The Trouble with Physics and Realism

                                                                        Lee Smolin, The Trouble with Physics

             In The Trouble with Physics, Lee Smolin presents a powerful critique of the state of modern physics.   http://www.thetroublewithphysics.com/  The cause of the “trouble with physics” is that the two leading theories of physics— quantum theory and the general theory of relativity (i.e., gravity) — are mutually incompatible.  The standard explanation for this incompatibility is that quantum physics, with its wave-particle duality and uncertainty principle, governs the world of the very small, while gravity, which by definition is proportional to mass, governs the very big.  See Vlatko Vedral, Living in a Quantum World, Scientific American  (June 2011).

            But there is only one world, combining the big with the small.  Where does one draw the line?  It seems self-evident that any final theory must explain the world on any scale; the theory must explain both tiny particles and the Milky Way; the quark and the sun.  

            In the world of modern physics, the leading candidate to unite quantum theory and gravity is string theory.  This theory holds that at the base of reality are not tiny particles but quivering strings, vibrating in ways that mimic the mass and movement of particles.  See Brian Greene, The Elegant Universe for a complete discussion of string theory.

            String theory may seem like an esoteric topic except, as Professor Smolin shows, it also dominates the physics departments of the nation’s leading universities and research institutions.  But string theory is riddled with serious problems of its own: its 11 dimensions (that’s 7 more than the 4 we know exist, the three spatial dimensions and time), makes no predictions that are testable and is not even a single theory.  As Professor Smolin explains,  

Much effort has been put into string theory in the last twenty years, but we still do not know whether it is true. Even after all this work, the theory makes no new predictions that are testable by current—or even currently conceivable—experiments. The few clean predictions it does make have already been made by other well-accepted theories.  .  .  Thus, no matter what the experiments show, string theory cannot be disproved. But the reverse also holds: No experiment will ever be able to prove it true.

          He goes on to say that

What we have, in fact, is not a theory at all but a large collection of approximate calculations, together with a web of conjectures that, if true, point to the existence of a theory. But that theory has never actually been written down. We don’t know what its fundamental principles are. We don’t know what mathematical language it should be expressed in—perhaps a new one will have to be invented to describe it. Lacking both fundamental principles and the mathematical formulation, we cannot say that we even know what string theory asserts.

(Kindle, Loc. 167-69; 181-84). Professor Smolin quotes the remarks Nobel Laureate, David Gross, gave in a string theory conference: “We don’t know what we are talking about…. The state of physics today is like it was when we were mystified by radioactivity…. They were missing something absolutely fundamental. We are missing perhaps something as profound as they were back then.”  (Kindle, Loc. 194-98).

            And the problem is broader than that.  As Smolin writes,

It is not an exaggeration to say that hundreds of careers and hundreds of millions of dollars have been spent in the last thirty years in the search for signs of grand unification, supersymmetry, and higher dimensions. Despite these efforts, no evidence for any of these hypotheses has turned up. A confirmation of any of these ideas, even if it could not be taken as a direct confirmation of string theory, would be the first indication that at least some part of the package deal that string theory requires has taken us closer to, rather than further from, reality.

(Kindle, Loc. 3243-47). 

            So why is the modern science community so enthralled with string theory?  Well, the answer, as Smolin also skillfully discusses, may be sociological: the string theory freight train is far down the track and anyone who doesn’t jump onboard is thrown aside; no professorships, no grants, no recognition by peers.  Recognizing the powerful conditioning influence of the physics community, Smolin stresses the need for new ideas, a “seer” who can branch off in a different direction and help develop a new approach to explaining the physical world, one perhaps that won’t require 11 dimensions or come in 10⁵⁰⁰ varieties.   

            And here we come to the root cause of the problem.  Specifically, modern science is wedded to the notion that any physical theory must “give an account of reality as it would be in our absence.” (Loc. 409-10).  He calls this perspective “realism,” the idea that the “real world out there must exist independently of us.” (Loc. 407).  He ponders the thought that realism as a philosophy might simply die, but deems this event unlikely.  Belief in a real world out there, he says,  and the “the possibility of truly knowing  it motivates us to do the hard work needed to become a scientist and contribute to the understanding of nature.”  (Loc. 456-60). 

            But here is the question that must be asked:  what if this real world out there — the one independent of us — does not in fact exist?  Suppose this notion of a mind-independent world is simply a model, a mental construct laid over experience to help frame it for further study?  Suppose in seeking to work within a “realist framework” scientists have ironically chosen an imaginary world? 

             At this point we must focus in a bit and address the question of what the “us” is in the phrase, independent of “us.”  To some, the answer to this question is that we are fundamentally a collection of mind-independent particles; to others, we are fundamentally a mind. 

             If we are ultimately made out of things, then of course the natural world and our bodies would be independent of our minds, or brains.  To conceptualize this standpoint requires no conceptualization: the natural world appears to exist independently of ourselves —like a grand stage on which we are the actors— and therefore we think it does.

             But if we are fundamentally a mind, then both our bodies and the natural world would be projections of the mind; dream-images existing on the same level and therefore real to each other.

             Rene Descartes, during his famous meditations in the 17^th century, concluded that  he had greater certainty over his own mind than over the independent existence of the external world.  The natural world, he reasoned, might very well be a dream created by the mind.  He then reasoned, however, that because God would not make him believe a world exist outside the mind unless one really did, he convinced himself the world was not a dream.  But Descartes, despite his use of God to restore the real world, nonetheless showed that we possess greater certainty over our own minds than over the independent existence of the physical world.  Put differently, what if Descartes had not appealed to God to cure his doubts about the independent existence of the external world?          

            And now we come to the big question: Is one standpoint more “real” than the other?  Is the imagined theoretical world of today’s scientific realist more “real” than the truly imagined world of the dreamer?  If we insist on defining “reality” before we know what realities are possible, then perhaps one can reach the conclusion that the world of science is more real.  But if we define reality in terms of possible worlds, then we may have no choice but to accept the fact that only dream worlds are possible and that the world we have is as real as worlds get.  

            So the trouble with physics may be that scientists have not yet thought long or hard enough about whether it is their conceptualization of “realism” that is holding them back from reaching a theory of everything. Perhaps it is possible to be both a “dream-realist” and a scientist, but science will never know unless it attempts to re-cast its theories within a different conception of “realism.” And last, scientists may have no choice: if the world is really a dream, then they must either adapt to that reality or someday find that their theories no longer align with the real world.