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Introduction

String theory is not simply a theory that has emerged within the last decade. This theory has quite an extensive history that has shown periods of promise and dismal times, as well. Because string theory has been developed along with many of the other prominent ideas of the last century, including the Standard Model and quantum mechanics, it has been obscured to the general public for the most part. Now let’s delve into a fascinating look into the birth of string theory.

Kaluza - Klein Theory

Kaluza, while studying Einstein’s Theory of General Relativity, pondered about the consequences of adding a fifth dimension to the accepted four dimensions.

The seeds for string theory in the second half of the twentieth century and beyond were planted in 1919 by Theodor Kaluza, who was working at the University of Konigsberg. Kaluza, while studying Einstein’s Theory of General Relativity, pondered about the consequences of adding a fifth dimension to the accepted four dimensions (three spatial dimensions and one time dimension). When Kaluza included the extra dimension, he discovered that this situation allowed for the unification or gravity and electromagnetism. This was a very significant breakthrough at such an early period; however, when Kaluza submitted his findings to Einstein in 1919, Einstein eventually began to ignore Kaluza’s theory. Although Einstein said, “at first glance I like your theory enormously,” the simple fact that there was no need or reason for this fifth dimension ultimately led to its unimportance for many years.

Later, in 1926, Swedish mathematician Oskar Klein confirmed Kaluza’s work by formulating a quantum theory with Kaluza’s findings. Klein realized that the universe has both “extended” and “curled-up” dimensions. That is, while we can easily seem and detect the extended dimensions, some dimensions are curled-up into such a tiny structure that it is not detectable. Today, Kaluza-Klein theories are defined as those that involve more than four dimensions. Kaluza and Klein’s work was generally disregarded for a long period of time because new forces were being discovered. This meant that the Kaluza-Klein Theory had to be amended for each of these new forces by adding another dimension. Finally, physicists have determined that eleven dimensions are needed to incorporate all of the forces within the Kaluza-Klein Theory. Interestingly, M-theory, which is the most modern and comprehensive version of string theory, demands exactly eleven dimensions. Although the Kaluza-Klein Theory did not prove to actually unite General Relativty and electromagnetism, this theory is still applicable to today’s latest research.

Early Rise

String theory was introduced during the 1960s as a means of working with the strong nuclear force and hadrons, which are particles that are affected by the strong nuclear forces such as neutrons and protons. Despite the initial excitement and work done for about five years hereafter, the field of quantum chromodynamics appeared to deal with this situation better. Then, in 1971, string theory incorporated supersymmetry, and this merger resulted in the creation of superstrings that can exist in ten dimensions. After that, the entire focus of string theory shifted when physicists moved away from the strong force and hadrons and focused instead on quantum gravity. At this point, the modern-day promise of string theory arose because string theory could now be developed to incorporate quantum mechanics and the previously bothersome force of gravity and the corresponding particle – the graviton.

First Revolution

By the end of 1985, there was not one, but rather, five separate string theories that each involved ten dimensions. Interestingly, each of the five theories seemed to be accurate.

The “first revolution” in string theory occurred in 1984 when the theory was proclaimed to be free from anomalies. The work of Green and Schwarz allowed for this significant declaration. However, by the end of 1985, there was not one, but rather, five separate string theories that each involved ten dimensions. Interestingly, each of the five theories seemed to be accurate. This posed as a significant concern until 1994.

Second Revolution

In 1994, the “second revolution” in string theory was born with the work of Seiberg and Professor Edward Witten. They said that these multiple theories, which also included an additional eleven dimensional theory, were simply different versions of the same theory. Known as “M-theory,” this all-in-one theory accounts for the other theories with duality transformations, which somehow connect the different theories together. These two revolutions have brought us to modern day and the excitement of string theory.

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