what is string theory ? string theory is theoretical and it is just like a mathematical tool other than classical physics like a cosmology . string theory suggest that smallest thing in not point particle instead of that it is a string which are one dimensional extended object . as in above fig the whole black part is universe and it is subdivided into small thread or string which is in blue color . small string connect together and make a anything around us . These string propagate through space and interact with each other , such string have charge and mass. they possess a vibration by which it communicate with each other . such vibrational state of the string include ;- 1. Gravition 2. Quantam mechanical particle 3. Gravitational force 1. Gravition; - it is hypothetical or imaginative theory they are expected to be massless it is belived that something like gravitation and spin around space. 2. quantam mechnical particle ;- In last arti