Timeline of astronomy: Difference between revisions
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Islamic and Indian astronomical works (including |
Islamic and Indian astronomical works (including ''Aryabhatiya'' and ''Brahma-Sphuta-Siddhanta'') are translated into [[Latin]] in [[Córdoba, Spain]] in [[1126]], introducing European astronomers to Islamic and Indian astronomy. |
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Revision as of 12:09, 9 March 2006
Many ancient sites are thought to have astronomical significance, such as the Egyptian pyramids, Harappan shell instruments, British megaliths, and buildings in China and Latin America.
In Lothal, the ancient port city of the Harappan civilization in Gujarat, India, a thick ring-like shell object found with four slits each in two margins served as a compass to measure angles on plane surfaces or in horizon in multiples of 40–360 degrees. Such shell instruments were invented to measure 8–12 whole sections of the horizon and sky, explaining the slits on the lower and upper margins. Archaeologists this as evidence the Lothal experts had achieved something 2,000 years before the Greeks are 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, the Stonehenge is built. It is a giant circle of stones that are aligned to the position of the Sun and the Moon in the sky.
Chinese astronomers record a solar eclipse.
Yajnavalkya composes 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 year as 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 year remains 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.
Babylonian astronomers discover 18.6-year cycle in the rising and 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 the 6th century Greece, this knowledge is used to predict eclipses.
According to Thales (who studied in Egypt around this time), Egyptian astronomers predict a solar eclipse.
Plato, a greek philosopher founds a school 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.
Aristarchus of Samos proposes heliocentrism an alternative to the Earth-centered universe. His heliocentric model 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.
The earliest recorded sighting of Halley's comet is 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.
Ptolemy publishes his star catalog, listing 48 constellations and endorses the 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.
The Hindu cosmological time cycles explained in the Surya Siddhanta, which was copied from an earlier work, 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.
Indian mathematician-astronomer 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.
Indian mathematician-astronomer 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.
The Sanskrit works of Aryabhata and Brahmagupta, along with the Sanskrit text Surya Siddhanta, are translated into Arabic, introducing Muslim astronomers to Indian astronomy.
The earliest surviving astrolabe is contructed by Islamic mathematician-astronomer Mohammad al-Fazari. Astrolabes are the most advanced instruments of their time. The precise measurment of the positions of stars and planets allows Islamic astronomers to compile the most detailed almanacs and star atlases yet.
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 supernova exploding.
Islamic and Indian astronomical works (including Aryabhatiya and Brahma-Sphuta-Siddhanta) are translated into Latin in Córdoba, Spain in 1126, introducing European astronomers to Islamic and Indian astronomy.
Indian mathematician-astronomer 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.
Nicolaus Copernicus publishes his theory that Earth travels around the Sun, in contradiction of the Church's teachings. However, he complicates his theory by retain plato's perfect circular orbits of the planets.
A brilliant comet is observed by Tycho Brache, who proves that it is travelling beyond Earth's atmosphere and therefore provides the first evidence that the heavens can change.
Dutch eyeglass maker Hans Lippershey invents the refracting telescope. The invention spreads rapidly across Europe, as scientists make their own instruments. Their discoveries begin a revolution in astronomy.
Johannes Kepler publishes 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. Almanacs based on his laws prove to be highly accurate.
Galileo Galilei publishes the findings of his observations with the telescape 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.
As the power and the quality of the telescopes increases, Christiaan Huygens studies Saturn and discovers its largest satellite, Titan. He also explains Satern's appearance, suggesting the planet is surround by a thin ring.
Scottish astronomer James Gregory builds a reflecting telescope, using mirrors instead of lenses, to allow a larger aperture and reduce light loss, within five years, Isaac Newton improves the design, creating the Newtonian telescope.
Isaac Newton publishes his 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.
Edmond Halley calculates that the comets recorded at 76-year intercals 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.
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.
Amateur astronomer William Herschel discovers 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.
Charles Messier publishes 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.
William Herschel splits sunlight through a prism and with a thermometer, mesures 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.
Italian astronomer Giuseppe Piazzi discovers what appears to be a new planet orbiting Mars and Jupiter, and names it Ceres. William Herschel proves 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.
Joseph von Fraunhofer builds 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 1859l these lines are linked to chemical elements in the Sun's atmosphere. Spectroscopy becomes a method for studying what stars are made of.
Friedrich Bessel successfully 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 framwork for measuring the scale of the universe.
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.
Irish astronomers the Earl of Risse completes 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.
French physicists Jean Foucault and Armand Fizeau take the first detailed photographs of the Sin'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.
A new planet, Neptune, is identified by German astronomer Johann Gottfried Galle while 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.
Astronomers notice a new bright emmission 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 Lockyer concludes 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.
An American astronomer Henry Draper takes 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 Huggins uses absoprtion lines to measure the redshifts of stars, which give the first indication of how fast stars are moving.
Konstantin Tsiolkovsky publishes 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.
A comprehensive survey of stars, the Henry Draper Catalog, is published. In the catalog, Annie Jump Cannon proposes a sequence of classiflying stars by the absorption lines in their spectra, which is still in use today.
Ejnar Hertzsprung establishes 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 Russel publishes 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 Eddington finally settles the controversy in 1924
German physicist Karl Schwarzschild uses 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.
Edwin Hubble discovers a Cephied variable 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.
Robert Goddard launches 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.
Edwin Hubble discovers 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 Lemaître suggests that the expansion can be traced to an initial "Big Bang".
By applying new ideas from subatomic physics, Subrahmanyan Changresekhar predicts 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 Baade and Fritz Zwicky describe the neutron star that results from this collapse, causing a supernova explosion.
Clyde Tombaugh discovers the planet pluto at the Lowell Obervatory in Flagstaff, Arizona. The planet is so faint and moving so slowly that he has to compare photos taken several nights apart.
Karl Jansky detects 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.
German physicist Hans Bethe explains how stars generate energy. He outlines a series of nuclear fusion reactions that turn hygrogen 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.
A team of German scientists led by Wernher von Braun develops 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.
The largest telescope in the world, with a 5.08 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 Pionner 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 Gagarin becomes the first person to orbit Earth in April. Nasa astronaut Alan Shepard becomes the first American in space a month later, but does not go into orbit. John Glenn achieves this in early 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 porbes to planets through the rest of the 1960s and 1970s.
Dutch-American astronomer Maarten Schmidt measures 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.
Arno Penzias and Robert Wilson announce the discoery 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 Band that created the universe 13 billion yeears ago.
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 follow ups to NASA's Ranger series of crash landers, scout sites for possible manned landings.
Jocelyn Bell Burnell and Antony Hewish detected 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.
THe US wins the race for the Moon, as Neil Armstrong steps onto the lunar surface on July 20th. Apollo 11 is followed by five further landing missions, three carrying a sophisticated lunar rover vehicle.
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 serveral possible black holes.
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.
The Russian probe Venera 9 lands on the surface of Venus and sends vack the first picture of its surface. The first prove 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 mussion 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 systerm, 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 and infraed 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 suttles 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 itself.
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 "ripples", 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.