Is the End in Sight for Theoretical Physics?

 

Abstract

 

Scientists and physicists have long been in the search for a single unified theory that will describe all the processes in a universe by a single set of equations and the existence of such a theory would result in the Unification of Physics. But there have been many false alarms in the past forcing eminent scientists to claim that physics might be over in just a matter of six months. From the current developments on the scene of theoretical physics, the end of physics has not drawn any closer and it appears that it may be a long while before we can again claim that the ‘End is in Sight for Theoretical Physics’.

 

Theoretical Physics

Before we try to answer the above question it is important for us to understand what a theory is and the relevance of theoretical physics.

·        What is a Theory?

A theory is a simple set of rules and principles expressed in a short message. The scientist Stephen Wolfram describes it as a compressed package of information applicable to many cases. To be a part of science, a theory must make predictions that survive comparison with observation and experiment. Many theories might exist side by side both describing the same phenomenon. But theories which tend to be in serious disagreement with the outcome of careful and well conducted experiments tend to get replace by the theories which agree with experiment and observation in a better way. Sometimes a single contradictory result might be all that is needed to discredit a theory.

·        Function of Theoretical Physics

Theoretical Physics is the branch of physics that essentially gives birth to new, and not always revolutionary, ideas. It is the breeding ground of all the ideas and theories presented by scientists and theoreticians which is always open to scrutiny through experiment and observation, and hence many ideas die in their infancy due to their lack of consistency with observation. In the past, theory and experiment went hand in hand but due to the rapid advancements in our understanding of the nature, theoretical physics and experimental physics have become quite separate. These days having a supposedly correct theory does not mean that the theory has been verified experimentally because sometimes experiments are nearly impossible to carry out. Also, Theoretical physics is not an independent branch but it lies at the root level of all branches of physics and is cause of ingesting new ideas in that particular field.

·        A Brief History of Evolution of Theoretical Physics

In the19th century only 2 theories existed which accounted for the behaviour of the then observed part of the universe: Newton’s Gravitational theory and Maxwell’s theory of Electromagnetic radiation. But these two theories had called for different speeds of light. Maxwell’s theory specified a fixed speed for electromagnetic radiation whereas Newtonian mechanics said that the speed of light would depend on the motion of the observer. In the early 1900’s the two theories of relativity proposed by Einstein solved this problem by stating that no matter what the velocity of the observer, the speed of light shall appear fixed.

The Maxwell’ian theory and the general relativity theory are classical theories in the sense that they treat the universe as continuos. This continuity meant that matter and energy could be divided into as small units as possible.

Quantum revolution changed the way physicists’ view the world and it sets the ultimate limit on how small a unit of time, energy or distance can be. Discoveries about the nature of light led to the formation of the field called Quantum Electro Dynamics (QED) which contains the best of Maxwell’s theory. In the 60’s and 70’s the Weak Nuclear Force was unified with QED by means of the theory called the Electro Weak Theory. Later the Strong Nuclear Force was accounted for by the formulation of the Quantum Chromo Dynamics (QCD). Recently, the String Theories have come into play to possibly incorporate Gravity into the Grand Unified Theories (GUT’s). Now a-days the ultimate goal of physicists is to find a complete, consistent unified theory that describes all physical interactions by a single set of equations.

 

The End of physics

 

The famous British physicist Stephen Hawking is fond of suggesting that the end maybe in sight for theoretical physics. But is the end for physics really insight? Do we know so much of our own universe that we can safely say that soon one day there will be no more to do?

There have been previous occasions on which physicists have thought they were on the brink of finding all the answers. Most famously at the end of the 19th century there was a feeling that with Maxwell’s and Newton’s equations firmly established, every thing else would be merely a matter of detail. Hardly was this feeling firmly established that physics was turned on its head by the twin revolutions of quantum theory and the relativity theory.

It happened again in the 1920’s when Paul Dirac formulated the quantum equations which determine the behaviour of the electron. The only other known particle at that time was the proton and it was thought that a similar equation would account for it as well. Hence it was thought that all was known that there was to know. In 1928 this led physicist and Nobel Prize winner Max Born to say to a group of visitors to Göttingen University that “Physics, as we know it, will be over in six months.” However the discovery of the neutron in 1930 and of nuclear forces knocked that one on the head too!

 

Quantum Physics

The main theory, which seeks to define the universe around us, is the Quantum theory.

The main aim of physicists to date has been to incorporate the quantum theory along with the theory of relativity into a single grand theory. As noted earlier some work has been done towards this end resulting in the unification of electromagnetic and the weak force, which resulted in the formation of the Electro weak theory. Further work led to some unification of these with the Strong nuclear force. Unfortunately none of this progress takes Gravity into account, the most universal of all forces and the first one to be discovered but the most elusive to date in terms of understanding. This was what caused Hawking to remark that ‘Grand unified theories ain’t so grand after all’. Though Hawking has partially succeeded in unifying quantum theory and general relativity in investigating black holes and time beginning, gravity still best defined by the General Theory of Relativity, which is a classical continuum theory.

The hypothesized Quantum Theory of Gravity contains particles called gravitons, which are responsible for the gravitational force of attraction. Though the particles are well understood in theory they are still undetected.

 

Strings

 

In the 1980’s a theory called the ‘Supergravity N=8’ was formulated to account for the graviton and the properties it is supposed to have. But this theory called for a huge number of other particles which are not known. Secondly the calculations involved were so complex that it was remarked that it would take 4 years to do the computation for the simplest case with the aid of computers, and that did not mean that the calculations would be flaw less. Hence the theory was abandoned in favour of another theory called the String theory which was actually invoked in the 1960’s to account for the strong nuclear force. String theories in their best form incorporate the graviton i.e. some equation of the string theory have properties required to describe gravity. Hence they are called Super string theories. It was this road towards unification that Stephen Hawking was enthusiastically endorsing by 1988. String theories have been the best attempts at unification of physics and perhaps its end. But that does not mean the end of problems.

One odd thing about the Super string theory is that it works on a matter of only 26 dimensions! Currently this number has been reduced to 10 dimensions (depending on the particles that we want to define) inclusive of the 4 dimensions that we are aware of: 3 spatial and one time. According to Michael Green of Queen Mary College, one of the pioneers of Super String, Super string theory is a theory in which the details have come first and we are still groping for an insight into the logic of the theory.

Super string theory also requires a property called Super symmetry to be able to function. But given the current technological standards it is extremely difficult to test this. And the energies that are required to prove that the super string theory is the ultimate theory are way beyond those that can be produced on earth even in the distant future. So there is plenty of work left for the physicists to do!

 

What happens when it ends?

 

Hearing Hawking tell you that physics may be coming to an end became something of a cliché in the 1980s, as at the beginning of that decade he used his inaugural lecture as Lucasian Professor at the Cambridge university to pose that question. Years later the end doesn’t look any closer than it was then. But if theoretical physics did reach the ‘end’ Hawking so eagerly predicts, there would still be plenty of work left for physicists to do. In an interview in Newsweek1 in 1988, Hawking said that after discovering the theory of every thing ’there would still be lots to do ‘, but then physics would be like ‘mountaineering after Everest’.

Cosmologist Martin Rees prefers a different analogy. He points out that learning the Rules of chess is only the first step on a fascinating and long path to becoming a Grandmaster. The long sought after theory of every thing is the equivalent of learning Chess rules and grand master status would still be far away. Our goal is a complete understanding of the events around us and of our own existence.

In his Inaugural lecture Hawking emphasized that the laws that Born was so proud of really are all we need in principle to describe the chemical reactions. Paul Dirac in the 1920’s had produced quantum equations that exactly describe how electrons behave and electrons being the essence of all chemistry. The snag is that this equation is too complex to be solved for any elements but the simple most hydrogen.

Biological processes in turn depend on chemistry of complex molecules. In Hawkings words:

…although in principle we now the equations that govern the whole of biology, we have not been able to reduce the study of human behaviour to a branch of applied mathematics.

 

Even if we had a genuine unified theory for the universe it would be far more difficult to use this to work out the behaviour of the universe than it is to work out your behaviour using Dirac’s equation.

 

The Unified theories are one of those prospects that have been receding into the future for the past 2 decades and by saying that the theories were just around the corner the physicists meant was the millenium. Yet today we are just days away from the millenium but where are the complete theories of the universe?

 

 

Conclusion

These days the physicists are a bit more skeptical and besides few who still claim the end to come around 2010 most refuse to be drawn into such speculations.

But suppose the theories were eventually found we can never be quite sure if it is they are correct since we can not prove theories. But if this theory is mathematically consistent and gave good predictions that agreed with observation our faith in the theory will be increased. This would also bring an end to the long and glorious chapter in the history of humanity’s intellectual struggle to understand the universe.

 

Detailed study and evaluation of the theories is beyond the scope of this paper. But from what has been outlined above we can easily draw the conclusion that though we know what end we are looking for that end does not seem to be in sight for quite a long while to come.

 

 

 

 

 

 

 

 

 

 

References

 

Books

Gell-Mann, M. (1994). The quark and the jaguar: adventures in the simple and the complex. New York: W. H. Freeman and Company

 

Hawking, S. (1988). A brief history of time: from big bangs to black holes. Great Briton: Bantam Books.

 

Hawking, S. (1994). Black holes and baby universes and other essays. Great Briton: Bantam Books

 

Gribbin, J., White, M. (1992). Stephen hawking: a life in science. New Delhi: Penguine Books.

 

Magazines

1Hawking, S. (1988, June 13th). Newsweek.

 

Internet

Smolin, L. 1999 ‘What is the Future Cosmology’ @http://www.flash.net/~csmith0/future.htm