Saturday, June 7, 2014

My 25-year Love Affair with Physics, Part I: Falling in Love

Even though physics leads to good career opportunities, I would not advise anyone to study physics for that reason alone.  You have to love the subject! Let me tell you about the beauty of physics as seen in the eyes of this smitten beholder.  I'll begin with the initial seduction.

My senior year of high school I read John Gribbin's book, "In Search of Schrodinger's Cat." The attempt to understand atoms and their interactions with light in the early 20th century led to some startling conclusions.  The (now) standard understanding of many phenomena relies on the notion of superposition of states, the idea that subatomic particles can simultaneously be in two or more distinct states at the same time.  What this means is a matter of some controversy.  Why does it work? Is this just a calculational tool? What is the correspondence with reality?  

Schrodinger introduced his famous cat to show that taking these superpositions literally led to absurd outcomes.  It's one thing to think of a radioactive nucleus being in a superposition of decayed and not decayed.  It's quite another to think of a cat as simultaneously alive and dead.  But for many physicists, what first appears as a ridiculous notion, that cat's can be both alive and dead, is actually the most conservative interpretation of the empirical successes of quantum mechanics. 

What a fascinating field of study! I did not understand the subject at all, really, but I was hooked.  I was infatuated with physics.

My first year of college was almost the end of this love affair.  My physics class was nowhere near as interesting as many of my other classes that were exposing me to interesting new ideas.  But all that changed in my second year when I studied electrodynamics and relativity.  It was the relativity in particular that made my heart beat faster once again.  

I had not appreciated relativity from reading popular accounts of it in high school.  It always seemed like it was just the perceptions of phenomena that were odd, but that relativity was not really saying anything interesting about reality.  But I was wrong.  Take for example the phenomenon of time dilation.  If you are moving relative to me, it will appear to me that your clock is running slowly compared to mine.  You will claim that my clock is running slowly compared to yours.  This seems to be just a matter of appearances.  It is not. With my 2nd year course I had the tools to calculate, using Einstein's theory, what would happen if I were to accelerate away from the campus of the University of Virginia, achieve speeds approaching the speed of light, and then turn around and return. This is what happens: 

Any functioning time piece I carried with me would show less time elapsed than would be the case for those who just stayed put on campus.  This is clearly not a matter of appearances.  Relativity theory says something deep and counterintuitive about the structure of space and time.  

I was also impressed by the power of careful and clear reasoning.  Such thinking is capable of revealing highly counterintuitive and beautiful truths.  My love was deepening.  I decided I would major in physics.  I was not ready to propose marriage, but I had something good going with my college girlfriend.

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