14 May 2011

THEORY vs. EXPERIMENT - Philosophy and the Importance of Falsifiability

Sometimes, the "questions" coming in to Ask-a-Geologist are not questions, but someone upset about something and spouting their theories... some less half-baked than others.  We generally try to respond in a considerate manner, but at the same time we feel as scientists that it is important to set the record straight.

Today I received an AaG "question" where the person spouted his theories about the Earth's magnetic field for several paragraphs, and then made an important point that I felt I should reinforce.  This was his final point: "if we can do experiments, we can prove which theories are right and which are wrong." 

My Reply:
As far as I can tell, your question to Ask-a-Geologist is not a question, but instead a statement of your personal beliefs.   

As far as I know, a majority of physicists teaching in universities still at least pay lip-service to the idea that any theoretical conclusion must be verified by experiment.  A theory must lead to a hypothesis that can be tested - i.e., it must be a statement or idea that is falsifiable.  Falsifiable means that if tested, a theory is either false or it is correct - but it must be false-or-correct-TESTABLE in the first place. For a little more than a century after the great physicists Faraday and Maxwell, this was for all practical purposes a working definition of "physics."  By the middle of the last century, the rather attention-grabbing success of atomic bomb development by physicists led to a golden age in physics, with branches expanding out into plasma physics, solid-state physics (where I come from), cryophysics, biophysics, geophysics, optics, and other experimental sub-specialties of physics. 

However, for at least 30 years now, a whole generation of theoretical physicists (who now dominate most large university physics departments, and thus control the hiring of younger new faculty) have been attempting to reconcile General Relativity with Quantum Mechanics and the particle physics zoo's Standard Model - by invoking String Theory.  This theory comes in as many flavors as there are physicists, but these flavors of the theory all postulate as a common denominator the existence of undetectably tiny strings - and totally untestable extra dimensions.  In an attempt to explain what is generally referred to as the (observed but poorly named) Anthropic Principle, they appeal to belief in a totally unverifiable "multiverse": an infinite number of parallel universes, of which we belong to the one populated universe by a sort of Darwinian natural selection.  While mathematically elegant, none of these theories are even remotely grounded in testable reality.  Not only is there no experimental proof of any of this, but the theoretical physicists (if pressed) will admit that these theoretical approaches are unfalsiable.  In other words, they are no longer "doing physics", but instead are indulging in mathematical philosophy. 

This is the reason why I left physics as a profession after a Masters Degree and continued my education in geophysics instead.  If you are interested in pursuing this theory-vs-experiment issue, I would encourage you to read Peter Woit's book "Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law", and/or Lee Smolin's book "The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next". 

I hope this gives you some peace of mind. 

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