Gardom's Edge Monolith

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Published: 09 April 2012

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Gardom Edge Monolith [photo courtesy of Dan Brown, Nottingham Trent University]

A two meter standing stone at Gardom’s Edge may be an astronomically aligned monolith set up during the Neolithic period 2,500 – 1,500 BCE to recognize the summer solstice.   According to Dan Brown, Andy Alder and Elizabeth Bemand of Nottingham Trent University, “Such an astronomically aligned stone could be described as a seasonal sundial … However it is not intending to mark local time during a day or measure exact dates during a year.  Rather the seasonal shadow casting allows for the display of cosmological knowledge such as the ‘death’ and ‘rebirth’ of the Sun”…

The upward facing north slope of the stone remains in shadow until near the time of Summer solstice.  Today the stone points south at an upward tilt of 58.3° +/- 2.9°, seemingly aimed at the highest rise of the summer sun, computed for the Gardom Edge latitude of 53.26° as 60.7° in Neolithic times.

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Pantheon Sundial

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Published: 02 August 2011

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One of the most iconic buildings in the world, the Pantheon in Rome is an enduring testament to the power and glory of ancient Rome.  At the same time, it has also always posed something of a mystery.  The only source of natural lighting is a thirty-foot diameter hole at the very top of the hemispherical dome, often referred to as the "oculus".

Working since 2009, scholars Guilio Magli and Robert Hannah discovered that at midday on the equinoxes, a shaft of circular light shines through the oculus and illuminates the Pantheon's entrance. 

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Early Astronomers

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Published: 13 March 2011

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[photo credit: Andrew Caswell and Robert Cockburn of The Daily Telegraph ]

Ask a person what is the earliest evidence of humans building structures to mark significant celestial events, and one offer "Stonehenge".  But there may be a structure built thousands of years early according to some experts in Australia.

A site "down under", name Wurdi Youang, estimated to be older than 10,000 years, has a strange arrangement of stones with alignments toward solstices and equinox that has been scrutinized by several eminent Australian scientists.  They conclude that the placement and alignment of the stones is not an accident and there is a perfect alignment with the setting sun on the mid-summer day. Understandably, the exact location of the site is a well-guarded secret, but it is known to be west of Melbourne approximately 80 kilometers.

Prosciutto di Portici Sundial's Owner

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Published: 10 June 2025

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The Prosciutto di Portici Sundial, more often called the Portici Ham Sundial, dates from the first century somewhere between  8 BCE to 79 CE.  This small silvered bronze dial was uncovered on 11 June, 1755 in the ruins of Herculaneum (current day Portici) in the "Villa of the Papyri", buried in volcanic ash and charred papyri from the eruption of Mount Vesuvius in 79 CE. The form of the sundial, which resembles a ham, has been extensively studied.  It is an altitude dial with similarities to the cylindrical sundial. 

Live Science reporter Kristina Killgrove writes, "Historians have long assumed that the owner of the Villa of the Papyri was L. Calpurnius Piso Caesoninus, the father-in-law of Julius Caesar."  https://www.livescience.com/archaeology/romans/prosciutto-di-portici-a-portable-sundial-that-looks-like-a-pork-leg-and-it-was-likely-owned-by-julius-caesars-father-in-law-before-mount-vesuvius-erupted

Calpurnius likely commissioned the Epicurean philospher Philodemus to drave the numerous charred scrolls at Villa of the Papyri.  Killgrove commented that "This may explain why the Roman pocketwatch was shaped like a ham. For adherents of Epicurean thought, the lowly pig was often used as a metaphor, as it was seen as a naturally pleasure-seeking creature.

To clarify the use of the dial and the drawn lines attributed in the article as "hours before or after sunset" were actually temporal hours. The lines measuried the hours from sunrise to sunset. Temporary (ancient) hours go across the dial face and vertical lines represent the boundary between the zodiac signs representing the twelve months of the year.  In this dial the twelve months have been “folded” and the month pair labeled between the lines: IUN-IU (June-July), MA-AU (May-August), AP-SE (April-September), MA-OC (March-October), FE-NO (February-November) and JA-DE (January-December).  Notice that both July and August are used and the longest shadows occuring at the end of June while the shortest occur at the end of December.  Further, since July and August are named, the dial was created after the reign of Julius and Augustus Caesar, and in particular when Augustus renamed the month Sextilis to August in 8 BCE.

The Ham dial has a fixed gnomon, the flattened piece at middle-left in the photo.  When properly working, the gnomon is actually much longer and the tip set a specific distance above the dial face and at the upper left corner of the hour-date lines.  To read the time, the dial is rotated from a string at top of the dial until the shadow falls on the vertical date line (or distance between) corresponding to the date. Like the cylindrical sundial, time is read from the downward shadow of the tip crossing the temporary hour line.

The Ham dial also has “folded” hour lines that run across the dial to tell temporary (ancient) hours.  The lines are from top to bottom are for sunrise, 1^st/11^th, 2^nd/10^th, 3^rd/9^th, 4^th/8^th, 5^th/7^th, and at bottom, the 6^th hour line for mid-day.

Historic Sundials of Andalusia

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Published: 16 November 2024

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Esteban Martínez Almirón has published a new book Historical Sundials: Forgotten Andalusian Treasures (Relojes de Sol Históricos Tesoros Andaluces Olvidados) In it he reviews over 400 sundials from the Andalucian region of southern Spain Originally to celebrate the 25th year of the website https://relojandalusi.org/

Esteban Martínez Almirón began showing his sundial drawings on the site. Ultimately more than 60 drawings are in his book, and many are posted on the @stbnart Instagram site. He presents the historical sundials using the themes according to geographical location and building type (e.g. on farms or country houses for daily time telling; churches, cathedrals and other sanctuaries; and civil buildings and public places). Unfortunately many dials have been lost to history and no longer exist.

Martínez Almirón looks briefly at portable sundials of Andalusia, particularly in Sierra de Huelva, the city of Ubeda (where its Renaissance sundials stand out) and the dials of the "New Populations" ("Nuevas Poblaciones"). The book is self-published. If you are interested in purchasing a copy, you can visit https://relojandalusi.org/relojes-de-sol-historicos/. The book cost is 12 euros plus shipping. Text in Spanish.