2. The Music of the Superstrings (I of V)

Posted by Spinning the superweb |

Watch the following video where Professor Michio Kaku talks about the Music of the Universe and String Theory.

Promotional material for the Strings 04 conference. This image was reproduced, as far as I know, on large posters, on the website of the conference, and on the cover of a compilation of talks intended for a lay public; the latter took place at La Sorbonne on 3rd July 2004. The session for the general public originally included the following speakers: G. Veneziano, J. H. Schwarz (not delivered), R. H. Dijkgraaf, J. M. Maldacena, D. J. Gross, and B. R. Greene.

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The interviewer starts by asking “what is string theory?” and “Einstein’s true successor” replies:
String theory is an attempt at a deeper description of nature by thinking of an elementary particle not as a little point but as a little loop of vibrating string. One of the basic things about a string is that it can vibrate in many different shapes or forms, which gives music its beauty. If we listen to a tuning fork, it sounds harsh to the human ear. And that’s because you hear a pure tone rather than the higher overtones that you get from a piano or violin that give music its richness and beauty.

So in the case of one of these strings it can oscillate in many different forms — analogously to the overtones of a piano string. And those different forms of vibration are interpreted as different elementary particles: quarks, electrons, photons. All are different forms of vibration of the same basic string. Unity of the different forces and particles is achieved because they all come from different kinds of vibrations of the same basic string. In the case of string theory, with our present understanding, there would be nothing more basic than the string.[source] (Italics added.)

That the world around us possesses musical attributes has been a preferred theme of philosophers and mystics since the early days of Western culture. The relationship has also been emphasized by highly regarded scientists, from Johannes Kepler, in the seventeenth century, to Edward Witten ― as the above quotation shows. However, the exact nature of this relationship has been subjected to different interpretations through the centuries. For example, the mystical stance sustained by Pythagoras more than two millennia ago, concerning a musical universe, diverges substantially from that proposed by contemporary string theorists. Thus, even though string theorists claim, as many before them did, that their physical universe has something to do with music, their association is unique. It cannot be reduced to previous conceptions. This new relationship between music and physics is the subject of the present essay. Before embarking upon this study, let us begin by saying a few words about the epistemological posture of string theorists.

As many other theoretical physicists do, string theorists start from the assumption that the complex world we live in is ultimately made up of minuscule elements. Everything we see and experience, from the very small to the bigger structures of the universe, is the result of the interaction of these tiny fundamental constituents ― once called atoms. In the jargon of modern theoretical physics they are known as elementary particles. For popular accounts, instead, “the building blocks of nature” is favoured. The interaction between these particles can be by gravitational or non-gravitational forces; best described by the general theory of relativity and the standard model of particle physics, respectively. This approach to the study of nature has been named “reductionism” by philosophers of science. String theorists, reductionists as they are, of course think that the fundamental ingredients of nature are minute objects. However, for them, these are not punctual objects but rather little strings. “The superstring theory … assumes that the ultimate building blocks of nature consist of tiny vibrating strings.”[source] Moreover, in string theory there is not a “zoo” of fundamental particles like in the standard model ― an unnecessary complication for describing the simplicity of nature according to string theorists. Rather, there is just one type of fundamental string. The rest of the things observed in the universe are simply different modes of vibration of this creative string. Only one string produces the orderly and beautiful universe: the cosmos.

At this point, a question comes to mind: why is this fundamental object called a string and not a particle, or an atom? Just a coincidence ― a happy one as we will see. The point is that the basic equation of the theory (the equations of motion of the fields) is similar to that which describes the oscillations of a string. For many years the formula was known as the “vibrating string equation,” thus, experts in the new field decided to use the same name for the theory and its fundamental object. Pushing the analogy a bit further, proponents of the theory concluded that their string should also produce a sort of sound, as much as the vibrating string produces musical notes. Many string theorists allege that this comparison makes sense since the spectrum of the fundamental superstring includes, in principle, each and every elementary particle of nature. More or less in the same way as the monochord can produce all possible audible notes. Despite these similarities, the association of superstring vibrations with musical notes requires further examination. Because, we can understand the reductionist claim that “there is nothing more basic that the string”; but, why this should give rise to a beautiful composition, as found in music, is not so clear. If we wish to understand this, it is clear that the answer cannot come from within string theory itself. We are forced to take a broader historical and contextual approach.

Some historians of science have tried, as have many aficionados of mystical beliefs, to answer this question. The most serious explanatory accounts deem that the long Western tradition relating music and physics, from Pythagoras to Einstein, is at the base of modern considerations. For instance, some time ago Thomas Kuhn noticed, but, to my knowledge, never tried to fully clarify, the historical reasons behind this relationship:
Other frequently remarked but still little investigated phenomena also hint at a psychological basis for this cleavage. Many mathematicians and theoretical physicists have been passionately interested in and involved with music, some having had great difficulty choosing between a scientific and a musical career. No comparably widespread involvement is visible in the experimental sciences including experimental physics (nor I think, in other disciplines without an apparent relationship to music). But music, or part of it, was once a member of the cluster of mathematical sciences, never of the experimental.[source] (Italics in the original.)

It seems to me that this attempt at an explanation is innacurate. In addition to a long-range perspective, as Kuhn suggests we use, I think that particular historical circumstances must also be considered. But, in spite of its inexactitude, Kuhn’s preoccupation will guide us towards our goal. In this essay I will first identify who those physicists were that “had great difficulty choosing between a scientific and a musical career.” In so doing, we will be ready to embark upon other important questions such as: can we compare Kuhn’s “theoretical physicists” with contemporary string theorists? do these physicists have the same interests and motivations for connecting music and physics? and, are the scientific and cultural contexts the same? These are the sort of questions Kuhn suggested needed investigation. The answers to them will be at the centre of my own discussion concerning the relationship between string theory and music.

I’ve organized the essay as follows. The first part recounts the history of the relationship between music, and philosophical and scientific descriptions of nature. The focus is on Western culture and on doctrines and theories of relevance to understanding “the music of the superstrings.” This introductory part will be useful, as well, for the discussion that follows in the next essays. I then point to those theoretical physicists that Kuhn was, maybe without knowing, talking about. After giving the floor to some string theorists, I put forward my own thesis on string theory and music. I explore why string theory supporters say that the music of their theory is as beautiful as a Bach concerto. It is crucial to know this beforehand. Because, string theorists do not make reference to just any sort of music. Not to the notes of a lyre, the instrument of Apollo, god of order and harmony, nor to the chants performed in the magnificent European Gothic cathedrals of the High and Late Middle Ages; but exclusively to Classical and Romantic concertos.
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