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83-546: Drömling lies in a flat hollow measuring about 15 to 20 kilometres across and surrounding by a 60-metre contour . It is a wider section of the Breslau-Magdeburg-Bremen glacial valley. In broad terms it stretches from Wolfsburg-Vorsfelde in the west to Calvörde in the east and from Klötze in the north to Oebisfelde in the south. To the west the geest ridges of the Vorsfelder Werder border on

166-463: A Derbyshire family and was a wealthy soap-maker in London. As a child, Halley was very interested in mathematics. He studied at St Paul's School , where he developed his initial interest in astronomy, and was elected captain of the school in 1671. The following year, Halley's mother, Anne (probably née Robinson) died. In July 1673, he began studying at The Queen's College, Oxford . Halley took

249-436: A choropleth map . In meteorology, the word isopleth is used for any type of contour line. Meteorological contour lines are based on interpolation of the point data received from weather stations and weather satellites . Weather stations are seldom exactly positioned at a contour line (when they are, this indicates a measurement precisely equal to the value of the contour). Instead, lines are drawn to best approximate

332-545: A diving bell , a device in which the atmosphere was replenished by way of weighted barrels of air sent down from the surface. In a demonstration, Halley and five companions dived to 60 feet (18 m) in the River Thames , and remained there for over an hour and a half. Halley's bell was of little use for practical salvage work, as it was very heavy, but he made improvements to it over time, later extending his underwater exposure time to over 4 hours. Halley suffered one of

415-441: A map describing the intersection of a real or hypothetical surface with one or more horizontal planes. The configuration of these contours allows map readers to infer the relative gradient of a parameter and estimate that parameter at specific places. Contour lines may be either traced on a visible three-dimensional model of the surface , as when a photogrammetrist viewing a stereo-model plots elevation contours, or interpolated from

498-477: A map of the southern stars. Oxford would not allow Halley to return because he had violated his residency requirements when he left for Saint Helena. He appealed to Charles II, who signed a letter requesting that Halley be unconditionally awarded his Master of Arts degree, which the college granted on 3 December 1678. Just a few days before, Halley had been elected as a fellow of the Royal Society , at

581-709: A word without a repeated letter . As late as 1944, John K. Wright still preferred isogram , but it never attained wide usage. During the early 20th century, isopleth ( πλῆθος , plethos , 'amount') was being used by 1911 in the United States, while isarithm ( ἀριθμός , arithmos , 'number') had become common in Europe. Additional alternatives, including the Greek-English hybrid isoline and isometric line ( μέτρον , metron , 'measure'), also emerged. Despite attempts to select

664-691: A captain in the Royal Navy , recommissioned the Paramour on 24 August 1699 and sailed again in September 1699 to make extensive observations on the conditions of terrestrial magnetism . This task he accomplished in a second Atlantic voyage which lasted until 6 September 1700, and extended from 52 degrees north to 52 degrees south. The results were published in General Chart of the Variation of

747-411: A constant pressure surface chart. Isohypse and isoheight are simply known as lines showing equal pressure on a map. An isotherm (from Ancient Greek θέρμη (thermē)  'heat') is a line that connects points on a map that have the same temperature . Therefore, all points through which an isotherm passes have the same or equal temperatures at the time indicated. An isotherm at 0 °C

830-406: A constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional graph of the function f ( x , y ) {\displaystyle f(x,y)} parallel to the ( x , y ) {\displaystyle (x,y)} -plane. More generally, a contour line for a function of two variables is a curve connecting points where

913-417: A contour map is the difference in elevation between successive contour lines. The gradient of the function is always perpendicular to the contour lines. When the lines are close together the magnitude of the gradient is large: the variation is steep. A level set is a generalization of a contour line for functions of any number of variables. Contour lines are curved, straight or a mixture of both lines on

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996-407: A curve of constant electric potential . Whether crossing an equipotential line represents ascending or descending the potential is inferred from the labels on the charges. In three dimensions, equipotential surfaces may be depicted with a two dimensional cross-section, showing equipotential lines at the intersection of the surfaces and the cross-section. The general mathematical term level set

1079-576: A doubt of its being round; others no less knowing imagin'd all they were not acquainted with, desart and uninhabitable. But now geography and hydrography have receiv'd some perfection by the pains of so many mariners and travelers, who to evince the rotundity of the earth and water, have sail’d and travell'd round it, as has been here made appear; to show there is no part uninhabitable, unless the frozen polar regions, have visited all other countries, tho never so remote, which they have found well peopl'd, and most of them rich and delightful…. Astronomy has receiv'd

1162-431: A given location and is used in the generation of isochrone maps . An isotim shows equivalent transport costs from the source of a raw material, and an isodapane shows equivalent cost of travel time. Contour lines are also used to display non-geographic information in economics. Indifference curves (as shown at left) are used to show bundles of goods to which a person would assign equal utility. An isoquant (in

1245-443: A grand expansion of European knowledge of the world: What was cosmography before these discoveries, but an imperfect fragment of a science, scarce deserving so good a name? When all the known world was only Europe, a small part of Africk, and the lesser portion of Asia; so that of this terraqueous globe not one sixth part had ever been seen or heard of. Nay so great was the ignorance of man in this particular, that learned persons made

1328-828: A line of constant annual variation of magnetic declination . An isoclinic line connects points of equal magnetic dip , and an aclinic line is the isoclinic line of magnetic dip zero. An isodynamic line (from δύναμις or dynamis meaning 'power') connects points with the same intensity of magnetic force. Besides ocean depth, oceanographers use contour to describe diffuse variable phenomena much as meteorologists do with atmospheric phenomena. In particular, isobathytherms are lines showing depths of water with equal temperature, isohalines show lines of equal ocean salinity, and isopycnals are surfaces of equal water density. Various geological data are rendered as contour maps in structural geology , sedimentology , stratigraphy and economic geology . Contour maps are used to show

1411-426: A picture of the major thermodynamic factors in a weather system. An isobar (from Ancient Greek βάρος (baros)  'weight') is a line of equal or constant pressure on a graph, plot, or map; an isopleth or contour line of pressure. More accurately, isobars are lines drawn on a map joining places of equal average atmospheric pressure reduced to sea level for a specified period of time. In meteorology ,

1494-440: A point; this distinction has since been followed generally. An example of an isopleth is population density , which can be calculated by dividing the population of a census district by the surface area of that district. Each calculated value is presumed to be the value of the variable at the centre of the area, and isopleths can then be drawn by a process of interpolation . The idea of an isopleth map can be compared with that of

1577-489: A single standard, all of these alternatives have survived to the present. When maps with contour lines became common, the idea spread to other applications. Perhaps the latest to develop are air quality and noise pollution contour maps, which first appeared in the United States in approximately 1970, largely as a result of national legislation requiring spatial delineation of these parameters. Contour lines are often given specific names beginning with " iso- " according to

1660-421: A specific time interval, and katallobars , lines joining points of equal pressure decrease. In general, weather systems move along an axis joining high and low isallobaric centers. Isallobaric gradients are important components of the wind as they increase or decrease the geostrophic wind . An isopycnal is a line of constant density. An isoheight or isohypse is a line of constant geopotential height on

1743-663: A twenty-four-foot (7.3 m) long telescope with him, apparently paid for by his father. While still an undergraduate, Halley published papers on the Solar System and sunspots . In March 1675, he wrote to John Flamsteed , the Astronomer Royal (England's first), telling him that the leading published tables on the positions of Jupiter and Saturn were erroneous, as were some of Tycho Brahe 's star positions. In 1676, Flamsteed helped Halley publish his first paper, titled "A Direct and Geometrical Method of Finding

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1826-461: A variety of scales, from large-scale engineering drawings and architectural plans, through topographic maps and bathymetric charts , up to continental-scale maps. "Contour line" is the most common usage in cartography , but isobath for underwater depths on bathymetric maps and isohypse for elevations are also used. In cartography, the contour interval is the elevation difference between adjacent contour lines. The contour interval should be

1909-787: A vertical section. In 1801, the chief of the French Corps of Engineers, Haxo , used contour lines at the larger scale of 1:500 on a plan of his projects for Rocca d'Anfo , now in northern Italy, under Napoleon . By around 1843, when the Ordnance Survey started to regularly record contour lines in Great Britain and Ireland , they were already in general use in European countries. Isobaths were not routinely used on nautical charts until those of Russia from 1834, and those of Britain from 1838. As different uses of

1992-446: Is a contour line for a variable which measures direction. In meteorology and in geomagnetics, the term isogon has specific meanings which are described below. An isocline ( κλίνειν , klinein , 'to lean or slope') is a line joining points with equal slope. In population dynamics and in geomagnetics, the terms isocline and isoclinic line have specific meanings which are described below. A curve of equidistant points

2075-452: Is a line joining points with constant wind speed. In meteorology, the term isogon refers to a line of constant wind direction. An isopectic line denotes equal dates of ice formation each winter, and an isotac denotes equal dates of thawing. Contours are one of several common methods used to denote elevation or altitude and depth on maps . From these contours, a sense of the general terrain can be determined. They are used at

2158-438: Is a line of equal or constant dew point . An isoneph is a line indicating equal cloud cover. An isochalaz is a line of constant frequency of hail storms, and an isobront is a line drawn through geographical points at which a given phase of thunderstorm activity occurred simultaneously. Snow cover is frequently shown as a contour-line map. An isotach (from Ancient Greek ταχύς (tachus)  'fast')

2241-522: Is a line of equal temperature beneath the Earth's surface. An isohyet or isohyetal line (from Ancient Greek ὑετός (huetos)  'rain') is a line on a map joining points of equal rainfall in a given period. A map with isohyets is called an isohyetal map . An isohume is a line of constant relative humidity , while an isodrosotherm (from Ancient Greek δρόσος (drosos)  'dew' and θέρμη (therme)  'heat')

2324-485: Is a set of points all at the same distance from a given point , line , or polyline . In this case the function whose value is being held constant along a contour line is a distance function . In 1944, John K. Wright proposed that the term isopleth be used for contour lines that depict a variable which cannot be measured at a point, but which instead must be calculated from data collected over an area, as opposed to isometric lines for variables that could be measured at

2407-616: Is called the freezing level . The term lignes isothermes (or lignes d'égale chaleur) was coined by the Prussian geographer and naturalist Alexander von Humboldt , who as part of his research into the geographical distribution of plants published the first map of isotherms in Paris, in 1817. According to Thomas Hankins, the Scottish engineer William Playfair 's graphical developments greatly influenced Alexander von Humbolt's invention of

2490-508: Is especially important in riparian zones. An isoflor is an isopleth contour connecting areas of comparable biological diversity. Usually, the variable is the number of species of a given genus or family that occurs in a region. Isoflor maps are thus used to show distribution patterns and trends such as centres of diversity. In economics , contour lines can be used to describe features which vary quantitatively over space. An isochrone shows lines of equivalent drive time or travel time to

2573-403: Is found on a map dated 1584 of the river Spaarne , near Haarlem , by Dutchman Pieter Bruinsz. In 1701, Edmond Halley used such lines (isogons) on a chart of magnetic variation. The Dutch engineer Nicholas Cruquius drew the bed of the river Merwede with lines of equal depth (isobaths) at intervals of 1 fathom in 1727, and Philippe Buache used them at 10-fathom intervals on a chart of

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2656-454: Is indicated on maps with isoplats . Some of the most widespread applications of environmental science contour maps involve mapping of environmental noise (where lines of equal sound pressure level are denoted isobels ), air pollution , soil contamination , thermal pollution and groundwater contamination. By contour planting and contour ploughing , the rate of water runoff and thus soil erosion can be substantially reduced; this

2739-461: Is not to Halley's credit that he failed to acknowledge Gregory's priority in this matter. In 1717–18 he discovered the proper motion of the "fixed" stars (publishing this in 1718) by comparing his astrometric measurements with those given in Ptolemy's Almagest . Arcturus and Sirius were two noted to have moved significantly, the latter having progressed 30 arc minutes (about the diameter of

2822-470: Is often used to describe the full collection of points having a particular potential, especially in higher dimensional space. In the study of the Earth's magnetic field , the term isogon or isogonic line refers to a line of constant magnetic declination , the variation of magnetic north from geographic north. An agonic line is drawn through points of zero magnetic declination. An isoporic line refers to

2905-412: Is shown in all areas. Conversely, for an island which consists of a plateau surrounded by steep cliffs, it is possible to use smaller intervals as the height increases. An isopotential map is a measure of electrostatic potential in space, often depicted in two dimensions with the electrostatic charges inducing that electric potential . The term equipotential line or isopotential line refers to

2988-484: The Bodleian Library at Oxford. He also completed a new translation of the first four books from the original Greek that had been started by the late David Gregory . He published these along with his own reconstruction of Book VIII in the first complete Latin edition in 1710. The same year, he received an honorary degree of doctor of laws from Oxford. In 1716, Halley suggested a high-precision measurement of

3071-623: The English Channel that was prepared in 1737 and published in 1752. Such lines were used to describe a land surface (contour lines) in a map of the Duchy of Modena and Reggio by Domenico Vandelli in 1746, and they were studied theoretically by Ducarla in 1771, and Charles Hutton used them in the Schiehallion experiment . In 1791, a map of France by J. L. Dupain-Triel used contour lines at 20-metre intervals, hachures, spot-heights and

3154-557: The aurora borealis . He suggested, "Auroral rays are due to particles, which are affected by the magnetic field, the rays parallel to Earth's magnetic field." In 1693 Halley published an article on life annuities , which featured an analysis of age-at-death on the basis of the Breslau statistics Caspar Neumann had been able to provide. This article allowed the British government to sell life annuities at an appropriate price based on

3237-514: The barometric pressures shown are reduced to sea level , not the surface pressures at the map locations. The distribution of isobars is closely related to the magnitude and direction of the wind field, and can be used to predict future weather patterns. Isobars are commonly used in television weather reporting. Isallobars are lines joining points of equal pressure change during a specific time interval. These can be divided into anallobars , lines joining points of equal pressure increase during

3320-664: The Aphelia, Eccentricities, and Proportions of the Primary Planets, Without Supposing Equality in Angular Motion", about planetary orbits , in Philosophical Transactions of the Royal Society . Influenced by Flamsteed's project to compile a catalogue of stars of the northern celestial hemisphere , Halley proposed to do the same for the southern sky , dropping out of school to do so. He chose

3403-679: The Astronomer Royal, John Flamsteed, and the Anglican Church questioned his religious views, largely on the grounds that he had doubted the Earth's age as given in the Bible . After Flamsteed wrote to Newton to rally support against Halley, Newton wrote back in hopes of reconciliation, but was unsuccessful. Halley's candidacy was opposed by both the Archbishop of Canterbury , John Tillotson , and Bishop Stillingfleet , and

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3486-521: The Astronomy of Comets ); in this, he stated his belief that the comet sightings of 1456, 1531, 1607, and 1682 were of the same comet, and that it would return in 1758. Halley did not live to witness the comet's return, but when it did, the comet became generally known as Halley's Comet. By 1706 Halley had learned Arabic and completed the translation started by Edward Bernard of Books V–VII of Apollonius 's Conics from copies found at Leiden and

3569-689: The Compass (1701). This was the first such chart to be published and the first on which isogonic , or Halleyan, lines appeared. The use of such lines inspired later ideas such as those of isotherms by Alexander von Humboldt in his maps. In 1701, Halley made a third and final voyage on the Paramour to study the tides of the English Channel . In 1702, he was dispatched by Queen Anne on diplomatic missions to other European leaders. The preface to Awnsham and John Churchill 's collection of voyages and travels (1704), supposedly written by John Locke or by Halley, valourised expeditions such as these as part of

3652-467: The Drömling. Drömling extends over the following districts: Salzwedel , Börde , Gifhorn , Wolfsburg and Helmstedt . 52°28′57″N 11°7′52″E  /  52.48250°N 11.13111°E  / 52.48250; 11.13111 Contour line A contour line (also isoline , isopleth , isoquant or isarithm ) of a function of two variables is a curve along which the function has

3735-463: The Sun. Upon his return to England, he was made a fellow of the Royal Society , and with the help of King Charles II , was granted a master's degree from Oxford . Halley encouraged and helped fund the publication of Isaac Newton 's influential Philosophiæ Naturalis Principia Mathematica (1687). From observations Halley made in September 1682, he used Newton's law of universal gravitation to compute

3818-497: The accuracy of his observations; Halley stayed with Hevelius and checked his observations, finding that they were quite precise. By 1681, Giovanni Domenico Cassini had told Halley of his theory that comets were objects in orbit. In September 1682, Halley carried out a series of observations of what became known as Halley's Comet ; his name became associated with it because of his work on its orbit and predicting its return in 1758 (which he did not live to see). In early 1686, Halley

3901-450: The addition of many constellations never seen before. Natural and moral history is embelish'd with the most beneficial increase of so many thousands of plants it had never before receiv'd, so many drugs and spices, such variety of beasts, birds and fishes, such rarities in minerals, mountains and waters, such unaccountable diversity of climates and men, and in them of complexions, tempers, habits, manners, politicks, and religions…. To conclude,

3984-578: The age of 22. In 1679, he published Catalogus Stellarum Australium ('A catalogue of the stars of the South'), which includes his map and descriptions of 341 stars. Robert Hooke presented the catalogue to the Royal Society. In mid-1679, Halley went to Danzig ( Gdańsk ) on behalf of the Society to help resolve a dispute: because astronomer Johannes Hevelius ' observing instruments were not equipped with telescopic sights , Flamsteed and Hooke had questioned

4067-415: The age of the purchaser. Halley's work strongly influenced the development of actuarial science . The construction of the life-table for Breslau, which followed more primitive work by John Graunt , is now seen as a major event in the history of demography . The Royal Society censured Halley for suggesting in 1694 that the story of Noah's flood might be an account of a cometary impact. A similar theory

4150-683: The behest of King William III , Halley was given command of the Paramour , a 52 feet (16 m) pink , so that he could carry out investigations in the South Atlantic into the laws governing the variation of the compass , as well as to refine the coordinates of the English colonies in the Americas . On 19 August 1698, he took command of the ship and, in November 1698, sailed on what was

4233-452: The below ground surface of geologic strata , fault surfaces (especially low angle thrust faults ) and unconformities . Isopach maps use isopachs (lines of equal thickness) to illustrate variations in thickness of geologic units. In discussing pollution, density maps can be very useful in indicating sources and areas of greatest contamination. Contour maps are especially useful for diffuse forms or scales of pollution. Acid precipitation

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4316-595: The cause of atmospheric motions. He also established the relationship between barometric pressure and height above sea level. His charts were an important contribution to the emerging field of information visualisation . Halley spent most of his time on lunar observations, but was also interested in the problems of gravity . One problem that attracted his attention was the proof of Kepler's laws of planetary motion . In August 1684, he went to Cambridge to discuss this with Isaac Newton , much as John Flamsteed had done four years earlier, only to find that Newton had solved

4399-638: The distance between the Earth and the Sun by timing the transit of Venus . In doing so, he was following the method described by James Gregory in Optica Promota (in which the design of the Gregorian telescope is also described). It is reasonable to assume Halley possessed and had read this book given that the Gregorian design was the principal telescope design used in astronomy in Halley's day. It

4482-443: The earliest being the one accepted. These dates were wrong by thousands of years, but the idea that scientific methods could be used to date ancient monuments was revolutionary in its day. Halley succeeded John Flamsteed in 1720 as Astronomer Royal, a position Halley held until his death in 1742 at the age of 85. He was buried in the graveyard of the old church of St Margaret's, Lee (since rebuilt), at Lee Terrace, Blackheath . He

4565-411: The earliest recorded cases of middle ear barotrauma . That same year, at a meeting of the Royal Society, Halley introduced a rudimentary working model of a magnetic compass using a liquid-filled housing to damp the swing and wobble of the magnetised needle. In 1691, Halley sought the post of Savilian Professor of Astronomy at Oxford. While a candidate for the position, Halley faced the animosity of

4648-437: The empire of Europe is now extended to the utmost bounds of the earth, where several of its nations have conquests and colonies. These and many more are the advantages drawn from the labours of those, who expose themselves to the dangers of the vast ocean, and of unknown nations; which those who sit still at home abundantly reap in every kind: and the relation of one traveler is an incentive to stir up another to imitate him, whilst

4731-428: The estimated surface elevations , as when a computer program threads contours through a network of observation points of area centroids. In the latter case, the method of interpolation affects the reliability of individual isolines and their portrayal of slope , pits and peaks. The idea of lines that join points of equal value was rediscovered several times. The oldest known isobath (contour line of constant depth)

4814-469: The first purely scientific voyage by an English naval vessel. Unfortunately problems of insubordination arose over questions of Halley's competence to command a vessel. Halley returned the ship to England to proceed against officers in July 1699. The result was a mild rebuke for his men, and dissatisfaction for Halley, who felt the court had been too lenient. Halley thereafter received a temporary commission as

4897-508: The first telescopic catalogue of the southern sky, and observed a transit of Mercury across the Sun. Focusing on this latter observation, Halley realised that observing the solar parallax of a planet—more ideally using the transit of Venus , which would not occur within his lifetime—could be used to trigonometrically determine the distances between Earth, Venus, and the Sun. Halley returned to England in May 1678, and used his data to produce

4980-400: The function has the same particular value. In cartography , a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level . A contour map is a map illustrated with contour lines, for example a topographic map , which thus shows valleys and hills, and the steepness or gentleness of slopes. The contour interval of

5063-456: The image at right) is a curve of equal production quantity for alternative combinations of input usages , and an isocost curve (also in the image at right) shows alternative usages having equal production costs. In political science an analogous method is used in understanding coalitions (for example the diagram in Laver and Shepsle's work ). In population dynamics , an isocline shows

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5146-429: The isotherm. Humbolt later used his visualizations and analyses to contradict theories by Kant and other Enlightenment thinkers that non-Europeans were inferior due to their climate. An isocheim is a line of equal mean winter temperature, and an isothere is a line of equal mean summer temperature. An isohel ( ἥλιος , helios , 'Sun') is a line of equal or constant solar radiation . An isogeotherm

5229-442: The locations of exact values, based on the scattered information points available. Meteorological contour maps may present collected data such as actual air pressure at a given time, or generalized data such as average pressure over a period of time, or forecast data such as predicted air pressure at some point in the future. Thermodynamic diagrams use multiple overlapping contour sets (including isobars and isotherms) to present

5312-427: The map key. Usually contour intervals are consistent throughout a map, but there are exceptions. Sometimes intermediate contours are present in flatter areas; these can be dashed or dotted lines at half the noted contour interval. When contours are used with hypsometric tints on a small-scale map that includes mountains and flatter low-lying areas, it is common to have smaller intervals at lower elevations so that detail

5395-520: The mint was profiting from it. In 1698, the Czar of Russia (later known as Peter the Great ) was on a visit to England, and hoped Newton would be available to entertain him. Newton sent Halley in his place. He and the Czar bonded over science and brandy. According to one disputed account, when both of them were drunk one night, Halley jovially pushed the Czar around Deptford in a wheelbarrow. In 1698, at

5478-437: The moon) southwards in 1800 years. In 1720, together with his friend the antiquarian William Stukeley , Halley participated in the first attempt to scientifically date Stonehenge . Assuming that the monument had been laid out using a magnetic compass, Stukeley and Halley attempted to calculate the perceived deviation introducing corrections from existing magnetic records, and suggested three dates (460 BC, AD 220 and AD 920),

5561-517: The name should be pronounced in the context of the astronomer or the comet. The alternative / ˈ h eɪ l i / is much more common in the latter context than it is when used as a modern surname. Colin Ronan , one of Halley's biographers, preferred / ˈ h ɔː l i / . Contemporary accounts spell his name Hailey, Hayley, Haley, Haly, Halley, Hawley and Hawly , and presumably pronunciations varied similarly. As for his given name, although

5644-482: The nature of the variable being mapped, although in many usages the phrase "contour line" is most commonly used. Specific names are most common in meteorology, where multiple maps with different variables may be viewed simultaneously. The prefix "' iso- " can be replaced with " isallo- " to specify a contour line connecting points where a variable changes at the same rate during a given time period. An isogon (from Ancient Greek γωνία (gonia)  'angle')

5727-471: The orbit of comet Kirch, based on Flamsteed's observations in 1680–1681. Although he was to accurately calculate the orbit of the comet of 1682, he was inaccurate in his calculations of the orbit of comet Kirch. They indicated a periodicity of 575 years, thus appearing in the years 531 and 1106, and presumably heralding the death of Julius Caesar in a like fashion in 45 BC. It is now known to have an orbital period of circa 10,000 years. In 1691, Halley built

5810-569: The periodicity of Halley's Comet in his 1705 Synopsis of the Astronomy of Comets . It was named after him upon its predicted return in 1758, which he did not live to see. Beginning in 1698, Halley made sailing expeditions and made observations on the conditions of terrestrial magnetism . In 1718, he discovered the proper motion of the "fixed" stars . Halley was born in Haggerston in Middlesex . His father, Edmond Halley Sr., came from

5893-496: The persistent misconception that Halley received a knighthood , it is not the case. The idea can be tracked back to American astronomical texts such as William Augustus Norton 's 1839 An Elementary Treatise on Astronomy , possibly due to Halley's royal occupations and connections to Sir Isaac Newton . Halley married Mary Tooke in 1682 and settled in Islington . The couple had three children. There are three pronunciations of

5976-599: The post went instead to David Gregory , who had Newton's support. In 1692, Halley put forth the idea of a hollow Earth consisting of a shell about 500 miles (800 km) thick, two inner concentric shells and an innermost core. He suggested that atmospheres separated these shells, and that each shell had its own magnetic poles , with each sphere rotating at a different speed. Halley proposed this scheme to explain anomalous compass readings. He envisaged each inner region as having an atmosphere and being luminous (and possibly inhabited), and speculated that escaping gas caused

6059-650: The problem, at the instigation of Flamsteed with regard to the orbit of comet Kirch , without publishing the solution. Halley asked to see the calculations and was told by Newton that he could not find them, but promised to redo them and send them on later, which he eventually did, in a short treatise titled On the motion of bodies in an orbit . Halley recognised the importance of the work and returned to Cambridge to arrange its publication with Newton, who instead went on to expand it into his Philosophiæ Naturalis Principia Mathematica published at Halley's expense in 1687. Halley's first calculations with comets were thereby for

6142-512: The rest of mankind, in their accounts without stirring a foot, compass the earth and seas, visit all countries, and converse with all nations. In November 1703, Halley was appointed Savilian Professor of Geometry at the University of Oxford, his theological enemies, John Tillotson and Bishop Stillingfleet having died. In 1705, applying historical astronomy methods, he published the paper Astronomiae cometicae synopsis ( A Synopsis of

6225-407: The same over a single map. When calculated as a ratio against the map scale, a sense of the hilliness of the terrain can be derived. There are several rules to note when interpreting terrain contour lines: Of course, to determine differences in elevation between two points, the contour interval, or distance in altitude between two adjacent contour lines, must be known, and this is normally stated in

6308-1079: The set of population sizes at which the rate of change, or partial derivative, for one population in a pair of interacting populations is zero. In statistics, isodensity lines or isodensanes are lines that join points with the same value of a probability density . Isodensanes are used to display bivariate distributions . For example, for a bivariate elliptical distribution the isodensity lines are ellipses . Various types of graphs in thermodynamics , engineering, and other sciences use isobars (constant pressure), isotherms (constant temperature), isochors (constant specific volume), or other types of isolines, even though these graphs are usually not related to maps. Such isolines are useful for representing more than two dimensions (or quantities) on two-dimensional graphs. Common examples in thermodynamics are some types of phase diagrams . Edmond Halley Edmond (or Edmund ) Halley FRS ( / ˈ h æ l i / ; 8 November [ O.S. 29 October] 1656 – 25 January 1742 [ O.S. 14 January 1741])

6391-424: The south Atlantic island of Saint Helena (west of Africa), from which he would be able to observe not only the southern stars, but also some of the northern stars with which to cross-reference them. King Charles II supported his endeavour. Halley sailed to the island in late 1676, then set up an observatory with a large sextant with telescopic sights. Over a year, he made observations with which he would produce

6474-496: The surname Halley . These are / ˈ h æ l i / , / ˈ h eɪ l i / , and / ˈ h ɔː l i / . As a personal surname, the most common pronunciation in the 21st century, both in Great Britain and in the United States, is / ˈ h æ l i / (rhymes with "valley"). This is the personal pronunciation used by most Halleys living in London today. This is useful guidance but does not, of course, tell us how

6557-440: The technique were invented independently, cartographers began to recognize a common theme, and debated what to call these "lines of equal value" generally. The word isogram (from Ancient Greek ἴσος (isos)  'equal' and γράμμα (gramma)  'writing, drawing') was proposed by Francis Galton in 1889 for lines indicating equality of some physical condition or quantity, though isogram can also refer to

6640-488: Was an English astronomer , mathematician and physicist . He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720. From an observatory he constructed on Saint Helena in 1676–77, Halley catalogued the southern celestial hemisphere and recorded a transit of Mercury across the Sun. He realised that a similar transit of Venus could be used to determine the distances between Earth, Venus, and

6723-578: Was elected to the Royal Society's new position of secretary, requiring him to give up his fellowship and manage correspondence and meetings, as well as edit the Philosophical Transactions . Also in 1686, Halley published the second part of the results from his Helenian expedition, being a paper and chart on trade winds and monsoons . The symbols he used to represent trailing winds still exist in most modern day weather chart representations. In this article he identified solar heating as

6806-530: Was independently suggested three centuries later, but is generally rejected by geologists. In 1696, Newton was appointed as warden of the Royal Mint and nominated Halley as deputy comptroller of the Chester mint. Halley spent two years supervising coin production. While there, he caught two clerks pilfering precious metals. He and the local warden spoke out about the scheme, unaware that the local master of

6889-795: Was interred in the same vault as the Astronomer Royal John Pond ; the unmarked grave of the Astronomer Royal Nathaniel Bliss is nearby. His original tombstone was transferred by the Admiralty when the original Lee church was demolished and rebuilt – it can be seen today on the southern wall of the Camera Obscura at the Royal Observatory, Greenwich. His marked grave can be seen at St Margaret's Church, Lee Terrace. Despite

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