Quantum gravity
M theory , although mathematically sound, requires another theory to work in tandem with it. This is supersymmetry . Supersymmetry posits that the standard model is extended so that all particles have a supersymmetric counterpart that differ by half a unit of spin. For every boson , there exists a superpartner fermion and vice versa. 18 This already creates massive assumptions regarding the validity of M theory and potentially threatens its collapse if found invalid. Supersymmetry predicted its lowest energy superpartners to exist within the threshold of CERN’s Large Hadron Collider . 19 Even after the discovery of the Higgs Boson in 2012, there remained no evidence to suggest that supersymmetry was correct. 20 M theory studies spatial objects called Dirichlet membranes or D-Branes that form in sheets formed of up to 11 dimensions and are vital for understanding how gravity would work in string theory between small distances. 21 String theory predicts that gravity is the result of a larger quantum field, referred to as supergravity that interacts across the new dimensions introduced by string theory and explains why gravity is so much weaker than other fundamental fields. In addition to this, string theory similarly solves the problem for some singularities by also preventing their size from reaching zero as strings are also restricted to a diameter of the Planck length , thus preventing infinite densities. However, string theory only solves this problem of infinities for certain varieties of black holes. 22 String theory is extremely thorough in its mathematical foundations and is a stronger candidate if regarded solely in terms of its mathematics. However, this also leads to its greatest deficiency. String theory seems to achieve much in its use of abstract spatial objects, but it is currently impossible to validate. Both theories discussed lead to huge changes in our understanding of gravity, cosmology and particle physics. Both lead to such mathematical abstraction of space that they completely change the fundamental building blocks of space and matter. Yet, I believe that loop quantum gravity is currently the more believable theory of quantum gravity. This is due to its compelling simplicity compared to string theory, as it maintains the same framework of quantum mechanics while also introducing the identical spacetime from general relativity. Although string theory does not currently provide the most compelling theory of gravity, I am sure that its development in mathematics will lead to a more successful theory of everything in the future.
Bibliography
Article
Bergeron, L. (2009). Stanford researchers: Gamma-ray photon race ends in dead heat; Einstein wins this round . [online] Stanford University. Available at: https://news.stanford.edu/news/2009/october26/fermi-telescope- discovery-102809.html.
18 See An Introduction to String Theory (2011): 8-9; Introduction to M Theory (1998): 4-6. 19 The Large Hadron Collider collides protons together at such high speeds that it creates new higher energy particles. The Large Hadron Collider has been able to detect the Higgs Boson at a mass of 125 GeV while Supersymmetry should predict the detectable mass to be lower due to the Higgs interaction with other particles, which has shown to be false. 20 Covariant Loop Quantum Gravity: An elementary introduction to Quantum Gravity and Spinfoam Theory (2014): 3. 21 See Introduction to M Theory (1998): 2-4. 22 See An Introduction to String Theory (2011): 250-254; Introduction to M Theory (1998): 3, 10-12.
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