End of Physics

The Theory of Everything, if you dare to be bold,

Might be something more than a string orbifold

While some of your leaders have got old and sclerotic,

Not to be trusted alone with things heterotic

Please heed our advice that you too are not smitten-

The Book is not finished, the last word

is not Witten.

(Sheldon Glashow, 10)

Many particle physicists are engaged in developing a theory that purports to unify all the fundamental forces of nature. Such a theory has been overzealously dubbed as the Theory of Everything (TOE). A number of popular science writers and professional physicists are embroiled in a hot discussion suggesting that such a theory may herald an end to physics. This implies that there may not be any challenging and exciting problems left for the physicists to work on after TOE.

Unification of the fundamental forces was the life long goal of the greatest scientist of the twentieth century, Albert Einstein, but he could not achieve it. This coveted goal seemed very remote in the first half of the twentieth century although it was generally believed that a completely unified theory should exist. Endeavors for attaining this goal were vigorously revived in the 1960's when Abdus Salam and Steven Weinberg successfully unified the weak and electro-magnetic forces in a single force in 1967, which is now called the electro-weak force. Both of them worked independent of each other and were rewarded with the Nobel Prize in 1979 in appreciation of their monumental work. The ultimate goal was still elusive although another significant step had been taken in1970's which unified the electro-weak force with the strong nuclear force. But unfortunately there was not one such a unified theory but a whole plethora of them and it is difficult to decide which one of these theories would ultimately lead to the complete unified theory of fundamental forces. It is also not very clear if any of these theories will indeed unify the force of gravity with the unified strong and electro-weak forces. Such theories have been grandiosely called the Grand Unified Theories or GUT's. Commenting on the nomenclature of GUT's, Stephen Hawking (14) remarked: "Such theories are given the rather exaggerated title of 'grand unified theories' or GUT's. This is rather misleading because they are neither all that grand, nor fully unified, nor complete theories in that they have a number of undetermined renormalization parameters such as coupling constants and masses."

Sheldon Glashow who had achieved a great degree of success with the Standard Model and the unification of strong and electro-weak forces deliberated the possibility of bringing the gravitational force into the fold of GUT's and developing a complete unified theory. He (11) seemingly muttered to himself, " Can mere mortals succeed where the great Einstein had failed? They are trying hard and they've come up with something new and promising and devilishly hard to understand: the Superstring." Interest in the earlier string theories had waned in the 1970's when it was discovered that the theory required a twenty- six dimensional spacetime to succeed. Such an idea was preposterous and unpalatable to most of the physicists. More disturbing was the prediction of a particle that was dubbed "tachyon" and had an imaginary mass. The whole thing was then dropped like a hot potato.

Interest in the string theory was again revived in early 1980's when the old ideas were treated with a dose of supersymmetry. This led to the formulation of a theory that needed ten dimensional spacetime instead of the twenty- six as in the earlier version, and the tachyon also exited gracefully from the theoretical framework. The beauty in this new theory, the superstrings as it is called, is that the gravitational force is incorporated in the theory naturally. According to Kaku (18), "When the constraints that the string places on spacetime were first calculated, physicists were shocked to find Einstein's equations emerging from the string. This was remarkable; without assuming any of Einstein's equations, physicists found that they emerged out of the string theory, as if by magic. Einstein's equations were no longer fundamental; they could be derived from the string theory." So, it appears that the superstrings theory may provide a suitable framework for achieving complete unification of the fundamental forces. No other feasible formulation is known so far.

In spite of this, the ultimate goal is still not in sight. In the euphoria of such an optimistic climate, the nomenclature of 'Theory of Everything' was born.

THE NAME IS BIGGER THAN THE GUTS

In spite of the bombastic title, a theory of everything is nothing but a unified theory of fundamental forces. Discussing the nature of the claim implicit in the name, Davies and Brown (3) have remarked, "No science is more pretentious than physics, for the physicist lays claim to the whole universe as his subject matter… The notion that nothing but the laws of physics are needed to account for the entire universe, in all its infinitely subtle details, is encouraged by the philosophy of reductionism…We do not intend to argue here whether this reductionist line of reasoning can be sustained, but merely point out that it is in this spirit that some physicists have recently been talking about Theories of Everything, or TOE's". Commenting on 'everything' in the title of TOE, Barrow (1) said, "Of course, we must be circumspect in our use of such a loaded term as 'Everything'. Does it really mean every thing, the works of Shakespeare, the Taj Mahal?" "No, it doesn't", he concluded. Michael Green (7), one of the founders of the superstrings theory, and who is one of the few who kept the theory alive while many others had moved away in despair and frustration, comments as follows: "Let me just say that it's because we really understand so little of the deep structure of the theory, that I object to this terminology that's often used, that this is the theory of Everything…. I think saying it's a Theory of Everything is merely saying it seems as though it might answer the questions that we now think are important in particle physics."

EXPECTING EAGERLY BUT NOT DELIVERED YET

Ever since Green and Schwarz infused a new life in the theory of superstrings in early 1980's, there has been a bated anticipation that the TOE is about to emerge. In the excitement of such an expectation, the inappropriate title of theory of everything was coined. But the wait is still not over. Scientists of the stature of Stephen Hawking had predicted that unification will be secured before the end of the twentieth century but the clock is still ticking and TOE is not in sight yet. Opening his Lucasian lecture in 1980, Hawking (14) had described, "…I want to discuss the possibility that the goal of theoretical physics might be achieved in the not too distant future say, by the end of the century." Gripped by a feverish excitement, the physicists have been making all kinds of predictions about the time when the ultimate fulfillment of unification will be achieved. Writing under the title of "A Unified Physics by 2050?", Steven Weinberg (21) concluded his paper by saying, "It is impossible to say when the problems will be overcome. They may be solved in a preprint put out tomorrow by some young theorist. They may not be solved by 2050, or even 2150." Realizing the difficulties in formulating a complete unified theory of superstrings, Ed. Witten remarked that the theory belonged to the twenty first century but was dropped by accident into the twentieth century. In answer to a question, Glashow (6) stated, " We do not yet have a theory which incorporates gravity. We may have the beginning of such a theory, but just the very beginning. My friends, the string theorists, who work with today's vision of truly unified theory, including gravity, say that it will take them twenty years to begin to make contact between the world of gravity and the world of elementary particles." Kitty Ferguson (9), Hawking's biographer, asked Hawking in June 1990, how would he change his Lucasian lecture of ten years before were he to write it over again today. "Is the end in sight for theoretical physics?", Hawking said yes, "But not by the end of the century. The most promising candidate to unify the forces and particles is no longer N=8 super-gravity (as he had previously surmised) ... It's the superstrings."

It thus appears that much of the ongoing hoopla about the anticipated fruition of a unified theory is still premature. All that has actually happened is that there is a sense of realization that one of the superstrings theories may hold a promise for unifying the fundamental forces completely. It is not even clear yet which one of the five or six theories, which are most promising for such a purpose, will eventually succeed.

DISSIDENT VIEWS

Some of the physicists working with the theory of Quantum Chromo-Dynamics (QCD), believe that the superstrings concept is contrived and will not succeed. The implied requirement of a ten dimensional spacetime for the superstrings theories in which unification can take place is naïve and outlandish concept. Another issue of concern is that the superstrings theories cannot be completely experimentally verified. Such verification needs production of extremely high energy (10^18 G eV) for experiments; even if all the wealth in the world were to be expended for building the required apparatus, it cannot be done. The theory is not testable. A theory that cannot be tested and validated by experiments is merely a hypothesis, not a theory. Is there a reverberation of 'positivism' here? Heisenberg (16) who had also been concerned about this issue in the past with respect to quantum mechanics, had described his views, which bear on the experimental verification of a theory, thus, "…I thought it was probably the idea of introducing only observable quantities….Einstein had pointed out to me that it is really dangerous to say that one should only speak about observable quantities. Every reasonable theory will, besides all things which one can immediately observe, also give the possibility of observing other things more indirectly." At another place, Heisenberg (17) described, "… at that time the theory of Bohr was not at all generally recognized as a good theory. The experimental physicists. for instance, … disliked all this game of quantum terms and quantum jumps, they called it atomystic, that is mysticism of the atom, and they felt that it was so much unlike classical physics that it was really not to be taken seriously." In support of formulating a theory of superstrings even when its experimental verification can not be done any time soon, Kaku (18) observes, "I don't think that we have to wait a century until our accelerators, space probes, and cosmic-ray counters will be powerful enough to probe the tenth dimension indirectly. Within a span of years, and certainly within the lifetime of today's physicists, someone will be clever enough to either verify or disprove the ten-dimensional theory by solving the field theory of strings or some other non-perturbative formulation. The problem is thus theoretical, not experimental."

Einstein had formulated his theory of general relativity in 1915 and the first verification came in 1919 through Eddington's observations of bending of rays of light in the vicinity of the sun during a solar eclipse. Ever since, all the observations and measurements have verified the theory of general relativity. Experimental verification of the electro-weak theory came some 10 - 12 years after the publication of the theory; even the Nobel Prize was awarded to the authors before the theory had been experimentally verified. Similarly, Dirac's theoretical prediction of antimatter was verified several years after the publication of his theory.

In an interview with Paul Davies, Richard Feynman (4) said, "I am an old man now, and these (superstrings) are new ideas, and they look crazy to me, and they look like they're (string theorists) on the wrong track. Now I know that other old men have been very foolish in saying things like this, and therefore I would be very foolish to say this (superstrings theory) is nonsense. I am going to be very foolish because I do feel strongly that this is nonsense! I can't help it even though I know the danger in such a point of view. So perhaps, I could entertain the future historians by saying I think all this superstrings stuff is crazy and is in the wrong direction." Richard Morris (19) has expressed Glashow's and his colleague Paul Ginsparg's views about the superstring theories as follows: "Contemplation of superstrings may evolve into an activity…. to be conducted at schools of divinity by future equivalents of medieval theologians. For the first time since the Dark Ages, we can see how our noble search may end with faith replacing science again." At another occasion, Glashow (6) remarked, "…It has often been said by my string theory friends that superstrings are going to dominate the next half of a century. Ed Witten has said that. I would like to modify that remark. I would say that string theory will dominate the next fifty years of physics in the same way that Kaluza-Klein theory, another kookie theory upon which string theory is based, has dominated particle physics in the past fifty years. Which is to say, not at all."

However, there are many other prominent theoretical physicists who support the superstrings theory. In addition to Hawking, Salam and Weinberg, both Nobel Laureates like Glashow and Feynman, look upon the theory favorably. "Superstring theory is now the only game in town", said Weinberg after a conference (20). There are thousands of other young physicists who work ceaselessly to develop and advance the theory. They are the ones who will prove whether the theory of superstrings will one day become the Theory of Everything. Michael Green (7), one of the founders of the superstrings, has this to say about the theory: "I can not imagine how any one who has previously worked on general relativity, for example, and who is now working on string theory, would ever go back to working on general relativity without strings."

END OF PHYSICS

We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance. (John Wheeler)

Will TOE sound the death knell for physics? The answer to this question is not quite definitive; it is ambivalent in nature. In other words, the answer is 'yes' and 'no'. Yes, the great challenge of finding a completely unified theory of fundamental forces will be settled, and no, it will not be the end of physics. The show will go on, albeit, may be, on a lower plane than before. Ferguson (9) asked Hawking," .. If somebody does find the Theory of Everything, what then?" Hawking replied, "doing physics after that would be like mountaineering after Mount Everest has been conquered. Hawking has also said that for humanity as a whole it would only be the beginning, because although a Theory of Everything would tell us how the universe works and why it is the way it is, it won't tell us why it exists at all." The views of most of the stalwarts in the world of theoretical physics regarding this question are a mixed bag. They feel that although the most serious challenge would disappear from the field of theoretical physics after the discovery of TOE, the complexity of problems requiring solution would still remain. Steven Weinberg (21) suggests, "This will not be the end of physics. It probably won't even help with some of the outstanding problems of today's physics, such as understanding turbulence and high temperature superconductivity. But it will mark the end of a certain kind of physics; the search for a unified theory that entails all other facts of physical science." The phenomenon of fluid turbulence, as mentioned by Weinberg, is indeed very complex and has the potential of challenging the best brains in physics for careful research and investigation (n). Gleick (12) has described a story about the quantum theorist, Werner Heisenberg, on his death bed declaring that he will have two questions for God: "why relativity, and why turbulence." Heisenberg said, "I really think He may have an answer to the first question."

Chaos is another field of research, which holds a great promise for useful work in many areas of theoretical and applied physics. According to Gleick (13), "The most passionate advocates of the new science go so far as to say that the twentieth century science will be remembered for three things: relativity, quantum mechanics, and chaos. Chaos, they contend, has become the century's third great revolution in the physical sciences." As long as human mind is capable of thinking, there will not be scarcity of good challenging problems to work on. Cartesian adage, "I think, therefore I am", applies globally and for as long as the human race exists. There will always be sufficient mysteries in the universe for man to ponder upon. There cannot be any end to science or physics. The most vitriolic critic of superstrings, Glashow (11), says in the last paragraph of his book, Interactions, "History is on our side. Every few years there has been a world-shaking discovery in fundamental physics or cosmology. There has been well over a hundred such discoveries since Newton's day. Can any one really believe that nature's bag of tricks has run out? Have we finally reached the point where there is no longer a new particle, a 'fifth' force, or a bewildering new phenomenon to observe? Of course not. Let the show go on." And Robert Brandenberger (2), a physicist and cosmologist at Brown University, "..considers the popular notion of the 'end of physics' laughable. How could we be close to the end of physics when we even don't know what nine-tenths of the matter in the universe is made up of?"

In answering a question posed by Davies that if the superstrings theory did describe the fundamental principle on which the world is built, will the theoretical physics then have come to an end, John Schwarz (8) replied, "I think that's a logical possibility, but very unlikely…Our experience to date is that whenever we succeed in answering a question, five more get raised by the knowledge of that answer. We see no indication that that's not going to continue to be the case for a long, long time." And according to Michael Green (7), "I am not, myself, of the opinion that these are 'ultimate building blocks'. I just can not believe that in two billion years time no body will have come up with a better theory."

The real problem is that many physicists are in a state of hyper- excitement and they oscillate like a pendulum between extremes. Although the unification of the fundamental forces has not yet been accomplished and may not be accomplished for a long time yet, the string theorists are making all kinds of predictions. Some of them believe that the theoretical physics will come to an end with the discovery of TOE while others like Schwarz and Green, the founders of the superstrings theory, suggest that the accomplishment of TOE will raise new questions which will need new answers. All of these claims are mere speculations. What happens after TOE is developed, remains to be seen after TOE is developed. A lot of confusion has been created by the misleading title of Theory of Everything that has been assigned to unified theory of fundamental forces. An end of physics was announced towards the end of the nineteenth century also. Two new branches of physics came into being within only a couple of decades of the beginning of the twentieth century, namely Relativity and Quantum Mechanics. Holding history as our guide, it is prudent not to indulge in making extravagant predictions about the future of physics, which are not supported by reasonable facts.

CONCLUSION

The title "Theory of Everything" is inappropriate and a misnomer; the superstrings theory if it ever succeeded in unifying the fundamental forces of nature would still be a unified theory, not a theory of every thing. It is true of course that of all the theories tested so far, superstrings theory appears to have a better chance to succeed. Still, it is curious as to how can any one make so many and such far reaching predictions with a theory which has not yet been developed. The predictions are at best hopes and expectations, which may or may not materialize.

Another thing that should be realized is that the extent of human knowledge is much more limited than the extent of his ignorance. The so called TOE will push the frontier of our knowledge farther but will not explain every thing. Every thing includes all the natural sciences, the social sciences, philosophy, arts, and the whole lot. TOE will probably not even explain every thing that falls in the domain of physics alone.

NOTE

Heisenberg, one of the notable founders of quantum mechanics, had written his Ph.D. thesis on the stability of laminar flow between two fixed walls. He had predicted a limit of stability of the laminar flow. The flow remained laminar up to a certain critical value of the Reynolds number beyond which it would become turbulent. This is in agreement with the experimental results and observations. Heisenberg narrated an interesting and enlightening story about his work. According to him (17), "I got my degree …. but one year later a very good mathematician, Noether, published another paper in which he proved by very rigorous mathematical methods that this problem which I had treated had no stable solution; the flow should be stable every where…in 1944 Dryden and collaborators made very accurate measurements of the laminar flow between two walls and the transition to turbulence. They found that really the calculations which I had made agreed well with the experiment… and now the question was 'what about this rigorous mathematical paper'. Well, the trouble is, I think, that even now no body knows what the mistake in the paper was."

The moral of the story is that turbulence is a complicated field of investigation and will present a challenge big enough to the best of the physicists. At the same time, the story underlines the importance of experimental verification of theoretical predictions.

REFERENCES

1. Barrow, J.D., "The Theory of Everything -What's Knowable And What's Not", http://www.the-scientist.com/yr1990/dec/opin-901210.htm

2. Brandenberger, R., and Alexander, S., "The Allure of the Unknown" in The Voyage of Discovery, Brown University, Annual Report 1997-98, http://www.brown.edu/Adminstration/Rpts/anrept/1997-98/speci al.htm.

3. Davies, P.C.W., and Brown, J., "Superstrings - A Theory of Everything", Cambridge University Press, 1998, pp.1-2.

4. Ibid., pp. 193-94.

5. Ibid., p. 181.

6. Ibid., p.191

7. Ibid., pp. 137 - 39.

8. Ibid., p. 86.

9. Ferguson, K., "Stephen Hawking - Quest for A Theory of Everything", Bantam Books, New York, 1992, pp. 159-60.

10. Glashow, S, with Ben Bova, "Interactions", Warner Books, New York, 1988, p. 333.

11. Ibid., p. 335.

12. Gleick, J., "Chaos", Penguin Books, New York, 1987, p. 121.

13. Gleick, J., "Chaos", in The World Treasury of Physics, Astronomy, and Mathematics, ed. Timothy Ferris, Little, Brown, And Company, 1991, p. 460.

14. Hawking, S., "Black Holes and Baby Universes", Bantam Books, New York, 1993, p. 49.

15. Ibid., p. 58.

16. Heisenberg, W., "Theory, Criticism, And Philosophy", in Unification of Fundamental Forces, 1988 Dirac Memorial Lecture, New York, 1990, pp. 98 - 100.

17. Ibid., pp. 102 - 104.

18. Kaku, M., "Hyperspace", Anchor Books Doubleday, New York, 1994, pp. 154,189.

19. Morris, R., "The Edges of Science", Prentice all Press, New York, 1990, p. 146.

20. Parker, B., "Search for a Super Theory", Plenum Press, New York and London, 1987, p. 247.

21. Weinberg, S., "A Unified Physics by 2050?", Scientific American, December, 1999, http://www.sciam.com/1999/1299 issue/1299.weinberg.html., p. 10 of 10.