn. These were called grist mills or water mills. Water can either go over the top of the wheel, or the wheel can be placed in the moving river. The flow of the river then turns the wheel at the bottom. Today, moving water can also be used to make electricity. Hydro means water. Hydro-electric means making electricity from water power. Hydroelectric power uses the kinetic energy of moving water to make electricity. Dams can be built to stop the flow of a river. Water behind a dam often forms a reservoir. Dams are also built across larger rivers but no reservoir is made. The river is simply sent through a hydroelectric power plant or powerhouse. Hydro is one of the largest producers of electricity in the United States. Water power supplies about 10 percent of the entire electricity that we use. In states with high mountains and lots of rivers, even more electricity if made by hydro power.
All of there are very efficient ways to save and conserve energy. I think they all work really well but for some reason solar and wind power stick out to me the most as in they would be the most effective ones to use. I think they would produce the most amount of electricy or "power".
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