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A Secret Number in Astronomy1

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A Secret Number in Astronomy1 INTERNATIONAL SPACE SCIENCE INSTITUTE SPATIUM Published by the Association Pro ISSI No. 19, August 2007 Editorial This issue of Spatium is devoted to though his means were nothing the history of astronomy, more pre- more than a pair of simple lenses Impressum cisely to its evolution in Europe and packed in a tube of cardboard called the area adjacent to the Mediterra- telescope, the shiny objects that nean Sea. It is a play on different now suddenly became visible chal- stages: In the early days of astron- lenged the human spirit enough to omy, the observation of heavenly let him make every effort to im- SPATIUM process was on the one hand a vital prove the miraculous device even Published by the necessity to tune agricultural activ- further. In that sense, the history of Association Pro ISSI ities to the changing seasons and on astronomy is also the history of the the other hand the Sun was wor- evolution of technology and today’s shipped as the inexhaustible source extensive use of space-borne instru- of light and life. Early astronomers ments for astronomical research is were priests therefore linking the nothing else than a continuation of Association Pro ISSI art of objective observations with Galiei’s use of telescopes some 400 Hallerstrasse 6, CH-3012 Bern the richness of pious inspirations. years ago. Phone +41 (0)31 631 48 96 see The initially united stages splitted All these different stages - and many www.issibern.ch/pro-issi.html off when scientists found that the more - were the subject of a most for the whole Spatium series wandering of the Sun, the Moon fascinating lecture Prof. Giovanni and the other celestial bodies is F. Bignami, then at the University President ruled by nothing else than a set of of Pavia, now President of the Ital- Prof. Klaus Pretzl soulless mathematical functions. On ian Space Agency, gave the Pro ISSI University of Bern the religious stage, emerging dog- audience in November 2006. The Layout and Publisher mas incorporated suitable world present text follows loosely the lines Dr. Hansjörg Schlaepfer models that received the status of of his presentation; may it provide CH-8173 Neerach eternal truth irrespective of the our readers the same wealth of Printing continued progress made on the inspring thoughts as Prof. Bigna mi’s Stämpfli Publikationen AG stage of science. Galileo Galilei con- talk offered his attentive audi - CH-3001 Bern tributed to further deepening the ence... ditches between the two stages by stipulating that a hypothesis, in or- Hansjörg Schlaepfer der to be scientifically acceptable, Neerach, August 2007 must be provable everywhere at any time. This of course was provoca- Front Cover tive news for the clerical establish- The recently found sky disk of Ne- ment which did not hesitate to bra, Central Germany, is the most denounce him of heresy and to ancient image of the sky. Dating prohibit him to further teach his back to 1600 B.C., it represents the findings: the two stages had entered Sun, the Moon and – probably - the a state of fierce war for the next Pleiades. It is assumed to have served centuries. determining the beginnings of new seasons for agricultural purposes, Galilei even added a third stage that but it certainly served religious tra- is the use of technical means to ditions as well. (Credit: Landesamt overcome the limitations of the hu- für Archäologie Sachsen-Anhalt, man senses to observe nature. Al- Germany, Hansjörg Schlaepfer) SPATIUM 19 2 4440: A Secret Number in Astronomy1 Dr. Hansjörg Schlaepfer, Neerach Introduction from millennia over centuries to 4,000 Years of decades, the last 40 years have given us astronomy from space, yielding a Naked Eye view of celestial objects over the Mankind has been looking at stars whole electromagnetic spectrum, Astronomy with naked eyes for the last 4,000 i.e. the most important channel years collecting data and under- through which the sky sends us in- standing important astronomical formation about itself. In decoding facts. Since Galileo Galilei gave us such information, gathered from From Early Testimonies... the telescope, 400 years ago, astron- telescopes in space, we have, once omy from the ground has reached again, vastly surpassed the work There was a time – not too far back a profound comprehension of our done over the previous centuries - when the night sky was really dark universe; infinitely greater than had and created entirely new scientific and crowded with uncountable been possible in the previous mil- disciplines such as planetology or stars. The Milky Way was the won- lennia. In a spectacular acceleration, cosmology. derful lane that leads from the ho- Fig. 1: Summer solstice over Stonehenge. The great stone circle was erected between 3000 B.C. and 1600 B.C. It consists of a circular structure, exactly aligned with the rising Sun at the solstice. (Credit: Andrew Dunn) 1 The present text follows a lecture by Professor Giovanni F. Bignami, President, Italian Space Agency, Rome, for the Pro-ISSI audience on 13 November 2006 and is freely retold by Hansjörg Schlaepfer. SPATIUM 19 3 rizon to the zenith and down again moon between the rivers Euphra- about the Sumerian endeavours to to the opposite side. Today, atmo- tes and Tigris the Sumerian culture understand the processes in the sky spheric pollution absorbs most of prospered at that very time. The in order to sow and to harvest at the this faint radiation and the scatter- Sumerians are known to have de- appropriate time. No doubt, the ing from the ubiquitous artificial veloped not only what could be need for sufficient food and water light sources hides the beauties of called the first “professional” astron- supply was at the root of their in- the night sky to most of us. Fortu- omers but also the means to be- terest in astronomy and, since fer- nately, mankind has evolved under queath much of their broad knowl- tility of the fields was a gift from the clear night skies and has been im- edge. They invented a form of gods at that time, religious and sci- pressed by the silently wandering writing in clay with a wedge-shaped entific endeavours could co-evolve stars. We do not know the begin- stylus thereby producing docu- in untroubled harmony... nings of their observations; the eons ments that survived the many mil- since have erased most, if not all, of lennia since. Thanks to these docu- While the Euphrates and the Tigris the traces of early astronomical en- ments, we know that the Sumerian were the source of wealth for the deavours. Interestingly though, priests studied the stars and knew Sumerians and the later Babylo- these seem to have evolved inde- to correlate astronomical align- nians, another large river, the Nile, pendently(?) at many different ments with the changing seasons. was the cradle for the Egyptian civ- places all over the world some 4,000 Based on their observations they set ilization. The Nil’s periodic inunda- years ago. One of these places is up a calendar consisting of a year tions, lasting from July to October, Stonehenge, UK (Fig. 1), of which with twelve months, each of which required the mastering of the cal- the oldest traces date back as far as began at the first sighting of the new endar to tune agricultural activities 3000 B.C. The megalith’s precise moon. Sometimes, based on a re- to the river’s habits: the Egyptians orientation towards the rising Sun spective royal order, the eleventh broke a year down into 365 days, at summer solstice is a clear indica- months had to be repeated, in or- which was largely sufficient for tion, that astronomy played an im- der to bring the lunar calendar in practical purposes, and it seems that portant role in the life of their line again with the Sun’s. A Sume- further efforts to understand the constructors. rian day consisted of six watches, mechanics of the heavens were not each being two double hours long. made, at least until the later Helle- On the Continent, more precisely Each hour was divided into 60 min- nistic period. in Central Germany, another mile- utes, and each minute was divided stone of early astronomical endeav- into 60 seconds. The year had nom- Not a great river, but a long sea shore ours from that time period was inally 360 days, and so their heav- was the key asset of the classic Greek found recently: the sky disk of Ne- ens were divided into 360 degrees. civilization that evolved approxi- bra, see the front cover. Dating back Many of these ancient concepts mately at the same time on the to 1600 B.C., it represents man- have survived thousands of years northern shores of the Mediterra- kind’s very first known image of the and constitute today our counting nean Sea. The great Greek philoso- sky. The latest analytical technolo- system for time and angles, while in phers Socrates2 and Plato3 laid the gies were used to unravel some of the other areas the decimal system, foundations of our western philoso- the disk’s secrets: it is thought that presumably of Indian origin, has be- phy. Socrates’ thinking and Plato’s di- its designers had contacts to the come the standard system. alogues are characterized by mythic- eastern Mediterranean area, to allegoric symbols for describing the Mycenae and even further to Mes- The cuneiforms, as the Sumerian world: their real world is that of the opotamia, where in the fertile half- clay tablets are called, tell us also ideas, while the human perception 2 Socrates, 470 B.C.
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