We explain what string theory is in physics, its main hypothesis and its variants. In addition, the controversy over its limitations.

String theory tries to be a "theory for everything."## What is string theory?

String Theory is an attempt to solve one of the great enigmas of contemporary theoretical physics and create a unifying theory of its different fields, that is, a "theory for everything".

This scientific hypothesis and foundational model holds that the material particles that we know, such asconstituent elements of the atom they are actually vibrational states of a "string" or "filament."

String Theory proposes that spacetime has many more dimensions than we can perceive (eleven, to be exact). Therefore, the fundamental "strings" can vibrate in many ways in all these dimensions.

To each mode of vibrating corresponds a fundamental particle: aelectron, a photon, a quark, or any other particle of the standard model. It is a theory that tries to get away from the idea of the point-particle.

Although this theory arose as a way to respond to the contradictions and unsolvable dilemmas of thephysical Contemporary, there are currently five superstring theories. Each is linked with a way of implementing the string model to the theory of supersymmetry, which assumes that for each elementary particle, there exists a supersymmetric companion.

Some of these variant theories are:

- Type I string theory. Consisting of strings and D-branes both open and closed, vibrating in ten-dimensional space-time.
- Type IIA string theory. Consisting of uniquely closed strings and D-branes, along with gravitines.
- Type IIB string theory. It differs from Type IIA in that it is non-chiral (preserving parity).
- Heterotic string theory SO. Also called Heterotic-O, based on the symmetry group O.
- E8xE8 heterotic string theory. Also called Heterotic-E, based on the exceptional Lie group E8.

## String theory controversy

Despite the fact that string theory could explain in an innovative way some of the most challenging physical phenomena of the natureIt also has notable limitations. For example, your math is valid only in a space–weather 11 dimensions.

On the other hand, the predictions made following this model have not been sufficiently concrete to be compared with an experimental model. For many, it is such an ambitious and comprehensive theory that it cannot be scientifically proven or disproved, which is why it has often been accused of pseudoscience.