History of sundials

A sundial is a device that measures time by the position of the Sun. It measures local solar time. Before the coming of the railways in the 1830s and 1840s, local time as displayed on a sundial was used by government and commerce.

Ancient sundials

World's oldest sundial, from Egypt's Valley of the Kings (c. 1500 BC), used to measure work hours.

The earliest sundials known from the archaeological finds are the shadow clocks (1500 BC) in ancient Egyptian astronomy and Babylonian astronomy. Not, as incorrectly suggested, obelisks at the temples only serving as a memorial in honor of the pharaoh to whom it was devoted. Presumably, humans were telling time from shadow-lengths at an even earlier date, but this is hard to verify. In roughly 700 BC, the [Old Testament] describes a sundial — the "dial of Ahaz" mentioned in Isaiah 38:8 and II Kings (possibly the earliest account of a sundial that is anywhere to be found in history) — which was likely of Egyptian or Babylonian design. Sundials are believed to have existed in China since ancient times, but very little is known of their history. There is an early reference to sundials from 104 BCE in an assembly of calendar experts.

Hemispherical Greek sundial from Ai Khanoum, Afghanistan, 3rd-2nd century BCE.

The ancient Greeks developed many of the principles and forms of the sundial. Sundials are believed to have been introduced into Greece by Anaximander of Miletus, c. 560 BC. According to Herodotus, the Greeks sundials were initially derived from the Babylonian counterparts. The Greeks were well-positioned to develop the science of sundials, having founded the science of geometry, and in particular discovering the conic sections that are traced by a sundial nodus. The mathematician and astronomer Theodosius of Bithynia (ca. 160 BC-ca. 100 BC) is said to have invented a universal sundial that could be used anywhere on Earth.

The Romans adopted the Greek sundials, and the first record of a sun-dial in Rome is 293 BC according to Pliny. Plautus complained in one of his plays about his day being "chopped into pieces" by the ubiquitous sundials. Writing in ca. 25 BC, the Roman author Vitruvius listed all the known types of dials in Book IX of his De Architectura, together with their Greek inventors. All of these are believed to be nodus-type sundials, differing mainly in the surface that receives the shadow of the nodus.

• the hemicyclium of Berosus the Chaldean: a truncated, concave, hemispherical surface
• the hemispherium or scaphe of Aristarchus of Samos: a full, concave, hemispherical surface
• the discus (a disc on a plane surface) of Aristarchus of Samos: a fully circular equatorial dial with nodus
• the arachne (spiderweb) of Eudoxus of Cnidus or Apollonius of Perga: half a circular equatorial dial with nodus
• the plinthium or lacunar of Scopinas of Syracuse: an example in the Circus Flaminius)
• the pros ta historoumena (universal dial) of Parmenio
• the pros pan klima of Theodosius of Bithynia and Andreas
• the pelekinon of Patrocles: the classic double-bladed axe design of hyperbolae on a planar surface
• the cone of Dionysodorus: a concave, conical surface
• the quiver of Apollonius of Perga
• the conarachne
• the conical plinthium
• the antiboreum: a hemispherium that faces North, with the sunlight entering through a small hole.

The Romans built a very large sundial in 10 BC, the Solarium Augusti, which is a classic nodus-based obelisk casting a shadow on a planar pelekinon.

The Greek dials were inherited and developed further by the Islamic Caliphate cultures and the post-Renaissance Europeans. Since the Greek dials were nodus-based with straight hour-lines, they indicated unequal hours — also called temporary hours — that varied with the seasons, since every day was divided into twelve equal segments; thus, hours were shorter in winter and longer in summer. The idea of using hours of equal time length throughout the year was the innovation of Abu'l-Hasan Ibn al-Shatir in 1371, based on earlier developments in trigonometry by Muhammad ibn Jābir al-Harrānī al-Battānī (Albategni). Ibn al-Shatir was aware that "using a gnomon that is parallel to the Earth's axis will produce sundials whose hour lines indicate equal hours on any day of the year." His sundial is the oldest polar-axis sundial still in existence. The concept later appeared in Western sundials from at least 1446.

The custom of measuring time by one's shadow has persisted since ancient times. In Aristophanes' play, Assembly of Women, Praxagora asks her husband to return when his shadow reaches 10 feet (3.0 m). The Venerable Bede is reported to have instructed his followers in the art of telling time by interpreting their shadow lengths.

Renaissance sundials

The onset of the Renaissance saw an explosion of new designs. Italian astronomer Giovanni Padovani published a treatise on the sundial in 1570, in which he included instructions for the manufacture and laying out of mural (vertical) and horizontal sundials. Giuseppe Biancani's Constructio instrumenti ad horologia solaria (ca. 1620) discusses how to make a perfect sundial, with accompanying illustrations.

The oldest sundial in England is incorporated into the Bewcastle Cross ca. early 8th Century AD.

Designers of the Taipei 101, the first record-setting skyscraper of the 21st century, brought the ancient tradition forward. The tower, tallest in the world when it opened in Taiwan in 2004, stands over half a kilometer in height. The design of an adjoining park uses the tower as the style for a huge horizontal sundial.

Gallery

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  Old sundial located in the Great Mosque of Kairouan also known as the Mosque of Uqba, in Kairouan, Tunisia.

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  A Scottish gravestone bearing a sundial. The instrument has often doubled as a memento mori.

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  A medieval mass dial (minus its gnomon) at St. Mary, Bibury; also known as a scratch dial, it was used to tell the times of Mass.

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  This sundial displays a likeness of Father Time. Its motto quotes Robert Browning: "Grow old along with me; the best is yet to be."

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  Marble equatorial sundial in the Europapark of Klagenfurt on Lake Woerth, Carinthia, Austria

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  Martin Bernhardt created a special gnomon for an equatorial sundial which adjusts for the equation of time and that allows one to read the time without knowing the date, to a precision of less than a minute.

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  The Giant Sundial of Jantar Mantar in Jaipur, India, also known as the Samrat Yantra (The Supreme Instrument), stands 27m tall. Its shadow moves visibly at 1 mm per second, or roughly a hand's breadth (6 cm) every minute. 26°55′29″N 75°49′29″E

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  A modern hemispherium in Gyeongbok Palace in Seoul, South Korea. 37°34′43″N 126°58′38″E The tip of the pointer serves as the nodus; the height of the nodus-shadow within the bowl gives the time of the year. Since the picture was taken on 24 November, the sun is low in the sky, and the nodus-shadow higher in the bowl.

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  Jantar Mantar observatory (Delhi) is a giant version of the spherical sundial.

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  Several sundials arrayed on the faces of a cube. The styles are all parallel and meant to be aligned with the Earth's rotation axis. Such an array of sundials is not self-aligning, however.

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  High precision (±30 seconds) sundial in Belgium (Google Earth)

See also

• Foucault pendulum
• Francesco Bianchini
• Horology
• Scottish sundial — the ancient renaissance sundials of Scotland.
• Tide (time) — divisions of the day on early sundials.
• Wilanów Palace Sundial, created by Johannes Hevelius in about 1684.

References

Notes

Bibliography

• Earle AM (1971). Sundials and Roses of Yesterday. Rutland, VT: Charles E. Tuttle. ISBN 0-8048-0968-2. LCCN 74142763.  Reprint of the 1902 book published by Macmillan (New York).
• A.P.Herbert, Sundials Old and New,Methuen & Co. Ltd, 1967.
• Mayall RN, Mayall MW (1994). Sundials: Their Construction and Use (3rd ed.). Cambridge, MA: Sky Publishing. ISBN 0-933346-71-9. 
• Hugo Michnik, Theorie einer Bifilar-Sonnenuhr, Astronomishe Nachrichten, 217(5190), p. 81-90, 1923
• Rohr RRJ (1996). Sundials: History, Theory, and Practice (translated by G. Godin ed.). New York: Dover. ISBN 0-486-29139-1.  Slightly amended reprint of the 1970 translation published by University of Toronto Press (Toronto). The original was published in 1965 under the title Les Cadrans solaires by Gauthier-Villars (Montrouge, France).
• Frederick W. Sawyer, Bifilar gnomonics, JBAA (Journal of the British Astronomical association), 88(4):334–351, 1978
• Gerard L'E. Turner, Antique Scientific Instruments, Blandford Press Ltd. 1980 ISBN 0-7137-1068-3
• J.L. Heilbron, The sun in the church: cathedrals as solar observatories, Harvard University Press, 2001 ISBN 978-0-674-00536-5.
• Make A Sundial, (The Education Group British Sundial Society) Editors Jane Walker and David Brown, British Sundial Society 1991 ISBN 0-9518404-0
• Waugh AE (1973). Sundials: Their Theory and Construction. New York: Dover Publications. ISBN 0-486-22947-5. 
• "Illustrating Shadows", Simon Wheaton-Smith, ISBN 0-9765286-8-1, LCN: 2005900674
• "Illustrating More Shadows", Simon Wheaton-Smith, both books are over 300 pages long.

External links

• British Sundial Society- Time line and register
• The Ancient Vedic Sun Dial