Robert Kaplan and Ellen Kaplan

Harvard Book Store is delighted to welcome husband-and-wife mathematics education team ROBERT KAPLAN and ELLEN KAPLAN as they reveal the wonder of one of geometry's simplest equations and discuss their new book, Hidden Harmonies: The Lives and Times of the Pythagorean Theorem.

a² + b² = c². It sounds simple, doesn't it? Yet this familiar equation is a gateway into the riotous garden of mathematics, and sends us on a journey of exploration in the company of two inspired guides, authors and teachers Robert and Ellen Kaplan. They trace the life of the Pythagorean Theorem, from ancient Babylon to the present, visiting along the way Leonardo da Vinci, Albert Einstein, President James Garfield, and the Freemasons—not to mention the elusive Pythagoras himself, who almost certainly did not make the statement that bears his name.

How can a theorem have more than one proof? Why does this one have more than two hundred—or is it four thousand? The Pythagorean Theorem has even more applications than proofs: Ancient Egyptians used it for surveying property lines, and today astronomers call on it to measure the distance between stars. Its generalizations are stunning—the theorem works even with shapes on the sides that aren't squares, and not just in two dimensions, but any number you like. And perhaps its most intriguing feature of all, this tidy equation opened the door to the world of irrational numbers, an untidy discovery that deeply troubled Pythagoras's disciples.

"It's clear that this theorem continues to play an important role in math and science, that the human capacity for theoretical exploration remains unabated and that our 'curiosity always seeks to justify the peculiar, and imagination to shape a deeper unity.' As such, this engaging history of the elegantly simple theorem provides readers with much more to ponder than just the mathematical." —Kirkus Reviews