A double sunset is a rare astro-geographical phenomenon, in which the Sun appears to set twice in the same evening from a specific viewing-point. A double sunrise may also occur in a similar situation. Such phenomena may have been regarded as significant in prehistoric times, and double sunsets have been discussed in the context of archaeoastronomy by researchers such as Alexander Thom. [1]
Orasso, a small village near the Italy-Switzerland border, sees two sunrises and two sunsets during the winter because of Mount Riga. [2]
In the town of Güímar in Tenerife a double sunset has been observed in alignment with the local pyramids at summer solstice. [3] In Spanish the phenomenon is described as a doble puesta. The site of the pyramids appears to have been used by the Guanche prehispanic culture, but the structures themselves have been dated to the 19th century.
A well-documented example of a double or occulted sunset is associated with Leek, Staffordshire, England. The phenomenon is viewable from the town on and around the summer solstice in good weather. [4] [5] [6]
The first published mention of the Leek double sunset was made in 1686 by Dr Robert Plot in his book The Natural History Of Stafford-Shire. [7] The phenomenon would have been visible well before the seventeenth century. However, the alignment of sun and landscape is subject to change over the centuries as it is affected by the Earth's axial precession. This was realised by Plot who suggested that the sunset could be used to measure the obliquity of the ecliptic. [8] [lower-alpha 1]
The traditional location for observing the phenomenon, as described by Plot, is the churchyard belonging to the parish church of St Edward the Confessor. The church is a medieval building, and it has been conjectured that the churchyard is an example of an ancient sacred site having been Christianised. Because of the chronology of the changing alignment, it seems that the site could not have been a viewing-point for the double sunset before the Iron Age. The first people to view the phenomenon may have been the area's Iron Age inhabitants. [8]
From a particular point in the churchyard, the whole of the Sun set on the summit of Bosley Cloud, a millstone grit hill six miles to the northwest. The Sun partially reappeared from The Cloud's steep northern slope and soon afterwards set for a second and final time on the horizon. [9] The spectacle was last reliably witnessed, and filmed, from the churchyard in 1977, [10] [11] but is no longer visible from the location because of tree interference. [12] [13] It is, however, still observable from Leek on and around the summer solstice from the road to Pickwood Hall, off Milltown Way, [14] and from Lowe Hill on the outskirts of the town. [15] Better viewing points, though, are from the A 523, above Rudyard Lake, [16] and Woodhouse Green, [17] both of which are nearer to The Cloud and therefore enable a larger proportion of the sun to reappear.
In the 1950s Alexander Thom surveyed a megalithic site at Kintraw, a locality on the mainland of Scotland, which is in an area rich in prehistoric sites. [19] Thom interpreted the site at Kintraw as a viewing point of a double sunset on the island of Jura (both the island and the mainland site are in Argyll and Bute). [1] The proposed alignment is to a notch at a distance of 28 miles between the mountains of Beinn Shiantaidh and Beinn a' Chaolais which are visible from Kintraw. [20]
Thom described the site as a type of midwinter observatory, but his interpretation has been the subject of controversy, one point at issue being the visibility of the midwinter notch: a higher observation point is needed to see the midwinter notch on Jura over a nearby ridge. Euan MacKie, recognising that Thom's theories needed to be tested, excavated at the site in 1970 and 1971, and found evidence for an observation platform. [21]
Archaeoastronomy is the interdisciplinary or multidisciplinary study of how people in the past "have understood the phenomena in the sky, how they used these phenomena and what role the sky played in their cultures". Clive Ruggles argues it is misleading to consider archaeoastronomy to be the study of ancient astronomy, as modern astronomy is a scientific discipline, while archaeoastronomy considers symbolically rich cultural interpretations of phenomena in the sky by other cultures. It is often twinned with ethnoastronomy, the anthropological study of skywatching in contemporary societies. Archaeoastronomy is also closely associated with historical astronomy, the use of historical records of heavenly events to answer astronomical problems and the history of astronomy, which uses written records to evaluate past astronomical practice.
The green flash and green ray are meteorological optical phenomena that sometimes occur transiently around the moment of sunset or sunrise. When the conditions are right, a distinct green spot is briefly visible above the Sun's upper limb; the green appearance usually lasts for no more than two seconds. Rarely, the green flash can resemble a green ray shooting up from the sunset or sunrise point.
Leek is a market town and civil parish in Staffordshire, England, on the River Churnet 10 miles (16 km) north east of Stoke-on-Trent. It is an ancient borough and was granted its royal charter in 1214.
Newgrange is a prehistoric monument in County Meath in Ireland, located on a rise overlooking the River Boyne, eight kilometres west of the town of Drogheda. It is an exceptionally grand passage tomb built during the Neolithic Period, around 3200 BC, making it older than Stonehenge and the Egyptian pyramids. Newgrange is the main monument in the Brú na Bóinne complex, a World Heritage Site that also includes the passage tombs of Knowth and Dowth, as well as other henges, burial mounds and standing stones.
The Clava cairn is a type of Bronze Age circular chamber tomb cairn, named after the group of three cairns at Balnuaran of Clava, to the east of Inverness in Scotland. There are about 50 cairns of this type in an area round about Inverness. They fall into two sub-types, one typically consisting of a corbelled passage grave with a single burial chamber linked to the entrance by a short passage and covered with a cairn of stones, with the entrances oriented south west towards midwinter sunset. In the other sub-type an annular ring cairn encloses an apparently unroofed area with no formal means of access from the outside. In both sub-types a stone circle surrounds the whole tomb and a kerb often runs around the cairn. The heights of the standing stones vary in height so that the tallest fringe the entrance and the shortest are directly opposite it.
Alexander Thom was a Scottish engineer most famous for his theory of the Megalithic yard, categorisation of stone circles and his studies of Stonehenge and other archaeological sites.
Cup and ring marks or cup marks are a form of prehistoric art found in the Atlantic seaboard of Europe (Ireland, Wales, Northern England, Scotland, France, Portugal, and Spain – and in Mediterranean Europe – Italy, Azerbaijan and Greece, as well as in Scandinavia and in Switzerland.
Ballochroy is a megalithic site in Kintyre on the Argyll peninsula in Scotland. It consists of three vertical stones, side by side, aligned with various land features 7–19 miles (11–31 km) away.
The Pyramids of Güímar are six rectangular pyramid-shaped, terraced structures built from lava stone without the use of mortar. They are located in the district of Chacona, part of the town of Güímar on the island of Tenerife in the Canary Islands, Spain. The structures have been dated to the 19th century AD and they may originally have been a byproduct of contemporary agricultural techniques. These pyramids stand as high as 12 metres (39 ft).
Dowth is a Neolithic passage tomb near the River Boyne in County Meath, Ireland. It is one of the three main tombs of the Brú na Bóinne World Heritage Site, along with Newgrange and Knowth. Its features align it with the other passage tombs, which date from around 3200 BC. Unlike its bigger neighbours, Dowth has mostly been left as a ruin, although its smaller inner chambers are largely intact. The Royal Irish Academy carried out a botched excavation in 1847, leaving a large crater in the mound that has never been repaired.
Thorpe Cloud is an isolated limestone hill lying between the villages of Thorpe and Ilam on the Derbyshire/Staffordshire border at the southern end of Dovedale. It is a popular hill amongst the many day-trippers who visit the area, and provides a fine viewpoint north up the dale and south across the Midland plain.
Ale's Stones is a megalithic monument in Scania in southern Sweden. It is a stone ship, oval in outline, with the stones at each end markedly larger than the rest. It is 67 m (220 ft) long formed by 59 large boulders, weighing up to 5 tonnes each.
The prehistoric monument of Stonehenge has long been studied for its possible connections with ancient astronomy. The site is aligned in the direction of the sunrise of the summer solstice and the sunset of the winter solstice, and its latitude in respect to the Great Pyramid and Equator is precisely defined by the silver ratio. Archaeoastronomers have made a range of further claims about the site's connection to astronomy, its meaning, and its use.
Manhattanhenge, also called the Manhattan Solstice, is an event during which the setting sun or the rising sun is aligned with the east–west streets of the main street grid of Manhattan, New York City. The astrophysicist Neil deGrasse Tyson claims to have coined the term, by analogy with Stonehenge. The sunsets and sunrises each align twice a year, on dates evenly spaced around the summer solstice and winter solstice. The sunset alignments occur around May 28 and July 13. The sunrise alignments occur around December 5 and January 8.
The winter solstice, also called the hibernal solstice, occurs when either of Earth's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere. For that hemisphere, the winter solstice is the day with the shortest period of daylight and longest night of the year, and when the Sun is at its lowest daily maximum elevation in the sky. Each polar region experiences continuous darkness or twilight around its winter solstice. The opposite event is the summer solstice.
The Cloud or Bosley Cloud is a prominent hill on the border between Cheshire and Staffordshire a couple of miles west of the Peak District National Park boundary.
The Bryn Gwyn Stones or Bryn Gwyn Standing Stones are neolithic stones in Brynsiencyn on Anglesey.
St Edward the Confessor's Church is an active Anglican church in Leek, Staffordshire, England. The building, which dates back to the 13th century, is listed Grade II*.
An axial stone circle is a megalithic ring of stones of a particular design found in County Cork and County Kerry in southwest Ireland. Archaeologists have found it convenient to consider the axial five-stone circle and axial multiple-stone circle separately. The circle has an approximate axis of symmetry aligned in a generally northeast–southwest direction. The stone at the southwest side of the circle, rather than being an upright orthostat like all the rest, is a slab lying horizontally with its long thin edge along the circumference of the ring. Because it marks the axis of the circle it is called the axial stone.