In discussing in this blog Lee Smolin’s new book, The Trouble with Physics: The Rise of String Theory, the Fall of Science, and What Comes Next, we are trying to characterize modern theoretical physics research in general, in what we refer to as the legacy system of physical theory (LST). Smolin’s book, as well as the book, Not Even Wrong: The Failure of String Theory and the Continuing Challenge to Unify the Laws of Physics, by Peter Woit, which is written along the same lines, has stirred up considerable controversy, especially among string theorists, who constitute by far the largest segment of LST theorists in the world today.
However, as these authors point out, the string theory controversy is only symptomatic of the central problem: The crisis in theoretical physics revolves around the fundamental issues that string theory was meant to address, and, thus, its failure, and especially the refusal to recognize its failure on the part of the largest segment of theoretical physicists in the LST community, implies a serious pathology in their ranks.
Unfortunately, most of the string theory community, acting more like a beleaguered government bureaucracy, than an eminent scientific community, have initially tended to defend the implications of the crisis, rather than to take their lumps and to begin to engage in an honest investigation of the probable causes involved. Nevertheless, it seems inevitable that this multi-billion dollar a year enterprise must face the music sooner or later: The truth is that the string theory approach has only managed to exacerbate the already shaky ground of the LST efforts to understand the structure of the physical universe.
Yet, Smolin’s thesis that the crisis has developed into epic proportions from historical roots that hearken back to Newton’s and Leibniz’s debate over the nature of space, which he establishes quite convincingly, only seems to irritate the string theorists whose own point of departure is that the concept of string vibrations solves the fundamental problem that the inverse square law introduces into particle interactions, and, in so doing, leads to a consistent theory of quantum gravity.
Thus, we see that the new definitions of space and matter lie at the heart of the crisis. For Smolin, the major fundamental point to be clarified is that space does not exist a priori, as a fixed structure, to provide the required background for motion, while for string theorists, the major fundamental point to be clarified is that matter does not consist of spaceless point entities, but spatially extended entities. Therefore, the Smolin vs.string theorists controversy actually boils down to an argument of whether it is better, in addressing the fundamental crisis of physics, to redefine space, as a dynamic network of discrete events, satisfying the postulates of geometry, or whether it is better to assume a fixed background and redefine matter instead, as extended objects, removing the infinities caused by the inverse square law.
Smolin points out the challenges and inconsistencies encountered in attempting to redefine matter, as string theorists have done, with their need for extra dimensions of space, and the need to cope with the landscape, etc, and string theorists point out the limited scope of the attempts to redefine the concept of space in order to devise a theory of quantum gravity that doesn’t connect with the force concepts of the standard model. The result is the so-called string wars now raging in the blogosphere and even in the printed media press, where much more heat than light is being generated.
Lately, the controversy has even spread into the field of cosmology, where the LST concept of the hot big bang is being challenged by physicists who are convinced that M-theory, with its membranes of space-time existing in unseen dimensions, allows them to explain the big bang as a recurring event in an endless cycle of brane collisions (see here).
In the meantime, the pink elephant in the room that everyone is ignoring is that the common understanding of the edifice of LST physics, built on the foundations of relativity and quantum mechanics, which Smolin characterizes as the “unfinished revolution,” is plagued by what Hrvoje Nikoli´ calls “myths.” Hence, given these problems in our understanding of the foundation of physics, the seemingly endless speculations and inventions of modern physicists, in their attempts to integrate a theory of quantum gravity into the current picture of the standard model and the big bang, and thus finish the spacetime revolution, seem misguided, if not pathetic.
Carlo Rovelli, a colleague of Smolin’s, in a paper entitled “Unfinished revolution,” describes the vision of LST theoretical physics as follows:
At the beginning of the XX century, General Relativity (GR) and Quantum Mechanics (QM) again began reshaping our basic understanding of space and time and, respectively, matter, energy and causality —arguably to a no lesser extent [than the Copernicus/Newton revolution]. But we have not been able to combine these new insights into a novel coherent synthesis, yet. The XX century scientific revolution opened by GR and QM is therefore still wide open. We are in the middle of an unfinished scientific revolution. Quantum Gravity is the tentative name we give to the “synthesis to be found”.
This view, that a synthesis of GR and QM, as a theory of quantum gravity, is now the primary quest of LST physics, implies that these two theories, that have “reshaped our basic understanding” of space and time, and matter, energy and causality, provide a solid foundation to build that theory of gravity upon. Indeed, Rovelli sums up the lesson to be learned as follows:
After a century of empirical successes that have only equals in Newton’s and Maxwell’s theories, it is time to take seriously GR and QM, with their full conceptual implications; to find a way of thinking [about] the world in which what we have learned with QM and what we have learned with GR make sense together —finally bringing the XX century scientific revolution to its end. This is the problem of Quantum Gravity.
But if our common understanding of “what we have learned with QM, and what we have learned with GR,” is plagued with “myths,” what are the chances of making it all “make sense together” by taking it seriously? In the abstract of his paper, “Quantum Mechanics: Myths and Facts,” Nikoli´ explains what he means in using the word myth in this connection:
A common understanding of quantum mechanics (QM) among students and practical users is often plagued by a number of “myths”, that is, widely accepted claims on which there is not really a general consensus among experts in foundations of QM. These myths include wave-particle duality, time-energy uncertainty relation, fundamental randomness, the absence of measurement-independent reality, locality of QM, nonlocality of QM, the existence of well-defined relativistic QM, the claims that quantum field theory (QFT) solves the problems of relativistic QM, or that QFT is a theory of particles, as well as myths on black-hole entropy. The fact is that the existence of various theoretical and interpretational ambiguities underlying these myths does not yet allow us to accept them as proven facts.
In the introduction of his paper, Nikoli´ carefully explains the difference between the oft-cited success of QM and the problematic nature of its foundational concepts:
On the technical level, quantum mechanics (QM) is a set of mathematically formulated prescriptions that serve for calculations of probabilities of different measurement outcomes. The calculated probabilities agree with experiments. This is the fact! From a pragmatic point of view, this is also enough. Pragmatic physicists are interested only in these pragmatic aspects of QM, which is fine. Nevertheless, many physicists are not only interested in the pragmatic aspects, but also want to understand nature on a deeper conceptual level. Besides, a deeper understanding of nature on the conceptual level may also induce a new development of pragmatic aspects. Thus, the conceptual understanding of physical phenomena is also an important aspect of physics. Unfortunately, the conceptual issues turn out to be particularly difficult in the most fundamental physical theory currently known – quantum theory.
The “particularly difficult” conceptual issues of QM form the number 2 problem of the five, “famously intractable,” problems of theoretical physics, which Smolin articulates in his book. It is second only to the discrete vs. continuous problem, the number 1 problem of theoretical physics. As he describes it, this number 2 problem is that, in QM, the structure of the physical universe cannot be described as something that exists independently of the observer. Smolin writes on page 7 and 8 of his book:
Since quantum theory was first proposed, a debate has raged between those who accept this way of doing science and those who reject it. Many of the founders of quantum mechanics, including Einstein, Erwin Schrodinger, and Louis de Broglie, found this approach to physics repugnant. They were realists. For them quantum theory, no matter how well it worked, was not a complete theory, because it did not provide a picture of reality absent our interaction with it. On the other side were Niels Bohr, Werner Heisenberg, and many others. Rather than being appalled, they embraced this new way of doing science…
This whole issue goes under the name the foundational problems of quantum mechanics. It is the second great problem of contemporary physics.
Problem 2: Resolve the problems in the foundations of quantum mechanics, either by making sense of the theory, as it stands, or by inventing a new theory that does make sense.
Unfortunately, however, the schoolmen don’t teach the subject this way, but rather tend to gloss over the problem and this is why Nikoli´ uses the word myth in his paper. He explains:
Textbooks on QM usually emphasize the pragmatic technical aspects, while the discussions of the conceptual issues are usually avoided or reduced to simple authoritative claims without a detailed discussion. This causes a common (but wrong!) impression among physicists that all conceptual problems of QM are already solved or that the unsolved problems are not really physical (but rather “philosophical”). The purpose of the present paper is to warn students, teachers, and practitioners that some of the authoritative claims on conceptual aspects of QM that they often heard or read may be actually wrong, that a certain number of serious physicists still copes with these foundational aspects of QM, and that there is not yet a general consensus among experts on answers to some of the most fundamental questions. To emphasize that some widely accepted authoritative claims on QM are not really proven, I refer to them as “myths”.
Attempting to build “a theory of everything” from the concept of quantum gravity, which is built on string theory, or from the concept of quantum gravity, which is built on loop theory, given the shaky foundations of quantum mechanics, is just foolish, it seems to me. We need to know why QM works, even though the concepts of “wave-particle duality, time-energy uncertainty relation, fundamental randomness, the absence of measurement-independent reality, locality of QM, nonlocality of QM, the existence of well-defined relativistic QM, the claims that quantum field theory (QFT) solves the problems of relativistic QM, or that QFT is a theory of particles,” are fundamental concepts that “may be actually wrong.”
If we don’t solve these problems first, how in the world can we think that finding a “synthesis” of GR and QM will ever be possible? And this honesty about the foundations of quantum mechanics is only part of what we need to consider. What about the foundations of general relativity? Can we really feel secure in believing that spacetime is something that exists as a dynamic field, fully capable of being warped and dragged about, like a rubber sheet, but not observable in any manner other than in its effects, or could this too be just another myth in our common understanding?
It appears that there is much more to “finishing the revolution” than synthesizing GR and QM into a new theory of quantum gravity. What is really needed is a much more fundamental revolution than we have in GR and QM. In the RST-based theoretical development, both space and matter have been redefined, and the result is that a new vision of the structure of the physical universe emerges, where the paradoxes of particle/wave duality and the existence of a measurement-independent reality not only arise in a natural and intuitive manner, but also provide tantalizing clues to the mystery of gravity.
Thus, it’s not that we have to finish the revolution that was begun in the twentieth century, but that we have to understand it for what it really is: The initial attempt to deal with problem number 1, which has resulted in problem number 2.