Question

This chapter goes through an overview of one of the leading smallest size theories - superstring theory. But is it a scientific theory? What issues in physics does it address better than other theories? What do you understand about the ten dimensions the theory requires? How do they fit into our observed reality? What is a particle according to this theory? How do different particles differ from each other? How are they related to each other?

Answer 1

So far no experimental evidence of supersymmetric particles has been observed by particle accelerators on which the theory is based. But the theory is derived from mathematics and physics that follow the scientific process. It remains to be seen if we observe any supersymmetric particle in the future. This is scientific theory but can only be validated by any an experimental observation and if it does not in the foreseeable future then it's not a scientific theory.

Superstring theory accounts for both fermions and bosons and incorporates supersymmetry to model gravity unline other string theories like bosonic string theory. The biggest problem in theoretical physics is combining the theory of general relativity(which explains large stuff) with quantum mechanics(explaining the smallest stuff). Thus string theory tries to do that i.e. to come up with a quantum gravity theory.

We can only sense the 3-dimensional world but string theory requires for its own internal consistencies that the spacetime should be 10 dimensions where either the rest dimensions are compactified in small length scales or we are part of smaller subpart with 3-dimensional world called submanifold.

A particle is a vibrational state of a string that gives its mass, change and other properties thus its the vibrational state of the string would determine the type of particle and is different for different particles.