and rebirth, with each cycle lasting 4,320,000 years.  Hindu  and  Buddhist philosophers  also developed a theory of five  classical elements :  Vayu  (air),  Ap  (water),  Agni  (fire),  Prithvi / Bhumi  (earth) and  Akasha  (aether). In the 6th century BC,  Kanada , founder of the  Vaisheshika  school, developed a theory of  atomism