A timeline is a display of a list of events in chronological order. It is a graphic design showing a long bar labelled with dates paralleling it, contemporaneous events. Timelines can use any suitable scale representing time, suiting data; this timescale is dependent on the events in the timeline. A timeline of evolution can be over millions of years, whereas a timeline for the day of the September 11 attacks can take place over minutes, that of an explosion over milliseconds. While many timelines use a linear timescale -- where large or small timespans are relevant -- logarithmic timelines entail a logarithmic scale of time. There are different types of timelines Text timelines, labeled as text Number timelines, the labels are numbers line graphs Interactive, zoomableThere are many methods of visualizations for timelines. Timelines were static images and drawn or printed on paper. Timelines relied on graphic design, the ability of the artist to visualize the data. Timelines, no longer constrained by previous space and functional limitations, are now digital and interactive created with computer software.
ChronoZoom is an example of computer-aided interactive timeline software. Timelines are used in education to help students and researchers with understanding the order or chronology of historical events and trends for a subject; when showing time on a specific scale on an axis, a timeline can be used to visualize time lapses between events and the simultaneity or overlap of spans and events. Timelines are useful for studying history, as they convey a sense of change over time. Wars and social movements are shown as timelines. Timelines are useful for biographies. Examples include: Timeline of the civil rights movement Timeline of European exploration Timeline of imperialism Timeline of Solar System exploration Timeline of United States history Timeline of World War I Timeline of religion Timelines are used in the natural world and sciences, for subjects such as astronomy and geology: 2009 flu pandemic timeline Chronology of the universe Geologic time scale Timeline of evolutionary history of life Another type of timeline is used for project management.
In these cases, timelines are used to help team members to know what milestones need to be achieved and under what time schedule. For example, in the case of establishing a project timeline in the implementation phase of the life cycle of a computer system. British Library interactive timeline Port Royal des Champs museum timeline
Geminiano Montanari was an Italian astronomer, lens-maker, proponent of the experimental approach to science. He is best known for his observation, made around 1667, that the second-brightest star in the constellation of Perseus varied in brightness, it is that others had observed this effect before, but Montanari was the first named astronomer to record it. The star's names in Arabic and other languages, all of which have a meaning of "ghoul" or "demon", imply that its unusual behaviour had long been recognised. Montanari was born in Modena, studied law in Florence, graduated from the University of Salzburg. In 1662 or 1663 he moved to Bologna, where he drew an accurate map of the Moon using an ocular micrometer of his own making, he made observations on capillarity and other problems in statics, suggested that the viscosity of a liquid depended on the shape of its molecules. In 1669 he succeeded Giovanni Cassini as astronomy teacher at the University of Bologna where one of his duties was to compile an astrological almanac.
He did so in 1665, but perpetrated a deliberate hoax by writing the almanac at random, to show that predictions made by chance were as to be fulfilled as those made by astrology. In the period shortly after Galileo Galilei, experimentalists like Montanari were engaged in a battle against the more mystical views of scientists such as Donato Rossetti. On 21 March 1676 Montanari reported a sighting of a comet to Edmund Halley. Montanari's observations of the great comet of 1680 are mentioned twice in the third volume of Newton's Principia. In 1679 Montanari moved to a teaching post in Padua, but all records of this period of his life have been lost. A letter survives from 1682 recording a sighting of Halley's Comet, he wrote on economics, observing that demand for a particular commodity was fixed, making comments on coinage and the value of money. A crater on the Moon, at 45.8S, 20.6W, is named after him. Pensieri fisico-matematici La Livella Diottrica Trattato mercantile delle monete Montanari, Geminiano.
Pensieri fisico-matematici intorno diversi effetti de' liquidi in cannuccie di vetro e altri vasi. In Bologna: Emilio Maria & fratelli Manolessi. Retrieved 15 June 2015. Montanari, Geminiano. Prostasi fisicomatematica. In Bologna: Emilio Maria & fratelli Manolessi. Retrieved 15 June 2015. Montanari, Geminiano. Speculazioni fisiche sopra gli effetti di que' vetri temprati che rotti in una parte si risolvono in polvere. In Bologna: Emilio Maria & fratelli Manolessi. Retrieved 15 June 2015. Montanari, Geminiano. Copia di lettera scritta all'illustrissimo Gio Giuseppe Orsi. In Bologna: Emilio Maria & fratelli Manolessi. Retrieved 15 June 2015. Montanari, Geminiano. Fiamma volante gran meteora veduta sopra l'Italia la sera del 31 marzo 1676. In Bologna: Emilio Maria & fratelli Manolessi. Retrieved 15 June 2015. Montanari, Geminiano. Lezione academica havuta nell'Academia di s.a. reale in Torino il giorno 5 marzo 1678. In Torino, & in Bologna: Emilio Maria & fratelli Manolessi. Retrieved 15 June 2015. Montanari, Geminiano.
Copia di due lettere scritte all'illustrissimo signor Antonio Magliabechi sopra i moti, e le apparenze delle due comete ultimamente apparse sul fine di nouembre 1680, nelle costellazioni di Vergine e Libra, e sul fine di decembre in quella di Capricorno. Retrieved 15 June 2015. Montanari, Geminiano. Astrologia convinta di falso col mezzo di nuove esperienze e ragioni fisico-astronomiche, o' sia La caccia del frugnuolo. In Venetia: Francesco Nicolini. Retrieved 15 June 2015. Montanari, Geminiano. Discorso sopra la tromba parlante del signor dottore Geminiano Montanari professore delle matematiche in Padova. Aggiontovi un trattato postumo del mare Adriatico, e sua corrente esaminata, co la naturalezza de fiumi scoperta, e con nove forme di ripari corretta. In Venetia: per Girolamo Albrizzi. Gómez López, Susana, Le passioni degli atomi. Montanari e Rossetti: Una polemica tra galileiani, Leo S. Olschki, 1997. Rotta, Sergio,'Scienza e "pubblica felicità" in G. Montanari', in Miscellanea Seicento, Florence, Le Monnier, 1971, vol.
2, pp. 65-208. Vanzo, Alberto,'Experiment and Speculation in Seventeenth-Century Italy: The Case of Geminiano Montanari', Studies in History and Philosophy of Science, 56, pp. 52-61. Works by Geminiano Montanari at Project Gutenberg Works by or about Geminiano Montanari at Internet Archive "The impact of Galilean culture - From Bonaventura Cavalieri to Gian Domenico Cassini", Bologna University, Department of Astronomy, 2004-4-10
The Crab Nebula is a supernova remnant in the constellation of Taurus. The now-current name is due to William Parsons, who observed the object in 1840 using a 36-inch telescope and produced a drawing that looked somewhat like a crab. Corresponding to a bright supernova recorded by Chinese astronomers in 1054, the nebula was observed by English astronomer John Bevis in 1731; the nebula was the first astronomical object identified with a historical supernova explosion. At an apparent magnitude of 8.4, comparable to that of Saturn's moon Titan, it is not visible to the naked eye but can be made out using binoculars under favourable conditions. The nebula lies in the Perseus Arm of the Milky Way galaxy, at a distance of about 2.0 kiloparsecs from Earth. It has a diameter of 3.4 parsecs, corresponding to an apparent diameter of some 7 arcminutes, is expanding at a rate of about 1,500 kilometres per second, or 0.5% of the speed of light. At the center of the nebula lies the Crab Pulsar, a neutron star 28–30 kilometres across with a spin rate of 30.2 times per second, which emits pulses of radiation from gamma rays to radio waves.
At X-ray and gamma ray energies above 30 keV, the Crab Nebula is the brightest persistent source in the sky, with measured flux extending to above 10 TeV. The nebula's radiation allows for the detailed studying of celestial bodies. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab Nebula's radio waves passing through it, in 2003, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula; the inner part of the nebula is a much smaller pulsar wind nebula that appears as a shell surrounding the pulsar. Some sources consider the Crab Nebula to be an example of both a pulsar wind nebula as well as a supernova remnant, while others separate the two phenomena based on the different sources of energy production and behaviour. For the Crab Nebula, the divisions are superficial but remain meaningful to researchers and their lines of study. Modern understanding that the Crab Nebula was created by a supernova traces back to 1921, when Carl Otto Lampland announced he had seen changes in its structure.
This led to the conclusion that the creation of the Crab Nebula corresponds to the bright SN 1054 supernova recorded by Chinese astronomers in AD 1054. There is a 13th-century Japanese reference to this "guest star" in Meigetsuki; the event was long considered unrecorded in Islamic astronomy, but in 1978 a reference was found in a 13th-century copy made by Ibn Abi Usaibia of a work by Ibn Butlan, a Nestorian Christian physician active in Baghdad at the time of the supernova. The Crab Nebula was first identified in 1731 by John Bevis; the nebula was independently rediscovered in 1758 by Charles Messier as he was observing a bright comet. Messier catalogued it as the first entry in his catalogue of comet-like objects; the exact time of the comet's return required the consideration of perturbations to its orbit caused by planets in the Solar System such as Jupiter, which Clairaut and his two colleagues Jérôme Lalande and Nicole-Reine Lepaute carried out more than Halley, finding that the comet should appear in the constellation of Taurus.
It is in searching in vain for the comet that Charles Messier found the Crab nebula, which he at first thought to be Halley's comet. After some observation, noticing that the object that he was observing was not moving across the sky, Messier concluded that the object was not a comet. Messier realised the usefulness of compiling a catalogue of celestial objects of a cloudy nature, but fixed in the sky, to avoid incorrectly cataloguing them as comets. William Herschel observed the Crab Nebula numerous times between 1783 and 1809, but it is not known whether he was aware of its existence in 1783, or if he discovered it independently of Messier and Bevis. After several observations, he concluded; the 3rd Earl of Rosse observed the nebula at Birr Castle in 1844 using a 36-inch telescope, referred to the object as the "Crab Nebula" because a drawing he made of it looked like a crab. He observed it again in 1848, using a 72-inch telescope and could not confirm the supposed resemblance, but the name stuck nevertheless.
In 1913, when Vesto Slipher registered his spectroscopy study of the sky, the Crab Nebula was again one of the first objects to be studied. In the early twentieth century, the analysis of early photographs of the nebula taken several years apart revealed that it was expanding. Tracing the expansion back revealed that the nebula must have become visible on Earth about 900 years ago. Historical records revealed that a new star bright enough to be seen in the daytime had been recorded in the same part of the sky by Chinese astronomers in 1054. Changes in the cloud, suggesting its small extent, were discovered by Carl Lampland in 1921; that same year, John Charles Duncan demonstrated that the remnant is expanding, while Knut Lundmark noted its proximity to the guest star of 1054. In 1928, Edwin Hubble proposed associating the cloud to the star of 1054, an idea which remained controversial until the nature of supernovae was understood, it was Nicholas Mayall who indicated that the star of 1054 was undoubtedly the supernova whose explosion produced the Crab Nebula.
The search for historical supernovae started at that moment: seven other historical sightings have been found by comparing modern observations of supernova remnants with astronomical documents of past centuries. Given its great distance, the daytime "guest star" o
Thomas Henderson (astronomer)
Thomas Henderson FRSE FRS FRAS was a Scottish astronomer and mathematician noted for being the first person to measure the distance to Alpha Centauri, the major component of the nearest stellar system to Earth, the first to determine the parallax of a fixed star, for being the first Astronomer Royal for Scotland. Born in Dundee, he was educated at the High School of Dundee, after which he trained as a lawyer, working his way up through the profession as an assistant to a variety of nobles. However, his major hobbies were astronomy and mathematics, after coming up with a new method for using lunar occultation to measure longitude he came to the attention of Thomas Young, superintendent of the Royal Navy's "Nautical Almanac". Young helped the young Henderson enter the larger world of astronomical science, on his death a posthumous letter recommended to the Admiralty that Henderson take his place. Henderson was passed over for that position, but the recommendation was enough to get him a position at the Royal Observatory at the Cape of Good Hope in South Africa.
There he made a considerable number of stellar observations between April 1832 and May 1833, including those for which he is remembered today. It was pointed out to him by Manuel John Johnson of the East India Company's observatory on Saint Helena that the bright southern star Alpha Centauri had a large proper motion, Henderson concluded that it might be close; the 1830s version of the "space race" was to be the first person to measure the distance to a star using parallax, a task, easier the closer the star. Henderson was thus in a good position to be this person. After retiring back to the United Kingdom due to bad health, he began analysing his measurements and came to the conclusion that Alpha Centauri was just less than one parsec away, 3.25 light years. This figure is reasonably accurate, being 25.6% too small. Henderson did not publish his results, he was beaten to the punch by Friedrich Wilhelm Bessel, who published a parallax of 10.3 light years for 61 Cygni in 1838. Henderson published his results in 1839, but was relegated to second place because of his lack of confidence.
He published confirming observations by Thomas Maclear. Alpha Centauri remained the nearest known star until the discovery of Proxima Centauri in 1915 by Robert T. A. Innes. In the meantime, his measurement work at the Cape had led him to be appointed the first Astronomer Royal for Scotland in 1834; the vacant chair of astronomy at the University of Edinburgh was given to him on the advice of Prime Minister Lord Melbourne. From 1834 he worked at the City Observatory in Edinburgh until his death. In April, 1840 he was elected a Fellow of the Royal Society. Henderson became a member or fellow of several distinguished societies, including the Royal Astronomical Society and the Royal Society of Edinburgh, he married Alexander Adie's daughter Janet Mary Adie in 1836 and had one daughter, Janet Mary Jane Henderson. He died at home 1 Hillside Crescent in Edinburgh on 23 November 1844 and is buried in Greyfriars Kirkyard; the grave may be either in the grave of Alexander Adie or in a grave marked by the stone "to his memory".
His name is not recorded on the Adie grave. A blue plaque is installed on his house at 1 Hillside Crescent, it refers to him as "Thomas J. A. Henderson", similar to middle names wrongly added to Wikipedia around 2007. A larger memorial is incorporated in the external wall of the City Observatory. Henderson, Thomas. "The Parallax of Alpha Centauri, deduced from Mr Maclear's observations at the Cape of Good Hope, in the years 1839 and 1840". Memoirs of the Royal Astronomical Society. 12: 329–372. Bibcode:1842MmRAS..12..329H. Henderson, Thomas. "On the Parallax of Alpha Centauri". Memoirs of the Royal Astronomical Society. 11: 61–68. Bibcode:1840MmRAS..11...61H. Astronomical Society of Edinburgh - journal 38 Biography of Thomas Henderson at the S2A3 Biographical Database of Southern African Science
Friedrich Georg Wilhelm von Struve
Friedrich Georg Wilhelm von Struve was a German-Russian astronomer and geodesist from the famous Struve family. He is best known for studying double stars and for initiating a triangulation survey named Struve Geodetic Arc in his honor, he was born at Duchy of Holstein, the son of Jacob Struve. Struve's father moved the family away from the French occupation to Dorpat in Imperial Russia to avoid military service, equipped with Danish passports. In 1808 he entered the Imperial University of Dorpat, where he first studied philology, but soon turned his attention to astronomy. From 1813 to 1820, he taught at the university and collected data at the Dorpat Observatory, in 1820 became a full professor and director of the observatory, his teachings have had a strong effect, still felt at the university. Struve was occupied with research on double stars and geodesy in Dorpat until 1839, when he founded and became director of the new Pulkovo Observatory near St Petersburg. Among other honors, he won the Gold Medal of the Royal Astronomical Society in 1826.
He was elected a Fellow of the Royal Society in March 1827 and was awarded their Royal Medal the same year. Struve was elected a member of the Royal Swedish Academy of Sciences in 1833, a Foreign Honorary Member of the American Academy of Arts and Sciences in 1834. In 1843 he formally adopted Russian nationality, he retired in 1862 due to failing health. The asteroid 768 Struveana was named jointly in his honour and that of Otto Wilhelm and Karl Hermann Struve and a lunar crater was named for another 3 astronomers of the Struve family: Friedrich Georg Wilhelm, Otto Wilhelm and Otto. Struve's name is best known for his observations of double stars, which he carried on for many years. Although double stars had been studied earlier by William Herschel and John Herschel and Sir James South, Struve outdid any previous efforts, he discovered a large number of double stars and in 1827 published his double star catalogue Catalogus novus stellarum duplicium. Since most double stars are true binary stars rather than mere optical doubles, they orbit around one another's barycenter and change position over the years.
Thus Struve made micrometric measurements of 2714 double stars from 1824 to 1837 and published these in his work Stellarum duplicium et multiplicium mensurae micrometricae. Struve measured the "constant of aberration" in 1843, he was the first to measure the parallax of a star Vega, although Friedrich Bessel had been the first to measure the parallax of a star. In an 1847 work, Etudes d'Astronomie Stellaire: Sur la voie lactee et sur la distance des etoiles fixes, Struve was one of the first astronomers to identify the effects of interstellar extinction, his estimate of the average rate of visual extinction, 1 mag per kpc, is remarkably close to modern estimates. He was interested in geodetic surveying, in 1831 published Beschreibung der Breitengradmessung in den Ostseeprovinzen Russlands, he initiated the Struve Geodetic Arc, a chain of survey triangulations stretching from Hammerfest in Norway to the Black Sea, through ten countries and over 2,820 km, to establish the exact size and shape of the earth.
UNESCO listed the chain on its List of World Heritage Sites in Europe in 2005. Struve was the second of a dynasty of astronomers through five generations, he was the father of Otto Wilhelm von Struve. He was the grandfather of Hermann Struve, Otto Struve's uncle. In 1815 he married Emilie Wall in Altona. In addition to Otto Wilhelm von Struve, other children were Heinrich Wilhelm von Struve, a prominent chemist, Bernhard Wilhelm von Struve, who served as a government official in Siberia and as governor of Astrakhan and Perm. After his first wife died, he remarried to Johanna Henriette Francisca Bartels, a daughter of the mathematician Martin Bartels, who bore him six more children; the most well-known was Karl de Struve, who served successively as Russian ambassador to Japan, the United States, the Netherlands. Bernhard's son Peter Berngardovich Struve is the best known member of the family in Russia, he was one of the first Russian marxists and penned the Manifesto of the Russian Social Democratic Labour Party upon its creation in 1898.
Before the party split into Bolsheviks and Mensheviks, Struve left it for the Constitutional Democratic party, which promoted ideas of liberalism. He represented this party at all the pre-revolutionary State Dumas. After the Russian Revolution, he published several striking articles on its causes and joined the White movement. In the governments of Pyotr Wrangel and Denikin he was one of the ministers. During the following three decades, he lived in Paris, while his children were prominent in the Russian Orthodox Church Outside of Russia. List of Russian astrophysicists Henry Batten. Resolute and undertaking characters: the lives of Wilhelm and Otto Struve. Springer. ISBN 90-277-2652-3. Media related to Friedrich Georg Wilhelm Struve at Wikimedia Commons Works by or about Friedrich Georg Wilhelm von Struve in libraries Portraits of Friedrich Georg Wilhelm Struve from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections Estonian souvenir sheet and first day cover dedicated to Struve and Struve Geodetic Arc
SN 1006 was a supernova, the brightest observed stellar event in recorded history, reaching an estimated −7.5 visual magnitude, exceeding sixteen times the brightness of Venus. Appearing between April 30 and May 1, 1006 AD in the constellation of Lupus, this "guest star" was described by observers across China, Iraq and Europe, recorded in North American petroglyphs; some reports state it was visible in the daytime. Modern astronomers now consider its distance from us to be about 7,200 light-years. Egyptian astrologer and astronomer Ali ibn Ridwan, writing in a commentary on Ptolemy's Tetrabiblos, stated that the "spectacle was a large circular body, 2½ to 3 times as large as Venus; the sky was shining because of its light. The intensity of its light was a little more than a quarter that of Moon light". Like all other observers, Ali ibn Ridwan noted; some astrologers interpreted the event as a portent of famine. The most northerly sighting is recorded in the annals of the Abbey of Saint Gall in Switzerland, at a latitude of 47.5° North.
Monks at St Gall provide independent data as to its magnitude and location in the sky, writing that "n a wonderful manner this was sometimes contracted, sometimes diffused, moreover sometimes extinguished… It was seen for three months in the inmost limits of the south, beyond all the constellations which are seen in the sky". This description is taken as probable evidence that the supernova was of Type Ia; some sources state. According to Songshi, the official history of the Song Dynasty, the star seen on 1 May 1006 appeared to the south of constellation Di, east of Lupus and one degree to the west of Centaurus, it shone so brightly. By December, it was again sighted in the constellation Di; the Chinese astrologer Zhou Keming, on his return to Kaifeng from his duty in Guangdong, interpreted the star to the emperor on May 30 as an auspicious star, yellow in color and brilliant in its brightness, that would bring great prosperity to the state over which it appeared. The reported color yellow should be taken with some suspicion however, because Zhou may have chosen a favorable color for political reasons.
There appear to have been two distinct phases in the early evolution of this supernova. There was first a three-month period. A petroglyph by the Hohokam in White Tank Mountain Regional Park, has been interpreted as the first known North American representation of the supernova, though other researchers remain skeptical. Earlier observations discovered from Yemen may have seen SN 1006 on April 17, two weeks before its assumed earliest observation. SN 1006's associated supernova remnant from this event was not identified until 1965, when Doug Milne and Frank Gardner used the Parkes radio telescope to demonstrate a connection to known radio source, PKS 1459-41; this is located near the star Beta Lupi. X-ray and optical emission from this remnant have been detected, during 2010 the H. E. S. S. Gamma-ray observatory announced the detection of very-high-energy gamma-ray emission from the remnant. No associated neutron star or black hole has been found, the situation expected for the remnant of a Type Ia supernova.
A survey in 2012 to find any surviving companions of the SN 1006 progenitor found no subgiant or giant companion stars, indicating that SN 1006 was most a double degenerate progenitor, that is, the merging of two white dwarf stars. Remnant SNR G327.6+14.6 has an estimated distance of 2.2 kpc. from Earth, making the true linear diameter 20 parsecs. Research has suggested that Type Ia supernovae can irradiate the Earth with significant amounts of gamma-ray flux, compared with the typical flux from the Sun, up to distances on the order of 1 kiloparsec; the greatest risk is to producing effects on life and climate. While SN 1006 did not appear to have such significant effects, a signal of its outburst can be found in nitrate deposits in Antarctic ice. History of supernova observation List of supernova candidates List of supernova remnants List of supernovae Near-Earth supernova Cause of Supernova SN 1006 Revealed Stories of SN 1006 in Chinese literature National Optical Observatory Press Release for March 2003 Simulation of SN 1006 as it appeared in the southern sky at midnight, May 1, 1006 Entry for supernova remnant of SN 1006 from the Galactic Supernova Remnant Catalogue X-ray image of supernova remnant of SN 1006, as seen with the Chandra X-ray Observatory Ancient rock art may depict exploding star Astronomy Picture of the Day, March 17, 2003 Astronomy Picture of the Day, July 4, 2008 Margaret Donsbach: The Scholar's Supernova SN 1006 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images
Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics and chemistry in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, stars, nebulae and comets. More all phenomena that originate outside Earth's atmosphere are within the purview of astronomy. A related but distinct subject is physical cosmology, the study of the Universe as a whole. Astronomy is one of the oldest of the natural sciences; the early civilizations in recorded history, such as the Babylonians, Indians, Nubians, Chinese and many ancient indigenous peoples of the Americas, performed methodical observations of the night sky. Astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, but professional astronomy is now considered to be synonymous with astrophysics. Professional astronomy is split into theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, analyzed using basic principles of physics.
Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain observational results and observations being used to confirm theoretical results. Astronomy is one of the few sciences in which amateurs still play an active role in the discovery and observation of transient events. Amateur astronomers have made and contributed to many important astronomical discoveries, such as finding new comets. Astronomy means "law of the stars". Astronomy should not be confused with astrology, the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin, they are now distinct. Both of the terms "astronomy" and "astrophysics" may be used to refer to the same subject. Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties," while "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, dynamic processes of celestial objects and phenomena."
In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject. However, since most modern astronomical research deals with subjects related to physics, modern astronomy could be called astrophysics; some fields, such as astrometry, are purely astronomy rather than astrophysics. Various departments in which scientists carry out research on this subject may use "astronomy" and "astrophysics" depending on whether the department is affiliated with a physics department, many professional astronomers have physics rather than astronomy degrees; some titles of the leading scientific journals in this field include The Astronomical Journal, The Astrophysical Journal, Astronomy and Astrophysics. In early historic times, astronomy only consisted of the observation and predictions of the motions of objects visible to the naked eye.
In some locations, early cultures assembled massive artifacts that had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops and in understanding the length of the year. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye; as civilizations developed, most notably in Mesopotamia, Persia, China and Central America, astronomical observatories were assembled and ideas on the nature of the Universe began to develop. Most early astronomy consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, the nature of the Sun and the Earth in the Universe were explored philosophically; the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the Ptolemaic system, named after Ptolemy.
A important early development was the beginning of mathematical and scientific astronomy, which began among the Babylonians, who laid the foundations for the astronomical traditions that developed in many other civilizations. The Babylonians discovered. Following the Babylonians, significant advances in astronomy were made in ancient Greece and the Hellenistic world. Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena. In the 3rd century BC, Aristarchus of Samos estimated the size and distance of the Moon and Sun, he proposed a model of the Solar System where the Earth and planets rotated around the Sun, now called the heliocentric model. In the 2nd century BC, Hipparchus discovered precession, calculated the size and distance of the Moon and inven