"Are we particles," Amy wants to know, "or waves?"
.... John Barth, On With the Story

Among the most significant intellectual advances of the twentieth century is "quantum mechanics", a view of the material world unlike any that has existed at any prior time in human history. Quantum mechanics is both sweeping in its implications and sufficiently novel and counter-intuitive so that even those most actively involved in its advancement remain today uncertain about exactly how its essence is best described. We are provide a set of experiences aimed at giving you some sense of what it involved in quantum mechanics, so that you too can perhaps particpate in the ongoing thinking through of how best to think and talk in these new terms, and what their implications are.

Most people comfortably and intuitively deal with and talk about objects, and "particles" are no more and no less than idealizations or abstractions of the "objects". They have postions, velocities, bang into and rebound from one another in ways that few would find surprising. "Waves" are, for many people, probably a little harder to make sense of, but one of course knows them, and a lot about their properties from ocean beaches and ripples on a pond. So particles, on the one hand, and waves, on the other, yield a picture of the material world with which most people are comfortable. And, if you've heard anything of quantum mechanics, it has probably been something like "things are really neither particles nor waves but rather both at the same time".

"Particle/wave duality" Is certainly e way to characterize what is counter-intuitive in quantum mechanics. Whether it actually makes quantum phenomena easier to understand, as opposed to being simply a mantra one remembers, is something you can decide for yourself. Richard Feynman, a Nobel Prize physicist, thought there must be a better way to describe quantum behavior than to throw up one hands and simply say "things sometimes act like a wave and somtimes act like a particle". In this exhibit, you can work through Feynman's alternative way of thinking about quantum behavior (one which makes life much simpler for material objects themselves) which he summarized as

Explore All Paths!

In addition to providing you the tools to try and develop your intuitive understanding of quantum behavior along the "explore all paths line", this exhibit will introduce you as well to some other central concepts of quantum mechanics. One is the idea that objects aren't actually ever at a particular place but rather exist as distributions of probabilities of being at a number of different places. And a related idea is that associating these probabilities, as one would have to do, for example, to predict the results of interactions of objects, requires a new concept, that of "phase". Its certainly a different way of thinking about the material world than most people are used to. Why does it exist? Is it an improvement? What better understandings does it yield of things we thought we understood? What new questions does it raise? Join us and others in thiking about these questions, and leave your thoughts in the Forum Area.