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100-586: Yablochkov graduated in 1866 as a military engineer from Nikolayev Engineering Institute, now Military Engineering-Technical University (Russian Военный инженерно-технический университет ), and in 1869 from Technical Galvanic School in Saint Petersburg . After serving in the army , Yablochkov settled in Moscow in 1873, where he was appointed Head of Telegraph Office at the Moscow- Kursk railroad. He opened up

200-404: A "pulse theory" and compared the spreading of light to that of waves in water in his 1665 work Micrographia ("Observation IX"). In 1672 Hooke suggested that light's vibrations could be perpendicular to the direction of propagation. Christiaan Huygens (1629–1695) worked out a mathematical wave theory of light in 1678 and published it in his Treatise on Light in 1690. He proposed that light

300-609: A better representation of how "bright" a light appears to be than raw intensity. They relate to raw power by a quantity called luminous efficacy and are used for purposes like determining how to best achieve sufficient illumination for various tasks in indoor and outdoor settings. The illumination measured by a photocell sensor does not necessarily correspond to what is perceived by the human eye and without filters which may be costly, photocells and charge-coupled devices (CCD) tend to respond to some infrared , ultraviolet or both. Light exerts physical pressure on objects in its path,

400-521: A better system of training for siege operations was required. On 23 April 1812 an establishment was authorised, by Royal Warrant, to teach "Sapping, Mining, and other Military Fieldworks" to the junior officers of the Corps of Royal Engineers and the Corps of Royal Military Artificers, Sappers and Miners. The first courses at the Royal Engineers Establishment were done on an all ranks basis with

500-553: A body could be so massive that light could not escape from it. In other words, it would become what is now called a black hole . Laplace withdrew his suggestion later, after a wave theory of light became firmly established as the model for light (as has been explained, neither a particle or wave theory is fully correct). A translation of Newton's essay on light appears in The large scale structure of space-time , by Stephen Hawking and George F. R. Ellis . The fact that light could be polarized

600-476: A dedicated force of military engineering specialists were the Romans, whose army contained a dedicated corps of military engineers known as architecti . This group was pre-eminent among its contemporaries. The scale of certain military engineering feats, such as the construction of a double-wall of fortifications 30 miles (48 km) long, in just 6 weeks to completely encircle the besieged city of Alesia in 52 B.C.E.,

700-467: A force of about 3.3 piconewtons on the object being illuminated; thus, one could lift a U.S. penny with laser pointers, but doing so would require about 30 billion 1-mW laser pointers.   However, in nanometre -scale applications such as nanoelectromechanical systems (NEMS), the effect of light pressure is more significant and exploiting light pressure to drive NEMS mechanisms and to flip nanometre-scale physical switches in integrated circuits

800-613: A galvanic cell with alkaline electrolyte , and created a regenerative cell (the so-called autoaccumulator). Yablochkov participated in Electrical engineering exhibitions in Russia (1880 and 1882), Paris (1881 and 1889), and First International Congress of Electricians (1881). For participation in the exhibition and congress, he was awarded the French Order of the Legion of Honor . Yablochkov

900-478: A given volume in a short duration. Specific military engineering occupations also extend to the field of explosives and demolitions and their usage on the battlefield. Explosive devices have been used on the battlefield for several centuries, in numerous operations from combat to area clearance. Earliest known development of explosives can be traced back to 10th-century China where the Chinese are credited with engineering

1000-411: A lasting molecular change (a change in conformation) in the visual molecule retinal in the human retina, which change triggers the sensation of vision. There exist animals that are sensitive to various types of infrared, but not by means of quantum-absorption. Infrared sensing in snakes depends on a kind of natural thermal imaging , in which tiny packets of cellular water are raised in temperature by

1100-450: A medium faster than the speed of light in that medium can produce visible Cherenkov radiation . Certain chemicals produce visible radiation by chemoluminescence . In living things, this process is called bioluminescence . For example, fireflies produce light by this means and boats moving through water can disturb plankton which produce a glowing wake. Certain substances produce light when they are illuminated by more energetic radiation,

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1200-400: A method of employing Michael Faraday 's discovery of induction to create a continuous current of higher voltage, where primary windings were connected to a source of alternating current and secondary windings could be connected to several electric "candles". Although it was not recognized at the time, Yablochkov's idea of using transformers to provide different voltages from the same AC line

1300-424: A phenomenon which can be deduced by Maxwell's equations , but can be more easily explained by the particle nature of light: photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by c , the speed of light.   Due to the magnitude of c , the effect of light pressure is negligible for everyday objects.   For example, a one-milliwatt laser pointer exerts

1400-539: A popular spectacle for the local people by 1843, when 43,000 came to watch a field day laid on to test a method of assaulting earthworks for a report to the Inspector General of Fortifications. In 1869 the title of the Royal Engineers Establishment was changed to "The School of Military Engineering" (SME) as evidence of its status, not only as the font of engineer doctrine and training for the British Army , but also as

1500-419: A process known as fluorescence . Some substances emit light slowly after excitation by more energetic radiation. This is known as phosphorescence . Phosphorescent materials can also be excited by bombarding them with subatomic particles. Cathodoluminescence is one example. This mechanism is used in cathode-ray tube television sets and computer monitors . Certain other mechanisms can produce light: When

1600-606: A separate Gramme generator. Beginning in 1880, the Paris Hippodrome's 20 Serrin lights powered by 20 generators were replaced by 68 additional Yablochkov candles, based on two years of positive experience with 60 candles powered by just three generators. The impact of the 1878 Paris demonstration was a depression in the value of gas company shares which did not recover until 1880. French, English , and American businessmen quickly set up companies licensing Yablochkov's patents. As part of his arc lighting patents, Yablochkov described

1700-410: A source. One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, while light travelled only in straight lines. He did, however, explain the phenomenon of the diffraction of light (which had been observed by Francesco Grimaldi ) by allowing that a light particle could create a localised wave in the aether . Newton's theory could be used to predict

1800-414: A surface between one transparent material and another. It is described by Snell's Law : where θ 1 is the angle between the ray and the surface normal in the first medium, θ 2 is the angle between the ray and the surface normal in the second medium and n 1 and n 2 are the indices of refraction , n = 1 in a vacuum and n > 1 in a transparent substance . When a beam of light crosses

1900-401: A technical discipline, the term civil engineering entered the lexicon as a way to distinguish between those specializing in the construction of such non-military projects and those involved in the older discipline. As the prevalence of civil engineering outstripped engineering in a military context and the number of disciplines expanded, the original military meaning of the word "engineering"

2000-551: A value of 298 000 000  m/s in 1862. Albert A. Michelson conducted experiments on the speed of light from 1877 until his death in 1931. He refined Foucault's methods in 1926 using improved rotating mirrors to measure the time it took light to make a round trip from Mount Wilson to Mount San Antonio in California. The precise measurements yielded a speed of 299 796 000  m/s . The effective velocity of light in various transparent substances containing ordinary matter ,

2100-406: A whole, including military engineering functions such as engineer support to force protection, counter-improvised explosive devices, environmental protection, engineer intelligence and military search. Military engineering does not encompass the activities undertaken by those 'engineers' who maintain, repair and operate vehicles, vessels, aircraft, weapon systems and equipment." Military engineering

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2200-409: A workshop for his experiments in electrical engineering, which laid down the foundations for his future inventions in the field of electric lighting , electric machines, galvanic cells and accumulators . Yablochkov’s major invention was the first model of an arc lamp that eliminated the mechanical complexity of competing lights that required a regulator to manage the voltaic arc. He went to Paris

2300-494: Is electromagnetic radiation that can be perceived by the human eye . Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz . The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively optical radiation . In physics ,

2400-527: Is also affected by the colour spectrum of light, a process known as photomorphogenesis . The speed of light in vacuum is defined to be exactly 299 792 458  m/s (approximately 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum. Different physicists have attempted to measure

2500-594: Is an academic subject taught in military academies or schools of military engineering . The construction and demolition tasks related to military engineering are usually performed by military engineers including soldiers trained as sappers or pioneers . In modern armies, soldiers trained to perform such tasks while well forward in battle and under fire are often called combat engineers . In some countries, military engineers may also perform non-military construction tasks in peacetime such as flood control and river navigation works, but such activities do not fall within

2600-454: Is an active area of research. At larger scales, light pressure can cause asteroids to spin faster, acting on their irregular shapes as on the vanes of a windmill .   The possibility of making solar sails that would accelerate spaceships in space is also under investigation. Although the motion of the Crookes radiometer was originally attributed to light pressure, this interpretation

2700-599: Is an example. Such military engineering feats would have been completely new, and probably bewildering and demoralizing, to the Gallic defenders. Vitruvius is the best known of these Roman army engineers, due to his writings surviving. Examples of battles before the early modern period where military engineers played a decisive role include the Siege of Tyre under Alexander the Great , the Siege of Masada by Lucius Flavius Silva as well as

2800-429: Is caused by the surface roughness of the reflecting surfaces, and internal scatterance is caused by the difference of refractive index between the particles and medium inside the object. Like transparent objects, translucent objects allow light to transmit through, but translucent objects also scatter certain wavelength of light via internal scatterance. Refraction is the bending of light rays when passing through

2900-470: Is classified by wavelength into radio waves , microwaves , infrared , the visible spectrum that we perceive as light, ultraviolet , X-rays and gamma rays . The designation " radiation " excludes static electric , magnetic and near fields . The behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths and lower frequencies have longer wavelengths. When EMR interacts with single atoms and molecules, its behavior depends on

3000-412: Is commonly listed under the role of combat engineers who demolitions expertise also includes mine and IED detection and disposal. For more information, see Bomb disposal . Military engineers are key in all armed forces of the world, and invariably found either closely integrated into the force structure, or even into the combat units of the national troops. Brazilian Army engineers can be part of

3100-457: Is incorrect; the characteristic Crookes rotation is the result of a partial vacuum. This should not be confused with the Nichols radiometer , in which the (slight) motion caused by torque (though not enough for full rotation against friction) is directly caused by light pressure. As a consequence of light pressure, Einstein in 1909 predicted the existence of "radiation friction" which would oppose

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3200-641: Is less than in vacuum. For example, the speed of light in water is about 3/4 of that in vacuum. Two independent teams of physicists were said to bring light to a "complete standstill" by passing it through a Bose–Einstein condensate of the element rubidium , one team at Harvard University and the Rowland Institute for Science in Cambridge, Massachusetts and the other at the Harvard–Smithsonian Center for Astrophysics , also in Cambridge. However,

3300-635: Is now largely obsolete. In its place, the term "military engineering" has come to be used. In ancient times, military engineers were responsible for siege warfare and building field fortifications , temporary camps and roads. The most notable engineers of ancient times were the Romans and Chinese , who constructed huge siege-machines (catapults, battering rams and siege towers ). The Romans were responsible for constructing fortified wooden camps and paved roads for their legions . Many of these Roman roads are still in use today. The first civilization to have

3400-449: Is regarded as the start of modern physical optics. Pierre Gassendi (1592–1655), an atomist, proposed a particle theory of light which was published posthumously in the 1660s. Isaac Newton studied Gassendi's work at an early age and preferred his view to Descartes's theory of the plenum . He stated in his Hypothesis of Light of 1675 that light was composed of corpuscles (particles of matter) which were emitted in all directions from

3500-499: The Académie des Sciences in 1817. Siméon Denis Poisson added to Fresnel's mathematical work to produce a convincing argument in favor of the wave theory, helping to overturn Newton's corpuscular theory. By the year 1821, Fresnel was able to show via mathematical methods that polarization could be explained by the wave theory of light if and only if light was entirely transverse, with no longitudinal vibration whatsoever. The weakness of

3600-612: The Battle of the Trench under the suggestion of Salman the Persian to dig a trench. For about 600 years after the fall of the Roman empire , the practice of military engineering barely evolved in the west. In fact, much of the classic techniques and practices of Roman military engineering were lost. Through this period, the foot soldier (who was pivotal to much of the Roman military engineering capability)

3700-513: The Brazilian Air Force is occupied by engineers professionalized by Centro de Instrução e Adaptação da Aeronáutica (CIAAR) (Air Force Instruction and Adaptation Center) and trained, or specialized, by Instituto Tecnológico de Aeronáutica (ITA) (Aeronautics Institute of Technology). The Royal School of Military Engineering is the main training establishment for the British Army 's Royal Engineers . The RSME also provides training for

3800-481: The British Army in the conduct of siege operations and bridging. During this war low-ranking Royal Engineers officers carried out large-scale operations. They had under their command working parties of two or three battalions of infantry, two or three thousand men, who knew nothing in the art of siegeworks. Royal Engineers officers had to demonstrate the simplest tasks to the soldiers, often while under enemy fire. Several officers were lost and could not be replaced, and

3900-555: The Churchill AVRE . These and other dedicated assault vehicles were organised into the specialised 79th Armoured Division and deployed during Operation Overlord – 'D-Day'. Other significant military engineering projects of World War II include Mulberry harbour and Operation Pluto . Modern military engineering still retains the Roman role of building field fortifications , road paving and breaching terrain obstacles. A notable military engineering task was, for example, breaching

4000-480: The Magasins du Louvre which was lit by six Yablochkov candles . By 1880, the system had grown in size to 120 lamps with 84 lit at a time powered by a 100-horsepower steam engine and had been operating every night for two and one half years. The Paris Exposition of 1878 presented Yablochkov with the unique opportunity to make a spectacular demonstration for a world audience, and through the promotional efforts of Gramme

4100-746: The Royal Navy , Royal Air Force , other Arms and Services of the British Army , Other Government Departments, and Foreign and Commonwealth countries as required. These skills provide vital components in the Army's operational capability, and Royal Engineers are currently deployed in Afghanistan , Iraq , Cyprus , Bosnia , Kosovo , Kenya , Brunei , Falklands , Belize , Germany and Northern Ireland . Royal Engineers also take part in exercises in Saudi Arabia , Kuwait , Italy, Egypt , Jordan , Canada, Poland and

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4200-510: The Suez Canal during the Yom Kippur War . Military engineers can come from a variety of engineering programs. They may be graduates of mechanical , electrical , civil , or industrial engineering . Modern military engineering can be divided into three main tasks or fields: combat engineering, strategic support, and ancillary support. Combat engineering is associated with engineering on

4300-428: The aurora borealis offer many clues as to the nature of light. A transparent object allows light to transmit or pass through. Conversely, an opaque object does not allow light to transmit through and instead reflecting or absorbing the light it receives. Most objects do not reflect or transmit light specularly and to some degree scatters the incoming light, which is called glossiness . Surface scatterance

4400-574: The quanta of electromagnetic field, and can be analyzed as both waves and particles . The study of light, known as optics , is an important research area in modern physics . The main source of natural light on Earth is the Sun . Historically, another important source of light for humans has been fire , from ancient campfires to modern kerosene lamps . With the development of electric lights and power systems , electric lighting has effectively replaced firelight. Generally, electromagnetic radiation (EMR)

4500-431: The reflection of light, but could only explain refraction by incorrectly assuming that light accelerated upon entering a denser medium because the gravitational pull was greater. Newton published the final version of his theory in his Opticks of 1704. His reputation helped the particle theory of light to hold sway during the eighteenth century. The particle theory of light led Pierre-Simon Laplace to argue that

4600-615: The refraction of light in his book Optics . In ancient India , the Hindu schools of Samkhya and Vaisheshika , from around the early centuries AD developed theories on light. According to the Samkhya school, light is one of the five fundamental "subtle" elements ( tanmatra ) out of which emerge the gross elements. The atomicity of these elements is not specifically mentioned and it appears that they were actually taken to be continuous. The Vishnu Purana refers to sunlight as "the seven rays of

4700-479: The 14th-century development of gunpowder , new siege engines in the form of cannons appeared. Initially military engineers were responsible for maintaining and operating these new weapons just as had been the case with previous siege engines. In England, the challenge of managing the new technology resulted in the creation of the Office of Ordnance around 1370 in order to administer the cannons, armaments and castles of

4800-409: The 20th and 21st centuries, military engineering also includes CBRN defense and other engineering disciplines such as mechanical and electrical engineering techniques. According to NATO , "military engineering is that engineer activity undertaken, regardless of component or service, to shape the physical operating environment. Military engineering incorporates support to maneuver and to the force as

4900-712: The Quadro Complementar de Oficiais da Armada and the Quadro Complementar de Oficiais Fuzileiros Navais. Officers can come from the Centro de Instrução Almirante Wandenkolk (CIAW) (Admiral Wandenkolk Instruction Center) and the Escola Naval (EN) (Naval School) which, through internal selection of the Navy, finish their graduation at the Universidade de São Paulo (USP) (University of São Paulo) . The Quadro de Oficias Engenheiros of

5000-655: The Quadro de Engenheiros Militares, with its members trained or professionalized by the traditional Instituto Militar de Engenharia (IME) (Military Institute of Engineering) , or the Arma de Engenharia, with its members trained by the Academia Militar das Agulhas Negras (AMAN) (Agulhas Negras Military Academy). In the Brazil's Navy , engineers can occupy the Corpo de Engenheiros da Marinha,

5100-463: The United States' history of warfare. The Army originally claimed engineers exclusively, but as the U.S. military branches expanded to the sea and sky, the need for military engineering sects in all branches increased. As each branch of the United States military expanded, technology adapted to fit their respective needs. Light#Light sources Light , visible light , or visible radiation

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5200-646: The United States. The prevalence of military engineering in the United States dates back to the American Revolutionary War when engineers would carry out tasks in the U.S. Army. During the war, they would map terrain to and build fortifications to protect troops from opposing forces. The first military engineering organization in the United States was the Army Corps of Engineers. Engineers were responsible for protecting military troops whether using fortifications or designing new technology and weaponry throughout

5300-502: The ability of defenders to bring fire onto attacking enemies. Fort construction proliferated in 16th-century Europe based on the trace italienne design. By the 18th century, regiments of foot (infantry) in the British, French, Prussian and other armies included pioneer detachments. In peacetime these specialists constituted the regimental tradesmen, constructing and repairing buildings, transport wagons, etc. On active service they moved at

5400-456: The amount of energy per quantum it carries. EMR in the visible light region consists of quanta (called photons ) that are at the lower end of the energies that are capable of causing electronic excitation within molecules, which leads to changes in the bonding or chemistry of the molecule. At the lower end of the visible light spectrum, EMR becomes invisible to humans (infrared) because its photons no longer have enough individual energy to cause

5500-470: The apparent size of images. Magnifying glasses , spectacles , contact lenses , microscopes and refracting telescopes are all examples of this manipulation. There are many sources of light. A body at a given temperature emits a characteristic spectrum of black-body radiation . A simple thermal source is sunlight , the radiation emitted by the chromosphere of the Sun at around 6,000  K (5,730  °C ; 10,340  °F ). Solar radiation peaks in

5600-554: The attack on Fort Eben-Emael in Belgium was conducted by Luftwaffe glider -deployed combat engineers. The need to defeat the German defensive positions of the " Atlantic wall " as part of the amphibious landings in Normandy in 1944 led to the development of specialist combat engineer vehicles. These, collectively known as Hobart's Funnies , included a specific vehicle to carry combat engineers,

5700-438: The battlefield. Combat engineers are responsible for increasing mobility on the front lines of war such as digging trenches and building temporary facilities in war zones. Strategic support is associated with providing service in communication zones such as the construction of airfields and the improvement and upgrade of ports, roads and railways communication. Ancillary support includes provision and distribution of maps as well as

5800-600: The beam from the eye travels infinitely fast this is not a problem. In 55 BC, Lucretius , a Roman who carried on the ideas of earlier Greek atomists , wrote that "The light & heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove." (from On the nature of the Universe ). Despite being similar to later particle theories, Lucretius's views were not generally accepted. Ptolemy (c. second century) wrote about

5900-452: The boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as refraction . The refractive quality of lenses is frequently used to manipulate light in order to change

6000-592: The concept of light is intended to include very-high-energy photons (gamma rays), additional generation mechanisms include: Light is measured with two main alternative sets of units: radiometry consists of measurements of light power at all wavelengths, while photometry measures light with wavelength weighted with respect to a standardized model of human brightness perception. Photometry is useful, for example, to quantify Illumination (lighting) intended for human use. The photometry units are different from most systems of physical units in that they take into account how

6100-495: The diameter of Earth's orbit. However, its size was not known at that time. If Rømer had known the diameter of the Earth's orbit, he would have calculated a speed of 227 000 000  m/s . Another more accurate measurement of the speed of light was performed in Europe by Hippolyte Fizeau in 1849. Fizeau directed a beam of light at a mirror several kilometers away. A rotating cog wheel

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6200-525: The director of the Establishment, was keen to confirm his teaching, and regular exercises were held as demonstrations or as experiments to improve the techniques and teaching of the Establishment. From 1833 bridging skills were demonstrated annually by the building of a pontoon bridge across the Medway which was tested by the infantry of the garrison and the cavalry from Maidstone . These demonstrations had become

6300-448: The disposal of unexploded warheads. Military engineers construct bases, airfields, roads, bridges, ports, and hospitals. During peacetime before modern warfare, military engineers took the role of civil engineers by participating in the construction of civil-works projects. Nowadays, military engineers are almost entirely engaged in war logistics and preparedness. Explosives are defined as any system that produces rapidly expanding gases in

6400-796: The end of World War I , the standoff on the Western Front caused the Imperial German Army to gather experienced and particularly skilled soldiers to form "Assault Teams" which would break through the Allied trenches. With enhanced training and special weapons (such as flamethrowers ), these squads achieved some success, but too late to change the outcome of the war. In early WWII, however, the Wehrmacht "Pioniere" battalions proved their efficiency in both attack and defense, somewhat inspiring other armies to develop their own combat engineers battalions. Notably,

6500-493: The eye. Another supporter of the wave theory was Leonhard Euler . He argued in Nova theoria lucis et colorum (1746) that diffraction could more easily be explained by a wave theory. In 1816 André-Marie Ampère gave Augustin-Jean Fresnel an idea that the polarization of light can be explained by the wave theory if light were a transverse wave . Later, Fresnel independently worked out his own wave theory of light and presented it to

6600-434: The eyes and rays from a source such as the sun. In about 300 BC, Euclid wrote Optica , in which he studied the properties of light. Euclid postulated that light travelled in straight lines and he described the laws of reflection and studied them mathematically. He questioned that sight is the result of a beam from the eye, for he asks how one sees the stars immediately, if one closes one's eyes, then opens them at night. If

6700-437: The fifth century BC, Empedocles postulated that everything was composed of four elements ; fire, air, earth and water. He believed that goddess Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from

6800-425: The force of pressure acting on the back. Hence, as the resultant of the two forces, there remains a force that counteracts the motion of the plate and that increases with the velocity of the plate. We will call this resultant 'radiation friction' in brief." Usually light momentum is aligned with its direction of motion. However, for example in evanescent waves momentum is transverse to direction of propagation. In

6900-511: The greatest regard to economy. To reduce staff the NCOs and officers were responsible for instructing and examining the soldiers. If the men could not read or write they were taught to do so, and those who could read and write were taught to draw and interpret simple plans. The Royal Engineers Establishment quickly became the centre of excellence for all fieldworks and bridging. Captain Charles Pasley ,

7000-829: The groundwork for the foundation of the Grand Orient of Russia's Peoples . In 1947, the USSR introduced the Yablochkov Award for the best work in the field of electrical engineering. The crater Yablochkov on the Moon is named after him. Military engineering Military engineering is loosely defined as the art, science, and practice of designing and building military works and maintaining lines of military transport and military communications . Military engineers are also responsible for logistics behind military tactics. Modern military engineering differs from civil engineering . In

7100-429: The head of marching columns with axes, shovels, and pickaxes, clearing obstacles or building bridges to enable the main body of the regiment to move through difficult terrain. The modern Royal Welch Fusiliers and French Foreign Legion still maintain pioneer sections who march at the front of ceremonial parades, carrying chromium-plated tools intended for show only. Other historic distinctions include long work aprons and

7200-421: The human eye responds to light. The cone cells in the human eye are of three types which respond differently across the visible spectrum and the cumulative response peaks at a wavelength of around 555 nm. Therefore, two sources of light which produce the same intensity (W/m ) of visible light do not necessarily appear equally bright. The photometry units are designed to take this into account and therefore are

7300-418: The infrared and only a fraction in the visible spectrum. The peak of the black-body spectrum is in the deep infrared, at about 10 micrometre wavelength, for relatively cool objects like human beings. As the temperature increases, the peak shifts to shorter wavelengths, producing first a red glow, then a white one and finally a blue-white colour as the peak moves out of the visible part of the spectrum and into

7400-401: The infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it. Above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nm and the internal lens below 400 nm. Furthermore, the rods and cones located in the retina of the human eye cannot detect

7500-558: The kingdom. Both military engineers and artillery formed the body of this organization and served together until the office's successor, the Board of Ordnance was disbanded in 1855. In comparison to older weapons, the cannon was significantly more effective against traditional medieval fortifications . Military engineering significantly revised the way fortifications were built in order to be better protected from enemy direct and plunging shot. The new fortifications were also intended to increase

7600-553: The leading scientific military school in Europe. The dawn of the internal combustion engine marked the beginning of a significant change in military engineering. With the arrival of the automobile at the end of the 19th century and heavier than air flight at the start of the 20th century, military engineers assumed a major new role in supporting the movement and deployment of these systems in war. Military engineers gained vast knowledge and experience in explosives . They were tasked with planting bombs, landmines and dynamite . At

7700-426: The luminous body, rejecting the "forms" of Ibn al-Haytham and Witelo as well as the "species" of Roger Bacon , Robert Grosseteste and Johannes Kepler . In 1637 he published a theory of the refraction of light that assumed, incorrectly, that light travelled faster in a denser medium than in a less dense medium. Descartes arrived at this conclusion by analogy with the behaviour of sound waves. Although Descartes

7800-413: The movement of matter. He wrote, "radiation will exert pressure on both sides of the plate. The forces of pressure exerted on the two sides are equal if the plate is at rest. However, if it is in motion, more radiation will be reflected on the surface that is ahead during the motion (front surface) than on the back surface. The backwardacting force of pressure exerted on the front surface is thus larger than

7900-436: The popular description of light being "stopped" in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrary later time, as stimulated by a second laser pulse. During the time it had "stopped", it had ceased to be light. The study of light and the interaction of light and matter is termed optics . The observation and study of optical phenomena such as rainbows and

8000-501: The right to wear beards. In West Africa , the Ashanti army was accompanied to war by carpenters who were responsible for constructing shelters and blacksmiths who repaired weapons. By the 18th century, sappers were deployed in the Dahomeyan army during assaults against fortifications. The Peninsular War (1808–14) revealed deficiencies in the training and knowledge of officers and men of

8100-564: The same year where he built an industrial sample of the "electric candle" ( French patent № 112024, 1876). It was in Paris that he developed his arc light idea into a complete system of electric lighting powered by Zénobe Gramme direct current dynamos fitted with an inverter to supply single-phase alternating current . The first public use of the Yablochkov system was in October 1877 at Halle Marengo of

8200-442: The scope of military engineering. The word engineer was initially used in the context of warfare, dating back to 1325 when engine’er (literally, one who operates an engine) referred to "a constructor of military engines". In this context, "engine" referred to a military machine, i. e., a mechanical contraption used in war (for example, a catapult ). As the design of civilian structures such as bridges and buildings developed as

8300-601: The spectrum of each atom. Emission can be spontaneous , as in light-emitting diodes , gas discharge lamps (such as neon lamps and neon signs , mercury-vapor lamps , etc.) and flames (light from the hot gas itself—so, for example, sodium in a gas flame emits characteristic yellow light). Emission can also be stimulated , as in a laser or a microwave maser . Deceleration of a free charged particle, such as an electron , can produce visible radiation: cyclotron radiation , synchrotron radiation and bremsstrahlung radiation are all examples of this. Particles moving through

8400-435: The speed of light throughout history. Galileo attempted to measure the speed of light in the seventeenth century. An early experiment to measure the speed of light was conducted by Ole Rømer , a Danish physicist, in 1676. Using a telescope , Rømer observed the motions of Jupiter and one of its moons , Io . Noting discrepancies in the apparent period of Io's orbit, he calculated that light takes about 22 minutes to traverse

8500-406: The sun". The Indian Buddhists , such as Dignāga in the fifth century and Dharmakirti in the seventh century, developed a type of atomism that is a philosophy about reality being composed of atomic entities that are momentary flashes of light or energy. They viewed light as being an atomic entity equivalent to energy. René Descartes (1596–1650) held that light was a mechanical property of

8600-562: The term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays , X-rays , microwaves and radio waves are also light. The primary properties of light are intensity , propagation direction, frequency or wavelength spectrum , and polarization . Its speed in vacuum , 299 792 458  m/s , is one of the fundamental constants of nature. Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents

8700-486: The ultraviolet. These colours can be seen when metal is heated to "red hot" or "white hot". Blue-white thermal emission is not often seen, except in stars (the commonly seen pure-blue colour in a gas flame or a welder 's torch is in fact due to molecular emission, notably by CH radicals emitting a wavelength band around 425 nm and is not seen in stars or pure thermal radiation). Atoms emit and absorb light at characteristic energies. This produces " emission lines " in

8800-624: The very short (below 360 nm) ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses (such as insects and shrimp) are able to detect ultraviolet, by quantum photon-absorption mechanisms, in much the same chemical way that humans detect visible light. Various sources define visible light as narrowly as 420–680 nm to as broadly as 380–800 nm. Under ideal laboratory conditions, people can see infrared up to at least 1,050 nm; children and young adults may perceive ultraviolet wavelengths down to about 310–313 nm. Plant growth

8900-427: The visible region of the electromagnetic spectrum when plotted in wavelength units, and roughly 44% of the radiation that reaches the ground is visible. Another example is incandescent light bulbs , which emit only around 10% of their energy as visible light and the remainder as infrared. A common thermal light source in history is the glowing solid particles in flames , but these also emit most of their radiation in

9000-480: The wave theory was that light waves, like sound waves, would need a medium for transmission. The existence of the hypothetical substance luminiferous aether proposed by Huygens in 1678 was cast into strong doubt in the late nineteenth century by the Michelson–Morley experiment . Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied

9100-438: The world's first known explosive, black powder . Initially developed for recreational purposes, black powder later was utilized for military application in bombs and projectile propulsion in firearms. Engineers in the military who specialize in this field formulate and design many explosive devices to use in varying operating conditions. Such explosive compounds range from black powder to modern plastic explosives. This particular

9200-608: Was an active Freemason . He was initiated in 1876 into the Supreme Council of France of the Scottish Rite . After being "Worshipful Master" of three lodges in Paris , he created a new lodge under the Supreme Council known as "Cosmos" in 25 June 1887. Through this he hoped to attract young and wealthy Russian emigrants in Paris. One member of his lodge was Maksim Kovalevsky , who would later help bring Freemasonry back to Russia and prepare

9300-482: Was considerable international competition to his arc lights. His lasted only one and a half hours whereas those of Charles F. Brush lasted twice as long. From the mid-1880s, Yablochkov mostly occupied himself with problems of generating electric energy . He constructed the so-called “magnet dynamo electric machine”, which had most of the features of the modern inductor . Yablochkov did extensive research on transformation of fuel energy into electric energy, suggested

9400-576: Was emitted in all directions as a series of waves in a medium called the luminiferous aether . As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium. The wave theory predicted that light waves could interfere with each other like sound waves (as noted around 1800 by Thomas Young ). Young showed by means of a diffraction experiment that light behaved as waves. He also proposed that different colours were caused by different wavelengths of light and explained colour vision in terms of three-coloured receptors in

9500-432: Was for the first time qualitatively explained by Newton using the particle theory. Étienne-Louis Malus in 1810 created a mathematical particle theory of polarization. Jean-Baptiste Biot in 1812 showed that this theory explained all known phenomena of light polarization. At that time the polarization was considered as the proof of the particle theory. To explain the origin of colours , Robert Hooke (1635–1703) developed

9600-404: Was incorrect about the relative speeds, he was correct in assuming that light behaved like a wave and in concluding that refraction could be explained by the speed of light in different media. Descartes is not the first to use the mechanical analogies but because he clearly asserts that light is only a mechanical property of the luminous body and the transmitting medium, Descartes's theory of light

9700-658: Was largely replaced by mounted soldiers. It was not until later in the Middle Ages , that military engineering saw a revival focused on siege warfare. Military engineers planned castles and fortresses. When laying siege, they planned and oversaw efforts to penetrate castle defenses. When castles served a military purpose, one of the tasks of the sappers was to weaken the bases of walls to enable them to be breached before means of thwarting these activities were devised. Broadly speaking, sappers were experts at demolishing or otherwise overcoming or bypassing fortification systems. With

9800-521: Was placed in the path of the light beam as it traveled from the source, to the mirror and then returned to its origin. Fizeau found that at a certain rate of rotation, the beam would pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel and the rate of rotation, Fizeau was able to calculate the speed of light as 313 000 000  m/s . Léon Foucault carried out an experiment which used rotating mirrors to obtain

9900-601: Was successful in having 64 of his arc lights installed along the half mile (0.8 km) length of Avenue de l'Opéra , Place du Théâtre Français (today Place André-Malraux ) and around the Place de l'Opéra . It was first lit in February 1878. Yablochkov candles required high voltage, and it was not long before experimenters reported that the arc lights could be powered on a 7-mile (11 km) circuit. Yablochkov candles were superior to Lontin-Serrin regulator arc lights that each required

10000-585: Was the model that modern transmission and distribution systems would settle on. As the patent said such a system "allowed to provide separate supply to several lighting fixtures with different luminous intensities from a single source of electric power". In 1879, Yablochkov established “Electric Lighting Company, P.N. Yablochkov the Inventor and Co” and an electrical plant in Petersburg that would later produce illuminators for military vessels and factories. There

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