Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, space navigation, it is the term of art used for the specialized knowledge used by navigators to perform navigation tasks. All navigational techniques involve locating the navigator's position compared to known locations or patterns. Navigation, in a broader sense, can refer to any skill or study that involves the determination of position and direction. In this sense, navigation includes pedestrian navigation. In the European medieval period, navigation was considered part of the set of seven mechanical arts, none of which were used for long voyages across open ocean. Polynesian navigation is the earliest form of open-ocean navigation, it was based on memory and observation recorded on scientific instruments like the Marshall Islands Stick Charts of Ocean Swells.
Early Pacific Polynesians used the motion of stars, the position of certain wildlife species, or the size of waves to find the path from one island to another. Maritime navigation using scientific instruments such as the mariner's astrolabe first occurred in the Mediterranean during the Middle Ages. Although land astrolabes were invented in the Hellenistic period and existed in classical antiquity and the Islamic Golden Age, the oldest record of a sea astrolabe is that of Majorcan astronomer Ramon Llull dating from 1295; the perfecting of this navigation instrument is attributed to Portuguese navigators during early Portuguese discoveries in the Age of Discovery. The earliest known description of how to make and use a sea astrolabe comes from Spanish cosmographer Martín Cortés de Albacar's Arte de Navegar published in 1551, based on the principle of the archipendulum used in constructing the Egyptian pyramids. Open-seas navigation using the astrolabe and the compass started during the Age of Discovery in the 15th century.
The Portuguese began systematically exploring the Atlantic coast of Africa from 1418, under the sponsorship of Prince Henry. In 1488 Bartolomeu Dias reached the Indian Ocean by this route. In 1492 the Spanish monarchs funded Christopher Columbus's expedition to sail west to reach the Indies by crossing the Atlantic, which resulted in the Discovery of the Americas. In 1498, a Portuguese expedition commanded by Vasco da Gama reached India by sailing around Africa, opening up direct trade with Asia. Soon, the Portuguese sailed further eastward, to the Spice Islands in 1512, landing in China one year later; the first circumnavigation of the earth was completed in 1522 with the Magellan-Elcano expedition, a Spanish voyage of discovery led by Portuguese explorer Ferdinand Magellan and completed by Spanish navigator Juan Sebastián Elcano after the former's death in the Philippines in 1521. The fleet of seven ships sailed from Sanlúcar de Barrameda in Southern Spain in 1519, crossed the Atlantic Ocean and after several stopovers rounded the southern tip of South America.
Some ships were lost, but the remaining fleet continued across the Pacific making a number of discoveries including Guam and the Philippines. By only two galleons were left from the original seven; the Victoria led by Elcano sailed across the Indian Ocean and north along the coast of Africa, to arrive in Spain in 1522, three years after its departure. The Trinidad sailed east from the Philippines, trying to find a maritime path back to the Americas, but was unsuccessful; the eastward route across the Pacific known as the tornaviaje was only discovered forty years when Spanish cosmographer Andrés de Urdaneta sailed from the Philippines, north to parallel 39°, hit the eastward Kuroshio Current which took its galleon across the Pacific. He arrived in Acapulco on October 8, 1565; the term stems from the 1530s, from Latin navigationem, from navigatus, pp. of navigare "to sail, sail over, go by sea, steer a ship," from navis "ship" and the root of agere "to drive". The latitude of a place on Earth is its angular distance north or south of the equator.
Latitude is expressed in degrees ranging from 0° at the Equator to 90° at the North and South poles. The latitude of the North Pole is 90° N, the latitude of the South Pole is 90° S. Mariners calculated latitude in the Northern Hemisphere by sighting the North Star Polaris with a sextant and using sight reduction tables to correct for height of eye and atmospheric refraction; the height of Polaris in degrees above the horizon is the latitude of the observer, within a degree or so. Similar to latitude, the longitude of a place on Earth is the angular distance east or west of the prime meridian or Greenwich meridian. Longitude is expressed in degrees ranging from 0° at the Greenwich meridian to 180° east and west. Sydney, for example, has a longitude of about 151° east. New York City has a longitude of 74° west. For most of history, mariners struggled to determine longitude. Longitude can be calculated. Lacking that, one can use a sextant to take a lunar distance that, with a nautical almanac, can be used to calculate the time at zero longitude.
Reliable marine chronometers were unavailable until the late 18th century and not affordable until the 19th century. For about a hundred years, from about 1767 until about 1850, mariners lacking a chronometer used the method of lunar distances to determine Greenwich time to find their longitude. A mariner with a chronometer could check its reading using a lunar determination of Greenwich tim
A compass is an instrument used for navigation and orientation that shows direction relative to the geographic cardinal directions. A diagram called a compass rose shows the directions north, south and west on the compass face as abbreviated initials; when the compass is used, the rose. Compasses display markings for angles in degrees in addition to the rose. North corresponds to 0°, the angles increase clockwise, so east is 90° degrees, south is 180°, west is 270°; these numbers allow the compass to show magnetic North azimuths or true North azimuths or bearings, which are stated in this notation. If magnetic declination between the magnetic North and true North at latitude angle and longitude angle is known direction of magnetic North gives direction of true North. Among the Four Great Inventions, the magnetic compass was first invented as a device for divination as early as the Chinese Han Dynasty, adopted for navigation by the Song Dynasty Chinese during the 11th century; the first usage of a compass recorded in Western Europe and the Islamic world occurred around 1190.
The magnetic compass is the most familiar compass type. It functions as a pointer to "magnetic north", the local magnetic meridian, because the magnetized needle at its heart aligns itself with the horizontal component of the Earth's magnetic field; the magnetic field exerts a torque on the needle, pulling the North end or pole of the needle toward the Earth's North magnetic pole, pulling the other toward the Earth's South magnetic pole. The needle is mounted on a low-friction pivot point, in better compasses a jewel bearing, so it can turn easily; when the compass is held level, the needle turns until, after a few seconds to allow oscillations to die out, it settles into its equilibrium orientation. In navigation, directions on maps are expressed with reference to geographical or true north, the direction toward the Geographical North Pole, the rotation axis of the Earth. Depending on where the compass is located on the surface of the Earth the angle between true north and magnetic north, called magnetic declination can vary with geographic location.
The local magnetic declination is given on most maps, to allow the map to be oriented with a compass parallel to true north. The location of the Earth's magnetic poles change with time, referred to as geomagnetic secular variation; the effect of this means. Some magnetic compasses include means to manually compensate for the magnetic declination, so that the compass shows true directions. There are other ways to find north than the use of magnetism, from a navigational point of view a total of seven possible ways exist. Two sensors that utilize two of the remaining six principles are also called compasses, i.e. gyrocompass and GPS-compass. A gyrocompass is similar to a gyroscope, it is a non-magnetic compass that finds true north by using an fast-spinning wheel and friction forces in order to exploit the rotation of the Earth. Gyrocompasses are used on ships, they have two main advantages over magnetic compasses: they find true north, i.e. the direction of Earth's rotational axis, as opposed to magnetic north, they are not affected by ferromagnetic metal in a ship's hull.
Large ships rely on a gyrocompass, using the magnetic compass only as a backup. Electronic fluxgate compasses are used on smaller vessels. However, magnetic compasses are still in use as they can be small, use simple reliable technology, are comparatively cheap, are easier to use than GPS, require no energy supply, unlike GPS, are not affected by objects, e.g. trees, that can block the reception of electronic signals. GPS receivers using two or more antennae mounted separately and blending the data with an inertial motion unit can now achieve 0.02° in heading accuracy and have startup times in seconds rather than hours for gyrocompass systems. The devices determine the positions of the antennae on the Earth, from which the cardinal directions can be calculated. Manufactured for maritime and aviation applications, they can detect pitch and roll of ships. Small, portable GPS receivers with only a single antenna can determine directions if they are being moved if only at walking pace. By determining its position on the Earth at times a few seconds apart, the device can calculate its speed and the true bearing of its direction of motion.
It is preferable to measure the direction in which a vehicle is moving, rather than its heading, i.e. the direction in which its nose is pointing. These directions may be different if there is tidal current. GPS compasses share the main advantages of gyrocompasses, they determine true North, as opposed to magnetic North, they are unaffected by perturbations of the Earth's magnetic field. Additionally, compared with gyrocompasses, they are much cheaper, they work better in polar regions, they are less prone to be affected by mechanical vibration, they can be initialized far more quickly. However, they depend on the functioning of, communication with, the GPS satellites, which might be disrupted by an electronic attack or by the effects of
Age of Enlightenment
The Age of Enlightenment was an intellectual and philosophical movement that dominated the world of ideas in Europe during the 18th century, the "Century of Philosophy". Some consider Descartes' 1637 statement "I think" to have sparked the period. Others cite the publication of Isaac Newton's Principia Mathematica. French historians traditionally date the Enlightenment from 1715 to 1789, from the beginning of the reign of Louis XV until the French Revolution. Most end it with the turn of the 19th century. Philosophers and scientists of the period circulated their ideas through meetings at scientific academies, Masonic lodges, literary salons, coffeehouses and in printed books and pamphlets; the ideas of the Enlightenment undermined the authority of the monarchy and the Church and paved the way for the political revolutions of the 18th and 19th centuries. A variety of 19th-century movements, including liberalism and neo-classicism, trace their intellectual heritage to the Enlightenment; the Enlightenment included a range of ideas centered on reason as the primary source of knowledge and advanced ideals such as liberty, toleration, constitutional government and separation of church and state.
In France, the central doctrines of the Enlightenment philosophers were individual liberty and religious tolerance, in opposition to an absolute monarchy and the fixed dogmas of the Roman Catholic Church. The Enlightenment was marked by an emphasis on the scientific method and reductionism, along with increased questioning of religious orthodoxy—an attitude captured by the phrase Sapere aude; the Age of Enlightenment was preceded by and associated with the scientific revolution. Earlier philosophers whose work influenced the Enlightenment included Bacon, Descartes and Spinoza; the major figures of the Enlightenment included Beccaria, Hume, Montesquieu, Adam Smith, Voltaire. Some European rulers, including Catherine II of Russia, Joseph II of Austria and Frederick II of Prussia, tried to apply Enlightenment thought on religious and political tolerance, which became known as enlightened absolutism. Benjamin Franklin visited Europe and contributed to the scientific and political debates there and brought the newest ideas back to Philadelphia.
Thomas Jefferson followed European ideas and incorporated some of the ideals of the Enlightenment into the Declaration of Independence. One of his peers, James Madison, incorporated these ideals into the United States Constitution during its framing in 1787; the most influential publication of the Enlightenment was the Encyclopédie. Published between 1751 and 1772 in thirty-five volumes, it was compiled by Diderot, d'Alembert and a team of 150 scientists and philosophers, it helped spread the ideas of the Enlightenment across Europe and beyond. Other landmark publications were Voltaire's Dictionnaire Letters on the English; the ideas of the Enlightenment played a major role in inspiring the French Revolution, which began in 1789. After the Revolution, the Enlightenment was followed by the intellectual movement known as Romanticism. René Descartes' rationalist philosophy laid the foundation for enlightenment thinking, his attempt to construct the sciences on a secure metaphysical foundation was not as successful as his method of doubt applied in philosophic areas leading to a dualistic doctrine of mind and matter.
His skepticism was refined by John Locke's Essay Concerning Human Understanding and David Hume's writings in the 1740s. His dualism was challenged by Spinoza's uncompromising assertion of the unity of matter in his Tractatus and Ethics; these laid down two distinct lines of Enlightenment thought: first, the moderate variety, following Descartes and Christian Wolff, which sought accommodation between reform and the traditional systems of power and faith, second, the radical enlightenment, inspired by the philosophy of Spinoza, advocating democracy, individual liberty, freedom of expression and eradication of religious authority. The moderate variety tended to be deistic, whereas the radical tendency separated the basis of morality from theology. Both lines of thought were opposed by a conservative Counter-Enlightenment, which sought a return to faith. In the mid-18th century, Paris became the center of an explosion of philosophic and scientific activity challenging traditional doctrines and dogmas.
The philosophic movement was led by Voltaire and Jean-Jacques Rousseau, who argued for a society based upon reason as in ancient Greece rather than faith and Catholic doctrine, for a new civil order based on natural law, for science based on experiments and observation. The political philosopher Montesquieu introduced the idea of a separation of powers in a government, a concept, enthusiastically adopted by the authors of the United States Constitution. While the Philosophes of the French Enlightenment were not revolutionaries and many were members of the nobility, their ideas played an important part in undermining the legitimacy of the Old Regime and shaping the French Revolution. Francis Hutcheson, a moral philosopher, described the utilitarian and consequentialist principle that virtue is that which provides, in his words, "the greatest happiness for the greatest numbers". Much of what is incorporated in the scientific method
East India Company
The East India Company known as the Honourable East India Company or the British East India Company and informally as John Company, Company Bahadur, or The Company, was an English and British joint-stock company. It was formed to trade in the Indian Ocean region with Mughal India and the East Indies, with Qing China; the company ended up seizing control over large parts of the Indian subcontinent, colonised parts of Southeast Asia, colonised Hong Kong after a war with Qing China. Chartered as the "Governor and Company of Merchants of London trading into the East Indies", the company rose to account for half of the world's trade in basic commodities including cotton, indigo dye, spices, saltpetre and opium; the company ruled the beginnings of the British Empire in India. In his speech to the House of Commons in July 1833, Lord Macaulay explained that since the beginning, the East India company had always been involved in both trade and politics, just as its French and Dutch counterparts had been.
The company received a Royal Charter from Queen Elizabeth I on 31 December 1600, coming late to trade in the Indies. Before them the Portuguese Estado da Índia had traded there for much of the 16th century and the first of half a dozen Dutch Companies sailed to trade there from 1595; these Dutch companies amalgamated in March 1602 into the United East Indies Company, which introduced the first permanent joint stock from 1612. By contrast, wealthy merchants and aristocrats owned the EIC's shares; the government owned no shares and had only indirect control until 1657 when permanent joint stock was established. During its first century of operation, the focus of the company was trade, not the building of an empire in India. Company interests turned from trade to territory during the 18th century as the Mughal Empire declined in power and the East India Company struggled with its French counterpart, the French East India Company during the Carnatic Wars of the 1740s and 1750s; the battles of Plassey and Buxar, in which the British defeated the Bengali powers, left the company in control of Bengal and a major military and political power in India.
In the following decades it increased the extent of the territories under its control, controlling the majority of the Indian subcontinent either directly or indirectly via local puppet rulers under the threat of force by its Presidency armies, much of which were composed of native Indian sepoys. By 1803, at the height of its rule in India, the British East India company had a private army of about 260,000—twice the size of the British Army, with Indian revenues of £13,464,561, expenses of £14,017,473; the company came to rule large areas of India with its private armies, exercising military power and assuming administrative functions. Company rule in India began in 1757 and lasted until 1858, following the Indian Rebellion of 1857, the Government of India Act 1858 led to the British Crown's assuming direct control of the Indian subcontinent in the form of the new British Raj. Despite frequent government intervention, the company had recurring problems with its finances, it was dissolved in 1874 as a result of the East India Stock Dividend Redemption Act passed one year earlier, as the Government of India Act had by rendered it vestigial and obsolete.
The official government machinery of British India assumed the East India Company's governmental functions and absorbed its navy and its armies in 1858. Soon after the defeat of the Spanish Armada in 1588, the captured Spanish and Portuguese ships with their cargoes enabled English voyagers to travel the globe in search of riches. London merchants presented a petition to Queen Elizabeth I for permission to sail to the Indian Ocean; the aim was to deliver a decisive blow to the Portuguese monopoly of Far Eastern Trade. Elizabeth granted her permission and on 10 April 1591 James Lancaster in the Bonaventure with two other ships sailed from Torbay around the Cape of Good Hope to the Arabian Sea on one of the earliest English overseas Indian expeditions. Having sailed around Cape Comorin to the Malay Peninsula, they preyed on Spanish and Portuguese ships there before returning to England in 1594; the biggest capture that galvanised English trade was the seizure of the large Portuguese Carrack, the Madre de Deus by Sir Walter Raleigh and the Earl of Cumberland at the Battle of Flores on 13 August 1592.
When she was brought in to Dartmouth she was the largest vessel, seen in England and her cargo consisted of chests filled with jewels, gold, silver coins, cloth, pepper, cinnamon, benjamin, red dye and ebony. Valuable was the ship's rutter containing vital information on the China and Japan trades; these riches aroused the English to engage in this opulent commerce. In 1596, three more English ships were all lost at sea. A year however saw the arrival of Ralph Fitch, an adventurer merchant who, along with his companions, had made a remarkable fifteen-year overland journey to Mesopotamia, the Persian Gulf, the Indian Ocean and Southeast Asia. Fitch was consulted on the Indian affairs and gave more valuable information to Lancaster. On 22 September 1599, a group of merchants met and stated their intention "to venture in the pretended voyage to the East Indies, the sums that they will adventure", committing £30
A jetboat is a boat propelled by a jet of water ejected from the back of the craft. Unlike a powerboat or motorboat that uses an external propeller in the water below or behind the boat, a jetboat draws the water from under the boat through an intake and into a pump-jet inside the boat, before expelling it through a nozzle at the stern. Jetboats were designed by Sir William Hamilton for operation in the fast-flowing and shallow rivers of New Zealand to overcome the problem of propellers striking rocks in such waters. Previous attempts at waterjet propulsion had short lifetimes due to the inefficient design of the units and the fact that they offered few advantages over conventional propellers. Unlike these previous waterjet developments, such as Campini's and the Hanley Hydrojet, Hamilton had a specific need for a propulsion system to operate in shallow water, the waterjet proved to be the ideal solution. From this, the popularity of the jet unit and jetboat increased rapidly. Through further developments, it was found the waterjet offered several other advantages over propellers for a wide range of vessel types, as such, waterjets are used today for many high-speed vessels, including passenger ferries, rescue craft, patrol boats and offshore supply vessels.
Jetboats are maneuverable, many can, from full speed, be reversed and brought to a stop within little more than their own length, in a maneuver known as a "crash stop". The well known Hamilton turn or "jet spin" is a high-speed maneuver where the boat's engine throttle is cut, the steering is turned and the throttle opened again, causing the boat to spin around with a large spray of water. There is no engineering limit to the size of jetboats, though the validity of their use depends a lot on the type of application. Classic prop-drives are more efficient and economical at low speeds, up to about 20 knots, but as boat speed increases beyond this, the extra hull resistance generated by struts, shafts means waterjets are more efficient in the 20–50 knot range. In situations with large propellers turning at slow speeds, the equivalent size waterjet would be too big to be practical. For these reasons, the vast majority of waterjet units are installed in high-speed vessels and in particular situations where shallow draught and load flexibility are main concerns.
The biggest jet-driven vessels are found in military use or the high-speed passenger/car ferry industry. South Africa's Valour-class frigates and the United States Littoral Combat Ship are among the biggest jet-propelled vessels so far; these vessels are capable of performing "crash stops". A conventional screw propeller works within the body of water below a boat hull "screwing" through the water to drive a vessel forward by generating a difference in pressure between the forward and rear surfaces of the propeller blades and by accelerating a mass of water rearward. By contrast, a waterjet unit delivers a high-pressure "push" from the stern of a vessel by accelerating a volume of water as it passes through a specialised pump mounted above the waterline inside the boat hull. Both methods yield thrust due to Newton's third law— every action has an equal and opposite reaction. In a jetboat, the waterjet draws water from beneath the hull, where it passes through a series of impellers and stators – known as stages – which increase the velocity of the waterflow.
Most modern jets are single-stage. The tail section of the waterjet unit extends out through the transom of the hull, above the waterline; this jetstream exits the unit through a small nozzle at high velocity to push the boat forward. Steering is accomplished by moving this nozzle to either side, or less by small gates on either side that deflect the jetstream; because the jetboat relies on the flow of water through the nozzle for control, it is not possible to steer a conventional jetboat without the engine running. Unlike conventional propeller systems where the rotation of the propeller is reversed to provide astern movement, a waterjet will continue to pump while a deflector is lowered into the jetstream after it leaves the outlet nozzle; this deflector redirects thrust forces forward to provide reverse thrust. Most developed reverse deflectors redirect the jetstream down and to each side to prevent recirculation of the water through the jet again, which may cause aeration problems, or increase reverse thrust.
Steering is still available with the reverse deflector lowered so the vessel will have full maneuverability. With the deflector lowered about halfway into the jetstream and reverse thrust are equal so the boat maintains a fixed position, but steering is still available to allow the vessel to turn on the spot – something, impossible with a conventional single propeller. Unlike hydrofoils, which use underwater wings or struts to lift the vessel clear of the water, standard jetboats use a conventional planing hull to ride across the water surface, with only the rear portion of the hull displacing any water. With the majority of the hull clear of the water, there is reduced drag enhancing speed and maneuverability, so jetboats are operated at planing speed. At slower speeds with less water pumping through the jet unit, the jetboat will lose some steering control and maneuverability and will slow down as the hull comes off its planing state and hull resistance is increased. However, loss of steering control at low speeds can be overcome by lowering the rev
In philosophy, empiricism is a theory that states that knowledge comes only or from sensory experience. It is one of several views of epistemology, the study of human knowledge, along with rationalism and skepticism. Empiricism emphasises the role of empirical evidence in the formation of ideas, rather than innate ideas or traditions. However, empiricists may argue. Empiricism in the philosophy of science emphasises evidence as discovered in experiments, it is a fundamental part of the scientific method that all hypotheses and theories must be tested against observations of the natural world rather than resting on a priori reasoning, intuition, or revelation. Empiricism used by natural scientists, says that "knowledge is based on experience" and that "knowledge is tentative and probabilistic, subject to continued revision and falsification". Empirical research, including experiments and validated measurement tools, guides the scientific method; the English term empirical derives from the Ancient Greek word ἐμπειρία, cognate with and translates to the Latin experientia, from which the words experience and experiment are derived.
A central concept in science and the scientific method is that it must be empirically based on the evidence of the senses. Both natural and social sciences use working hypotheses that are testable by observation and experiment; the term semi-empirical is sometimes used to describe theoretical methods that make use of basic axioms, established scientific laws, previous experimental results in order to engage in reasoned model building and theoretical inquiry. Philosophical empiricists hold no knowledge to be properly inferred or deduced unless it is derived from one's sense-based experience; this view is contrasted with rationalism, which states that knowledge may be derived from reason independently of the senses. For example, John Locke held that some knowledge could be arrived at through intuition and reasoning alone. Robert Boyle, a prominent advocate of the experimental method, held that we have innate ideas; the main continental rationalists were advocates of the empirical "scientific method".
Vaisheshika darsana, founded by the ancient Indian philosopher Kanada, accepted perception and inference as the only two reliable sources of knowledge. This is enumerated in his work Vaiśeṣika Sūtra; the earliest Western proto-empiricists were the Empiric school of ancient Greek medical practitioners, who rejected the three doctrines of the Dogmatic school, preferring to rely on the observation of phantasiai. The Empiric school was allied with Pyrrhonist school of philosophy, which made the philosophical case for their proto-empiricism; the notion of tabula rasa connotes a view of mind as an blank or empty recorder on which experience leaves marks. This denies; the image dates back to Aristotle: What the mind thinks must be in it in the same sense as letters are on a tablet which bears no actual writing. Aristotle's explanation of how this was possible was not empiricist in a modern sense, but rather based on his theory of potentiality and actuality, experience of sense perceptions still requires the help of the active nous.
These notions contrasted with Platonic notions of the human mind as an entity that pre-existed somewhere in the heavens, before being sent down to join a body on Earth. Aristotle was considered to give a more important position to sense perception than Plato, commentators in the Middle Ages summarized one of his positions as "nihil in intellectu nisi prius fuerit in sensu"; this idea was developed in ancient philosophy by the Stoic school. Stoic epistemology emphasized that the mind starts blank, but acquires knowledge as the outside world is impressed upon it; the doxographer Aetius summarizes this view as "When a man is born, the Stoics say, he has the commanding part of his soul like a sheet of paper ready for writing upon." During the Middle Ages Aristotle's theory of tabula rasa was developed by Islamic philosophers starting with Al Farabi, developing into an elaborate theory by Avicenna and demonstrated as a thought experiment by Ibn Tufail. For Avicenna, for example, the tabula rasa is a pure potentiality, actualized through education, knowledge is attained through "empirical familiarity with objects in this world from which one abstracts universal concepts" developed through a "syllogistic method of reasoning in which observations lead to propositional statements which when compounded lead to further abstract concepts".
The intellect itself develops from a material intellect, a potentiality "that can acquire knowledge to the active intellect, the state of the human intellect in conjunction with the perfect source of knowledge". So the immaterial "active intellect", separate from any individual person, is still essential for understanding to occur. In the 12th century CE the Andalusian Muslim philosopher and novelist Abu Bakr Ibn Tufail included the theory of tabula rasa as a thought experiment in his Arabic philosophical novel, Hayy ibn Yaqdhan in which he depicted the development of the mind of a feral child "from a tabula rasa to that o
A royal yacht is a ship used by a monarch or a royal family. If the monarch is an emperor the proper term is imperial yacht. Most of them are financed by the government of the country; the royal yacht is most manned by personnel from the navy and used by the monarch and his/her family on both private and official travels. Some royal yachts have been/are small vessels only used for short trips on rivers or in calm waters, but others have been/are large seaworthy ships. Depending on how the term is defined royal yachts date back to the days of antiquity with royal barges on the Nile in ancient Egypt; the Vikings produced royal vessels. They followed the pattern of longships although decorated and fitted with purple sails. In England, Henry V sold off the royal yachts to clear the Crown's debts; the next royal vessels in England were built in the Tudor period with Henry VIII using a vessel in 1520, depicted as having cloth of gold sails. James I had Disdain, a ship in miniature, built for his son Prince Henry.
Disdain was significant in that she allowed for pleasure cruising and as a result can be seen as an early move away from royal ships as warships. The first ships to unquestionably qualify as royal yachts were those owned by Charles II of England Scotland and Ireland; the first was gift from the Dutch but yachts were commissioned and built in England. This established a tradition of royal yachts in Britain, copied by other royal families of Europe. Through the 19th century royal yachts got larger. World War I brought this trend to an end and the royal families that survived found it harder to justify the cost with the result that there are only three royal yachts left in use in Europe. For the most part royal yachts have been superseded by the use of warships in this role, as royal yachts are seen as a hard-to-justify expenditure. In addition most monarchies with a railway system employ a special set of royal carriages. Most monarchies employ aircraft as a luxurious mode of transportation; the Danish royal family have had several royal yachts.
Two of them have been named Dannebrog. HMDY Sophia Amalia HMDY Elephanten HMDY Kiel HDMY Ægir HMDY Slesvig HDMS Jylland – a frigate which served as a royal yacht on occasion. HDMY Dannebrog HDMY Dannebrog Dubai is the personal yacht of Sheikh Mohammed bin Rashid Al Maktoum, ruler of Dubai and Prime Minister of the United Arab Emirates. Completed in 2006, she is the third largest yacht in service at 524 feet long, she came to world media attention when she sailed out to welcome the retired ocean liner, RMS Queen Elizabeth 2 to Dubai in November 2008. Another personal yacht of the Sheikh, is the 40-metre Alloya. Built by Sanlorenzo in 2013. Mahroussa was built for the Khedive of Egypt, she passed the Suez Canal during its opening. Lengthened twice, she was converted from paddle steamer to screws, she now serves as a school ship for the Egyptian Navy. The luxury yacht Fortuna & the sailing yacht Bribón XV both belonged to King Juan Carlos I until he renounced them in 2013. During the existence of the German Empire, the Kaiser used these imperial yachts: SMY Hohenzollern.
Cleopatra's Barge renamed Haʻaheo o Hawaiʻi Kamehameha III, seized by the French when they invaded Honolulu Savoia Trinacria, former steamship America Savoia De Groene Draeck Jumbo VI Prince Bernhard's yacht, a Moonen 85 King Haakon VII received the royal yacht Norge as a gift from the people of Norway in 1947. The royal yacht manned by the Royal Norwegian Navy. Before this other naval ships had served as royal sea transport and the king used some smaller boats for short trips on official occasions. Sophia Amalia Elephanten Heimdal Stjernen I Stjernen II Norge Horten The Oman Royal Yacht Squadron operates the following major vessels from Muscat and Muttrah in Oman: The Imperial Ottoman Government used many yachts for its head of state; these include: Tesrifiye İzzeddin Sultaniye Talia ErtuğrulThe Republic of Turkey has presidential yachts Veloz: 1858 Sirius: 1876 Amélia I: 1888 Amélia II: 1897 Amélia III: 1898 Amélia IV: 1901The Portuguese King Charles I used four successive royal yachts, all named Amélia, after his wife, Queen Amélie of Orleans.
These yachts were used by Charles I for his oceanographic missions. It was in the Amélia IV that King Manuel II and the Portuguese royal family left the country for the exile, after the republican revolution of 5 October 1910. In the republican regime the Amélia IV was renamed NRP 5 de Outubro and operated by the Portuguese Navy. Imperial yachts employed by the Tsar of Russia: Alexandria Standart Derzhava Tsarevna Livadia. Used by the Romanovs only twice. Polyarnaya Zvezda Alexandria Standart Saudi ro