EGYPTIAN MATHEMATICS Jens Høyrup
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8 EGYPTIAN MATHEMATICS Jens Høyrup Ivor Grattan-Guinness in memoriam The primary references of the term “Egyptian mathematics” are the computa- tional techniques and the underlying mathematical knowledge attested in Pharaonic written sources. Secondary references are, on one hand, the corre- sponding techniques etc. as known from demotic sources and, on the other, the geometrical procedures used in Pharaonic and subsequent architecture and visual arts. Greek mathematics producedinHellenisticEgyptisthusnot included. Accordingly, all dates in the following are bce when not specified to be ce. THE SOURCES The most important written sources for Pharaonic mathematics are the Rhind Mathematical Papyrus (henceforth RMP)1 and the Moscow Mathematical 1 Two editions with ample analysis exist: T. Eric Peet, The Rhind Mathematical Papyrus, British Museum 10057 and 10058. Introduction, Transcription, Translation and Commentary (London: University Press of Liverpool, 1923); Arnold Buffum Chace, The Rhind Mathematical Papyrus. British Museum 10057 and 10058,2vols.(Oberlin,OH:MathematicalAssociationofAmerica,1927–9),vol.1(withtheassistance of Henry Parker Manning): Free Translation and Commentary and a Bibliography of Egyptian Mathematics by R. C. Archibald; vol. 2 (with Ludlow Bull and Henry Parker Manning): Photographs, Transcription, Transliteration, Literal Translation and a Bibliography of Egyptian and Babylonian Mathematics (Supplement),byR.C.ArchibaldandtheMathematical Leather Roll in the British Museum, by S. R. K. Glanville (the literal translation is indeed very literal; it is used in all quotations below from RMP). A recent facsimile edition with description and discussion and translation of large extracts is GayRobinsandCharlesShute,The Rhind Mathematical Papyrus: An Ancient Egyptian Text (London: British Museum Publications, 1987).Valuable general accounts of Egyptian mathematics which (by necessity) deal extensively with RMP are: Kurt Vogel, Vorgriechische Mathematik. Volume 1: Vorgeschichte und Ägypten (Mathematische Studienhefte, 1; Hanover: Hermann Schroedel / Paderborn: Ferdinand Schöningh, 1958); Richard J. Gillings, Mathematics in the Time of the Pharaohs (Cambridge, MA: MIT Press, 1972). After the manuscript for the present article was finished (essentially in 1997), Marshall Clagett has published Ancient Egyptian Science. A Source Book. Volume 3: Ancient Egyptian Mathematics (Memoirs of the American Philosophical Society, 232; Philadelphia, PA: American Philosophical Society, 1999). This volume reproduces the facsimile edition of Chace’svolume2and includes a translation kept close to that of the same volume as well as an extensive analysis. Extensive analysis of RMP as well as other Middle Kingdom sources is also found in Annette Imhausen, Ägyptische Algorithmen. Eine Untersuchung zu den mittelägyptischen mathematischen Aufgabentexten (Ägyptologische Abhandlungen, 65; Wiesbaden: Harrassowitz, 2003). Egyptian mathematics in its social setting is dealt 144 Egyptian Mathematics 145 Papyrus (MMP).2 To these can be added a few shorter papyri containing mathematical problems; a couple of listings of equivalent fractions; and a larger number of accounting papyri that apply the metrology and show how the basic arithmetical techniques were used. The RMP is a copy from a Middle Kingdom original (Amenemhet III, c. 1800), made during the Hyksos period; it is a teacher’sorcalculator’s manual, containing several tables (to which we shall return) and some eighty problems with solution. The MMP seems to be a late Middle Kingdom copy from an earlier Middle Kingdom original; it is a collection of student’s answers to problems, provided with the teacher’s approval (at times justly refused). The other properly mathematical sources are from the Middle through New Kingdom.3 A source of particular character is the New Kingdom fictional “satirical letter” or Papyrus Anastasi I,4 in which a scribe chides a colleague for his professional ignorance; it shows that a military scribe was supposed to be familiar with Palestinian geography and with the determination of the manpower, rations, and other requirements of construction work. Accounting papyri show that other categories of scribes had analogous tasks. Some administrative records go back to the Old Kingdom (and a few docu- ments containing numbers to the early dynastic period); even in this respect, however, the Middle through New Kingdom is much richer. The mathematical sources of the Pharaonic period are written in hieratic script (evidently, some hieroglyphic documents contain numbers); part of the metrological terminology seems to have been created in hieratic and to have acquired hieroglyphic equivalents only at a later moment (when at all). with in Annette Imhausen, Mathematics in Ancient Egypt: A Contextual History (Princeton & Oxford: Princeton University Press, 2016). 2 Edition with translation and extensive commentary: W. W. Struve, Mathematischer Papyrus des Staatlichen Museums der Schönen Künste in Moskau (Quellen und Studien zur Geschichte der Mathematik. Abteilung A: Quellen, 1. Band; Berlin: Julius Springer, 1930). The edition is reproduced in Marshall Clagett, Ancient Egyptian Science, vol. 3, which also contains an English translation and a commentary. 3 Marshall Clagett, following recent research, gives the following approximate dates (Ancient Egyptian Science. A Source Book. Volume I: Knowledge and Order (Memoirs of the American Philosophical Society, 184 A+B; Philadelphia, PA: American Philosophical Society, 1989), pp. 629–35): Early dynastic period (dynasties 1–2): 3110–2665. Old Kingdom (dynasties 3–8): 2664–2155. First intermediate period (dynasties 9–10): 2154–2052. Middle Kingdom (dynasties 11–13): 2040–1640. Second intermediate period (Hyksos dynasties 15–16, Theban dynasty 17): 1640–1532. New Kingdom (dynasties 18–20): 1550–1070. Third intermediate period (dynasties 21–(initial) 25): 1070–712. Late period (dynasties (final) 25–31, including the Assyrian hegemony during dynasty 26 and the Persian dynasties 27 and 31): 712–332. Greco-Roman period: 332 bce to 395 ce. 4 Full edition and translation in Alan H. Gardiner, Egyptian Hieratic Texts. Series I: Literary Texts from the New Kingdom. Part I: The Papyrus Anastasi I and the Papyrus Koller, together with Parallel Texts (Leipzig: J. C. Hinrichs’sche Buchhandlung, 1911). 146 Jens Høyrup From the demotic phase (late and Greco-Roman periods), several papyri containing mathematical problems and tables survive5 – with the possible exception of one uncertain fragment all of Greco-Roman date. NUMBERS AND METROLOGY The Egyptian number system was decadic. Already in early dynastic times, individual signs for 1, 10, 100, 1,000, 10,000, 100,000, and 1,000,000 existed.6 In hieroglyphic, other numbers were constructed additively, by mere repetition of these signs; in hieratic, thesewerecontractedintoindividualsigns for 1, 2, ...,9,10,20,..., 90, 100, 200, etc. From the Middle Kingdom onward, fractional numbers were expressed as sums of aliquot parts (including two-thirds); in order to keep close to theEgyptiannotationwemaytranscribe ″ 2 ′ 1 ′ 1 1 ″ ′ ′ them as follows: 3 (= /3), 2 (= /2), 3 (= /3), 4(= /4), 5,etc.(3 ,2,and3 had special signs); the others were denoted by the sign ro (“mouth,” here “part”)or by a dot above the number (in hieroglyphic respectively hieratic writing), according to a canon that did not allow repetition of the same aliquot part but expressed for instance 5 5as3′ 15 (juxtaposition means addition). Essential metrologies, however, would operate with subunits instead of these fractions. Many of the problems in the mathematical texts deal with the difficulties to which the non-decadic metrologies would give rise. Closest to decadic principles is the length system. The basic length unit was the “royal cubit” “ ” “fi ” “ ” (mh˙ , c. 52cm), subdivided into 7 palms of 4 ngers each (a short cubit of 6 palms was also in use). 100 royal cubits was a “rope” (khet). Land might be measured in setat (that is, square khet), divided by successive halvings into 1 subunits with special names (down to /32 setat); in surveying practice, the “cubit of land” (1 cubit versus 1 khet) and the “thousand of land” (1,000 cubit versus 1 khet) were mostly preferred. The central capacity unit was the h̩ ek̩ at, divided according to one system into 10 henu or 320 ro (the “part” again, but in a different use), according to another 1 7 by successive halvings (down to /64). Multiples of the h̩ ek̩ at were expressed by special signs or by non-standard use of the standard numerals. A special unit for 2 bulkysubstancesisthekhar,equalto20h̩ ek̩ at and to /3 of a cubic royal cubit (probably a secondary normalization of originally distinct units). 5 Edition with translation and extensive commentary in Richard A. Parker (ed.), Demotic Mathematical Papyri (Providence, RI and London: Brown University Press, 1972). 6 The standard reference for Egyptian numerals and number words remains Kurt Sethe, Von Zahlen und Zahlworten bei den Alten Ägyptern, und was für andere Völker und Sprachen daraus zu lernen ist (Schriften der Wissenschaftlichen Gesellschaft in Straßburg, 25; Straßburg: Karl J. Trübner, 1916). In the second millennium, the sign for 1,000,000, and afterwards that for 100,000, went out of use; instead, multiplicative notations were used. 7 The hieroglyphic signs for the successive halves of the h̩ ek̩ at can be put together to the standard representation of the healing sacred eye of Horus, as pointed out by Peet, The Rhind Mathematical Papyrus,