14 december 1974 jaargang 40 nederlands
Inhoud II Mededelingen Agenda Binnenland Buitenlandse congressen Correspondentie tijdschrift 265 Feestrede G. Klein 267 Greek observational astronomy before Ptolemaios by Frans Bruin voor 271 Astronomical observations and instruments of Islam, idem 276 Boekbesprekingen Personalia hart index '73 natuurkunde 19
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I-1------· fl- -I- Q« « 14 ra nonZA 4 «0 « 1 m O O e Redactie: / rt . ir Hoofdredacteur: Dr. ir. H. van Krugten, ad interim BP n Redacteuren b. 1. ' Dr. H. J. A. Bluyssen (instrumentatie), C drs. J. G. Bonenkamp (onderwijs), dr. H. G. M. Heideman (boekrecencies). Phy- (f#A sisch laboratorium, Sorbonnelaan 4 St»li. t 1- Utrecht, dr. J. Polman (algemeen), prof. ,/%7 dr. Ph. B. Smith. Redactieraad: -\ ,/.- Prof. Dr. L. J. F. Broer, Prof. Dr. A Dynamus, Dr. J. Fahrenfort, Dr. Ir. H. M. 1 A. Ferdinande, Prof. Dr. L. van Gerven d»53» Dr, P. W. M. Glaudemans, Prof. Dr. S. R. t-tolot: 12&5'- :itastteoloe ro H. F. Vrehen, Prof. Dr. H. de Waard, Prof. Dr. R. van Wageningen, Prof. Dr. A. H. Wapstra, Prof. Dr. Ir. W. J. Witteman. Redactiesecretariaat: Drs. R. E. Kisman, Stichting Uitgeverij Sigma Chemie, Post- bus 1767, Den Haag, Telefoon 646915*. Artikelen, korte mededelingen, actualitei- _ -,t -1 ten op fysisch gebied en varia kunnen - f worden gezonden aan de redactiesecreta- ris. -==» Aankondigingen van lezingen, vergaderin- gen, congressen e.d. uitsluitend bestemd Voor het Iange kerstreces: twee artikelen van Frans Bruin over astronomie, toepasselijker voor 'Agenda binnenland', zende men aan kan het niet. Het eerste gaat over de resultaten die de oude Grieken behaalden op dit de Stichting Uitgeverij Sigma Chemie, gebied, waarbij zowel de Ioniirs als de Alexandriijrs aan de orde komen. Het tweede postbus 1767, Den Haagt.a.v. mej. Ir. Ch. handelt over het werk van de astronomen uit Voor-Indii en de Islamitische astronomen. M. van Dijk. Telefoon (070) 469406* Tien pagina's astronomie (267-276) en nog weI in het Engels: een stuk nascholing. Administratie: De Nederiandse Natuurkundige Vereni- ' - - -- - ging, Van der Waals-laboratorium, Vale- kenierstraat 67, Amsterdam (C), telefoon G. Klein index '73 020-226237, postgiro 263079. De admini- staatssecretaris van O&W opende deze Bijna waren we het vergeten. maar dank- stratie behandelt alle zaken betreffende zomer twee gebouwen van het universi- zij Geert van Heusden is het nog gelukt de het lidmaatschap van de N.N.V., abonne- teitscentrum De Uithof: het Transitorium index '73 in 1974 te publiceren. Op de menten op het N.T.v.N., evenals alle III en het gebouw voor experimentele hartpagina's van dit nummer staat het betalingen. Voor inlichtingen betreffende fysica. In de rede die hij bij die gelegen- afgedrukt, dus makkelijk uitneembaar. advertentietarieven en opdrachten tot het heid afstak benadrukte hij de noodzaak Aan het register '74 wordt al gewerkt, dit plaatsen van advertenties in het N.T.v. N. tot het gezamenlijk benutten van appara- ter geruststelling. wende men zich tot de stichting Uitgeverij ten en gebouwen. Daardoor komt men tot Sigma Chemie, postbus 1767, Den Haag een meer doelmatige besteding van over- t.a.v. de heer A. W. L. op der Heijde, heidsgelden. Gezien de beperkter wor- telefoon 070-646915*. dende middelen geen overbodige zaak. .' : ------r 1
astronomie
de of stars. In order to obtain latitude as indirect way, usually with the moon as an declinations, but not always the corres- well as longitude or, more precisely, intermediate step. The solar position is ponding right ascensions, as one would do equatorial declination and either right found in sunlight by turning the relevant today. Instead, like Kallippos, he read the ascension or mediation, it is necessary to ecliptic degree towards the sun, until the mediation, i.e. the ecliptic longitude of the 1 mount two rings instead of one on an ecliptic ring shadows its lower half. Next ecliptic point that culminates with the equatorial axis. By aligning each ring to a the pair of inner astrolabe rings are turned star. Later (140 AD) Ptolemaios built a star, one can measure the declination of together into their shadow, whereafter the different armillary astrolabe (Fig. 5), each as well as their difference in right exact position can be read. The position of without a fixed ecliptic ring, but in which ascension. Thus a startable can be set up the moon can now be ascertained by the astrolabe rings revolved around the and used to construct a celestial sphere. In means of the outer astrolabe ring, which is axis of the ecliptic instead of around the Alexandria, Hipparchos seems to have then fixed to the spindle with a wooden equator, and by which ecliptic longitude been the first to construct an instrument peg. After sunset, the inner astrolabe and latitude could be measured directly. of this kind for this specific purpose. He rings with the sights are free to sight a star. This was done in order to account for the called it 'Astrolabon Organon' but, in Subsequent stars can then be measured progression of the tropical points, a phe- accordance with the later custom, we will with respect to the first one without nomenon discovered by Hipparchos, and name it equatorial armillary astrolabe. further use of the moon. nowadays described as precession of the The instrument looks like PIaton's spind- Of this first complex scientific instrument equinoxes. The latter found that since the le, without the terrestrial globe in the the original description is lost. Yet it is time of Timocharis the star Spica had center, mounted on an equatorial axis and quite certain that such an instrument was moved two degrees in ecliptic longitude held within one fixed prime meridian ring, used. From the numerical data it can be away from the autumnal equinox, while it or perhaps within a pair of rings, like those concluded, as was done for Kallippos, had retained its ecliptic latitude. This of Kallippos. The 'spindle' consists of a that the rings of Hipparchos's celestial indicated a slow rotation around the eclip- pair of perpendicular colure rings, inter- globe and armillary astrolabe had divisi- tic pole, which seemed to make ecliptic secting at the axis around which they can ons for degrees and half degrees, so that coordinates more practical for future use. rotate, and of an equator ring of the same he could read or estimate to 1/2, 1/3, 1/4, This most important discovery in ancient diameter, but perpendicular to the axis 2/3 and 3/4 of a degree. To permit this, the astronomy shows the complete confiden- (Fig. 4). To this rigid structure is added an rings would have to be about one cubit in ce of an observer as critical as Hipparchos inclined ring representing the ecliptic. diameter. in measurements to within a fraction of a This ring is useful for measurements on Hipparchos used his equatorial armillary degree at a time as early as Timocharis. the sun, or with respect to the sun, astrolabe mainly for compiling a better whereas it also allows the measurement of and larger star catalogue. '- He tabulated 1. Bruin. F.. The Earliest Astronomical Observations. Ned. ecliptic longitude and mediation. the coordinates of some 800 stars with Tijdschr Natuurk 39 (1973) 315-319 During 2. Dreyer. J. L. E., A History of Astronomy from Thales to measurements, the spindle is kept in a such precision that no substantial impro- Kepler (1905) Dover Publ. Inc., New York 1953 position corresponding to the sky over- vement was achieved until Brahe. 3. Grant, M.. The Myths of Hyginos. Poetica Astronomica, Tycho Book II, Univ. of Kansas Publ.. Humanistic Studies No. 34, head. Between the spindle and the fixed (Measurements on a number of funda- Lawrence 1960 meridian rings, which carry everything, a mental stars with the equatorial astrolabe 44. Manitius, K. Hipparchi in Arati et Eudoxi Phaenomena. Commentariorum, Teubner, Leipzig 1894. fits which can rotate a ring freely around show errors of the order of only 1 /10th of a 5 Dicks, D R., Early Greek Astronomy to Aristotle, also: diameter as celestial axis, and which degree, which is about the limit of the Solstices. Equinoxes. and the Presocratics. J. Hellenic Studies serves to sight a star 86 (1966) 26·40. and measure its ancient armillary instruments in general. 6 Vitruvius. Book nine of The Ten Books on Architecture, coordinates on the spindle. In addition The majority of stars show mean devia- Translated by M. H. Morgan, Dover Pubi. Inc., New York there is a double ring sights 1960. with mounted tions of roughly 1/4 degree in mediation 7 Waerden. B L van der, Die Astronomie der Pythagoreer, similarly inside the spindle. These rings, and 1 /2 degree in ecliptic longitude. The Royal Netherl. Acad Sciences. Section Physics, First Series, the pair Volume 20 (1961) No. 1, pp. 6-80. Also: Basic Ideas and inside and the one outside the latter error is partly due to the use of the Methods of Babylonian and Greek Astronomy, Symp. on spindle, are called astrolabe rings, becau- moon as intermediate and errors in the Scientific Change, Univ. of Oxford, July 1961. se they are used to 'take 8. Manitius, K.. Handbuch der Astronomie des Klaudios the stars'. The calculation for the correction of the paral- Ptolemaios, Two volumes. Teubner, Leipzig (1911) 1963. ecliptic ring and one of the inner astrolabe lax. 9. Bruin. F. Vondjidis, A.. The Books of Autolykos. Amen can University of Beirut, Beirut. 1971. rings are divided into 720 parts. Theoretical historians and astronomers 10 Heath, T L. Aristarchos of Samos. Clarendon Press, Using the two astrolabe rings simultane- alike, having no direct personal experien- Tford 1913 Also: Greek Astronomy. Dent and Sons, London two stars ously for allows one to read their ce with observations, have paid undue 11 Bruin. F . L'6clipse d Hipparque et les grandeurs et difference in right ascension on the spind- attention to distances de la Lune et du Solei], Onon 12 ( 1967) No. 100, individual errors in ancient 50-54. le. The position of a star can also be observations, which usually do not war- 12 Vogt, H., Hipparch's Fixsternverzeichnis, Astron Nachr measured relative to the sun, but in an rant a detailed analysis). He measured 224 (1925) No. 5354-55. Columns 17-62. Astronomical observations and instruments of Islam Het werk van de astronomen uit Voor-Indi8 en van de Islamitische astronomen tot + 1700 A.D. is hier in 't westen veel minder bekend, dan het werk van de 'Oude Grieken'. E6n van de opvallende aspecten van dit werk is zijn nauwe verbondenheid met de wiskunde uit die tijd. Het boeiende relaas in dit artikel. Frans Bruin
1. The Hindu tradition. The origins of astronomy was further developed in Se- tain is that, around 500, the bulk of this pre-Islamic Persian and Arab astronomy leucia, and somehow would seem to have material was transmitted once again to are not well known. There is some eviden- survived in Ktesiphon3. There are reasons India where, in the hands of the mathema- ce that fragments of Babylonian astrono- to assume that at that time it became tician Aryabhatta, it was molded and my' reached the Hindus, perhaps by the infused with Greek astronomy, about as it integrated into the algebraic style of ear- sea route, because the Hindu siddhantas was known to Hipparchos2, and that in lier work. This fusion turned out to be a (astronomical handbooks) seem to con- this form it was absorbed and carried on very fortunate one. It gave rise to the tain Babylonian elements. Linear'zigzag' by the Sasanian astronomers. More cer- algebraic treatment of geometric pro-
271 astronomie blems, and generated the basic excercises of trigonometry. Sine and Versed Sine are Indian inventions, while Tangent and Co- tangent emerged naturally from observati- ons with the gnomon. The Hindu siddhan- tas4 differed from the early Greek treat- ment in their use of the Babylonian notation instead of continued place-value „ fractions, using base sixty and a zero «1 ,/m symbol. r ; st Some of the siddhantas of that time ms ----- describe simple astronomical instru- ad w ments. Chapter eight of the Surya sidd- hanta gives a description of Platon's spindle and mentions various other small instruments. As a whole it would seem, however, that the basic instruments used t - tr were the gnomon for astronomical obser- vation and the waterclock for civil time { '1 keeping. The thorough investigation of the gnomon, the repeated application of the pythagorean theorem, and the intro- (f duction of Tangents, turned out to have far-reaching effects on observational techniques. In the Surya siddhanta stars at transit are sighted along the top of a gnomon by looking at a mirror placed flat on the ground. By using a Tangent table this allows a simple and accurate way of Figure 1. Cut-away view of the Arab observatory built by the author in the village of obtaining the meridional altitude and the Kfour on Mount Lebanon at 700 meter attitude. m marble meridian strip of sundial onthe declination of stars, and it opens a way for floor inside, m' the same on the roof. ew east-west strip used during equinoxes, ms mural similar instruments using the local sextant of 3 meter radius, st stone table with reference point. t sighting tube, r small ring coordinates of azimuth and altitude. Di- on the roof close to orifice of sundial, trp line of sight to polar star. d short brass ruler on rect angular measurements were also ma- pillar being one degree when viewed from o. The distance od is 16 meters. d is used as de however. The Pancha siddhantika artificial horizon for setting sun at equinoxes. a frame for altitude-azimuth instrument. tr mentions a graduated ring, pierced by a triquetrum. small radial orifice, permitting to take solar altitude, using a plumb-line. It also of the Zij al-Sindhind and the Zij al-Shah the zijes tended to become more accurate a the circles describes celestial globe with the solar declination use was and extended, culminating in Ulugh Beg's of the tropics on it, to find the time of the (only for made of the Almagest). Zij al-Kurgani, composed by Jamshid the solar altitude is known. day if Muhammad ibn Musa al-Khwarizmi was a al-Kashi in 1420. Normally a zij begins All siddhantas show how astrono- closely Persian mathematician who worked for with a description of calendars and' on my was related to astrology. All are based the 'Abbasid Khalif al-Ma'mun (813-833). how to convert one into the other. Hindus on the the theory that planets, the sun, and In mathematics he is honored by the and Moslims alike use the lunar calendar the moon had been together at the begin- words and algebra (Hijra), where the month begins on the ning of the constellation Aries in the year algorithm (his name) (from al-jabr, the equation, in the title of evening when the new lunar crescent is 3102 BC (later thought to be the year of the one of his books). His Zij is the first to be actually seen for the first time. This is of biblical flood). This allowed the calculati- in Arabic. It is not known the from composed particular importance for fasting on of the planetary positions given whether he made astronomical observa- month of Ramadan. Lunar visibility tables periods of their cycles' to within a few tions, but he acted as eye-witness in some therefore are found in many zijes. The foresaw the degrees. theory recurren- 0f them. In Islam, crucial observations Ptolemaios used only one trigonometric after a ce of their conjunction world-cycle made for the construction and correction table, namely the one of the Chord. Most of 4 320 000 years. of zijes were witnessed by a number of zijes have a chapter on mathematical 2. The Islamic Zijes. The Arabs became trusted persons, as was also the first tables for the Sine, Tangent (shadow), and familiar with elementary astronomy sighting of the lunar crescent at the Cotangent (second shadow), but some- through Persian sources, and it was only beginning of each month. Considering the times also for the Versed Sine or Arrow in 771 that the siddhanta of Brahmagupta enormous amount of computational work (1-Cos 0), and the Secant. Even in the (628) was brought from Ujjain to the royal involved in writing a new zij, the supervi- early zijes these are for each quarter court in Baghdad. It was translated into sion of observations is not surprising. It degree. Already ibn Yunis (1003) calcula- Arabic by Ibrahim al-Fazari, and hence- seems likely that the observations, as well tes Sines and Tangents for each minute of forth called Zij al-Sindhind (Zij meaning a as the composition of zijes, often were the arc to nine decimal places. Also the Zij collection of astronomical tables). About combined activity of a group of astrono- al-Kurgani gives the Sine and Tangent for at the same time the Arabs obtained the mers working as a team. each minute with this accuracy, but by siddhanta of Aryabhatta, composdd in The earliest zijes dealt mainly with the this time there are tables for all common 500. These translations were disappoint- calendar and methods for calculating the trigonometric functions. The spherical ing in that they turned out to be mainly positions of the planets, based on Hindu trigonometry of Ptolemaios is based sole- manuals of instruction for computations, procedures. In 'Abbasid times these were ly on Menelaos' theorem, which often is without much explanation. Two more replaced by the tables·of Ptolemaios and awkward to apply, and which was un- zijes of this early period became impor- Theon, while Hindu trigonometry remain- known to the Hindus. Many zijes tabulate tant in Islam. The older one, the Sasanian ed in use and was further developeds. functions which are basic to spherical Zij al-Shah, was based in part on the work Most authors were content with Theons astronomy, such as declination and medi- of Aryabhatta, and had lastly been cor- parallax tables for the sun and the moon, ation of ecliptic points, and ascensions or rected in 556 in Ktesiphon. The other one, but some adapted them to their own rising times, and these allow to by-pass the zij of al-Khwarizmi, is a combination geographical location. As time went on, Menelaos' theorem.
272 astronomie
The Hindus used twenty eight prominent tory. Here many prominent scholars wor- stars, or groups of stars, near the ecliptic ked, among them Ishaq and Thabit. (the lunar mansions) to keep track of the Great attention was paid to the observa- lunar month, similar to the Babylonian tion of the solar parameters. Thabit mis- practice. These are also mentioned in the takenly claimed to have obtained an im- zijes. The zijes may contain further: proved correction for the tropical year, 1 Ephemerides of the fixed stars, with their namely 3651/4 minus 5/300th of a day,
positions given in ecliptic coordinates, -. instead of the Hipparchean term of sometimes with magnitudes and colors. 30 i - 1/300th. A better correction (one second The ecliptic longitudes and latitudes and / of time to small) was found only much the mean motions of the planets for a r ¥ W' later by Tycho Brahe, and is in this *f E number of years, as well as their stations -i : -4, p notation -2.35/300th. Thabit seems to be and retrogradations, computed according ,-4 ' the first to mention that solstices and to the epicycle theory (usually the Ptole- equinoxes can be measured more accura- mean model). This was an important part 1 £ 7.6 tely by counting days before and after the of the zij, that needed regular correction i '4 4.' ..1=ek.Al. extrema of the solstices and halving the and updating. The planets were of emi- ' ' J amount, a method that we suggested nent importance to astrology. The zijes t.:' ' 9 .li earlierl to have been in use already in contain instructions «- Babylon by Copernicus often for computing I ' 1 t (later also used solar and lunar eclipses, usually in terms -- , 1-"-* al r--m='. and by Tycho Brahe). From such mea- of the Hijra calendar, as well as for the + 2.Il*Bliail-M.*- surements followed the accurate value for equation of time for the sun. Finally there the ecliptic longitude of the sun's apogee, may be tables to determine the time of day which was then compared to the value or night from the altitude of the sun or a Figure 2. Armillary astrotabe at the Ante- rican University of Beirut, made after the given by Hipparchos: on longitude and star, depending ecliptic in for a given latitude. There are also some one used in the observatory of al-Tusi longitude error Maragheh. auxiliary tables which may or may not be - 140 Hipparchos 65°30' +45' included in the zij, such as the times of the 831 Musa brothers 8245 -05 pagan astronomer from Harran, under 1003 Ibn Yunis 86 10 -13 five daily prayers, geometrical construc- whom most Greek books on astronomy 1588 Tycho Brahe 95 30 +27 tions for finding the direction of 1969 Recent vdue 102 27 00 Mecca, were edited in Arabic. During this period the curves on flat sundials for drawing 'Ahmad ibn Muhammad al-Farghani wrote different orientations, engraving circles an elementary summary of the Almagest From the two data it followed that the on astrolabes (stereographic projection), (Kitab fi' Harakat) which became very solar apogee had progressed at a rate of as well as various kinds of astrological popular. about 1 42 degrees per century, a value tables. Under Khalif al-Ma'mun, a son of al-Ras- already known to the Hindus (actually it is Like in earlier Islamic times, therefore, hid who had been educated in Marw, the 61.5" per year). This erroneously was consisted of the astronomy study of the scholarly activities reached a peak, and an thought to be identical to the Hipparchean and positions motions of the sun, moon, intensive program of astronomical obser- precession, whereas only some 80% of it and stars on the celestial planets sphere by vations was started under Yahya ibn Abi is due to this. means of mathematical computations and Mansur. The latter composed the so- The astronomers of Baghdad also measur- based on a set of reliable observations. Its called Verified Tables (Zij al-Mumtahan) ed the maximum ecliptic latitude of the aim wasto predict celestial phenomena, to based on newly observed parameters. Abi moon by its meridional altitude and found determine rising times for casting horo- Mansur also determined the geographic it to be 4°41', between the Hindu value of scopes, and to find the hours of day and latitude of Baghdad, and with 'Ali ibn 'Isa 41/2 degrees and the more accurate Hip- Islamic were the determi- night. Uniquely the length of one degree of geographic parchean value of 5 degrees. Later ibn the nation of direction of Mecca and of the latitude with an error of less than one Yunis observes 5'8', but none of the times of the five canonical prayers. In the Percent. These observations were of great Arabs noticed that the orbital inclination course of astrology and the use of time, importance because they allowed to place oscillates between 4°58' and 5°17', as was the planispheric astrolabe, as well as the Baghdad on a map of the world that was discovered by Tycho Brahe. observation of the new lunar crescent, being made. The data were found by 4. The Almagest. Except for the gnomon, an integral part of became the Islamic taking the solar meridional altitude, pre- the observational instruments used by culture. sumably with a quadrant, on the same day Ptolemaios are described in the Almagest. 3. The House of Wisdom. In 762 the at points 185 km apart in the plane of The former is used only for finding the 'Abbasid Khalif al-Mansur, following Sinjar, to be repeated a few years later in direction of the prime meridian line, astrological judgement of the Persians the plane of Palmyra. Other observations which can be done with an error of about al-Nawbakht, Masha'Allah, and made in Baghdad were those by the sons ten minutes of arc. Solar meridional alti- al-Fazari6, chose the Babylonian village of of Musa ibn Shakir, made between 850 tude is taken with the mural quadrant and, Bagh-Da-Du as the site for the new capital and 870 from their house near Bab al-Taq. if its radius is about one cubit (50 cm), the of Islam. Al-Mansur invited to his court Al-Khwarizmi was eye-witness to some of error in altitude is about two minutes. The distinguished men of all disciplines, many these. A long series of observations (be- quadrant is an improvement over the from Marw and Jundi-Shapur, which were tween 885 and 933) was also made by the meridian rings in that it is cheaper and centers of Greek scholarship. The latter Amajur family. Another observer and more rigid. For a large accurately con- city had an astronomical observatory. mathematician, Habash al-Hasib of structed quadrant the error may be reduc- Al-Mansur's successor Harun al-Rashid Marw, the calculator, worked in Damas- ed to one minute, but only Tycho Brahe (786-808) collected Greek manuscripts cus and composed several zijes, his best achieved this. The equator ring is used for which were translated into Arabic and known being an improved version of the finding the equinoxes. Three steps are studied. The translation of the Elements Zij al-Mumtahan. These were private and required in order to erect it, namely the of Euklides and of the Almagest was somewhat isolated activities. In order to construction of the prime meridian line by completed by al-Hajjaj ibn Mae in 827, coordinate the efforts, at the suggestion of means of the gnomon, finding the equi- and a superior translation by the Nestori- Musa, al-Ma'mun founded in Baghdad the noctial points with the meridian rings, and an Ishaq ibn Hunayn (. 860) was further House of Wisdom (Bayt al-H'ikma) under levelling it at right angles to the polar corrected and commented on by Thabit the direction of a certain Salam or Salm. direction. This results in an error of74 day ibn Qurra. The former was the greatest This Academy, similar to the Museum in in the determination of the equinoxes. translator of the Arabs, the latter was a Alexandria, had a library and an observa- Similar problems arise for the erection of
273 astronomie the armiltary astrolabe, which can be used The longest treatise on the astrolabe to measure the celestial coordinates of known is by al-Sufi (see below). any luminary. The smallest mean error With Muhammad al-Battani (858-929), the one can expect here amounts to some six „, most renowed of the Arab astronomers, minutes of arc. Ptolemaios replaced the c we find the astronomy of the Almagest Hipparchean ruler by his triquetmm, fully absorbed, and from then onward which he used for finding the angular · Islamic astronomy is almost completely diameter and meridional altitude of the Ptolemean. Like Thabit, al-Battani came moon. From the observations follow the from Harran, but worked in al-Raqqa. He lunar parallax and latitude with an error of made observations from 877 until 918 and about ten minutes. Finally, Ptolemaios wrote the Zij al-Sabi' (911). This text, describes a celestial sphere which was not although based on Ptolemaios, is more used for observation, but served to find condensed and aimed at solving practical the position of the sky at a certain moment problems. He describes the mural qua- and at a certain location with an error of drant and triquetrum of Ptolemaios, but is one ar two degrees. The quadrant, eclipti- Figure 3. Small instruments used by the said to have increased the radius of his the cal armillary astrolabe, and triquetrum author. On the left a quadrant. In quadrant to about one meter, and to have were all improvements on earlier instru- middle a celestial sphere. At the right an added a ruler to it. He also describes a flat ments introduced by Ptolemaios. With the astrolabe. sundial and a new kind of brass sphere Arab astronomers we note that each would have neither this nor an armillary which can be used for solar observations. authority on instruments takes pride in astrolabe. He would need a little study With this sphere the solar position is adding at least one instrument of his own with a niche to keep his books (stacked found by placing a thin cylinder on it in design to the existing set. horizontally, not upright as we do nowa- such a way that it casts no shadow. From Throughout the Islamic period the obser- days). His work would have to do with observation of the tropical points he finds vations consist of three types: (a) Naked- tables, numbers, and computation, rather an excellent value for the obliquity and the eye observations of first visibility of the than with actual observation. The porta- eccentricity of the solar orbit Table II. lunar crescent, conjunctions of the moon ble astrolabe he would carry around not so From improved measurement of lunar and and planets with a star. Study of eclipses, much to find the time of day and night, solar diameters al-Battani concludes (con- comets, and new stars. These would need than as a trademark of his profession. trary to Ptolemaios) that annular solar no instruments. Small portable instruments used by the eclipses should be possible. His catalog of Arabs are this astrolabe and a Solar eclipses were observed by looking at plane stars, which has only half as many entries the reflected image of the sun in a water special kind of quadrant (Figure 3), whe- as the one of Ptolemaios, is derived from by Coperni- by surface. (b) Meridional transit boserva- reas the cross-staff, as used the latter adding 11°10' to all ecliptic tions transit observations of the sun and cus and Tycho Brahe, seems to have been longitudes (one degree per 71 years). the moon, to find or correct their orbital a European invention (possibly made in Al-Battani uses the Hipparchean ruler to elements and to determine local geogra- southern France by Levi Ben Gerson in find the position of the new lunar crescent phic latitude. This would be done with 1328). It was really a modification for in the twilight sky. the mural quadrant or some similar devi- large angles of the Hipparchean ruler. The 6. Islamic astronomy. Whereas the scho- ce. quadraftt was a kind of folded-up version larly achievements under the 'Abbasid Observations of this kind are relatively of the astrolabe and may be an Islamic Khalifate, including those of al-Battani, invention around 1000. The astrolabe seen a simple and do not require sharp eye-sight. of can be largely as struggle to master serves two functions. The front carries an (c) Spherically orientated observations the inherited material, we have now a a point with the armillary astrolabe (Figure 2) in open rete representing stereographic reached where the astronomical order to find the celestial coordinates of projection of the heavens, which may be activities of the Arabs have become more rotated around a a coordi- truly Islamic. We witness the design of stars and planets. These are by far the central pin over most difficult and elaborate observations. nate grid of azimuth and altitude circles. several new instruments and the gradual The instrument seems to have been used This part of the astrolabe may have been development of a new grand style of known already to Hipparchos and is fully operation7. The Buwayhid Sultan Adud for specific cases only. No systematic series of Islamic observations have come described by Ptolemaios in his treatise on al-Dawla (949-982) once again showed down to us. the planisphere. The back of the instru- great interest in astronomy. His son, In Islam there were two kinds of observa- ment carries a ruler with sights which also Sharaf al-Dawla (982-989) founded a new may rotate around the central pin. The tories, namely small private ones, and observatory in the garden of his palace in those attached to large institutions, spon- ruler is used to take the altitude of the sun Baghdad under the leadership of Abu or a star. This sored by a local ruler. An individual observational part may al-Wafa', one of the prominent mathema- astronomer, such as al-Battani or ibn have come into use in the time of Theon ticians of the Arabs. It came to great Yunis, would use his home for making (360). The astrolabe therefore is a Greek prominence with the mathematician Abu observations or, if he were a muwaqqit, he instrument, but its extensive use in Islam Sahl al-Kuhi, who directed the observa- made it Islamic astrono- would observe from the courtyard or the the symbol of the tions, the astronomer 'Abd al-Rahman mer and for his roof of his mosque. He would possess astrologer. It can not be used al-Sufi, famous for Uranometry (illus- serves well for some portable instruments: a conical gno- precise observations, but trated book on the constellations), and the or the mon with marble baseplate and a plumb- finding the hour of the day night and mathematician Abu Ishaq al-Harrani. The Islamic astrolabe quickly take very large di- line, a mural quadrant, both relatively horoscope. The first instruments small (about one cubit) and, for quick was made by al-Fazari, and an excellent mensions, because, following al-Battani, theory, orientation, a a planispheric treatise on the construction, and it was believed that this would improve globe and the accuracy. For astrolabe. The flat roof would be a good use of the astrolabe was written by the Adud al-Dawla, al-Sufi Jew Masha'Allah. A famous astrolabe makes solar a meridi- place to observe, but if the house were on observations, using a hillside facing south, the terrace would maker was 'Ali ibn 'Isa al-Asturlabi, a an ring of five meters diameter. al-Ma'mun. be equally convenient (Figure 1). If the Muslim astronomer under For Sharaf, Abu Sahl constructs inside a means would be there, such as was the case for the Musa brothers and the Ama- Table U some instruments like a obliquity error eccentricity error jur family, larger -140 Hipparchos 23 0 51 +7 208 104 +40 quadrant or sextant and an equator ring 831 Musa and Yahya 23 35 +1 911 al-Battani 23 35 0 173 10' +05 would be installed permanently, Normal- 994 al-Khujandi 23 32 -2 ly, however, the private astronomer
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building the lower segment of a hollow dium of Astronomy (Tadhkira), a succes- sphere: A pencil beam of sunlight entered sor of the book of al-Farghani, and his through an orifice in the roof, positioned Textbook on Plane and Spherical Trigono- at the center of the sphere, and the 4. metry (Shikl al-Qita'), the first of its kind resulting lightspot (an image of the solar s (1260). All algebraic equations of the disk) permitted the measurement of solar Arabs were written out in words, without altitude. The technique is reminescent of making use of the modern symbolic nota- f al-Battani's brass sphere, only now the , s tion, but otherwise these books are the 1 sphere is hollow and has a radius of twelve 5 - 21 1 forerunners of the standard textbooks on R meters! A few years later (994) Abu 2, goniometry and astronomy as they have Mahmud al-Khujandi, co-inventor of the been in use in high schools in Europe for Sine Theorem for spherical triangles, built the past century. Al-Tusi's observatoryg in Rayy for Fakhr al-Dawla a stone ' 1 was built on a flat hill west of Maragheh. sextant of twenty meter radius, also with i P i. Its main domed building had a diameter of an orifice at its center, one degree of its twenty three meters and a height of about arc comprising 35 cm. With this large , f fifty (roughly three times the size of the instrument, called Fakhri-Sextant, he Tower of Winds in the ancient market measured the ecliptic obliquity (see table 4/ place in Athens). On the floor inside was a above) and the local latitude. Although his e meridian strip which received sunlight accuracy is not as high as he likes to /,17 1 through an orifice in the southern part of believe (the error was -2'), he is the first the dome, and could be used to measure to state firmly that the obliquity is de- solstices and equinoxes. Outside were a creasing, a phenomenon as important as Figure 4. Sine-Azimuth instrument recon- number of fixed structures (Figure 4) the Hipparchean precession, but about a structed from the treatise of al-'Urdi. P made of stone, wood, and brass for other hundred times as difficult to detect (it pole, SS sights. observations. The observatory was com- amounts to one minute of arc per 130 pleted in 1270 and survived until 1316, but years). and built the first altitude-azimuth instru- today nothing of it remains but a small brass Before continuing about the large instru- ment (of seven meters diameter) for th e sphere which is kept in Dresden. Observations were ments, we must pause for a moment to observatory of 'Ala al-Dawla in Hama- thought to be necessa- at least a mention four great men who, around the dan. He did not believe in ry for thirty years, complete astrology, and of no observations of year 1000, constitute the peak of Islamic seems to have been the first to remark that period Saturn, but any importance are known to have been I scholarly achievement, and who all in the speed of light must be finite. made. their own way were important to astrono- These men thought and lived much like my. The first is Abu al-Hassan ibn Yunis, the scientist of today. They carried out An illustrated treatise of Muayyad al- an astronomer who lived in the Fustat practical experiments on chemicals, on 'Uridi gives a detailed description of the district of Cairo under the Fatimid Khalif light, and measured the density of materi- instruments that were constructed. Apart al-Hakim, and who is the author of the Zij als. They studied physical phenomena from the well-known Greek instruments, al-Hakim. This'zij is twice as extensive as such as refraction and the rainbow. Yet such as the mural quadrant, triquetrum, the one of al-Battani and contains many we must not think that this was an entirely and armillary astrolabe, there are also five observational data of earlier Islamic astro- new attitude. The astronomers of Bayt new Arab instruments. One of these, the nomers. Ibn Yunis is famous for his al-H'ikma also wrote on these subjects, Sine-Azimuth instrument, based on a de- elegant treatment of problems of spherical while much the same was done already in sign of ibn Sina, is reproduced in figure 4. trigonometry. He also made many obser- the Museum of Alexandria. Ibn Sina's The outcome of the entire enterprise, vations himself. About one, made in Qanun shows great likelyhood with the apart from the pleasure it may have given Babylenian fashion, he reports as follows: work of Galen, al-Manazir and al-Tafhim its participants, was the Zij al-Khan, 'On the 18th of June 995 around 7h 40. are simply expansions respectively on the published in 1271, three years before Venus was seen about 2/3 or 3/4 of a Optics and Tetrabiblos of Ptolemaios. The al-Tusi died. A little earlier, at the other degree north of Regulus, about a fitr on latter already describes experiments on end of the Mediterranean, new planetary sight. I determined their conjunction (in the refraction of liquids, and explains tables had been prepared under king ecliptic longitude) by imagining a large correctly the effect of atmospheric refrac- Alfonso X of Castile. These so-called circle through the ecliptic poles to pass tion on astronbmical observations. Alfonsine Tables were completed in 1252, through the two luminaries'. A younger Cairo never had a true observatory. Ibn and remained in use for several centuries. contemporary of ibn Yunis is Abu'Ali ibn Yunis is believed to have made his obser- They replaced the Toledo Tables compo- al-Haytham, from Basra, who is known vations at home. In the time of al-Afdal sed by al-Zarqali (- 1050) of Cordoba. first of all as a physicist because he wrote (1125) a ten ton bronze ring of five meters In 1419 Mirza Ulugh Beg (1395-1449), a book on optics (Kitab al-Manazir). diameter was placed on top of Bab al-Nasr grandson of Timur-Lang, well versed in Using a camera obscura he studied the (Gate of Victory), and the solar altitude mathematics and astronomy, started an properties of light beams, and put an end was taken with it. But soon it was consi- observatory and an academy near his to the Greek conviction that light emerges dered a bad idea and the ring was destroy- capital Samarkand. In charge of the many from the eye. The idea of using a darkened ed in 1130. When, after sacking Baghdad astronomers were Jamshid al-Kashi, Qa- room with an orifice in the door may be in 1258, Hulagu Khan, the grandson of di-Zada al-Rumi, and later 'Ali Qushji. traced to his contemporaries Abu Sahl and Ghingiz Khan, took residence in Marag- The main observatory building contained al-Khujandi. The third man, Abu Rayhan heh, he ordered the Persian philosopher a meridional sextant of fourty meters al-Biruni from Khwarizm was a critical and mathematician Nasir al-Din al-Tusi, radius, each degree of the arc being70 cm. historian best known for his History of to build an observatory, with the aim of The other instruments were much the India (Ta'rikh al-Hind). He also wrote producing a new zij. At the same time the same as those of al-Tusi, although some extensively on astronomy, and composed observatory would hold the booty of were larger. The armillary astrolabe had a a Manual of Astrology (Kitab al-Tafhim) books taken from the House of Wisdom. diameter of two meters, and one would that became very popular. Finally, al-Hu- The costs of construction were so immen- guess that Ulugh Beg had given the royal sayn ibn Sina from Bukhara was a philo- se that Muhammad al-'Urdi, an instru- command that everything should be twice sopher and physician, famous for his ment maker at the observatory, later said as large as anything that had been built work on medicine (Qanun fi al-Tibb) of that only 'Allah could pronounce the before. The description of the major about a million words. He also wrote on numbers'. Al-Tusi wrote many books, instruments is found in a treatise of 'Abd astronomical observations, and designed among which are best known his Compen- al-Mun'im al-'Amili al-Fotuni (Isfahan
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1562). An instrument designed by Ulugh pole, a kind of improved cross-staff, Beg himself is reproduced in figure 5. The copied from his contemporary Tycho result of the activities led to the Zij . =S==».. Brahe. The manuscript also mentions a al-Kurgani, written by al-Kashi (1437), -,« -447'r: r mechanical clock with geartrain. The first often praised in later centuries for its - use of a clock in astronomy seems to have supernova accuracy. His catalog of stars, however, »12202;IEFilifilz.Lisiliumcily,741 been for the observation of the was not obtained from observation, but by of 1572 by the Landgrave of Hesse Kas- taking over the list of al-Sufi, corrected 24»4, 1- 'F-71 sel. Here we witness a fusion of Islamic for Hipparchean precession. It would \. ' ' - 17 and Christian astronomy, the one decli- seem, therefore, that none of the ning, the other on the threshold of exciting Islamic -
boekbesprekingen wetenschappen die begrip willen krijgen zien, om maar niet te spreken van een voor de plaats van de natuurkunde in het radicaal anti-natuurwetenschappelijke Structure and Bonding, Volume 11 geheel van de cultuur. In de tweede plaats houding waarvan vele voorbeelden uit Springer Verlag, Berlin, Heidelberg, New Sterke fig., kan het ook worden gebruikt bij cursussen vorige eeuwen worden gegeven. York, 1972, 170 blz., 57 15 x23 cm; natuurkunde en maatschappij. Om deze hoofdstukken zijn ook die waarin de ing. DM 54,- doelen te bereiken beschrijft Schroeer een geschiedenis van het A-bom project wordt aantal onderwerpen uit de geschiedenis beschreven en de analyse van de reden De inhoud van dit deel betreft biochemi- van Stonehenge tot energieproblemen waarom dat in Nazi-Duitsland niet van de sche onderwerpen. Het eerste artikel van vanuit verschillende gezichtspunten: de grond kwam. Te summier zijn de hoofd- A. J. Thomson, R. J. P. Williams en S. kloof tussen de alpha en beta-weten- stukken over de oudste natuurwetenschap Reslova betreft complex verbindingen ver- schapppen, de technologische invloed op en vooral de laatste hoofdstukken over de want aan Pt(NHJ)2C12· de kwantiteit en de kwaliteit van het huidige problemen. Bij de beschrijving Hoewel de recent ontdekte antikankerwer- bestaan en een analyse van de weten- van de energievoorraden gaat de auteur te king uitgangspunt is, worden vrijwel uit- schapsman als deskundige of als geinfer- optimistisch te werk en op de technologi- sluitend chemische structuur en eigen- meerde leek. sche en sociale merites van de verschillen- schappen behandeld. Twee bijdragen be- Ieder hoofdstuk is voorzien van een aantal de mogelijke energieprojecten gaat hij treffen respectievelijk Vitamine B 12- interessante discussievragen en een goed helemaal niet in. enzymen en molybdenium-bevattende en- gekozen literatuuropgave. Hoewel dit laatste het boek naar mijn zymen. Het slotartikel van J. B. Neilands mening wat onvolledig maakt om in cur- behandelt het voorkomen en de fysiologi- Beoordeling: Hetboek is zeker interessan- sussen voor alpha's te gebruiken, is het sche rol van ijzerverbindingen in dierlijke te lectuur, niet alleen voor alpha-weten- boek het lezen en aanschaffen zeker en plantaardige organismen. J. A. A. Kete- schappers maar ook voor natuurkundi- waard. Prof. dr. E. Boeker laar. gen. Onder de laatste groep zullen velen met belangstelling de hoofdstukken lezen personalia Algemeen over de natuurkunde van Goethe, de Benoemingen Dietrich Schroeer romantiek en de kritiek van Goethe op de Professor E. Barendrecht (VU) is bij KB Physics and its fifth dimension: society mechanistische natuurwetenschap van nr. 40 van 5 november 1974 benoemd tot Addison-Wesley, New York, 1972, 378 zijn dagen. De situatie lijkt op een aantal gewoon hoogleraar in de afdeling der pag., 13,5 x 20,5 cm2 punten op de huidige periode waarin er Scheikundige Technologie van de TH geven in de Inhoud: Het boek is in de eerste plaats ook een romantische beweging groeit die Eindhoven, om onderwijs te bestemd voor studenten buiten de natuur- de natuur weer als een geheel wil gaan elektrochemie.
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