For the past century physicists have been trying to formulate a theory to unify all known laws of physics into a single equation to describe the behaviour of the universe. Obviously, one can imagine that this is not the easiest task so the question may be asked; why would we need to do this? Well, simplicity has always been a matter of taste; however, a single theory could mean that we would be able to predict certain future aspects of the universe much more easily. Currently, there appears to be nothing wrong with our notion of physics but having both a classical and quantum way of looking at events which are often contradictory is unsatisfying. This is where physicists started to build a unified theory called the M-theory. The ‘M’ is generally believed to stand for membrane, although, propositions such as magic, mother and master are widely accepted.
The M-theory can be described as a collection of different theories, each of which is a good description of a situation within a certain physical range. Wherever they overlap they predict the same phenomena and this family of theories can be considered as different aspects of the M-theory. It is analogous to maps placed together where certain parts of the maps overlap in order to produce a very accurate representation of the geography of our planet. We all know that the usual Mercator projection maps of the Earth become quite distorted as you move away from the equator. So just like there is no single flat map that can precisely show the surface of the Earth, there is no one formula that can sum the behavior of the universe.
The chronology of how physics has evolved started with classical theories in which the universe has a single history. As physics progressed quantum theories were introduced to account for the behavior of microscopic particles. In quantum physics a system doesn’t have one history but every possible history. The next step to a unified theory was to create quantum versions of the classical theories.
Electromagnetism was the first of the four classical forces (electromagnetism, weak nuclear, strong nuclear and gravity) to be used in a quantum field theory and later the weak nuclear forces were unified with electromagnetism forming the electroweak forces. The problem with the strong forces was that they could not be unified with the electroweak ones and also a quantum field theory for gravity could not be made.
In 1976 a field theory of gravity called ‘supergravity’ was proposed and in 1984 a new theory called the string theory became popular among scientists. The string theory is a framework that includes all known forces and ten dimensions. We don’t observe all of them because some are curled up into something known as internal space which can be curved in millions of different ways, each of which has its own values of the physical constants and different behaviors of the physical systems. One of these shapes of the internal space corresponds to our universe. The remaining shapes could be describing the conditions in different universes.
The string theory and ‘supergravity’ gave rise to the M-theory which in turn has 11 dimensions and is the closest physicists have got to a complete unified description of the universe. A famous quotation attributed to Albert Einstein says “Everything should be made as simple as possible, but no simpler”. So the question is whether the M-theory is a simple way of looking at all the phenomena surrounding us or an incomplete simpler model will be established as further investigations and experiments are conducted.
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