There theory of everythingalso called TOE from English theory of everythingis a physical theory that seeks a physical formulation capable of unify the four fundamental interactions – gravity, electromagnetism, the strong nuclear interaction and the weak nuclear interaction, sometimes incorrectly called “forces” – with the aim of bringing them together in a single conceptual framework and mathematical formalism all physical phenomena of the universe. For this reason, this theory is also known as unified field theory. This theory aims to include and reconcile microscopic phenomena (such as Quantum mechanics) with macroscopic phenomena (such as general relativity by Albert Einstein) which are currently mathematically irreconcilable. Stephen Hawking, a well-known British mathematician, physicist and cosmologist, devoted part of his life to trying to describe everything in a theory. James Marsh’s 2014 film of the same name is about the theory, The theory of everything.
Where does the idea of the theory of everything come from?
When we speak of a theory of everything, we mean a model capable of simultaneously and completely explaining all physical phenomena. This model claims to include the four fundamental interactions of nature: gravitational, electromagnetic, strong nuclear and, finally, weak nuclear. But so far, the description of one of these four – especially gravity – is irreconcilable with the other three.
Gravitational interaction, and in particular the curvature of space-time, is described by Albert Einstein in his work general relativity. On the other hand, the Quantum mechanics it describes well the other three interactions, electromagnetic, strong and weak, but does not include gravity.
Thus was born the idea of trying to unify the description of the universe into a single theory. This theory attempts to explain those physical phenomena of the Universe in which all forces come into play with a similar intensity, and where it is therefore not possible to neglect one or more contributions. This almost never happens on Earth, where we can easily describe physical phenomena by assuming that certain interactions are zero, often three out of four.
The unification of 3 interactions: weak, strong and electromagnetic
The first step was to unify two interactions. In 1967-1968, Sheldon Glashow, Steven Weinberg and Abdus Salam managed to unify the weak nuclear interaction with the electromagnetic interaction, calling it electroweak interaction. This electroweak force, in turn, manages to coexist with the strong nuclear force to form what has been called nuclear power interaction. Gravity, however, remains outside this unification.
The birth of different theories of everything
Many scientists over the past decades have attempted to develop a theory of everything, a coherent and complete set of fundamental laws which explain all aspects of reality with a single formulation. This research resulted in the production of a family of interconnected theories instead of a single theory, and each of these theories attempts to describe a version of reality.
In short, there is no single theory for everything. Over the years, many theoretical physicists have proposed completely different theoriesnone of which, however, has ever been confirmed experimentally.
This idea – difficult to accept even for many scientists – presupposes that reality is not strictly objective. This contrasts with the simplified description of classical science in which the properties of the world are defined and independent of the observer who perceives them.
Some of the most accredited and well-known theories are string theory, M-theory and supergravity.
String theory
The first of them, the string theoryreplaces point particles of ropes, one-dimensional, string-like objects capable of vibrating. These ropes they vibrate differently and define the properties of matter, such as mass and electric charge.
M-theory
From the union of string theory with supersymmetry – a theory according to which each boson (or fermion) corresponds to a second boson (or fermion) of the same mass – the superstring theory. This theory can also describe the behavior of bosons and fermions not included in the previous theory. From the set of 5 different superstring theories comes the M-theory.
Supergravity
There supergravity it is a theory that combines the supersymmetry with the general relativity. This theory includes the gravitonthe particle linked to the gravitational force.
