“I want to tell you about one of the most beautiful ideas that I know.

It’s a physics experiment, and it’s beautiful because in one elegant stroke, it expands our consciousness, forcing us to realize that objects can behave in ways that are impossible for us to picture (but remarkably, possible for us to calculate). It’s beautiful because it calls into question the bedrock of logic on which we’ve built our understanding of the world. It’s beautiful because it’s deceivingly simple to understand, and yet its consequences are deeply unsettling. And it’s beautiful because I refused to accept it until I ran the experiment for myself, and I distinctly remember watching my worldview shatter as the picture slowly built up on the computer monitor.”

So begins Aatish Bhatia’s eloquent blog post about the existential challenges posed by close observations of the humble electron. You may have some sense of its supposed duality: sometimes it’s like a particle, other times it’s like a wave. Right? You may recall how the so-called “double-slit experiment” opened our eyes to its wave-like behavior.


Animation of the double-slit experiment, showing how wave interference patterns lead to the observed pattern of fringes on the screen. (Wikipedia: Lookang, License CC BY-SA)

But calling an electron a “particle” or a “wave” is just an analogy, and a reflection of limits in our popular language. Electrons are not particles. They are not waves. They are not simultaneously both particles and waves; nor are they neither of these. So much for conventional logic.

Physicists have devised the mathematical language of quantum mechanics to fill the void in vocabulary, and given the name superposition to this fundamental state of being.

A rousing introduction to superposition is how Prof. Allan Adams kicks off his new OCW course 8.04 Quantum Physics I.  Aatish credits Prof. Adams’ videos as the primary inspiration of his post, adding, “The first lecture is an fascinating and often hilarious look at the principle of superposition explained in a non-technical way. I highly recommend checking it out – he’s a very engaging lecturer.”

We couldn’t agree more. Spend an hour with Prof. Adams’ introductory lecture, and your world will never be the same.