A conundrum faced ancient mathematicians. Which number to use for the square root of 2? Ancient Babylonians used the fraction 305470/216000. This was accurate to about six decimal places. Ancient Indians used the fraction 577/408. This fraction is accurate to five decimal places. Today, mathematicians understand that the square root of 2 is irrational, its digits go on forever without repeating. It is calculated using an infinite series. This book lists the first million digits of the square root of 2.