About advancing of mathematical theories and calculation methods When ancient mathematicians like Aristotle and Euclid made the theories and calculated things like area of circle and triangle, they had only their head, when they made their calculations. The ancient Greeks believed that pi was three, and that information was enough in that time. Pi defined is as the ratio of a circle's circumference to its diameter. That was enough sharp at that time. When Sir Isaac Newton and Gottfried Leibnitz started to work with derivate and integral calculations they had the first mechanical calculator in their use. But when David Hilbert started to work with the errors in the Euclidean geometry, he used only the sharper numbers that Euclid. When we are thinking about the time of Albert Einstein, we must realize that in his time, in the physics was only mechanical calculation machines. In the time of Albert Einstein was not an observation of the black holes, and I don't know how many