Passage 1

  String theory is a work in proGREss whose partial completion has already revealed remarkably elegant answers to questions about nature‘s most fundamental

  constituents and forces. For instance, in string theory many line aspects of nature that might appear to be arbitrary technical 5 details – such as the number of distinct varieties of particle inGREdients and their properties – are found to arise from tangible aspects of geometry of the universe.

  In the final analysis, though, nothing is a substitute for definitive, testable predictions that can determine whether 10 string theory has truly lifted the veil of mystery hiding the deepest truths of our universe.It may be some time before our level of comprehension has reached sufficient depth to achieve this aim. In fact, the mathematics of string theory is so complicated that, to date, no one even knows the exact 15 equations of the theory. Nevertheless, experimrntal tests could provide strong circumstantial support for string theory within the next ten years or so.

  One of the pioneers of string theory summarizes the situation by saying that ―string theory is a part of twenty- 20 first-century physics that fell by chance into the twentieth century. ‖ It is as if our forebears in the nineteenth century had been presented with a modern-day supercomputer,

  without the operating instructions. Through inventive trial and error, hints of the supercomputer‘s power would have 25 become evident, but it would have taken vigorous and prolonged effort to gain true mastery. The hints of the computer‘s potential, like our glimpses of string theory‘s explanatory power, would have provide strong motivation for obtaining complete facility. A similar motivation today 30 energizes physicists to pursue string theory. Science proceeds in fits and starts. Scientists put forward results, both theoretical and experimental. The results are then debated by the community; sometimes they are discarded, sometimes they are modified, and sometimes 35 hey provide inspiration for new and more accurate ways of understanding the universe. In other words, science proceeds along a zigzag path toward what we hope will be ultimate truth, a path that began with humanity‘s earliest attempts to fathom the cosmos and whose end we cannot 40 predict. Whether string theory is an incidental rest stop along this path, a landmark turning point, or the final destination we do not know. But the last two decades of reseach by hundreds of dedicated physicists and mathematicians has given us well-founded hope that 45 we are on the right and possibly final track.

  Passage 2

  No matter how things turn out, the story of string theory is an episode with no parallel in the history of modern physics. More than twenty years of research by thousands of the world‘s best scientists producing tens of thousands 50 of scientific papers has not led to a single testable experimental prediction of the theory. This unpreccedented situation leads one to ask whether one can really describe string theory as science.

  Human beings engage in many different attempts to 55 explain the world around them, but only a specific sort of explanation is normally considered to be scientific. An explanation that allows one to predict successfully in details what will happen when one goes out and performs a feasible experiment is the sort of explanation that most 60 clearly can be labeled. ―scientific. ‖ Explanations that cannot be used to form predictions clearly do not deserve this label.

  Remarkably, the lack of any proGREss in achieving a predictive version of string theory that could be tested by 65 experiment has not led to theorists‘ giving it up. Indeed, in recent years, many string theorists have become convinced that string theory inherently must allow an astronomically large number of physical possibilities, so many that it is difficult to see how the theory can ever be tested. Yet some 70 theorists are convinced that a better understanding of the theory will uncover testable phenomena. This way of thinking is a steadfast refusal to acknowledge the lesson that conventional science says one should draw in this kind of circumstance: if one‘s theory can‘t predict anything, one 75 should try something else.

  The phrase ―not even wrong ‖ is popular among physicists. A theory can be ―not even wrong‖ because it is so incomplete and ill-defined that it can‘t be used to make predictions whose failure would show it to be wrong. 80 This sort of ―not even wrong‖ is not necessarily a bad thing. Most new theoretical ideas begin in this state, and it can take quite a bit of work before their implications are well enough understood for researchers to be able to tell whether the idea is right or wrong. But there is a second 85 connotation of ―not even wrong‖: something worse than a wrong idea. In case of string theory, the way some physicists are abandoning fundamental scientific principles rather than admit that a theory is wrong is something of this

  kind: worse than being wrong is refusing to admit when 90 one is wrong.