In purely intellectual terms, a unified theory of physics would be the greatest of all scientific achievements. It would culminate the ancient human quest for knowledge, which began when the first of our ancestors asked, "Why?" It would yield the basic rules governing the entire universe, from the smallest to the largest scales. It would tell us how the universe came into being and why it took this particular form, which permitted our existence. It might even reveal our ultimate cosmic fate. At least, that's what seekers of a unified theory hope, and what I used to believe. In the early 1990s, I came to suspect that the quest for a unified theory is religious rather than scientific. Physicists want to show that all things came from one thing: a force, or essence, or membrane wriggling in eleven dimensions, or something that manifests perfect mathematical symmetry. In their search for this primordial symmetry, however, physicists have gone off the deep end, postulating particles and energies and dimensions whose existence can never be experimentally verified. The Superconducting Supercollider, the monstrous particle accelerator that Congress canceled in 1993, would have been 54-miles in circumference. Gaining access to the infinitesimal microscales where superstrings supposedly wriggle would require an accelerator 1,000 light years around. (The entire solar system is only one light day around.) It is this problem that makes me confident I will win this bet. The Nobel prize judges have always been sticklers for experimental proof. The dream of a unified theory, which some evangelists call a "theory of everything," will never be entirely abandoned. But I predict that over the next twenty years, fewer smart young physicists will be attracted to an endeavor that has vanishingly little hope of an empirical payoff. Most physicists will come to accept that nature might not share our passion for unity. Physicists have already produced theories-Newtonian mechanics, quantum mechanics, general relativity, nonlinear dynamics--that work extraordinarily well in certain domains, and there is no reason why there should be a single theory that accounts for all the forces of nature. The quest for a unified theory will come to be seen not as a branch of science, which tells us about the real world, but as a kind of mathematical theology. By the way, I would be delighted to lose this bet.
It is often forgotten that physics is mainly done indirectly. Thus, we know that the sun is made of hydrogen gas, yet no one has ever visited the sun. We know that black holes exist in space, yet they are invisible by definition. We know that the Big Bang took place approximately 15 billion years ago, yet no one was there to witness it. We know these things, because we have indirect evidence or "echoes", such as sunlight and characteristic radiation from black holes and Creation. Likewise, you do not need to build an atom smasher the size of the galaxy to prove string theory or M-theory (the leading and, in fact, only candidate for a "theory of everything). Instead, we need to look for echoes from the 10th and 11th dimensions as follows: a) Within a few years, the Large Hadron Collider, the largest atom smasher on earth, will be turned on outside Geneva, Switzerland. It might be able to find "sparticles" or super particles, i.e. higher vibrations or octaves of the superstring. b) Invisible dark matter, which makes up 90% of the matter in the universe, might be shown to consist of sparticles like the photino. This might also verify string theory. c) In this decade, gravity wave detectors should be able to record shock waves from colliding black holes, which might reveal the first quantum corrrection to Einstein's original theory of 1915. These quantum corrections can be compared to those predicted by string theory. d) Within 20 years, NASA plans to send three gravity wave detectors into outer space. They should be sensitive enough to pick up the shock waves from the Big Bang itself created a fraction of a second after the instant of creation. This should be able to prove or disprove string theory. Personally, I feel no need to prove the theory experimentally, since I believe it can be proven using pure mathematics. A theory of everything is also a theory of everyday energies, where we find familar electrons, protons, and atoms. If we can solve the theory mathematically, then we should be able to calculate the properties of electrons, protons, and atoms from pure mathematics. If the results disagree with known data, then string theory will be shown to be a "theory of nothing." However, if the numbers agree, then it will be heralded as the greatest achievement of the human mind. We will have "read the mind of God." So what prevents us from simply solving the theory and comparing the results with nature? The problem is that the theory is smarter than we are. No one on this planet is smart enough to solve this theory. The smartest people on earth are working on this problem, and have so far failed. (This is because the theory was discovered purely by accident in 1968. We were never supposed to see this theory in the 20th century. The mathematics necessary to solve the theory have not yet been discovered.) Because string theory has near-miraculous breakthroughs every 8 to 10 years, we can expect 2 more breakthroughs in the theory before 2020, and hence might be able to solve this theory by then. Perhaps someone reading this bet will be inspired to mathematically solve this theory completely. Maybe that person will then receive a telephone call from Sweden.