Wednesday, September 8, 2010

Week 30: Wave-Particle Duality (1/2)

Wave-Particle Duality
How Thompson's electron shattered Newton's apple, and why we shouldn't try to pick up the pieces. What modern physics can tell us about the meaning of life. 

I just watched this clip from AC360 about a burgeoning new "religion" called Universism. Universism is about learning to accept the uncertainty that governs our universe. They are anti-faith, where the Universist definition of faith is "letting other people think for you."

At a typical meeting, they sit around and discuss everything from politics to life to love. There is no preacher, pastor, pope, imam or cleric to tell them: this is how you live your life, this is what you believe and this is how you love. Instead they share and listen and learn about what life can be like and how great love can be. 

They look closer and what they see is not a single orbital path but a fuzzy cloud of possibilities.
At the end, Tom Foreman, a hint of derision in his voice (because he is an asshole), describes the practitioners as—"a diverse group of disaffected souls, heading out into the world with the gospel of uncertainty." 

But is this so bad?
Consider that it was a new “gospel of uncertainty” that transformed the study of physics in the 20th century. The transition from classical to modern physics challenged all notions of an absolute order in the universe, demanding that we embrace a “gospel of uncertainty” in exchange for deeper insights into the nature of nature.
Classical mechanics, first expounded by Sir Isaac Newton in the 17th century, is the mathematical framework through which humanity caught its first glimpses of a rational order underlying what was previously a chaotic, capricious universe. 
Where you are, where you have been, where you are going, how you will get there: such questions were the bread and butter of classical mechanics, and Newton’s framework allowed for these questions to be answered with absolute certainty.
Classical mechanics was an adequate tool for probing Newton’s human-scale universe. But a macroscopic apple falling from a tree is very different from an infinitesimal electron zipping through a cathode ray tube, and as humanity began pushing beyond the limits of our five senses, Newton’s world—and the classical understanding of physics that it was based on—began to break down.  

The cracks really began to show at the turn of the 20th century. Up until then, electricity was understood classically as a wave-like phenomenon—described as a kind of fluid through which energy flowed. 

But in 1897, J.J. Thompson conducted an experiment that proved otherwise. His conclusion: electricity could only be described as a particle with negative charge moving through space—an electron. 
The classical view held that everything in the universe was either a particle or a wave; matter or energy—but never both. The descriptions were mutually exclusive: matter couldn’t be energy, and energy couldn't be matter (kind of like how men can’t be women, and women can’t be men).
And yet here was evidence to the contrary: Electricity was both a wave, and a particle! Both descriptions of electricity were accurate, and both provided wonderful new insights into the phenomenon, but they both couldn’t be right, could they? 
The nature of light soon came under new scrutiny, and when physicists looked more closely, they noticed the same thing! Depending on how you observed/measured it, light could be described as either a wave, or a particle!
The “reality” of light seemed to change depending on how physicists chose to “perceive” it!
But how could that be? How could there be more than one reality? 

Tune in next week! 

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