The biggest dilemma of Einstein’s life represents the search of a unified theory. Scientists all over the world are currently engrossed in the quest of a unified theory where we unify all the laws of physics, be it Quantum mechanics or the Classical physics: all the laws collated in one single framework which could predict anything and everything.
Currently, we have multiple theories and suggestions for the unified theory but the very promising and compelling one is “the string theory.”
So what is string theory? In physics, string theory represents a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. For example, take a piece of wood. Inside it you would find millions of atoms bonded together. Inside every atom there is a nucleus. The atomic nucleus consists of nucleons—protons and neutrons. Protons and neutrons are made of quarks. The string theory states that inside quarks there are strings which vibrate at different frequencies causing the property of the substance. Now how does this unify all the laws?
In physics we got 4 fundamental laws that underpin the universe: gravity, electromagnetism, strong nuclear force and weak nuclear force.
Gravity is described by Einstein's beautiful mathematics of curved space and time. But the other three forces are written in the language of quantum mechanics. And these two methods are completely incompatible. Presently the string theory says: Various vibrations of this stringy stuff correspond to each of the fundamental particles producing the properties of gravity, light and other elementary substances and laws.
But the mathematics of string theory is a little strange, and in placing the pieces together, physicists needed to add more and more dimensions of space to make their theories work, many more than the three we experience in our everyday lives. For the string theory to work, we don't merely need to put four dimensions but 11 dimensions!
The very idea of extra dimensions dates back to the 19s when a German mathematician named Theodore Kalua suggested a very bold and in some ways very bizarre idea. He proposed that our universe might actually have more than the three dimensions that we are all aware of that is in addition to left-right back-forth and up-down. Kaluza was a man of theory. He could even risk his life for theories but we as practical minded people might ask if there are extra dimensions then where are they? We can't perceive them.
it's a possibility that the dimensions might come in two varieties. There might be big easy to see dimensions but there might also be tiny curled up dimensions curled up so small even though they're all around us that we don't see them.
Let's consider an example of a wire hung a hundred metres apart from you. From our naked eyes we would assume and consider the wire as 2 dimensional. But let's say there are ants on the wire, they could move in any direction and for them those wires would be 3 dimensional. Therefore it is a possibility that the extra dimensions are extremely small for our naked eyes to observe.
Some physicists feel that the theorists on the string theory bandwagon are heading down a dead-end path in the search for ultimate physics, and others feel it's very promising. In fact, we absolutely don't know. We don't know if any of our ideas are truly inching a way towards the ultimate theory, or if a completely alternative approach is required.
In fact, we simply don't know if a grand unified theory barely exists.
But this will not stop physicists from pursuing their search.
Credits : Brian Greene for suggesting the example to explain further dimensions.