Posted by KeighleyAstro on Nov 2, 2024 in Main |

‘Why do we Stargaze’? (The motivations and methods from prehistory to today). Was the title of the presentation delivered at the October meeting of Keighley Astronomical society by Dr Jamie Lees from the School of Physics, Engineering and Technology at the University of York.

Dr Lees introduced himself and stated that he has worked across a wide range of physics projects including astrophysics, nuclear, biophysics and condensed matter research. Alongside this he has had a keen interest in science communication and outreach having worked on several nationwide committees and writing a number of physics books. He brought with him a copy of his latest publication titled ‘Matmatica’ – Mathematics from ancient times to the modern world.

Backed with a visually stunning PowerPoint display Dr lees expertly went through his lecture with no reference to written notes. He commenced with a photograph of the Pleiades or as is more commonly known ‘The seven sisters’. He stated that we know that early mankind was looking at the night sky because we know quite a bit about the very early interpretations of the Pleiades that have been passed down through the ages. The Pleiades feature in the mythology and folklore of different culture spanning several continents and centuries, and where known about as far back as the Bronze Age. Common themes in many of the myths are love, tragedy and the everlasting beauty of the night sky.

In Greek myth the Pleiades were said to be daughters of the titan Atlas and the sea nymph Pleione. Each of the seven prominent stars has its own name: Alcyone, Asterope, Celaeno, Electra, Maia, Merope, and Taygete. Two further bright stars in the cluster are named after Atlas and Pleione.

Dr Lees highlighted ‘Warren Field’; the location of a Mesolithic calendar monument built about 8,000 BCE. It includes 12 pits believed to correlate with phases of the Moon and used as a lunisolar calendar. It is considered to be the oldest lunisolar calendar yet found. It is near Crathes Castle, in the Aberdeenshire region of Scotland. It was originally discovered from the air as anomalous terrain by the Royal Commission on the Ancient and Historical Monuments of Scotland. It was first excavated in 2004.

The pits align on the southeast horizon and a prominent topographic point associated with sunrise on the midwinter solstice (thus providing an annual astronomical correction concerning the passage of time as indicated by the Moon, the asynchronous solar year, and the associated seasons). The Aberdeenshire time reckoner predates the Mesopotamian calendars by nearly 5,000 years.

It was also interpreted as a seasonal calendar because the local prehistoric communities, which relied on hunting migrating animals, needed to carefully note the seasons to be prepared for a particular food source. The Warren Field site is particularly significant for its very early date and the fact that it was created by hunter-gatherer peoples, rather than sedentary farmers usually associated with monument building.

Moving to Mesolithic France. The Lascaux cave is embedded in the Santon limestone massif, its entrance being just below the top of Lascaux hill, c. 90 m above the valley floor of the Vézère. It comprises three long and narrow subterranean galleries in the form of a letter ‘K’ and measuring almost 250 m in length, including what have become known as the Axial Gallery, the Hall of the Bulls, the Chamber of Felines, the Nave, the Apse, and the Shaft. Covering most parts of the cave are numerous monochrome and polychrome paintings and engravings.

The published corpus lists 1963 figures including animals (horse, aurochs, bison, ox, stag, ibex, feline, woolly rhinoceros, bird, bear), an anthropoid, a chimera, some possible abstract representations of plants, and symbols (geometric figures, series and sets of dots etc). Carbon-14 dates (from charcoal used sparingly for painting), pollen analysis and stylistic evaluations suggest that the majority of the rock pictures should be associated with the Lower Magdalenian, c. 17,000–15,000 BP, although it is possible that a few were created much later, in the Mesolithic (up to c. 5000 BC).

A number of the Lascaux pictures have a possible astronomical significance. These include the ‘Chinese horse’ and ‘fronting ibex’ in the Axial Gallery and the ‘crossed bison’ in the Chamber of Felines (natural calendars); the stag-and-horse motif and related dots in the Axial Gallery and the five ‘swimming stags’ in the Nave (astronomical almanacs); the aurochs in the Hall of the Bulls with its clusters of dots (representations of asterisms); and two pictograph panels in the Shaft (cosmography).

Natural calendars. The majority of the animals depicted at Lascaux show seasonal characteristic features: the deer are represented in their rutting season at the start of autumn, the horses at their time of mating and foaling in late winter/early spring, the ibexes at the time when they congregate in same-sex herds during the late summer/early autumn, and so on. These indications of particular seasons are sometimes enhanced by the addition of stylised plants: an example is the ‘Chinese horse’ in the Axial Gallery that is shown in its summer fur, highly pregnant and surrounded by stylised branches, illustrating the time of foaling around summer solstice.

Astronomical almanacs. Some abstract designs associated with ‘seasonal’ animals may relate to astronomical calendars. For example, it is argued that a set of 13 dots and another of 26 appearing beneath a roaring stag and a pregnant horse (representing autumn and spring respectively) in the Axial Gallery represent the 13- and 26-week intervals from the summer solstice to the autumn equinox and then to the spring equinox, each spot counting 7 days.

Representations of asterisms, particularly the Pleiades and Hyades. A cluster of dots above the back of the aurochs (no. 18) in the Hall of the Bulls resembles the Pleiades, while the animal’s eye and surrounding dots resemble Aldebaran (α Tau) and the Hyades, suggesting that the aurochs may be a distant forerunner of the constellation Taurus.

Archaic cosmography. Two pictograph panels in the Shaft have been interpreted as representing the sky panorama as perceived by Magdalenian people from the top of the Lascaux hill at, for example, around midnight around the time of summer solstice in c. 16,500 BP.

The Ishango bone, discovered at the “Fisherman Settlement” of Ishango in the Democratic Republic of the Congo, is a bone tool and possible mathematical device that dates to the Upper Paleolithic era. The curved bone is dark brown in colour, about 10 centimeters in length, and features a sharp piece of quartz affixed to one end, perhaps for engraving. Because the bone has been narrowed, scraped, polished, and engraved to a certain extent, it is no longer possible to determine what animal the bone belonged to, although it is assumed to have been a mammal.

The ordered engravings have led many to speculate the meaning behind these marks, including interpretations like mathematical significance or astrological relevance. It is thought by some to be a tally stick, as it features a series of what has been interpreted as tally marks carved in three columns running the length of the tool, though it has also been suggested that the scratches might have been to create a better grip on the handle or for some other non-mathematical reason. Others argue that the marks on the object are non-random and that it was likely a kind of counting tool and used to perform simple mathematical procedures.

Other speculations include the engravings on the bone serving as a lunar calendar. Dating to 20,000 years before present, it is regarded as the oldest mathematical tool to humankind, with the possible exception of the approximately 40,000-year-old Lebombo bone from southern Africa.

Alexander Marshack, an archaeologist from Harvard University, speculated that the Ishango bone represents numeric notation of a six-month lunar calendar after conducting a “detailed microscopic examination” of the bone. This idea arose from the fact that the markings on the first two rows adds up to 60, corresponding with two lunar months, and the sum of the number of carvings on the last row being 48, or a month and a half. Marshack generated a diagram comparing the different sizes and phases of the Moon with the notches of the Ishango bone.

There is some circumstantial evidence to support this alternate hypothesis, being that present day African societies utilize bones, strings, and other devices as calendars. However, critics in the field of archaeology have concluded that Marshack’s interpretation is flawed, describing that his analysis of the Ishango bone confines itself to a simple search for a pattern, rather than an actual test of his hypothesis.

This has also led Claudia Zaslavsky to suggest that the creator of the tool may have been a woman, tracking the lunar phase in relation to the menstrual cycle.

The Sumerians were an ancient civilization that lived in the southern part of Mesopotamia, which is now modern-day Iraq and Syria. Their civilization flourished from around 4100–1750 BCE, and they are considered to be the creators of civilization, as we know it today.

The Sumerians were among the first astronomers, mapping the stars into sets of constellations, many of which survived in the zodiac and were also recognised by the ancient Greeks. They were also aware of the five planets that are visible to the naked eye.

During the 8th and 7th centuries BC, Babylonian astronomers developed a new empirical approach to astronomy. They began studying and recording their belief system and philosophies dealing with an ideal nature of the universe and began employing an internal logic within their predictive planetary systems. This was an important contribution to astronomy and the philosophy of science, and some modern scholars have thus referred to this approach as a scientific revolution. This approach to astronomy was adopted and further developed in Greek and Hellenistic astrology.

Classical Greek and Latin sources frequently use the term Chaldeans for the philosophers, who were considered as priest-scribes specializing in astronomical and other forms of divination. Babylonian astronomy paved the way for modern astrology and is responsible for its spread across the Graeco-Roman empire during the 2nd Century, Hellenistic Period. The Babylonians used the sexagesimal system to trace the planets transits, by dividing the 360 degree sky into 30 degrees; they assigned 12 zodiacal signs to the stars along the ecliptic.

Only fragments of Babylonian astronomy have survived, consisting largely of contemporary clay tablets containing astronomical diaries, ephemerides and procedure texts, hence current knowledge of Babylonian planetary theory is in a fragmentary state. Nevertheless, the surviving fragments show that Babylonian astronomy was the first “successful attempt at giving a refined mathematical description of astronomical phenomena” and that “all subsequent varieties of scientific astronomy, in the Hellenistic world, in India, in Islam, and in the West … depend upon Babylonian astronomy in decisive and fundamental ways.”

An object labelled the ivory prism was recovered from the ruins of Nineveh. First presumed to be describing rules to a game, its use was later deciphered to be a unit converter for calculating the movement of celestial bodies and constellations.

Babylonian astronomers developed zodiacal signs. They are made up of the division of the sky into three sets of thirty degrees and the constellations that inhabit each sector.

The MUL.APIN contains catalogues of stars and constellations as well as schemes for predicting heliacal risings and settings of the planets, and lengths of daylight as measured by a water clock, gnomon, shadows, and intercalations. The Babylonian GU text arranges stars in ‘strings’ that lie along declination circles and thus measure right-ascensions or time intervals, and also employs the stars of the zenith, which are also separated by given right-ascensional differences.

The Babylonians were the first civilization known to possess a functional theory of the planets. The oldest surviving planetary astronomical text is the Babylonian Venus tablet of Ammisaduqa, a 7th-century BC copy of a list of observations of the motions of the planet Venus that probably dates as early as the second millennium BC.

The Babylonian astrologers also laid the foundations of what would eventually become Western astrology. The Enuma anu enlil, written during the Neo-Assyrian period in the 7th century BC, comprises a list of omens and their relationships with various celestial phenomena including the motions of the planets.

MUL.APIN is a collection of two cuneiform tablets (Tablet 1 and Tablet 2) that document aspects of Babylonian astronomy such as the movement of celestial bodies and records of solstices and eclipses. Each tablet is also split into smaller sections called Lists. It was comprised in the general time frame of the astrolabes and Enuma Anu Enlil, evidenced by similar themes, mathematical principles, and occurrences.

Tablet 1 houses information that closely parallels information contained in astrolabe B. The similarities between Tablet 1 and astrolabe B show that the authors were inspired by the same source for at least some of the information. There are six lists of stars on this tablet that relate to sixty constellations in charted paths of the three groups of Babylonian star paths, Ea, Anu, and Enlil. There are also additions to the paths of both Anu and Enlil that are not found in astrolabe B.

Egyptian astronomy started in prehistoric times, in the Predynastic Period. In the 5th millennium BCE, the stone circles at Nabta Playa may have made use of astronomical alignments. By the time the historical Dynastic Period began in the 3rd millennium BCE, the 365 day period of the Egyptian calendar was already in use, and the observation of stars was important in determining the annual flooding of the Nile.

The Egyptian pyramids were carefully aligned towards the pole star, and the temple of Amun-Re at Karnak was aligned on the rising of the midwinter Sun. Astronomy played a considerable part in fixing the dates of religious festivals and determining the hours of night, and temple astrologers were especially adept at watching the stars and observing the conjunctions and risings of the Sun, Moon, and planets, as well as the lunar phases.

In Ptolemaic Egypt, the Egyptian tradition merged with Greek astronomy and Babylonian astronomy, with the city of Alexandria in Lower Egypt becoming the centre of scientific activity across the Hellenistic world.

Roman Egypt produced the greatest astronomer of the era, Ptolemy (90–168 CE). His works on astronomy, including the Almagest, became the most influential books in the history of Western astronomy.

Following the Muslim conquest of Egypt, the region came to be dominated by Arabic culture and Islamic astronomy.

The astronomer Ibn Yunus (c. 950–1009) observed the Sun’s position for many years using a large astrolabe, and his observations on eclipses were still used centuries later. In 1006, Ali ibn Ridwan observed the SN 1006, a supernova regarded as the brightest stellar event in recorded history, and left the most detailed description of it. In the 14th century, Najm al-Din al-Misri wrote a treatise describing over 100 different types of scientific and astronomical instruments, many of which he invented himself.

Greek astronomy was heavily influenced by Babylonian astronomy and, to a lesser extent, Egyptian astronomy. In later periods, ancient Greek astronomical works were translated and promulgated in other languages, most notably in Arabic by the astronomers and mathematicians within the various Arab-Muslim empires of the Middle Ages.

Many Greek astronomical texts are known only by name, and perhaps by a description or quotations. Some elementary works have survived because they were largely non-mathematical and suitable for use in schools. Books in this class include the Phaenomena of Euclid and two works by Autolycus of Pitane. Three important textbooks, written shortly before Ptolemy’s time, were written by Cleomedes, Geminus, and Theon of Smyrna.

Books by Roman authors like Pliny the Elder and Vitruvius contain some information on Greek astronomy. The most important primary source is the Almagest, since Ptolemy refers to the work of many of his predecessors.

The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts of Oriental Orthodoxy as well as by the Amazigh people (also known as the Berbers).

The Julian calendar was proposed in 46 BC by (and takes its name from) Julius Caesar, as a reform of the earlier Roman calendar, which was largely a lunisolar one. It took effect on 1st January 45 BC, by his edict. Caesar’s calendar became the predominant calendar in the Roman Empire and subsequently most of the Western world for more than 1,600 years, until 1582 when Pope Gregory XIII promulgated a revised calendar.

The Julian calendar has two types of years: a normal year of 365 days and a leap year of 366 days. They follow a simple cycle of three normal years and one leap year, giving an average year that is 365.25 days long. That is more than the actual solar year value of approximately 365.2422 days (the current value, which varies), which means the Julian calendar gains one day every 129 years. In other words, the Julian calendar gains 3.1 days every 400 years.

Medieval Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (9th–13th centuries), and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and later in the Far East and India. It closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science with Islamic characteristics. These included Greek, Sassanid, and Indian works in particular, which were translated and built upon.

Islamic astronomy played a significant role in the revival of ancient astronomy following the loss of knowledge during the early medieval period, notably with the production of Latin translations of Arabic works during the 12th century. Islamic astronomy also had an influence on Chinese astronomy.

A significant number of stars in the sky, such as Aldebaran, Altair and Deneb, and astronomical terms such as alidade, azimuth, and nadir, are still referred to by their Arabic names. A large corpus of literature from Islamic astronomy remains today, numbering approximately 10,000 manuscripts scattered throughout the world, many of which have not been read or catalogued. Even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed.

The House of Wisdom was an academy established in Baghdad under Abbasid caliph Al-Ma’mun in the early 9th century. Astronomical research was greatly supported by al-Mamun through the House of Wisdom.
The first major Muslim work of astronomy was Zij al-Sindhind, produced by the mathematician Muhammad ibn Musa al-Khwarizmi in 830.

It contained tables for the movements of the Sun, the Moon, and the planets Mercury, Venus, Mars, Jupiter and Saturn. The work introduced Ptolemaic concepts into Islamic science, and marked a turning point in Islamic astronomy, which had previously concentrated on translating works, but which now began to develop new ideas.

Several works of Islamic astronomy were translated to Latin starting from the 12th century.
The work of al-Battani, Kitāb az-Zīj (“Book of Astronomical Tables”), was frequently cited by European astronomers and received several reprints, including one with annotations by Regiomontanus.

Nicolaus Copernicus, in his book that initiated the Copernican Revolution, the De revolutionibus orbium coelestium, mentioned al-Battani no fewer than 23 times, and also mentions him in the Commentariolus. Tycho Brahe, Giovanni Battista Riccioli, Johannes Kepler, Galileo Galilei, and others frequently cited him or his observations. His data is still used in geophysics.

Around 1190, al-Bitruji published an alternative geocentric system to Ptolemy’s model. His system spread through most of Europe during the 13th century, with debates and refutations of his ideas continued to the 16th century.

In 1217, Michael Scot finished a Latin translation of al-Bitruji’s Book of Cosmology (Kitāb al-Hayʾah), which became a valid alternative to Ptolemys Almagest in scholasticist circles. Several European writers, including Albertus Magnus and Roger Bacon, explained it in detail and compared it with Ptolemy’s. Copernicus cited his system in the De revolutionibus while discussing theories of the order of the inferior planets.

Some historians maintain that the thought of the Maragheh observatory, in particular the mathematical devices known as the Urdi lemma and the Tusi couple, influenced Renaissance-era European astronomy and thus Copernicus. Copernicus used such devices in the same planetary models as found in Arabic sources. Furthermore, the exact replacement of the equant by two epicycles used by Copernicus in the Commentariolus was found in an earlier work by Ibn al-Shatir of Damascus.

Copernicus’ lunar and Mercury models are also identical to Ibn al-Shatir’s.

While the influence of the criticism of Ptolemy by Averroes on Renaissance thought is clear and explicit, the claim of direct influence of the Maragha school, postulated by Otto E. Neugebauer in 1957, remains an open question. Since the Tusi couple was used by Copernicus in his reformulation of mathematical astronomy, there is a growing consensus that he became aware of this idea in some way.

It has been suggested that the idea of the Tusi couple may have arrived in Europe leaving few manuscript traces, since it could have occurred without the translation of any Arabic text into Latin. One possible route of transmission may have been through Byzantine science, which translated some of al-Tusi’s works from Arabic into Byzantine Greek.

Several Byzantine Greek manuscripts containing the Tusi-couple are still extant in Italy. Other scholars have argued that Copernicus could well have developed these ideas independently of the late Islamic tradition. Copernicus explicitly references several astronomers of the “Islamic Golden Age” (10th to 12th centuries) in De Revolutionibus: Albategnius (Al-Battani), Averroes (Ibn Rushd), Thebit (Thābit ibn Qurra), Arzachel (Al-Zarqali), and Alpetragius (Al-Bitruji), but he does not show awareness of the existence of any of the later astronomers of the Maragha school.

Nicolaus Copernicus (19th February 1473 to 24th May 1543) was a Renaissance polymath, active as a mathematician, astronomer, and Catholic canon, who formulated a model of the universe that placed the Sun rather than Earth at its centre. In all likelihood, Copernicus developed his model independently of Aristarchus of Samos, an ancient Greek astronomer who had formulated such a model some eighteen centuries earlier.

The publication of Copernicus’s model in his book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), just before his death in 1543, was a major event in the history of science, triggering the Copernican Revolution and making a pioneering contribution to the Scientific Revolution.

The Copernican Revolution was the paradigm shift from the Ptolemaic model of the heavens, which described the cosmos as having Earth stationary at the centre of the universe, to the heliocentric model with the Sun at the centre of the Solar System.

This revolution consisted of two phases; the first being extremely mathematical in nature and the second phase starting in 1610 with the publication of a pamphlet by Galileo. Beginning with the 1543 publication of Nicolaus Copernicus’s De revolutionibus orbium coelestium, contributions to the “revolution” continued until finally ending with Isaac Newton’s work over a century later.

The earliest existing record of a telescope was a 1608 patent submitted to the government in the Netherlands by Middelburg spectacle maker Hans Lipperhey for a refracting telescope. The actual inventor is unknown but word of it spread through Europe. Galileo heard about it and, in 1609, built his own version, and made his telescopic observations of celestial objects.

The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors (reduction of spherical aberration and no chromatic aberration) led to many proposed designs and several attempts to build reflecting telescopes.

In 1668, Isaac Newton built the first practical reflecting telescope, of a design, which now bears his name, the Newtonian reflector.

The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose-built radio telescope went into operation in 1937. Since then, a large variety of complex astronomical instruments have been developed.

The Reber Radio Telescope is a historic radio telescope, located at the Green Bank Observatory near Green Bank, West Virginia, United States. Built in 1937 in Illinois by the astronomer Grote Reber, it was the first purpose-built parabolic radio telescope. It was designated a National Historic Landmark in 1989.

The telescope was built by Reber in his back yard in Wheaton, Illinois, in 1937, following up on the research of Karl Jansky, the discoverer in 1933 of radio waves emanating from the Milky Way. It was the second radio telescope ever built (after Jansky’s dipole array), and the first parabolic radio telescope, serving as a prototype for the first large dish radio telescopes such as the Green Bank Telescope and Lovell Telescope constructed after World War II.

Reber was the world’s only radio astronomer at the time and his construction of the telescope, and the sky surveys he did with it, helped to found the field of radio astronomy, revealing radio sources such as Cassiopeia A and Cygnus X-1 for the first time.

A space telescope (also known as space observatory) is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launched in 1968, and the Soviet Orion 1 ultraviolet telescope aboard space station Salyut 1 in 1971.

Space telescopes avoid several problems caused by the atmosphere, including the absorption or scattering of certain wavelengths of light, obstruction by clouds, and distortions due to atmospheric refraction such as twinkling. Space telescopes can also observe dim objects during the daytime, and they avoid light pollution, which ground-based observatories encounter.

They are divided into two types: Satellites, which map the entire sky (astronomical survey), and satellites, which focus on selected astronomical objects or parts of the sky and beyond. Space telescopes are distinct from Earth imaging satellites, which point toward Earth for satellite imaging, applied for weather analysis, espionage, and other types of information gathering.

Space-based astronomy is more important for frequency ranges that are outside the optical window and the radio window, the only two wavelength ranges of the electromagnetic spectrum that are not severely attenuated by the atmosphere. For example, X-ray astronomy is nearly impossible when done from Earth, and has reached its current importance in astronomy only due to orbiting X-ray telescopes such as the Chandra X-ray Observatory and the XMM-Newton observatory. Infrared and ultraviolet are also largely blocked.

The Square Kilometre Array (SKA) is an intergovernmental international radio telescope project being built in Australia (low-frequency) and South Africa (mid-frequency). The combining infrastructure, the Square Kilometre Array Observatory (SKAO), and headquarters, are located at the Jodrell Bank Observatory in the United Kingdom. The SKA cores are being built in the southern hemisphere, where the view of the Milky Way galaxy is the best and radio interference is at its least.

Conceived in the 1990s, and further developed and designed by the late-2010s, when completed sometime in the 2030s it will have a total collecting area of approximately one square kilometre. It will operate over a wide range of frequencies and its size will make it 50 times more sensitive than any other radio instrument.

If built as planned, it should be able to survey the sky more than ten thousand times faster than before. With receiving stations extending out to a distance of at least 3,000 km (1,900 mi) from a concentrated central core, it will exploit radio astronomy’s ability to provide the highest-resolution images in all astronomy.

The SKA was estimated to cost €1.8 billion in 2014, including €650 million for Phase 1, which represented about 10% of the planned capability of the entire telescope array. There have been numerous delays and rising costs over the nearly 30-year history of the intergovernmental project.

As of December 2022, the whole project was reported to be worth around an estimated $3 billion.

And that was where Dr Lees finished his presentation and left the society members present still pondering the question ‘Why do we stargaze’. There followed a detailed question and answer debate with Dr Lees.