In physics, escape velocity is the minimum speed needed for a free object to escape from the gravitational influence of a massive body. It is slower the further away from the body an object is, slower for less massive bodies; the escape velocity from Earth is about 11.186 km/s at the surface. More escape velocity is the speed at which the sum of an object's kinetic energy and its gravitational potential energy is equal to zero. With escape velocity in a direction pointing away from the ground of a massive body, the object will move away from the body, slowing forever and approaching, but never reaching, zero speed. Once escape velocity is achieved, no further impulse need to be applied for it to continue in its escape. In other words, if given escape velocity, the object will move away from the other body, continually slowing, will asymptotically approach zero speed as the object's distance approaches infinity, never to come back. Speeds higher than escape velocity have a positive speed at infinity.
Note that the minimum escape velocity assumes that there is no friction, which would increase the required instantaneous velocity to escape the gravitational influence, that there will be no future acceleration or deceleration, which would change the required instantaneous velocity. For a spherically symmetric, massive body such as a star, or planet, the escape velocity for that body, at a given distance, is calculated by the formula v e = 2 G M r, where G is the universal gravitational constant, M the mass of the body to be escaped from, r the distance from the center of mass of the body to the object; the relationship is independent of the mass of the object escaping the massive body. Conversely, a body that falls under the force of gravitational attraction of mass M, from infinity, starting with zero velocity, will strike the massive object with a velocity equal to its escape velocity given by the same formula; when given an initial speed V greater than the escape speed v e, the object will asymptotically approach the hyperbolic excess speed v ∞, satisfying the equation: v ∞ 2 = V 2 − v e 2.
In these equations atmospheric friction is not taken into account. A rocket moving out of a gravity well does not need to attain escape velocity to escape, but could achieve the same result at any speed with a suitable mode of propulsion and sufficient propellant to provide the accelerating force on the object to escape. Escape velocity is only required to send a ballistic object on a trajectory that will allow the object to escape the gravity well of the mass M; the existence of escape velocity is a consequence of conservation of energy and an energy field of finite depth. For an object with a given total energy, moving subject to conservative forces it is only possible for the object to reach combinations of locations and speeds which have that total energy. By adding speed to the object it expands the possible locations that can be reached, with enough energy, they become infinite. For a given gravitational potential energy at a given position, the escape velocity is the minimum speed an object without propulsion needs to be able to "escape" from the gravity.
Escape velocity is a speed because it does not specify a direction: no matter what the direction of travel is, the object can escape the gravitational field. The simplest way of deriving the formula for escape velocity is to use conservation of energy. For the sake of simplicity, unless stated otherwise, we assume that an object is attempting to escape from a uniform spherical planet by moving away from it and that the only significant force acting on the moving object is the planet's gravity. In its initial state, i, imagine that a spaceship of mass m is at a distance r from the center of mass of the planet, whose mass is M, its initial speed is equal to v e. At its final state, f, it will be an infinite distance away from the planet, its speed will be negligibly small and assumed to be 0. Kinetic energy K and gravitational potential energy Ug are the only types of energy that we will deal with, so by the conservation of energy, i = f Kƒ = 0 because final velocity is zero, Ugƒ = 0 because its final distance is infinity, so ⇒ 1 2 m v e 2 + − G M m r
Louis XIV of France
Louis XIV, known as Louis the Great or the Sun King, was a monarch of the House of Bourbon who reigned as King of France from 1643 until his death in 1715. Starting on 14 May 1643 when Louis was 4 years old, his reign of 72 years and 110 days is the longest recorded of any monarch of a sovereign country in European history. In the age of absolutism in Europe, Louis XIV's France was a leader in the growing centralisation of power. Louis began his personal rule of France in 1661, after the death of his chief minister, the Italian Cardinal Mazarin. An adherent of the concept of the divine right of kings, Louis continued his predecessors' work of creating a centralised state governed from the capital, he sought to eliminate the remnants of feudalism persisting in parts of France and, by compelling many members of the nobility to inhabit his lavish Palace of Versailles, succeeded in pacifying the aristocracy, many members of which had participated in the Fronde rebellion during Louis' minority. By these means he became one of the most powerful French monarchs and consolidated a system of absolute monarchical rule in France that endured until the French Revolution.
Louis encouraged and benefited from the work of prominent political and cultural figures such as Mazarin, Louvois, the Grand Condé, Turenne, Sébastien Le Prestre de Vauban, André Charles Boulle, Molière, Boileau, La Fontaine, Marais, Le Brun, Bossuet, Le Vau, Charles, Claude Perrault, Le Nôtre. Under his rule, the Edict of Nantes, which granted rights to Huguenots, was abolished; the revocation forced Huguenots to emigrate or convert in a wave of dragonnades, which managed to destroy the French Protestant minority. During Louis' long reign, France was the leading European power, it fought three major wars: the Franco-Dutch War, the War of the League of Augsburg, the War of the Spanish Succession. There were two lesser conflicts: the War of Devolution and the War of the Reunions. Warfare defined the foreign policy of Louis XIV, his personality shaped his approach. Impelled "by a mix of commerce and pique", Louis sensed that warfare was the ideal way to enhance his glory. In peacetime he concentrated on preparing for the next war.
He taught his diplomats that their job was to create tactical and strategic advantages for the French military. Louis XIV was born on 5 September 1638 in the Château de Saint-Germain-en-Laye, to Louis XIII and Anne of Austria, he was named Louis Dieudonné and bore the traditional title of French heirs apparent: Dauphin. At the time of his birth, his parents had been married for 23 years, his mother had experienced four stillbirths between 1619 and 1631. Leading contemporaries thus regarded him as his birth a miracle of God. Sensing imminent death, Louis XIII decided to put his affairs in order in the spring of 1643, when Louis XIV was four years old. In defiance of custom, which would have made Queen Anne the sole Regent of France, the king decreed that a regency council would rule on his son's behalf, his lack of faith in Queen Anne's political abilities was his primary rationale. He did, make the concession of appointing her head of the council. Louis' relationship with his mother was uncommonly affectionate for the time.
Contemporaries and eyewitnesses claimed. Both were interested in food and theatre, it is likely that Louis developed these interests through his close relationship with his mother; this long-lasting and loving relationship can be evidenced by excerpts in Louis' journal entries, such as: "Nature was responsible for the first knots which tied me to my mother. But attachments formed by shared qualities of the spirit are far more difficult to break than those formed by blood." It was his mother who gave Louis his belief in the absolute and divine power of his monarchical rule. During his childhood, he was taken care of by the governesses Françoise de Lansac and Marie-Catherine de Senecey. In 1646, Nicolas V de Villeroy became the young king's tutor. Louis XIV became friends with Villeroy's young children François de Villeroy, divided his time between the Palais-Royal and the nearby Hotel de Villeroy. On 14 May 1643, with Louis XIII dead, Queen Anne had her husband's will annulled by the Parlement de Paris.
This action made Anne sole Regent of France. Anne exiled some of her husband's ministers, she nominated Brienne as her minister of foreign affairs. Anne nominated Saint Vincent de Paul as her spiritual adviser, which helped her deal with religious policy and the Jansenism question. Anne kept the direction of religious policy in her hand until 1661. Anne wanted to give her son a victorious kingdom, her rationales for choosing Mazarin were his ability and his total dependence on her, at least until 1653 when she was no longer regent. Anne protected Mazarin by arresting and exiling her followers who conspired against him in 1643: the Duke of Beaufort and Marie de Rohan, she left the direction of the daily administration of policy to Cardinal Mazarin. The best example of Anne's statesmanship and the partial change in her heart towards her native Spain is seen in her keeping of one of Richelieu's men, the Chancellor of France Pierre Séguier, in his post. Séguier was the pers
An aerial telescope is a type of long focal length refracting telescope, built in the second half of the 17th century, that did not use a tube. Instead, the objective was mounted on a pole, tower, building or other structure on a swivel ball-joint; the observer stood on the ground and held the eyepiece, connected to the objective by a string or connecting rod. By holding the string tight and maneuvering the eyepiece, the observer could aim the telescope at objects in the sky; the idea for this type of telescope may have originated in the late 17th century with the Dutch mathematician and physicist Christiaan Huygens and his brother Constantijn Huygens, Jr. though it is not clear if they invented it. Telescopes built in the 17th and early 18th century used single element non-achromatic objective lenses that suffered from interfering rainbow halos introduced by the non-uniform refractive properties of single glass lenses; this degraded the quality of the images. Telescope makers from that era found that long focal length objectives had no appreciable chromatic aberration.
They realized that when they doubled the diameter of their objectives they had to make the objective's focal length 4 times as long to achieve the same amount of minimal chromatic aberration. As the objective diameter of these refracting telescopes was increased to gather more light and resolve finer detail they began to have focal lengths as long as 150 feet. Besides having long tubes, these telescopes needed scaffolding or long masts and cranes to hold them up, their value as research tools was minimal since the telescope's support frame and tube flexed and vibrated in the slightest breeze and sometimes collapsed altogether. Around 1675 the brothers Christiaan and Constantijn Huygens decided to accommodate the long focal length objectives they were creating by eliminating the tube altogether. In the Huygens' "aerial" telescope the objective was mounted inside a short iron tube mounted on a swiveling ball-joint on top of an adjustable mast; the eyepiece was mounted in another short tube, the two tubes were kept aligned by a taut connecting string.
Christiaan Huygens published designs for these tubeless "aerial telescopes" in his 1684 book Astroscopia Compendiaria, their invention has been attributed to him and his brother Constantijn, although similar designs were used by Adrien Auzout. The Huygens contrived some ingenious arrangements for aiming these "aerial telescopes" at an object visible in the night sky; the telescope could be aimed at bright objects such as planets by looking for their image cast on a white pasteboard ring or oiled translucent paper screen and centering them in the eyepiece. Fainter objects could be found by looking for the reflection of a lamp held in the observer's hand being bounced back by the objective and centering that reflection on the object. Other contrivances for the same purpose are described by Philippe de la Hire and by Nicolaas Hartsoeker; the objectives for aerial telescopes sometimes had long focal lengths. Christiaan Huygens states that in 1686 he and his brother made objectives of 8 inch and 8.5 inch diameter and 170 and 210 ft focal length, respectively.
Constantijn Huygens, Jr. presented a 7.5 inch diameter 123 ft focal length objective to the Royal Society of London in 1690. Adrien Auzout and others made telescopes of from 300 to 600 ft focal length, Auzout proposed a huge aerial telescope 1,000 ft in length that he would use "to observe animals on the Moon". Astronomer Giovanni Domenico Cassini had the wooden Marly Tower built as part of the Machine de Marly to lift water for the reservoirs and fountains at the Gardens of Versailles, moved to the grounds of the Paris Observatory. On this tower he mounted long tubed telescopes and the objectives of aerial telescopes made for him by the Italian optician Giuseppe Campani. In 1684 he used one of his aerial telescopes to find two satellites of Saturn. James Bradley, on December 27, 1722, measured the diameter of Venus with an aerial telescope whose objective had a focal length of 212 ft. Francesco Bianchini tried to map the surface of that same planet and deduce its rotational period in Rome in 1726 using a 2.6" 100 foot focal length aerial telescope.
The extreme difficulty of using these long focal length telescopes led astronomers to develop alternative designs. One was the reflecting telescope. In 1721 John Hadley showed a Newtonian reflecting telescope to the British Royal Society with 6 inch in diameter mirror; the instrument was examined by Society members James Pound and James Bradley who compared its performance to the 7.5 inch diameter aerial telescope built by Constantijn Huygens, Jr. that the Society had in their collection. In the comparison they noted that the Hadley reflector "will bear such a charge as to make it magnify the object as many times as the latter with its due charge", that it represented objects as distinct, though not altogether so clear and bright as the Huygens aerial telescope; the need for long focal length refracting telescope objectives was eliminated with the invention of the achromatic lens in the middle of the 18th century. In May 2014 a working replica of an aerial Huygens telescope was unveiled at the Old Leiden Observatory in Leiden.
It was commissioned by a Dutch science promoter. It was unveiled during the first annual'Kaiser Lente Lezingen', local astronomy lecture even
Plume (fluid dynamics)
In hydrodynamics, a plume is a column of one fluid moving through another. Several effects control the motion of the fluid, including momentum and buoyancy. Pure jets and pure plumes define flows that are driven by momentum and buoyancy effects, respectively. Flows between these two limits are described as forced plumes or buoyant jets. "Buoyancy is defined as being positive" when, in the absence of other forces or initial motion, the entering fluid would tend to rise. Situations where the density of the plume fluid is greater than its surroundings, but the flow has sufficient initial momentum to carry it some distance vertically, are described as being negatively buoyant; as a plume moves away from its source, it widens because of entrainment of the surrounding fluid at its edges. Plume shapes can be influenced by flow in the ambient fluid; this causes a plume which has been'buoyancy-dominated' to become'momentum-dominated'. A further phenomenon of importance is whether a plume has turbulent flow.
There is a transition from laminar to turbulent as the plume moves away from its source. This phenomenon can be seen in the rising column of smoke from a cigarette; when high accuracy is required, computational fluid dynamics can be employed to simulate plumes, but the results can be sensitive to the turbulence model chosen. CFD is undertaken for rocket plumes, where condensed phase constituents can be present in addition to gaseous constituents; these types of simulations can become quite complex, including afterburning and thermal radiation, ballistic missile launches are detected by sensing hot rocket plumes. Spacecraft managers are sometimes concerned with impingement of attitude control system thruster plumes onto sensitive subsystems like solar arrays and star trackers. Another phenomenon which can be seen in the flow of smoke from a cigarette is that the leading-edge of the flow, or the starting-plume, is quite approximately in the shape of a ring-vortex. Pollutants released to the ground can work their way down into the groundwater, leading to groundwater pollution.
The resulting body of polluted water within an aquifer is called a plume, with its migrating edges called plume fronts. Plumes are used to locate and measure water pollution within the aquifer's total body of water, plume fronts to determine directions and speed of the contamination's spreading in it. Plumes are of considerable importance in the atmospheric dispersion modelling of air pollution. A classic work on the subject of air pollution plumes is that by Gary Briggs. A thermal plume is one, generated by gas rising above heat source; the gas rises. Quite simple modelling will enable many properties of developed, turbulent plumes to be investigated, it is sufficient to assume that the pressure gradient is set by the gradient far from the plume. The distribution of density and velocity across the plume are modelled either with simple Gaussian distributions or else are taken as uniform across the plume; the rate of entrainment into the plume is proportional to the local velocity. Though thought to be a constant, recent work has shown that the entrainment coefficient varies with the local Richardson number.
Typical values for the entrainment coefficient are of about 0.08 for vertical jets and 0.12 for vertical, buoyant plumes whilst for bent-over plumes, the entrainment coefficient is about 0.6. Conservation equations for mass, momentum and buoyancy fluxes are sufficient for a complete description of the flow in many cases, For a simple rising plume these equations predict that the plume will widen at a constant half-angle of about 6 to 15 degrees. Gaussian plume models can be used in several fluid dynamics scenarios to calculate concentration distribution of solutes such as a smoke stack release or contaminant released in a river. Gaussian distributions are established by Fickian diffusion, follow a gaussian distribution. For calculating the expected concentration of a one dimensional instantaneous point source we consider a mass M released at an instantaneous point in time, in a one dimensional domain along x; this will give the following equation: C = M / √ ∗ e x p ( 2 / where M is the mass released at time t=t0 and location x=x0, D is the diffusivity.
This equation makes the following four assumptions: The mass M is released instantaneously. The mass M is released in an infinite domain; the mass spreads only through diffusion. Diffusion does not vary in space
In astronomy, axial tilt known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, the angle between its equatorial plane and orbital plane. It differs from orbital inclination. At an obliquity of 0 degrees, the two axes point in the same direction. Earth's obliquity oscillates between 24.5 degrees on a 41,000-year cycle. Over the course of an orbital period, the obliquity does not change and the orientation of the axis remains the same relative to the background of stars; this causes one pole to be directed more toward the Sun on one side of the orbit, the other pole on the other side—the cause of the seasons on Earth. There are two standard methods of specifying tilt; the International Astronomical Union defines the north pole of a planet as that which lies on Earth's north side of the invariable plane of the Solar System. The IAU uses the right-hand rule to define a positive pole for the purpose of determining orientation. Using this convention, Venus is tilted 177°.
Earth's orbital plane is known as the ecliptic plane, Earth's tilt is known to astronomers as the obliquity of the ecliptic, being the angle between the ecliptic and the celestial equator on the celestial sphere. It is denoted by the Greek letter ε. Earth has an axial tilt of about 23.4°. This value remains about the same relative to a stationary orbital plane throughout the cycles of axial precession, but the ecliptic moves due to planetary perturbations, the obliquity of the ecliptic is not a fixed quantity. At present, it is decreasing at a rate of about 47″ per century. Earth's obliquity may have been reasonably measured as early as 1100 BC in India and China; the ancient Greeks had good measurements of the obliquity since about 350 BC, when Pytheas of Marseilles measured the shadow of a gnomon at the summer solstice. About 830 AD, the Caliph Al-Mamun of Baghdad directed his astronomers to measure the obliquity, the result was used in the Arab world for many years. In 1437, Ulugh Beg determined the Earth's axial tilt as 23°30′17″.
It was believed, during the Middle Ages, that both precession and Earth's obliquity oscillated around a mean value, with a period of 672 years, an idea known as trepidation of the equinoxes. The first to realize this was incorrect was Ibn al-Shatir in the fourteenth century and the first to realize that the obliquity is decreasing at a constant rate was Fracastoro in 1538; the first accurate, western observations of the obliquity were those of Tycho Brahe from Denmark, about 1584, although observations by several others, including al-Ma'mun, al-Tusi, Purbach and Walther, could have provided similar information. Earth's axis remains tilted in the same direction with reference to the background stars throughout a year; this means that one pole will be directed away from the Sun at one side of the orbit, half an orbit this pole will be directed towards the Sun. This is the cause of Earth's seasons. Summer occurs in the Northern hemisphere. Variations in Earth's axial tilt can influence the seasons and is a factor in long-term climate change.
The exact angular value of the obliquity is found by observation of the motions of Earth and planets over many years. Astronomers produce new fundamental ephemerides as the accuracy of observation improves and as the understanding of the dynamics increases, from these ephemerides various astronomical values, including the obliquity, are derived. Annual almanacs are published listing the methods of use; until 1983, the Astronomical Almanac's angular value of the mean obliquity for any date was calculated based on the work of Newcomb, who analyzed positions of the planets until about 1895: ε = 23° 27′ 8.26″ − 46.845″ T − 0.0059″ T2 + 0.00181″ T3where ε is the obliquity and T is tropical centuries from B1900.0 to the date in question. From 1984, the Jet Propulsion Laboratory's DE series of computer-generated ephemerides took over as the fundamental ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated: ε = 23° 26′ 21.448″ − 46.8150″ T − 0.00059″ T2 + 0.001813″ T3where hereafter T is Julian centuries from J2000.0.
JPL's fundamental ephemerides have been continually updated. For instance, the Astronomical Almanac for 2010 specifies: ε = 23° 26′ 21.406″ − 46.836769″ T − 0.0001831″ T2 + 0.00200340″ T3 − 5.76″ × 10−7 T4 − 4.34″ × 10−8 T5These expressions for the obliquity are intended for high precision over a short time span ± several centuries. J. Laskar computed an expression to order T10 good to 0.02″ over 1000 years and several arcseconds over 10,000 years. Ε = 23° 26′ 21.448″ − 4680.93″ t − 1.55″ t2 + 1999.25″ t3 − 51.38″ t4 − 249.67″ t5 − 39.05″ t6 + 7.12″ t7 + 27.87″ t8 + 5.79″ t9 + 2.45″ t10where here t is multiples of 10,000 Julian years from J2000.0. These expressions are for the so-called mean obliquity, that is, the obliquity free from short-term variations. Periodic motions of the Moon and of Earth in its orbit cause much smaller short-period oscillations of the rotation axis of Earth, known as nutation, which add a periodic component to Earth's obliquity; the true or instant
Asteroids are minor planets of the inner Solar System. Larger asteroids have been called planetoids; these terms have been applied to any astronomical object orbiting the Sun that did not resemble a planet-like disc and was not observed to have characteristics of an active comet such as a tail. As minor planets in the outer Solar System were discovered they were found to have volatile-rich surfaces similar to comets; as a result, they were distinguished from objects found in the main asteroid belt. In this article, the term "asteroid" refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There exist millions of asteroids, many thought to be the shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets; the vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects.
Individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups: C-type, M-type, S-type. These were named after and are identified with carbon-rich and silicate compositions, respectively; the sizes of asteroids varies greatly. Asteroids are differentiated from meteoroids. In the case of comets, the difference is one of composition: while asteroids are composed of mineral and rock, comets are composed of dust and ice. Furthermore, asteroids formed closer to the sun; the difference between asteroids and meteoroids is one of size: meteoroids have a diameter of one meter or less, whereas asteroids have a diameter of greater than one meter. Meteoroids can be composed of either cometary or asteroidal materials. Only one asteroid, 4 Vesta, which has a reflective surface, is visible to the naked eye, this only in dark skies when it is favorably positioned. Small asteroids passing close to Earth may be visible to the naked eye for a short time; as of October 2017, the Minor Planet Center had data on 745,000 objects in the inner and outer Solar System, of which 504,000 had enough information to be given numbered designations.
The United Nations declared 30 June as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, Russian Federation, on 30 June 1908. In April 2018, the B612 Foundation reported "It's 100 percent certain we'll be hit, but we're not 100 percent sure when." In 2018, physicist Stephen Hawking, in his final book Brief Answers to the Big Questions, considered an asteroid collision to be the biggest threat to the planet. In June 2018, the US National Science and Technology Council warned that America is unprepared for an asteroid impact event, has developed and released the "National Near-Earth Object Preparedness Strategy Action Plan" to better prepare. According to expert testimony in the United States Congress in 2013, NASA would require at least five years of preparation before a mission to intercept an asteroid could be launched; the first asteroid to be discovered, was considered to be a new planet.
This was followed by the discovery of other similar bodies, with the equipment of the time, appeared to be points of light, like stars, showing little or no planetary disc, though distinguishable from stars due to their apparent motions. This prompted the astronomer Sir William Herschel to propose the term "asteroid", coined in Greek as ἀστεροειδής, or asteroeidēs, meaning'star-like, star-shaped', derived from the Ancient Greek ἀστήρ astēr'star, planet'. In the early second half of the nineteenth century, the terms "asteroid" and "planet" were still used interchangeably. Overview of discovery timeline: 10 by 1849 1 Ceres, 1801 2 Pallas – 1802 3 Juno – 1804 4 Vesta – 1807 5 Astraea – 1845 in 1846, planet Neptune was discovered 6 Hebe – July 1847 7 Iris – August 1847 8 Flora – October 1847 9 Metis – 25 April 1848 10 Hygiea – 12 April 1849 tenth asteroid discovered 100 asteroids by 1868 1,000 by 1921 10,000 by 1989 100,000 by 2005 ~700,000 by 2015 Asteroid discovery methods have improved over the past two centuries.
In the last years of the 18th century, Baron Franz Xaver von Zach organized a group of 24 astronomers to search the sky for the missing planet predicted at about 2.8 AU from the Sun by the Titius-Bode law because of the discovery, by Sir William Herschel in 1781, of the planet Uranus at the distance predicted by the law. This task required that hand-drawn sky charts be prepared for all stars in the zodiacal band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would be spotted; the expected motion of the missing planet was about 30 seconds of arc per hour discernible by observers. The first object, was not discovered by a member of the group, but rather by accident in 1801 by Giuseppe Piazzi, director of the observatory of Palermo in Sicily, he discovered a new star-like object in Taurus and followed the displacement of this object during several nights. That year, Carl Friedrich Gauss used these observations to calculate the orbit of this unknown object, found to be between the planets Mars and Jupiter.
Piazzi named it after Ceres, the Roman goddess of agriculture. Three other asteroids (2 Pallas, 3 Juno, 4 Ves
The Paris Observatory, a research institution of PSL Research University, is the foremost astronomical observatory of France, one of the largest astronomical centres in the world. Its historic building is to be found on the Left Bank of the Seine in central Paris, but most of the staff work on a satellite campus in Meudon, a suburb southwest of Paris. Administratively, it is a grand établissement of the French Ministry of National Education, with a status close to that of a public university, its missions astrophysics. It maintains a radio astronomy observatory at Nançay, it was the home to the International Time Bureau until its dissolution in 1987. The Paris Observatory Library, founded in 1785, provides the researchers with documentation and preserves the ancient books and heritage collections of the institution. Many collections are available on the Paris Observatory digital library, its foundation lies in the ambitions of Jean-Baptiste Colbert to extend France's maritime power and international trade in the 17th century.
Louis XIV promoted its construction, started in 1667 and completed in 1671. It thus predates by a few years the Royal Greenwich Observatory in England, founded in 1675; the architect of the Paris Observatory was Claude Perrault whose brother, was secretary to Colbert and superintendent of public works. Optical instruments were supplied by Giuseppe Campani; the buildings were extended in 1730, 1810, 1834, 1850, 1951. The last extension incorporates the spectacular Meridian Room designed by Jean Prouvé; the world's first national almanac, the Connaissance des temps, was published by the observatory in 1679, using eclipses in Jupiter's satellites to aid sea-farers in establishing longitude. In 1863, the observatory published the first modern weather maps. In 1882, a 33 cm astrographic lens was constructed, an instrument that catalysed what proved to be the over-ambitious international Carte du Ciel project. In November 1913, the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless signals with the United States Naval Observatory to determine the exact difference of longitude between the two institutions.
The Paris Observatory library preserves a great number of original works and letters of the Observatory and well known astronomers. The entire collection - archives, iconography - has been inventoried on Alidade; some of the work is now digitized on the digital library such as Hevelius, Lalande or Delisle letters. Among other, are to be found: Administrativ documents Scientific observations Scientifc work of Giovanni Domenico Cassini Scientific work of Jacques Cassini Scientific work of Charles Messier Annual reports from 1878 to 1940 Numerous images of instruments and persons The Meudon great refractor was a 83 cm aperture refractor, which with September 20, 1909 observations by E. M. Antoniadi helped disprove the Mars canals theory, it was a double telescope completed in 1891, with secondary having 62 cm aperture lens for photography. It was one of the largest active telescopes in Europe; the title of Director of the Observatory was given for the first time to César-François Cassini de Thury by a Royal brevet dated November 12, 1771.
However, the important role played by his grandfather and father in this institution during its first century gives them somewhat the role of director. Solar Observatory Tower Meudon Chateau de Meudon LESIA space and astrophysics instrumentation research laboratory Nançay radio telescope Also known as the Observatoire du Pic de Château Renard, the Observatoire de Saint-Véran was built in 1974 on top of the Pic de Château Renard, on the commune of Saint-Véran in the Haut Queyras. A coronograph was in operation there for ten years. Nowadays, the AstroQueyras amateur astronomy association operates the facility, using a 60 cm telescope on loan from the Observatoire de Haute Provence. Numerous asteroids have been discovered there. "Paris Observatory", Encyclopædia Britannica, Deluxe CDROM edition Aubin, D.. "The fading star of the Paris Observatory in the nineteenth century: astronomers' urban culture of circulation and observation". Osiris. 18: 79–100. Doi:10.1086/649378. Guinot, B.. "History of the Bureau International de l'Heure".
Polar Motion: Historical and Scientific problems. Pp. 175–184. Bibcode:2000ASPC..208..175G. Paris Observatory Location in Paris Inventory of astronomy heritage Digital library for astronomy archives Publications of the Observatoire de Paris in Gallica, the digital library of the BnF