piet_hut's picture
professor of astrophysics at the Institute for Advanced Study, in Princeton
There Are No Things.

That's right. No thing exists, there are only actions. We live in a world of verbs, and nouns are only shorthand for those verbs whose actions are sufficiently stationary to show some thing-like behavior. These statements may seem like philosophy or poetry, but in fact they are an accurate description of the material world, when we take into account the quantum nature of reality.

Future historians will be puzzled by the fact that this interpretation has not been generally accepted, 75 years after the discovery of quantum mechanics. Most physics text books still describe the quantum world in largely classical terms. Consequently anything quantum seems riddled with paradoxes and weird behavior. One generally talks about the "state" of a particle, such as an electron, as if it really had an independent thing-like existence, as in classical mechanics. For example, the term `state vector' is used, even though its operational properties belie almost anything we normally associate with a state.

Two voices have recently stressed this verb-like character of reality, those of David Finkelstein, in his book Quantum Relativity, and of David Mermin, in his article "What is quantum mechanics trying to tell us" [1998, Amer. J. of Phys. 66, 753]. In the words of the second David: `"Correlations have physical reality; that which they correlate does not.'" In other words, matter acts, but there are no actors behind the actions; the verbs are verbing all by themselves without a need to introduce nouns. Actions act upon other actions. The ontology of the world thus becomes remarkably simple, with no duality between the existence of a thing and its properties: properties are all there is. Indeed: there are no things.

Two hundred years ago, William Blake scolded the physicists for their cold and limited view of the world, in terms of a clockwork mechanism, in which there was no room for spontaneity and wonder. Fortunately, physicists did not listen to the poet, and pushed on with their program. But to their own utter surprise, they realized with the discovery of quantum mechanics that nature exhibits a deeply fundamental form of spontaneity, undreamt of in classical physics. An understanding of matter as dissolving into a play of interactions, partly spontaneous, would certainly have pleased Blake.

What will be next? While physics may still seem to lack a fundamental way of touching upon meaning and wonder, who is to say that those will remain forever outside the domain of physics? We simply do not know and cannot know what physics will look like, a mere few hundred years from now.

There is an analogy with computer languages. Physicists have a traditional aversion to learning any other language than Fortran, with which they grow up, no matter how useful the other languages may be. But without ever parting from their beloved Fortran, it was Fortran that changed out from under them, incorporating many of the features that the other languages had pioneered. So, when asked how future physicists will program, a good answer is: we have not the foggiest idea, but whatever it is, it will still be called Fortran.

Similarly, our understanding of the material world, including the very notion of what matter and existence is, is likely to keep changing radically over the next few hundred years. In what direction, we have no idea. The only thing we can safely predict is that the study of those wonderful new aspects of reality will still be called physics.