String theory is a theory which was proposed to combine two totally opposite concepts of physics - General relativity and Quantum mechanics. General Relativity explains the things of large scale and Quantum mechanics explains the things of small scale. The name “string theory “ comes from the single dimensional particles called “strings” which replace the subatomic particles according to the theory. Here the particular way of vibration of these strings are responsible for the subatomic particle characteristics such as charge and mass.

It is being believed by many scientists that this theory could unify and explain all the four nature’s forces-Strong nuclear force, Weak nuclear force, Electromagnetism and Gravity.  It also explains about all types  of matter by bringing it under a single quantum mechanical framework. Even though the theory looks so impressive with its mathematical calculation, it still needs to be experimentally proven to make it a strong and proven theory. 

The Standard model of physics could explain everything but not Gravity. Here’s where the String theory becomes the best theory to supersede the Standard model of Physics. In 1915 Einstein unified Space , time and gravity with his General Relativity theory.  Einstein dreamt of a theory that could unite all the four forces so called an “unified theory”. In contrast, from the 1920s onwards quantum mechanics emerged with a concern, explaining about the quantum level particles not being affected by gravity.

Gabriele Veneziano, a young theorist, made a breakthrough by finding that 200 year old formula - Euler beta function could explain some detailed information about the strong nuclear force. After few years , Leonard Susskind of Stanford University, Holger Nielsen of the Niels Bohr Institute, and Yoichiro Nambu of the University of Chicago added much information that Veneziano’s proposal explained about the vibrational movement of the minuscule filaments of energy which just resembles the strings from where we get the name “String Theory”. 

As explained above, string theory is such an attractive theory in its mathematical way but still its refined measurements of strong force made many scientists of that time to conclude that the string would not support the real universe. But John Schwarz of the California Institute of Technology and Joel Scherk of the École Normale Supérieure and, independently, Tamiaki Yoneya of Hokkaido University came to a radical conclusion. 

They concluded that the massless particles as predicted by string theory could be the way to make Einstein’s dream come true- The Unification theory. Though they concluded and some scientists supported, most of the scientists didn’t agree with the theory and theoretical problems aided this as one ended up with signs being inconsistent and for another ended up with 10 dimensions to complete the mathematical equation. 

By the 1980s only 2 were left dealing with string theory and they were Schwarz and Michael Green of Queen Mary College, London. By 1984, these 2 physicists finally brought up string theory by removing a knot by proving that the string theory is consistent with their equation. This made many scientists to drop down their works and pay attention to string theory.  According to the theory, the strings have a length of about 10^(-33)cm. 

According to string theory, the 3 dimensions which we experience are large and the rest 6 dimensions are so small that they could not be detected. Still this extra-dimension is being a hurdle and is being imagined that they are so small. Their geometry is also required for the theory to predict. The exact shape and size of the extra dimension affects the vibration of strings.  These requirements make it hard to predict the characteristics as it requires geometric knowledge about the dimensions. 

In 1995 , Edward Witten of Institute of Advanced Study rejuvenated string theory by adding a number of new features to the theory. This also included the realization of the 7 dimensions. The more exact equation also explained about the membrane-like structures of various dimensions collectively called the branes.

Finally, theorists all concluded this as an unification of the older versions of string theory and named it as the “M-Theory”. In 1997, Juan Maldacena of Harvard University made another breakthrough by  making a very good tie with quantum field theory and his theory was called the anti-de sitter/conformal field theory(AdS/CFT). This resulted in an even more exact equation of string theory. Even though the theory had been through much enhancive  improvements theoretically, it still needs some observations to prove them strongly.

Supersymmetry is a quality of string, a mathematical property which requires every known particle species to have a partner particle species and hence called as Superpartner. Because of this quality, string theory is sometimes called the Superstring theory. So far no superpartners have been found but scientists believe that’s all because of their increased mass than their counterparts.

And to detect these superpartners, machines such as the Large Hadron Collider(LHC) are the possible ways one could check out. If the superpartner particles are found, string theory still will not be proved correct, because more-conventional point-particle theories have also successfully incorporated supersymmetry into their mathematical structure. However this theory would help us to confirm whether we are on the right track to our Unification theory by giving us indirect evidence. 

However Ads/CFT Correspondences are found to solve the paradoxes of the black hole such as Black Hole information Paradox, applied to theoretical problems of quantum gravity and in condensed matter physics to understand superfluids and superconductors. 

All these end up with one message- We are evolving with better questions and better answers. The more we learn about this universe, the more bizarre it gets, the more questions we get and the more answers we jot in the papers and history. So let’s all keep rocking… 

Hope that this article will give you a very good idea about String theory.

Thank you for reading this article.

Stay tuned with Black Hole of Knowledge!!

Sourced from: www.livescience.com 

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An article by Zandriana