Over at backreaction, a video was made discussing the pros and cons of string theory. As stated in the video, string theory was first proposed (in the late 60's) as a theory to describe the nuclear force. String theory didn't fare so well as such, but was regarded as promising by luminaries such as Nobel prize winner Murray Gell-Mann, who offered John Schwarz and his colleagues funding to keep researching the theory at Caltech, Pasadena, CA. With time, string theory became better suited as a unified theory of all forces and particles and is studied at all major universities around the world.

Note: Schwarz is still at Caltech, and holds promise for the future of string theory, and its modern incarnation M-theory.

Let's start with the pros of string theory:

- It extended the study of quantum field theory beyond the mere study of point particles. This brought conformal transformations to the forefront of scattering amplitude calculations.
- The theory of vertex operator algebras, now a prominent branch of mathematics, came from the original "dual resonance model", the first version of string theory.
- Closed strings naturally give a graviton, which along with open strings, can provide a means to unify gravity with the other fundamental forces.
- Compactifications of D=10 string theory on Calabi-Yau spaces brought a deeper understanding in mathematics, giving a way to relate such spaces via mirror symmetry.
- The mysterious Monster group, the largest of the sporadic groups, was found to act as the symmetry of a certain vertex operator algebra for string theory on a 24-torus.
- M-theory as a matrix theory and D-branes with their noncommutative coordinates, have helped give a deeper understanding of noncommutative geometry, which is a branch of mathematics that asserts that operator algebras can be used to generate the quantum analog of smooth manifolds.
- M-theory was shown in the late 90's to reduce to 11-dimensional supergravity, a theory Stephen Hawking once considered the most exciting candidate for a unified theory.

- There are vastly many ways to reduce to four spacetime dimensions from D=10 (or D=11in the case of M-theory). The space of possible compactifications is called the landscape.
- String theory natural enjoys supersymmetry, and one must break supersymmetry to recover the standard model of particle physics we observe at accelerators.
- It has proven experimentally difficult to verify string theory, as most of the structure of models is to be found at extremely high energies.
- After the introduction of M-theory by Edward Witten, the 11-dimensional model has yet to take a final form. The deep structure of M-theory remains a mystery.