The Britannica Guide to The History of Mathematics

Britannica Educational Publishing, Erik Gregersen

• Verlag: Britannica Educational Publishing
• Jahr: 2010
• ISBN:
  9781615302215
• Thema: Matematica
• Thema: Storia e filosofia della matematica

The field of mathematics today represents an ongoing global effort, spanning both countries and centuries. Through this in-depth narrative, students will learn how major mathematical concepts were first derived, as well as how they evolved with the advent of later thinkers shedding new light on various applications. Everything from Euclidean geometry to the philosophy of mathematics is illuminated as readers are transported to the ancient civilizations of Mesopotamia, Egypt, and beyond to discover the history of mathematical thought

CHAPTER 1
ANCIENT WESTERN MATHEMATICS

Mathematics is the science of structure, order, and relation that has evolved from elemental practices of counting, measuring, and describing the shapes of objects. It deals with logical reasoning and quantitative calculation, and its development has involved an increasing degree of idealization and abstraction of its subject matter. Since the 17th century, mathematics has been an indispensable adjunct to the physical sciences and technology, and in more recent times it has assumed a similar role in the quantitative aspects of the life sciences.

In many cultures—under the stimulus of the needs of practical pursuits, such as commerce and agriculture—mathematics has developed far beyond basic counting. This growth has been greatest in societies complex enough to sustain these activities and to provide leisure for contemplation and the opportunity to build on the achievements of earlier mathematicians.

All mathematical systems (for example, Euclidean geometry) are combinations of sets of axioms and of theorems that can be logically deduced from the axioms. Inquiries into the logical and philosophical basis of mathematics reduce to questions of whether the axioms of a given system ensure its completeness and its consistency.

As a consequence of the exponential growth of science, most mathematics has developed since the 15th century CE. This does not mean, however, that earlier developments have been unimportant. Indeed, to understand the history of modern mathematics, it is necessary to know its history at least in Mesopotamia and Egypt, in ancient Greece, and in Islamic civilization from the 9th to the 15th century. These civilizations influenced one another and Greek and Islamic civilization made important direct contributions to later developments. For example, India’s contributions to the development of contemporary mathematics were made through the considerable influence of Indian achievements on Islamic mathematics during its formative years.

ANCIENT MATHEMATICAL SOURCES

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It is important to be aware of the character of the sources for the study of the history of mathematics. The history of Mesopotamian and Egyptian mathematics is based on the extant original documents written by scribes. Although in the case of Egypt these documents are few, they are all of a type and leave little doubt that Egyptian mathematics was, on the whole, elementary and profoundly practical in its orientation. For Mesopotamian mathematics, on the other hand, there are a large number of clay tablets, which reveal mathematical achievements of a much higher order than those of the Egyptians. The tablets indicate that the Mesopotamians had a great deal of remarkable mathematical knowledge, although they offer no evidence that this knowledge was organized into a deductive system. Future research may reveal more about the early development of mathematics in Mesopotamia or about its influence on Greek mathematics, but it seems likely that this picture of Mesopotamian mathematics will stand.

From the period before Alexander the Great, no Greek mathematical documents have been preserved except for fragmentary paraphrases, and, even for the subsequent period, it is well to remember that the oldest copies of Euclid’s Elements are in Byzantine manuscripts dating from the 10th century CE. This stands in complete contrast to the situation described above for Egyptian and Babylonian documents. Although in general outline the present account of Greek mathematics is secure, in such important matters as the origin of the axiomatic method, the pre-Euclidean theory of ratios, and the discovery of the conic sections, historians have given competing accounts based on fragmentary texts, quotations of early writings culled from nonmathematical sources, and a considerable amount of conjecture.

Many important treatises from the early period of Islamic mathematics have not survived or have survived only in Latin translations, so that there are still many unanswered questions about the relationship between early Islamic mathematics and the mathematics of Greece and India. In addition, the amount of surviving material from later centuries is so large in comparison with that which has been studied that it is not yet possible to offer any sure judgment of what later Islamic mathematics did not contain, and therefore it is not yet possible to evaluate with any assurance what was original in European mathematics from the 11th to the 15th century.

MATHEMATICS IN ANCIENT MESOPOTAMIA

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Until the 1920s it was commonly supposed that mathematics had its birth among the ancient Greeks. What was known of earlier traditions, such as the Egyptian as represented by the Rhind papyrus (edited for the first time only in 1877), offered at best a meagre precedent. This impression gave way to a very different view as Orientalists succeeded in deciphering and interpreting the technical materials from ancient Mesopotamia.

Owing to the durability of the Mesopotamian scribes’ clay tablets, the surviving evidence of this culture is substantial. Existing specimens of mathematics represent all the major eras—the Sumerian kingdoms of the 3rd millennium BCE, the Akkadian and Babylonian regimes (2nd millennium), and the empires of the Assyrians (early 1st millennium), Persians (6th through 4th centuries BCE), and Greeks (3rd century BCE to 1st century CE). The level of competence was already high as early as the Old Babylonian dynasty, the time of the lawgiver-king Hammurabi (c. 18th century BCE), but after that there were few notable advances. The application of mathematics to astronomy, however, flourished during the Persian and Seleucid (Greek) periods.

THE NUMERAL SYSTEM AND ARITHMETIC OPERATIONS

Unlike the Egyptians, the mathematicians of the Old Babylonian period went far beyond the immediate challenges of their official accounting duties. For example, they introduced a versatile numeral system, which, like the modern system, exploited the notion of place value, and they developed computational methods that took advantage of this means of expressing numbers. They also solved linear and quadratic problems by methods much like those now used in algebra. Their success with the study of what are now called Pythagorean number triples was a remarkable feat in number theory. The scribes who made such discoveries must have believed mathematics to be worthy of study in its own right, not just as a practical tool.

The older Sumerian system of numerals followed an additive decimal (base-10) principle similar to that of the Egyptians. But the Old Babylonian system converted this into a place-value system with the base of 60 (sexagesimal). The reasons for the choice of 60 are obscure, but one good mathematical reason might have been the existence of so many divisors (2, 3, 4, and 5, and some multiples) of the base, which would have greatly facilitated the operation of division. For numbers from 1 to 59, the symbols

for 1 and

for 10 were combined in the simple additive manner (e.g.,

represented 32). But, to express larger values, the Babylonians applied the concept of place value: for example, 60 was written as

, 70 as

, 80 as

, and so on. In fact,

could represent any power of 60. The context determined which power was intended. The Babylonians appear to have developed a placeholder symbol that functioned as a zero by the 3rd century BCE, but its precise meaning and use is still uncertain. Furthermore, they had no mark to separate numbers into integral and fractional parts (as with the modern decimal point). Thus, the three-place numeral 3 7 30 could represent 3⅛ (i.e., 3 + 7/60 + 30/60²), 187 ½ (i.e., 3 × 60 + 7 + 30/60), 11,250 (i.e., 3 × 60² + 7 × 60 + 30), or a multiple of these numbers by any power of 60.

The four arithmetic operations were performed in the same way as in the modern decimal system, except that carrying occurred whenever a sum reached 60 rather than 10. Multiplication was facilitated by means of tables; one typical tablet lists the multiples of a number by 1, 2, 3,…, 19, 20, 30, 40, and 50. To multiply two numbers several places long, the scribe first broke the problem down into several multiplications, each by a one-place number, and then looked up the value of each product in the appropriate tables. He found the answer to the problem by adding up these intermediate results. These tables also assisted in division, for the values that head them were all reciprocals of regular numbers.

Regular numbers are those whose prime factors divide the base. The reciprocals of such numbers thus have only a finite number of places (by contrast, the reciprocals of nonregular numbers produce an infinitely repeating numeral). In base 10, for example, only numbers with factors of 2 and 5 (e.g., 8 or 50) are regular, and the reciprocals (1/8 = 0.125, 1/50 = 0.02) have finite expressions; but the reciprocals of other numbers (such as 3 and 7) repeat infinitely (0.3 and 0.142857, respectively, where the bar indicates the digits that continually repeat). In base 60, only numbers with factors of 2, 3, and 5 are regular. For example, 6 and 54 are regular, so that their reciprocals (10 and 1 6 40) are finite. The entries in the multiplication table for 1 6 40 are thus simultaneously multiples of its reciprocal 1/54. To divide a number by any regular number, then, one can consult the table of multiples for its reciprocal.

Babylonian mathematical tablet. Yale Babylonian Collection

An interesting tablet in the collection of Yale University shows a square with its diagonals. On one side is written “30,” under one diagonal “42 25 35,” and right along the same diagonal “1 24 51 10” (i.e., 1 + 24/60 + 51/60² + 10/60³). This third number is the correct value of

to four sexagesimal places (equivalent in the decimal system to 1.414213…, which is too low by only 1 in the seventh place), while the second number is the product of the third number and the first and so gives the length of the diagonal when the side is 30. The scribe thus appears to have known an equivalent of the familiar long method of finding square roots. An additional element of sophistication is that, by choosing 30 (that is, 1/2) for the side, the scribe obtained as the diagonal the reciprocal of the value of

(since

/2 = 1/

), a result useful for purposes of division.

GEOMETRIC AND ALGEBRAIC PROBLEMS

In a Babylonian tablet now in Berlin, the diagonal of a rectangle of sides 40 and 10 is solved as 40 + 10²/(2 × 40). Here a very effective approximating rule is being used (that the square root of the sum of a² + b² can be estimated as a + b²/2a), the same rule found frequently in later Greek geometric writings. Both these examples for roots illustrate the Babylonians’ arithmetic approach in geometry. They also show that the Babylonians were aware of the relation between the hypotenuse and the two legs of a right triangle (now commonly known as the Pythagorean theorem) more than a thousand years before the Greeks used it.

A type of problem that occurs frequently in the Babylonian tablets seeks the base and height of a rectangle, where their product and sum have specified values. From the given information the scribe worked out the difference, since (b − h)² = (b + h)² − 4bh. In the same way, if the product and difference were given, the sum could be found. And, once both the sum and difference were known, each side could be determined, for 2b = (b + h) + (b − h) and 2h = (b + h) − (b − h). This procedure is equivalent to a solution of the general quadratic in one unknown. In some places, however, the Babylonian scribes solved quadratic problems in terms of a single unknown, just as would now be done by means of the quadratic formula.

Although these Babylonian quadratic procedures have often been described as the earliest appearance of algebra, there are important distinctions. The scribes lacked an algebraic symbolism. Although they must certainly have understood that their solution procedures were general, they always presented them in terms of particular cases, rather than as the working through of general formulas and identities. They thus lacked the means for presenting general derivations and proofs of their solution procedures. Their use of sequential procedures rather than formulas, however, is less likely to detract from an evaluation of their effort now that algorithmic methods much like theirs have become commonplace through the development of computers.

As mentioned above, the Babylonian scribes knew that the base (b), height (h), and diagonal (d) of a rectangle satisfy the relation b² + h² = d². If one selects values...

Inhaltsverzeichnis

• Cover Page
• Title Page
• Copyright Page
• Contents
• Introduction
• Chapter 1: Ancient Western Mathematics
• Chapter 2: European Mathematics Since the Middle Ages
• Chapter 3: South and East Asian Mathematics
• Chapter 4: The Foundations of Mathematics
• Chapter 5: The Philosophy of Mathematics
• Glossary
• Bibliography
• Index