The square root of two was was found way back in 1800 BC. A Babylonian Clay Tablet was found to have the first few digits of the square root of two. Some of the first digits are 1.4142135623730950488016. The square root of two is non-terminating and non-repeating which causes it to become a irrational number. It was also one of the first number to be found in mathematics that is known to be irrational. This number is special because it is also known as the hypotenuse a.k.a the length of a diagonal square.