The Theory of Everything – Holy Grail of Physics

by Charitha Saumya

The study about forces which occur between electrically charged particles such as electrons and protons is called Electromagnetism, study about forces that occur between objects which are proportional to the masses of those objects, you call it Gravitation, and the branch of science that describes about any phenomena connected to a flow of electrons is Electricity. One can mention thousands of theories, phenomena, scientific discoveries, inventions because it was the nature of the mankind to be curious about what happens around him and try to explain whatever he observes according to a well-balanced theory. But what if, all those branches of science can be explained by a single unified theory? This may sound strange, but this concept has a fair amount of history and physicists usually call this “The theory of everything” i.e. ToE.

Early Attempts

Many theories were proposed as ToE during the past few centuries but none of them were accepted by the scientific world, hence it remains as an unsolved problem in physics. Archimedes was the first scientist to come up with the idea of explaining every physical observation using some kind of a theory which he called an “Axiom” or principal. Democrates stated that all physical phenomena are caused by the motion of fundamental matter particles or the atoms. In the 17^th century Sir Isaac Newton published “Principia” in which he included the laws of gravity, using those laws he was able to unify Galileo’s studies on terrestrial gravity and Kepler’s Laws of planetary motion. In 1814 Laplace came up with the idea that if we know the position and velocity of a particle at any given time we could find the velocity and position of that particle accurately at any other given time using the laws of nature. In 1820 scientist Hans Christian Orsted accidently discovered that electricity and magnetism are interconnected. While carrying out an experiment he observed a sudden deflection in a compass which was kept near a conducting wire. This interesting discovery resulted in the birth of Electromagnetism, which was formulated in to a well- defined theory by James Clerk Maxwell in 1865. In this era the physicists started to suggest that most of the examples of forces i.e. Friction, viscosity, pressure, contact forces are caused by interactions between smallest particles of matter. In each of these attempts physicists’ objective was to find a unified theory to describe gravity and electromagnetism using a single model, but unfortunately none of them succeeded.

Einstein factor

The search for a ToE faced a revolutionary change in 1915 with the introduction of general relativity by Albert Einstein. Newton’s concepts related to gravity and gravitational force were challenged by Einstein’s general relativity. Einstein suggested that gravity is a result of space time being curved due to objects having a massive mass. Further he stated that the motion of objects (even light) is affected by this curvature of space time. Einstein was able to prove his theory by showing that the path of light waves coming from a distance star gets curved when it travels near the sun. For this he had to wait for a solar eclipse because it was hard to observe a star when it is placed near to the Sun on the sky.

“In a curved space time the motion of objects gets very interesting. For example take earth’s surface as the curved surface. The shortest distance between two points on that surface will be a part of a great circle ; a circle which goes through those two points and the center of which is placed at the center of earth. But this path will be a curved line in a flat map!!!”

With the emergence of general relativity the search for a unified field theory to combine gravity with electromagnetism started with a new intensity. Einstein himself wasted the later stages of his life for this, but had no success.

At that time physicists were more interested in the new findings on Nuclear reactions which actually seemed to be another obstacle for the ToE. The reason was that these nuclear interactions were so different from gravity or Electromagnism. In 1967-68 three physicists, namely Sheldon Glashow, Steven Weinberg and Abdus Salam proposed that the first 2 of the three quantum forces; electromagnetic force, weak force, strong force can be combined through a concept called “electroweak force”. This was when the physics world came to know about “Bosons” which you may have heard already. In quantum field theories a force field is said to be made of these “boson” elementary particles. These particles move back and forth between matter particles transmitting the forces. In lower energies the weak forces are carried by bosons and electromagnetic forces are carried by photons which is also an example for bosons. Matter particles are called “fermions” and electrons, quarks are some examples for fermions. Currently many interesting experiments are carried on these elementary particles using advanced particle detectors to check whether they really exist.

Modern approaches

Presently one of the favorite candidates for ToE is the String theory or the M- theory. Actually this is not a complete theory but rather an approach to find a ToE. The theory is mainly based on the premise that the universe consists of many dimensions than we usually observe. We are familiar with the dimensions that are easily observable to us like space and time but this may not be the case. So this theory tries to deal with a large number of dimensions to derive equations for physical phenomena and compare them with known laws of physics to find some similarities. Interestingly this theory can describe the reason for gravity to be so weak compared to other forces, which is the possibility of gravity being leaked to some other unknown dimensions in ways that other forces would not. But the problem with this theory is that it allows a large number of possibilities for a given universe with an arbitrary number of dimensions. One solution proposed is that these universes coexist but small number of them is good enough to live on. The Idea of Causal sets is another interesting concept which is mainly related to quantum gravity. It is based on the idea that space time is discrete not continuous as most of the physicists believe and space time events are related with a partial order.

The challenge on physicists’ hand is to find unification for electroweak force with strong force and finally combine it with gravity, but still the quest for such grand unified theory has achieved a very little amount of success. Modern physicists states that the future of ToE depends on the ongoing experiments on elementary particles and dark matter because the quest requires more input to produce such universal theory.

References:

http://en.wikipedia.org/wiki/Theory_of_everything

The Grand Design by Stephen Hawking 

Note : This is an article i wrote for the E-Carrier magazine published by the Electronics and Telecommunication department of university of Moratuwa.