Physics and the Limits of Reductionism

I was recently discussing the difference between chemistry and physics with my 17-year old son, who is thinking about what he wants to study in college.  I said at the time that chemistry studies how protons and electrons behave in atoms, and physics studies what protons and electrons are.  However, soon afterward, I realized that this was wrong.  While this may be an aspiration of physics, it's not true in any practical sense today.  You can take every physics course on earth and nobody will tell you what an electron is, because nobody knows.  The descriptions of reality that physics provides are operational descriptions, meaning they describe how entities operate, or behave, in certain situations.  These descriptions have proven incredibly useful, as demonstrated by our incredible technology, which was designed using these operational understandings.  However, they remain unsatisfying if what you really want are what I'll call existential descriptions, meaning what things really are.  This realization has helped me understand that the reason I study physics is for existential explanations.  I want to know what the heck all this stuff is.

Science typically makes progress through reductionism.  This principle seeks understanding of a complex entity by breaking it down into its constituent parts.  Usually, these parts are simpler than the whole, and once we understand the parts, the behavior of the whole becomes more comprehensible.  The bottom of the reductionist ladder in physics today is called The Standard Model of Particle Physics, which is more or less synonymous with "quantum physics".  Quantum physics is all operational descriptions, for example that things called electrons behave like waves in this experiment and like particles in that experiment.  There may be a layer underneath particle physics that we can't detect today.  String Theory aspires to be this next layer, describing all the particles of the Standard Model as different vibrations of Plank-scale entities called strings.  If string theory is true (which I have strong doubts about, due to Lee Smolin's book The Trouble with Physics), we may be able to eventually detect these strings and come up with satisfying existential descriptions of what they are.

The universe is, of course, not obligated to be comprehensible to our brains, which evolved to understand the behavior of macroscopic objects on earth.  It's also possible that no intuitive existential description of the universe exists.  However, I don't believe this is the case, and at this point I certainly see no reason to stop looking for one.  However, it is concerning that string theory has so many flaws, and that quantum physics produces so many incomprehensible and seemingly contradictory results, such as wave/particle duality.  I think it's possible that this confusion results from the fact that reductionism has reached the limits of its usefulness in physics.

Let me illustrate this idea by using biology as an analogy.  The successes of biology have mostly resulted from the reductionism that explains organisms in terms of their parts, in layers from systems, through organs, tissues, cells, organelles, down to the genetic code which orchestrates it all.  But then why haven't we cured all disease since we've already cracked the genetic code?  There are many reasons for this, but one major factor is that thinking of genetics as the "bottom layer" that explains everything is not accurate.  Just because a gene exists doesn't mean it's expressed (used to create proteins).  Whether or not a gene is expressed turns out to depend on many epigenetic (outside the genome) factors, including food, environmental chemicals (often produced by other organisms) and radiation.  For humans, the epigenetic factors include the symbolic input we receive from our culture, which influences our nervous system, which in turn strongly influences every other bodily system.  It's often most accurate and useful to think of the cumulative influence of the whole planet as decisive in determining which genes get expressed.  From this viewpoint, biology begins to look like a giant game of rock-paper-scissors, where no phenomena can be fully understood unless you look simultaneously at all the layers and their interactions.

I think the same pattern may be in play with physics.  Maybe quantum physics is so inexplicable because we are not considering the other layers, which are "above" it in the reductionist model.  There is certainly ample evidence that every particle in the universe affects every other particle.  Electromagnetic and gravitational fields (whatever they are) are infinite in extent, so that every part of the universe is causally connected to every other part.  These cause and effect relationships all travel at the speed of light.  Why?  How can physically separated entities be causally connected?  Maybe there are no more layers, but when all of the layers and their interactions are understood simultaneously, it will form an intuitively satisfying existential description of reality.  This would require combining quantum physics with relativity, which is the description of space, time, and matter as an evolving whole.  However, relativity is currently a classical (non-quantum) theory, where things are continuous, not quantized.  The combination of relativity and quantum physics (sometimes called quantum gravity) is a dynamic frontier of the field, with many ideas but no clear winners as yet.

Quantum effects are even more weird than, say, electromagnetic effects, because there appears to be instantaneous causal interaction in phenomena like entanglement.  This instantaneous effect is baffling to so many people because it paradoxically violates the "cosmic speed limit" of the speed of light as described in relativity theory.  However, if you stop thinking about two entangled particles as separate objects, then perhaps the phenomena can make more sense.  If what we perceive as separate objects are just two aspects of a single underlying characteristic of the universe, then perhaps there is no paradox at all.

I have read a couple of books which talk about the wholeness of the universe being important in trying to understand quantum phenomena.  Well, I've started reading them anyway.  One is called The End of Time by Julian Barbour, which makes the audacious claim that time does not exist.  It's really fascinating, but I'm wondering if I should study relativity theory first, and I also made a bad choice in purchasing the Kindle version of this book.  It has diagrams that are hard to see on my phone (my Kindle reader) and it requires frequently flipping back to earlier diagrams, which is hard in an e-reader.  At least that's my excuse for not finishing it quicker.

The other fascinating book I'm stuck on is David Bohm's The Undivided Universe.  Bohm was a brilliant but controversial physicist who never accepted the Copenhagen interpretation of quantum physics.  The Copenhagen interpretation is what gives us notions like that a particle does not exist in any particular state until we observe it.  This interpretation is treated like fact by many physics-minded people, but it's far from universally accepted, and the mathematics just doesn't say that definitively.  People are constantly describing Schrodinger's Cat, a thought experiment which "shows" that a cat can be both dead and alive at the same time.  What people don't understand is that the thought experiment was devised by Erwin Schrodinger, one of the founders of quantum mechanics, in order to show how absurd the Copenhagen interpretation is.  However, science is a social activity, and the strong personality of Niels Bohr won out, resulting in the Copenhagen interpretation being taught as fact today.

Bohm's Undivided Universe explains his alternate interpretation of quantum physics, which states that subatomic particles always have specific properties like position whether or not we are observing them.  To make this square with the math of quantum physics, he has to assume that instantaneous non-local effects exist, which is more than most physicists are willing to accept, because it appears to violate the relativity speed limit.  However, I don't so far see anyone else offering a better explanation for things like entanglement. I got halfway through Bohm's book by simply reading the words and "browsing" the math.  It is not a book for general audiences like most of my reading is, and it's chock full of some very advanced math that I never studied in school (or that has atrophied away now).  Bohm's quantum interpretation is so interesting to me that I decided to go back and learn all the math that I would need to know to really understand his book.  I want to review the math and then take another crack at it.  Unsurprisingly, this has been a tough program to stick with.  I'm considering this a long-term project.  Not sure when I'll get to it unless I win the lottery and quit my day job, but we'll see.

It's hard for me to imagine anything more interesting than thinking about what subatomic particles actually are.  Given how bewildering most discussions of physics are today, I think we're in need of some different interpretations of the math, and of what things are.  I think I'm attracted to The Undivided Universe and The End of Time because they both try to explain the world of subatomic interactions by understanding them as configurations of the universe as a whole.