Bellos - Alexs Adventures in Numberland

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A group of eight divinities in the Indian epic the Mahabharata.

The mathematical constant e is an irrational number beginning 2.718281828, which Gregory Chudnovsky calls twice Tolstoy since the Russian novelist was born in 1828. It has no relation to Einsteins equation E=mc 2, where E means energy.

In the original, the spelt figure is mistakenly written 2301.

Egyptian unit of volume.

Using the convention that 00 = 1, since if 00 = 0 the number would collapse immediately.

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You might think that lines of latitude are parallel to the equator. This is not true because the lines of latitude (with the exception of the equator) are not straight lines, and only straight lines can be parallel to each other. A straight line is the shortest distance between two points, which is why a plane flying between New York and Madrid, which are both on the same line of latitude, does not fly along the line of latitude but instead has a path that looks curved when seen on a two-dimensional map.

Soroban champion Yuzan Araki, aged eight, with trophy and medals. I like to calculate fast,' he said.

Yuji Miyamoto, the inventor of Flash Anzan, and his youngest class of soroban pupils. (Seepp. 68-75.)

BOOK I. PROP. XLVII THEOR.

Pythagoras's theorem from Oliver Byrne's remarkable 1847 version of Euclid'sThe Elements, in which the propositions are expressed using blocks of colour. (Seep. 97.)

An origami scorpion and its crease pattern, created by former NASA physicist Robert Lang. (See p. 108.)

Islamic geometers covered their holy sites with sophisticated tile patterns, like this mosaic from the Alhambra palace in Granada. The ever-repeating patterns were representations of how God reveals himself through mathematical forms. (Seepp. 98-9.)

A Latin square at Rothamsted Research Farm in Harpenden. Six chemical treatments are arranged so that each row and column has one square of each treatment. (Seep. 224.)

Modern-day Pythagorean Jerome Carter and his wife Pamela, outside their dream home in Scottsdale, Arizona (seepp. 779). He has advised hip-hop royalty on the numbers behind their names.

The Shankaracharya of Puri, right, sitting on his throne, next to his chief disciple and interpreter. A picture of Shankara is on the wall behind. (Seepp. 1339.)

Contestants limbering up at the Mental Calculation World Cup (seep. 145). German Jan van Koningsveld, in the foreground, won the square root and calendar calculation rounds.

Pi men: brothers Gregory and David Chudnovsky, left and right, with their collaborator Tom Morgan, centre. They built a supercomputer in Gregory's New York apartment that calculated pi to more than two billion decimal places. (See pp. 1659.)

At the height of the 1818 tangram puzzle craze, these cards were produced in France. The figures of Henry IV, the Young man, Cateau and the Chinese man were to be assembled from the seven geometrical pieces.

OPPOSITE The tangram-style trench patience game, played (and partly designed) by German soldiers in the First World War. (See pp. 2302.)

Erik Demaine, computer scientist (see pp. 108 and2423).

Ivan Moscovich, puzzlist (see pp. 2456).

Raymond Smullyan, logician (see pp. 86 and 245).

Neil Sloane, sequence supremo (seepp. 25565).

The four men above were all guests at the 2008 Gathering for Gardner in Atlanta, an event that celebrates the work of Martin Gardner, the king of recreational mathematics (seepp.24353). Gardner, pictured right at his home in Oklahoma, still works standing up at his wooden desk.

Claw blimey! Eddy Levin with his golden mean gauge in his garden in north London. He found phi in a flower, and also a peacock feather. (See pp. 283301.)