Julieta EYNATYAN

The periods of science formation reflect the historical unity if different people and different cultures, which was possible due to regular relations existing between them. It is known that ancient Greece inherited traditions of the oldest centers of scientific evolution, i.e. Babylonia, Egypt and India, as favorable conditions were created for it in this country.

In science, more than in any other sphere of human history, investigation of the past is necessary for a better understanding of the present and the possibility to direct nature rules in the future. The nucleus of scientific thought history is the connection of mathematics with astronomy, which never stopped during several millenniums, beginning with the foundation of the first cities. Observations were accumulated and methods were perfected one after another.

As any other ancient people, Armenians observed movements of celestial bodies from time immemorial. Pictures of stars, constellations, planets, as well as the Sun and the Moon, done on rocks during several millenniums B.C., give evidence about great interest towards astronomy on the Armenian Plateau. According to the opinion of some specialists, fragments of rock with astronomical sculptures dating back to the 3^rd millennium, found in the oldest site of Metzamor fortress, served to observe celestial bodies and phenomena.

Devastating wars and natural catastrophes destroyed many valuable scientific works created by the Armenian people, and only fragments of tools, parts of maps or petrified manuscripts found in mountain caves have reached our days. Belts with inscriptions concerning astronomy and calendar theory, things of domestic use with decor representing stars and constellations signs, inscriptions about eclipses and astronomical rock pictures have been found.

Solar clocks exist until now on the walls of numerous Armenians monasteries and churches. Their descriptions can also be found in the manuscripts kept at the Mashtots Matenadaran in Yerevan. The dial plate of these clocks is perpendicular to the horizon and stretches from East to West. They are engraved on the Southern wall of the buildings. Shadow-measurers were also used in Armenia to measure time. Those were tables showing differences in shadow length during the days of the year. Letters of Armenian alphabet replaced figures on solar clocks, as well as on shadow-measurers. The first nine letters meant single unit, the second nine meant tens and so on. The hour numeration began from morning and reached six by noon. Picture 1 shows the solar clock engraved on the wall of the Zvartnots Cathedral (7^th century A.D) in about 15 km from Yerevan.

Shadow-measurers are based on the principle that shadows of vertical things have different length at different hours of the day. As the length of the day is also changing during different seasons of the year, which is the result of the Sun altitude changing, the shadows length depends on the season as well. The shadow of a thing will be shorter at the same hour in summer (minimal dimension occurs on the day of summer solstice) than in winter (maximal dimension occurs on the day of winter solstice). Picture 2 shows the shadow-measurer painted on folio 58r of the Matenadaran manuscript no. 2001.

Astrolabes, the most frequently used astronomical and geodesic instruments of the Middle Ages, were known in Armenia. Their descriptions and the way of using them can be met in numerous manuscripts of the Matenadaran. A fragment of an astrolabe of the 10^th century is kept at the Echmiadzin Museum. The History Museum of Oxford keeps two Arabic astrolabes of the 9^th-10^th centuries, on which Armenian inscriptions can be seen. Astrolabes were used to solve astronomical problems (planets and stars altitudes above the horizon, Sun rising and setting moments and so on), as well as everyday practical issues (remoteness of objects, their altitude, rivers wideness and so on). Picture 3 shows the astrolabe made by Ghukas Vanandetsi in the 17^th century, now kept at the Burakan Observatory.

In Armenian manuscripts, there is information about the Sun and the Moon eclipses, as well as observations of novae and supernovae. As an example, we can bring the mentioning of a nova, as bright as fire, observed in the beginning of the 11^th century (1006). B. Toumanian, a famous Armenian astronomy historian, while studying manuscripts comes to the conclusion that our sources are talking about the supernova explosion, which took place in 1006 and was seen with the naked eye. He mentions that the same explosion was described in Chinese and Japanese sources. Toumanian writes: “The description of this fact in Armenian authors’ works is the third evidence of it in the world and has great significance for modern astrophysics in the studying of supernovae essence and explosion rule”.

It is well known that results of ancient Greek scientists’ investigations are summarized in the Almagest of C. Ptolemy (2^nd century B.C.). According to his geocentric system, the Earth was placed in the center of the Universe and the Moon, Mercury, Venus revolved round it by concentric circles. The Christian Church supported such a special position and importance given to the Earth by this theory. In 1543, in his work On the Revolution of Celestial Bodies (De revolutionibus orbium coelestium), famous Polish scientist Copernicus rejected this theory, which was dominating during a whole millennium. He proposed and proved the theory of heliocentric system, which was not admitted for a long time by the Christian Church ministers.

During these centuries Armenia was under foreign domination and the Church did everything to keep people away from new scientific revolution and its consequences. In 1695, in Amsterdam Vanandians published the first Armenian big format map called Universal Geographic Map. This map represents the Western and Eastern hemispheres, as well as pictures of constellations on the starry sky, and the Universe geocentric system.

The Dictionary of Armenian Language published in 1749 contains two maps presenting the cosmic system proposed by the famous Danish astronomer Tycho-Brahe. According to him planets were revolving round the Sun and the Sun round the Earth. Echoes of Copernicus theory reached Armenia only centuries later. The manuscript work On Geography by Yeghia Karnetsi describes the heliocentric system and mentions that there is no reason to deny this theory. The first Armenian printed book openly speaking about the heliocentric system is the Little Book called Principle of Natural Sciences by S. Abkarian published in 1796 in Rome.

Progressive Armenian thinkers of the 19^th century joined their efforts to translate into modern Armenian the best achievements of world science and to spread them among the people. Articles, manuals and investigations published in Armenian in the 19^th century unanimously adopted the heliocentric system.

As to Armenian manuscripts, they are richer in texts dedicated to the theory of calendar. It is indisputable that history is measured by time. A fact is considered a historical one if it is given not only in the space, but also in the time. In this scope, the time is a supportive link for history, which serves to precise the chronological remoteness of the fact from us. Nevertheless, time units, i.e. day, month and year are not proportional and one can hardly find a quantity of years expressed by an entire figure containing months and days expressed by entire figures. This circumstance explains the difficulty of time measuring and the variety of calendar systems used by different nations during millenniums. To overcome these difficulties and to make the three mentioned magnitudes to concord was the reason that three types of calendar, i.e. lunar, lunar-solar and solar, were created by different nations. Lunar calendars are based on the lunar month, which consists of 29.5 days. In lunar calendars the year has twelve months, each having 29 or 30 days. The beginning of each month is new Moon, the middle of the month is full Moon and the end of the month is ending Moon. In fact, the date is showing the age of the Moon phase. That is the advantage of the lunar calendar in comparison with the solar one.

Almost all nations used lunar calendar in ancient times. In most languages, the words month and Moon are homonyms. The beginning of the month, i.e. the first appearance of the Moon in the East, was announced in many places by observers, but in different seasons the observation results were not the same and sometimes they were false. So the months were successively considered to have 29 or 30 days.

Nevertheless, the lunar month was not very convenient to measure time, as the rhythm of human life is more connected with the Sun than with the Moon, and it was necessary to find a way to coordinate the revolving of these celestial bodies. The issue was complicated by the fact that lunar months do not divide the year into equal parts. The difference between 12 lunar months and a solar year is almost 11 days, and 13 lunar months are longer than a solar year for about 18 days. It made no difference for farmers how many lunar months separated one harvesting from another, but for collecting taxes the State authorities had to know precisely the year length, as taxes were to be collected at the same time everywhere in the country.

That was the reason for adding from time to time supplementary lunar months, approximately one month each three years. Authorities added this month without any precise order. The numeral ratio between lunar month and solar year length was known from the 7^th century B.C. and in the 7^th-4^th centuries B.C. supplementary months were already added regularly, hypothetically 3 months during 8 years. So, such calendars were called lunar-solar and they were more complicated than others, as the Sun movement and the Moon phases had to be coordinated.

Practical difficulties connected with the coordination of lunar and solar calendars, which exist up till now when calculating the Easter date, were the basis of mathematical and astronomical knowledge development. Calculations made with the lunar 19-year period are more convenient for Church practice, as 235 lunar months are equal to 19 solar years with a few hours difference. During 19 years supplementary “embolismic” months were added for 7 times. The 19-year calculations were also done by additions, as the lunar year was shorter than the solar one for 11 days. So adding 11 to the age of the Moon at the beginning of each year, one can obtain the age of the Moon of that year. If it overpasses 30, one must take away 30. In this case, to be more precise 12 was added instead of 11 at the end of the last year of the 19-year period. It is known that Babylonians, Chinese, Indians used this cycle at different times, but it became known to the science due to Greek scholar Meton (5^th century B.C.). This lunar-solar periodical cycle was convenient to calculate religious feast dates and was used by Christian nations, as well as by Armenians. These permanent tables, in which days of the Moon rising and setting were noted for 19 years, were used nearly for a whole millennium. Nevertheless, this lunar-solar system did not keep away most of the nations (Egyptians, Romans, Persians, Armenians) from using solar calendars as well.

Historians of calendar and practical astronomy highly appreciate particularly the Egyptian solar calendar, stating “that it was the only smart calendar in human history”. The Egyptian year, which had always the same length without corrections, was very convenient for astronomical calculations. The Babylonian lunar calendar and the Greek one, which was full of mistakes, were corrected not only for coordination with the Sun and the Moon revolving, but also to accord with local habits and even policy. They were much more inconvenient than the Egyptian year, which remained without changes during centuries and had always the same length.

For instance, calculating the difference in days between the year beginnings for a 50-year period in the system of Babylonian or Greek calendar was a serious problem, meanwhile in the Egyptian one, this interval was 365x50. It is but normal that in the Middle Ages this calendar was widely used to solve astronomical problems, up to Copernicus who used it in his Moon or planets tables.

Deviation of the Egyptian calendar from the Sun movement during a human life was not very noticeable, making only 10 days in 40 years. “It was for this reason, that the schematic year of 12x30+5 became the official system of time measuring in Sassanid Iran, as well as in Armenia and Cappadocia”, writes E.J. Bickerman.

Nevertheless, people having adopted Christianity had to choose a stabile calendar to calculate religious feasts. In this scope the most convenient was the Julian one. In the Western part of the Byzantine Empire it was adopted without any changes, but in the Eastern part, where the official language was Greek, it was adapted to the local habits. They were based on the “Alexandrian” year, which was identical to the Egyptian one. Simply, each four years a day was added to the scheme 12 x 30 + 5 days. Among neighboring calendar systems the Zoroastrian one had also permanently 365 days. Here the difference between solar and calendar years was corrected once in 120 years by adding a whole month. By the way, the viewpoint according to which Egyptian calendar was the prototype of the Zoroastrian one is not the only one. Investigations of the last years brought to another conclusion, i.e. calendar systems of 12x30+5 days were used by different nations and even the Zoroastrian calendar can be considered as an improvement of the Indo-European heritage.

The Armenian calendar was also a solar one, and the year had a permanent length: 365 days. Although Christian nations used the Julian calendar already for a long time, Armenians continued using their ancient mobile calendar for centuries.

It is known that discussions among Monophysites and Dyophysites were violent in the 5^th century and they played an important role in the history of Armenian culture and particularly calendar. As a result of these dogmatic discussions and the creation of Armenian alphabet, Armenians did everything to escape any foreign influence or impulse. In the middle of the 6^th century the Armenian Church separated from the Chalcedonians, and if until that time the Church languages were Greek and Syriac and the Church feasts were calculated with the same calendar, from the middle of the 6^th  century, i.e. from July 11, 552, the major Armenian era began and feasts were calculated according to Armenian mobile calendar, which was already used by the people. According to Armenian manuscripts, in 552 Andreas, a calendar theorist finished establishing 200 years Easter lists, which were used by all Christian nations. According to this information, during 9 years after the lists were ready, everybody confused calculations of Easter until the astronomers council of Alexandria, headed by Eas of Alexandria, discovered the 532-year cycle of Easter, which takes into account the 19-year cycle of the Moon, as well as the 28 (4x7)-year cycle of the Sun. Manuscripts connect the Armenian major era foundation with the beginning of this period.

The fact that Armenian calendar was mobile and the necessity of elucidating numerous issues of Church discussions compelled Armenians to translate, write and comment many works devoted to the calendar theory, the main part of which is preserved in Armenian manuscripts up till now. Courses of calendar theory were delivered in monastic universities and students were taught to calculate by Armenian calendar, as well as by those of other people.

The most ancient written evidence about Armenian calendar is preserved in Movses Khorenatsi’s History. According to this author king Artashes (2^nd century B.C.) paid special attention to several sciences development and, among them, the calendar theory. The tradition connects the beginning of Armenian era with the victory of patriarch Hayk against Bel, and the names of Armenian months with the names of his sons and daughters, which were Navasard, Hori, Sahmi, Tre, Kaghots, Arats, Meheki, Areg, Aheki, Mareri, Margats, Hrortits. It must be mentioned that all these 12 months had 30 days and the supplementary month Aveliats of 5 days was added to them.

Taking the cyclical period of 1460 years as a basis of his calculations, prominent armenologist of the 19^th century L. Alishan tried to elucidate the beginning of the Armenian era and found 2492, but this attempt to give a scientific argumentation to old traditions was not accepted by later researchers. That is why historians of calendar base their investigations exclusively on data given in manuscripts. According to the most of them the Armenian era began from the middle of the first millennium B.C., and the months names have mainly Persian origin.

After the adoption of Christianity and up to the 7^th century, the Armenian Church used calculations of other Churches (200-year Easter list of Andreas or 532-year list of Eas of Alexandria) to establish feast dates, meanwhile people used for their daily life the Armenian mobile calendar. From the middle of the 7^th century, when Persia annexed one part of Armenia and Byzantium another, the new religion of Islam began to represent a real danger. As Persia was inclined towards this religion, Armenians had nothing to do but to “seek protection near Greeks”. Historians give evidence that in the middle of the 7^th century, the Armenian Catholicos, worried by this situation, entrusted prominent Armenian philosopher and mathematician Anania Shirakatsi to change Armenian mobile calendar such as the Church should not have to seek the help of any other calendar. Shirakatsi realized the aim and changed the Armenian calendar according to the needs of the Church, going without errors to the Julian one, but in the same time remaining independent and close to national traditions. Alongside with the Armenian calendar, Shirakatsi gave the coordination of Roman, Hebrew, Assyrian, Greek and other calendars. Finding correspondence of the Armenian calendar calculations with anyone of them, one can find also the others.

Nevertheless, according to the sources, the calendar system created by Shirakatsi was not used because of the Catholicos death and the fact that no Church special decision was taken about it. Only several centuries after Shirakatsi, his works were fragmentarily copied in different collections of works, being shortened and reduced. Researchers think that it was in the 11^th century that famous thinker Grigor Magistros asked the Catholicos not to disregard the works of Shirakatsi, as he used the scientific heritage of different ancient people, collecting, correcting and writing them down for the Armenian people.

It is well known that after the adoption of Christianity the antique science was partly forgotten, but this situation could not last long. Gradually Church fathers started to use such theses of antique science, which could serve purposes of their ideology. It should be mentioned that works of Greek thinkers were known in Armenia as early as the 5^th century and were partly translated into Armenian. In this scope, Eznik Koghbatsi, Yeghishe and David the Invincible are worth special mentioning among Armenian thinkers, as their works were of naturalistic philosophical character. Natural sciences were founded in Armenia as early as in the 7^th century due to Anania Shirakatsi. Summarizing the works of his predecessors, he completed them with those of Greek thinkers and his own observations, in which he combined scientific and biblical theses, and put them all down. He rejected superstitions and astrology, and though his astronomical system was a geocentric one, he knew that the Earth has the form of a globe and does not lie on anything. He believed that antipodes exist, that the Milky Way consists of a multitude of weakly shining stars and that the Moon has not its own light. The mathematics manual written by Shirakatsi is one of the most ancient in the world.

In the 7^th century, Anania Shirakatsi could use the systems created by other nations (for instance, the Alexandrian year), adding each four years an Aveliats month of 6 days instead of 5, and changing nor the Armenian months names neither the solar nature of the year, preserving thus the national independence of the calendar. Nevertheless, this 7^th century great thinker went a different way. He left untouched the Zodiac year which came from the depth of centuries and precisely measured time with the scheme of 12x30+5, being up till now highly appreciated by historians of astronomy. To calculate Church feasts, he connected the calculation of leap year not with the Sun, but with the Moon, and reduced the Moon addition by 1 each fourth year. Due to this the Armenian Church year moved alongside with other people calendars, but remained independent and unchanged. Not adding the leap year day to the year days resulted in the change of the year beginning or, to express it differently the leap year days were accumulated separately. Date calculation definitions were based exactly on this rule. One of these definitions dealt with the Theophany of Christ, i.e. January 6, and the other one with the day of vernal equinox, i.e. March 20. In order to define any Armenian date, we must determine how much the Theophany or the vernal equinox days had moved from the beginning of the major Armenian era, as a result of neglecting the leap days, then multiply the quantity of these days by 4, taking into account in which year of the leap we are, and we will get the Armenian date. In fact, combining the mobile character of the Armenian calendar with the leap calculation, we get the Armenian date. This canon could be used until the missing days would not make a whole year (which occurs once in a cycle of 1460 years). Not disturbing the Church feats calculation, this system brought to a break between Armenian and Roman dates.

This difference was corrected and commented in the 11^th century by famous Armenian philosopher and calendar theorist Hovhannes Sarkavag Yerzynkatsi. Omitting the supplementary year from the calculations, he restored the two dates concordance. Besides, he set up a new calendar system for the needs of the Church. In that system the year began with August 11 and each four years a leap day was added. The collections called Synaxary were compiled according to this system. That was also the beginning of the Armenian minor era, which began in 1085, and was based on the same principle, i.e. the changing of the Theophany and vernal equinox days each fourth year. Hovhannes Sarkavag enriched and wrote anew some parts of the Chapters of the Calendar Theory in which Shirakatsi’s system remained basic, and major and minor Armenian eras were calculated on its principles.

Investigators of Armenian medieval manuscripts devoted to the theory of calendar noticed that among them there is an anonymous work entitled Chapters of the Calendar Theory. This work presents in separate parts the theory of Armenian, as well as Roman, Greek, Assyrian, Hebrew, old Arabic, Ethiopian, Egyptian, Athenian, Cappadocian, Buthanian, Caucasian Albanian, Georgian and Persian calendars. It must be mentioned that, after the Armenian calendar, the author pays the greatest attention to the Roman and Hebrew ones. Short and long copies of this work exist in more than 90 manuscripts of the Yerevan Matenadaran. Its most ancient copies date back to the 13^th-14^th centuries and the most recent ones to the 18^th-19^th centuries.

Investigation of manuscripts brings to the conclusion that Armenian calendar system existed for centuries long. The work Chapters of the Calendar Theory remained a starting point for later calendar theorists and commentaries written on it allowed to summarize all the knowledge about calendar theory in medieval cultural centers. At the beginning of the 15^th century, Hacob Ghrimetsi, another prominent theorist of the calendar, brought to order the manual Chapters of the Calendar Theory, enriched it with new subjects and cleared away numerous mistakes accumulated in it. It seemed absurd to go on calculating with the Armenian mobile calendar at the beginning of the 15^th century, when the Julian calendar was used everywhere and the immobile Church year reformed by Hovhannes Sarkavag already existed, but it was dictated by the political and religious situation of the time. The Church was in great danger because of the Uniats, who tried to spread Western scholastic ideas in Armenia, neglecting Armenian rites, habits and literature. This antipatriotic activity was met by a strong reaction headed by Hovhan Vorotnetsi and Grigor Tathevatsi who demanded from their disciples to be not only studious, but first of all eager to keep pure the Armenian language, literature and Church traditions. In this anti-Uniat struggle the calendar issue was also of certain importance.

Besides rich knowledge about the calendar theory, the work Chapters of the Calendar Theory contains the summary of medieval practical data in astronomy. Some of the definitions begin with the following sentences: “If you want to know in which Zodiac sign the Sun is…”, “If you want to know in which zone the Sun is…”, “If you want to know in which Zodiac sign the Moon is…” and so on. From this viewpoint the Chapters remind of Zigs (in Arabic this word means Tables), which are of special importance in the history of Arabic astronomy. This work, enriched with numerous tables, contains vast information about other people calendars and the canons of coordinating them with each other, as well as methods of solving practical astronomic concrete problems. It is well known that the Zigs were mostly composed under the immediate influence of the Ptolemy’s Almagest. For instance, we can mention a text, which occurs in Zigs and Chapters, as well as in the Almagest. It speaks of connections existing between celestial bodies, parts of human body and nations. Here the Zodiac constellation of Aries corresponds to Persia and the human head; the Cancer constellation corresponds to Armenia and human chest; the Pisces constellation corresponds to India and human feet, and so on. In some manuscripts one can also find pictures devoted to this.

The work Chapters of the Calendar Theory, containing the 2000-year old theoretical and practical Armenian and neighboring nations astronomy advice, as well as the summary of the times astronomic practical knowledge, was taught in the medieval universities during all the Middle Ages. It was corrected and commented up till the 18^th-19^th centuries.