CHRONOLOGY – some selected dates in the development of sundials and solar astronomy
|
Date |
Development |
| 9000 BC to 8000 BC | The Maya make astronomical inscriptions and constructions in Central America. A marked bone (possibly) indicating months and lunar phases in use in Ishango (Zaire) |
| 4228 BC to 2773 BC | The Egyptians institute a 365-day calendar. The start of the year, coinciding with the annual Nile floods, is linked to the rising of Sirius (the Dog Star) in line with the sun. |
| 1500 BC to 1450 BC |
L-shaped sundials used in Egypt. |
| 1450 BC to 1400 BC |
Stonehenge achieves the form known today. |
| 600 BC to 590 BC |
Sundials are used in China and the Chinese text “Arithmetic classic of the gnomon and the circular paths of the heaven” contains a version of the Pythagorean theorem. |
| 585 BC | Thales of Miletus (Turkey) correctly predicts a solar eclipse. |
| 520 BC to 510 BC |
Anaximander introduces the sundial to Greece (previously used in Mesopotamia, Egypt and China. He also produces a cylindrical (sic) model of the Earth. |
| 500 BC to 490 BC |
The Pythagoreans (Greece) introduce a spherical model of the Earth. |
| 450 BC approx | Greek philosopher Democritus draws the first maps with rectangular grids of “latus and longus” (latitude and longitude). |
| 480 BC to 470 BC |
Greek philosopher Oenopides calculates that the axis of the Earth is tipped over by 24° from the plane of its orbit. |
| 340 BC to 330 BC |
Kiddinu (Babylonia) works out an (inaccurate) version of the precession of the equinoxes. |
| 270 BC to 260BC |
Aristarchus of Samos (near Turkey) challenges Aristotle’s theory by asserting that the Sun is the centre of the solar system and the planets revolve around it. He estimates the distances of the Moon and (wrongly) the Sun from the Earth. |
| 240 BC to 230 BC |
Eratosthenes of Cyrene (Libya) calculates the circumference of the Earth from the difference in latitude between Alexandria and Aswan, using shadow lengths. He also lays down lines of longitude on a map. |
| 190 BC to 180 BC |
The Greek astronomer Seleucus is the last known astronomer to champion a helio-centric theory of the solar system until Copernicus. |
| 164 BC | Pliny, writing about 210 years later, records that a sundial was properly set up for the first time in Rome around this time, and the Romans begin to divide the period of daylight into hours. |
| 160 BC to 140 BC |
Hipparchus of Nicea (Turkey) produces a more accurate theory of the precession of the equinoxes. |
| 120 BC to 110 BC |
Hipparchus of Nicea (Turkey) uses a total solar eclipse and parallax to measure the distances to and sizes of the Moon (correctly) and the Sun (an order of magnitude too small). |
| 87 BC | A complex mechanical Greco-Egyptian astronomical calendar is made and shipped to Rome. It is later recovered from the sea and becomes known as the Antikythera mechanism. |
| 52 BC | Chinese astronomer Ken Shou-Ch’ang builds a form of armillary ring, a metal circle representing the equator and used to observe the stars. |
| 50 BC to 41 BC |
Andronikos of Kyrrhestes builds the Tower of the Winds in Athens. It includes early sundials in the eight principal directions.The Roman architect Vitruvius (Marcus Vitruvius Pollio) includes information on sundials in his “De Architectura” on engineering and architecture. He uses the word analemma in referring to a form of orthographic projection. |
| 10 BC | Augustus erects a monumental sundial in Rome. The 15 metre stone obelisk gnomon, brought from Egypt and now in the Piazza de Populo, commemorated victory over Mark Antony and Cleopatra, and was surrounded by numerous lines for the hours, days and months. |
| 46 BC | Julius Caesar, acting on the advice of Greek astronomer Sosigenes (court astronomer of Egypt), introduces the Julian calendar. To account for previous errors, year 46 BC has 445 days. |
| 84 AD | Fu An and Chia Kuei improve on the armillary sphere for locating stars by combining an equatorial ring with an ecliptic one. |
| 100 to 109 | Bhaskara measures the diameter of the sun.Menelaus of Alexandria’s “Spherics” establishes spherical trigonometry. |
| 140 to 149 | Ptolemy, (Claudius Ptolemaeus) the last great astronomer of the Alexandrian school in Egypt, writes the book “Megale Syntaxis tes astronomias” (Great Astronomical composition) later called the Almagest by the Arabs. It includes his model of the solar system based on circles and epicycles. |
| 450 approx | Palladius Rutilius Taurus Emilianus in Sicily writes “De Re Rustica”, giving shadow lengths for this southerly location. |
| 497 | Aryabhata I (in India) recalculates Greek measurements of the solar system. He largely accepts Ptolemy’s model, but also proposes that the Earth rotates. |
| 530 | Simplicius of Cilicea comments on Plato’s 1000-year old theory that the heavenly bodies have uniform circular motions. |
| 580 approx | Gregory of Tours writes “De Cursu Stellarum” (The tracks of the stars) providing monks with a set of rules for saying their nocturnal prayers. |
| 664 | The Synod of Whitby, attended by Bede and other leading monks, determine the inaccuracies in the current calendar. The term “Anno Domini” (in the year of Our Lord) is introduced. |
| 650 approx | Pope Sabinianus commands that dials should be placed on churches to show the hour of the day. |
| 670 to 679 | The Venerable Bede (an English scholar at Jarrow, Northumbria), writes on the calendar, marine tides and the shape of the Earth in his English history “Historica Ecclesiastica gentis Anglorum”. He also gives an accurate table of shadow lengths. |
| 700 approx | The oldest surviving Anglo-Saxon sundials in England are built at Bewcastle (Cumbria) and Escomb (Co. Durham). |
| 807 | Einhard’s “Life of Charlemagne” provides the first Western reference to sunspots |
| 827 | Egyptian astronomer and geographer Afragamus (Abu-al-‘Abbas al Farghani) presents Ptolemy’s works clearly in Arabic. |
| 850 approx | The “Tiberius Horologium” is written by monks in northern England, giving accurate shadow lengths at different times throughout the year. |
| 880 to 910 | Arabian astronomer Albategnius re-calculates the length of the year and provides a refined measurement of the precession of the equinoxes. |
| 890 to 900 | Thabit Ibn Qurra (Baghdad) writes the manuscripts “Description of the figures formed by the extremity of a gnomon in its passage on a horizontal plane, in all the days, in all the places” and “Book on the instruments which indicate the hours, called solar dials”. |
| 940 to 950 | The Dunhuang star map is produced in China. It uses a form of projection later used by Mercator. |
| 1000 to 1010 | Ibn Yunus’s “The large astronomical tables of al-Hakim” contains accurate astronomical and mathematical tables based on 200 years of observations. |
| 1010 to 1029 | Alhazen (b. Basra, Iraq; d. Cairo) explains the cause of twilight as atmospheric refraction, develops quartz lenses and discovers the properties of parabolic mirrors. |
| 1070 to 1090 | Arzachel suggests that planetary orbits are elliptical. |
| 1086 | Chinese scientist Shen Kua’s “Dream pool essays” contains the first known reference to a magnetic compass for navigation. |
| 1092 | In China, Su Sung builds a giant water clock and mechanical armillary sphere. |
| 1100 approx. | Omar Khayyám ( Persia, c1048-1131) calculates the year length correct to about 1 minute. |
| 1100 to 1110 | Chinese astronomers build a stone planisphere of the heavens that correctly demonstrates the cause of solar and lunar eclipses. |
| 1126 | Adelard of Bath (England) translates Al-Khowarizmi’s “Astronomical tables” from the Arabic. |
| 1200-1300 | Returning Crusaders bring Islamic knowledge of the polar gnomon and many dial types to Europe. |
| 1220 | At the University of Paris, John of Holywood (Sacrobosco) writes “Sphaera mundi” (spheres of the world) introducing Ptolemy’s Almagest to Europe and explaining solar and lunar eclipses. |
| 1265-7 | Roger Bacon, a Franciscan friar educated in Paris and Oxford, writes on many subjects including astronomy and astrology, and proposes the need for calendar reform to Pope Clement IV. |
| 1270 to 1280 | Kuo Shou-Ching builds the first torquetum, the first astronomical device to use an equatorial mounting. |
| 1276 | Chinese astronomer Zhou Kung sets up a 12 metre gnomon for measuring the sun’s shadow. |
| 1280 | Abul Hhasan al Marrakushi writes a manuscript (translated into French by J. J. Sedillot in 1834) describing many types of dials and the methods for calculating them. |
| 1288 | Jacob ben Machir ibn Tibbon (Latin name Profatius, 1236-1305) designs a new quadrant of “quadrans novus” which allows the time to be found by the altitude of the sun or another star. |
| 1290 to 1299 | William of Saint-Cloud determines the obliquity of the ecliptic from the sun’s position at the solstice – he is only 2 arc-mins in error. |
| 1310 to 1319 | The first mechanical clocks appear in Europe and unequal hours begin to be displaced by equal hours. |
| 1348 to 1364 | Giovanni de Dondi of Padua (Italy) builds his famous Astrarium, or astronomical clock. Using Ptolemeic astronomy, it shows the orbits of the Sun, Moon and the five known planets, together with many other features including sunrise and sunset. |
| 1391 | Geoffrey Chaucer’s “A treatise on the astrolabe” shows how this instrument can compute the position of a star. He describes a monk using a chilindrum (shepherd’s dial) in his “Canterbury Tales”. |
| 1438 | The “horary quadrant” is invented by Johannes von Gmunden (1384-1442) as a simplified version of the old Islamic quadrant specifically for time-telling. |
| 1471 to 1474 | Regiomontanus (b. Johann Müller (1436-76) and adopted the name “the man from the Royal Mountain” from his birthplace in Königsberg) builds an observatory in Nuremberg, Germany. He publishes “Ephemerides astronomicae”, although it is not until later editions that the tables of solar declination used by navigators (including Christopher Columbus) are included. His “universal rectilinear analemma” is a form of card dial. The Nuremberg group make much use of Ptolemy’s rulers, and further develop the torquetum. |
| 1475 | Italian mathematician and astronomer Paolo Toscanelli installs a 100 metre noon line in Filippo Brunelleschi’s newly completed dome of the Santa Maria del Fiore, Florence. |
| 1514 | Copernicus writes the first version of his heliocentric theory, although it is not published until 1543. in Filippo Brunelleschi’s newly completed dome of the Santa Maria del Fiore, Florence. |
| 1514 | Copernicus writes the first version of his heliocentric theory, although it is not published until 1543. |
| 1517 | Nicholas Kratzer comes to England from Austria to be horologist to King Henry VIII. He later makes several famous dials and is painted by Hans Holbein making a polyhedral dial. |
| 1525 | Petrus Apianus publishes his book “Cosmographie” It includes a drawing of a universal diallist’s companion, a form of analogue computer for giving sunrise/sunset times, declinations etc. He supports the Aristotelian model of crystal spheres carrying the Sun, Moon and planets. |
| 1530 | Gemma Frisius’ globe manual “De Principuiis Astronomae et Cosmographiae” describes the use of spherical gnomon for providing equal hours. |
| 1532 | Oronce Finé (Paris) publishes his “Protomathesis”, giving a comprehensive treatment of dial types. |
| 1533 | Dutch geographer Reiner Gemma is the first to point out that comparisons of clock and solar time can be used to find longitude. |
| 1550 | Joanne de Rojas develops the universal astrolabe, based on the orthogonal projection. |
| 1560 | Oronce Finé (Paris) publishes “De Solaribus Horologiis”. |
| 1582 | Pope Gregory XIII reforms the calendar, resulting in 1582 having only 354 days. The Gregorian calendar is adopted by most of mainland Europe. |
| 1583 | Joseph Justus Scaliger (Lot-et-Garonne, France) devises a system of counting days from 4713 BC, later to be incorporated in the Julian Day count. |
| 1593 | Thomas Fale publishes “Horologiographica: The art of Dialling”, the earliest work devoted to the subject of making dials in the English language. |
| 1595 | Mercator’s “Atlas sive cosmographicae” is published posthumously. |
| 1598 | Valentin Pini discusses Ptolemy and introduces an armillary dial |
| 1606 | Elias Allen, one of the greatest dial and scientific instrument makers of the era, is established near Fleet Street, London. |
| 1609 | Kepler’s “Astonomia nova” contains his views that the planets orbit the Sun in ellipses, sweeping out equal angles in equal time intervals (Kepler’s Law).Galileo builds his first telescope |
| 1624 | William Oughtred devises the double horizontal dial, manufactured to very high quality by Elias Allen. |
| 1631 | French engineer Pierre Vernier invents the vernier scale. |
| 1633 | The Roman Catholic Inquisition forces Galileo to recant his Copernican view that the Earth orbits the sun. |
| 1638 | Samuel Foster, of Gresham College, London, publishes “The Art of Dialling”, including the first description of scales for drawing a dial. |
| 1654 | Samuel Foster describes a number of new types of dial, including analemmatic and diametral. |
| 1655 | Gian Domenico Cassini builds the great sundial in Bologna cathedral with which he measures new values for the obliquity of the ecliptic. |
| 1657 | George Serle puts dialling scales onto a ruler and describes them in his article “Dialling Universal”. |
| 1664 | René Descartes’ “Le Monde”, published posthumously, affirms the Copernican theory. |
| 1670 | G. Mouton proposes the use of one-sixtieth part of a degree of the meridian as the unit of length. |
| 1675 | The Greenwich Observatory is founded by King Charles II. John Flamsteed is the first Astronomer Royal and calculates a table of the EoT. |
| 1685 | John Twysden publishes his “Use of the Great Planisphere called the Analemma”. |
| 1687 | Newton publishes the “Principia” including the law of universal gravitation. |
| 1714 | The British Parliament sets a prize of £20,000 for a method for finding longitude at sea. |
| 1724 | Jai Singh, Rajah of Jaipur, builds his great sundials in India. |
| 1725 | Antoine Thiout (Vesoul, France) designs a clock to show solar time. It is called the equation clock. |
| 1740 | The modern figure-8 form of the analemma curve is conceived by Jean Paul Grandjean de Fouchy, secretary of the Académie des Sciences, Paris. |
| 1748 | James Bradley discovers the nutation of the Earth’s axis. |
| 1749 | Jean le Rond d’Alembert gives the first mathematical description of the regular changes in the Earth’s rotational axis. |
| 1750 | The Greenwich Meridian is established at its current position by James Bradley. It had initially been 20.4 metres further west. |
| 1752 | Great Britain finally adopts the Gregorian calendar, and moves the start of the civil year to 1 January.Johann Tobias Mayer (Marbach, Germany) publishes lunar ephemeris with sufficient accuracy to find longitude. |
| 1754 | John Dollond (London) invents the heliometer and uses it to find the semidiameter of the sun. |
| 1756 | J. J. de Lalande (Ain, France) designs the oldest analemmatic dial still in existence, in Brou churchyard. |
| 1759 | John Harrison completes his “Number Four” clock, later used to win the Longitude prize. |
| 1764 | Lagrange explains the libration of the Moon. |
| 1767 | Astronomer Royal Nevil Maskelyne publishes the first annual ephemeris which will later become the “Nautical Almanac”. |
| 1792 | Jean-Baptiste Delambre and Pierre Mechain measure the arc of the meridian from Dunkirk to Barcelona, leading to the new definition of a metre. |
| 1812 | Laplace gives an accurate calculation for sunrise, using 5000 years of data. |
| 1837 | The London and Birmingham Railway deploy Cooke and Wheatsone’s new telegraph signalling and use “railway time” for trains from Euston.Charles Dickens mentions railway time in “Dombey and Son”. |
| 1838 | France adopts mean time rather than solar time for civil purposes. |
| 1843 | Edward Dent (England) patents the dipleidoscope. |
| 1847 | Railway time (now used by most railway companies) is declared “a dangerous innovation” in The Times. |
| 1848 | Sir Charles Wheatstone (1802-1875) invents the polarised light dial. |
| 1852 | Exeter Cathedral clock is put forward 14 minutes to read London Time. There are still many places using local time, e.g. Plymouth and Oxford, plus rural areas. |
| 1862 | Léon Foucault measures the distance from the Earth to the Sun. |
| 1867 | Lloyd Mifflin is granted a US patent for an analemma-shaped gnomon to tell mean time. |
| 1872 | Mrs Gatty publishes “The Book of Sundials”, giving examples of many dials and their mottoes. |
| 1880 (Aug) | The Definition of Time Act finally establishes Greenwich time as the basis for civil timekeeping throughout Great Britain. |
| 1884 (Oct) | The International Meridian Conference in Washington, DC, sets the Prime Meridian through Greenwich and defines the standard time zones. It also established the mean solar day, and voiced a desire to extend the use of the decimal system. |
| 1892 | John Oliver is granted a British patent for a gnomon shaped to account for the EoT |
| 1900 | The last French railway stations abandon the use of heliochronometers for setting their clocks. |
| 1905 | The first time signals are broadcast by the US Naval Observatory, Washington D.C., to specialist radio receivers. |
| 1911 | France finally recognises Greenwich as the origin of longitude (but avoids referring to it as the Prime Meridian). |
| 1922 | Hugo Michnik invents the bifilar sundial. |
| 1924 | The BBC begins the world’s first public time broadcast by transmitting the time “pips”, having started with a piano playing the Westminster chimes two years earlier. |
| 1960 | The ephemeris second is set as the basic unit of time |
| 1974 | Robert Gundlach is awarded a US patent for a shadowless sundial; this design has some similarities to the later CD dial. |
| 1981 | Boon obtains a US patent for a digital sundial. It is later improved by R L Kellogg. |
| 1984 | The second is redefined based on atomic rather than Earth-rotation principles, and dynamical time replaces ephemeris time. |
| 1989 | The British Sundial Society is formed. |
| 1994 | The North American Sundial Society is formed. |
| 1999 | The diffraction sundial is invented by M. Catamo and C. Lucarini. |
| 2000 | The Japanese Sundial Society is formed. |