Prehistoric astronomical activity is represented by a Stonehenge-like megalithic circle and "Observatory" at Rujm-el-Hiri, near Yonathan in the Golan, the Westernmost sector of the historical Bashan plateau dating from the IIIrd Millenium BC.

Star worship is mentioned in the Old Testament as being common among the Canaanites, but the Bashan inhabitants who built that Golan megalithic circle antedate the Canaanites. Very little is known about them and the presumably religous role of their edifice.

To the IIIth Century B.C. Israelitis, they appeared as the work of giants (Refa'im, also Anakim, Emim, Zuzim), and this is probably the source of the legends about races of giants that had lived in Eretz-Israel prior to the Israelite conquest including the characterization "a remnant of the giants" for Og, King of Bashan, in Deuteronomy and Joshua. Indeed, the Rujm-el-Hiri circle is just one among many megalithic remains in the Bashan, probably at the origin in Greece and England (the "Giant's Dance" = Stonehenge).


The Israelitis' abstract monotheism and their centering of intellectual creativity on ethical issues were detrimental to a natural development of observational science, as did happen in Sumeria or Greece. However, the requirements of agriculture induced a cycle of holidays that were incorporated in time into Judaism and were given Ethnical or National religious significance. There thus developed a need for an understanding of the recurrence of seasons and for a synchronized calendar fitted to Solar, Lunar and Sidereal time . Several of the Mishnaic scholars were versed in Astronomy, such as the "Tannaim" Yehoshua ben Zakkai, the Patriarch Gamliel II and in particular Yehoshua (=Joshua) ben Hananiah.

In the tractate Horayoth, dealing with errors of Justice, the following anecdote is related:

"Rabbi Gamliel and Rabbi Yehoshua went together on a voyage at sea. Rabbi Gamliel carried a supply of bread, Rabbi Yehoshua carried a similar amount of bread and in addition a reserve of flour. At sea, they used up the entire supply of bread and had to utilize Rabbi Yehoshua's flour reserve. Rabbi Gamliel then asked Rabbi Yehoshua - "Did you know that this trip would last longer than usual, when you decided to carry this flour reserve?" Rabbi Yehoshua answered - "There is a star that appears every 70 years and induces navigational errors. I thought it might appear and cause us to go astray." Rabbi Gamliel then exclaimed "You are so knowledgeable and you nevertheless have to travel to make a living?" Rabbi Yehoshua then answered bitterly - "How come you are so surprised? Don't you know that two of your own students Rabbi Eliezer Hisma and Rabbi Yehohanan ben Gudgada who are so smart that they can tell you how many drops there are in the ocean, have neither bread to eat nor clothes to wear?"

This observation is generally interpreted as relating to Halley's Comet, with a period aproximating 76 years. Observing a comet's periodicity, with such a long period, requires records covering many centuries; it is possible that the Mishnaic scholars did inherit such records from the Great Knesset scholars (before 300 BC) who received them during the Babylonian exile (586-537 BC) from the "Chaldeans" (i.e. from Sumer, Akad etc. going back to the IIIrd Millenium BC). Indeed, the Hebrew agricultural names of the months were replaced by Sumerian and Akadian names after the Babylonian captivity.

However, there is perhaps a difficulty with the dates: Rabbi Yehoshua was born in 35 AD and died in 117 AD. Rabbi Gamliel died in 115 AD. The only appearance of Halley's Comet in the interval 55-155 (when Yehoshua was older than 20), is in 66 AD.

Rabbi Gamliel was younger then Rabbi Yehoshua and it has been argued that if he was 20-25 years old, it is doubtful whether he could have had students at the time. Still, this is not a strong argument, as Rabbi Gamliel II was also the hereditary Patriarch, and may have had students attached to him formally from the moment he was appointed head of the Sanhedrin.

Philippe Veron has, however, come up recently with a different identification of Rabbi Yehoshua's star, and argues that this was the variable Mira Ceti.

Mar Samuel, who became around 220 AD the Dean of the Talmudic Academy of Nehardea in Babylonia, was an astronomer who could calculate and adjust the calendar with great precision, intercalating an extra month or reassigning the length of a month.

The prescriptions for the calendar adjustments were written down in a special Baraita. They include the 19 years synchronization cycle to this very day in the Jewish Calendar.


Science spreads by convection. When Khushru Anushirvan, Sassanid Emperor of Persia, signed a ten year truce with Justinian of Byzance, he ensured the continuity of science by requesting that the teachers of the recently abolished Academy of Athens be transferred to Persia. In his fanaticism, Justinian was then trying hard to put an end to Judaism at the same time eradicating Neo-Platonicism and what was left of Greek science. The Neo-Platonicists settled in Mesopotamia under Persian rule, and their school was already flourishing when Persia was conquered by Islam. Mathematics and Astronomy thrived (e.g. Omar Khayyam, whose Rubayat was just a hobby, his professional creativity having yielded methods for solving factorizable cubic equations etc.) and spread all over the new Mohammedon Empire.

The Jews were active participants, and the first Arabic-languate treatise on the Astrolabe was written by the Jew Joel, known as Masha-Allah of Basra (Iraq) around the year 800. This is the treatise that was translated into English by Geoffrey Chaucer ("The Treatise on the Astrolabe") around 1380, from a prior Latin translation. Masha-Allah also wrote a book on Lunar and Solar Eclipses, that was later translated into Hebrew by Abraham Ibn Ezra ("Sefer be kadrut ha levana ve ha shemesh")

Sind ben Ali, a heretic Jew, was the main contributor (~830) to the astronomical tables of the Caliph Maimum. The scene now shifts to Spain, where Abraham bar Hiyya Hanasi ("The Prince") of Barcelona (d. 1336) improved on these tables, using calculations performed by the Arab astronomer Al-Battani (d. 929). Abraham bar Hiyya was a prominent mathematician and astronomer, and wrote famous textboks in both fields. He introduced Europe to (Arab) trigonometry in his "Treatise on Mensuration and Calculations". The Hebrew was translated by Plast of Tivoli into Latin in 1145 and his book served as main source material for that later work of Leonardo Fibonacci of Pisa. In Astronomy, his book "The Shape of the Earth" is based upon the Ptolemaic system, contains a roughly correct estimate of the distance to the Moon (but the wrong distance to the Sun). The principles for Calender intercalation make up yet another book.

His student, Abraham Ibn Ezra (1089-1164), poet, philosopher, Biblical commentator and Astronomer, spent the last part of this life travelling in Italy and France, ending up in Eretz-Israel. He continued the publication of tables, mostly on the movement of the planets. The "Toledo Tables" were compiled by 12 Jewish astronomers led by the Cordovan Arab astronomer Ibn Arzarkali ("Azarchel"). The Latin version (translated by John of Brescia and Jacob Ibn Tibbon) was further improved in 1272 by a group of astronomers led by Isaac Ibn Said, and is known as the "Alphonsine Tables".

Rabbi Moshe ben Maimon's (=Maimonides) main contribution to Astronomy in his complete rejection of Astrology (1194). He is is unique, throughout the Centuries, in making this clear-cut. Remember that Kepler was still drawing horoscopes! Perhaps this should justify a visit to Maimonides' tomb in Tiberias.

Rabbi Levi ben Gershom ( = Gersonides, also Maestre Leo de Bagnols, Maestre Leo Hebraeus; 1288-1344), was one of the greatest of Medieval astronomers. He lived in Provence, mostly at Orange. As a mathematician, he re-discovered the law of sines and published a sine table, correct to the 5th decimal. As an astronomer (he wrote 136 "chapters"!), he is the first to have relied on his own observations (in his studies of eclipses) rather than on Ptolemy's. He invented "Jacob's staff", a navigational instrument which was widely used for 3 centuries, and was the first person kown to have used a Camera Obscura for his observations.

Rabbi Levi is also the first scientist to derive more realistice estimates of the distance to the fixed stars. Ptolemy's estimate was of the order of 10-5 light years ( a million times smaller than the distance to the nearest star), whereas Rabbi Levi reached a figure of about 105 light years, 10 times our present estimate for the distance to an average star in the Galaxy. Gersonides was also one of the greatest Medieval philosophers and published Commentaries to the Bible.

The Zohar, a compilation of Jewish mystic writings drawn in Spain in the XIIIth Century anticipates Copernicus by stating that "the whole earth spins in a circle like a ball; the one part is up when the other part is down; the one part is light when the other is dark; it is day in the one part and night in the other".

Jewish astronomers played a key role in the theoretical preparation of the great voyages of discovery in the XVth Century. Judah Cresques, forced to adopt Christianity in the massacres of 1391, later became the Director of the Prince Henry of Portugal's ("The Navigator") Nautical Academy of Sagres. Abraham Zacuto ("Zacut", 1452-1515) worked first at Salamanca but moved to Portugal after the expulsion from Spain.

As Court Astronomer to Kings John II and Manuel I, he prepared the voyage of Vasco da Gama (1496) and supplied instumentation (include his newly perfected copper astrolabe), improved tables, charts, intruction and briefs. He developed the first copper astrolabe. His very precise predictions of eclipses were used by Columbus to threaten the natives at a dangerous moment. Like all Jews, Zacut had to flee Portugal in 1497 and went to Tunis. He died in Eretz-Israel.

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