Thursday, April 3, 2014

In an age with a record number of sicentists, could we be missing new phyiscs?

In the late 1800s and early 1900s, classical theories of physics began to crumble in light of new evidence accumulated by experiments on the quantum scale.  The new explanations proposed at the time irked some of the biggest names in physics, mathematics, and philosophy.

For example, Poincare's philosophy of science was based on what philosophers call instrumentalism, which dismisses unobservable entities.  (see for example the paper by Milena Ivanova)  This viewpoint is dismissive of the reality of atoms because they are not directly observed.  Even when the evidence mounted, Milena Ivanova argues that, "...PoincarĂ©’s paper motivates a non-fundamentalist view about the world, and that this is compatible with his structuralism. ... PoincarĂ© advanced structural realism, which commits one to the structural claims of scientific theories and not the claims regarding unobservable entities."  In other words, the theory describes what is observed in terms of a mathematical structure, but the observation does not imply, for example, that atoms - an assumption underpinning the theory - exist.

The early 1900s must have been an exciting time of discovery.  Scientists had to shed their preconceived notion about certainty and absolute space.  I wonder if I would have been a staunch supporter of the status quo or if I would have accepted the new way of thinking.  We'll never know, though I'm sure many of us would fancy ourselves falling on the right side of history.

Quantum mechanics became accepted as the theory of atoms and molecules because of its success in predicting atomic spectra and differential scattering cross-sections. As such, the underlying structure of atoms and molecules as suggested by the theory have become accepted as reality.  Our classical view and intuition about the world falls apart at the quantum scale.  Electrons are not tiny point-like particles whose position and momenta can be simultaneously determined to arbitrary precision.

The rates of thermodynamic processes are typically accelerated when the temperature is increased, but we find a dramatic decrease in the rates of self healing when we turn up the heat.  Many such strange things characterize the underlying process.

In the modern era, physicists picture a single electron in an atom as a fuzzy cloud rather than the old planetary picture of one tiny particle orbiting a nucleus.  An electron can pass simultaneously through two slits in a wall and two particles can be entangled so that measuring the spin of one particle instantaneously determines the spin of another one on the other side of the universe.  Observations like these are so commonplace that we accept them without question.

We have warmed to the reality of something very bizarre because all measurements support this view.  Is it really that way?  I would respond, yes, because reality is probed by observation, even if by indirect means.  Because of the theory's great success, it is assumed to work for highly complex systems even when it is impossible to test the theory because of our computational limitations and inaccurate experiments.

In my field of nonlinear optics, we measure the nonlinear susceptibilities of molecules and compare them with theory.  However, the measurements have large experimental uncertainties and the calculations use approximation techniques that render the calculations imprecise.  It would be wonderful if experiments and calculations could reliably reach 10% uncertainties.  In many cases, it's more like 25-50% uncertainty. Contrast this with the test of quantum electrodynamics in which theory and experiments agree to 12 decimal places.  That is an amazing theory!

One of our projects seeks to understand the self-healing process and our experiments suggest that strange things are at work.  When a material is burned with light, it does not recover just like ashes don't recombine into a log from which they came.  We have been observing self-healing of molecules after being burned with highly intense light.  Though this may seem weird to most physicists, it is commonplace in our lab, where we have been observing the phenomena for over a decade.  The rates of thermodynamic processes are typically accelerated when the temperature is increased, but we find a dramatic decrease in the rates of self healing when we turn up the heat.  Many such strange things characterize the underlying process.

As described in a previous post, we postulated that molecules in the company of others heal more quickly.  We call these groupings domains.  At elevated temperatures, thermal jiggling breaks up the domains and therefore self healing is suppressed.  Do domains really exist?  We haven't seen a domain but every measurement is consistent with the predictions of the theory.   In other words, the mathematical structure corresponds to the reality of what we are measuring.  At what point can we say that domains actually exist in our samples?

It takes lots of evidence for a theory to be accepted as the true description of a phenomena, and the picture that it suggests starts to become accepted slowly as the theory predicts other phenomena that were not intentionally added to the theory when it was originally formulated.  For example, the famous Dirac Equation accurately predicts all of the relativistic corrections to the hydrogen atom, and naturally includes spin, which in the Schrodinger theory needs to be separately added -- an inelegant solution.

Dirac's theory of the electron worked flawlessly, but also had a major defect; it had negative energy solutions that were not observed.  Dirac perseverated over this flaw and tried many approaches to sweep the problem under the proverbial rug.  The negative energy solutions were later shown to be those of the positron, the anti-particle to the electron.  The Dirac equation in effect predicted the existence of antimatter.  Dirac quipped that his equation was smarter than him.

While to the best of our knowledge, the domain theory of self healing has not been making any new predictions, we have been testing it in new ways.  One of my students (Ben) wrote a dissertation that focused on measurements of self healing under the influence of an electric field.  An electric field induces an electric dipole moment in a molecule.  The molecules in a domain will then interact with each other through the electric fields generated by the induced dipole moments.  It is straightforward to calculate the energy of interaction, and thus determine if a domain grows or gets torn apart by the electric field.

Ben's calculations of the effect of the electric field on the distribution of domains in a sample, and thus it's healing properties, agrees well with his experiments.  As the evidence accumulates, the domain model is not only holding up well, but predicts with reasonable precision what we observe.

The problem is that we have not actually "seen" a domain.  It may be possible to do scattering experiments in which particles such as neutrons probe the microscopic structure of a domain.  We have also been trying to come up with an explanation of the nature of a domain and how it is held together.  My preferred picture is that a domain is made of molecules that are attached to a polymer chain (the domain model suggests wispy string-like domains and not clumps) rather than a string of molecules connected to each other.  Our model allows us to determine the binding energy of a molecule to a domain, and experiments show it to be in the ballpark of hydrogen binding energies between molecule and polymer.

There is even a more intriguing possibility.  This system may be exhibiting a phenomena that arises from the complexity of the system, and cannot be reduced to a description in terms of simpler units.  Perhaps the picture of bonds and molecules starts falling apart when many large molecules interact with each other and with long polymer chains.  The bond, which chemists hold sacred, is not as sacred as the Schrodinger equation, but rather a convenient form of book keeping that helps chemists understand what molecules are formed in reactions between smaller units.

Chances are that the explanation of the phenomena is more mundane than we propose.  At worst case, we may be deluding ourselves into seeing something that is not there.  We won't know until we do lots more work and other researchers test our models with new experiments.

too much research these days is focused on narrow topics, so new and interesting work might be missed simply because it falls outside the mainstream.

Our group enjoys the luxury of having a huge lead in this area of research. We may be sitting on a very interesting discovery.   Though my talented grad students have done lots of excellent work to eliminate hypotheses, we are still puzzled by what we are observing.  We continue to whittle away the false hypotheses in our quest to uncover the truth.

This lead is a two-edged sword.  Our paper on the affect of the electric field on self-healing, which we submitted to Physical Review E and which appears on the Physics Archives, has been sent to half a dozen reviewers, all of whom have turned down the request to review.  The editors subsequently  notified us that they were going through a second wave of review requests.  Because we are so far ahead, other researchers may not understand our work.  Another unfortunate consequence of our sequential series of papers is that we reference a large number of our own papers.  This is unavoidable since we have done all of the foundational work on the topic.  But, it raises eyebrows in the community, which makes us cringe.  However, I am happy to report that our paper eventually got two reviewers who made some good suggestions that we implemented, and the paper is in print.

I believe that too much research these days is focused on narrow topics, so new and interesting work might be missed simply because it falls outside the mainstream.  Perhaps the huge success of science has lead to such a high volume of activity that researchers can only understand work in their own narrow area of specialization.  We are too busy studying the scales to see the huge serpent wriggling in our midst.  This is not to say that one research paradigm should be pursued at the exclusion of all others.

A balance needs to be struck between detailed narrow work, which can miss the big stuff, and broader investigations, which may temporarily lead us astray but eventually lead to something big.  Though the process is sloppy, science has a way of eventually sorting through the trash and finding the real gems.  Hopefully, my lifetime commitment to the process will eventually uncover something of value.  Even if I fail, I take comfort in the fact that we are all part of a highly interconnected human network, where each part contributes to the success of the whole.

We must take pleasure in the process of discovery, give it our best shot, and see where it takes us.  I am fortunate to be part of the most incredible journey, keeping me excited throughout my life.  I still suffer fitful nights, being kept awake by ideas running around my head and starting the morning with impatience for all the administrative obligations that keep me away from my true passion.  The professorial life still gives a fair amount of time and more importantly encouragement to pursue the big ideas, giving me the resolve to pursue my ideas even if in a quixotic manner.  For this I am eternally grateful.