How can light be a particle and a wave? I have no freaking idea. This has perplexed scientists for generations now, but experiment after experiment have proven it is true. Somehow, the individual photons that make up light are particles sometimes and waves others, depending on how you look at them. Even weirder, sometimes photons seem to have the properties of both particles and waves at the same time.
A few years ago, I read a simple analogy that makes particle-wave duality a little easier to understand. This comes to us courtesy of Isaac Asimov’s book Atom: Journey Across the Subatomic Cosmos.
Asimov asks us how we might describe an empty ice cream cone (other than disappointing). Is it a triangle or a circle? Somehow, it appears to be both. When observed from one perspective, it’s clearly a triangle; from another, it’s obviously circular. And sometimes, if viewed under certain special circumstances, the ice cream cone appears to exhibit properties of both a triangle and a circle at the same time!
Of course, light’s dual nature is far more complicated than that of an ice cream cone. Our limited, human minds may never learn how to visualize photons doing their quantum voodoo particle-wave thing, but the ice cream analogy might make this bizarre concept a little easier to digest.
P.S.: A few years ago, I wrote a review of Atom: Journey Across the Subatomic Cosmos. If you have any interest in learning about science, this book is a must read. I cannot emphasize enough that it is the best book on science I have ever encountered.