The heart of what became string theory began in the early 20th century and then got jumbled in with a lot of philosophical ideas - 'what if there are dimensions we can't see?' A fifth dimension was a nice discussion, but without being detected it was just that. As the century moved on, Kaluza-Klein theory, S-matrix theory, everyone kept coming up with new stuff and it all eventually became what we now know as String Theory.
The problem has always been that there is no way to validate any of it - it is only a theory in the sense that it uses Theory as a proper name. A team of researchers have flipped that problem around so that string theory doesn't need to be validated, they will instead use string theory to validate quantum mechanics. Beliefs meet the science topology that exists and declare themselves the explanation.
While this latest repurposing, M-theory, has only been given a lukewarm reception outside the community that has been funded to think about M-theory, the authors of a new paper in Physics Letters believe it is the basis of all physics.
"This could solve the mystery of where quantum mechanics comes from," says Professor Itzhak Bars of the University of Southern California, lead author of the paper. He and graduate student Dmitry Rychkov used math to show that a set of fundamental quantum mechanical principles known as "commutation rules'' may be derived from the geometry of strings joining and splitting.
"Our argument can be presented in bare bones in a hugely simplified mathematical structure," Bars said. "The essential ingredient is the assumption that all matter is made up of strings and that the only possible interaction is joining/splitting as specified in their version of string field theory."
Physicists have long sought to unite quantum mechanics and general relativity, and to explain why both work in their respective domains. If it had been shown to be true, string theory would have resolved inconsistencies of quantum gravity and suggested that the fundamental unit of matter was a tiny string, not a particle, and that the only possible interactions of matter are strings either joining or splitting.
Four decades later, proponents in that area of theoretical physic are still trying to hash out the rules of string theory, which seem to demand some interesting starting conditions to work - like extra dimensions, which are necessary to explain why quarks and leptons have electric charge, color and "flavor" that distinguish them from one another.
A Theory of Everything still eludes us. On larger scales, scientists use classical, Newtonian mechanics to describe how gravity holds the moon in its orbit or why the force of a jet engine propels a jet forward. Newtonian mechanics is intuitive and can often be observed with the naked eye. But that does not apply at the really large scale, it is why there is talk of Dark Matter and Dark Energy. On incredibly tiny scales, such as 100 million times smaller than an atom, relativistic quantum field theory describes the interactions of subatomic particles and the forces that hold quarks and leptons together inside protons, neutrons, nuclei and atoms but that does not explain everything, like how particles to be in two places at once.
Still, quantum mechanics is extremely successful as a model for how things work on small scales, but it contains a big mystery: the unexplained foundational quantum commutation rules that predict uncertainty in the position and momentum of every point in the universe.
"The commutation rules don't have an explanation from a more fundamental perspective, but have been experimentally verified down to the smallest distances probed by the most powerful accelerators. Clearly the rules are correct, but they beg for an explanation of their origins in some physical phenomena that are even deeper," Bars said.
The difficulty lies in the fact that there's no experimental data on the topic — testing things on such a small scale is currently beyond a scientist's technological ability.
So M-theory remains conjecture. The safe bet remains that if Michio Kaku embraces it, it is okay to disregard it.