- Timeline of astronomy
Timelineof astronomy 2500 BC
Many ancient sites are thought to have astronomical significance, such as the
Ancient Egyptian pyramids, Harappanshell instruments, British megaliths, and buildings in Chinaand Latin America.
Lothal, the ancient port cityof the Harappan civilization in Gujarat, India, a thick ring-like shell object found with four slits each in two margins served as a compassto measure angles on plane surfaces or along the horizon in multiples of 40–360 degrees. Such shell instruments were invented to measure 8–12 whole sections of the horizonand sky, explaining the slits on the lower and upper margins. Archaeologists see this as evidence that the Lothal experts had achieved something 2,000 years before the Greeksare credited with doing: an 8–12 fold division of horizon and sky, as well as an instrument to measure angles and the position of stars, and for navigation purposes.
Around this time in
England, Stonehengeis built. It is a giant circle of stones that are aligned to the position of the Sunand the Moonin the sky.
Chinese astronomers record a
solar eclipse. 900 BC Yajnavalkyacomposes the astronomical text " Shatapatha Brahmana" in ancient India. He is the first to propose the concept of heliocentrism(the idea that the Sun is at the centre of the solar system and the Earth is moving around it). He refers to the Earth as a sphere and the Sun as the "centre of spheres". Based on this heliocentric model, he proposes a 95-year cycle to synchronize the motions of the Sun and the Moon, which gives the average length of the tropical yearas 365.24675 days, which is only 6 minutes longer than the modern value of 365.24220 days. This estimate for the length of the tropical yearremains the most accurate anywhere in the world for over a thousand years. The distances of the Moon and the Sun from the Earth is accurately measured as 108 times the diameters of these heavenly bodies. These are very close to the modern values (using modern instruments) of 110.6 for the Moon and 107.6 for the Sun. 750 BC Babylonian astronomers discover 18.6-year cycle in the risingand setting of the Moon. From this they created the first almanacs- tables of the movements of the Sun, Moon and planets for the use in astrology. In 6th century Greece, this knowledge is used to predict eclipses. 600 BC
Thales(who studied in Egypt around this time), Ancient Egyptian astronomers predict a solar eclipse. 388 BC Plato, a Greek philosopher, founds a school (the Platonic Academy) that will influence the next 2000 years. This promotes the idea that everything in the universe moves in harmony and that the Sun, Moon, and planets move around Earth in perfect circles. 270 BC Aristarchus of Samosproposes heliocentrism as an alternative to the Earth-centered universe. His heliocentricmodel places the Sun at its center, with Earth as just one planet orbiting it. However, there were only a few people who took the theory seriously. 164 BC
The earliest recorded sighting of
Halley's cometis made by Babylonian astronomers. Their records of the comet's movement allow astronomers today to predict accurately how the comet's orbit changes over the centuries.
Ptolemypublishes his star catalogue, listing 48 constellations and endorses the geocentric(Earth-centered) view of the universe. His views go unquestioned for nearly 1500 years in Europe, and are passed down to Arabic and medieval European astronomers in his book the " Almagest". 400
Hinducosmological time cycles explained in the " Surya Siddhanta", gives the average length of the sidereal year (the length of the Earth's revolution around the Sun) as 365.2563627 days, which is only 1.4 seconds longer than the modern value of 365.2563627 days. This remains the most accurate estimate for the length of the sidereal year anywhere in the world for over a thousand years. 499 Indian mathematician- Aryabhata, in his "Aryabhatiya", propounds a heliocentric solar system of gravitation, and an eccentric elliptical model of the planets, where the planets spin on their axes and follow elliptical orbits around the Sun. He also writes that the planets and the Moon do not have their own light but reflect the light of the Sun, and that the Earth rotates on its axis causing day and night and also round the sun causing year. Aryabhata gives the radii of planetary orbits in terms of orbit of earth/sun. Incredibly, he also believes that the orbits of the planets are ellipses and not circles, and also correctly explains the causes of eclipse of sun and moon. His calculation of Earth's diameter at 8316 miles would remain the most accurate approximation for over a thousand years. Aryabhata also accurately computes the Earth's circumference, the solar and lunar eclipses, and the length of Earth's revolution around the Sun. 628
Brahmagupta, in his "Brahma-Sphuta-Siddhanta", first recognizes gravity as a force of attraction, and briefly describes the law of gravitation. He gives methods for calculations of the motions and places of various planets, their rising and setting, conjunctions, and calculations of the solar and lunar eclipses. 773
Sanskritworks of Aryabhataand Brahmagupta, along with the Sanskrit text " Surya Siddhanta", are translated into Arabic, introducing Muslim astronomers to Indian astronomy. 777 Muhammad al-Fazariand Yaqūb ibn Tāriqthe Sanskrit works into Arabic as as "Zij al-Sindhind". 830
The first major Muslim work of astronomy is the "Zij al-Sindh" by al-Khwarizimi. The work contains tables for the movements of the sun, the moon and the five planets known at the time. The work is significant as it introduced Ptolemaic concepts into Islamic sciences. This work also marks the turning point in Islamic astronomy. Hitherto, Muslim astronomers had adopted a primarily research approach to the field, translating works of others and learning already discovered knowledge. Al-Khwarizmi's work marked the beginning of nontraditional methods of study and calculations. [Dallal (1999), pg. 163]
al-Farghani wrote "Kitab fi Jawani" ("A compendium of the science of stars"). The book primarily gave a summary of Ptolemic cosmography. However, it also corrected Ptolemy based on findings of earlier Arab astronomers. Al-Farghani gave revised values for the obliquity of the ecliptic, the precessional movement of the
apogees of the sun and the moon, and the circumference of the earth. The books were widely circulated through the Muslim world, and even translated into Latin. [Dallal (1999), pg. 164] 870 Al-Kindi(Alkindus in Latin) stated his law of terrestrial gravity:Qadir (1989), p. 6-11.] Robert Hookelater quantified and modified Al-Kindi's law of terrestrial gravity in the 17th century for explaining celestial motion to state that:Qadir (1989), p. 11.]
Robert Hooke's law of celestial gravity in turn inspired
Newton's law of universal gravitation. 928
The earliest surviving
astrolabeis constructed by Islamic mathematician-astronomer Mohammad al-Fazari. Astrolabes are the most advanced instruments of their time. The precise measurement of the positions of stars and planets allows Islamic astronomers to compile the most detailed almanacs and star atlases yet. 1000
The first Muslim astonomer to support a heliocentric model was
Ibn al-Haytham(Alhacen in Latin) in the early 11th century.Qadir (1989), p. 5-10.]
The foundations of telescopic astronomy can also be traced back to Ibn al-Haytham. His work was influential in the development of the modern telescope. [O. S. Marshall (1950). "Alhazen and the Telescope", "Astronomical Society of the Pacific Leaflets" 6, p. 4.]
Abu al-Rayhan al-Biruni discussed the Indian heliocentric theories of
Aryabhata, Brahmaguptaand Varahamihirain his "Ta'rikh al-Hind" ("Indica" in Latin). Biruni stated that the followers of Aryabhata consider the Sun to be at the center. In fact, Biruni casually stated that this does not create any mathematical problems. [Saliba (1999).] 1031
Abu al-Rayhan al-Biruni, in his "Kitab al-qanun al-Mas’udi" (later translated into Latin as "Canon Mas’udicus"), observed that the planets revolved in elliptical orbits, instead of the circular orbits of the
Greeks.Richard Covington (2007)] Abu Said Sinjari, a contemporary of Biruni, also suggested the possible heliocentric movement of the Earth around the Sun, which Biruni did not reject.A. Baker, L. Chapter (2002)] 1050
Al-Zarqali (Arzachel in Latin) stated that the
planets moved in ellipses with the Sunat one focus, which is now known as Kepler's first law of planetary motion. 1054
Chinese astronomers record the sudden appearance of a bright star. Native-American rock carvings also show the brilliant star close to the Moon. This star is the Crab
Abu Ubayd al-Juzjani published the "Tarik al-Aflak". In his work, he indicated the so-called "
equant" problem of the Ptolemic model. Al-Juzjani even proposed a solution for the problem. In al-Andalus, the anonymous work "al-Istidrak ala Batlamyus" (meaning "Recapitulation regarding Ptolemy"), included a list of objections to the Ptolemic astronomy.
One of the most important works in the period was "Al-Shuku ala Batlamyus" ("Doubts on Ptolemy"). In this, the author summed up the inconsistencies of the Ptolemic models. Many astronomers took up the challenge posed in this work, namely to develop alternate models that evaded such errors.
Islamic and Indian astronomical works (including "Aryabhatiya" and "Brahma-Sphuta-Siddhanta") are translated into
Latinin Córdoba, Spainin 1126, introducing European astronomers to Islamic and Indian astronomy. 1150
Bhaskara, in his "Siddhanta Shiromani", calculates the longitudes and latitudes of the planets, lunar and solar eclipses, risings and settings, the Moon's lunar crescent, syzygies, and conjunctions of the planets with each other and with the fixed stars, and explains the three problems of diurnal rotation. He also calculates the planetary mean motion, ellipses, first visibilities of the planets, the lunar crescent, the seasons, and the length of the Earth's revolution around the Sun to 9 decimal places. 1250 Mo'ayyeduddin Urdidevelops the Urdi lemma, which is later used in the Copernican heliocentric model. Nasir al-Din al-Tusiresolved significant problems in the Ptolemaic system by developing the Tusi-coupleas an alternative to the physically problematic equantintroduced by Ptolemy,M. Gill (2005). [http://www.chowk.com/show_article.cgi?aid=00005502&channel=university%20ave Was Muslim Astronomy the Harbinger of Copernicanism?] ] and conceived a plausible model for elliptical orbits. His Tusi-couple is later used in the Copernican model.
Qutb al-Din al-Shirazi, in his "The Limit of Accomplishment concerning Knowledge of the Heavens", discusses the possibility of heliocentrism.
'Umar al-Katibi al-
Qazwini, who also worked at the Maraghahobservatory, in his "Hikmat al-'Ain", wrote an argument for a heliocentric model, though he later abandoned the idea. 1350 Ibn al-Shatir( 1304– 1375), in his "A Final Inquiry Concerning the Rectification of Planetary Theory", eliminated the need for an equant by introducing an extra epicycle, departing from the Ptolemaic system in a way very similar to what Copernicuslater also did. Ibn al-Shatir proposed a system that was only approximately geocentric, rather than exactly so, having demonstrated trigonometrically that the Earth was not the exact center of the universe. His rectification is later used in the Copernican model. 1543 Nicolaus Copernicuspublishes " De revolutionibus orbium coelestium" containing his theory that Earth travels around the Sun. However, he complicates his theory by retaining Plato's perfect circular orbits of the planets. 1577
A brilliant comet is observed by
Tycho Brahe, who proves that it is travelling beyond Earth's atmosphere and therefore provides the first evidence that the heavens can change. 1608
Dutch eyeglass maker
Hans Lippersheyinvents the refracting telescope. The invention spreads rapidly across Europe, as scientists make their own instruments. Their discoveries begin a revolution in astronomy. 1609 Johannes Keplerpublishes his " New Astronomy". In this and later works, he announces his three laws of planetary motion, replacing the circular orbits of Plato with elliptical ones. Almanacsbased on his laws prove to be highly accurate. 1610 Galileo Galileipublishes " Sidereus Nuncius" describing the findings of his observations with the telescope he built. These include spots on the Sun. craters on the Moon, and four satellites of Jupiter. Proving that not everything orbits Earth, he promotes the Copernican view of a Sun-centered universe. 1655
As the power and the quality of the telescopes increases,
Christiaan Huygensstudies Saturn and discovers its largest satellite, Titan. He also explains Saturn's appearance, suggesting the planet is surround by a thin ring. 1663
Scottish astronomer James Gregory builds a
reflecting telescope, using mirrors instead of lenses, to allow a larger aperture and reduce light loss, but within five years, Isaac Newton improves the design, creating the Newtonian telescope. 1687 Isaac Newtonpublishes his "Philosophiae Naturalis Principia Mathematica", establishing the theory of gravitation and laws of motion. The Principia explains Kepler's laws of planetary motion and allows astronomers to understand the forces acting between the Sun, the planets, and their moons. 1705 Edmond Halleycalculates that the comets recorded at 76-year intervals from 1456 to 1682 are one and the same. He predicts that the comet will return again in 1758. When it reappears as expected, the comet is named in his honor. 1750
French astronomer Nicolas de Lacaille sails to southern oceans and begins work compiling a catalog of more than 10000 stars in the southern sky. Although Halley and others have observed from the Southern Hemisphere before, Lacaille's star catalog is the first comprehensive one of the southern sky.
William Herscheldiscovers the planet Uranus, although he at first mistakes it for a comet. Uranus is the first planet to be discovered beyond Saturn, which was thought to be the most distant planet in ancient times. 1784 Charles Messierpublishes his catalog of star clusters and nebulas. Messier draws up the list to prevent these objects from being identified as comets. However, it soon becomes a standard reference for the study of star clusters and nebulars and is still in use today. 1800
William Herschel splits sunlight through a prism and with a thermometer, measures the energy given out by different colours. He notices a sudden increase in energy beyond the red end of the
spectrum, discovering invisible infrared and laying the foundations of spectroscopy. 1801
Giuseppe Piazzidiscovers what appears to be a new planet orbiting Mars and Jupiter, and names it Ceres. William Herschelproves it is a very small object, calculating it to be only 320 km in diameter, and not a planet. He proposes the name asteroid, and soon other similar bodies are being found. We now know that Ceres is 932 km in diameter, however, it is still too small to be a planet. 1814 Joseph von Fraunhoferbuilds the first accurate specrometer and uses it to study the spectrum of the Sun's light. He discovers and maps hundreds of fine dark lines crossing the solar spectrum. In 1859 these lines are linked to chemical elements in the Sun's atmosphere. Spectroscopy becomes a method for studying what stars are made of. 1838 Friedrich Besselsuccessfully uses the method of stellar parallax, the effect of Earth's annual movement around the Sun, to calculate the distance to 61 Cygin: the first star other that the Sun to have its distance measured. Bessel has pioneered the truly accurate measurement of stellar positions, and the parallax technique establishes a framework for measuring the scale of the universe. 1843
German Amateur astronomer
Heinrich Schwabe, who has been studying the Sun for the past 17 years, announces his discovery of a regular cycle in sunspot numbers - the first clue to the Sun's internal structure. 1845
William Parsons, 3rd Earl of Rossecompletes the first of the world's great telescopes, with a 180-cm mirror. He uses it to study and draw the structure of nebulas, and within a few months discovers the spiral structure of the Whirlpool Galaxy.
Jean Foucaultand Armand Fizeautake the first detailed photographs of the Sun's surface through a telescope - the birth of scientific astrophotography. Within five years, astronomers produce the first detailed photographs of the Moon. Early film is not sensitive enough to image stars. 1846
A new planet, Neptune, is identified by German astronomer
Johann Gottfried Gallewhile searching in the position suggested by Urbain Le Verrier. Le Verrier has calculated the position and size of the planet from the effects of its gravitational pull on the orbit of Uranus. An English mathematician, John Couch Adams, also made a similar calculation a year earlier. 1868
Astronomers notice a new bright emission line in the spectrum of the Sun's atmosphere during an eclipse. The emission line is caused by an element's giving out light, and British astronomer
Norman Lockyerconcludes that it is an element unknown on Earth. He calls it helium, from the Greek word for the Sun. Nearly 30 years later, helium is found on Earth. 1872
An American astronomer
Henry Drapertakes the first photograph of the spectrum of a star (Vega), showing absortion lines that reveal its chemical makeup. Astronomers begin to see that spectroscopy is the key to understanding how stars evolve. William Hugginsuses absoprtion lines to measure the redshifts of stars, which give the first indication of how fast stars are moving. 1895 Konstantin Tsiolkovskypublishes his first article on the possibility of space flight. His greatest discovery is that a rocket, unlike other forms of propulsion, will work in a vacuum. He also outlines the principle of a multistage launch vehicle. 1901
A comprehensive survey of stars, the
Henry Draper Catalog, is published. In the catalog, Annie Jump Cannonproposes a sequence of classifying stars by the absorption lines in their spectra, which is still in use today. 1906 Ejnar Hertzsprungestablishes the standard for measuring the true brightness of a star. He shows that there is a relationship between color and absolute magnitude for 90% of the stars in the Milky Way Galaxy. In 1913, Henry Norris Russellpublishes a diagram that shows this relationship. Although astronomers agree that the diagram shows the sequence in which stars evolve, they argue about which way the sequence progresses. Arthur Eddingtonfinally settles the controversy in 1924. 1916
Karl Schwarzschilduses Albert Einstein's theory of general relativity to lay the groundwork for black hole theory. He suggests that if any star collapse to a certain size or smaller, its gravity will be so strong that no form of radiation will escape from it. 1923 Edwin Hubblediscovers a Cepheidvariable star in the "Andromeda Nebula" and proves that Andromeda and other nebulas are galaxies far beyond our own. By 1925, he produces a classification system for galaxies. 1926 Robert Goddardlaunches the first rocket powered by liquid fuel. He also demonstrates that a rocket can work in a vacuum. His later rockets break the sound barrier for the first time. 1929 Edwin Hubblediscovers that the universe is expanding and that the farther away a galaxy is, the faster it is moving away from us. Two years later, Georges Lemaîtresuggests that the expansion can be traced to an initial "Big Bang". 1930
By applying new ideas from subatomic physics,
Subrahmanyan Changresekharpredicts that the atoms in a white dwarf star of more than 1.44 solar masses will disintegrate, causing the star to collapse violently. In 1933, Walter Baadeand Fritz Zwickydescribe the neutron star that results from this collapse, causing a supernova explosion. Clyde Tombaughdiscovers the planet Plutoat the Lowell Observatory in Flagstaff, Arizona. The planet is so faint and moving so slowly that he has to compare photos taken several nights apart. 1932 Karl Janskydetects the first radio waves coming from space. In 1942, radio waves from the Sun are detected. Seven years later radio astronomers identify the first distant source - the Crab Nebula, and the galaxies Centaurus A and M87. 1938
Hans Betheexplains how stars generate energy. He outlines a series of nuclear fusion reactions that turn hydrogen into helium and release enormous amounts of energy in a star's core. These reactions use the star's hydrogen very slowly, allowing it to burn for billions of years. 1944
A team of German scientists led by
Wernher von Braundevelops the V-2, the first rocket powered ballistic missile. Scientists and engineers from Braun's team were captured at the end of World War II and drafted into the American and Russian rocket programs. 1948
The largest telescope in the world, with a 5.08m (200in) mirror, is completed at Palomar Mountain in California. At the time, the telescope pushes single-mirror telescope technology to its limits - large mirrors tend to bend under their own weight.
Russia launches the first artificial satellite, Sputnik 1, into orbit, beginning the space age. The US launches its first satellite, Explorer 1, four months later.
Russia and the US both launch probes to the Moon, but NASA's Pioneer probes all failed. The Russian Luna program was more successful. Luna 2 crash-lands on the Moon's surface in September, and Luna 3 returns the first pictures of the Moon's farside in October.
Russia takes the lead in the space race as
Yuri Gagarinbecomes the first person to orbit Earth in April. NASA astronaut Alan Shepardbecomes the first American in space a month later, but does not go into orbit. John Glennachieves this in early 1962. 1962
Mariner 2 becomes the first probe to reach another planet, flying past Venus in December. NASA follows this with the successful Mariner 4 mission to Mars in 1965, both the US and Russia sends many more probes to planets through the rest of the 1960s and 1970s.
Maarten Schmidtmeasures the spectra of quasars, the mysterious starlike radio sources discovered in 1960. He establishes that quarsars are active galaxies, and among the most distant objects in the universe. 1965 Arno Penziasand Robert Wilsonannounce the discovery of a weak radio signal coming from all parts of the sky. Scientists figure out that this must be emitted by an object at a temperature of -270°C. Soon it is recognized as the remnant of the very hot radiation from the Big Bang that created the universe 13 billion years ago. 1966
Russian Luna 9 probe makes the first successful soft landing on the Moon in January, while the US lands the far more complex Surveyor missions, which follows up to NASA's Ranger series of crash landers, scout sites for possible manned landings.
1967 Jocelyn Bell Burnelland Antony Hewishdetected the first pulsar, an object emitting regular pulses of radio waves. Pulsars are eventually recognized as rapidly spinning neutron stars with intense magnetic fields - the remains of a supernova explosion. 1969
The US wins the race for the Moon, as
Neil Armstrongsteps onto the lunar surface on July 20th. Apollo 11 is followed by five further landing missions, three carrying a sophisticated lunar rover vehicle. 1970
The Uhuru satellite, designed to map the sky at X-ray wavelengths, is launched by NASA. The existence of X rays from the Sun and a few other stars has already been found using rocket-launched experiments, but Uhuru charts more than 300 X-ray sources, including several possible black holes.
C.T. Bolton was the first to develop a computer model for stellar atmospheres.
Russia launches its first space station, Salyut 1, into orbit. It is followed by a series of stations, culminating with Mir in 1986. A permanent platform in orbit allows cosmonauts to carry out serious research and to set a series of new duration records for spaceflight.
Charles Thomas Bolton was the first astronomer to present irrefutable evidence of the existence of a black hole.
The Russian probe Venera 9 lands on the surface of Venus and sends back the first picture of its surface. The first probe to land on another planet, Venera 7 in 1970, had no camera. Both break down within an hour in the hostile atmosphere.
Two NASA probes arrive at Mars. Each Viking mission consists of an orbiter, which photographs the planet from above, and a lander, which touches down on the surface, analyzes the rocks, and searches unsuccessfully for life.
Two Voyager probes are launched by NASA to the outer planets. The Voyagers return scientific data and pictures from Jupiter and Saturn, and, before leaving the solar system, Voyager 2 becomes the first probe to visit Uranus and Neptune.
Columbia, the first of NASA's reusable space shuttles, makes its maiden flight, ten years in development, the shuttle will make space travel routine and eventually open the path for a new International Space Station.
The first infrared astronomy satellite, ITAS, is launched. It must be cooled to extremely low temperatures with liquid helium, and it operates for only 300 days before the supply of helium is exhausted. During this time it completes an infrared survey of 98% of the sky.
NASA's spaceflight program comes to a halt when the space shuttle Challenger explodes shortly after launch. A thorough inquiry and modifications to the rest of the fleet kept the shuttles on the ground for nearly three years.
The returning Halley's comet is met by a fleet of five probes from Russia, Japan, and Europe. The most ambitious is the European Space Agency's Giotto, which flies through the comet's coma and photographs the nucleus.
The Magellan probe, launched by NASA, arrives at Venus and spends three years mapping the planet with radar. Magellan is the first in a new wave of probes that include Galileo, which arrives at Jupiter in 1995, and Cassini. which is scheduled to arrive ar Saturn in 2004.
The Hubble Space Telescope, the first large optical telescope in orbit, is launched using the space shuttle, but astronomers soon discovered that it is crippled by a problem with its mirror. A complex repair mission in 1993 allows the telescope to start producing spectacular images of distant stars, nebulas, and galaxies.
The Cosmic Background Explorer satellite produces a detailed map of the background radiation remaining from the Big Bang. The map shows "nipples", caused by slight variations in the density of the early universe - the seeds of galaxies and galaxy clusters.
The 10-m Keck telescope on Mauna Kea, Hawaii, is completed. The first revolutionary new wave of telescopes, the Keck's main mirror is made of 36 six-sided segments, with computers to control their alignment. New optical telescopes also make use of interferometry - improving resolution by combining images from separate telescopes.
Construction work on a huge new space station begins. A joint venture between many countries, including former space rivals Russia and the US, the space station will be the size of a football field when completed. It will house up to seven astronauts in orbit at any one time and act as a platform for microgravity research, astronomy, and further explorations of the solar system.
* A. Baker and L. Chapter (2002), "Part 4: The Sciences". In M. M. Sharif, "A History of Muslim Philosophy", "Philosophia Islamica".
* Richard Covington (May-June 2007). "Rediscovering Arabic science", "
Saudi Aramco World", p. 2-16.
* Ahmad Dallal, "Science, Medicine and Technology.", in "The Oxford History of Islam", ed. John Esposito, New York:
Oxford University Press, (1999).
* Asghar Qadir (1989). "Relativity: An Introduction to the Special Theory". World Scientific,
Singapore. ISBN 9971506122.
George Saliba(1999). [http://www.columbia.edu/~gas1/project/visions/case1/sci.1.html Whose Science is Arabic Science in Renaissance Europe?] Columbia University.
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