Imagining Numbers: (particularly the square root of minus fifteen) [Hardcover]

Barry Mazur (Author)

Book Description

ISBN-10: 0374174695 | ISBN-13: 978-0374174699 | Publication Date: 2003

How the elusive imaginary number was first imagined, and how to imagine it yourself

Imagining Numbers (particularly the square root of minus fifteen) is Barry Mazur's invitation to those who take delight in the imaginative work of reading poetry, but may have no background in math, to make a leap of the imagination in mathematics. Imaginary numbers entered into mathematics in sixteenth-century Italy and were used with immediate success, but nevertheless presented an intriguing challenge to the imagination. It took more than two hundred years for mathematicians to discover a satisfactory way of "imagining" these numbers.

With discussions about how we comprehend ideas both in poetry and in mathematics, Mazur reviews some of the writings of the earliest explorers of these elusive figures, such as Rafael Bombelli, an engineer who spent most of his life draining the swamps of Tuscany and who in his spare moments composed his great treatise "L'Algebra". Mazur encourages his readers to share the early bafflement of these Renaissance thinkers. Then he shows us, step by step, how to begin imagining, ourselves, imaginary numbers.

Editorial Reviews

From Scientific American

Mazur, a mathematician and university professor at Harvard University, writes "for people who have no training in mathematics and who may not have actively thought about mathematics since high school, or even during it, but who may wish to experience an act of mathematical imagining and to consider how such an experience compares with the imaginative work involved in reading and understanding a phrase in a poem." It is a stimulating and challenging journey, one likely to lead the reader to share Mazur's view: "The great glory of mathematics is its durative nature; that it is one of humankind's longest conversations; that it never finishes by answering some questions and taking a bow. Rather, mathematics views its most cherished answers only as springboards to deeper questions."

Editors of Scientific American

Review

"A clear, accessible, beautifully written introduction not only to imaginary numbers, but to the role of imagination in mathematics."
-George Lakoff, Professor of Linguistics, University of California, Berkeley

"This absorbing and in itself most imaginative book lies in the grand tradition of explanations of what mathematical imagination is--such as those of Hogben, Kasner and Newman, and Polya's How to Solve It. But it is unique in its understanding of and appeal to poetic thought and its analogues, and will appeal particularly to lovers of literature."
-John Hollander

"A very compelling, thought-provoking, and even drmataic description of what it means to think mathematically."
-Joseph Dauben, Professor of History and History of Science, City University of New York

"Barry Mazur’s Imagining Numbers is quite literally a charming book; it has brought even me, in a dazed state, to the brink of mathematical play."
-Richard Wilbur, author of Mayflies: New Poems and Translations

See all Editorial Reviews

Product Details

• Hardcover: 270 pages
• Publisher: Farrar, Straus and Giroux (2003)
• Language: English
• ISBN-10: 0374174695
• ISBN-13: 978-0374174699
• Product Dimensions: 7.6 x 5.2 x 1 inches
• Shipping Weight: 11.2 ounces
• Average Customer Review: 3.2 out of 5 stars  See all reviews (18 customer reviews)
• Amazon Best Sellers Rank: #549,052 in Books (See Top 100 in Books)

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Customer Reviews

Most Helpful Customer Reviews

26 of 29 people found the following review helpful:

5.0 out of 5 stars Not for math geeks, April 6, 2003

By A Customer

This review is from: Imagining Numbers: (particularly the square root of minus fifteen) (Hardcover)

This isn't a book for people whose sole focus is mathematics. In fact, it's a book for those who are interested in the imagination and all of its works: poems, novels, paintings, music, and yes, mathematical concepts and ideas. The central question of the book is simply "what happens when we imagine something?" By way of shedding some light on that question, Mazur explores the slow, tentative process by which mathematicians came to feel that they had an adequate picture of what such a number as the square root of -15 actually is.

There is a lot of good history of mathematics here. Mazur has done his homework, and at times he departs from the received wisdom among historians because his reading of the primary sources has convinced him otherwise. He displays his erudition as lightly as possible, however, which makes it easy to miss the fact that some of the interpretations are in fact novel. Folks interested in the history of how complex numbers came to be accepted as honest-to-goodness numbers should definitely read this book.

And finally, this is a book that gives us a chance to see a great mind in action. It feels as if we have been invited to the author's house and we are sharing in a relaxed and rambling after-dinner conversation in which Mazur, one of the world's greatest living mathematicians, explains to his guests how it is that imagining numbers is like imagining the yellow of a tulip. Anyone in his right mind, had they a chance to actually go to Mazur's house and have this conversation, would be crazy to miss the opportunity. We can't have Mazur in person, but here he is on the page, and it's a pleasure to get to know him.

17 of 20 people found the following review helpful:

5.0 out of 5 stars Not So Imaginary Numbers, June 20, 2003

By 

R. Hardy "Rob Hardy" (Columbus, Mississippi USA) - See all my reviews
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This review is from: Imagining Numbers: (particularly the square root of minus fifteen) (Hardcover)

Pythagoras is supposed to have said that all things are numbers, and from his time onwards, people have found that mathematics has been surprisingly supple and fitting in explaining the physical universe. If something is mathematically true, then it is among the most trustworthy concepts we can count on in this uncertain world. Yet mathematicians have had to incorporate more inclusive number systems, some of which they have originally found intimidating or even revolting. In Imagining Numbers (particularly the square root of minus fifteen) (Farrar, Straus, and Giroux), Harvard mathematician Barry Mazur has given a poetic and absorbing illustration of what it is to imagine mathematically. It isn't a book for mathematicians, but it has wonderful ideas about mathematics and what it is that mathematicians spend their time doing. Readers will need to do a few calculations, but mercifully few; the endnotes sometimes take a stronger mathematical background, but the actual mathematics within the text is unintimidating.

Some numbers just seem to be part of us; even babies seem to know the small ones. But big ones, or fractions, or irrationals, take a bit of imagination to understand. When negative numbers were discovered (or invented), mathematicians could use them practically in calculations, even though they were originally called _fictae_ or fictions. But the square root of a negative number doesn't make much intuitive sense. Think of a square with an area of negative nine; it then has a side equal to the square root of negative nine, which isn't three or negative three. Mazur explains, "This has more the ring of a Zen koan than of a question amenable to a quantitative answer." The square roots of negative numbers would not stay impractical like a Zen koan, however. By the 1700s, mathematicians were solving equations that called for such numbers as answers. René Descartes dismissed them by terming them "imaginary numbers," and the name has stuck, even though they are really no more imaginary than negative numbers or irrationals. Mazur does not mention that these less-than-real, more-than-real numbers have been put to practical work in the real world; they have proved unimaginary enough to be useful in understanding electrical circuits, signal processing, and holography. The complex plane, with real numbers along the horizontal axis and imaginary ones on the vertical (beautifully developed here), is where the Mandlebrot set resides, producing all the resultant hallucinatory colors of pictures of fractals.

Mazur has given a history of the idea of imaginary numbers, but he has also tried to explain mathematical imagination in general. He uses many examples from poetry and literature, so a reader who does not know numbers but has some idea about literary images will feel at home. Literary analogies abound here, and Mazur winds up comparing them to mathematical analogies, such as how an algebraic context throws light on a geometric one. Deep structural analogies have always brought impressive understanding in diverse mathematical fields, as mathematicians have striven to make the analogies into equalities. Readers who stick to Mazur's rich and happy exposition may not start using imaginary numbers practically, but they will gain insight into just why Mazur loves doing mathematics and how imagination can be extended in to previously forbidding numerical territory.

12 of 15 people found the following review helpful:

3.0 out of 5 stars A disjointed book, July 31, 2003

By 

Dan Taflin (Seattle, WA USA) - See all my reviews

This review is from: Imagining Numbers: (particularly the square root of minus fifteen) (Hardcover)

I read this book during the leisure time of a vacation, when I could have spent hours on tangents if the situation called for it. In fact, I did take the time to do some of the calculations suggested in the text. Unfortunately, despite its moments of brilliance, I did not find the book in general suitable for leisurely contemplation, but found myself racing toward the conclusion and both relieved and disappointed when I reached it.

Mazur is trying very hard to reach the liberal arts audience. To that end, he throws in piles of philosophical speculations, with copious references to classical works. That in itself is not a fault; but the execution of it is awkward. He slavishly alternates mathematical teaching with philosophical speculation, thus destroying any sense of continuity in the narrative. I found myself skipping the "liberal arts" portions so I could continue the thread of mathematical reasoning without interruption.

He is at his best when he introduces the complex plane. Its connection with rotation is beautifully made, and is the one piece of "new" information I took from the book. I wish he had emphasized more the "Fundamental Theorem of Algebra," which shows how inclusion of imaginary numbers completes the theory of solutions of algebraic equations, but I won't quibble about that.

In the end, I must conclude that Mazur's goal of helping us imagine what must have been in the minds of the inventors/discoverers of imaginary numbers is a failure. Less philosophy and more history would have been a better path to that end. I would love to read what mathematicians themselves were thinking and saying about this new theory as it was being developed, but there is precious little of that.