Motley string or from 10 to 4

Abstract

In 1926 O. Klein proposed [5] that extra spacial dimension in Kaluza theory got curled up in a circle of small radius (aka "compactified"). Same idea applied to Superstring theory means that some spacial dimensions (6) are compactified, while others (3) are not, which leaves unanswered question why some dimensions are better then others. Also it implies the existence of standing waves in compactified dimensions (so called Kaluza-Klein tower) which are not observed experimentally.