Portal:Technology/Selected articles
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[edit] 35 mm film
35 mm film is the basic gauge most commonly used for both still photography and motion pictures, and remains relatively unchanged since its introduction in 1892 by William Dickson and Thomas Edison, using film stock supplied by George Eastman. The photographic film is cut into strips 35 mm (about 1 3/8 inches) wide — hence the name. The standard negative pulldown is four perforations per frame along both edges, which makes for exactly 16 frames per foot.
A wide variety of largely proprietary gauges were used by the numerous different camera and projection systems independently invented around the late 19th century and early 20th century, ranging from 13 mm to 75 mm (0.51–2.95 in). Its longevity is largely because its size allows for a relatively good tradeoff between the cost of the film stock and the quality of the images captured. Additionally, the ubiquity of 35 mm movie projectors in commercial movie theaters makes it the only motion picture format, film or video, which can be played in almost any cinema in the world.
[edit] Nuclear weapon
A nuclear weapon is a tool employed to injure, defeat, or destroy an adversary. It derives its destructive force from nuclear reactions of fission or fusion. As a result, even a nuclear weapon with a small yield is significantly more powerful than the largest conventional explosives, and a single weapon is capable of destroying an entire city.
In the history of warfare, nuclear weapons have been used only twice, both during the closing days of World War II. The first event occurred on the morning of August 6, 1945, when the United States dropped a uranium gun-type device code-named "Little Boy" on the Japanese city of Hiroshima. The 2nd event occurred 3 days later when the United States dropped a plutonium implosion-type device code-named "Fat Man" on the city of Nagasaki. The use of these weapons, which resulted in the immediate deaths of around 100,000 to 200,000 people and even more over time, was and remains controversial.
Since the Hiroshima and Nagasaki bombings, nuclear weapons have been detonated on over 2,000 occasions for testing and demonstration purposes. The only countries known to have detonated such weapons are (chronologically) the United States, Soviet Union, United Kingdom, France, People's Republic of China, India, Pakistan, and North Korea.
[edit] Rocket
A rocket or rocket vehicle is a missile, aircraft or other vehicle which obtains thrust by the reaction of the rocket to the ejection of fast moving fluid from a rocket engine. Chemical rockets work by the action of hot gas produced by the combustible forces that accelerate the gas to extremely high speed and exert a large thrust on the rocket (since every action has an equal and opposite reaction).The history of rockets goes back to at least the 13th century.[1] By the 20th century, they have enabled human spaceflight to the Moon. In the 21st century, they have made commercial space tourism possible.
Rockets are used for fireworks and weaponry, as launch vehicles for artificial satellites, human spaceflight and exploration of other planets. While inefficient for low speed use, they are, compared to other propulsion systems, very lightweight and powerful, capable of attaining extremely high speeds with reasonable efficiency and accuracy
[edit] Laser
A laser is a device that emits light (electromagnetic radiation) through a process called stimulated emission. The term laser is an acronym for light amplification by stimulated emission of radiation. Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses. Typically, lasers are thought of as emitting light with a narrow wavelength spectrum ("monochromatic" light). This is not true of all lasers, however: some emit light with a broad spectrum, while others emit light at multiple distinct wavelengths simultaneously. The coherence of typical laser emission is distinctive. Most other light sources emit incoherent light, which has a phase that varies randomly with time and position.
[edit] Interstellar travel
Interstellar space travel is unmanned or manned travel between stars. The concept of interstellar travel in starships is a staple in science fiction. Interstellar travel is tremendously more difficult than interplanetary travel. Intergalactic travel, the travel between different galaxies, is even more difficult.
Many scientific papers have been published about related concepts. Given sufficient travel time and engineering work, both unmanned and generational interstellar travel seem possible, though representing a very considerable technological and economic challenge unlikely to be met for some time, particularly for crewed probes. NASA has been engaging in research into these topics for several years, and has accumulated a number of theoretical approaches.
The main difficulty of interstellar travel is the vast distances that have to be covered and therefore the time it takes with most realistic propulsion methods - from decades to millennia. Hence an interstellar ship would be much more severely exposed to the hazards found in interplanetary travel, including hard vacuum, radiation, weightlessness, and micrometeoroids. The long travel times make it difficult to design manned missions, and make economic justification of any interstellar mission nearly impossible, since benefits that do not become available for decades or longer have a present value close to zero.
[edit] Global Positioning System
The Global Positioning System (GPS) is the only fully functional global navigation satellite system (GNSS). The GPS uses a constellation of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave signals, that enable GPS receivers to determine their location, speed, direction, and time. GPS was developed by the United States Department of Defense. Its official name is NAVSTAR-GPS. Although NAVSTAR-GPS is not an acronym[2], a few backronyms have been created for it[3]. The GPS satellite constellation is managed by the United States Air Force 50th Space Wing.
Similar satellite navigation systems include the Russian GLONASS (incomplete as of 2008[update]), the upcoming European Galileo positioning system, the proposed COMPASS navigation system of China, and IRNSS of India.
Following the shooting down of Korean Air Lines Flight 007 in 1983, President Ronald Reagan issued a directive making the system available free for civilian use as a common good.[4] Since then, GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, scientific uses, and hobbies such as geocaching. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.
[edit] Fusion power
Fusion power is power generated by nuclear fusion reactions. In this kind of reaction, two light atomic nuclei fuse together to form a heavier nucleus and in doing so, release energy. In a more general sense, the term can also refer to the production of net usable power from a fusion source, similar to the usage of the term "steam power." Most design studies for fusion power plants involve using the fusion reactions to create heat, which is then used to operate a steam turbine, similar to most coal-fired power stations as well as fission-driven nuclear power stations.
The largest current experiment is the Joint European Torus [JET]. In 1997, JET produced a peak of 16.1 MW of fusion power (65% of input power), with fusion power of over 10 MW sustained for over 0.5 sec. In June 2005, the construction of the experimental reactor ITER, designed to produce several times more fusion power than the power put into the plasma over many minutes, was announced. The production of net electrical power from fusion is planned for DEMO, the next generation experiment after ITER.
[edit] Solar cell
A solar cell or photovoltaic cell is a device that converts solar energy into electricity by the photovoltaic effect. Photovoltaics is the field of technology and research related to the application of solar cells as solar energy.
Sometimes the term devices intended specifically to capture energy from sunlight , while the term photovoltaic cell is used when the source is unspecified.
Assemblies of cells are used to make solar modules, which may in turn be linked in photovoltaic arrays.
Solar applications. Individual small devices as electronic calculators. Photovoltaic arrays generate a form of renewable electricity, particularly useful in situations where from the grid as in remote area power systems, Earth-orbiting satellites and space probes, remote radiotelephones and water pumping applications. Photovoltaic electricity is also increasingly deployed in grid-tied electrical systems.
Similar devices intended to capture from other sources include thermophotovoltaic cells, betavoltaics cells, and optoelectric nuclear battery.
[edit] Nanotechnology
Nanotechnology, sometimes shortened to "Nanotech", refers to a field whose theme is the control of matter on an atomic and molecular scale. Generally nanotechnology deals with structures 100 nanometers or smaller, and involves developing materials or devices within that size.
Nanotechnology is extremely diverse, ranging from novel extensions of conventional device physics, to completely new approaches based upon molecular self-assembly, to developing new materials with dimensions on the nanoscale, or the scale of nothing, even to speculation on whether we can directly control matter on the atomic scale.
There has been much debate on the future of implications of nanotechnology. Nanotechnology has the potential to create many new materials and devices with wide-ranging applications, such as in medicine, electronics, and energy production. On the other hand, nanotechnology raises many of the same issues as with any introduction of new technology, including concerns about the toxicity and environmental impact of nanomaterials, and their potential effects on global economics, as well as speculation about various doomsday scenarios. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.
[edit] Black hole information paradox
The black hole information paradox results from the combination of quantum mechanics and general relativity. It suggests that physical information could "disappear" in a black hole. It is a contentious subject since it violates a commonly assumed tenet of science—that information cannot be destroyed.
In 1975, Stephen Hawking and Jacob Bekenstein showed that black holes should slowly radiate away energy, which poses a problem. From the no hair theorem one would expect the Hawking radiation to be completely independent of the material entering the black hole. Nevertheless, if the material entering the black hole were a pure quantum state, the transformation of that state into the mixed state of Hawking radiation would destroy information about the original quantum state. This violates Liouville's theorem and presents a physical paradox.
[edit] Superstring theory
Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modelling them as vibrations of tiny supersymmetric strings. It is considered one of the most promising candidate theories of quantum gravity. Superstring theory is a shorthand for supersymmetric string theory because unlike bosonic string theory, it is the version of string theory that incorporates fermions and supersymmetry.
The deepest problem in theoretical physics is harmonizing the theory of general relativity, which describes gravitation and applies to large-scale structures (stars, galaxies, super clusters), with quantum mechanics, which describes the other three fundamental forces acting on the atomic scale.
The development of a quantum field theory of a force invariably results in infinite (and therefore useless) probabilities. Physicists have developed mathematical techniques (renormalization) to eliminate these infinities which work for three of the four fundamental forces – electromagnetic, strong nuclear and weak nuclear forces - but not for gravity. The development of a quantum theory of gravity must therefore come about by different means than those used for the other forces.
[edit] Israel Aerospace Industries
Israel Aerospace Industries (Hebrew: התעשייה האווירית לישראל ha-ta'asiya ha-avirit le-yisra'el) or IAI (תע"א ta`a') is Israel's prime aerospace and aviation manufacturer, producing aerial systems for both military and civilian usage. It has 16,000 employees as of 2007.
In addition to local construction of fighter aircraft, IAI also builds civil aircraft (for Gulfstream, on the G100/G150 and G200) and performs local maintenance of foreign-built military and civilian aircraft. In addition, the company works on a number of missile and avionics systems. In 2003, Israel Aircraft Industries attempted to enter the VLJ (Very Light Jet) Market, by launching the Avocet ProJet, a 6-8 seat, high utilization air taxi, with a list price almost half the cost of the least expensive business jet available at that time.
In early 2006, ProJet stalled after a major undisclosed US OEM pulled out of the program due to unspecified reasons.
Although the IAI main focus is aviation and high-tech electronics, it also manufactures military systems for ground and naval forces. Many of these products are specially suited for Israel Defence Forces needs, while others are also marketed to foreign militaries.
[edit] Lockheed Martin F-16 Fighting Falcon
The Lockheed Martin F-16 Fighting Falcon is a multirole jet fighter aircraft originally developed by General Dynamics for the United States Air Force. Designed as a lightweight fighter, it evolved into a successful multirole aircraft. The Falcon's versatility is a paramount reason it has proven a success on the export market, having been selected to serve in the air forces of 25 nations. The F-16 is the largest Western jet fighter program with over 4,400 aircraft built since production was approved in 1976. Though no longer being bought by the U.S. Air Force, advanced versions are still being built for export customers. In 1993, General Dynamics sold its aircraft manufacturing business to the Lockheed Corporation, which in turn became part of Lockheed Martin after a 1995 merger with Martin Marietta.
The Fighting Falcon is a dogfighter with numerous innovations including a frameless, bubble canopy for better visibility, side-mounted control stick to ease control while under high g-forces, and reclined seat to reduce the effect of g-forces on the pilot. Weapons include a M61 Vulcan cannon and various missiles mounted on up to 11 hardpoints. It was also the first fighter aircraft deliberately built to sustain 9-g turns. It has a thrust-to-weight ratio greater than one, providing enough power to climb and accelerate vertically – if necessary. Although the F-16's official name is "Fighting Falcon", it is known to its pilots as the "Viper", due it resembling a cobra snake and after the Battlestar Galactica starfighter. It is used by the Thunderbirds air demonstration team.
[edit] Space toilet
A space toilet, or zero gravity toilet, is a toilet that can be used in a low gravity environment. In the absence of gravity the collection and retention of liquid and solid waste is directed by use of air flow. Since the air used to direct the waste is returned to the cabin, it is filtered beforehand to control odor and cleanse bacteria. In older systems, waste water is vented into space and any solids are compressed and stored for removal upon landing. More modern systems expose solid waste to vacuum to kill bacteria, which prevents odor problems and kills pathogens.
The toilet used on the Space Shuttle is called the Waste Collection System (WCS). In addition to air flow, it also uses rotating fans to distribute solid waste for in-flight storage. Solid waste is distributed in a cylindrical container which is then exposed to vacuum to dry the waste. Liquid waste is vented to space. During STS-46, one of the fans malfunctioned, and crew member Claude Nicollier was required to perform in-flight maintenance (IFM). An earlier, complete failure, on the eight-day STS-3 test flight, forced its two-man crew (Jack Lousma and Gordon Fullerton) to use the much-hated "Apollo Bag" for waste elimination and disposal.
[edit] Virtual globe
A virtual globe is a 3D software model or representation of the Earth or another world. A virtual globe provides the user with the ability to freely move around in the virtual environment by changing the viewing angle and position. Compared to a conventional globe, virtual globes have the additional capability of representing many different views on the surface of the Earth. These views may be of geographical features, man-made features such as roads and buildings, or abstract representations of demographic quantities such as population.
In 1998, Microsoft released a popular offline virtual globe in the form of Encarta Virtual Globe 98. The first widely publicized online virtual globe was Google Earth.
Virtual globes may be used for study or navigation (by connecting to a GPS device) and their design varies considerably according to their purpose. Those wishing to portray a visually accurate representation of the Earth often use satellite image servers and are capable not only of rotation but also zooming and sometimes horizon tilting. Very often such virtual globes aim to provide as true a representation of the world as is possible with worldwide coverage up to a very detailed level. When this is the case the interface often has the option of providing simplified graphical overlays to highlight man-made features since these are not necessarily obvious from a photographic aerial view. The other issue raised by such detail available is that of security with some governments having raised concerns about the ease of access to detailed views of sensitive locations such as airports and military bases.
[edit] Area 51
Area 51 is a nickname for a military base located in the southern portion of Nevada in the western United States (north-northwest of Las Vegas). Situated at its center, on the southern shore of Groom Lake, is a large military airfield and one of the most secretive places in the world. The base's primary purpose is to support development and testing of experimental aircraft and weapons systems.
The base lies within the United States Air Force's vast Nevada Test and Training Range. Although the facilities at the range are managed by the 99th Air Base Wing at Nellis Air Force Base, the Groom facility appears to be run as an adjunct of the Air Force Flight Test Center (AFFTC) at Edwards Air Force Base in the Mojave Desert, around 160 miles (260 km) from Groom, and as such the base is known as Air Force Flight Test Center (Detachment 3). Area 51 researcher Glenn Campbell claims that AFFTC Detachment 3 is located at Groom, citing the title of a leaked security manual, the mailbox in Henderson, Nevada he believes formerly served Groom, and the NASA biography of astronaut Carl E. Walz who was formerly a manager at AFFTC detachment 3 (AFFTC-DET3.)
[edit] Colonization of Callisto
NASA performed a study called HOPE (Revolutionary Concepts for Human Outer Planet Exploration) regarding the future exploration of the solar system. The target chosen was Callisto, a moon of Jupiter. It could be possible to build a surface base that would produce fuel for further exploration of the solar system.
Because it is outside of Jupiter's radiation belt and also geologically very stable, it could prove to be a suitable place for a base. This base would also be a center for exploration of the Jovian system, for example remote exploration of Ganymede and Europa. It would also be the ideal location for a Jovian system way station that could service spacecraft headed farther into the outer Solar System, using a gravity assist from a close fly-by of Jupiter after departing Callisto.
[edit] Radioactive decay
Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide. For example: a carbon-14 atom (the "parent") emits radiation and transforms to a nitrogen-14 atom (the "daughter"). This is a random process on the atomic level, in that it is impossible to predict when a given atom will decay, but given a large number of similar atoms the decay rate, on average, is predictable.
The SI unit of radioactive decay is the becquerel (Bq). One Bq is defined as one transformation (or decay) per second. Since any reasonably-sized sample of radioactive material contains many atoms, a Bq is a tiny measure of activity; amounts on the order of TBq (terabecquerel) or GBq (gigabecquerel) are commonly used. Another unit of radioactivity is the curie, Ci, which was originally defined as the activity of one gram of pure radium, isotope Ra-226. At present it is equal, by definition, to the activity of any radionuclide decaying with a disintegration rate of 3.7 × 1010 Bq. The use of Ci is presently discouraged by the SI.
[edit] Sextant
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]]A sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Making this measurement is known as sighting the object, shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart. A common use of the sextant is to sight the sun at noon to find one's latitude. See celestial navigation for more discussion. Held horizontally, the sextant can be used to measure the angle between any two objects, such as between two lighthouses, which will, similarly, allow for calculation of a line of position on a chart.
The scale of a sextant has a length of ⅙ of a full circle (60°); hence the sextant's name (sextāns, -antis is the Latin word for "one sixth", "εξάντας" in Greek). An octant is a similar device with a shorter scale (⅛ of a circle, or 45°), whereas a quintant (⅕, or 72°) and a quadrant (¼, or 90°) have longer scales.
Sir Isaac Newton (1643-1727) invented the principle of the doubly reflecting navigation instrument (a reflecting quadrant - see Octant (instrument)), but never published it. Two men independently developed the octant around 1730: John Hadley (1682-1744), an English mathematician, and Thomas Godfrey (1704-1749), a glazier in Philadelphia. The octant and later the sextant, replaced the Davis quadrant as the main instrument for navigation.
[edit] Antikythera mechanism
The Antikythera mechanism is the oldest known complex scientific calculator. It contains many gears, and is sometimes called the first known analog computer although its flawless manufacturing suggests that it had a number of predecessors which have not yet been discovered.
It appears to be constructed upon theories of astronomy and mathematics developed by Greek astronomers and it is estimated that it was made around 150 to 100 BC. One hypothesis is that the device was constructed at an academy founded by the ancient Stoic philosopher Posidonius on the Greek island of Rhodes, which at the time was known as a centre of astronomy and mechanical engineering, and that perhaps the astronomer Hipparchus was the engineer who designed it since it contains a lunar mechanism which uses Hipparchus' theory for the motion of the Moon.
[edit] Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol (gasoline) engine or gas engine, which uses the Otto cycle, in which a fuel/air mixture is ignited by a spark plug.
It operates using the diesel cycle (named after Dr. Rudolph Diesel). Diesel engines have the highest thermal efficiency of any internal or external combustion engine, because of their compression ratio. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in submarines and ships. Use in locomotives, large trucks and electric generating plants followed later. In the 1930s, they slowly began to be used in a few automobiles. As of 2007, about 50 percent of all new car sales in Europe are diesel.
[edit] Blueprint
The blueprint process is essentially the cyanotype process developed by the British astronomer and photographer Sir John Herschel in 1842. The photosensitive compound, a solution of ferric ammonium citrate and potassium ferricyanide, is coated onto paper. Areas of the compound exposed to strong light are converted to insoluble blue ferric ferrocyanide, or Prussian blue. The soluble chemicals are washed off with water leaving a light-stable print.
[edit] Slide rule
The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for "scientific" functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.
Slide rules come in a diverse range of styles and generally appear in a linear or circular form with a standardized set of markings (scales) essential to performing mathematical computations. Slide rules manufactured for specialized fields such as aviation or finance typically feature additional scales that aid in calculations common to that field.
William Oughtred and others developed the slide rule in the 1600s based on the emerging work on logarithms by John Napier. Before the advent of the pocket calculator, it was the most commonly used calculation tool in science and engineering. The use of slide rules continued to grow through the 1950s and 1960s even as digital computing devices were being gradually introduced; but around 1974 the electronic scientific calculator made it largely obsolete and most suppliers exited the business.
[edit] Difference engine
The Difference Engine was an automatic, mechanical calculator designed to tabulate polynomial functions. Both logarithmic and trigonometric functions can be approximated by polynomials, so a difference engine can compute many useful sets of numbers.
In 1822, Charles Babbage proposed the use of such a machine in a paper to the Royal Astronomical Society on 14 June entitled "Note on the application of machinery to the computation of astronomical and mathematical tables". This machine used the decimal number system and was powered by cranking a handle. The British government initially financed the project, but withdrew funding when Babbage repeatedly asked for more money whilst making no apparent progress on building the machine. Babbage went on to design his much more general analytical engine but later produced an improved difference engine design (his "Difference Engine No. 2") between 1847 and 1849.
[edit] Caravel
A caravel is a small, highly maneuverable, two- or three-masted lateen-rigged ship, created by the Portuguese and used also by them and by the Spanish for long voyages of exploration from the 15th century
The caravel was developed in the Atlantic under the order of Henry the Navigator and became the preferred vessel for Portuguese explorers. Initially, the Portuguese used carracks to explore along the west African coast and into the Atlantic Ocean. The carrack (or nau) was the state of the art in late medieval shipbuilding. But these larger, full-rigged square-sailed ships could not always be sailed with the precision necessary for inshore surveying in unknown waters. The explorers soon came to prefer the caravel, as well as the barge (barca) or the balinger (barinel) of around 50 to 200 tons. Being smaller, the caravel could sail upriver in shallow coastal waters. With the lateen sails attached, it could go fast over shallow water and take deep wind, while with the square Atlantic-type sails attached, it was very fast. Its economy, speed, agility, and power made it esteemed as the best sailing vessel of its time. The exploration done with caravels made possible the spice trade of the Portuguese and the Spanish.
[edit] Pump
A pump is a device used to move matter, usually fluids, such as gases, liquids or slurries. A pump displaces a volume by physical or mechanical action. One common misconception about pumps is the thought that they create pressure. Pumps alone do not create pressure; they only displace fluid, causing a flow. Adding resistance to flow causes pressure. Pumps fall into two major groups: positive displacement pumps and rotodynamic pumps. Their names describe the method for moving a fluid.
[edit] Saturn V
The Saturn V (pronounced "Saturn Five") was a multistage liquid-fuel expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. In total NASA launched thirteen Saturn V rockets with no loss of payload. It remains the largest and most powerful launch vehicle ever brought to operational status from a height, weight and payload standpoint. The Soviet Energia, which flew two test missions in the late 1980s before being canceled, had slightly more takeoff thrust.
The largest and biggest production model of the Saturn family of rockets, the Saturn V was designed under the direction of Wernher von Braun at the Marshall Space Flight Center in Huntsville, Alabama, with Boeing, North American Aviation, Douglas Aircraft Company, and IBM as the lead contractors. Von Braun's design was based in part on his work on the "Aggregate" series of rockets, especially the A-10, A-11, and A12, in Germany during World War II. The three stages of the Saturn V were developed by various NASA contractors, but following a sequence of mergers and takeovers all of them are now owned by Boeing.
[edit] Aristotle
Aristotle (Greek: Ἀριστοτέλης, Aristotélēs) (384 BC – 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. He wrote on many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology and zoology.
Together with Plato and Socrates (Plato's teacher), Aristotle is one of the most important founding figures in Western philosophy. He was the first to create a comprehensive system of Western philosophy, encompassing morality and aesthetics, logic and science, politics and metaphysics. Aristotle's views on the physical sciences profoundly shaped medieval scholarship, and their influence extended well into the Renaissance, although they were ultimately replaced by Newtonian Physics. In the biological sciences, some of his observations were confirmed to be accurate only in the nineteenth century. His works contain the earliest known formal study of logic, which was incorporated in the late nineteenth century into modern formal logic. In metaphysics, Aristotelianism had a profound influence on philosophical and theological thinking in the Islamic and Jewish traditions in the Middle Ages, and it continues to influence Christian theology, especially Eastern Orthodox theology, and the scholastic tradition of the Catholic Church. All aspects of Aristotle's philosophy continue to be the object of active academic study today.
Though Aristotle wrote many elegant treatises and dialogues (Cicero described his literary style as "a river of gold"), it is thought that the majority of his writings are now lost and only about one-third of the original works have survived.
[edit] Philosophiæ Naturalis Principia Mathematica
The Philosophiæ Naturalis Principia Mathematica, which is Latin for "mathematical principles of natural philosophy", often Principia or Principia Mathematica for short, is a three-volume work by Isaac Newton first published on 5 July 1687. Newton also published two further editions, the second in 1713, and the third in 1726. The Principia contains the statement of Newton's laws of motion forming the foundation of classical mechanics, as well as his law of universal gravitation and a derivation of Kepler's laws for the motion of the planets (which were first obtained empirically). The Principia is "justly regarded as one of the most important works in the history of science."
In formulating his physical theories, Newton had developed a field of mathematics now known as calculus. However, the language of calculus as we know it was largely absent from the Principia. Instead, Newton cast the majority of his proofs in geometric form, although with many calculus-like arguments based on limits of vanishing small geometric quantities.
In a supplement to the Principia, entitled General Scholium, Newton expressed his famous Hypotheses non fingo ("I feign no hypotheses" or "I make no guesses").
[edit] Gregor Mendel
Gregor Johann Mendel (July 20, 1822 – January 6, 1884) was an Augustinian priest and scientist, and is often called the father of genetics for his study of the inheritance of certain traits in pea plants. Mendel showed that the inheritance of these traits follows particular laws, which were later named after him. The significance of Mendel's work was not recognized until the turn of the 20th century. Its rediscovery formed the foundation of the modern science of genetics.
Mendel was born into an ethnic German family in Heinzendorf bei Odrau, Austrian Silesia, Austrian Empire (now Hynčice, Czech Republic), and was baptized two days later. He was the son of Anton and Rosine Mendel, and had one older sister and one younger. They lived and worked on a farm which had been owned by the Mendel family for at least 130 years. During his childhood, Mendel worked as a gardener, studied beekeeping, and as a young man attended the Philosophical Institute in Olomouc in 1840–1843. Upon recommendation of his physics teacher Friedrich Franz, he entered the Augustinian Abbey of St Thomas in Brno in 1843. Born Johann Mendel, he took the name Gregor upon entering monastic life. In 1851 he was sent to the University of Vienna to study, returning to his abbey in 1853 as a teacher, principally of physics.
[edit] Roger Bacon
Roger Bacon, O.F.M. (c. 1214–1294), also known as Doctor Mirabilis (Latin: "wonderful teacher"), was an English philosopher and Franciscan friar who placed considerable emphasis on empiricism. He is sometimes credited as one of the earliest European advocates of the modern scientific method inspired by the works of Plato via early Islamic scientists.
Roger Bacon was born in Ilchester in Somerset, possibly in 1214. The only source for his date of birth is his statement in the Opus Tertium, written in 1267, that "forty years have passed since I first learned the alphabet". The 1214 birth date assumes he was not being literal, and meant 40 years had passed since he matriculated at Oxford at the age of 13. If he had been literal, his birth date was more likely to have been around 1220. In the same passage he reports that for all but two of those forty years he had always been engaged in study. His family appears to have been well-off, but, during the stormy reign of Henry III of England, their property was despoiled and several members of the family were driven into exile.
[edit] Barcode
A barcode (also bar code) is an optical machine-readable representation of data. Originally, bar codes represented data in the widths (lines) and the spacings of parallel lines, and may be referred to as linear or 1D (1 dimensional) barcodes or symbologies. They also come in patterns of squares, dots, hexagons and other geometric patterns within images termed 2D (2 dimensional) matrix codes or symbologies. Although 2D systems use symbols other than bars, they are generally referred to as barcodes as well. They are widely used in todays market.
The first use of barcodes was to label railroad cars, but they were not commercially successful until they were used to automate supermarket checkout systems, a task in which they have become almost universal. Their use has spread to many other roles as well, tasks that are generically referred to as Auto ID Data Capture (AIDC). Systems such as attempting to make inroads in the AIDC market, but the simplicity, universality and low cost of barcodes has limited the role of these other systems. It costs about US$0.005 to implement a barcode compared to passive RFID which still costs about US$0.07 to US$0.30 per tag.
Barcodes can be read by optical scanners called barcode readers, or scanned from an image by special software. In Japan, most mobile phones have built-in scanning software for 2D codes, and similar software is becoming available on smartphone platforms.
[edit] Pottery
Pottery is the ceramic ware made by potters. Major types of pottery include earthenware, stoneware, and porcelain. The places where such wares are made are called potteries. Pottery is one of the oldest human technologies and art-forms, and remains a major industry today. Ceramic art covers the art of pottery, whether in items made for use or purely for decoration.
Pottery is made by forming a clay body into objects of a required shape and heating them to high temperatures in a kiln to induce reactions that lead to permanent changes, including increasing their strength and hardening and setting their shape. There are wide regional variations in the properties of clays used by potters and this often helps to produce wares that are unique in character to a locality. It is common for clays and other minerals to be mixed to produce clay bodies suited to specific purpose.
[edit] Battleship
A battleship is a large, heavily armored warship with a main battery consisting of the largest calibre of guns. Battleships were larger, better armed, and better armored than cruisers and destroyers.
Battleship design continually evolved to incorporate and adapt technological advances to maintain an edge. The word battleship was coined around 1794 and is a shortened form of line-of-battle ship, the dominant wooden warship during the Age of Sail.[5] The term came into formal use in the late 1880s to describe a type of ironclad warship,[6] now referred to as pre-dreadnought battleships. In 1906, the launch of HMS Dreadnought heralded a revolution in battleship design. Following battleship designs that were influenced by the HMS Dreadnought were referred to as "dreadnoughts".
Battleships were a potent symbol of naval dominance and national might, and for decades the battleship was a major factor in both diplomacy and military strategy. The global arms race in battleship construction in the early 20th century was one of the causes of World War I, which saw a clash of huge battle fleets at the Battle of Jutland. The Naval Treaties of the 1920s and 1930s limited the number of battleships but did not end the evolution of design. Both the Allies and the Axis Powers deployed battleships of old construction and new during World War II.
[edit] Pantheon
The Pantheon (pronounced /pænˈθiː.ən/ or /ˈpænθi.ən/,Latin: Pantheon from Greek: Πάνθεον, meaning "Every god") is a building in Rome, originally built by Marcus Agrippa as a temple to all the gods of Ancient Rome, and rebuilt in the early 2nd century AD. The intended degree of inclusiveness of this dedication is debated. The generic term pantheon is now applied to a monument in which illustrious dead are buried. The building is circular with a portico of three ranks of huge granite Corinthian columns (eight in the first rank and two groups of four behind) under a pediment opening into the rotunda, under a coffered, concrete dome, with a central opening (oculus) open to the sky. The Pantheon is the oldest large-scale dome in Rome. The height to the oculus and the diameter of the interior circle are the same, 43.3 metres (142 ft). A rectangular structure links the portico with the rotunda. It is one of the best preserved of all Roman buildings. It has been in continuous use throughout its history. Since the 7th century, the Pantheon has been used as a Roman Catholic church dedicated to "St. Mary and the Martyrs" but informally known as "Santa Maria Rotonda."
[edit] Jacquard loom
The Jacquard Loom is a mechanical loom, invented by Joseph Marie Jacquard in 1801, that simplifies the process of manufacturing textiles with complex patterns such as brocade, damask, and matelasse. The loom is controlled by punchcards with punched holes, each row of which corresponds to one row of the design. Multiple rows of holes are punched on each card and the many cards that compose the design of the textile are strung together in order. It is based on earlier inventions by the Frenchmen Basile Bouchon (1725), Jean Falcon (1728) and Jacques Vaucanson.
Each hole in the card corresponds to a "Bolus" hook, which can either be up or down. The hook raises or lowers the harness, which carries and guides the warp thread so that the weft will either lie above or below it. The sequence of raised and lowered threads is what creates the pattern. Each hook can be connected via the harness to a number of threads, allowing more than one repeat of a pattern. A loom with a 400 hook head might have four threads connected to each hook, resulting in a fabric that is 1600 warp ends wide with four repeats of the weave going across.
[edit] Corrective lens
A corrective lens is a lens worn in front of the eye, mainly used to treat myopia, hyperopia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye. Intraocular lenses are surgically implanted most commonly after cataract removal, but recently for purely refractive purposes. Myopia (near sightedness) requires a divergent lens, whereas hyperopia (far sightedness) requires convergent lens.
Corrective lenses are typically prescribed by an optometrist. The prescription consists of all the specifications necessary to make the lens. Prescriptions typically include the power specifications of each lens (for each eye). Strengths are generally prescribed in quarter-diopter steps (0.25 D) because most people cannot generally distinguish between smaller increments (ex. eighth-diopter steps / 0.125 D). The formula for calculating dioptres of a lens is given by,P=1/f (where P is power in dioptres and f is focal length of the lens).
[edit] Stirrup
The stirrup is a ring with a flat bottom fixed on a leather strap, usually hung from each side of a saddle by an adjustable strap to create a footrest for a person using a riding animal (usually a horse or other equine, such as a mule), used as a support for the foot of a rider when seated in the saddle and as an aid in mounting. It greatly increases the rider's ability to stay in the saddle and control the mount, increasing the animal's usefulness in communication, transportation and warfare. It is considered one of the basic tools used to create and spread modern civilization. Some argue it is as important as the wheel or printing press.
The stirrup, which gave greater stability to a rider, has been described as one of the most significant inventions in the history of warfare, prior to gunpowder. As a tool allowing expanded use of horses in warfare, the stirrup is often called the third revolutionary step in equipment, after the chariot and the saddle. The basic tactics of mounted warfare were significantly altered by the stirrup. A rider supported by stirrups was less likely to fall off while fighting, and could deliver a blow with a weapon that more fully employed the weight and momentum of horse and rider.
[edit] Ballpoint pen
A ballpoint pen (also eponymously known in British English and Australian English as a biro and 
/ˈbaɪroʊ/ bye-roe in Britain and Australia but sometimes /ˈbiːroʊ/ bee-roh" elsewhere, named after its credited, though contested, inventor László Bíró), is a modern writing instrument. A ballpoint pen has an internal chamber filled with a viscous ink that is dispensed at the tip during use by the rolling action of a small metal sphere (0.7 mm to 1.2 mm in diameter) of brass, steel or tungsten carbide The ink dries almost immediately after contact with paper. Inexpensive, reliable and maintenance-free, the ballpoint has replaced the fountain pen as the most popular tool for everyday writing.
The manufacture of economical, reliable ballpoint pens resulted from a combination of experimentation, modern chemistry, and the precision manufacturing capabilities of 20th century technology. Many patents worldwide are testaments to failed attempts to make these pens commercially viable and widely available. The ballpoint pen went through several failures in design throughout its early.
[edit] Nail (fastener)
In Engineering, Woodworking and Construction, a nail is a pin-shaped, sharp object of hard metal or alloy, formerly wrought iron, though today a modern alloy of steel is common, used as a strong fastener. Nails for specialized purposes may often be dipped or coated to prevent corrosion in harsh conditions like weather or chemically treated wood. Whereas, a Stainless Steel alloy, Brass (Copper & Tin), or Aluminum, are often reserved for the art of fine craft where the nail is the elegant accent of the art-piece presented. Galvanized (Zinc coated), is made of particular mention here however; due arbitrarily to its common use, very low cost, diverse plating affinity, and notably wide range of corrosion resistance to harsh environments.
Nails are typically driven into the workpiece by a hammer or by a nail gun driven by compressed air or a small explosive charge or primer. A nail holds materials together by friction in the axial direction and shear strength in lateral directions. The point of the nail is also sometimes bent over or clinched to prevent it from pulling out.
[edit] Cavitation
Cavitation is the formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure. Cavitation is usually divided into two classes of behavior: inertial (or transient) cavitation, and noninertial cavitation. Inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave. Such cavitation often occurs in pumps, propellers, impellers, and in the vascular tissues of plants. Noninertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers, etc.
Inertial cavitation was first studied by Lord Rayleigh in the late 19th century, when he considered the collapse of a spherical void within a liquid. When a volume of liquid is subjected to a sufficiently low pressure, it may rupture and form a cavity. This phenomenon is termed cavitation inception and may occur behind the blade of a rapidly rotating propeller or on any surface vibrating underwater with sufficient amplitude and acceleration. A fast-flowing river can cause cavitation on rock surfaces, particularly when there is a drop-off, such as on a waterfall.
[edit] Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an ore body, vein or (coal) seam. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock salt and potash. Any material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory, is usually mined. Mining in a wider sense comprises extraction of any non-renewable resource (e.g., petroleum, natural gas, or even water).
Mining of stone and metal has been done since pre-historic times. Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials and finally reclamation of the land to prepare it for other uses once the mine is closed. The nature of mining processes creates a potential negative impact on the environment both during the mining operations and for years after the mine is closed. This impact has led to most of the world's nations adopting regulations to moderate the negative effects of mining operations. Safety has long been a concern as well, though modern practices have improved safety in mines significantly. Mining today is able to profitably and safely recover minerals with little negative impact to the environment.
Since the beginning of civilization people have used stone, ceramics and, later, metals found on or close to the Earth's surface. These were used to manufacture early tools and weapons, for example, high quality flint found in northern France and southern England were used to create flint tools. Flint mines have been found in chalk areas where seams of the stone were followed underground by shafts and galleries. The mines at Grimes Graves are especially famous, and like most other flint mines, are Neolithic in origin (ca 4000 BC-ca 3000 BC). Other hard rocks mined or collected for axes included the greenstone of the Langdale axe industry based in the English Lake District.
[edit] Vacuum tube
In electronics, a vacuum tube, electron tube (in North America), thermionic valve, or valve (elsewhere, especially in Britain) is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space. Some special function vacuum tubes are filled with low-pressure gas: these are so-called soft valves (or tubes), as distinct from the hard vacuum type which have the internal gas pressure reduced as far as possible. Almost all depend on the thermal emission of electrons, hence thermionic.
Vacuum tubes were critical to the development of electronic technology, which drove the expansion and commercialization of radio broadcasting, television, radar, sound reproduction, large telephone networks, analog and digital computers, and industrial process control. Some of these applications pre-dated electronics, but it was the vacuum tube that made them widespread and practical.
For most purposes, the vacuum tube has been replaced by solid-state devices such as transistors and solid-state diodes. Solid-state devices last much longer, are smaller, more efficient, more reliable, and cheaper than equivalent vacuum tube devices. However, tubes are still used in specialized applications: for engineering reasons, as in high-power radio frequency transmitters; or for their aesthetic appeal and distinct sound signature, as in audio amplification. Cathode ray tubes are still used as display devices in television sets, video monitors, and oscilloscopes, although they are being replaced by LCDs and other flat-panel displays. A specialized form of the electron tube, the magnetron, is the source of microwave energy in microwave ovens and some radar systems. The klystron, a powerful but narrow-band radio-frequency amplifier, is commonly deployed by broadcasters as a high-power UHF television transmitter. It was also used in first generation computers (1949-1955).
[edit] Integrated circuit
In electronics, an integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a thin substrate of semiconductor material. Integrated circuits are used in almost all electronic equipment in use today and have revolutionized the world of electronics.
Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.
There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed one transistor at a time. Furthermore, much less material is used to construct a circuit as a packaged IC die than as a discrete circuit. Performance is high since the components switch quickly and consume little power (compared to their discrete counterparts) because the components are small and close together. As of 2006, chip areas range from a few square millimeters to around 350 mm2, with up to 1 million transistors per mm2.
[edit] Heat exchanger
A heat exchanger is a device built for efficient heat transfer from one medium to another, whether the media are separated by a solid wall so that they never mix, or the media are in direct contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, and natural gas processing. One common example of a heat exchanger is the radiator in a car, in which the heat source, being a hot engine-cooling fluid, water, transfers heat to air flowing through the radiator [i.e. the heat transfer medium].
Heat exchangers may be classified according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient, in that it can transfer the most heat from the heat (transfer) medium. See countercurrent exchange. In a cross-flow heat exchanger, the fluids travel roughly perpendicular to one another through the exchanger.
For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger. The exchanger's performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence.
[edit] Hipparchus
Hipparchus was born in Nicaea (now Iznik, Turkey), and probably died on the island of Rhodes. He is known to have been a working astronomer at least from 147 BC to 127 BC. Hipparchus is considered the greatest ancient astronomical observer and, by some, the greatest overall astronomer of antiquity. He was the first whose quantitative and accurate models for the motion of the Sun and Moon survive. For this he certainly made use of the observations and perhaps the mathematical techniques accumulated over centuries by the Chaldeans from Babylonia. He developed trigonometry and constructed trigonometric tables, and he has solved several problems of spherical trigonometry. With his solar and lunar theories and his trigonometry, he may have been the first to develop a reliable method to predict solar eclipses. His other reputed achievements include the discovery of precession, the compilation of the first comprehensive star catalog of the western world, and possibly the invention of the astrolabe, also of the armillary sphere which first appeared during his century and was used by him during the creation of much of the star catalogue. It would be three centuries before Claudius Ptolemaeus' synthesis of astronomy would supersede the work of Hipparchus; it is heavily dependent on it in many areas.
[edit] Logarithm
In mathematics, the logarithm of a number to a given base is the power or exponent to which the base must be raised in order to produce the number.
For example, the logarithm of 1000 to the base 10 is 3, because 3 is how many 10s you must multiply to get 1000: thus 10 × 10 × 10 = 1000; the base 2 logarithm of 32 is 5 because 5 is how many 2s one must multiply to get 32: thus 2 × 2 × 2 × 2 × 2 = 32. In the language of exponents: 103 = 1000, so log101000 = 3, and 25 = 32, so log232 = 5.
The logarithm of x to the base b is written logb(x) or, if the base is implicit, as log(x). So, for a number x, a base b and an exponent y,
An important feature of logarithms is that they reduce multiplication to addition, by the formula:
That is, the logarithm of the product of two numbers is the sum of the logarithms of those numbers. The use of logarithms to facilitate complicated calculations was a significant motivation in their original development.
[edit] Operational amplifier
An operational amplifier, which is often called an op-amp, is a DC-coupled high-gain electronic voltage amplifier with differential inputs and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of its output voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation. High input impedance at the input terminals (ideally infinite) and low output impedance (ideally zero) are important typical characteristics.
Op-amps are among the most widely used analog electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid operational amplifiers with special performance specifications may cost over $100 US in small quantities.
Modern designs are electronically more rugged than earlier implementations and some can sustain direct short circuits on their outputs without damage.
The op-amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op-amp, but with 2 outputs), the instrumentation amplifier (usually built from 3 op-amps), the isolation amplifier (similar to the instrumentation amplifier, but which works fine with common-mode voltages that would destroy an ordinary op-amp), and negative feedback amplifier (usually built from 1 or more op-amps and a resistive feedback network).
[edit] Barbed wire
Barbed wire, also known as barb wireor bobbed, is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand(s). It is used to construct inexpensive fences and is used atop walls surrounding secured property. It is also a major feature of the fortifications in trench warfare (as a wire obstacle).
A person or animal trying to pass through or over barbed wire will suffer discomfort and possibly injury. Barbed wire fencing requires only fence posts, wire and fixing devices such as staples. It is simple to construct and quick to erect by an unskilled person.
It was first conceived in 1865 by Louis Jannin as fil de fer barbelé, French for "barbed iron wire". The first patent in the United States was issued in 1867 to Lucien B. Smith of Kent, Ohio, who is regarded as the inventor. Joseph F. Glidden of DeKalb, Illinois received a patent for the modern invention in 1874 after he made his own modifications to previous versions.
Barbed wire was the first wire technology capable of restraining cattle. Wire fences were cheaper and easier to erect than their alternatives (such as the planting of Osage orange, a thorny bush which was time-consuming to transplant and grow. The Osage orange later became a suplier of the wood used in making barbed wire fence posts and when they became widely available in the United States in the late 19th century they made it affordable to fence much larger areas than before. They made intensive animal husbandry practical on a much larger scale.
[edit] Plough
The plough (American spelling: plow; both /plaʊ/) is a tool used in farming for initial cultivation of soil in preparation for sowing seed or planting. It has been a basic instrument for most of recorded history, and represents one of the major advances in agriculture. The primary purpose of ploughing is to turn over the upper layer of the soil, bringing fresh nutrients to the surface, while burying weeds and the remains of previous crops, allowing them to break down. It also aerates the soil, and allows it to hold moisture better. In modern use, a ploughed field is typically left to dry out, and is then harrowed before planting.
Ploughs were initially pulled by oxen, and later in many areas by horses. In industrialised countries, the first mechanical means of pulling a plough used steam-power (ploughing engines or steam tractors), but these were gradually superseded by internal-combustion-powered tractors. In the past two decades plough use has reduced in some areas (where soil damage and erosion are problems), in favour of shallower ploughing and other less invasive tillage techniques.
Ploughs are even used under the sea, for the laying of cables, as well as preparing the earth for side-scan sonar in a process used in oil exploration.
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